Evaluation of perfusion index to predict hypotension in lower segment cesarean section under spinal anaesthesia.

Sympathetic blockade and decreased cardiac output causes hypotension after spinal anaesthesia. Pregnancies are associated with increased sensitivity to local anaesthetic, decreased response to vasopressors and a low mean arterial pressure (MAP) at term. These women may develop profound hypotension following central neuraxial blockade for the lower segment caesarean section (LSCS).

The aim is to study the role of perfusion index to predict the incidence of hypotension in lower segment cesarean section under spinal anaesthesia. The primary objective of this study is to determine if Perfusion Index >3.5 is associated with higher incidence of hypotension in lower segment cesarean section under spinal anaesthesia.

Written informed consent will be taken from all patients followed by detailed pre-anaesthetic evaluation and airway examination.  Patients will be received in the pre-operative room. The patient’s particulars will be checked. Standard monitoring with electrocardiography, automated NIBP, and pulse oximetry (SpO2) will be performed for baseline values and intraoperative monitoring. Baseline hemodynamic values including Perfusion Index will be recorded in the supine position. The perfusion index will be measured in the supine position using a specific pulse oximeter probe (Masimo® MightySatâ„¢Fingertip Pulse Oximeter; Masimo Corp., Irvine, CA, USA) attached to the left index finger of all patients to ensure uniformity in measured PI values. Those with a baseline Perfusion Index of ≤3.5 fall into Group I and those with a Perfusion Index of >3.5 fall into Group II. Maximum cephalad spread will be checked every 2 minutes from time of Subarachnoid Block (SAB) and then every minute till maximum level is achieved.). Systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP), heart rate (HR), SpO2 and PI will be recorded at 2 minutes intervals after the SAB up to 20 minutes and then at 5 minutes interval till the end of surgery. Hypotension is defined as a decrease in MAP <65 mmHg and treated with IV bolus of 6 mg injection Mephentermine. Bradycardia is defined as HR <55 beats/min and treated with injection atropine 0.6 mg IV bolus. Injection oxytocin (2 units IV bolus + 10 units in 500 ml of Ringer’s Lactate slow infusion over 1 hour) will be given as uterotonic following baby extraction. Patients requiring additional oxytocics and/or additional surgical interventions are excluded from

the study. The incidence of other side effects such as nausea, vomiting if observed will be recorded. Following extraction of the baby, APGAR score will be recorded at 1 and 5 minutes followed by fetal pH and base excess (BE) utilizing umbilical cord blood gas analysis where sample will be obtained from segment of double clamped cord after delivery of the baby in pre-heparinized 1 ml syringe.

All observations will be recorded in the proforma and analyzed using appropriate statistical methods.