Analgesia nociception index as a tool to predict hypotension after spinal anaesthesia for elective caesarean section.

Arterial hypotension is the main disadvantage of spinal anaesthesia (SA) for caesarean delivery with deleterious effects on maternal-foetal outcomes. Recently, a non-invasive device 'analgesia nociception index' (ANI) has been developed to evaluate the parasympathetic component of the nervous autonomous system. The aim of this study was to evaluate the ability of ANI to predict the risk of hypotension after SA for elective caesarean section. One hundred patients scheduled for elective caesarean delivery under SA were recruited in this observational prospective study. Hemodynamic and ANI parameters were recorded in supine position (TB), in sitting position (T0), after induction of SA (T1) and then every three minutes (T2, T3, Tn) until the end of surgery or having resort to ephedrine. After SA, women were classified into two groups according to occurrence of hypotension (group H, n = 80) or not (group C, n = 20). The variations of ANI between T2 and T0 were significantly higher in the group H as compared to the control group. A threshold of 4.5 points decrease in instantaneous ANI value could predict maternal hypotension. ANI is a simple and effective tool in predicting the risk of SA-related hypotension.Impact statementWhat is already known on this subject? Arterial hypotension is the main disadvantage of spinal anaesthesia for caesarean delivery with deleterious effects on maternal-foetal outcomes. The balance between the sympathic and parasympathic systems could be used to predict the onset of hypotension following spinal anaesthesia. Analgesia nociception index (ANI) is an index calculated based on heart rate variability HRV analysis, designed originally to evaluate the antinociception/Nociception balance.What do the results of this study add? We have shown that the analysis of HRV with ANI was a predictor of maternal hypotension after spinal anaesthesia.What are the implications of these findings for clinical practice and/or further research? ANI is an effective tool in predicting the risk of spinal anaesthesia-related hypotension. These findings are of potential clinical importance in the obstetrical anaesthesia setting. Further studies are required in order to implement this simple tool and optimise prophylactic measures especially vasopressors.