Obesity in Anestesia and Intensive Care

8/13/2019 Obesity in Anestesia and Intensive Care

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Br it ish Jou rna l of Ana es the sia 85 (1 ): 91-108

(2000)

Obesity in anaesthesia and

intensive care

J. P. Adams and P. G. Murphy

Department of Anaesthesia, The General

Infirmary at

Leeds, Great

George treet, Leeds Ll !"#, $%

Br] Anaesth 2000; 85: 9

I -I 08


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Keywrds: complications, obesity

The prevalence of sinificant obesity contin!es to

rise in both "evelope" an" "evelopin co!ntries,an" is associate" #ith an increase" inci"ence of a#i"e spectr!m of me"ical an" s!rical patholoies$%

&Table 1'( As a res!lt, the anaesthetist can e)pect to

be presente" fre*!ently #ith obese patients in the

operatin theatre, intensive care !nit or res!scitation

room( These patients may provi"e the anaesthetist

#ith a consi"erable challene( A thoro!h !n"er-

stan"in of the pathophysioloy an" specific

complications associate" #ith the con"ition sho!l"allo# more effective an" safer treatment for this

!ni*!e ro!p of patients(

!e"initins

+besity is a con"ition of e)cessive bo"y fat( The

name is "erive" from the atin #or" o&esus, #hichmeans fattene" by eatin(9The "ifference bet#een

normality an" obesity is arbitrary, b!t an in"ivi"!al

m!st be consi"ere" obese #hen the amo!nt of fat

tiss!e is increase" to s!ch an e)tent that physical

an" mental health are affecte" an" life e)pectancy

re"!ce"(122.)amples of bo"y fat contents in a"!ltsfrom /estern societies are 20-$0 for the averae

female, 18-2% for the averae male, 10-12 for a

professional soccer player an" for a marathonr!nner(121

Acc!rate meas!rement of bo"y fat content is

"iffic!lt an" re*!ires sophisticate" techni*!es s!chas comp!te" tomoraphy &T' scannin or

manetic resonance imain( 3sef!l estimates,

ho#ever, can be obtaine" by eval!atin #eiht for a

iven heiht an" then comparin that fi!re #ith an

i"eal #eiht( The concept of i"eal bo"y #eiht

&IB/' oriinates from life ins!rance st!"ies #hich

"escribe the #eiht associate" #ith the lo#est

mortality rate for a iven heiht an" en"er; foreneral clinical p!rposes, IB/ can be estimate"

from the form!la IB/ &in 4' 5 heiht &in cm' - ),#here )is 100 for a"!lt males an" 10% for a"!lt

females(

The bo"y mass in"e) &B6I' is a more rob!st

meas!re of the relationship bet#een heiht an"

#eiht, an" is #i"ely !se" in clinical an"

epi"emioloical st!"ies( It is calc!late" as follo#s7

B6I 5 bo"y #eiht &in 4'Iheiht2&in

metres'

A B6I of 2% 4 m-2 is consi"ere" normal; a person

#ith a B6I of 2%-$0 4 m-2 is consi"ere"

over#eiht b!t at lo# ris4 of serio!s me"ical

complications, #hile those #ith a B6I of $0, $%an" %% 4 m-2 are consi"ere" obese, morbi"ly

obese an" s!per-morbi"ly obese, respectively($9

6orbi"ity an" mortality rise sharply #hen the B6I is

$0 4 m2( Altho!h it is a very rob!st an"

practical assessment of obesity, the B6I "oes have

its limitations( :or instance, heavily m!scle"

in"ivi"!als #o!l" be classifie" as over-#eiht( It is

no# tho!ht that other factors, s!ch as yo!n aean" the pattern of a"ipose tiss!e "istrib!tion, may

be better pre"ictors of health ris4(

#pidemi$%y

There is over#helmin evi"ence that the prevalence

of obesity is increasin #orl"#i"e( In 199, an

International +besity Tas4 :orce s!mmarie"

information on the epi"emioloy of obesity($%

can"inavia an" the ?etherlan"s &10' b!t #orse

for .astern .!rope &!p to %0 amon #omen in

some co!ntries'( The health an" economic

implications are consi"erable, since co!ntries s!chas :rance, @ermany an" the 3= #ill each have

appro)imately 10 million obese inhabitants($% The

sit!ation in the 3>A is even #orse, #ith the

prevalence of a B6I of 2% 4 m-2bein %9( for

men, %0( for #omen an" %(9 for a"!ltsoverall(0:!rthermore, for the perio" 190-199, the

prevalence of obesity &B6I of $0 4 m-2' hasincrease" mar4e"ly from 12(8 to 22(%(

The prevalence of obesity varies #ithsocioeconomic stat!s( In "evelope" co!ntries,

poverty is associate" #ith a reater prevalence of

obesity #hereas in "evelopin areas it is affl!ence


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that carries the hiher ris4(1


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Table 1 Medical and surgical conditions associated with obesity

Category Examples


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Obesity

Cardiovasculardisease

Respiratory diseaseEndocrine diseaseGastrointestinal

diseaseGenitourinaryMalignancyMusculoskeletal

udden !cardiac" death# obesity cardiomyopathy# hypertension# ischaemic heart disease# hyperlipidaemia#

cor pulmonary# cerebrovascular disease# peripheral vascular disease# varicose veins# deep-vein thrombosis and

pulmonary embolism Restrictive lung disease# obstructive sleep apnoea# obesity hypoventilation syndrome$iabetes mellitus# Cushing%s disease# hypothyroidism# in&ertility'iatus hernia# gallstones# inguinal herniaMenstrual abnormalities# &emale urinary incontinence# renal calculi

(reast) prostate) colorectal) cervical and endometrial cancer*steoarthritis o& weight-bearing +oints) back pain


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Obesity

Mrta$ity

There is little evi"ence to s!est that bein

mo"erately over#eiht &act!al bo"y #eiht 110-

120 of IB/' carries m!ch e)cess ris4 in yo!n

a"!lts,1$ b!t morbi"ity an" mortality rise sharply#hen B6I is $0 4 m 2) partic!larly #ithconcomitant ciarette smo4in( The ris4 of

premat!re "eath "o!bles in in"ivi"!als #ith a B6I of

$% 4 m 2( >!""en !ne)plaine" "eath is 1$times more li4ely in morbi"ly obese #omen than in

their non-obese co!nterp s $ 10 +ver#eiht menparticipatin in the :raminham st!"y82 ha" a

mortality rate $(9 times reater than the normal

#eiht ro!p( 6orbi"ly obese in"ivi"!als are at a

m!ch reater ris4 of mortality from "iabetes,

car"iorespiratory2 an" cerebrovasc!lar "isor"ers,

an" certain forms of cancer,%as #ell as a host of

other "iseases99 1,, &Table 1'( These ris4s areproportional to the "!ration of obesity;121 it appearsthat contin!e" #eiht ain constit!tes a hiher ris4

than for obese in"ivi"!als #hose #eiht is constant(:or a iven level of obesity, men are at a hiher ris4

than #omen,10 b!t for both ro!ps #eiht loss

re"!ces the ris4 associate" #ith previo!s obesity(


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Obesity

Geneti predisposition

+besity ten"s to be familial, #ith chil"ren of t#o

obese parents havin abo!t a 0 chance of

becomin obese themselves as compare" #ith a 20

ris4 for chil"ren of non-obese parents( This can, inpart, be e)plaine" by infl!ences s!ch as "iet an"

lifestyle, b!t st!"ies of a"opte" chil"ren sho#

#eiht patterns similar to those of their nat!ral

parents, s!estin that a enetic component "oese)ist( Animal st!"ies have confirme" that there is a

enetic

"thni influenes

In the 3>A there are mar4e" "ifferences in the

prevalence of obesity in the "ifferent ethnic

pop!lations, #ith African an" 6e)ican Americansbein at m!ch hiher ris4 than #hite Americans(

Asian immirants to the 3= have a more central

"istrib!tion of fat than native a!casians; this isassociate" #ith an increase" ris4 of "iabetes an"

coronary heart "isease($%


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oioeonomi fators*+

In the 3= there is an inverse relationship bet#een

socioeconomic stat!s an" the prevalence of obesity, #ith

#omen of social class I havin a 10 ris4 as compare" #ith

2% in social class C( +f #omen #ho move to a hiher

social class on marriae, only 12 #ere over#eiht as

compare" #ith 22 #ho move" to a lo#er social class(

edial disorders

.n"ocrine abnormalities s!ch as !shinDs "isease or

hypothyroi"ism pre"ispose to obesity( Eatients #ith s!ch

"iseases are !s!ally i"entifie" *!ic4ly from symptoms other

than obesity, an" appropriate me"ical therapy normally

corrects the problem( In the same #ay, certain "r!s-s!ch as

corticosteroi"s, anti"epressants an" antihistamines-may also

lea" to #eiht ain(

"nergy &alane

The total n!mber of calories cons!me" an", partic!larly, the

"ietary fat content, is the prime "eterminant of obesity &the

proportion of fat in the 3= "iet has increase" from 20 to

0 over the last %0 years'( Alcohol appears to play a 4ey

role too, an" may infl!ence the site of fat "eposition,enco!rain central fat to be lai" "o#n(

ontrary to pop!lar belief, obese people have a reater

enery e)pen"it!re than thin people as it ta4es more enery to

maintain their increase" bo"y sie( Inactivity is !s!ally theres!lt, b!t not necessarily the ca!se, of the obesity( o#ever,

it has been sho#n that in"ivi"!als #ho remain active in their

a"!lt life "o best at maintainin healthy #eiht levels(

/hile an imbalance bet#een enery inta4e an" enery

e)pen"it!re is typical of obesity, the "aily net calorie e)cessmay be *!ite mo"est( :or instance, a typical #eiht ain of20 4 over 10 years implies an initial "aily enery e)cess of

