Can passive leg raise test predict hypotension after spinal anesthesia in pregnant women?

Purpose: Hypotension is the most frequent complication seen in pregnant women due to spinal anesthesia, which may result in undesired consequences both for the mother and the baby. In this study, we aimed to investigate the incidence of hypotension between pregnant women who were fluid responsive, and those who were not. The fluid responsiveness was evaluated by Passive Leg Raise (PLR) test. Moreover, we aimed to investigate the pathophysiology of hypotension and the mechanism of the treatment by evaluating the cardiac output (CO) and systemic vascular resistance (SVR) during hypotension and normotension after the treatment. Materials and methods: After the Investigational Board approval, 75 pregnant women aged 18 to 45 scheduled for elective cesarean section (C/S) operation under spinal anesthesia, were recruited for the study. In addition to the standard monitoring, suprasternal notch Doppler ultrasound CO measurements (USCOM) were performed on the patients. Routine spinal anesthesia protocol was performed. Fluid responsiveness, hemodynamic parameters, CO and SVR values were recorded. The patients were stratified into two groups depending on their fluid responsiveness with PLR test, as fluid responsive and unresponsive. Incidence of hypotension; CO and SVR values were compared between the two groups. Results: Stroke volume variation (SVV) and heart rate (HR) of the patients measured before spinal anesthesia were found to be higher in the patients with hypotension, compared with those without (P = 0.045 and 0.009 for SVV and HR, respectively). Fifty-five patients had more than 10% rise and 20 patients had less than 10% rise in CO in the PLR test. A small decrease in CO was detected during hypotension, but the difference was not statistically significant. CO values were found to be higher than the initial values after the treatment (P < 0.001). Of the patients with fluid responsiveness 67% developed hypotension, while this number was 50% in the patients without; but this difference was not statistically significant. No correlation was observed between the fluid responsiveness and hypotension (r = 0.082, P > 0.05). Sixty-six of the patients had block level above T4, and 68% of them developed hypotension, while none of the patients with T6 block level had hypotension (P < 0.001). SVR value was significantly reduced with the leg raise (P = 0.002). Decline in the SVR during hypotension was much more prominent and this significant decline continued after the treatment (P < 0.001). Basal HR was the strongest predictor for the development of hypotension as it had the largest area under "receiver operating curve". Conclusion: Cardiac output measurement via USCOM to detect the fluid responsiveness during PLR test in the patients undergoing elective cesarean section under spinal anesthesia was not a good predictor for the detection of spinal anesthesia-caused hypotension. HR was a stronger predictor of hypotension than the other parameters. Decrease in SVR had more significant role in the post-spinal hypotension pathophysiology than the decrease in the CO. Ephedrine used in treating post-spinal hypotension did not treat the decrease in SVR, but it maintained normotension by increasing the CO above the initial values.