Non-invasive PREDIctive Hemodynamic Continuous moniToring vs Standard Intermittent Blood Pressure and Post-spinal hypotensION During Elective Cesarean Section: a Randomized Clinical Trial

Caesarean section (CS) is one of the most commonly performed operations worldwide, with 1 in 5 women (21.1%) currently giving birth through this route.

The introduction of neuraxial techniques determined an improved safety, better postoperative analgesia, reduction in hemorrhage, higher Apgar scores in the neonate and a more participative birth experience.

Single shot spinal anesthesia (SA) is the most commonly used technique because it provides rapid onset, effective and reliable anesthesia.

SA induces a sympathetic block that almost inevitably produces maternal hypotension (Post Spinal Hypotension - PSH) often accompanied by nausea, vomiting and bradycardia. Sustained PSH may lead to decreased utero-placental blood flow and fetal acidosis. For this reason, the optimal management of hypotension in this setting has become one of the most active areas of research in obstetric anesthesia. In particular, preventive administration of vasopressors directly counter arteriolar vasodilation and decreased systemic vascular resistance and, by maintaining vascular tone in venous and splanchnic vessels, increases venous return and cardiac filling.

Although proactive vasopressor administration is now considered the strategy of choice for PSH, the ideal drug, dose, and mode of delivery have been debated. Studies comparing prophylactic phenylephrine infusions and rescue boluses doses have shown conflicting results. Routine prophylactic vasopressor infusion raises concerns for unnecessary or even inappropriate treatment, particularly when hypotension is unlikely to develop (50%). In other words, half of the patients, those not experiencing spinal-induced hypotension, may be exposed to unnecessary vasopressor infusion potentially developing adverse effects such as hypertension, tachycardia, Takotsubo cardiomyopathy, ventricular arrhythmias. Prophylactic phenylephrine infusions have gained favor, as recommended by the latest published international consensus statement. On the other hand, continuous vasopressors infusions may be detrimental to hemodynamic homeostasis, potentially resulting in reactive hypertension or precipitating a baroreceptor-mediated bradycardia, which in turn may result in reduced maternal CO: indeed, cardiac output decreases significantly with increasing phenylephrine rate. Norepinephrine prophylaxis is gaining popularity in clinical practice because of less bradycardia and higher maternal CO compared with phenylephrine prophylaxis. Nevertheless, concerns about an effect of norepinephrine on fetal acidosis were raised by several authors: lower umbilical pH using continuous infusion of vasopressors probably result from placental transfer and stimulation of foetal metabolism.