$ 0 0 4cal, the e*!ivalent of less than half a san"#ich($%

!istributin " bdy "at and hea$th ris&

It is no# becomin clear that it is not only the amo!nt of fat

that is important in "eterminin ris4, b!t also its anatomical

"istrib!tion($ ss 1$1 In the central or an"roi" type of

"istrib!tion, #hich is more common in males, fat ispre"ominantly "istrib!te" in the !pper bo"y an" may be

associate" #ith increase" "eposits of intra-ab"ominal or

visceral fat( In the peripheral or ynaecoi" type, fat is more

typically "istrib!te" aro!n" the hips, b!ttoc4s or thihs; this is

the more !s!al female pattern of "istrib!tion(20 entral

a"ipose tiss!e is metabolically more active than fat in the

peripheral "istrib!tion an" is associate" #ith more metabolic

complications s!ch as "yslipi"aemias, l!cose intolerancean" "iabetes mellit!s, an" a hiher inci"ence of mortality

from ischaemic heart "isease(22 0 1$1 6orbi"ly obese

patients #ith a hih proportion of visceral fat are also

at a reater ris4 from car"iovasc!lar "isease, left ventric!lar

"ysf!nction an" stro4e(1$The mechanism for this increase"

ris4 #ith intra-ab"ominal fat is not 4no#n, b!t one #i"elyhel" theory implicates the pro"!cts of the brea4"o#n of

visceral fat bein "elivere" "irectly into the portal circ!la-

tion an" thereby in"!cin a sinificant secon"ary metabolic

imbalance(121 Altho!h the practical assessment of fat

"istrib!tion re*!ires sophisticate" imain techni*!es, the

ratio of #aist to hip circ!mference is a !sef!l clinicalmeas!re( In .!ropean "escen"ants a #aist7hip ratio of 1(0

in men an" 0(8% in #omen #o!l" ten" to s!est a hiher

proportion of more centrally "istrib!te" fat($

Obesity and the respiratry system

-&struti.e sleep apnoea

Appro)imately % of morbi"ly obese patients #ill have

obstr!ctive sleep apnoea +>A, #hich is characterie" by the

follo#in feat!res71F 9% 121 19

&i' :re*!ent episo"es of apnoea or hypopnoea "!rinsleep(11An obstr!ctive apnoeic episo"e is "efine" as 10s or more of total cessation of airflo# "espite

contin!o!s respiratory effort aainst a close" air#ay(ypopnoea is "efine" as %0 re"!ction in airflo# or a

re"!ction s!fficient to lea" to a "ecrease in arterial

o)yen sat!ration(1121The n!mber of episo"es tho!ht

to be clinically sinificant is often *!ote" as five or

more per ho!r or $0 per niht( The e)act n!mbers are

rather arbitrary an" it is obvio!sly the clinical se*!elae,

s!ch as hypo)ia, hypercapnia, systemic an" p!lmonary

hypertension an" car"iac arrhythmias, that are moreimportant(

&ii' >norin( This !s!ally ets lo!"er as the air#ayobstr!cts, follo#e" by silence, as airflo# ceases, an"

then aspin or cho4in, as the person ro!ses an"

air#ay patency is restore"(

&iii'


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Obesity

m!scle tone is lost "!rin sleep an", in many in"ivi"!als,this lea"s to sinificant narro#in of the air#ay, ca!sin

t!rb!lent airflo# an" snorin(1Increase" inspiratory effortan" the response to hypo)ia an" hypercapnia lea" to aro!sal

#hich, in t!rn, restores !pper air#ay tone(%1 101 The patient

then asps, ta4es a fe# breaths an" falls asleep aain; the

cycle then restarts( Total occl!sion can occ!r if the air#ay is

narro#e" f!rther, s!ch as by enlare" pharyneal soft tiss!es

or by a f!rther re"!ction in m!scle tone by "r!s or

alcohol(120

is1 fators

The main pre"isposin factors are male en"er, mi""le ae

an" obesity, #ith other factors s!ch as evenin alcohol or

niht se"ation compo!n"in the problem(fi1 +ther feat!res

that help to i"entify sinificant +>A are a B6I of $0 4

m-2) hypertension, observe" episo"es of apnoea "!rinsleep, collar sie 1(%, polycythaemia, hypo)aemiaH

hypercapnia an" riht ventric!lar hypertrophy or impairment

on electrocar"ioraphy an" echocar"ioraphy(121


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Table 2 erioperative changes in o0ygenation) and the in&luence o& EE in patients undergoing bariatnc surgery !&romre&erence 134". 56 7 intermittent positive pressure ventilation) EE 7 positive end e0piratory pressure) Doe 7 o0ygendelivery) KT 7 cardiac output) QS/QT7 stunt &raction) !8-a"a9 7 alveolar arterial o0ygen di&&erence

Pao:(kPa)

Paco(kPa)

P(A - a"o)(kPa)

KT !litres min -1" QSIQT !;"$o) !mlmin-1"

reoperative)1,.4


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perative chanes in o)yenation in patients

!n"eroin bariatric s!rery134&Table 2'( A mo"est

"efect in as e)chane an" increase" sh!nt fraction

preoperatively "eteriorate "ramatically follo#in

in"!ction of anaesthesia an" inc!bation( The a""itionof E..E improves o)yenation b!t lea"s to

re"!ctions in car"iac o!tp!t an" o)yen "elivery(

The re"!ction in :G impairs the capacity of the

obese patient to tolerate perio"s of apnoea( +besein"ivi"!als "esat!rate rapi"ly after in"!ction of

anaesthesia "espite pre-o)yenation( This is a res!lt

of havin a smaller o)yen reservoir in their re"!ce"

:G an" an increase in o)yen cons!mption(

3s!ally :G is re"!ce" as a conse*!ence of a

re"!ction in .GC #ith resi"!al vol!me &GC'remainin #ithin normal limits(13?o#ever, in some

obese patients GC is increase" s!estin astrappin an" co-e)istin obstr!ctive air#ays "isease(

:orce" e)piratory vol!me in 1 s an" force" vital

capacity are !s!ally #ithin the pre"icte" rane, b!t

- improvements have been "emonstrate" after

#eiht loss(A1

-3ygen onsumption and ar&on dio3ide prodution

+)yen cons!mption an" carbon "io)i"e pro"!ction

are increase" in the obese as a res!lt of the metabolicactivity of the e)cess fat an" the increase" #or4loa"

on s!pportive tiss!es(11$ 1$% Basal metabolic

activity as relate" to bo"y s!rface area is !s!ally

#ithin normal limits( ?ormocapnia is maintaine"!s!ally by an increase in the min!te ventilation,

#hich in t!rn lea"s to an increase" o)yen cost of

breathin(4,o#ever, most obese patients retain the

normal response to hypo)aemia an" hypercapnia( Ine)ercise, o)yen cons!mption rises more sharply

than in non-obese s!bJects, #hich implies respiratory

m!scle inefficiency(121

Gas e3hange

6orbi"ly obese in"ivi"!als !s!ally have only a

mo"est "efect in as e)chane preoperatively #ith a

re"!ction in Eao2

12@

an" increases in alveolar-to-arterial o)yen "ifference an" sh!nt fraction( These

"eteriorate mar4e"ly on in"!ction of anaesthesia an"

hih inspire" fractions of o)yen are re*!ire" to

maintain a"e*!ate arterial o)yen tensions( As

previo!sly state", E..E improves the Eao2b!t onlyat the e)pense of car"iac o!tp!t an" o)yen

"elivery(134

Lung ompliane and resistane

Increasin B6I is associate" #ith an e)ponential

"ecline in respiratory compliance; in severe cases,total compliance can fall to $0 of pre"icte"

norma1(124Altho!h acc!m!lation of fat tiss!e inan" aro!n" the chest #all lea"s to a mo"est

re"!ction in chest #all compliance, recent #or4

s!ests that the "ecrease in total compliance is

principally a conse*!ence of a "ecrease in l!n

compliance, this in t!rn bein the res!lt of an

increase" p!lmonary bloo" vol!meLM 128 Ge"!ce"compliance is associate" #ith a "ecrease in the

