Combined BIS and Perfusion Index Response Linked to Post-Induction Hypotension Risk in Obese Patients

Dr Khushboo Agarwal A combined index that tracks changes in bispectral index and perfusion index during induction helped identify obese patients at risk of low blood pressure after induction.

Obesity is increasingly common among adult surgical patients. It changes how the lungs, heart, and blood vessels function and how anesthetic drugs are distributed and act in the body. As a result, the response to anesthesia induction can be hard to predict. Soon after induction, several factors can combine to cause a sudden fall in mean arterial pressure (MAP), and some patients need early vasopressor support. These factors include vasodilation, reduced sympathetic tone, myocardial depression, and relative hypovolemia.

Perfusion index (PI) and bispectral index (BIS) are usually assessed separately. A prospective cohort study therefore examined whether changes in BIS and PI could predict post-induction hypotension. The researchers looked at each measure alone and as part of a combined score, the Anesthesia Drug Response Index (ADRI).

The study included 128 obese adults with a body mass index (BMI) of 30 kg/m² or more who were undergoing elective surgery under general anesthesia. MAP, BIS, PI, and heart rate were recorded before induction and during the first 10 minutes after it. Post-induction hypotension was defined as any of the following:

A drop in MAP of 20% or more from baseline
MAP below 65 mmHg
A need for vasopressors

Hypotension occurred in 39 patients (30.5%). Compared with the others, these patients had a higher BMI, lower MAP before induction, and higher PI before induction. They were also more likely to have ASA III status or hypertension.

The authors concluded that BIS and PI assessment may help identify peri-induction risk early in obese surgical patients. ADRI showed promising discrimination but needs external validation before clinical use.

(Reference: Saba Arif, Muhammad Abdullah Shakeel, Urwadil Jamshed Ali, Aqeel Ahmad, Hafiz Muhammad Fawaad Bilal, Dure Shahwar. Anesthesia Drug Response Index in Obese Patients Using Perfusion Index + BIS: A Novel Composite Model. JHWCR [Internet]. 2026 Mar. 30 [cited 2026 Oct. 15];4(5):1-11. Available from: https://jhwcr.com/index.php/jhwcr/article/view/1825)