202410301432
Status:
Tags: Obstetrics
General anaesthesia for C section
indication
- speed i.e. Cat 1 CS
- C/I to SA
- patient refusal
GA still fasting than rapid sequence SA (taking ~8min)
aspiration risk
reduce risk by lowering acidity with non-particulate antacids
Na citrate lasting around 30min
?? H2 blocker or PPI AFTER intubation (to reduce risk for extubation)
Difficult airway
higher risk of difficult or failed intubation - 1:49 and 1:808 respectively, compared to non-pregnant patients
The physiologic changes of pregnancy affecting the airway and respiratory system include more vascular and edematous upper respiratory tract mucosa, with increased risk of tissue friability, bleeding and swelling with airway manipulation.
These changes may be exaggerated in the setting of preeclampsia, oxytocin and IV fluid administration and after Valsalva maneuvers during the 2nd stage of labor
After induction of anesthesia, oxygen desaturation with apnea is accelerated in parturients due to ↓ FRC and ↑ O2 consumption
cricoid pressure is traditionally applied with an initial force of 10 N and increasing to 30 N with loss of consciousness
Gentle positive pressure is now also recommended immediately preceding the first attempt of laryngoscopy to
- ↓ O2 desaturation
- estimate the likelihood of successful BMV should it be required
The risk of pulmonary aspiration is ↑ ∵
- progesterone-induced ↓ gastroesophageal sphincter tone
- delayed Gastric emptying in pregnancy
- a/w pain and opioid administration
Difference from other GA:
Prep & drape BEFORE induction: need good communication with patient
RSI
- ↓ aspiration risk
- ↓ time of fetal exposure to anaesthetic agents
Gentle mask ventilation with peak inspiratory pressure <20 cm H2O with or without cricoid pressure is considered to be safe to maintain oxygen saturation between intubation attempts if needed, while limiting the risk of gastric insufflation with gases
(OAA + DAS 2015 guideline)
(pearl: if some drugs can cross BBB → likely it can cross placenta)
incision w/i seconds of induction
→ leading to hypertension (could lead to Cx esp in PET patients)
Delivery:
Apgar at 1min usually lower ∵ we anaesthetise the baby as well
implication
- need another person e.g. paed to resuscitate the baby
- need to communicate with that personnel RE: drug given to mother
Drug dose:
trade off btwn mother VS baby
Prevention of awareness
- amnestic e.g. midazolam after delivery
- adv of sux ∵ mother can move if aware
- N2O ∵ ↓ MAC
- monitor
- end-tidal gas
- brain monitor
Although rapid placental transfer occurs with lipophilic induction agents and opioids are not routinely administered, alfentanil, remifentanil, sufentanil or fentanyl are advisable in cases of severe hypertension, cardiac disease, or neurologic compromise to blunt the hemodynamic response to laryngoscopy and intubation
High-dose volatile anesthetic agents such as sevoflurane with high gas flows may be initiated to quickly obtain end-tidal concentrations of 1 MAC before delivery; however, because of dose-dependent uterine relaxation effects, after delivery MAC should be lowered to 0.5 – 0.75, with supplementation with nitrous oxide 50 – 70%
Volatile as Tocolytics
usual rule: limit volatile agent to 0.5 MAC to minimise tocolytic effects
References
WCA2026: General anaesthesia for caesarean delivery: current role and best practices (youtube.com)