:G, encroachment on the closin vol!me an"

impairment of as e)chane(1%8 1>= >inificant

obesity is also associate" #ith an increase in total

respiratory resistance; once aain this is larely a

res!lt of an increase in l!n resistance(128 129 This

"eranement of l!n compliance an" resistanceres!lts in a shallo# an" rapi" pattern of breathin,increases the #or4 of breathin an" limits the

ma)im!m ventilatory capacity( As miht be

anticipate", these chanes are even more mar4e"

!pon ass!mption of the s!pine position(

espiratory effiieny and or1 of &reathing

As implie" in the previo!s section, the combination

of increase" mechanical press!re from the ab"omen,

re"!ction in p!lmonary compliance an" increase in

the metabolic "eman"s of the respiratory

m!sc!lat!re res!lt in respiratory m!scle inefficiency

an" an increase in the #or4 of breathin( Innormocapnic obese in"ivi"!als at rest, this may be

reflecte" in a mo"est $0 increase in the #or4 of

breathin, altho!h s!ch respiratory m!scle

inefficiency may limit the ma)im!m ventilatory

capacity an" lea" to relative hypoventilation at times

of hih metabolic activity( In the obese in"ivi"!al

#ith establishe" "aytime hypoventilation

syn"rome, #or4 of breathin may approach fo!r

times that pre"icte"(

Impliations for anaesthesia

Ereoperative assessment sho!l" incl!"e f!ll bloo"co!nt &to e)cl!"e polycythaemia', chest -ray,

s!pine an" !priht arterial bloo" ases, l!n

f!nction tests an" overniht o)imetry( Eatients #ith

symptoms of sinificant +>A sho!l" be consi"ere"

for polysomnoraphy an" may benefit preoperatively

from meas!res "esine" to combat noct!rnal air#ayobstr!ction, s!ch as noct!rnal nasal contin!o!s

positive air#ay press!re &EAE' or bilevel-positive

air#ay press!re &BIEAE'(1=1The anaesthetist sho!l"


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Obesity

patientDs ability to breathe "eeply an" sho!l" chec4 that thenostrils are patent( >pecific ris4s sho!l" be e)plaine" to the

patient, an" the possibilities of a#a4e int!bation, post-operative ventilation an" even tracheostomy "isc!sse"(F

Tracheal inc!bation an" positive press!re ventilation are

man"atory in the morbi"ly obese patient( The choice

bet#een a#a4e an" asleep inc!bation is "iffic!lt, an"

"epen"s !pon the anticipate" "iffic!lties in a partic!lar

patient alon #ith the e)perience of the anaesthetist(0>omea!thors recommen" a#a4e inc!bation #hen act!al bo"y

#eiht is 1% of IB/($ >inificant +>A symptoms

in"icate altere" !pper air#ay morpholoy an" ma4e control

of ba an" mas4 air#ay more "iffic!lt; some a!thorities

#o!l", therefore, a"vocate a#a4e int!bation in these

patients( Another approach is ently to attempt "irect

larnoscopy after anaesthetiin the pharny) #ith local

anaesthetic; if the laryneal str!ct!res cannot be vis!alie",then a#a4e fibreoptic inc!bation is the safest co!rse of

action( Blin" nasal inc!bation has been a"vocate" by some,

b!t sho!l" be avoi"e" by all b!t those very s4ille" in the

techni*!e, as epista)is an" s!bse*!ent "eterioration in

inc!batin con"itions are very real possibilities(

In"!ction of anaesthesia is li4ely to be a partic!larlyhaar"o!s time for the patient #ith an increase" ris4 of

"iffic!lt or faile" int!bation($1%1Ba an" mas4 ventilation

is li4ely to be "iffic!lt beca!se of !pper air#ay obstr!ction

an" re"!ce" p!lmonary compliance( @astric ins!fflation

"!rin ineffective mas4 ventilation #ill f!rther increase the

ris4 of re!ritation an" aspiration of stomach contents(

Apart from a#a4e fibreoptic int!bation, the safest

techni*!e is a rapi" se*!ence in"!ction !sin s!ccinylcho-

line follo#in a perio" of a"e*!ate preo)yenation( It is

essential to have s4ille" anaesthetic assistance toether #ith

a"e*!ate n!mbers of staff in or"er to t!rn the patient sho!l"

the nee" arise( A f!ll rane of ai"s for a "iffic!lt int!bationsho!l" be available, an" sho!l" incl!"e short-han"le", polio

bla"e an" 6coy larynoscopes, a !m elastic bo!ie an"

stan"ar" an" int!batin laryneal mas4 air#ays( .*!ipment

for cricothyroi"otomy an" transtracheal ventilation sho!l"

also be available( orrect position of the tracheal t!be m!st

be confirme" by both a!sc!ltation an" capnoraphy( It is

hihly "esirable to have the services of another e)perience"

anaesthetist thro!ho!t the in"!ction perio" rather than

havin to #ait for assistance if "iffic!lty is enco!ntere"(

Eerio"s of hypo)aemia an" hypercapnia may increase

p!lmonary vasc!lar resistance an" precipitate riht heart

fail!re( +bese patients sho!l" not be allo#e" to breathespontaneo!sly !n"er anaesthesia, as hypoventilation is li4ely

to occ!r, #ith conse*!ent hypo)ia an" hypercapnia( :!rtherrespiratory embarrassment #ill occ!r if the patient is place"

in the lithotomy or Tren"elenb!r position an" these sho!l"

be avoi"e" if at all possible(121 1$8 The obese patient #ill

re*!ire mechanical ventilation #ith hih inspire" o)yen

fractions, possibly #ith the a""ition of E..E to maintain an

a"e*!ate arterial o)yen tension; a

ventilator of s!fficient po#er an" sophistication is, there-fore, re*!ire"( .n"-ti"al capnoraphy is a poor !i"e to

a"e*!acy of ventilation in the obese patient beca!se of thealveolar-to-arterial "ifference in carbon "io)i"e in these

patients( Instea", serial arterial bloo" as analysis sho!l" be

!se" to assess a"e*!acy of min!te ventilation(

E!lmonary complications are more common in obesepatients,12% 18 1% b!t B6I an" preoperative l!n f!nction

tests are not acc!rate pre"ictors of postoperative prob-lems(12+bese patients may be more sensitive to the effects

of se"ative "r!s, opioi" analesics an" anaesthetic "r!s, so

they may benefit from a perio" of postoperative ventilation

to allo# safe elimination of resi"!al anaesthetic or se"ative

aents( Altho!h technically challenin, reional

anaesthetic techni*!es, s!ch as peripheral nerve an"thoracol!mbar epi"!ral bloc4a"e, may help to atten!ate

many of these problems(1$ Eostoperative ventilation is

more li4ely to be re*!ire" in obese patients #ho have

coe)istin car"iorespiratory "isease or carbon "io)i"e

retention an" in those #ho have !n"erone prolone"

proce"!res or #ho have "evelope" pyre)ia after the

operation(%2

The trachea sho!l" only be e)t!bate" #hen the patient isf!lly a#a4e an" transferre" to the recovery room sittin !p at

%F(10 !mi"ifie" s!pplemental o)yen sho!l" be

a"ministere" imme"iately, an" chest physiotherapy com-

mence" soon after the operation( >ome obese patients,

partic!larly those #ith a history of +>A, may benefit from

noct!rnal nasal EAE( .piso"es of +>A are most fre*!ent

"!rin rapi" eye movement &G.6' sleep, the e)tent of

#hich is relatively lo# in the initial postoperative perio",b!t in e)cess on the thir" to fifth postoperative nihts(121

The haar"s of +>A may, therefore, be at their #orst some

"ays after s!rery; this has obvio!s implications for the

"!ration of postoperative o)imetry an" o)yen therapy(

Obesity and the cardivascu$ar system

ar"iovasc!lar "isease "ominates the morbi"ity an" mor-

tality in obesity an" manifests itself in the form of ischaemic

heart "isease, hypertension an" car"iac fail!re( A recent

>cottish health s!rvey fo!n" the prevalence of any

car"iovasc!lar "isease #as $ in a"!lts #ith a B6I of

$0 4 m-2, 21 in those #ith a B6I of 2%-$0 4 m-2 an"only 10 in those #ith a B6I of 2% 4 m-2(111 All

morbi"ly obese patients presentin for anaesthesia sho!l"

be investiate" e)tensively for car"iovasc!lar complica-tions preoperatively an" certain patients sho!l" be referre" to

a car"ioloist for f!rther optimiation(

4ardio.asular derangement

Hypertension

6il" to mo"erate hypertension is seen in %0-0 of obese

patients an" severe hypertension in %-10,#ith a $- mm


18/37

A sand Murphy

increase in systolic an" a 2 mm increase in "iastolic

arterial press!re for every 10 4 of #eiht aine"($$ An

e)pansion of the e)tracell!lar vol!me, res!ltin in

hypervolaemia, an" an increase in car"iac o!tp!t are

characteristic of obesity-in"!ce" hypertension( The e)act

mechanism for hypertension in the obese is not 4no#n, an"

probably represents an interaction bet#een enetic, hormo-nal, renal an" haemo"ynamic factors( yperins!linaemia,

