Heart rate variability and cardiac baroreflex inhibition-derived index predicts pain perception in burn patients

Dressing changes induce acute pain in burn patients. This pain is difficult to predict and may be therefore undertreated. Two different non-invasive electrophysiological indices from heart rate variability and baroreflex inhibition-derived indices, analgesia/nociception index (ANI) and cardiovascular depth of analgesia (CARDEAN), have been proposed to predict and better assess adequacy of anti-nociception. The aim of this study was to evaluate these techniques as early pain alert tools in conscious burnt patients during dressing changes' procedures.

Twenty adult burnt patients undergoing scheduled wound treatment procedures were included in this prospective observational study. Pain intensity was assessed using a 0-10 numerical rating scale (NRS) and was compared with both ANI and CARDEAN, during the procedures. Non parametric rank sum test and linear discriminant analysis were used for evaluating potential differences of measured variables between periods with different pain intensities. Receiver-operating characteristic (ROC) curves were built to assess their performance to detect pain within following 15s.

The sensitivity and specificity of ANI to detect pain were 67% and 70% and those of CARDEAN were 77% and 80%, with area under the curve (AUC) values of 0.75 and 0.83, respectively. Their combination increased AUC to 0.87.

Both ANI and CARDEAN indices during wound treatment procedures seem to discriminate periods with and without pain within 15s, serving as a potential complementary tool for early optimized pain control.