Does Compounding of Local Anesthetic Agents.25

8/10/2019 Does Compounding of Local Anesthetic Agents.25

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579

Does Compounding

of

Local Anesthetic Agents

Increase Their Toxicity

in

Humans?

DANIEL C. MOORE, M.D.

L DONALD BRIDENBAUGH, M.D.

PHILLIP

0

RIDENBAUGH, M.D.

GALE E THOMPSON, M.D.

GEOFFREY

T.

TUCKER, Ph.D.t

Seatt le, Wash ing ton *

s

YET the ideal local anesthetic agent

A has not been produced. The pharma-

cologic and physiologic characteristics of

such an agent probably would include:

(1)

rapid onset;

(2)

wide and rapid spread,

with deep penetration of nerves; (3) low

tissue toxicity; 4 ) low systemic toxicity;

(5) rapid absorption from the site of injec-

tion, so as not to cause tumefaction; (6)

rapid detoxification, without accumulation

of the drug or its metabolic byproducts;

(7) stability, permitting heat sterilization;

8)

high solubility in cold physiologic

sa

line solutions; and

(9)

prolonged duration

of action,

so that a single-dose rather than

a continuous-dose technic might be em-

ployed. These characteristics should not de-

pend on the use

of

a vasoconstrictor drug

in the local anesthetic solution, but should

be maintained if vasoconstrictors are indi-

cated.

To approach these requirements, we and

others have used the technic of compound-

ing (mixing of two local anesthetic agents)

to take advantage of the rapid onset, spread,

and penetration of one agent and the pro-

longed duration of action

of

another.1-*

Either dibucaine or tetracaine has been

compounded with chloroprocaine, hexyl-

caine, lidocaine, mepivacaine, or procaine

in approximately 2098 patients for caudal

and epidural blocks.1-3

*The Mason Clinic, Seattle, Washington 98101.

?University of Washington School

of

Medicine, Seattle, Washington 98105. Virginia Mason Research

Center, Seattle, Washington 98101.


2/7

580 ANESTHESIA

ND

ANALGESIA.

.Current Researches

VOL.51,

NO. ,

JULY-AUGUST972

In white rats, white mice, and in dogs,

the compounding of tetracaine with chloro-

procaine, lidocaine, mepivacaine, procaine,

and prilocaine has increased the incidence

of systemic toxic reactions and deaths in

comparison with the use of these agents

singly.5--7 Additive or synergistic action has

been considered the cause of increased tox-

icity, with the implication of similar effects

in

This paper presents the results of our

use of compounded solutions in humans, in

partial answer to the question, Is toxicity

increased when compounded solutions of

local anesthetic agents are injected into

humans?

METHOD

The following data were abstracted from

the anesthetic records of patients given com-

pounded so lu tion s of lo ca l anesthetic

agents: (1) types and number of blocks

administered; 2 ) dosage of the two local

anesthetic agents; (3) dosage of vasocon-

strictor drugs; 4) onset and establishment

of surgical anesthesia;

(5)

duration of the

block; (6) complications. Duration was de-

termined by noting the time in the postop-

erative period when the patient complained

of pain in the operated area, or during the

surgical procedure when there was evidence

of the block dissipating, indicated by pain

in the conscious patient, or, in the semicon-

scious or unconscious patient, restlessness;

increased respiration, blood pressure,

or

pulse rate; return of muscle tone; the need

for additional anesthesia to complete the

surgical procedure; or combi nati on s of

these. Complications included those from

the local anesthetic agents themselves, such

as local tissue toxicity, generalized systemic

toxic reactions, or neurologic sequelae, but

TABLE

1

Number

o f

Epidural Caudal an d Peripheral

Nerve Blocks Performed with Compounded

Solutions for Surgical and Obstetric

Procedures

N u m b e r o f N u m b e r o f

C o m p o u n d e d a g e n t s e p i d u r a l o n d p e r i p h e r a l

c oud o l b l oc k s ne r v e b l oc k s

Lidocaine + tetracaine 6277 1

Mepivacaine

+

tetracaine

2539 986

Chloroprocaine+ tetracaine

638 12

Propoxycaine + tetracaine

78

0

Prilocaine + tetracaine

3 4

9535 1003

Total

10,538

not those inherent in technic, such as hypo-

tension from sympathetic blockade follow-

ing epidural block.

RESULTS

All blocks were performed as described

earlier,4 and compounded solutions were

used in single-dose technics only.