#hich is characteristic of obesity, can contrib!te byactivatin the sympathetic nervo!s system an" by ca!sin

so"i!m retention( In a""ition, ins!lin resistance may be

responsible for the enhancement in pressor activity of

norepinephrine an" aniotensin 11(119

ypertensionper se lea"s to concentric left ventric!lar

hypertrophy an" a proressively non-compliant left ven-tricle #hich, #hen a""e" to the increase" bloo" vol!me,

increases the ris4 of car"iac fail!re(12-1 1 121

/eiht loss has been sho#n to re"!ce hypertension in the

obese(8 1 19 2 1 10%

Ishaemi heart disease

It is no# enerally accepte" that obesity is an in"epen"ent

ris4 factor for ischaemic heart "isease$ 89 1,, an" is more

common in those obese in"ivi"!als #ith a central "istrib!-

tion of fat(10+ther factors s!ch as hypertension, "iabetes

mellit!s, hypercholesterolaemia an" re"!ce" hih "ensity

lipoprotein levels, #hich are all common in the obese, #ill

compo!n" the problem(11 Interestinly, 0 of obesepatients #ith anina "o not have "emonstrable coronary

artery "isease;111 in other #or"s, anina may be a "irect

symptom of obesity(

Blood .olume

Total bloo" vol!me is increase" in the obese b!t on avol!meH#eiht basis is less than that in non-obese in"ivi"-

!als &%0 ml 4-1compare" #ith % ml 4-1',2$ #ith most of

this e)tra vol!me bein "istrib!te" to the fat oran(

>planchnic bloo" flo# is increase" by 20 #hereas renal

an" cerebral bloo" flo# are n o ( 9

4ardia arrhythmias

Arrhythmias may be precipitate" in the obese by a n!mber

of factors7 hypo)ia, hypercapnia, electrolyte "ist!rbance

ca!se" by "i!retic therapy, coronary artery "isease,increase" circ!latin catecholamine concentrations, +>A,

myocar"ial hypertrophy an" fatty infiltration of the con-

"!ction system,$0 89 11$ 12 1%

4ardia funtion

The morbi"ly obese in"ivi"!al is at ris4 of a specific form of

obesity-in"!ce" car"iac "ysf!nction, altho!h the belief that

this is secon"ary to fatty infiltration of the heart &Ncor

a"ipos!mD' is no loner vali"( 1 A!topsy st!"ies have

sho#n that, altho!h increases in epicar"ial fat are common,

fatty infiltration of the myocar"i!m is !ncommon an" seemsto affect mainly the riht ventricle, the latter possibly bein

associate" #ith con"!ction abnormalities an" arrhythmias(1

There is a linear relationship bet#een car"iac #eiht an"

bo"y #eiht !p to 10% 4, after #hich car"iac #eiht

contin!es to increase, b!t at a slo#er rate($ 1== The increase

in heart #eiht is a conse*!ence of "ilation an" eccentric

hypertrophy of the left an", to a lesser e)tent, the riht

ventricle($ 1%

+ther#ise healthy obese in"ivi"!als "emonstrate an

increase" car"iac o!tp!t, elevate" left ventric!lar en"-"iastolic press!re &C.!ch eccentric left ventric!lar

hypertrophy res!lts in re"!ce" compliance an" left

ventric!lar "iastolic f!nction, i(e( impairment of ventric!lar

fillin, lea"in to elevate" C.


19/37

Obesity

Obstructive sleep apnoea obesity hypoventilation

1Hypoxia/hypercapnia

VPulmonary venous

hypertension

Obesity

Increased circulation

blood volume

Increased

stroke volume

Increased

cardiac output

1B6 enlargement

1Increased B6 all stress

1!ccentric B6 hypertrophy

"# systolic B6 diastolic


20/37

A sand Murphy

dys$unuction dys$unuction

LV failure I

Pulmonary arterial %# enlargement &hypertension - ~ hypertrophy

RT failure

Hypertension

Ischaemic heartdisease

Mg 2 The aetiology o& obesity cardiomyopathy) and its association with right-sided heart &ailure) systemic hypertension and ischaemic heart disease.B6) le&t ventricular# R6) right ventricular.


21/37

A sand Murphy

s!ch as anina or e)ertional "yspnoea may occ!r

only very occasionally, b!t act!ally coinci"e #ith

most perio"s of sinificant physical activity( 6any

in"ivi"!als #ill prefer to sleep !priht in a chair, an"

therefore "eny the symptoms of orthopnoea an"paro)ysmal noct!rnal "yspnoea( As4in the patient to

#al4 the lenth of the #ar" may reveal a mar4e"ly

re"!ce" e)ercise tolerance, an" ass!min the s!pine

position may pro"!ce sinificant orthopnoea an"

even car"iac arrest(1%$ The patient sho!l" have a

"etaile" an" thoro!h car"iovasc!lar e)amination,

loo4in in partic!lar for evi"ence of hypertension

ith an appropriately sie" bloo" press!re c!ff' an"

car"iac fail!re( >ins of car"iac fail!re, s!ch as

raise" J!!lar veno!s press!re, a""e" heart so!n"s,p!lmonary crac4les, hepatomealy an" peripheral

oe"ema, may all be "iffic!lt to elicit in the morbi"ly

obese s!bJect, an" investiations are in"icate"(

In.estigations

An electrocar"ioram is man"atory preoperatively( It

may be of lo# voltae beca!se of the e)cessoverlyin tiss!e an" as s!ch miht !n"erestimate the

severity of ventric!lar hypertrophy( A)is "eviationan" atrial tachyarrhythmias are relatively common(

hest ra"ioraphy may reveal car"iomealy

s!estive of car"iac fail!re, b!t is often normal(

.chocar"ioraphy may be "iffic!lt, b!t can provi"e

!sef!l

information, #ith eccentric left ventric!lar

hypertrophy s!estin sinificant obesity-in"!ce"

chanes even if ventric!lar f!nction appears

normal( Transoesophaeal echocar"ioraphy may

provi"e better imaes, especially of the left si"e ofthe h e , altho!h is obvio!sly more invasive(

Testin of e)ercise tolerance is li4ely to be

impossible if coronary artery "isease is s!specte"( If

time is available, the patient sho!l" be referre" to a

car"ioloist for f!rther investiation an"

optimiation, s!ch as control of bloo" press!re,

treatment of heart fail!re or coronary anioplasty(

Anaestheti impliations

In the presence of respiratory "isease, ventric!lar

impairment is almost inevitable, b!t its severitymay be !n"er-estimate" by clinical eval!ation(

Gapi" #eiht ain preoperatively may in"icate

#orsenin car"iac fail!re, altho!h #eiht ain

once a person has been accepte" for bariatric

s!rery is #ell reconie"(%9 1=, Intraoperative

ventric!lar fail!re may occ!r for a variety ofreasons, incl!"in rapi" intraveno!s fl!i"

a"ministration &in"icatin left ventric!lar "iastolic"ysf!nction', neative inotropy of anaesthetic aents

or p!lmonary hypertension precipitate" by hypo)ia

or hypercapnia( The anaesthetist sho!l" al#ays have

a selection of inotropes an" vaso"ilators to han"(


22/37

A sand Murphy

ar"iac performance is li4ely to "eteriorate follo#in

in"!ction of anaesthesia an" tracheal int!bation in the obese

patient In one st!"y of obese in"ivi"!als !n"eroin

ab"ominal s!rery, car"iac in"e) fell by 17-33% after

in"!ction an" int!bation, compare" #ith a fall of -11 in

lean controls( This "eranement persiste" postoperatively,

#ith the car"iac in"e) 1 3- 23 % less than preoperative

control val!es in the obese ro!p, #hereas in lean controls

car"iac performance ret!rne" to normal(

An arterial line #ill allo# acc!rate monitorin of arterial

press!re an" re!lar bloo" as analysis( entral veno!s

press!re monitorin is "esirable as it allo#s some assess-

ment of car"iac f!nction an" can be !se" for inotrope

inf!sions in case of "eterioratin car"iac performance(M

Eatients #ith "oc!mente" car"iac fail!re may benefit fromthe !se of a p!lmonary artery flotation catheter(

