Literature Review: Spinal Anesthesia: Functional Balance is Impaired after Clinical Recovery

Anthony R. Brown, MB

Imarengiaye CO, Song D, Prabhu AJ, Chung F. Anesthesiology 2003;98:511-5

In this study, the authors compared clinical markers of gross motor recovery with objective data of functional balance after spinal anesthesia.

The study included 22 ASA I and II male outpatients (18-65 yrs old) scheduled for elective ambulatory peroneal surgery. Spinal anesthesia was administered in the sitting position at L2-L3 or L3-L4 intervertebral space with a 25-gauge Whitacre needle. A 3 mL mixture of 5 mg heavy bupivacaine (7.5%), 10 mg fentanyl, and 0.9% saline was injected slowly into the subarachnoid space. The patient was placed in the supine position to achieve sensory blockade to T10-T12 within 10 min. and supplementary fentanyl 25-50 mg was administered IV on patient request.

Motor function of the lower extremities was assessed using straight leg raises, deep knee bends, heel-to-shin maneuvers, and modified Bromage scores 30-60 min before anesthesia (baseline), 5 min after spinal injection, 60 min after spinal injection (first postoperative assessment), and every 30 min thereafter until the patient was discharged home. The level of the block was determined at the same time intervals by testing response to pin-prick stimulation.

Functional balance was determined using a Balance Master system (model 6.1). This is a computerized force platform in which the patient's feet are placed on 2 foot pads, each resting on a transducer that's transmits movement-generated signals to a computer that calculates and tracks the force and movement of the patient's center of gravity and displays the value on a monitor. The functional balance tests chosen for this study included the sit-to-stand test, the step-up/-over test, and the tandem walk. The timing of the tests were the same as those testing motor function with the exclusion of the one performed 5 min after spinal anesthesia. Motor function and ability to ambulate were assessed clinically prior to each balance test. Ambulatory readiness and candidacy for discharge were defined by the patients' ability to walk steadily without assistance. Temporal measurements included time to onset of spinal anesthesia, duration of anesthesia and surgery, times to return of motor and sensory function, recovery to ambulatory readiness, PACU discharge, and discharge home.

All patients achieved satisfactory surgical anesthesia to T11-T12 and none required supplemental intraoperative analgesia. Most patients maintained motor function and proprioception 5 min after spinal injection: 96% were able to achieve the straight leg increase, 82% were able to perform deep knee bends, 77% were able to perform heel-to-shin maneuvers, and 91% were able to identify joint positions.

At 60 min after spinal injection the level of sensory blockade averaged T12 (T3-L3) and all patients were able to straight leg increase. The remaining tests of motor function were similar to those recorded 5 min after spinal anesthesia. In contrast, functional balance tests demonstrated that only 36% of patients could actually stand and even fewer (18%) could complete the Balance Master assessment. The latter group had significantly lower rising indexes compared to their preanesthesia baselines.

At 90 minutes after spinal injection the level of sensory blockade averaged L2 (T3-S2) and all patients could successfully perform the motor function tests and identify joint position. The percentage able to stand increased to 73% and 55% fulfilled functional balance tests.

At 150 min after spinal injection, 96% of patients had fully recovered their ability to walk steadily without assistance, and their balance scores achieved preanesthesia values (within ± 20% ranges). At this time their median level of blockade was L2 (T10-S2). Only 1 patient achieved full ambulatory recovery at 180 minutes.

Commentary

This elegant study clearly demonstrates that tests of gross motor function are inadequate as indicators of the ability to ambulate in readiness for discharge. As concluded by the authors, these results suggest that the ability to walk without assistance after spinal anesthesia requires a longer recovery period than predicted solely by gross motor recovery, making its return inadequate as a sole marker of ambulatory ability and readiness for discharge. Spinal anesthesia is favored by many of us over general anesthesia in the outpatient setting as a technique that is easy to perform, with a low failure rate and rapid onset, and affords us the opportunity of avoiding the side effects associated with general anesthesia and opioid analgesia. Pressures to discharge ambulatory patients from the hospital in the shortest possible time has resulted in ever decreasing doses of spinal local anesthetic with various additives to limit the degree and duration of motor blockade. This study serves as a warning that even with low doses of local anesthetics, we should not only determine that full motor recovery has been achieved, but in addition, we should be aware that the recovery time to unassisted ambulation is longer than has been assumed. In addition, the standard clinical markers of gross motor function are poor predictors of functional balance following ambulatory surgery.

Anthony R. Brown, MB
Columbia University
New York, NY