Joseph B. Zwischenberger

Suppression of Shivering Decreases Oxygen Consumption and Improves Hemodynamic Stability during Postoperative Rewarming

Thirty-three patients undergoing elective myocardial revascularization were prospectively randomized into two study groups (Group S and Group P) to permit evaluation of the effects of shivering on oxygen consumption per minute (VO2), carbon dioxide production per minute (VCO2), and hemodynamic performance. Group S was allowed to shiver during the postoperative rewarming period, and Group P received hourly injections of pancuronium bromide and Metubine (metocurine) sulfate with sedation to block the shivering response. Group S demonstrated significantly higher increases in VO2 and VCO2, lower systolic blood pressure and mixed venous oxygen saturation, and a greater use of inotropic support than the patients in Group P. Suppression of the shivering response minimized increases in VO2 and VCO2, improved hemodynamic stability, and resulted in a decreased need for inotropic support.

Prolonged extracorporeal life support of pediatric and adolescent cardiac transplant patients

Options for mechanical support of pediatric patients with severe heart failure who are awaiting transplantation or have undergone transplantation are limited. This report examines 3 patients placed on extracorporeal life support (ECLS) while awaiting transplantation and 3 patients who underwent transplantation and suffered subsequent heart failure due to rejection or postoperative myocardial dysfunction. The overall survival rate was 2 of 6. The 2 surviving patients had a failing transplanted heart. There were no survivors among the patients placed on ECLS as a bridge to transplantation. In each case a contraindication to transplantation developed before a donor heart could be obtained. The mean time of ECLS support was 147.5 hours (range, 70 to 370 hours). The ECLS circuit did not affect cyclosporin levels or antirejection therapy. Extracorporeal life support can be used to support pediatric cardiac transplant patients with biventricular failure due to acute rejection or postoperative dysfunction. Although the results have been discouraging, ECLS may still have a role as a bridge to transplantation. However, complications can develop during ECLS that may preclude transplantation.

Independent measurement of oxygen consumption and oxygen delivery.

This experiment investigated the relationship between oxygen consumption and oxygen delivery (cardiac output X arterial oxygen content) in an acute canine model. Previous studies investigating this relationship have largely utilized methods in which oxygen consumption and oxygen delivery were each calculated using the same measured variables resulting in mathematical coupling of variables. In this study, oxygen consumption was measured directly by closed-circuit spirometry. Oxygen delivery was independently controlled using right atrial bypass. These techniques assured that the values for oxygen consumption and oxygen delivery were derived entirely independently. In our study using 11 dogs, we found that oxygen consumption was constant and independent of oxygen delivery at oxygen delivery levels greater than 8.0 cc/kg/min (normal canine oxygen delivery 20-25 cc/kg/min). Oxygen consumption was linearly related to oxygen delivery at oxygen delivery levels less than or equal to 8.0 cc/kg/min. Below this critical level of oxygen delivery, animals were more acidotic and hypotensive than at higher delivery levels.

Method of pulmonary and membrane lung gas exchange measurement during extracorporeal membrane oxygenation.

A method for measuring simultaneous MemL and NatL gas exchange during neonatal ECMO has been described. Closed-circuit spirometry techniques were used for both measurements. This technique demonstrated minimal pulmonary gas exchange at low airway pressures prior to pulmonary recovery and measured the gas exchange of metabolism in these critically ill neonates.

Rapid technique of occlusion of the venae cavae for total cardiopulmonary bypass during repeat cardiac operations.

A new technique of occlusion of the venae cavae utilizing a cannula with an inflatable balloon cuff is described.