/ratial onsiderations

/remediation

+pioi" an" se"ative "r!s may ca!se respiratory "epressionin the morbi"ly obese1% an" are probably best avoi"e",

altho!h one st!"y faile" to "emonstrate an increase" ris4 of

o)yhaemolobin "esat!ration #ith beno"iaepines($1 The

intram!sc!lar an" s!bc!taneo!s ro!tes sho!l" be avoi"e",

since absorption is very !nreliable(%21% If a#a4e fibreoptic

int!bation is bein consi"ere", then an antisialoo!e maybe appropriate(

All morbi"ly obese patients sho!l" receive prophyla)is

aainst aci" aspiration even if they "o not "eclare any

symptoms of heartb!rn or refl!)( %2 1% 12 A combinationof an 2 bloc4er &e(( raniti"ine 1%0 m orally' an" a

pro4inetic &e(( metocloprami"e 10 m orally' iven 12 h

an" 2 h before s!rery #ill re"!ce the ris4 of aspiration

pne!monitis( >ome anaesthetists also a"vocate ivin 30 ml

of 0.3 6 citrate imme"iately before in"!ction as an e)tra

preca!tion(

6ost of the patientDs !s!al me"ications, s!ch as

car"iovasc!lar "r!s an" steroi"s, sho!l" be contin!e" as

normal !ntil the time of s!rery, altho!h it is recommen"e"

that aniotensin convertin enyme inhibitors be stoppe" onthe "ay before s!rery as their contin!ation can lea" to

profo!n" hypotension "!rin anaesthesia(

If the patient is "iabetic, a "e)trose-ins!lin reimen #ill be

re*!ire" for all b!t the shortest proce"!res( Ins!lin

re*!irements are li4ely to increase postoperatively( .)perta"vice from a "iabetoloist may be helpf!l(

6orbi"ly obese patients are more li4ely to be immobile

postoperatively an" are at increase" ris4 of "eep-veinthrombosis( o#-"ose s!bc!taneo!s heparin sho!l" be iven

as prophyla)is an" contin!e" into the postoperative phase

!ntil the patient is f!lly mobile( +ther antiembolic meas!res,

s!ch as pne!matic leins or ra"e" compression

stoc4ins, sho!l" be !se" #herever possible b!t may be

"iffic!lt to fit in larer patients(

This ro!p of patients is also at increase" ris4 of

postoperative #o!n" infection an" may re*!ire prophylactic

antibiotics( This sho!l" be "isc!sse" #ith the s!reon an"

also a microbioloist if appropriate(

/ositioning and transfer

6ost operatin tables are "esine" for patients of !p to 120-

10 4 in #eiht( .)cee"in this limit may p!t the patientan" staff at ris4( >pecially "esine" tables may be re*!ire",

or t#o normal tables may be place" si"e by si"e(%2

The patient sho!l" be anaesthetie" on the operatin table

in the operatin theatre to avoi" !nnecessary transfer fromthe anaesthetic room an" the associate" ris4s to both patient

an" staff( +nce the patient is in position, partic!lar care

sho!l" be pai" to protectin press!re areas, as the ris4 of

press!re sores an" ne!ral inJ!ries9is reater in the obese(

ompression of the inferior vena cava m!st be avoi"e" by

left lateral tilt of the operatin table or by placin a #e"e

!n"er the patient( >ome obese patients are best positione" in

the lateral "ec!bit!s position so as to re"!ce the amo!nt of#eiht loa"in on the chest(

Transfer of the obese patient aro!n" the hospital isprobably best "one on their o#n hospital be", as normal

theatre trolleys are li4ely to be ina"e*!ate for the p!rpose(Appropriate manpo#er sho!l" al#ays be available #hen

movin morbi"ly obese patients an" local liftin policies

sho!l" be a"here" to(

Intra.enous aess

This may be a problem beca!se of e)cessive s!bc!taneo!s

tiss!e( 6any anaesthetists #o!l" a"vocate establishin

central veno!s access, b!t this in itself can be "iffic!lt( 3se

of portable !ltraso!n" e*!ipment may improve s!ccess(

onitoring

Invasive arterial press!re monitorin has been a"vocate" forall b!t the most minor proce"!res in the morbi"ly obese(

%2 If a non-invasive c!ff is to be !se", it sho!l" be of an

appropriate sie, as stan"ar" c!ffs #ill ten" to over-

estimate the arterial press!re( E!lse o)imetry,

electrocar"ioraphy, capnoraphy an" monitorin of

ne!rom!sc!lar bloc4 are all man"atory( 3se of centralveno!s an" p!lmonary artery flotation catheters sho!l" be

consi"ere" in patients !n"eroin e)tensive s!rery or those

#ith serio!s car"iorespiratory "isease(

egional anaesthesia

The !se of reional anaesthesia in the obese re"!ces the

ris4s from "iffic!lt int!bation an" aci" aspiration an" alsoprovi"es safer an" more effective postoperative anal-

esia(12 :or thoracic an" ab"ominal proce"!res, most

anaesthetists a"vocate the !se of combine" epi"!ral an"

eneral anaesthesia( This has a"vantaes over eneral

anaesthesia alone, incl!"in re"!ce" opioi" an" potent

inhalational anaesthetic re*!irements, D2 earlier tracheale)t!bation, 1% re"!ce" postoperative p!lmonary compli-

cations D2 an" improve" postoperative analesia, allo#in

more rioro!s physiotherapy an" a better co!h(1$


23/37

Obesity

Geional anaesthesia in the obese can be technically

challenin beca!se of "iffic!lties in i"entifyin the !s!al

bony lan"mar4s( .pi"!ral an" spinal anaesthesia may be

ma"e easier by sittin the patient !priht an" by !sin

loner nee"les(3ltraso!n" has been s!ccessf!lly !se" in

the obese to i"entify the epi"!ral space an" to !i"e the

T!ohy nee"le into position(1$ >ome anaesthetists #o!l"

a"vocate the sitin of epi"!ral catheters on the evenin

before s!rery to save time the ne)t "ay, an" also to allo#

heparin prophyla)is to be iven on the mornin of s!rery(In the same #ay, peripheral nerve bloc4a"e may be ma"e

easier an" safer by the !se of ins!late" nee"les an" a nerve

stim!lator(

ocal anaesthetic re*!irements for epi"!ral an" spinal

anaesthesia are re"!ce" to %-80 of normal in themorbi"ly obese, since fatty infiltration an" the increase"

bloo" vol!me ca!se" by increase" infra-ab"ominal press!re

re"!ce the vol!me of the epi"!ral space(M 1%1 This can lea"

to an !npre"ictable sprea" of local anaesthetic an" vari-

ability in bloc4 heiht(8% 1$2 Bloc4s e)ten"in above T% ris4

respiratory compromise, an" car"iovasc!lar collapse sec-

on"ary to a!tonomic bloc4a"e(12$

:or these reasons, theanaesthetist m!st al#ays be prepare" to convert to eneralanaesthesia an" have the necessary e*!ipment an" assist-

ance imme"iately to han"(

ystemi analgesia

The !se of opioi" analesics may be haar"o!s in the obese(

The intram!sc!lar ro!te is not recommen"e" as it is

!npre"ictable an" has been sho#n to provi"e pooreranalesia than other ro!tes(1 1$ If the intraveno!s ro!te is

to be !se", then a patient-controlle" analesia system

&EA>' is probably the best option(2%EA> has been sho#n

to provi"e effective analesia in the obese, altho!h

respiratory "epression has been reporte"(1%%!pplemental o)yen an" close

observation, incl!"in p!lse o)imetry monitorin, are

recommen"e"(

Eostoperative epi"!ral analesia, !sin opioi"s or local

anaesthetic sol!tions, may provi"e the most effective an"

safest analesia for the obese patient(12The epi"!ral ro!te

for opioi" a"ministration is preferre" over other ro!tes

beca!se it pro"!ces less "ro#siness, na!sea an" respiratory

"epression, earlier normaliation of bo#el motility, im-prove" p!lmonary f!nction an" re"!ce" hospital stay( 1 2

1$ As a res!lt of the potential for "elaye" onset respiratory

"epression, s!pplemental parenteral opioi"s sho!l" probablybe avoi"e"( ontin!o!s epi"!ral analesia #ith local

anaesthetics has been sho#n to have a beneficial effect on

car"iovasc!lar f!nction, #ith a re"!ction in left ventric!lar

stro4e #or4,altho!h an associate" motor bloc4 #ill "elay

amb!lation(

All of the above reimens can be s!pplemente" #ith oral

analesics s!ch as paracetamol or non-steroi"al anti-

inflammatory "r!s if appropriate(

4onsiderations in o&stetris

The obese prenant patient presents partic!lar "iffic!lties,

#hich incl!"e7 &i' increase" ris4 of chronic hypertension,

pre-eclampsia an" "iabetes;$ 8 &ii' hiher inci"ence of

"iffic!lt labo!r #ith increase" li4elihoo" of instr!mental

"elivery an" aesarean section;8 1$2 &iii' aesarean section

operations ten" to be loner1$o#ith a hiher inci"ence of

postoperative complications, incl!"in reater bloo" loss,

"eep-vein thrombosis an" #o!n" infection or "ehiscence;8

&iv' increase" ris4 of anaesthesia-relate" morbi"ity an"

mortality "!rin aesarean section an" in partic!lar,increase" ris4 of faile" int!bation an" astric aspiration

