Refractory hypotension during paraganglioma removal - do we have to worry?

Sir,

Pheochromocytoma and paraganglioma removal may be associated with severe hypotension and hypoglycaemia. Hypotension after tumour removal is usually responsive to fluid therapy and vasopressor infusions. Prolonged and refractory hypotension can thus be a concern as it may not only result in tissue hypoxia leading on to organ dysfunction and/or failure, but also result in post-operative bleeding if haemostasis cannot be checked at normal blood pressures prior to surgical closure. We recently encountered a patient with severe and refractory hypotension during paraganglioma removal who did not respond to fluid therapy and high dose multiple vasopressor infusions. The abdomen was closed at extremely low blood pressures. However, no complications occurred.

The patient, a 51-year-old male was incidentally detected to have a retro-caval mass. Elevated urinary catecholamines and their metabolites (nor-epinephrine-536.5 μg/day, vanillylmandelic acid 59.2 μg/day) and a metaiodobenzylguanidine scan confirmed diagnosis of 8 cm, inter aorto-caval paraganglioma. Pre-operative antihypertensive therapy included prazosin, amlodipine, and metoprolol for 12 days, and the blood pressure was fairly well controlled. An open surgical removal of lesion was planned. A large bore venous cannula, arterial catheter in left radial artery, and epidural catheter in lower thoracic inter-spinous space were inserted. Anaesthesia was induced with propofol and fentanyl. Atracurium was used for muscle relaxation. A triple lumen central venous catheter was inserted through the right internal jugular vein. Intra-operative hypertensive spikes were managed with a sodium nitroprusside infusion and intravenous boluses of diltiazem and metoprolol. Analgesia was provided with 3 mg of morphine in 15 ml of 0.1% bupivacaine given through epidural catheter. After tumour isolation, the mean arterial pressure (MAP) decreased to below 60 mmHg and the central venous pressure (CVP) came down to 7-8 mmHg. Around 1.5 L of crystalloids were infused over next 10 min to increase CVP to 10-12 mmHg. Nor-epinephrine infusion was titrated up to 20 mcg/min. The MAP, however, remained below 60 mmHg. Other vasopressors including dopamine, epinephrine, phenylephrine, and later dobutamine and vasopressin were sequentially started over the next 40 min without any improvement. Hydrocortisone and calcium were given intravenously. Blood loss during surgery was around 1 L and 700 ml of packed red blood cells was infused. The patient's arterial blood gas analysis showed a pH of 7.25 with base deficit of 7.6 mmol/L and lactate of 4.2 mmol/L. After waiting for almost 30 min for MAP to improve, the abdomen was closed at a systolic blood pressure of 60 mmHg.

The patient was shifted to the Intensive Care Unit (ICU) without reversal of anaesthesia and all infusions were continued. After about an hour, MAP started to improve and vasopressor and inotropic support were slowly tapered and withdrawn over the next 3-4 h [Figure 1]. During this time his trachea was also extubated. The rest of the ICU and hospital stay were uneventful and no post-operative complications were noted.

Figure 1

Intraoperative and post-operative haemodynamic parameters of patient. Bold arrow shows time at which tumour was isolated. SBP – Systolic blood pressure in mm Hg, DBP - Diastolic blood pressure in mmHg, HR – Heart rate in beats per minute, CVP – Central venous pressure in mmHg

The incidence of hypotension after pheochromocytoma and paraganglioma removal varies between 20% and 77%.[1] Chronically-elevated plasma catecholamine levels in the pre-removal phase leads to the down regulation of alpha and beta-receptors. Exogenously infused vasopressors acting via adrenergic receptors will therefore not result in the anticipated rise in blood pressure.[2] Higher than normal doses of vasopressors may be required. Hypotension not responding to nor-epinephrine and epinephrine but counteracted by vasopressin which acts via non-alpha receptors has been previously described in literature.[34] Hypotension in our patient was, however, refractory to high doses of multiple vasopressors and inotropes, including vasopressin [Figure 1]. The total sodium nitroprusside (12.5 mg), diltiazem (10 mg) and metoprolol (10 mg) used intraoperatively were also well within the recommended doses and, thus, rules out toxicity by these agents.

Use of phenoxybenzamine preoperatively,[5] catecholamine-induced myopathy,[6] and adrenal insufficiency[7] have also been postulated as causes of severe post-operative hypotension after pheochromocytoma removal. Our patient, however, was on prazosin, had a normal pre-operative echocardiography study and underwent no adrenal manipulation. Despite persistently low blood pressure for 4-5 h, blood gas analysis showed only a mild metabolic acidosis (base deficit-7.6 mmol/L), which was probably due to adequate volume status and did not lead to any organ dysfunction later in the course of ICU stay.

In conclusion, this report describes unusually refractory and severe hypotension in a patient after paraganglioma removal which did not lead to signs of organ hypo-perfusion or rebound post-operative surgical bleeding. Knowing that such incidents can occur with no untoward patient outcome will help surgeons and critical care specialists manage and counsel their patients appropriately.

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