This patient should undergo pericardiocentesis. He has low-pressure cardiac tamponade, which is tamponade occurring in the setting of clinical dehydration. Evidence of cardiac tamponade on echocardiography includes diastolic inversion of the right-sided chambers and respiratory variation in the mitral inflow pattern; a ventricular septal shift and plethora of the inferior vena cava also may be present. However, because of volume contraction, the intracardiac filling pressures are low, and tamponade does not result in an elevation of estimated central venous pressure. Therefore, several physical examination findings usually associated with pericardial tamponade, such as jugular venous distention and pulsus paradoxus, may not be evident in many patients. Low-pressure cardiac tamponade may be caused by malignancy, tuberculosis, or other severe chronic illnesses that result in both dehydration and pericardial effusions, with metastatic involvement of the pericardium likely present in this patient with known disseminated cancer.

In cardiac tamponade, the pericardial effusion causes intrapericardial pressure to exceed ventricular diastolic pressures, which leads to impairment in ventricular filling and stroke volume. Sinus tachycardia, as evident in this patient, is a compensatory response to maintain forward cardiac output. Treatment should consist of acute intravenous hydration to augment ventricular preload and stroke volume and, most importantly, procedures to relieve the tamponade, specifically pericardiocentesis.

An intra-aortic balloon pump is used in patients with hemodynamic instability, usually as a bridging device until definitive treatment can be undertaken. Because removal of pericardial fluid in this patient would be expected to markedly improve his hemodynamic status, pericardiocentesis is indicated prior to pursuing additional supportive therapy.

Phenylephrine is a potent vasoconstrictor. Although phenylephrine may improve this patient's blood pressure by increasing his systemic vascular resistance, the increase in resistance will reduce stroke volume, which is already significantly impaired by tamponade and hypovolemia. Phenylephrine, therefore, would not be an appropriate intervention prior to treating the tamponade and ensuring adequate volume expansion.

A window pericardiectomy procedure is performed in the operating room either as an open procedure or using video-assisted thoracoscopy by cardiac surgery and would be indicated only if this patient's tamponade was unresponsive to pericardiocentesis, a less invasive bedside procedure.