"!rin proce"!res !n"er eneral anaesthesia;8 &v' in-

crease" inci"ence of m!ltiple, faile" attempts at epi"!ral

sitin;8 1$2 &vi' increase" ris4 of fetal morbi"ity an"

mortality, #ith some st!"ies sho#in an increase" inci"ence

of fetal "istress;8&vii' s!pine an" Tren"elenb!r positions

f!rther re"!ce :G, increasin the possibility ofhypo)aemia; &viii' some st!"ies sho# a reater cephala"

sprea" of local anaesthetic "!rin spinal an" epi"!ral

anaesthesia;8!i0" loss of intercostal m!scle f!nction "!rinspinal anaesthesia lea"in to respiratory "iffic!lty; &)'

possible severe re"!ction in car"iac o!tp!t #ith eneral

anaesthesia, relate" to profo!n" aorto-caval compressionan" the !se of E..E(

olutions

If at all possible, eneral anaesthesia sho!l" be avoi"e" in

the prenant obese patient( If it is absol!tely essential, then a

"iffic!lt int!bation sho!l" be anticipate" an" the appropriate

assistance an" e*!ipment ma"e rea"ily available( If time is

available, an a#a4e fibreoptic int!bation sho!l" be con-

si"ere"( A clear action plan m!st have been form!late" for

the possibility of a faile" int!bation( The motherDs safetym!st come first; if a faile" int!bation is "eeme" li4ely, then a

rapi" se*!ence in"!ction sho!l" not be consi"ere"(>itin an epi"!ral catheter early in labo!r allo#s the

anaesthetist to establish oo" analesia in a calm an"

controlle" atmosphere rather than havin to r!sh in the

event of an emerency sit!ation(8.pi"!ral analesia can be

s!pplemente" for operative proce"!res an" may re"!ce the

li4elihoo" of post-part!m "eep-vein thrombosis(

N>inle-shotD spinal anaesthesia may be ina"e*!ate for a

prolone" aesarean section, so consi"eration sho!l" be

iven to a combine" spinal-epi"!ral techni*!e if a

s!barachnoi" bloc4 is favo!re"( ocal anaesthetic re*!ire-

ments may be re"!ce" by !p to 2% in the obese prenant

state(

Anaesthesia and the o&ese hild

+ver#eiht chil"ren become obese a"!lts( It appears that

bo"y fat "istrib!tion is more important than percentae bo"y

fat in "eterminin car"iovasc!lar ris4 factors for later life(%%

$ In a % yr follo#-!p st!"y, all-ca!se an"


24/37

A sand Murphy

car"iovasc!lar mortality #as reater for a"!lts #ho ha" ha" a

hiher chil"hoo" B6I(80

The chil" #ith Era"er-/illi syn"rome is li4ely to present apartic!lar challene to the anaesthetist(% :eat!res of the

syn"rome incl!"e hypotonia, mental retar"ation, obesity,

"iabetes mellit!s, scoliosis an" sleep apnoea hich may

#orsen postoperatively'( ar"iovasc!lar "ist!rbance

&hypertension, arrhythmias', restrictive p!lmonary "efects

an" thermore!latory abnormalities have also been "e-scribe"( It #o!l" seem pr!"ent that these chil"ren sho!l" be

anaesthetie" in specialist centres that have e)perience of

the con"ition(

Laparosopi proedures in the o&ese

the respiratory mechanics an" arterial bloo" ases in 1%

morbi"ly obese patients !n"eroin laparoscopic astro-

plasry( They sho#e" that ab"ominal ins!fflation to 2(2 4Ea

le" to a $1 "ecrease in respiratory compliance, increases of1 an" $2 in pea4 an" platea! air#ay press!res &at

constant ti"al vol!me', sinificant hypercapnia b!t no

chane in arterial o)yen sat!ration( E!lmonary compliancean" ins!fflation press!res ret!rne" to baseline val!es after

ab"ominal "eflation an" the proce"!res #ere #ell tolerate"(

>imilarly, O!vin an" collea!es9 "emonstrate" that obese

patients !n"eroin laparoscopic astroplasry ha" sinifi-

cantly re"!ce" analesic re*!irements, #ere able to #al4

sooner an" ha" a shorter hospital stay than a comparable

ro!p of patients #ho ha" ha" an open proce"!re(

aparoscopy for astroplasty may improve the imme"iatepostoperative co!rse b!t the anaesthetist m!st be a#are that

Tren"elenb!r an" reverse Tren"elenb!r positions areli4ely to be poorly tolerate" an" that hypercarbia may ca!se

arrhythmias an" car"iovasc!lar instability "!rin the pro-

ce"!re(

Obesity and %astrintestina$ disrders

It is commonly believe" that combination of increase" intra-

ab"ominal press!re, hih vol!me an" lo# p of astric

contents,1%9 "elaye" astric emptyin an" an increase"

inci"ence of hiat!s hernia an" astro-oesophaeal refl!)

place the obese patient at a hiher ris4 of aspiration of

astric content follo#e" by aspiration pne!monitis( Gecentst!"ies, ho#ever, have challene" this contention( Pacchian" collea!es10 sho#e" that obese patients #itho!t

symptoms of astro-oesophaeal refl!) have a resistance

ra"ient bet#een the stomach an" the astro-oesophaeal

J!nction similar to that in non-obese s!bJects in both the

lyin an" sittin positions( Altho!h obese in"ivi"!als have a

% reater astric vol!me than normal in"ivi"!als, recent

#or4 has sho#n that astric emptyin is act!ally faster in

the obese, especially #ith hih-enery content

inta4e s!ch as fatty em!lsions( o#ever, as a res!lt of the

larer astric vol!me, the resi"!al vol!me is larer in obese

in"ivi"!als(18 Both the faster astric emptyin an" the

larer astric vol!me can be partially reverse" by #eiht

loss(1%2ome st!"ies sho# a

10 inci"ence of an abnormal l!cose tolerance test in

patients !n"eroin bariatric s!rery(121All obese patients

sho!l" have a ran"om bloo" s!ar test performe"

preoperatively an", if in"icate", a l!cose tolerance test(

The catabolic response to s!rery may necessitate the !se of

ins!lin postoperatively to control l!cose concentrations(

:ail!re to control bloo" l!cose concentrations a"e*!ately

#ill ren"er the patient more s!sceptible to #o!n" infectionsan" #ill increase the ris4 of myocar"ial infarction "!rin

perio"s of myocar"ial ischaemia(1$$

Throm&oem&oli disease

The ris4 of "eep-vein thrombosis in obese patients !n"er-

oin non-malinant ab"ominal s!rery is appro)imately

t#ice that of lean patients &8 vs 2$', #ith a similar

increase" ris4 of p!lmonary embol!s(%F 121 It is thecommonest complication of bariatric s!rery, #ith the

inci"ence reporte" to be bet#een 2( an" (%(0 121

The increase" ris4 of thromboembolic "isease in obese

patients is li4ely to res!lt from prolone" immobiliation

lea"in to veno!s stasis, polycythaemia, increase" ab"om-

inal press!re #ith increase" press!re in the "eep veno!s

channels of the lo#er limb, car"iac fail!re an" "ecrease"

fibrinolytic activity #ith increase" fibrinoen concentra-tions( 6eas!res to prevent veno!s thromboembolism sho!l"

al#ays be ta4en(

!ru% hand$in% in besity

The physioloical chanes associate" #ith obesity lea" to

alterations in the "istrib!tion, bin"in an" elimination ofmany "r!s(l 2 11% The net phamaco4inetic effect in any

patient is often !ncertain, ma4in monitorin of clinical

en"-points &s!ch as heart rate, arterial press!re an"

se"ation' an" ser!m concentrations of "r!s moreimportant than empirical "r! "osin base" on p!blishe"

"ata(11% 12 :or "r!s #ith narro# therape!tic in"ices

&e(( aminophylline, aminolycosi"es or "io)in', to)ic

reactions may occ!r if patients are "ose" accor"in to their

act!al bo"y #eiht(L 2 9 11%


25/37

Obesity

A&sorption

+ral absorption of "r!s remains essentially !nchane" in

the obese patient(9

5olume of distri&ution

:actors that affect the apparent vol!me of "istrib!tion &C "'

of a "r! in the obese incl!"e the sie of the fat oran,

increase" lean bo"y mass, increase" bloo" vol!me an"car"iac o!tp!t, re"!ce" total bo"y #ater, alterations in

plasma protein bin"in an" the lipophilicity of the "r!($

Thiopental, for instance, has an increase" 6d beca!se of its

hihly lipophilic nat!re an" also beca!se of the increase"

bloo" vol!me, car"iac o!tp!t an" m!scle mass(11Therefore

the absol!te "ose sho!l" be increase", even tho!h on a#eiht-for-#eiht basis the "ose re*!ire" #ill be less than

that for a lean in"ivi"!al( An increase in the vol!me of

"istrib!tion #ill re"!ce the elimination half-life !nless the

clearance is increase"('2 /ith thiopental an" other lipophilic

"r!s &s!ch as beno"iaepines or potent inhalational

anaesthetic aents', effects may persist for some time after

"iscontin!ation(

There may be variable effects of obesity on the proteinbin"in of some "r!s( The increase" concentrations of

trilyceri"es, lipoproteins, cholesterol an" free fatty aci"s

may inhibit protein bin"in of some "r!s, an" so increase

free plasma concentrations(1 In contrast, increase" con-

centrations of al aci" lycoprotein may increase the "eree

of protein bin"in of other "r!s &e(( local anaesthetics', so

re"!cin the free plasma fraction(

"limination

Altho!h histoloical abnormalities of the liver are rela-

tively common, hepatic clearance is !s!ally not re"!ce" in

the obese( Ehase I reactions &o)i"ation, re"!ction an"

hy"rolysis' are !s!ally normal or increase" in obesity,

#hereas metabolism of some "r!s by phase II reactions

&e(( loraepam' is consistently increase"( ar"iac fail!re

an" re"!ce" liver bloo" flo# may slo# the elimination of

"r!s that are rapi"ly eliminate" by the liver &e((mi"aolam or li"ocaine'(11%

Genal clearance increases in obesity beca!se of the

increase" renal bloo" flo# an" lomer!lar filtration rate( "1?