NUMBER

F PATIENTS OCALANESTHET-

FORMED.

-From

1952,

when we

started

to

use compounded solutions (chloroprocaine,

lidocaine, mepivacaine, prilocaine, or pro-

poxycaine plus tetracaine) through 1970, a

total of 10,538 patients received such solu-

tions for (1) caudal block; 2 ) epidural

block;

(3)

brachial plexus block; or 4) sci-

atic and femoral nerve blocks, with or with-

out lateral femoral cutaneous nerve block,

obturator nerve block, or both (tables 1and

2). Compounding of solutions for periph-

eral nerve block was not started until

1967.

IC AGENTSEMPLOYED AND BLOCKS ER-

TABLE 2

Types and Numbers of Peripheral Ner ve Blocks Done wi th

Compounded Solutions for Operat ive Procedures

Blocks

L i d o c a i n e + M e p i v a c o i n e + Pr i l oc a i ne + C h l o r o p r a c a i n e +

t e t r ac o i ne te t r ac a i ne te t r ac a i ne te t r ac a i ne

Brachial plexus

Axillary

141

1

5

Supraclavicular

1 333 3 3

Sciatic

and

femoral

nerves,

with

o r

512

4

1 986 4 12

without lateral femoral cutaneous

nerve

and obturator nerve


3/7

Local Anesthetic Toxici ty. ..Moore,

et

a1

Chloroprocaine, lidocaine, or mepivacaine

plus tetracaine were the principal com-

pounds employed. Prilocaine and propoxy-

caine were used in only 85 cases before

1966; because of the insignificant number,

these will not be considered further. Lido-

caine or chloroprocaine plus tetracaine were

the principal agents compounded through

1966. Lidocaine plus tetracaine was used in

only one peripheral nerve block during that

time; therefore this compound for such use

is given no further consideration. Prior to

1967 chloroprocaine was compounded with

tetracaine for 638 epidural blocks but for

only 12 peripheral nerve blocks, and the

peripheral nerve blocks will not

be

consid-

ered further. The use of chloroprocaine was

discontinued when the pharmaceutical com-

pany that originally developed the agent

stopped producing it.

After 1966, mepivacaine plus tetracaine

was used almost exclusively because the

time of onset, spread, penetration, and es-

tablishment of surgical anesthesia of mepi-

vacaine were comparable to those of lido-

caine, and the commercial packaging of the

agent was better suited for our method of

compounding.

DOSAGE. Solutions to be compounded

were mixed immediately before injection.

We incorporated epinephrine in all com-

pounded solutions. For epidural and caudal

block through

1966,

the epinephrine con-

centration varied depending on the volume

of the local anesthetic solution injected,

that is, where

12

to

25

ml. was administered

the concentration was 1:125,000 and when

26 to 50 ml. was used, 1:200,000.From 1967

on the maximum concentration of epineph-

581

rine was 1:200,000, hat

is,

0.1 ml. 0.1mg.)

of epinephrine

1:lOOO

in

20

ml. of solution,

and the maximum total milligram

dose

of

epinephrine for any regional block technic

was 0.25 mg. Even when regional block

technics requiring more than

50

ml. of the

local anesthetic solution were executed

(block of the sciatic, femoral, lateral fe-

moral cutaneous, and obturator nerves,

which require 100 ml.) 0.25 mg. of epineph-

rine was not exceeded since this amount

does not usually cause a severe epinephrine

reaction or initiate arrhythmias even in pa-

tients with cardiac disease. Therefore, in

peripheral nerve blocks requiring in excess

of 50 ml. of the local anesthetic solution the

concentration is less than 1:200,000 e.g.,

when 100 ml. is used the concentration of

epinephrine is

1

:400 000.

For lumbar epidural block used primar-

ily for intra-abdominal surgery, 2 mg. of

tetracaine was added to each milliliter of

either 1.5 percent lidocaine, 1.5 percent me-

pivacaine, or 2 percent chloroprocaine, and

a maximum of 20 ml. was injected into the

lumbar epidural space.4 In the majority of

cases the dose was 18 ml. or less.

For caudal block used primarily for

perineal surgery, 2 mg. of tetracaine was

added to each milliliter of

1.5

percent lido-

mine or 1.5 percent mepivacaine up to a

total volume of 25 to 30 ml. When between

31 and 50 ml. was used, as for vaginal hys-

terectomy, we selected a solution of

1

per-

cent lidocaine or 1 percent mepivacaine,

rather than 1.5 percent, to avoid exceeding

our approximate maximum dose of lidocaine

DANIEL . MOORE,M.D., is Clinical Associate Pro-

fessor of Anesthesiology at the University of Washington,

Seattle, and Director, Department of Anesthesiology, the

Mason Clinic and the Virginia Mason Hospital, Seattle,

Washington.

