Correlation of perfusion index with noninvasive hemodynamic parameters to evaluate stress response in neurosurgical cases under general anesthesia: an observational study

Background: The perfusion index (PI) is a noninvasive hemodynamic parameter measured by a pulse oximeter that reflects the peripheral perfusion. This study aimed to correlate the perfusion index with noninvasive hemodynamic parameters during periods of stress in neurosurgical cases. Patients and Methods: Fifty-five American Society of Anesthesiologists physical status I and II patients scheduled for elective supratentorial surgeries under general anesthesia were recruited. Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and PI were noted before induction, before and after intubation, skull pin insertion, skin incision, and craniotomy. Correlations between PI and HR, SBP, and DBP were assessed. Sensitivity, specificity, and positive and negative predictive values were calculated for SBP, DBP, and PI taking HR as the gold standard. Results: Intubation, skull pins, and incision produced significant increases in HR, SBP, DBP, and a significant decrease in PI when compared to pre-procedure values. Changes in PI were more pronounced (P < 0.001). A negative correlation was seen between PI and HR, SBP, and DBP (r = -0.22, -0.13, -0.18, respectively, P < 0.001). The area under the receiver operator characteristic curve is 0.75 for the PI criterion to predict stress response with a sensitivity of 81% (CI 76.99%-85.03%) and specificity of 59.92% (CI 56.35%-63.39%). Conclusion: PI correlated significantly with conventional hemodynamic markers during periods of stress. However, PI showed higher sensitivity, but lower specificity than SBP and DBP. Keywords: Blood pressure, heart rate, hemodynamics, intraoperative, monitoring