Anesthesia for Non-Obstetric Surgery Most common reasons for surgery: – Appendicitis – Cholecystitis – Trauma – Ovarian torsion

Anesthesia for Non-Obstetric Surgery Maternal safety is related to: – Physiological adaptations associated with pregnancy Fetal safety is related to: – Teratogenicity – Avoidance of fetal asphyxia – Avoidance of preterm labor

Anesthesia in the 1 st Trimester Altered cardiac, haemodynamic, respiratory, metabolic and pharmacological parameters Increase minute ventilation, O2 consumption and dec. reserve More difficult laryngoscopy and intubation Marked reduction of plasma cholinesterase Higher aspiration risk

Pharmacologic considerations 20-30% reduction in MAC Increased sensitivity to local anesthetics More extensive spread of local anesthetics given intrathecally 25% reduction of plasma cholinesterase levels Most drugs can easily cross placental barrier No proven teratogen among anesthetics

Examples Vecuronium at 0.2mg/kg – faster onset and longer duration Rocuronium at 0.6 mg/kg – unchanged onset but longer duration Atracurium – faster onset and shorter duration

Preoperative management Anxiolytics Aspiration pneumonitis prophylaxis – H2 – receptor antagonist – Dopamine antagonist

Anesthesia Technique Regional/Local Anesthesia Reduced exposure of fetus to potential teratogens Decreased maternal respiratory complications (failed intubation, aspiration, etc) General Anesthesia Ensures patient comfort Nitrous oxide without concomitant administration of a halogenated anesthetic is reported to reduce uterine blood flow

Anesthesia Technique Regional or local anesthesia should be employed whenever possible – Spinal is preferred over epidural due to: decreased drug exposure to fetus not associated with unintentional intravascular injections or potentially large intrathecal doses of local anesthetic

Intraoperative management 15 0 left lateral tilt (esp 2 nd trimester onwards) Slow change in positioning If GA, utilize rapid sequence induction: – Initiate only after abdomen has been prepped – 5 minutes meticulous denitrogenation – Apply cricoid pressure – Use drugs with well-known history of safety – No positive pressure ventilation

Monitor Maternal oxygenation Maternal BP Maternal PaCO2 ABG in some cases Uterine blood flow Fetal heart tone (18 wk onward)

Dosages Induction agents: – Thiopental 4mg/kg – Propofol 2mg/kg – Ketamine 1mg/kg – Etomidate 0.3mg/kg – Succinylcholine 1-1.5mg/kg Inhalants: – 50% N2O/50% O2 and 0.5 to 1.0 MAC desflurane, sevoflurane or isoflurane

Spinal – reduce by 25% segmental dose requirement (not seen in 1 st trimester)