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Methemoglobinemia is an uncommon cause of tissue hypoxemia that can be life-threatening if not promptly identified and treated. It can occur after exposure to an oxidizing agent from contaminated well water or from nitroglycerin, sodium nitroprusside, or certain local anesthetics. During oropharyngeal use of topical anesthetics for transesophageal echocardiography, systemic drug uptake is unpredictable and unexplained complications can ensue. Treatment of acquired methemoglobinemia may require methylene blue, as oxygen is not usually sufficient. Avoidance of the oxidizing agent, probably benzocaine in the cases presented, is prudent.

Study Objectives: To investigate the changes in hemodynamic profile during cardiopulmonary bypass, and determine the effect of intravenous (IV) heparin on serum chemistry and acid-base status., Design: Prospective study., Setting: Three Canadian hospitals., Patients: 43 consecutive patients undergoing elective aortocoronary bypass., Interventions: Anesthetic technique was standarized. Hemodynamic profile, blood gases, and serum electrolytes were measured immediately before IV heparin for cardiopulmonary bypass, and 5 minutes after., Results: Mean arterial pressure (MAP) decreased by a mean of 11.2 mmHg (12.5%, p = 0.0001) in all patients, of whom 28% were treated with vasoactive drugs to restore MAP. Mean systemic vascular resistance decreased by 418 dyne sec/cm(5) (25%, p = 0.0001), and mean serum potassium increased by 0.14 meq/L (p = 0.0002). The reduction in MAP correlated strongly with the reduction in SVR (p = 0.004), but not with changes in potassium or other variables., Implications: Mean arterial pressure is significantly affected by IV heparin for cardiopulmonary bypass. The hemodynamic mechanism is systemic vasodilation, implying that treatment with a short-acting vasoconstrictor is appropriate, if necessary. Unlike earlier studies, the increase in serum potassium observed, although reproducible, was trivial.

Traumatic lung herniation is an unusual clinical problem. This case report describes a morbidly obese individual who sustained significant chest trauma in a motor vehicle accident. Lung herniation was noted at the time of delayed respiratory failure necessitating ventilation. The significance of the lung hernia in this patient's respiratory failure is uncertain. The lung hernia was repaired surgically to relieve pain, prevent incarceration, and optimize respiratory function. After a brief period of postoperative ventilation, the patient recovered markedly and has been well since.