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ANETESIA EN CESÁREAS Y RESUCITACIÓN NEONATAL

Sheilah Robertson Senior Medical Director Lap of Love Veterinary Hospice

Discussion points

Our goals

Physiology of pregnancy

Risk factors – dam and offspring

Morbidity and mortality

Anesthetic protocols

Neonatal resuscitation

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Goals Physiologic Changes

HEMATOLOGIC CARDIOVASCULAR RESPIRATORY

NEUROLOGICAL GASTROINTESTINAL

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Hematologic Changes

Allard RL et al 1989

Dilutional or “relative” anemia of pregnancy

Correlates with number of fetuses

Normal PCV may = dehydration

PCV %Gestation

week 1

Gestation

week 8

Lactation

week 8

MEAN 50 38.2 44.1

Physiologic changes

Increased:

Metabolic rate

Oxygen consumption

Cardiovascular Changes

IncreasedCardiac output ~30-50%HR and SVUterus receives 25% of cardiac output

DecreasedVascular resistance

Blood pressure

Maintained

Aortocaval Compression Syndrome

Dorsal recumbency

Aortocaval compression by fetus

Decreased cardiac output

Decreased uterine perfusion

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Aortocaval Compression Aortocaval Compression Syndrome

Probst and Webb 1983, Probst et al 1987 Giant Breeds

?

Positioning the patient Respiratory Changes

INCREASED

Respiratory rate

Tidal volume

Alveolar ventilation

Metabolic rate

Oxygen consumption

DECREASED

PaCO2

Normal 40-45 mmHg

Pregnancy 26-32 mmHg

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Uterine Blood Flow

PaCO2 < 22 mmHg decreases uterine

blood flow and oxygen delivery

Respiratory Changes

Clinical Implications

Risks:

Desaturation

Hypoxemia

Changes transmitted to fetus

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Pre-oxygenation Gastrointestinal Changes

Decreased lower esophageal sphincter tone

Gastric compression by uterus

Increased gastric acid

Prolonged gastric emptying

Clinical implications - humans

Mendelssohn's syndrome

Outcome is pH and volume related

Risks

Regurgitation and aspiration

Aspiration in 50% of C-section deaths

Moon PF et al 1998

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Preventing nausea and vomiting

5HT receptor antagonist NK-1 receptor antagonist

Breed incidence

Brachycephalic United Kingdom

Boston terrier

Bulldog

French Bulldog

> 80%

Evans & Adams 2010

Breed incidence - dystociaDOLICHOCEPHALIC BRACHYCEPHALIC MESOCEPHALIC

10% 7.55% 2.3%

75% require surgery

medical

intervention

often successful

Maternal mortality - dogs

DATE OF STUDY MORTALITY

1939-1975

Small sample sizes0-70%

1994-1997

Moon et al 808 bitches1%

2014 Metcalfe et al

2014 Lever and Ayers

0/74

0/480

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Puppy mortality

Emergency procedure 13%

Elective procedure 4%

Moon et al

Pre-operative preparation

Physical examination

Blood work

Place an IV catheter

Fluids

Clip surgical site

Anesthetic drugsPaCO2

SYSTEMICVASCULAR

RESISTANCE

SYSTEMIC BLOODPRESSURE

UTERINE BLOOD

FLOW

NO FETAL AUTOREGULATION

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PaCO2

SYSTEMICVASCULAR

RESISTANCE

SYSTEMIC BLOODPRESSURE

UTERINE BLOOD

FLOWPAINFEAR

EXCITEMENT

HYPERVENTILATION

SEDATIONANESTHESIA

HYPOVOLEMIA

Drug dosing

Weight gain up to 40%

Pre-pregnancy weight

Induction drugs to effect

Premedication

Temperament

Physical status

Premedication

Calming

Smoother induction and recovery

Anesthetic sparing

Preventive (preemptive) analgesia

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A question for you

Which of these drugs will have the most detrimental effect on uterine blood flow?

