Wilms’ tumor with hyperreninemia produces vasoconstriction and fluid retention that leads to sustained hypertension, and patients can develop lethal congestive heart failure [10]. In our infant, milrinone and diuretics were used for congestive heart failure in the ICU. However, her hypertension could not be controlled, and we needed a calcium-channel blocker and angiotensin-converting enzyme inhibitor. For many years, several drugs have been used to treat hypertension associated with Wilms’ tumor [10]. Previous reports indicated that an angiotensin-converting enzyme inhibitor (e.g., captopril), angiotensin II analog (e.g., saralasin), or angiotensin II receptor antagonist (e.g., losartan) were administered to control severe hypertension in patients with Wilms’ tumor [8, 11, 12]; however, these drugs had limited ability to control hypertension. Since we needed to optimize antihypertensive therapy in our patient, we used clonidine, an α2-adrenergic receptor agonist, to achieve light sedation. Surprisingly, this sedation decreased the blood pressure of the infant. We speculate that any sedative may be useful for the management of hemodynamic stability in combination with antihypertensive drugs, such as angiotensin-converting enzyme inhibitors. Our preoperative medical management to achieve hemodynamic stability contributed to stable anesthetic induction and maintenance of the patient.
In our anesthetic management, small hemodynamic changes occurred before and after tumor resection. The blood pressure slightly increased despite gentle handling of the tumor and decreased after resection, regardless of the blood loss and the depth of anesthesia. These changes are similar to those that occur with surgical resection of pheochromocytoma. Charlton et al. demonstrated that infusions of phentolamine, phenoxybenzamine, and sodium nitroprusside were useful for intraoperative control of blood pressure associated with Wilms’ tumor [6]. Alpha-adrenergic blockade is actually used in surgery for pheochromocytoma resection [13]. We could have used these drugs for the management of blood pressure in our surgery. With regard to the small decrease in blood pressure, intermittent mechanical compression of the inferior vena cava by the surgeon may induce hypotension. Another possible explanation is that hypovolemia from hemorrhage and downregulation of angiotensin receptors contribute to hypotension. This possible mechanism is consistent with the observation that hemorrhage and downregulation of α- and β-adrenergic receptors induce hypotension after pheochromocytoma resection [13]. However, we did not measure the concentrations of renin, angiotensin I, angiotensin II, and aldosterone during surgery before or after tumor resection. The underlying mechanism of hypotension in our infant remains unknown.
In neonates and infants, the myocardium has less contractile force than in adults because of the less compliant ventricles [14]. This developmental immaturity of the heart accounts for their sensitivity to volume loading and poor tolerance of increased afterload. In our patient, the myocardium was continually remodeled by hypertension with hyperreninemia, and there was a tendency toward heart failure in utero and throughout her life. As mentioned above, the preoperative hemodynamic control (i.e., decreased preload and afterload) contributed to the improvement in cardiac function. We speculate that she was hypovolemic just before surgery because of the medications given to treat heart failure. However, we did not accurately evaluate intravascular volume before and during the surgery, in part because the clinical assessment of hemodynamic status based on routine monitoring or goal-directed fluid therapy by measuring aortic blood flow is limited in pediatric patients [15]. In this case, it might have been possible to use transesophageal echocardiography or non-invasive cardiac output monitoring by electrical velocimetry for precise hemodynamic control [16]. However, their usefulness in infants is still controversial.
In this case, the stage of the Wilms’ tumor was low grade, and the infant has a good prognosis. The National Wilms’ Tumor Study Group in the USA recommends five classifications (stage I–V) for Wilms’ tumor [10]. Importantly, when the stage of the tumor was higher than stage III, intravascular extension into the inferior vena cava with thrombosis frequently occurred [17]. Anesthetic management in patients undergoing Wilms’ tumor resection is of major concern. Anesthesiologists should consider the presence of pulmonary embolism, obstruction of the vena cava, or obstruction of the tricuspid valve [18]. Transesophageal echocardiography may be useful to evaluate intravascular extension during the perioperative period if the stage of the tumor is advanced.
This case report indicates that optimized preoperative hemodynamic control and sedation produce stable anesthetic management during surgery in the pediatric patient with severe heart failure associated with Wilms’ tumor.
