Cardiac Dysrhythmia and Arrest After Adductor Canal Block

Introduction We describe a case of ventricular dysrhythmia and cardiac arrest under general anesthesia after an adductor canal block for knee arthroscopy. Intra-operative trans-esophageal echocardiography showed an ejection... [ view full abstract ]

Introduction

We describe a case of ventricular dysrhythmia and cardiac arrest under general anesthesia after an adductor canal block for knee arthroscopy. Intra-operative trans-esophageal echocardiography showed an ejection fraction of 10% with biventricular failure. The patient was treated with an aortic balloon pump and intralipid, and then regained cardiac function.

Case report

A 22 year-old, 70kg male, presented for knee arthroscopy after multi-ligamentous injury in a motorcycle accident. Pre-operative assessment did not reveal any medical history, and patient had previously tolerated a procedure to the hand/wrist under local anesthetic. In the pre operative area an adductor canal saphenous nerve block was performed under ultrasound guidance with patient monitors in place. A 2 inch 21 gauge needle was used with 25 mL of 0.5% ropivacaine. The patient tolerated nerve block well without any neurological or cardiovascular signs or symptoms. He was then taken to the operating room where general anesthesia was induced without incident. Approximately 3 minutes after induction, about 25-30 minutes after regional block the heart rate increased from 80 to 120. The patient then went into ventricular tachycardia and was treated with 70mg lidocaine IV for a total of 100mg including induction. This converted the rhythm to junctional tachycardia and then sinus tachycardia. At this point blood pressure and CO2 began to decrease. He then went into pulseless ventricular tachycardia and was treated with CPR and cardioverted back into NSR. TEE was performed intra-operatively revealing ejection fraction of 10% and biventricular failure with global hypokinesis. This was treated with epinephrine, phenylephrine and milrinone. Cardiology then placed an aortic balloon pump in the operating room. The patient was also treated with an intralipid infusion. After monitoring in the ICU the patient was weaned off pressors and extubated with ejection fraction of 35-40% on repeat echocardiography. Follow up exam with CT angiogram and echocardiography 2 months after discharge showed fully normal cardiac function.

Discussion

This case possibly represents an atypical presentation of local anesthetic toxicity. It is unusual that the patient did not show any symptoms pre-operatively after regional anesthesia. Each dose of local anesthetic (ropivacine 125mg, Lidocaine 100mg) was well below the recognized toxic dose. The delayed onset and absence of any neurological symptoms such as numbness and seizures is also atypical. General anesthesia may have masked these symptoms so that ventricular tachycardia was the first visible sign. The treatment of the dysrhythmia with additional lidocaine could have contributed to a reaction to local anesthetics. Movement of the extremity while transferring to the operating table could introduced more local anesthetic into circulation, though any movement was minimal. A pulmonary embolism is also in the differential, but TEE imaging was inconsistent with expected right heart effects. The patient may also have had a genetic predisposition to local anesthetic or general anesthetics that was exposed during the procedure. Fortunately with TEE and cardiology immediately available the patient was able to make a full recovery.