Single shot spinal anaesthesia with hypobaric bupivacaine for hip fracture repair surgery in the elderly. Randomized, double blinded comparison of 3.75 mg vs. 7.5 mg.

BACKGROUND Arterial hypotension is the most frequent adverse effect of subarachnoid anaesthesia in the elderly sustaining a femoral proximal fracture. Decreasing the local anaesthetic dose reduces the incidence of hypotension but shortens sensory block duration that could be insufficient in some surgical procedures. Sensory block duration could be prolonged using hypobaric local anaesthetics. We evaluated whether low hypobaric bupivacaine doses were adequate for this type of surgery while maintaining the haemodynamic stability. METHODS A prospective, randomized, double blinded study was designed. Patients over 65 years old, sustaining traumatic hip fracture, were assigned to one of two groups: B0.5 group, hypobaric bupivacaine 7.5mg 5mg/ml (control group), and B0.25 group, hypobaric bupivacaine 3.75 mg 2.5mg/ml (study group). After subarachnoid injection, sensory level and motor blockade degree were registered, as were blood pressure, and heart rate at basal time and at 2, 5, 10, 15, 20 and 30 min after injection. The doses of vasopressor needed were registered as well. Surgical conditions and the duration of the surgical procedure-whether rescue analgesia or anaesthesia was needed-and sensory level regression to T12, were registered as well. RESULTS Sixty four patients was the calculated sample size. The study was stopped in an interim analysis because an elevated number of patients in the B0.25 group needed iv rescue anaesthesia. In the analyzed cases, blood pressure was significantly lower in the B0.5 group at the 15 and 30 min measurements. Vasopressor drugs needs were similar between groups [ephedrine accumulated mean (SD) doses 11.4 (5.2) mg vs. 9.1 (2.7) mg, p=0.045)]. Sensory block regression to T12 was faster in the B0.25 group, [(mean (SD) 68.2 (29.0) min vs. 112.8 (17.3) min in the B0.5 group, p<0.05]. Five out of 19 patients in the B0.25 group needed intravenous anaesthesia rescue before surgery started. CONCLUSION Lowering hypobaric bupivacaine dose to 3.75 mg in subarachnoid anaesthesia for hip fracture repair surgery in elderly patients decrease intraoperative blood pressure, but in an important number of patients intravenous anaesthesia rescue was needed and preclude recommendation.