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Lower-Extremity Muscle Weakness After Removal of an Epidural Catheter Used for Anesthesia and Analgesia Following Total Knee Arthroplasty1
A sixty-eight-year-old man who had been diagnosed with severe osteoarthritis of the left knee presented for a total knee replacement. His medical history was unremarkable, and he took no medications other than nonsteroidal anti-inflammatory drugs. There was no family history of clotting abnormalities or stroke. The preoperative laboratory evaluation did not reveal any abnormality; the prothrombin time, activated partial thromboplastin time, international normalized ratio, and platelet count were all within normal limits. An epidural catheter was inserted prior to the operation to provide anesthesia during surgery and analgesia postoperatively. According to the medical record, the catheter was inserted without difficulty, the operation was completed uneventfully, and the patient was then transferred to a ward. Low-molecular-weight heparin (tinzaparin sodium, 4500 anti-factor Xa IU) was injected subcutaneously into the abdominal wall six hours after the operation and then once daily. Blood loss from the drain in the knee joint was 420 mL, which was considered unremarkable, and the drain was removed on the second postoperative day. Analgesia was provided through the epidural catheter with Naropein (ropivacaine hydrochloride) 0.1% (AstraZeneca, Monts, France) and fentanyl 2 mg/mL at an administration rate of 7 mL/h. Mobilization of the patient began on the first postoperative day. The epidural catheter was removed on the third postoperative day, twelve hours after administration of the anticoagulant injection, and the patient was allowed to have oral analgesics as needed. The next day (four days postoperatively), the patient reported muscle weakness and low-back pain. Neurologic evaluation revealed muscle weakness in all muscle groups of the lower extremities. According to the grading scale of the British Medical Research Council (in which a grade of 5 indicates normal strength), muscle strength was graded as 4 for the iliopsoas, 3 for the quadriceps, 4 for the hamstrings, 4 for the anterior tibial muscles, and 4 for the posterior tibial muscles. The low-molecular-weight heparin was discontinued. Until that time, the patient had received one dose of tinzaparin each day for four days. The last dose (fourth dose) was given on the third postoperative day, which was the day of the catheter removal.
An urgent magnetic resonance imaging scan was ordered, but the scanner was not available. In the afternoon, a clinical evaluation revealed increased muscle weakness in all muscle groups of the lower extremities. The muscle strength was rated as 3 in all muscle groups. The next morning, the patient demonstrated further weakening in the lower extremities, and muscle strength in all muscle groups was rated as 2 (iliopsoas, quadriceps, and hamstrings muscles) or 3 (anterior tibial and posterior tibial muscles). The patient had also lost control of bowel and bladder sphincters. A magnetic resonance imaging scan was acquired that morning (twenty-six hours after the first symptoms) (Fig. 1). The prothrombin time, activated partial thromboplastin time, international normalized ratio, and platelet counts were still within normal limits.
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