A comparative study of hemodynamic stability through intraoperative fluid administration guided by stroke volume variation assessment versus conventional parameters in terms of inferior vena cava diameter and collapsibility index during spine surgery

Abstract

Stroke volume variation (SVV) is a naturally occurring phenomenon, often used by anesthesiologists for hemodynamic response to intra-operative fluid administration. In a mechanically ventilated patient under general anesthesia, the arterial pulse pressure rises during inspiration and falls during expiration due to changes in intra-thoracic pressure secondary to positive pressure ventilation. : In this open labelled, parallel group, randomized controlled trial, we investigated the role of using SVV as a marker for optimal intra-operative fluid therapy versus the conventional parameters of hemodynamic monitoring i.e., blood pressure, pulse rate and urine output in patients undergoing major spinal surgery in prone position. It was a single centre study and each group consisted of 35 patients in the age group of 18 – 50 years having ASA grade I status and without any previous comorbidities. SVV was maintained between 10 to 13% and Non-Invasive Blood Pressure (NIBP) and pulse rate maintained within 20% of baseline pre-induction values. Ringer’s lactate solution was chosen as fluid therapy in both groups. : The study showed that the total amount of fluid infused to either group had no statistically significant difference; however, the change in Inferior vena cava maximum diameter (IVCmax) in patients of the SVV monitored group was significantly lower than the conventional arm, for a given amount of fluid in either group. (Levene’s test for equality of variance F = 45.46, test statistics for equality of means t = 3.86; p = 0.001) Moreover, those patients who were maintained on lower margin of SVV range had a remarkable decrease of collapsibility index of IVC compared to pre-operative values. (Spearman’s rank correlation r = 0.533; p = 0.001) Thus, SVV proves to be a surrogate marker of administering intravenous fluid per-operatively maintaining euvolemic status as reflected by subsequent IVC collapsibility index (CI) values obtained in patients undergoing spinal surgery.