Dr. Moore is one of the most active mem-

bers of the specialty, holding honorary membership in

many organizations and having written four books and

over eighty papers. His principal interests have been

local anesthetic agents and regional technics.

In

1944

he

graduated from Northwestern University Medical School,

Evanston, Illinois, and was an intern and a Resident in Anesthesiology at

Wesley Memorial Hospital, Chicago. He is a Past President 1959) of the

American Society of Anesthesiologists.


4/7

582

ANESTHESIAN D ANALGESIA..Current Researches VOL.

51,

No. 4, JULY-AUGUST972

or mepivacaine for a single-dose technic,

and we added 2 mg. of tetracaine to each

milliliter of lidocaine or mepivacaine.

For peripheral nerve block for extremity

procedures, with a volume of 50 ml. or less

of injected solution, 2 mg. of tetracaine was

added to each milliliter of

1

percent mepiva-

caine.

If

over 50 ml.

(60-100

ml.) were to

be used, tetracaine (1 mg./lb. of body

weight, not to exceed 200 mg. or a final tet-

racaine concentration of 0.25 percent) was

added to the 0.5 percent mepivacaine solu-

tion. The weaker solution of mepivacaine

was selected when volumes necessary for

the block were more than 50 ml., to avoid

exceeding our approximate maximum dose

of this drug.

OF SURGICALNESTHESIA. or epidural

and caudal block compounded solutions had

(1) onset within 5 to 8 minutes; (2) surgi-

cal anesthesia within 12 to 25 minutes; and

3)

duration of from 2% to 2y4 hours. In

caudal block, solutions containing 1.5 per-

cent lidocaine or 1.5 percent mepivacaine,

as compared with 1 percent, usually estab-

lished surgical anesthesia earlier, but dura-

tion of anesthesia was approximately the

same.

For

peripheral nerve block

onset and es-

tablishment of surgical anesthesia with com-

pounded solutions were similar to those for

caudal and epidural block, but duration

was significantly longer-from 4 to 51/2

hours, and occasionally longer.

COMPLICATIONS.-

o local tissue toxicity

resulted from the use of compounded solu-

tions in any block procedure.

Following

lumbar epidural block

6 pa-

tients exhibited systemic toxic reactions.

After receiving lidocaine plus tetracaine, 3

patients convulsed and

1

ost consciousness,

probably from the cerebral effects of the

lidocaine. Following mepivacaine plus tet-

racaine, one convulsed and one remained

conscious but was disoriented. All recovered

uneventfully after treatment with oxygen

by bag and mask.

One patient, in whom a lumbar epidural

block with 18 ml. of a 1.5 percent solution

of lidocaine (270 mg.) and 36 mg. of tetra-

caine with 1 125,000 epinephrine was ad-

ministered for an appendectomy, experi-

enced permanent bilateral weakness of the

quadriceps muscle.

Following

caudal block 4

patients ex-

hibited systemic toxic reactions progressing

O N S E T ESTABLISHMENT AND

DURATION

to convulsions-2 had received a solution

of lidocaine plus tetracaine and the other 2,

a solution of mepivacaine plus tetracaine.

All were treated with oxygen by bag and

mask and all recovered.

In 1 patient with cancer of the rectum,

a caudal block for biopsy, using

20

ml. of

1.5 percent lidocaine 300mg.) and 40 mg.

of tetracaine, with epinephrine

1

125,000,

was followed by a bilateral paralysis which

gradually extended from the 10th to the

6th thoracic dermatome over a 3-week pe-

riod. This complication resulted

was diagnosed as an ascending

tery syndrome.

No complications followed

nerve block.

from what

spinal ar-

peripheral

DISCUSSION

O P T I M A L

MILLIGRAMOSAGEF

TETRA-

CAINE AS

RELATED

O CHLOROPROCAINE

LIDOCAINE

OR

MEPIVACAINE.

or com-

pounding local anesthetic agents, our ap-

proximate maximum doses are

(1) 1000

mg.

of chloroprocaine; (2) 500 mg. of lidocaine

or mepivacaine; and

3)

1 mg./lb. (body

weight) of tetracaine, not to exceed 200

mg.4 These are the same maximum doses

which we would employ

if

the agents were

not compounded.