A. Meperidina

B. Fentanilo

C. Dexmedetomida

D. Acepromacine

E. Morfina

Sedatives and tranquillizers

ACEPROMAZINE

Avoid if dehydrated Xylazine and puppy mortality

Vasoconstriction

Decreased cardiac output

ALPHA2-AGONISTS

Opioids

PROS

Preemptive analgesia

Anesthetic sparing

Reversible

CONS

Vomiting

Neonatal depression

Mask Induction

Higher mortality

Aspiration

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Induction drugs

Ketamina

Propofol

Etomidato

Thiopental Sodico

Alfaxalone

Effects of four anaesthetic protocols on the

neurological and cardiorespiratory variables

of puppies born by caesarean sectionLuna et al Vet Rec 2004

EPIDURAL PROPOFOL THIOPENTONE KETAMINE MIDAZOLAM

1 2 3 4

Ketamine (+ benzodiazepine)

Decreased puppy vigor*

Neurologic depression†

Did not affect mortality

*Moon-Massat & Erb 2002†Luna et al 2004

3 StudiesNo maternal deaths

No difference in puppy survival

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Puppy Apgar scores alfaxalone versus propofol

Doebeli et al 2013

Dr Virginia Apgar

Puppy Vigor - Apgar scoring

Parameter 0 1 2

Heart rate < 180 bpm 180-220 bpm > 220 bpm

Respiration No crying,

RR< 6

Mild crying,

RR 6-15

Crying,

RR > 15

Response to

toe pinch

No response Weak

retraction,

vocalization

Vigorous

retraction,

vocalizing

Movement Flaccid Some flexion Active

motion

Mucus

membranes

Cyanotic Pale Pink

Veronesi et al 2009

Maximum score = 10

10

8

6

4

2

0

5 min 15 min 60 min

Alfaxalone Propofol

P < 0.05

AP

GA

R S

CO

RE

Alfaxalone TIVA? alfaxalone/isoflurane?

Ruiz et al Vet 2015

INDUCTION - ALFAXALONE

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TIME - MINUTES ALFAXALONE ISOFLURANE

RECOVERY TIME 46 22

EXTUBATION 17 6

HEAD LIFT 26 6

STERNAL 25 6

SUCKLING 29 15

Epidural anesthesia

Theoretically “best for the pups or kittens”

Cochrane review (humans)

Neuraxial verses general anesthesia

No difference in APGAR scores

Epidural anesthesia

Unprotected airway

Size of the epidural space

Hypotension

May not be tolerated

Takes longer

Line block – Lidocaina 2%

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Monitoring during surgery Hypotension

Decrease vaporizer setting

Crystalloids

Colloids

Hypotension

FIRST DRUG CHOICE

Ephedrine 0.04 - 0.1 mg/kg

Alpha and beta effects

Preserves uterine blood flow

Inotropes

Dopamine

Dobutamine

Infusion rates

≤5 microg/kg/minute

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Body Temperature

High priority

Patient comfort post-operatively

Wound infection

Bleeding

Bradycardia

Delayed recovery

Body Temperature

Neonatal hypothermia

Inhibits resuscitative efforts

Acidosis

Analgesia

Placental transfer of drugs

Transfer into milk

Limited data for dogs and cats

Analgesia

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Post-operative epidural: morphine

Check lists

C-SECTIONS MASK AVAILABLE FOR PRE-OXYGENATION

SURGEONS READY BEFORE INDUCTION

HOW MANY PUPPIES OR KITTENS ARE EXPECTED?

CRYSTALLOID FLUIDS STARTED

COLLOIDS AVAILABLE

DOSE OR INFUSION RATE OF VASOPRESSORS

CALCULATED AND READY FOR USE

NEONATAL RESUSCITATION EQUIPMENT AND DRUGS

SET UP

IS THE NEONATAL RESUSCITATION TEAM READY?

ANETESIA EN CESÁREAS

QUESTIONS?

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RESUCITACIÓN NEONATAL RESUCITACIÓN NEONATAL

Transition from intrauterine to extra-uterine life

FLUID AIR

Human data

10% of newborns require some assistance to begin breathing

“Successful resuscitation should prevent many of these deaths and improve the

outcome in surviving infants”

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Today’s evidence

International Liaison Committee on Resuscitation

Gather evidence based data

Recommendations

Neonatal Resuscitation

American Heart Association

Updated every 5 years

Human Data

Neonatal mortality

Vaginal birth 0.06%

C-Section 0.177%

MacDorman et al 2006, Birth

Puppy Mortality

At birth 2 hours

Natural birth 2.2% -

C-section 8% 13%

Moon et al 2001 Vet Clin N America

Neonatal Resuscitation

C-Sections

Vaginal delivery

New mothers

Rejected kittens and puppies

Debilitated dam

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C-section delivery

Puppy survival increased if:

Not an emergency procedure

Not a brachycephalic breed

Babies - Resuscitation yes or no?

Is the baby full term?

Is the amniotic fluid clear of meconium?

Breathing or crying?

Good muscle tone?

If the answer is YES, no resuscitation needed

Dry, keep warm, observe

Babies – Resuscitation yes or no?

