International Journal of Anesthesiology & Pain Medicine

The Predictive Value of Baseline Pulse Oximeter Perfusion Index on the Incidence of Hypotension During Balanced General Anesthesia Induction

Hypotension is a common occurrence during general anesthesia induction. Perfusion Index (PI) has been used as a measure of systemic vascular resistance and was shown to predict hypotension after regional anesthesia and propofol induction.

Objective: This study aims to determine whether baseline PI can predict hypotension during balanced general anesthesia induction and determine a cut-off value where hypotension is expected to occur.

Methods: Thirty-five ASA I/II adults who will undergo elective surgery under general anesthesia were enrolled. Heart rate, blood pressure and PI were measured every minute from baseline to 5 minutes following induction and 10 minutes after endotracheal intubation. Hypotension was defined as fall in systolic BP (SBP) by >30% from baseline and/or mean arterial pressure (MAP) to <60 mm Hg. Severe hypotension (MAP of <55 mm Hg) was treated.

Results: Hypotension was not observed in the first 5 minutes but was present in 11.4% of subjects by the 10^th minute and 5.7% of subjects by the 15^th minute. PI showed very low (r < 0.2) to low (r = 0.2 to 0.39), negative to positive and insignificant correlation (p > 0.05) with hypotension whether using SBP or MAP criterion and whether observed at 10 or 15 minutes of anesthesia induction. The Area under the ROC curve is 0.397, 95% CI [0 .126, 0.667], p = 0.431.

Conclusion: This study lends inconclusive evidence on the utility of perfusion index to predict hypotension during balanced general anesthesia induction for this sample of patients. Interestingly, there was a positive, moderate (r=0.538, 0.501 and 0.469) and significant (p<0.05) correlation between perfusion index and SBP, Diastolic BP and MAP, respectively.

Author(s):

Brian Rainier T Herradura, MD, Beverly Anne P Portugal, MD, Olivia C. Flores, MD

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