For

epidural block

we inject no more

than 20 ml. of the local anesthetic solution

into the epidural space, whether or not the

solution is ~ompounded.~hen the amounts

used for skin wheal, local infiltration, and

test dose are added to this, however, the

total of the compounded solution may reach

26 ml. Thus, maxima may reach 390 mg.

of lidocaine,

390

mg. of mepivacaine, 520

mg. of chloroprocaine, and 52 mg. of tetra-

caine, but the total milligram dosage of

these agents is markedly less than our maxi-

mum dose for any one agent used alone.

For caudal block when a volume of solu-

tion of 30ml. or less is to be used, including

skin wheal, local infiltration, test dose, and

amount injected into caudal canal, the ratio

of compounding

is

2 mg. of tetracaine to

each milliliter of 1.5 percent lidocaine or 1.5

percent mepivacaine. We seldom inject

more than

30

ml., equaling a maximum of

450 mg. of lidocaine or mepivacaine and

60

mg. of tetracaine. I n the unusual case, when

31 to 50 ml. of solution (including skin

wheal, local infiltration, test dose, and

amount injected into the caudal canal) is

used and 2 mg. of tetracaine

is

added to


5/7

Local

Anesthetic Toxicity. . Moore, t

a1

583

each milliliter of 1 percent lidocaine or 1

percent mepivacaine, the maximum amount

injected

is

310 to 500 mg. of lidocaine or

of mepivacaine and 62 to 100 mg. of tetra-

caine. Therefore, in caudal block, the total

dosage of the compounded local anesthetic

agents is usually less than our approximate

maximum dosage of either agent injected

alone.

For peripheral nerve block as concentra-

tions of lidocaine or mepivacaine in excess

of 1 percent may produce neuritis, we do

not routinely employ them for this technic.4

For brachial plexus block, we use 50 ml.

of solution; for sciatic and femoral nerve

blocks, 50 ml.; and for sciatic and femoral

nerve blocks with either lateral femoral cu-

taneous nerve block or obturator block, or

both,

70

to 100 ml.4

When volumes of 50 ml. are employed,

2 mg. of tetracaine is added to each milli-

liter of

1

percent mepivacaine,

500

mg. of

mepivacaine and 100 mg. of tetracaine being

administered. When 70 to 100 ml. of solu-

tion is injected, tetracaine

(1

mg./lb., not

to exceed 200 mg.) is added to each milli-

liter of 0.5 percent mepivacaine, 350 to 500

mg. of mepivacaine and varying amounts

of tetracaine, depending on body weight,

being injected. Therefore, in peripheral

nerve blocks, the maximal dose of either

agent is not exceeded.

The reasons for such ratios in compound-

ing in order to produce the long duration of

action of tetracaine are not clearly under-

stood. However, this phenomenon has been

observed in man by us and in dogs by De-

falque and Stoelting.9

COMPARISON OF ONSET, ESTABLISHMENT

OF SURGICAL ANESTHESIAND DURATION

OF SURGICAL A N ES THES IAITH LIDOCAINE

A N D

MEPIVACAINE.-

When only lidocaine,

mepivacaine, or chloroprocaine

is

used for

epidural or caudal block onset occurs in 5

to 8 minutes, surgical anesthesia is estab-

lished within 12 to 25 minutes, and duration

of action is from 1 to 1 hours, when such

solutions contain epinephrine. When tetra-

caine is added, onset and establishment of

surgical anesthesia are not altered, but

duration of action is extended to 21/4 to 2%

hours.

For peripheral nerve

block,

when only

lidocaine or mepivacaine with epinephrine

is employed, onset

is

within 5 to 8 minutes,

surgical anesthesia resulting in 12 to 25

minutes (depending on accuracy of place-

ment of the local anesthetic solution), and

anesthesia lasts for 1 o 3 hours. The ad-

dition of tetracaine does not alter the time

of onset or establishment of surgical anes-

thesia, but duration

of

anesthesia is length-

ened to

4

to 59$ hours and occasionally

longer. For some unexplained reason, tetra-

caine alone, used for peripheral nerve block,

gives a duration of 6 to 9 hours or longer.

