202411101216
Status:
Tags: Obstetrics, Neuraxial
Neuraxial anaesthesia induced hypotension in CS
The occurrence of maternal nausea-vomiting (often accompanied by dyspnea) is closely correlated with these hemodynamic variations
Fetal perfusion is dependent on uteroplacental blood flow, which lacks autoregulation, making it directly dependent on uterine perfusion pressure and inversely proportional to uterine vascular resistance.
The most widely accepted definitions of hypotension are either
- “SBP <80% baseline,” or
- “SBP <100 mm Hg or <80% baseline.”
The use of prophylactic vasopressors has demonstrated a benefit with regard to the incidence of hypotension both before and after delivery; it has also been shown to reduce the incidence of intraoperative nausea and vomiting during cesarean section
Ephedrine was the vasopressor of choice to treat and/or prevent maternal hypotension during CD for decades
However, subsequent studies in pregnant women suggested ==high placental transfer of ephedrine ==leading to a beta-adrenergic-mediated increase in CO2 and lactate production, particularly with doses above 15 mg
Although α-agonists that also have some β-agonist activity, such as norepinephrine and metaraminol, may have the best profile, phenylephrine is presently the most recommended drug because there is much more evidence supporting its efficacy and safety.
lower maternal morbidity with a prophylactic strategy: less hypotension, nausea/vomiting, tachycardia, dizziness and shortness of breath
A potential downside of norepinephrine is the risk of drug dilution error if prepared from concentrated vials manufactured for the ICU. Use of pre-made compounded dilute solutions may minimize the risk of dosing errors.
In the case of patients with preeclampsia, prophylactic administration of a vasopressor may not be necessary as these women are less likely to develop spinal anesthesia-induced hypotension than normotensive women
A crystalloid fluid coload (1 L administered immediately and rapidly after spinal injection) is preferable to a preload, and in combination with vasopressors significantly reduces the incidence of spinal-induced hypotension
In view of the potentially negative impact of overload on early post-CD rehabilitation strategies including early removal of urinary catheter in PACU whenever possible in uneventful CD, crystalloid co-loading should be limited to 500-1000 mL and infused quickly within the first 5-10 minutes after the induction of spinal anesthesia.
Among women randomized to receive a prophylactic phenylephrine infusion compared to intermittent bolus regimens, umbilical artery pH and base excess were improved and the incidence of maternal IONV was lower
Vasopressors and crystalloid co-loading at least should be combined to better prevent both hypotension occurrence and its severity.
The benefit of adding left lateral tilt, ondansetron and/or lower limb compression is more debated.
References
Society for Obstetric Anesthesia and Perinatology: Consensus Statement and Recommendations for Enhanced Recovery After Cesarean
Society for Obstetric Anesthesia and Perinatology Consensus Statement and Recommendations for Enhanced Recovery After Cesarean
Neuraxial Anaesthesia-Induced Hypotension During Caesarean Section - BJA Ed
Preventing and Treating Hypotension During Spinal Anaesthesia for Caesarean Section - BJA Ed