In obese patients #ith renal "ysf!nction, estimates of thecreatinine clearance from stan"ar" form!lae ten" to be

inacc!rate an" "osin reimens for renally e)crete" "r!s

sho!l" be base" instea" on meas!re" creatinine clearance(1

Inhalational anaesthetis

The tra"itional theory that slo# emerence from anaesthesia

in morbi"ly obese patients is a res!lt of "elaye" release of

volatile aent from e)cessive a"ipose tiss!e has been

challene"(108Ge"!ctions in bloo" flo# to the fat oran may

limit the "elivery of volatile aents to fat stores, #ith the

slo# emerence more probably res!ltin from increase"

central sensitivity( In fact, some st!"ies "emonstrate

comparable recovery times in obese an" lean s!bJects for

anaesthesia lastin 2- h(53

+bese patients may be more s!sceptible to the ill-effects

of altere" hepatic metabolism of volatile aents( Elasmaconcentrations of bromi"e, a mar4er of re"!ctive an"

o)i"ative metabolism of halothane, are increase" in obese

patients(121 Increase" re"!ctive metabolism may be an

important factor in the "evelopment of liver inJ!ry after

e)pos!re to halothane, an" this may be more li4ely in obese

in"ivi"!als at ris4 from hypo)aemia an" re"!ce" liver bloo"

flo#( oncentrations of inoranic free fl!ori"e ions are

hiher in obese patients follo#in e)pos!re to halothane orenfl!rane, increasin the ris4 of nephroto)icity 2 7 2 8 This

"oes not appear to be the case #ith sevofl!rane, "espite its

sinificant hepatic metabolism( :l!ori"e concentrations

are not sinificantly increase" after isofl!rane anaesthe-

sia,19so this remains the inhalational aent of choice for

many anaesthetists( Altho!h its rapi" elimination an"

analesic properties ren"er nitro!s o)i"e potentially attract-

ive, its !sef!lness is limite" by the hih o)yen "eman"s ofmany morbi"ly obese patients( The infl!ence of obesity on

the pharmaco4inetics of commonly !se" anaesthetic "r!s

is s!mmarie" in Table $(

'rauma and the bese patient

It is a #i"ely hel" belief that the o!tcome of tra!ma in obese

patients is poor, b!t "ata to s!pport this are scarce(

Bo!laner an" collea!es e)amine" retrospectively thepattern of bl!nt tra!ma in obese an" non-obese in"ivi"!als

over a yr perio"($The obese ro!p ten"e" to be involve"

more in car crashes &2( vs %(1' an" to have better@> scores, an" they #ere more li4ely to have rib fract!res,

p!lmonary cont!sions, pelvic fract!res an" e)tremity frac-

t!res( They #ere less li4ely to have s!ffere" hea" tra!ma or

liver inJ!ries( >mith-hoban an" collea!es reporte" an

eiht-fol" increase in mortality follo#in bl!nt tra!ma inmorbi"ly obese patients compare" #ith the non-obese(1%

The metabolic response to severe tra!ma appears to be"ifferent in obese an" non-obese s!bJects( Oeevanan"am an"

collea!es9$ sho#e" that tra!matie" obese patients

mobilie" relatively more protein an" less fat than non-

obese victims( In other #or"s, they #ere !nable to !se their

most ab!n"ant f!el so!rce( They s!est that the n!tritional

manaement of obese tra!ma victims sho!l" provi"eeno!h l!cose calories to spare protein(

are of the morbi"ly obese tra!ma victim in theres!scitation room is li4ely to prove "iffic!lt( @iven the

hih probability of !n"erlyin car"iorespiratory impair-

ment, s!ch patients are li4ely to re*!ire hih inspire"

o)yen fractions, early int!bation an" respiratory s!pport,

metic!lo!s fl!i" res!scitation #ith invasive monitorin, an"

a"e*!ate personnel to transport them aro!n" the emerency


26/37

A sand Murphy

Table 3 5n&luence o& obesity on the pharmacokinetics o& anaesthetic drugs !adapted &rom re&erence 1=3". T(7total body weight) B(7lean body weight)M8C 7 minimum alveolar concentration

Drug Altered pharmacokinetics Clinical implications


27/37

Obesity

HypnoticsThiopental

ropo&ol

Mida9olam) dia9epam

Neuromuscular lockingdrugs uccinylcholine

8tracurium

6ecuronium

ancuronium

$imethyltubocurarine !pioids

entanyl8l&entanilMorphine

"ocal anaestheticsBidocaine

(upivacaine

InhalationalanaestheticsDitrous o0ide

'alothane

En&lurane

evo&lurane

5ncreased central volume o& distribution#prolonged elimination hal&-li&e

Bittle knownCentral volume o& distribution increases inline with body weight# prolonged elimination

hal&-li&e

lasma cholinesterase activity increases inproportion to body weight

Do change in absolute clearance) absolutevolume o& distribution and absoluteelimination hal&-li&e 5mpaired hepaticclearance and increased volume o&distribution lead to delayed recovery time

Bow lipid solubility

Elimination hal&-li&e increases in proportion with ;obesity

Do change in elimination &ollowing 1,

.tg kg-1

Elimination may be prolonged

Do in&ormation available

Bittle in&ormation

Considerable deposition in adipose tissue# increasedrisk o& reductive hepatic metabolism

(lood:gas partition coe&&icient &alls with increasingobesity# inorganic &luoride concentrations

rise twice as &ast in obese individuals

Do di&&erence in &luoride concentrationsbetween obese and non-obese patients

5ncreased absolute dose# reduced dose per unitbody weight# prolonged duration o& action

5ncreased absolute dose# reduced dose per unitbody weight 5ncreased absolute dose) same doseper unit body weight# prolonged duration o&

action) particularly a&ter in&usion

5ncreased absolute dose# reduced dose per unitbody weight# doses o& 12,-1=, mg appearsatis&actory

/nchanged dose per unit body weight

Give according to estimated lean body weight

/nchanged dose per unit bodyweight Give according toestimated B(

$ose per unit body weightunchanged 8d+ust dose toB(5ncreased absolute C


28/37

A sand Murphy


29/37

Obesity

"epartment( Blee"in is li4ely to pro"!ce earlycar"iovasc!lar "ecompensation an" so sho!l" be

vioro!sly so!ht an" treate"( Eortable ra"ioraphs

may be of poor *!ality beca!se of overlyin soft

tiss!e, an" clinical sins may be "iffic!lt to elicit(6ore sophisticate" imain techni*!es, s!ch as T

scannin, may be nee"e", altho!h many T tables

have #eiht restrictions of abo!t 10 4( The

atten"in physician sho!l" al#ays consi"er thepossibility of covert patholoy in the obese tra!ma

patient(

'he bese patient n the intensive care

unit

:e# "ata are available on the morbi"ity an"

mortality of obese patients in the intensive care

settin, b!t aain it is #i"ely hel" that the o!tcome

is poor(


30/37

A sand Murphy

The morbi"ly obese patient is li4ely to have sinificant

car"iovasc!lar impairment an" to tolerate fl!i" loa"in

poorly( Invasive haemo"ynamic monitorin may assist in

titratin fl!i" replacement an" assessin car"iac perform-

ance( >itin of central veno!s catheters may be "iffic!lt,

res!ltin in a hiher inci"ence of catheter misplacement an"

local complications s!ch as infection an" thrombosis($8

:emoral vein catheteriation may be impossible o#in to

local intertrio( erry 5!( "ambert ;%( et a" :actors in$luencing le$tventricular systolic $unction in nonhypertensi)e morbidly obese

patients( and e$$ect o$ eight loss induced by /astroplasty.Am *Cardiol 199" 10 4 4

1$Alpert MA( "ambert ;%( >erry 5!( et a" In$luence o$ le$tventricular mass on le$t ventricular diastolic $illing in

normotensi)e morbid obesity.Am Heart * 199, 1"$# 1$68!+"

1Alpert MA( "ambert ;%( 0anayiotou H( et al+ %elation o$ durationo$ morbid obesity to le$t ventricular mass( systolic $unction( and

diastolic $illing( and e$$ect o$ eight loss+ Am * Cardiol 199, =011,3

1%Alpert MA( "ambert ;%( >erry 5!( et a" !$$ect o$ eight loss onle$t ventricular diastolic $illing in morbid obesity+ Am

