Femoral artery Doppler as a novel predictor of spinal hypotension in elective cesarean delivery cases: a prospective observational study.

BACKGROUND

Spinal anesthesia is the preferred anesthetic for elective cesarean deliveries, though spinal hypotension requires prophylactic intervention to avoid serious complications. Several parameters have been studied to predict spinal hypotension; however, no reliable predictor has been identified to date. Spinal anesthesia induces femoral artery vasodilatation that induces flow velocity changes. Therefore, our study aimed to evaluate whether changes in femoral artery Doppler indices could serve as predictors of spinal hypotension.

METHODS

This prospective observational study included pregnant women undergoing elective cesarean delivery. Spinal hypotension was defined as a reduction of systolic blood pressure of >20 % of the baseline value. All patients received a co-load of lactated Ringer's 200 mL over 10 minutes, and a prophylactic infusion of noradrenaline 0.08 µg/kg/min. An experienced operator performed Doppler examinations of the right common femoral artery before, immediately after, at two, and five minutes after spinal anesthesia. Pulsatility and resistive indices were calculated using built-in software. A receiver operating characteristic curve analysis was performed to assess the accuracy of Doppler indices in predicting spinal hypotension. The primary outcome variable was the accuracy of the change in pulsatility index in predicting spinal hypotension.

RESULTS

Forty patients were included in the study. Patients with hypotension (n=13) showed higher baseline Pulsatility index, shock index, change in pulsatility index, change in resistive index, and change in waveform morphology. Doppler indices showed a good predictive ability for predicting spinal hypotension. The AUC (95% CI) for change in pulsatility index and resistive index to predict spinal hypotension were 0.99 (0.90-1.00) and 0.96 (0.85-1.00), respectively. In addition, the best cut-off values for the change in pulsatility and resistive indices to predict spinal hypotension were >10.6% and 12%, respectively.

CONCLUSION

Our findings in women undergoing scheduled cesarean delivery under spinal anesthesia and prophylactic norepinephrine infusion show that changes in the femoral artery Doppler indices, specifically pulsatility index, resistive index, and waveform morphology, may predict spinal hypotension. Absent morphological changes after spinal anesthesia can rule out spinal hypotension, with a 100% negative predictive value.