Spinal anesthesia: functional balance is impaired after clinical recovery

The ability of patients to walk without assistance after spinal anesthesia is a determining factor in the time to discharge following ambulatory surgery. The authors compared clinical markers of gross motor recovery with objective data of functional balance after spinal anesthesia.

Twenty-two male patients with American Society of Anesthesiology physical status I or II who were scheduled for perineal surgery were studied during recovery from spinal anesthesia to compare the predictive accuracy of clinical markers of ambulatory readiness (e.g., full knee flexion and extension) with that of an objective method of measurement focused on functional balance. Lumbar puncture was performed at the L2-L3 or L3-L4 interspace using a 25-gauge Whitacre needle, with patients in the sitting position. A 3-ml mixture of 5 mg bupivacaine (heavy) and 10 microg fentanyl was injected. Block regression and restoration of motor function were assessed and recorded. Functional balance was measured using a computerized force platform method.

The majority of patients maintained motor function and proprioception sensation at the onset of surgical anesthesia, as indicated by performance on clinical tests of function: 96% were able to perform the straight leg increase; 82, 77, and 91%, respectively, were able to perform full knee flexion and extension, perform heel-to-shin maneuvers, and identify joint position in the supine position. Postoperatively, clinical return of motor function occurred much earlier than recovery of functional balance. At 60 min after onset of spinal anesthesia, 22 patients (100%) had recovered sensory and gross motor function, but only 36% could stand, and 8% could walk without assistance (P < 0.01). At 150-180 min after onset, 96-100% of patients achieved the levels of functional balance that permitted adequate ambulation.

The results suggest that the recovery time to unassisted ambulation is longer than has been assumed, and that the standard clinical markers of gross motor function are poor predictors of functional balance following ambulatory surgery.