ADVANTAGESF

COMPOUNDING. Most

anesthesiologists prefer single-dose to con-

tinuous technics because (1) they are tech-

nically less difficult and time-consuming;

(2) the incidence of complications is less

-for example, broken plastic tubing; and

(3) the incidence of unsatisfactory anesthe-

sia is less. For most surgical procedures,

single-dose regional block requires the use

of a local anesthetic agent with a prolonged

duration. While the commonly employed

agents, such as chloroprocaine, lidocaine, or

mepivacaine, do have excellent diffusion

and penetrability as well as rapid onset and

rapid establishment of surgical anesthesia,

they do not produce prolonged sensory and

motor blockade. Therefore, they are not

satisfactory agents for single-dose technics

in the following circumstances: (1) teach-

ing of regional block, which may require 30

to 45 minutes prior to preparation and drap-

ing of the patient for surgery; (2) epidural

or caudal block, where the time needed for

establishment of surgical anesthesia and

for the surgical or obstetric procedure ex-

ceeds the duration of action of these agents;

(3) peripheral nerve block for surgical pro-

cedures requiring anesthesia in excess of 3

hours; or 4 ) prolonged pain relief, either

during the postoperative period or following

diagnostic and therapeutic blocks.

On the other hand, although tetracaine in

concentrations of 0.1, 0.15, or 0.25 percent

for single-dose peripheral nerve block pro-

vides

a

duration of anesthesia of 6 to

9

hours, or even 10 to 14 hours when the solu-

tion contains epinephrine, many anesthesi-

ologists do not use tetracaine because (1)

its onset time

is 5

to 10 minutes; (2) surgi-

cal anesthesia may not be established for 15

to 40 minutes;

(3)

diffusibility

is

limited,

requiring marked accuracy of placement on

or near the nerves; and 4) it has been

(falsely) accused of being too toXi~.4,10J1

Even if the time of onset and establish-

ment of maximum anesthesia were as rapid

with 0.1, 0.15, or 0.25 percent tetracaine as

with 1.5 percent lidocaine or 1.5 percent

mepivacaine, we would not

us

these con-

centrations of tetracaine for single-dose


6/7

584

ANESTHESIA

ND

ANALGESIA.

Current Researches VOL.

51,

No

4, JULY-AUGUST

972

caudal or epidural block, as the resulting

sensory and motor anesthesia

is

more con-

sistently predictable with lidocaine or me-

pivacaine.

COMPLICATIONS. ocal toxicity from

compounded solutions-for example, slough

of tissue-d id not occur in our experience or

in that of other investigators.'-3 We ob-

served two unexplained neurologic compli-

cations following the use of compounded

solutions-one after caudal block and the

other after epidural block. This incidence is

not markedly different from that of neuro-

logic sequelae following epidural block re-

ported by Bonica and associates' 1:3637

patients), by .Lund3 2:

10,OOO

patients),

and by Hellmannl2 2:26,127patients). In

our cases, the epinephrine content may have

been too great, but this is debatable. Since

1966,

by maintaining the optimal maximum

epinephrine concentration of 1:200,000 for

all regional nerve blocks, no neurologic

se

quelae or alteration in duration of anesthe-

sia has resulted.

We observed 10 systemic toxic reactions

(eight of which progressed to convulsions)

following injection of compounded solutions

into the epidural space via a lumbar inter-

space or the sacral hiatus. In these cases,

routine tests were made to avoid intravas-

cular or subarachnoid injection of the dose

of the drug calculated to produce the de-

sired anesthesia. The tests, aspiration for

blood or spinal fluid and injection of 3 to 5

ml. of the local anesthetic solution, followed

by observation of the patient for 5 minutes

to detect either changes in sensorium or

onset of anesthesia, were in all cases nega-

tive.

Our incidence of systemic toxic reactions

progressing to convulsions does not differ

significantly from that reported by other

authors. Bonica's group' reported general-

ized systemic toxic reactions following

epi-

dural blocks in 116 of 3637 patients, with

8 convulsing, and LundS in 44 of 10,OOO

patients, with 11 convulsing. Hellmannlz

did not report the number of generalized

systemic reactions, but 17 of his 26,127 pa-

tients convulsed.

APPLICABILITYF EXTRAPOLATINGRE-

SULTS

FROM

ANIMALS

O

H u M A N s . ~ ~ ~ ~ ~

compounding of chloroprocaine, lidocaine,

mepivacaine, prilocaine, or procaine with

one another or with tetracaine was found to

increase the severity of systemic toxic reac-

tions and the incidence of death in certain

strains of white rats and mice and in dogs,

use of these compounds in humans was

pos-

tulated to be dangerou~.~-Towever, results

of such animal experiments, especially with

ester-type agents, cannot properly be extra-

polated to humans, as acute toxicity studies

in animals involve rapid administration of

drug until death, high brain levels being

produced within such a short time that

ca-

tabolism of the agent is negligible. In con-

trast, clinical tolerance involves the kinetics

of drug absorption, distribution, and elimi-

nation.

