Anaesthesia for Caesarean Section - Part 2

General anaesthesia
Propofol and thiobarbiturates have the advantage of rapid onset and short duration with minimal residual foetal depression (1), but can cause cardiovascular depression and decreased uterine blood flow. Transient apnoea is common following administration and may result in foetal hypoxia and academia if the mother is not pre- oxygenated, rapidly intubated, and ventilated. Propofol is associated with better puppy vigour than barbiturates(2). Maintenance of anaesthesia with propofol is not yet recommended in humans because of lower neurological and adaptive capacity scores in the offspring compared to thiopental (3). However, when compared to isoflurane, total intravenous anaesthesia with propofol in pregnant ewes resulted in superior haemodynamics (4).

The dose of all induction agents and therefore their side-effects can be reduced by first giving intravenous lidocaine (0.25-0.5 mg/kg), diazepam (0.1-0.4 mg/kg), or midazolam (0.1-0.3 mg/kg).
Ketamine (4-6 mg/kg i.v.) combined with diazepam (0.1-0.4 mg/kg i.v.) or midazolam (0.1-0.3 mg/kg i.v.) is an alternative induction technique that provides good cardiovascular support. Ketamine combinations do not affect overall puppy survival but have necessitated more vigorous resuscitative efforts (2).

In compromised dams, etomidate (2 mg/kg i.v.) is recommended because of its minimal cardiovascular effects. When used alone etomidate may cause gagging or retching but when used in combination with a benzodiazepine, these side-effects are reduced.