Variability of Perfusion Index to Predict Hypotension

About one-third of deliveries are performed by cesarean section, and this rate is increasing. The standard anesthetic technique for this procedure is spinal anesthesia (SA), which is associated with hypotension in nearly 70% of cases . The mechanism is a sympatholysis leading to a drop in systemic vascular resistance and cardiac output, which can be aggravated by relative hypovolemia. This hypotension is responsible for maternal dizziness, nausea, and vomiting, as well as fetal acidosis, and in extreme cases, fetal circulatory insufficiency.

Currently, it is recommended to prevent post-spinal hypotension through a strategy combining co-loading with fluids and the administration of vasopressors in all patients. However, this non-individualized strategy is not always effective in preventing hypotension and may even be harmful to the mother in cases of excessive fluid administration.

Current guidelines for perioperative fluid management in elective surgery advocate for an individualized approach based on preoperative assessment of preload dependence through cardiac output monitoring. Correcting this relative hypovolemia helps maintain an appropriate blood pressure for the patient's needs.

In parturients, we have shown that evaluating preload dependence by measuring the variation in the time-velocity integral under the aorta (ΔTVI) using cardiac ultrasound before and after a passive leg raising test (PLR) can predict post-spinal hypotension with good sensitivity and specificity. We obtained comparable results using monitoring of the variation in stroke volume by the Clearsight™ system (Edwards Lifesciences, Irvine, California, US), before and after PLR .

However, these technologies have limitations: availability of equipment, cost, operator expertise, and patient echogenicity in the case of ultrasound. Using a non-invasive, simple, and accessible method for monitoring preload dependence that can be used by an untrained operator would help easily identify patients at higher risk for post-spinal hypotension, enabling individualized management.

The main objective of our study is to evaluate the ability of ΔIPELJP to predict post-rachianesthesia hypotension in parturients scheduled for a cesarean section.

This is a prospective, monocentric study carried out at the level 3 maternity unit of Marseille's Hôpital Nord Patients will be monitored as usual using an SpO2 sensor placed on the index finger of the limb contralateral to the blood pressure cuff, giving the PI value, a blood pressure monitor taking blood pressure (systolic, diastolic and mean) every 2 minutes, and an ECG.

A transthoracic cardiac echocardiogram will be performed with measurement of the sub-aortic time-velocity integral, and the same measurement will be taken 1 min after a passive leg-lift to see whether this maneuver significantly increases systolic ejection volume. The PI value and arterial pressure will be measured at each of these manoeuvres. The same data will be collected one minute after return to the initial position. Thereafter, PI and arterial pressure will be recorded every two minutes until the newborn is delivered.

The pH of the newborn's cord blood is systematically recorded.

Eligibility Criteria:
Inclusion Criteria:

* Parturient women
* With a term of more than 34 weeks' amenorrhea (SA)
* Requiring a scheduled caesarean section under spinal anaesthesia at the maternity ward of the Hôpital Nord de Marseille (AP-HM).
* Patients affiliated to a Social Security System

Exclusion Criteria:

* Urgent caesarean section
* Contraindication to perimedullary anesthesia
* Clinical features likely to distort the plethysmographic signal: scleroderma, Raynaud's syndrome, nail pathology, etc.
* Presence of anti-hypertensive treatment
* Cardiac arrhythmia
* Anesthetist not trained in transthoracic cardiac echography
* Refusal to participate in the study
* Guardianship or curatorship, safeguard of justice
* Instable Perfusion Index Signal