Bradycardia and severe vasospasm caused by intramyometrial injection of vasopressin during myomectomy.

Vasopressin is often used locally to reduce blood loss during surgery. Vasopressin has longest clinical effect, but its systemic effects may be profound and pose significant challenges for the anesthesiologist and it can also sometimes cause lethal complications. The loss of peripheral pulse along with bradycardia, non-measurable arterial blood pressure, and cardiac complications have been reported after myometrial injection of vasopressin. Here, we describe a patient with multiple uterine myomas who developed severe bradycardia, non-measurable blood pressure by non-invasive means and loss of peripheral pulse after myometrial injection of vasopressin at a total dose of 20 units (1 unit/ml) with documentation of severe peripheral arterial vasospasm and increased proximal blood pressure. The patient was successfully resuscitated.

INTRODUCTION

One of the major problems with a myomectomy is excessive bleeding from the abundant uterine blood supply. A local infiltration of vasopressin can significantly reduce the operative blood loss; however, it is not free of side effects and may sometimes cause lethal complications like bradycardia, arrhythmias, pulmonary edema, and cardiac arrest.[12] We herein report a case of sudden severe bradycardia and vasospasm immediately after a myometrial injection of vasopressin and discuss the potential adverse effects and related complications.

CASE REPORT

A healthy woman 43 years weighing 52 kg with multiple uterine fibroids was posted for open myomectomy. Physical examination was unremarkable with normal hematological, biochemical investigations, and echocardiogram. After arrival in the operation theater, the patient was monitored by three lead continuous electrocardiography (ECG), pulse oximetry and noninvasive automatic blood pressure monitor. Her baseline vital parameters were pulse of 84/min, blood pressure 120/82 mmHg, oxygen saturation 100%, and normal sinus rhythm on ECG. Intravenous line was sequred and preloaded with ringer lactate. Spinal anesthesia was given in the L3-L4 interspace and level of T6 was achieved with 3 ml of 0.5% Bupivacaine with 25 μg of Fentanyl. Surgery was started in supine position. Pulse was maintained between 72 and 76 and blood pressure 100-110 mmHg. Approximately 30 min after the subarachnoid block, patient's heart rate dropped to 28/min with ECG showing sinus bradycardia. There was intense facial pallor and radial pulse could not be felt though carotids were palpable. The pulse oximeter became flat. The next BP cycle did not register a value. Inj. atropine 0.6 mg was given intravenously, 100% oxygen was delivered using assisted ventilation and 100 ml of fluid was infused rapidly. So we checked the level of spinal anesthesia, the response to pinprick was equivocal at T4-T6. We inquired if any drug was injected in myometrium, surgeon told that she had injected 20 ml of 1 Unit/ml vasopressin intramyometrially after confirming negative aspiration of blood. Bradycardia and severe vasospasm occurred after 30 s of injecting vasopressin. Her tongue was pappery white and she complained of nausea and vomiting. Blood pressure was 216/144 mmHg. Single spray of nitroglycerin (NTG) was given sublingually within 1 min, pulse was increased to 120/min. Over the subsequent 25 min, pulse rate subsided to 90 /min and BP to 110/76 mmHg. Patient was comfortable with spontaneous respiration with 100% oxygen saturation. It was therefore decided to continue with surgery. Further surgery was uneventful. Surgery was completed and patient was shifted to recovery room and monitered there for 24 h.

DISCUSSION

Vasopressin has been documented to effectively reduce blood loss in gynecologic practice. Vasopressin, a direct vasoconstrictor, has been shown to control acute hemorrhage during a myomectomy. Local infiltration of vasopressin may cause lethal complications in spite of rarity of reported cases. Hung et al., described two cases of bradycardia followed by cardiac arrest and pulmonary edema after local infiltration of 6-10 ml of dilute vasopressin (2 units/ml) during an open myomectomy.[2] Zullo et al., also described a laparoscopic myomectomy complicated by bradycardia, followed by pulmonary edema and atrioventricular block, after the local injection of 10 ml of dilute vasopressin (2 units/ml).[2] Based on previous reports, Alexander GD, Brown M. recommended that the concentration of dilute vasopressin should be less than 0.05-0.3 units/ml to avoid lethal complications.. It is used in cardio-pulmonary resuscitation, hemorrhagic gastritis, burns, hemorrhagic cystitis, liver transplant, myomectomies, and cesarean section. Uterine myoma are rich in blood supply, and the possibility that such a large dose of vasopressin was accidently absorbed into the vessels could not be excluded. However, complex cardiovascular effects limit the use of vasopressin in physiological situations. Coronary vasoconstriction, altered vagal and sympathetic tone cause bradycardia, arrhythmia, reduced cardiac output and in severe cases myocardial ischemia and death. Cutaneous and peripheral vasoconstriction cause marked facial pallor and gangrene with large doses of vasopressin.[3]

Our patient exhibited all the vasoconsticting effects of vasopressin — intense pallor, bradycardia, absent radials and hypertension, only carotid pulses were palpable. Although low doses of intrauterine vasopressin have been used safely, hemodynamic complications during uterine myomectomy have been reported with doses exceeding 5 Units. Deschamps A and Krishnamurthy S described bradycardia and atrioventricular block with bigemmini after injecting 3 U of a 0.5 U /ml of vasopressin intramyometrialy.[4] Frishman suggested a routine intramyometrial dose of 2 units, with a maximum of 4-6 U to avoid hemodynamic complications.[5] The dose of vasopressin administered to our patient (20 U in 20 ml saline) substantially exceeded these recommended limits. Reflex bradycardia mediated by a strong vagal tone was caused by central hypertension, despite the absence of peripheral pulses. The effect of vasopressin in the circulation on the heart is mainly due to an increased vagal tone through the baroreflex mediated neurogenic regulation of blood pressure while the sympathetic tone and coronary flow are decreased.[1]

The equivocal response to pin-prick made us consider the possibility of high spinal anesthesia(T4). However, there was no bradycardia, hypotension or respiratory insufficiency prior to vasopressin. Moreover, persistent tachycardia and hypertension in the post injection phase, delayed ascent and rapid regression of pin prick response favored the diagnosis of adverse effects with vasopressin rather than high spinal anesthesia.

Close communication between the anesthesiologist and gynecologist is also important to identify and treat this rare complication, which can sometimes be induced by local infiltration of vasopressin.

CONCLUSION

Bradycardia induced by vasopressin infiltration has been described in such operations as myomectomy and cervical conization, the dose used should range from 0.05-0.3 units/ml and the total administered dose should be as small as possible. We recommend that careful monitering is essential for hemostasis of the uterus. In addition, close communication between the anesthesiologist and the gynecologist is also important to identify and treat this rare complication, which can sometimes be induced by the local infiltration of vasopressin.