1)     RECOMMENDATIONS

a)      General Approach

i)        Minimize anesthetics and surgical time

ii)       Hydrate and pre-oxygenate (if nonstressful)

iii)     Do not over-ventilate

(1)   Monitor ETCO2 or blood gases

(2)   PaCO₂ less than 35 will decrease uterine blood flow (UBF)

iv)     MAC is significantly decreased

(1)   Isoflurane MAC decreases 40%

(2)   Halothane MAC decreases 25%

(3)   Sevoflurane?

b)      Pre-anesthetic Medications

i)        Most anesthesia and reproductive specialist use minimal preanesthetic medications if any at all. If, however, maternal stress is excessive low doses of acepromazine may be a consideration assuming the bitch is not hypotensive

(1)   Acepromazine

(a)    The routine use of acepromazine is not recommended

(i)      Avoid if patient is hypotensive

(b)   If needed, stay at the very lowest end of the dose range

(i)      0.005 to 0.02 mg/kg IV, IM

(2)   Opioids

(a)    Buprenorphine is used routinely by some reproductive specialists

(i)      The partial mu agonist, buprenorphine, is generally free of significant sedative and respiratory depressant properties making it well suited as a preemptive analgesic for C-section patients, particularly cats

(ii)     0.020 to 0.030 mg/kg IV (IM if IV access not immediately available or TM (transmucosal) in cats) given 20 to 30 minutes prior to induction

(b)    Many will delay systemic opioid administration in canine c-sections until the puppy have been delivered then immediately administering a mu agonist via the IV route

(i)      Fentanyl, hydromorphone, methadone, and morphine (slowly IV) are all good considerations. Buprenorphine is less ideal at this point in the procedure as it has a significantly delayed onset even when given IV

(ii)      When systemic opioid administration is delayed, an incisional line block and an epidural opioid/local anesthetic combination are highly recommended (assuming the epidural can be placed in a timely fashion)

ii)       Anticholinergics

(1)   The routine use of an anticholinergic is avoided unless the status of the bitch dictates their use

(2)   In an emergency situation atropine is the anticholinergic of choice

(3)   In nonemergent situations the choice of anticholinergics is subject to debate with no clear best choice

(4)    Glycopyrrolate is a large protein that does not cross the placenta limiting its effects to the bitch only

(5)   Atropine will cross the placenta effecting both bitch and pups

iii)     Epidurals

(1)   If they can be performed quickly and efficiently, a morphine/local anesthetic epidural can be an effective tool

(2) The bitch has increased collateral blood flow which may distend the epidural veins decreasing local anesthetic requirements

c)      Induction

i)         Propofol

(1)   2.0 to 6 mg/kg (1.0 to 3.0 mg/lb) IV titrated to effect over 30 to 90 seconds

ii)      Alfaxalone   

(1)   2.0 to 3 mg/kg (1.0 to 1.5 mg/lb) IV titrated to effect over 30 to 90 second

iii)      Ketamine/diazepam, ketamine/midazolam, and thiopental are NOT recommended as all are associated with reduced puppy vigor at birth compared to propofol and alfaxalone

d)      Maintenance

i)         Isoflurane/Sevoflurane         

(1)   Remember MAC decreases significantly during pregnancy

e)      Support

i)         IV fluid support is a basic requirement

ii)       Opioids are an attractive postoperative analgesic class for nursing bitches and queens¹

(1)   Morphine’s hydrophilic nature minimizes its passage into the milk

(3)   Buprenorphine transmucosally is attractive for feline management

iii)     A single NSAID dose postoperatively to normotensive bitches should improve patient comfort and is not thought to be of detriment to the neonates¹

2)     PRECAUTIONS

a)      Pre-anesthetic Medications

i)        Limit preanesthetic medications associated with a reduction in puppy vigor

ii)       Avoid mu agonists, alpha-2 agonists, and benzodiazepines

iii)   If maternal stress is excessive consider buprenorphine and, if bitch is not hypotensive, very low dose acepromazine

b)      Induction

i)        Dose propofol to effect to minimize respiratory depression and hypotensive potential

c)      Maintenance

i)         MAC is lowered significantly during pregnancy

d)      Support

i)        Insure adequate hydration and oxygenation

ii)       Bradycardia in the pups is a poor prognostic indicator

(1)   Intubate and ventilate ASAP

(2)   Doxapram use is not recommended. 1 drop of dopram can be placed sublingually to help stimulate respiration if, and only if, intubation is not possible

(a)    Doxapram is a general stimulant that not only increases ventilation drive, it also increase cerebral oxygen demand, generally without a net gain in tissue oxygenation

(i)      Ventilating the patient is always preferred to doxapram use

(3)   1 drop naloxone can be placed sublingually to reverse narcotic bradycardic or respiratory depressant effects if a mu agonist is used

iii)     Avoid extended NSAID use in the postoperative period if nursing

iv)     Observe the nursing pups and kittens for opioid induced depression using naloxone for control