Pheochromocytomas are rare neuroendocrine tumors secreting high levels of catecholamines that produce highly variable clinical signs and symptoms. Although hypertension, tachycardia, pallor, headache, and anxiety usually dominate the clinical presentations, gastrointestinal manifestations, such as nausea, abdominal pain, and chronic constipation, are also reported in 20–40% of patients with pheochromocytoma [1, 2]. Gastrointestinal pseudo-obstruction, which differs from mechanical ileus in that there is no demonstrable blocking lesion, is a rare and relatively unknown but potentially life-threatening complication of pheochromocytoma. Osinga et al. report, in a review that describes 34 cases of pseudo-obstruction associated with pheochromocytoma and paraganglioma in 32 publications, that 5 patients (15%) developed bowel perforation and 16 patients (47%) died within 1 year after the development of the condition [7]. Its pathophysiology can be a direct consequence of the elevated catecholamine levels that reduce the peristalsis of the gastrointestinal tract. Gastrointestinal activity is controlled by the parasympathetic and sympathetic nervous systems. The activation of the parasympathetic nervous system causes acetylcholine release, which stimulates muscarinic receptors and leads to bowel movement. In contrast, activation of the sympathetic nervous system releases noradrenaline, which inhibits bowel motility through activation of the α1-, α2-, and β2-adrenergic receptors. The activity of the sympathetic nervous system is further augmented by a presynaptic noradrenaline-mediated inhibition of parasympathetic acetylcholine release. In addition, circulating catecholamines can not only inhibit gastrointestinal peristaltic activity through stimulation of β2 receptors but also cause intestinal vasoconstriction and ischemia through stimulation of α1 and α2 receptors [4, 8, 9].
The first-line treatment for pheochromocytoma-associated gastrointestinal pseudo-obstruction is a conservative approach, which includes fasting, nasogastric suction, and intravenous replacement of fluids and electrolytes. If initial treatment is not successful, endoscopic desufflation and pharmacological treatment should be considered. Some reports suggest the use of nonselective α blockers, such as phentolamine or phenoxybenzamine, for the treatment of gastrointestinal complications of pheochromocytoma [7]. However, neither phentolamine nor doxazosin was effective for our patient. The ultimate therapy is surgical removal of the pheochromocytoma. Although there are some reports about surgical treatment, anesthetic considerations are scarcely described, and as far as we know, this is the first description of the anesthetic management of gastrointestinal pseudo-obstruction as a complication of pheochromocytoma.
From the pathophysiological characteristics of gastrointestinal pseudo-obstruction, we reasoned that inhibition of the gastrointestinal sympathetic system perioperatively by epidural infusion of local anesthetics would be advantageous for the patient to promote intestinal peristalsis. In addition, epidural analgesia would be beneficial in terms of avoiding postoperative opioid administration, which inhibits intestinal peristalsis by activating intestinal μ receptors [9]. Although the postoperative pain of our patient was well-controlled without using opioids, the anticipated effect of improved bowel movement was not apparent. One of the reasons for this could be attributed to the very short duration of epidural infusion of local anesthetics postoperatively. However, on the grounds that many factors, e.g., perioperative fluid infusion and inflammation, can influence bowel movement in an early postoperative period, it is impossible to determine whether the epidural infusion had little effect on our patient or the other factors overwhelmed it. Longer use of epidural infusion might have had an effect on intestinal peristalsis; however, we have no evidence to prove it. Another possibility can be maldistribution of adrenergic receptors, which should be affected by over-secreted catecholamines due to pheochromocytoma and would recover gradually postoperatively, which might be consistent with our patient’s recovery time course. But again, we have no way to prove it.
In conclusion, this case report illustrates the anesthetic consideration of intestinal pseudo-obstruction induced by pheochromocytoma. From a pathophysiological point of view, epidural anesthesia may be promising in terms of promoting intestinal peristalsis postoperatively by inhibiting the sympathetic system; however, in our patient, a beneficial effect was not apparent.