*Cardiol

199, +6# 1 198!2$1

1Alpert MA( "ambert ;%( >erry 5!( et a" Interrelationship o$ le$tventricular mass( systolic $unction and diastolic $illing in

normotensi)e morbidly obese patients+ Int J Obes %elat MetabDisord 199, 19# 99

1Amad 8H( 5rennan *;( Alexander *8+ >he cardiac patholo/y o$chronic eo/enous obesity. ;irculation 196, "2# 39

18Andersen *( %asmussen *P( !riksen *+ Pulmonary $unction inobese patients scheduled $or euno!ileostomy.Acta Anaesthesiol7cand 1,. 21# "'6!,1

19Anderson *7( )ri$$en


31/37

Obesity

7erum inorganic $luoride levels in obese patients during and a$teren$lurane anesthesia+ AnesthAnalg 1,,. ,8# 3,12

28 5entley *5( #aughan %


32/37


33/37

Obesity

intraoperati)e and postoperati)e hemodynamic study+Anest)Analg 1,-. 9,0 ,2-

- )ilbert >5( 7ene$$ M)( 5ecker %5+ :acilitation o$ internal Cugularvenous cannulation using an audioguided 'oppler ultrasoundvascular access device0 results $rom a prospecti)e dualcenter(randomiEed( crossover clinical study+ Crit Care Med 199, 2"# =9

, )ratE I( A$shar M( 8idell P( *( *a)ey 7mith )+;hildhood obesity and adult cardiovascular mortality0 a 9y

$olloup study based on the 5oyd Orr cohort+ Am J Clin Nutr1998 6+# 1 1 1 1!8

-1 Halaka 8( MustaCoki P( Aittomaki *( %o)iar)iA%+ !$$ect o$ eightloss and body position on pulmonary $unction and /as exchange

abnormalities in morbid obesity+ IntJ O#es $elat Meta# Disord 199,19# "'"!67 686

-2 Harris >( ;ook :( )arrison %( Higgins M( 8annel aylor M"( "iu 7( Mark "+ Magneticresonance imaging o$ cerebrospinal $luid volume and the

in$luence o$ body habitus and abdominal pressure+Anesthesiology1996 8'# 1"'1!9

-= Holley H7( Milic!mili *( 5ecklake M%( 5ates '#+ %egional

distribution o$ pulmonary ventilation and per$usion in obesity. JClin In4est 1,=. '6# '+,!81

- Hood ''( 'ean 'M+ Anesthetic and obstetric outcome inmorbidly obese parturients.Anesthesiology 199" +9# 121$!18

88 Hsieh 7'( ?oshinaga H+ Abdominal $at distribution and coronaryheart disease risk $actors in menaist/height ratio as a simple

and use$ul predictor+ IntJ O#es $elat Meta# $isord 199, 19# ,8,!9

89 Hubert H5( :einleib M( Mc6amara PM( ;astelli %( Mc6amaraPM+ >he relation o$ adiposity to blood pressure and thedevelopment of hypertension# >he :ramingham study+ Ann #ntMed 186+ 6+# '8!,9

100 8annel he obese patient in the I;G+ C)est1998 11"# '92!8

11 Manson *!( ;olditE )A( 7tamp$er M*( et alA prospecti)estudy o$ obesity and risk o$ coronary heart disease in omen+ Ne6

EnglJ Med 199$ "22# 882!9


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A sand Murphy

11 Mayersohn M( ;alkins *M( Perrier ')( et a' >hiopentalkinetics in obese patients+Anesthesiology 1981 ,,# 1-A

118 Messerli :H( 7undgaard%iise 8( %eisen !( 'reslinski )%('unn :)( :rohlich !+ 'isparate cardiovascular e$$ects o$ obesity

and arterial hypertension.Am J Med 198" +'# 8$8!12

119 Mikhail 6( )olub M7( >uck M"+ Obesity and hypertension.Prog "ardio)as! $is 1999 '2# "9!,8

120 Millman %P( Meyer >*( )eloff 7!+ 7leep apnea in themorbidly obese. (hode #sland Med 1992 +,# '8"!6

121 Murphy P)+ Obesity+ In0 Hemmings H; *r( Hopkins PM( eds+


35/37

Foundations o& Anaesthes ia. Bas ic and Clinical Sciences. "ondon0 Mosby( 2. 41 I

122 6ational Institutes o$ Health ;onsensus *e)elopment ;on$erence 7tatement Health implications o$ obesity+ Ann Int Med 198, 1$"# 1'+!,1

12" Ober/ 5( Poulsen >'+ Obesity0 an anaesthetic challenge+ Acta Anaesthesiol Scand 1996 30 1,12

12' Partinen M( )uilleminault ;+ 'aytime sleepiness and vascular morbidity at sevenyear follo

Chest 199$ 9+# 242

12, Pasulka P7( 5istrian -R7 5enotti P6+ >he risks o$ surgery in obese patients+Ann Int Med 1986 1$'# 93 6

126 Paul '%( Hoyt *"( 5outros A%+ ;ardiovascular and respiratory changes in response to change o$ posture in the very obese+ Anesthesio logy1,=. ',# 4-

12 Pelosi P( Ra)a/nan I( )iurati )( Panigada M( 5uttoni 6( >redici 7+ Positive endexpiratory pressure improves respiratory $unction in obese

but not in normal subCects during anesthesia and paralysis.Anesthesio logy 1999 91# 1221!"1

128 Pelosi P( ;roci M( Ra)a/nan I( #icardi P( )attinoni "+ >otal respiratory system( lung( and chest all mechanics in sedated paraly4ed

postoperati)e morbidly obese patients. Chest 1996 1$9# 1''!,1

129 Pelosi P( ;roci M( Ra)/nan I( et aL >he e$$ect o$ body mass on lung volumes( respiratory mechanics( and gas exchange during generalanesthesia+Anesth Analg 1998 8+# K 9 3

1"$ Perlo *H( Morgan MA+ Massive maternal obesity and perioperati)e cesarean morbidity+Am Obstet Gynecol 199' +$# ,6$!,1"1 Perry A;( 3pple/ate !5( Allison M'( *ackson M"( Miller P;+

;linical predictability o$ the aisttohip ratio in assessment o$cardiovascular disease risk $actors in overeight( pre

menopausal omen+ Am Clin Nutr 1998 68# 122

1"2 Pitkanen M>+ -ody mass and spread o$ spinal anesthesia ith

bupi)acaine.AnesthAnalg 198+ 66# 12+!"1

1"" %aucolesAime M( 5rimaud '+ 'iabetes mellitus0 implications $or

the anesthesiologist Curr OinAnesth 1996 9# 2391

1"' %aal 6( 7Costrand G( ;hristo$$erson !( 'ahlstrom 5( Arvill A(

%ydman H+ ;omparison o$ intramuscular and epidural morphine

$or postoperati)e analgesia in the grossly obese+ In$luence on

postoperati)e ambulation and pulmonary $unction+ Anesth Analg

198' 6"# ,8"!92

1", %ay ;( 7ue '( 5ray )( Hansen *!( aivainen >( >uominen M( %osenberg PM+ In$luence o$ obesity on the spread o$ spinal analgesia a$ter inCection o$ plain +9bupi)acaine at the " or "N9 interspace+ Br Anaesth 1,,. =30 ,'2!6


36/37

1%2 >osetti ;( ;orinaldesi %( 7tanghellini #( et al. )astric emptyin/ o$ solids in morbid obesity+ #ntJ Obes Relat $etab $isord 1996 2$# 29

1%$ >sueda 8( 'ebrand M( Beok 77( hi 56( "ormeau 5( Paries *( Attali *%+ ;ardiac autonomic $unction in obese patients+ IntJ Obes Relat $etab $isord 199, 19#11"!18

1%% #an'ercar 'H( MartineE AP( 'e "isser !A 7leep apnea syndromes0 a potential contraindication $or patient!controlled anal/esia.Anesthesiology 1991 +'# 62"!'

1% #aughan %


37/37

Adams and Murphy

165 Warnes CA, Roberts WC. The heart in massive (more than 1 Wisen 0 , Hellstrom !. Gastrointestinal motility in obesit". #

$o%n&s or 136 'ilorams) obesit"* anal"sis o+ 1 $atients st%&ie& Med 1--5 /3*1 112at nero$s".Am # Cardiol 1-2 5* 102/-1 1 4o%n T, alta !, em$se" #, S'atr%& #, Webber S, a&er S.

166 Wasan 7!, 8o e9erestein :. The in+l%ene o+ o%rrene o+ slee &isor&ere& breathin amon mi&&leli$o$roteins on the $harmao'inetis an& $harmao&"namis a&%lts. New Engl J Med 1--3 32* 1305

o+ li$o$hili &r%s an& &r% arriers. Ar ch Me d Re s 1--3 * 3-5 1 ;ahi , !earin

Documents

Obesity in Anestesia and Intensive Care