To the Editor, We present an unusual cause of tamponade-like presentation in a patient undergoing anesthesia. We briefly discuss the related pathophysiology and the need for vigilance in maintaining a broad differential diagnosis for critical events occurring in the operating room (OR). The patient gave written consent for publication of this report. A 76-yr-old male presented to hospital with sudden acute onset of abdominal pain and nausea. He was hemodynamically stable in the emergency department where blood tests revealed an elevated lactate level (3.4 mmoL L). Computed tomography of the patient’s abdomen showed a left diaphragmatic hernia defect and small bowel herniation. He was treated with antibiotics and fluid resuscitation by the surgical team while a plan for surgery was being formulated with the concern for potential bowel ischemia. The patient’s condition acutely deteriorated on the surgical floor. He developed increasing oxygen requirements and became hypotensive. Repeat investigations showed a serum lactate of 10.5 mmoL L with a blood pH of 7.19. The patient was transferred to the OR for emergency exploratory laparotomy and possible left thoracotomy for reduction of a suspected incarcerated paraesophageal hernia with bowel ischemia. On initial examination outside the OR, the patient was in obvious respiratory distress on 15 L oxygen with a nonrebreathing mask, and there were visible signs of air hunger with oxygen saturations in the 80’s. He was immediately transferred into the OR, and aggressive fluid resuscitation was initiated while preparing to secure the patient’s airway emergently. Rapid sequence induction was performed with propofol 30 mg iv, succinylcholine 120 mg iv, and tracheal intubation. The patient remained hypotensive with a systolic blood pressure of approximately 80 mmHg and a heart rate of 120 beats min despite fluid resuscitation. The initial central venous pressure (CVP) was 20 mmHg, and the peak airway pressures reached 40 cm H2O. An epinephrine infusion was initiated at a rate of 0.1 lg kg min. As surgery progressed and proceeded from a laparotomy to a thoracotomy, there was an audible decompression of the herniated bowel from the chest with an immediate resolution of the high airway pressures, tachycardia, and elevated CVP. The patient’s blood pressure and heart rate normalized, his urine output improved, and he was able to be weaned from the epinephrine infusion. The patient tolerated the remainder of the procedure well, and he was transferred to the intensive care unit. Subsequent review of his immediate preoperative chest x-ray showed left chest opacification and bowel herniation with right mediastinal shift (Fig. 1). The pathophysiology of this case can best be described as the patient having an incarcerated ischemic bowel in the chest producing cardiac compression and tamponade-like physiology. Reduction of the herniated bowel resulted in the immediate resolution of the patient’s hemodynamic instability. The patient’s postoperative chest x-ray showed resolution of the mediastinal shift (Fig. 2). Cardiac tamponade is a life-threatening slow or rapid compression of the heart due to the pericardial accumulation of fluid, pus, blood, clots, or gas resulting from effusion, trauma, or rupture of the heart. In this case, we believe that the incarcerated bowel became ischemic and edematous, causing extrinsic compression and displacement of the heart and resulting in cardiogenic shock. The x-ray of the patient at original presentation to the hospital K. J. McKeown, MD (&) W. Sischek, MD University of Western Ontario, London, ON, Canada e-mail: kevin.mckeown@utoronto.ca