We report a 34-year-old woman with secondary hypertension diagnosed with a left-sided phaeochromocytoma. Excision of the tumour resulted in recurrent hypoglycaemia up to 6 days post-operatively. We discuss the pathogenesis of hypoglycaemia following removal of the tumour and put forward hypothesis for the recurrent hypoglycaemia.
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Phaeochromocytoma is a not uncommon cause of secondary hypertension and treatment consists of surgical excision. Transient hypoglycaemia has been reported previously after removal of the tumour. We report a patient with recurrent hypoglycaemia up to 6 days post-operatively, who required monitoring and glucose infusion for a prolonged period. So far, no reports of recurrent hypoglycaemia have been published in the literature. In this case report we highlight the need for prolonged monitoring of patients following surgical excision of a phaeochromocytoma.
A 34-year-old-woman presented with headache, giddiness, palpitations, excessive sweating and chest pain for 6 months. Hypertension was diagnosed just prior to admission by her general practitioner but she was not commenced on treatment. Examination revealed an anxious tense woman, supine blood pressure (BP) 160/120 mmHg and lower limb BP 170/130 mmHg. There were no café-au-lait spots, neurofibromas or neurocutaneous lesions. Abdominal, respiratory and cardiovascular system examination and fundi were normal. There was no bruit over the renal arteries. She did not have a goitre. With a clinical diagnosis of phaeochromocytoma, the patient was investigated. Full blood count, renal function, serum calcium, electrolytes, fasting blood glucose, thyroid function tests, electrocardiogram and chest X-ray were normal. Urinary catecholamines was 200 μg/24 h (normal 100–150 μg/24 h) and vanillyl mandelic acid was 24.15 mg/24 h (2.5–5 mg/24 h). Abdominal ultrasound revealed a left-sided suprarenal lesion measuring 6 × 6 × 5 cm with no masses along the sympathetic chain. The patient was commenced on phenoxybenzamine 10 mg 6-hourly and propranolol 40 mg bid. Pre-operatively her BP was 130/90 mmHg.
The patient underwent surgery under cover of intravenous sodium nitroprusside and propranolol. A left-sided suprarenal tumour was removed and histology confirmed a phaeochromocytoma. There were no complications during surgery and blood loss was average. Intra-operatively she received 1.5 l of 5% dextrose and one unit of blood.
Two hours post-operatively, the patient lapsed into a stuporous state and on investigation her blood glucose was 1.1 mmol/l. She was given an immediate intravenous infusion of 50 ml 50% dextrose and she improved. She was started on 10% dextrose infusion with 50 ml 50% dextrose bolus every 4 hours. On the third day, oral feeds were introduced and intravenous fluids were discontinued. Three hours later she became unresponsive and her blood glucose was 1.2 mmol/l. She was recommenced on a continuous infusion of 10% dextrose after a bolus of 50% dextrose. On the sixth day she had a third episode of hypoglycaemia (blood glucose 1.3 mmol/l) when the dextrose infusion was stopped, which was recommenced and continued for a further 48 h and then discontinued (figure). She did not have further episodes of hypoglycaemia in hospital. Insulin assays were in the normal range but at the time of blood sampling she was normoglycaemic. She was followed up regularly over the next 18 months and had not suffered further hypoglycaemic episodes. A prolonged fast and abdominal ultrasound done at follow-up were normal.
This is the first case of recurrent hypoglycaemia following surgical removal of a phaeochromocytoma. Transient hypoglycaemia (within 12 hours) has been reported previously in the literature.1 2 Various metabolic factors give rise to hypoglycaemia after this surgery. Adrenaline infusion has been shown to inhibit insulin secretion and stimulate glucagon secretion in normal subjects.3 4 Sudden withdrawal causes reversal of these effects and a rebound hyperinsulinaemia inappropriate to the prevailing blood glucose concentration. Previously, it has been suggested that endogenous insulin secretion is suppressed by the increased circulating catecholamines in patients with phaeochromocytoma, and that excessive rebound secretion of insulin occurs after the removal of the tumour.2 In addition, prolonged exposure to adrenaline may delay the recovery of the hypoglycaemic response to glucagon. Hyper-catecholaemia depletes liver glycogen and inhibits glucose uptake, thus impairing the body's response to hypoglycaemia.5 These factors may explain the occurrence of transient hypoglycaemia after removal of phaeochromocytoma.
Insulinoma is a possible cause for recurrent hypoglycaemia but insulin assays were normal in our patient and after the sixth day she did not have further episodes of hypoglycaemia. Furthermore, she did not develop hypoglycaemia during prolonged fast and in the 18 months follow-up after surgery she was healthy and doing well, which probably excludes insulinoma as a possible cause for her recurrent hypoglycaemia in the immediate post-operative period. Other possible explanations for the hypoglycaemia are:
the dextrose infusions given to the patient in the post-operative period were insufficient to replenish the depleted glucose and glycogen stores in the liver resulting from a prolonged hyper-catecholaemic state
catecholamine levels in the body may remain elevated for up to a week post-operatively6
phaeochromocytoma is an uncommon cause of secondary hypertension
transient hypoglycaemia is known to occur after surgical excision of a phaeochromocytoma
recurrent hypoglycaemia after surgery may also occur
all patients undergoing surgical excision of a phaeochromocytoma must be monitored for a prolonged period (eg, 7 days) to prevent the complications of hypoglycaemia
Patients undergoing major surgery are monitored in high-dependency or intensive-care units and are usually on narcotic analgesics, as a result of which they may be drowsy. They could also be drowsy as a result of the anaesthesia itself. In such patients hypoglycaemia may be missed unless it is specifically looked for. Therefore, there must be increased awareness of the possibility of hypoglycaemia in patients undergoing removal of a phaeochromocytoma. In addition, these patients may have further hypoglycaemia up to a week post-operatively. The cause of recurrent hypoglycaemia needs further investigation, but meanwhile such patients must be monitored for up to a week to avoid the complications of hypoglycaemia.