Anaesthetic Implications of Severe Hyperthyroidism Secondary to Molar Pregnancy: A Case Report and Review of Literature

Abstract

Pregnant women with gestational trophoblastic disease have an increased likelihood to develop hyperthyroidism secondary to increased secretion of human chorionic gonadotropin. Most of these cases of hyperthyroidism remain undiagnosed and may present as a thyrotoxic crisis during the perioperative period. Pregnant patients with gestational trophoblastic disease should be always evaluated for hyperthyroidism, and in cases of severe hyperthyroidism, antithyroid treatment should be initiated before evacuation of the mole. Anesthetic management of these cases is challenging in view of the emergency nature of the surgery and potential for thyroid crisis. Spinal anesthesia can be safely administered and has a protective role in preventing thyroid crisis.

INTRODUCTION

Severe hyperthyroidism is one of the rare features of molar pregnancy. The condition usually occurs in patients with advanced untreated disease due to massive secretion of human chorionic gonadotropin (HCG). HCG has thyrotrophic activity because of structural similarity to thyroid-stimulating hormone (TSH).[1,2] Anesthetic management of these cases is challenging because of risk of intraoperative thyroid storm and high-output cardiac failure. We like to report a case of advanced molar pregnancy with severe hyperthyroidism posted for suction and evacuation.

CASE REPORT

A 20-year-old primigravida at 17 weeks of gestation was admitted to our hospital with a history of spotting per vagina for 15 days and intermittent pain abdomen for the past 2 months There was no history of passage of clots or vesicles. Clinical examination revealed pallor, tachycardia with heart rate of 124/min, and hypertension with blood pressure (BP) of 140/98 mmHg. The uterus was around 20 weeks size. Pelvic ultrasonography revealed a large heterogeneous soft-tissue lesion measuring 6.9 cm in the endometrial cavity with the classical “Snow Storm appearance,” suggestive of complete molar pregnancy. Her blood investigations revealed a hemoglobin of 7 g% on admission, Serum beta-HCG was elevated and found to be >2 lac mIU/L. Thyroid function test showed elevated thyroid hormone levels serum T3 level of 347 pg/dL, serum T₄22.9 ng/L, and TSH <0.01 μ/L. Electrocardiogram (ECG) revealed sinus tachycardia.

Suction and evacuation of the mole was planned. Since the patient had features of severe hyperthyroidism, it was decided to optimize the patient preoperatively before the procedure. In consultation with endocrinologist, she was treated with tablet propranolol 40 mg b.d., antibiotics, and supportive care. During the treatment, the patient developed intermittent high-grade febrile spikes with temperature up to 103°F and two episodes of vomiting, 4 days after start of treatment patient was posted for evacuation of the mole.

Preoperatively, the patient had a heart rate of 100 bpm and BP 130/80 mmHg and SpO₂ of 100% in room air. Intraoperative monitoring included ECG, SpO₂, end-tidal CO₂, noninvasive BP, and temperature. Subarachnoid block was administered with bupivacaine 0.5% 2 ml with 25 μg fentanyl as an additive. Vital parameters remained stable during the intraoperative period. One unit of the packed red blood cells was transfused during the procedure in view of anemia and intraoperative blood loss of 500 ml.

The patient had febrile spikes for 2 days postprocedure during which time propranolol was continued. All the features of hyperthyroidism resolved within 2 days of hydatidiform mole evacuation. A repeat thyroid function test 2 weeks later showed results within normal limits, and the beta hCG level dropped down to 82,085 after 48 h of evacuation.

DISCUSSION

The association of hyperthyroidism secondary to molar pregnancy is a rare but recognized clinical entity. Hyperthyroidism occurs in advanced untreated molar pregnancies with high titers of beta HCG because of structural similarity of beta HCG and TSH and the resultant thyrotropic activity of beta HCG.[1,2] Diagnosis of the condition in the preoperative period is important because several reports of intraoperative thyroid storm and high-output cardiac failure had been reported secondary to thyrotoxicosis.[3,4,5,6] Hence, optimization of the thyroid status and control of the hypermetabolic status is necessary before surgery to prevent this complication. Treatment has to be individualized. Some patients may require only beta blockers while others may require in addition antithyroid medications, steroids, and lugols iodine. Soutter and Norman et al. reported two cases of metastatic carcinoma complicated with thyrotoxicosis, leading to cardiac failure in one patient and severe thyroid crisis in other. They managed the patients with iodide and beta blockers and recommended routine prophylaxis for high-risk patients, using propylthiouracil, oral iodide, and propranolol[3] In another case reported by Khanna et al., a patient with gestational trophoblastic disease was managed with methotrexate, antithyroid drugs, steroids, and beta blockers for 3 weeks before being taken up for surgery.[4] A case of rapid preparation before surgery by plasmapheresis has also been reported.[7,8] We preferred to treat with beta blockers since the patient came at an advanced stage and less time available for preoperative optimization. Beta blockers provide rapid optimization when compared to other antithyroid drugs.[9] Propranolol inhibits sympathetic overactivity, prevents the peripheral conversion of T₄ to T₃ and also reduces the fall in systemic vascular resistance that may occur in these cases, thereby preventing high-output cardiac failure. Various other complications that have been reported during the perioperative period include hypertension, embolization of pulmonary arteries by trophoblastic materials, hypovolemia, disseminated intravascular coagulation, and pulmonary edema.[4]

Various anesthetic techniques are reported in the literature for the management of these patients, including general anesthesia,[5] spinal anesthesia,[9,10] and combined spinal-epidural.[11] Erturk et al. reported the management of a woman with 12 weeks of gestation with molar pregnancy with hyperthyroidism. The case was conducted under total intravenous anesthesia using propofol, remifentanil, and esmolol infusion for controlling sympathetic hyperactivity during surgery.[12] The choice of anesthesia also needs to be individualized. The major goals during the anesthetic management include perioperative prevention of thyrotoxic crisis and control of overt sympathetic response secondary to hyperthyroidism. In patients with active bleeding and severe hypotension, general anesthesia is preferred to maintain hemodynamic stability. However, volatile agents including halothane, isoflurane, sevoflurane, and desflurane cause uterine relaxation and may increase bleeding and hence may have to be used in lower concentrations. In addition, laryngoscopy in patients with hyperthyroidism may precipitate hypertensive crisis.

In the above case, subarachnoid block was preferred for the procedure because the patient was hemodynamically stable. Spinal anesthesia has several advantages over general anesthesia. It is nontocolytic and safe in hyperthyroidism.[9] Spinal anesthesia also enables earlier detection of a complication such as thyroid storm and cardiorespiratory distress. Judicious use of intravenous fluids and blood is essential since patients have potential to develop pulmonary edema.

CONCLUSION

Hyperthyroidism should always be excluded in patients with advanced trophoblastic diseases and preoperative treatment of severe hyperthyroidism with multidisciplinary approach involving anesthesiologists, obstetricians, and endocrinologists necessary to prevent perioperative complications. Spinal anesthesia may be safely administered and has several advantages to protest against thyroid storm provided hemodynamic stability is maintained.

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Conflicts of interest

There are no conflicts of interest.