Supraclavicular block evaluation in oncoorthopedic patients under general anesthesia using perfusion index: A prospective cohort study

Background: Supraclavicular brachial plexus blocks (SCBPB) are routinely placed prior to anaesthetic induction for post-operative pain relief after prolonged orthopaedic oncosurgery, since patients are required to remain awake for sensorimotor evaluation of block. If the window period after surgery but before anesthesia-reversal is employed for administering SCBPB, it bestows the quadruple advantage of being painless, not augmenting surgical bleed, longer post-operative analgesia and reduced opioid-related side effects. The problem spot is assessing SCBPB-efficacy under general anesthesia. Methods: This prospective, single-centric, observational cohort study included 30 patients undergoing upper limb orthopaedic oncosurgery under general anesthesia. Perfusion index (PI) was assessed using two separate units of Radical-7™ finger pulse co-oximetry devices simultaneously in both the upper limbs and PI ratios calculated. Skin temperature was noted. Results: After successful block, PI values in blocked limb suddenly increased after 5 min, progressively increasing for next 10 min, whereas PI failed to increase further above that attained post anaesthetic-induction in unblocked limb. PI values in the blocked limb were 4.32, 4.49, 4.95, 7.25, 7.71, 7.90, 7.94, 7.89, and 7.93 at 0, 2, 3, 5, 10, and 15 min post block-institution at reversal and 2 min, 5 min post-reversal, respectively. PI ratios at 2, 3, 5, 10, and 15 min post block-administration in the blocked limb, taking PI at local anaesthetic injection as denominator were 1.04, 1.15, 1.67, 1.78, and 1.83, respectively. Correlation between PI and skin temperature in the blocked limb gave a repeated measures correlation coefficient of 0.79. Conclusion: Monitoring trends in PI and PI-ratio in the blocked limb is a quantitative, non-invasive, inexpensive, simple, effective technique to monitor SCBPB-onset in anaesthetised patients.