Predictive value of baseline perfusion index for hypotension after spinal anaesthesia in elderly patients undergoing lower limb orthopaedic procedures

Background: Hypotension is a clinically significant and commonly presented complication resulting from the spinal anaesthesia with higher incidence being reported in elderly subjects resulting from the compromised compensation of baroreceptor reflex. Monitoring using intermittent NIBP (non-invasive blood pressure) result in delay for detection of hypotension. The PI (perfusion index) is a continuous and non-invasive measure for peripheral perfusion which can act as an early indicator for hemodynamic parameters and is a potential biomarker to assess hypotension.

Aim: The present study was aimed to assess the relationship in incidence of hypotension and baseline perfusion index in elderly subjects undergoing orthopedic surgeries for lower limb under spinal anesthesia, The study also aimed to assess whether intraoperative change in perfusion index precede NIBP-defined hypotension and to assess response of perfusion index after administration of vasopressor.

Methods: The present study assessed 128 subjects aged 60 years or more and undergoing orthopedic surgeries for lower limb under spinal anesthesia using subarachnoid block. They were divided into 2 groups of 64 subjects each depending on baseline perfusion index of >3.5 or ≤3.5. The incidence of hypotension was assessed in the two study groups which was considered as >20% reduction from pre-anesthetic systolic blood pressure in these subjects.

Results: The study results showed that hypotension incidence was significantly higher in Group I subjects as seen in 100% (n=64) subjects compared to Group II where incidence was 22% (n=14) subjects with p<0.0001. Also, greater number of hypotension episodes were recorded in Group I. Baseline perfusion index of >3.5 showed hypotension prediction with 100% specificity and 82% sensitivity. The negative and positive predictive values were 78% and 100% respectively.

Conclusion: The present study concludes that a baseline perfusion index of >3.5 is a highly sensitive and specific non-invasive predictor for development of hypotension in elderly subjects administered with spinal anesthesia. Intraoperative changes in perfusion index have been correlated with hypotension; they are not essentially seen preceding its onset as assessed by NIBP measurement. Hence, clinical utility of perfusion index is attributed to preoperative risk assessment.