If the answer to any question is NOA Provide warmth

Clear airway

Dry

Stimulate

B Ventilation, oxygen

C Chest compressions

D Drugs / volume expansion

Veterinary Resuscitative Efforts

Heat source 41%

Doxapram 34%

Oxygen 15%

Naloxone 3%

Atropine 2%

Epinephrine 2%

Glucose 1%

Intubation 1%

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Vital signs – newborn puppies

Heart rate

Beats/min

Respiratory

rate

Breaths/min

To rangeoCoF

200 - 250 25 - 3534.4 - 36.0

94.0 - 96.8

First Breath

Overcomes collapsed lungs

Mean negative pleural pressure:

50 to 100 cmH2O

Be Prepared

FORCED WARM

AIR OR A

HAIRDRYER

INTUBATION SUPPLIES

DRUGS

BULB SYRINGES

OXYGEN MASKS

Be Prepared

PREWARMED

TOWELS

MICROSYRINGES

Doppler

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Equipment for suction and oxygen administration

Bulb syringes

Face masks

Cotton tipped swabs

Timer

Be Prepared

Primary concerns at delivery

RAPID evaluation

Prevent hypothermia

Remove secretions

Assessment

Heart Rate

Breathing

Color?

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Color

Acrocyanosis

Blue color of paws

Normal at birth

Cold stress

Color

Central cyanosis

Face

Belly

Mucus membranes

Body Temperature

Pre-warming (15 minutes) and intraoperative warming of women for C-section

Decreased maternal shivering

Babies

Higher core temperatures

Less acidotic

Horn et al 2002, Anesth Analg

Body Temperature

Newborns lack hypothalamic control of body temperature

Hypothermia

Increases metabolic demands

Decreases response to resuscitative efforts

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Body Temperature

Lose heat easily and rapidly

Wet

Large SA / BW ratio

Little fat

Poorly developed shivering response

Non-shivering thermogenesis

Brown fat, high energy requirements

Temperature support 28.5-32.0oC

Neonatal respiratory distress syndrome

Common cause of neonatal death

First 48 hours of life

Treatment

Clear airway

Membranes

Mucus

Distl et al 2008 Neonatology of the dog

Use of (a) a syringe mount attached to a 1 ml syringe and (b) a

nasal aspirator to remove fluids from the nose of a neonatal

puppy during resuscitation.

Goericke-Pesch S, Wehrend A 2012

Practical, efficient, no bleeding

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Meconium staining

Suction if puppy or kitten is not vigorous

Suction devices

DeLee aspirator Suction tip catheters

Suction Oropharynx

Stimulation

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Swinging

NO

Head and neck injuries

Cerebral hemorrhage

Grundy et al Topical Review 2009

Stimulation

Neonates

Flicking soles of feet may stimulate respiration

Initiating respiration

Oxygen

Tactile stimulation

Continue to suction

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Initiate ventilation if……

No spontaneous respiration in 30 seconds

Central cyanosis

Ventilation by mask If mask is ineffective

Intubate

Suction trachea

Chest excursions?

Color? 2 mm

12-16 gauge IV catheters

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Positive Pressure Ventilation

20-25 cmH2O

Can increase to 30-40 cm H2O

Rate: 40-60 bpm

Success = increased in HR

Positive Pressure Ventilation

Once successful

10 -15 cm H2O

0.5 -1.0 second inspiratory times

Remove ETT, replace with mask

Continue with oxygen

“Jen Chung” CV 25

Acupuncture point

25g needle

Chest compressions

Compression-relaxation ratio

Let chest fully re-expand

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“Drugs are rarely indicated in resuscitation of newborns. Bradycardia is usually the result of

inadequate lung inflation and hypoxemia”*

*Neonatal Resuscitation Guidelines

Route of Administration

Umbilical vein

Dilute drug

Flush

Intraosseous Tramsmucosal

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Epinephrine 1:10,000 = 0.1 mg/ml

0.01 mg/kg

250 g puppy

0.0025 mg

0.025 mls

Naloxone

Only if dam received opioids

Slow heart rate

0.1 mg/kg

0.06 mls for a 250g pup

Atropine

Hypothermia and hypoxia cause bradycardia

Not vagally mediated

Doxapram

Controversial

Central stimulant

Won’t work if hypoxic

Rarely used in human neonates

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Glucose Supplementation

If dam is slow to recover

Unwilling to nurse

Oral dosing at 2-3 mls / kg of 10% dextrose

Lancet 2013

Corn syrup Post-Delivery

Observe closely

Keep warm

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Success!

Meet mum!

QUESTIONS