Effectiveness of plethysmographic variability index for prediction of subarachnoid block induced hypotension in caesarean section

Background: Hypotension is frequently observed after spinal anaesthesia for cesarean section and canbe detrimental to both mother and baby. The pleth variability index (PVI) is a new algorithm used forautomatic estimation of respiratory variations in pulse oximeter waveform amplitude, which mightpredict fluid responsiveness. Because anaesthesia-induced hypotension may be partly related to patientvolume status. The pleth variability index (PVI) was developed as a noninvasive bedside measurementof this variation in the pulse oximetry waveform. Objective: To observe the hypotension predictive capacity of PVI and to find out association & correlationof PVI with sphygmomanometeric blood pressure measurement. Methods: This observational study was carried out in the department of anaesthesia, Analgesia andIntensive Care Medicine Bangabandu Sheikh Mujib Medical University, Dhaka between July 2015 toDec 2015. A total 100 elective caesarean section patients under subarachnoid block were selected by theinclusion and exclusion criteria. Patients who fulfill the ASA physical status i, ii. and full term singletonpregnancy height from 152cm to160cm. were included and patients suffering from obesity (bodyweight>115 kg), hypertension, COPD, bronchial asthma, haemoglobinopathies, severe anaemia,arrythmia, heart failure, any congenital heart disease, pre-eclampsia, total placenta praevia or patientwho took anti hypertensive medications were excluded from the study. Patients were divided in twogroups, PVI ³22.0 in group-A and PVI <22.0 in group-B.Dehydration was corrected 10 min before sub arachnoid block (sab). Pre–anesthetic Himoglobin% SPO2,Heart rate, PVI & blood pressure was recorded at baseline after 5 minutes of rest by one anesthesiologist.Subarachnoid block performed with 0.5% hyperbaric bupivacaine (12.5 mg) at the L3-L4 intervertebralspace on sitting position. After spinal block patient was returned to supine position with a wedge underbuttock to facilitate left uterine displacement. Oxygen 4 lit/min was administered via face mask.Immediately after sub arachnoid block Spo2, heart rate, SBP and DBP was recorded by anotheranesthesiologist at 2 minutes interval in first 10 minute. Surgical incision was allowed when a blocklevel at least T6 dermatome was obtained with cold & pin prick.All data was recorded by two anesthesiologist who were not involved in the study. The study ended withdelivery of the baby. Chi-Square test was used to analyze the categorical variables, shown with cross tabulation.Student t-test was used for continuous variables. p value <0.05 was considered as statistically significantly. Result: In baseline, majority (58.0%) patients was found PVI e”22 (group A) and 42(42.0%) was PVI <22(group B). Mean age of the patients was 27.5±4.5 years, Mean heart rate was found 93.2±5.8 beats/minin group A and 89.7±12.7 beats/min in group B. The mean systolic BP was found 132.1±7.7 mmHg ingroup A and 128.7±8.5 mmHg in group B. The mean diastolic BP was found 80.9±3.8 mmHg in group Aand 79.1±5.1 mmHg in group B. The mean MAP was found 98.0±5.6 mmHg in group A and 95.6±6.8mmHg in group B. The mean SPO2 was found 97.8±1.4 in group A and 97.4±1.5 in group B. The meanperfusion index was found 5.0±2.6 in group A and 5.4±3.5 in group B. The mean pleth variability index was found 22.5±2.3 in group A and 15.1±3.1 in group B. The mean pleth variability index was statisticallysignificant (p<0.05) between two groups. Conclusion: Higher baseline pleth variability index can associated with hypotension after spinalanaesthesia for cesarean section may be a clinically useful predictor. JBSA 2018; 31(2): 62-66