Furthermore, the animals used in these

studies catabolize ester derivatives quite

slowly,13-16 while humans metabolize them

rapidly.13~14~16 sing gas chromatography,

we could detect no tetracaine in the blood of

patients 2 to 30 minutes after administering

150 mg. for bilateral intercostal nerve

blocks.

The assay for tetracaine can determine 0.1

mcg./ml. of the drug when added to human

blood in vitro, and significantly less than

this can be detected. The assay

is

similar

to

that

for anilide derivatives, except that

arsenite solution is added and the blood is

frozen pending analysis, to prevent hydroly-

sis of tetracaine during and after sampl-

ing. OtherslcJ* have also found difficulty

in measuring tetracaine in vivo in humans

but have confirmed that it can be measured

in vitro.

Therefore, since lidocaine or mepivacaine

injected in humans for caudal, epidural, and

peripheral nerve blocks does not reach peak

blood levels for 10 to 30 minutes, as deter-

mined by gas chromatography, and since

tetracaine cannot be measured after normal

clinical doses, presumably because it is

rapidly metabolized, we can hypothesize

that high levels of the drugs do not coincide

and that generalized systemic toxic reac-

tions are not likely to occur in humans

as

a result of compounding an anilide with an

ester. This assumes, of course, that metabo-

lites of tetracaine are not significantly toxic.

At present, no methods are available for

determining precisely the levels

of

esterized

local anesthetic derivatives in human blood

following normal clinical doses. Such meth-

ods

should be sought,

so

that uptake

and

elimination of the ester derivatives can be

determined in man.


7/7

Local Anesthetic Toxicity. . .Moore, et a1

585

CONCLUSIONS

In a retrospective study of the records of

over 10 000patients given local anesthetic

agents for caudal, epidural, brachial plexus,

or peripheral nerve blocks, compounding of

certain parenteral agents was found to give

more satisfactory results than use of the

agents singly.

The primary advantage of compounding

is that it permits the use of single-dose tech-

nics by taking advantage of the outstanding

qualities of each local anesthetic agent, that

is, the rapid establishment of surgical anes-

thesia of chloroprocaine, lidocaine or mepi-

vacaine, and the prolonged duration of tet-

racaine.

Compounded solutions permit single-dose

technics for epidural or caudal block in

many instances where a continuous technic

would be mandatory with a single agent.

Other advantages are also described.

Compounding as detailed herein is a safe

technic in man. Data indicating systemic

toxic reactions and deaths in animal experi-

ments with such compounded local anes-

thetic solutions do not appear subject to

extrapolation for clinical purposes.

Finally, when anesthesia

is

unsatisfac-

tory following

a

regional block performed

with the approximate maximum dose of

either an anilide or an ester derivative and

it is decided to repeat the block, a local

anesthetic agent of an alternate chemical

derivation

should

be used. For example, if

an anilide derivative

is

injected initially

and the resulting anesthesia is unsatsfac-

tory, reinjection should be done with an

ester derivative.

Generic and T rade Names

of Drugs

Chloroprocaine-Nesacaine

Dibucaine-Nupercaine

Epinephrine-Adrenalin

Hexylcaine-Cyclaine

Lidocaine-X y locaine

Mepivacaine-Carbocaine

Prilocaine-Citanest

Procaine-Novocain

Propoxycaine-Blockain

Tetracaine-Pontocaine

REFERENCES

1. Crawford

OB

Chester RV: Caudal anesthe-

sia in obstetrics: a combined procaine-pontocaine

single injection technic. Anesthesiology

10: 73-478,

1949

2.

Bonica JJ, Backup PH, Anderson CE, et al:

Peridural block: analysis of

3,637

cases and

a

re-

view. Anesthesiology

18: 23-784, 957

3.

Lund PC: Peridural anesthesia. A review

of

10,OOO

administrations. Acta Anaesth Scand

6:143-

159, 1962

4.

Moore DC: Regional Block. Fourth edition.

Springfield, Illinois, Charles

C

Thomas, Publisher,

1961,

pp

16, 18, 410

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