Total knee arthroplasty is one of the most successful operations performed. Multiple modalities are utilized for pain management in the perioperative period. Regional anesthesia is a common, effective method associated with high patient satisfaction. It typically provides exceptional local pain control without the systemic side effects that have been associated with oral or parenteral narcotics. Alleviation of pain allows for earlier mobilization and potentially shorter hospital stays. However, continuous infusion of a long-acting local anesthetic is not without risk. Case reports of severe complications such as hypotension, arrhythmia, seizure, and cardiovascular collapse have been reported, but all involved intra-articular injections or a single injection of a large dose of anesthetic medication to attain a regional block1-6. We found no reports of arrhythmia in association with an indwelling catheter in patients who were receiving regional anesthesia.
We present the case of a patient in whom a third-degree heart block developed in association with a continuous bupivacaine infusion through an indwelling femoral catheter. The patient was informed that data concerning the case would be submitted for publication, and she consented.
History
A seventy-eight-year-old woman who weighed 59 kg had a five-year history of progressive, debilitating, left knee pain that was most severe with walking, stair-climbing, and arising from a seated position. As nonoperative treatment had failed to provide relief, the decision was made to perform a total knee replacement. Her medical history included osteoarthritis of both knees, peptic ulcer disease, a cerebrovascular accident in 1993, and cirrhosis of the liver secondary to alcohol abuse. The patient had previously undergone a right total knee arthroplasty with no complications. Physical examination of the left lower extremity demonstrated a 20° valgus deformity and an arc of knee motion from 15° to 115°. Due to the known fact that the patient had liver disease, liver-function testing was obtained, the results of which revealed the following serum levels: aspartate aminotransferase, 57 U/L (laboratory normal value, <40 U/L), alanine aminotransferase, 42 U/L (laboratory normal value, <60 U/L), total bilirubin 0.7 mg/dL (11.97 µmol/L) (laboratory normal value, <1.4 mg/dL [23.94 µmol/L]), albumin 3.4 g/dL (34 g/L) (laboratory normal range, 3.5 to 4.0 g/dL [35 to 40 g/L]), and an international normalized ratio of 1.4 (laboratory normal range, 0.9 to 1.1). She had normal cognitive function, no asterixis, and no ascites. Assessment of the patient's chronic liver disease, with use of the modified Child-Pugh classification system, resulted in a score of 5 points (grade A), indicating well-compensated liver disease and a one-year survival rate of 100%7,8. The patient had no known history of hypertension, myocardial infarction, or cardiac arrhythmia. A preoperative electrocardiogram demonstrated normal sinus rhythm.
Perioperative Course
A left total knee arthroplasty was performed without complication. Prior to surgery, the anesthesia team, using a Stimuplex needle (B. Braun Medical, Bethlehem, Pennsylvania), placed a femoral nerve catheter without difficulty or complication. A femoral nerve block was established with the administration of 30 mL of 0.50% bupivacaine, and the catheter was left in place. No additional bupivacaine was infused during the surgery. The surgery was performed with the patient under general anesthesia. Following surgery, the patient was transferred to the postoperative anesthesia care unit, where laboratory studies and radiographs were obtained and the bupivacaine infusion was initiated (0.25% bupivacaine at 8 mL per hour). Postoperative laboratory studies revealed a hematocrit of 34% (laboratory normal range, 40% to 52%), a serum calcium level of 7.9 mg/dL (1.98 mmol/L) (laboratory normal range, 8.5 to 10 mg/dL [2.13 to 2.50 mmol/L]), and a serum magnesium level of 0.9 mg/dL (0.37 mmol/L) (laboratory normal range, 1.8 to 2.4 mg/dL [0.74 to 0.99 mmol/L]), with all other values within normal limits. Intravenous calcium gluconate and magnesium sulfate were given to correct the electrolyte imbalance. She was transferred to the surgical floor when her condition became stable.
On the evening of surgery, approximately six hours after the initiation of the bupivacaine infusion (nine hours after placement of the catheter and establishment of the nerve block), the heart rate of the patient was 38 beats per minute. The patient was alert and oriented but drowsy. Blood tests revealed a hematocrit of 32.5%, no electrolyte abnormalities, and normal levels of cardiac enzymes. Abnormal values included a serum albumin level of 2.8 g/dL (28 g/L) and an international normalized ratio of 1.6. An electrocardiogram (Fig. 1) demonstrated complete atrioventricular heart block (third degree). Cardiology and intensive care unit teams evaluated the patient, and a diagnosis of asymptomatic complete heart block with no discernible etiology was made. The femoral nerve catheter was discontinued by the orthopaedic team, and the patient was transferred to the coronary care unit for evaluation and monitoring. Within six hours following cessation of the bupivacaine infusion, the patient's heart returned to a normal sinus rhythm. The patient was transferred out of the coronary care unit forty-eight hours later and had no further episodes of heart block, conduction abnormality, or arrhythmia during the period of hospitalization. She was discharged home on the fourth postoperative day with no further complications. Additional cardiology workup on an outpatient basis was negative for any etiology of the heart block; the patient was therefore not started on any cardiac medications and was discharged from the cardiology clinic.