Improved myocardial function using cardiopulmonary support in resuscitation for hemorrhagic shock.

OBJECTIVES: To clarify the pathophysiologic characteristics of hemorrhagic shock and to assess methods of resuscitation. DESIGN: An animal experiment using sheep subjected to hemorrhagic shock and fibrillation to compare various resuscitation techniques. SETTING: An experimental laboratory setting meant to simulate hemorrhagic shock secondary to trauma. STUDY GROUPS: Group 1 animals (n = 6) were controls that were not subjected to shock and fibrillation. Group 2 animals (n = 6) were subjected to shock and fibrillation and were resuscitated with volume replacement. Group 3 animals (n = 6) were also subjected to shock and fibrillation but were resuscitated with epinephrine hydrochloride infusion. Group 4 animals (n = 6) were subjected to shock and fibrillation but were resuscitated with cardiopulmonary support. INTERVENTIONS: The shock was to a mean arterial pressure of 25 mm Hg for 1 hour followed by 5 minutes of fibrillation. Group 2 animals were resuscitated for 1 hour. Group 3 animals were supported for 6 hours on epinephrine after the shock period. Group 4 animals were supported for 1 hour on cardiopulmonary support, then were observed for another 5 hours. All animals were sedated and intubated, and a median sternotomy was performed. MAIN OUTCOMES MEASURED: Survival, hemodynamic function, lactate production, myocardial blood flow, and water content. RESULTS: Group 1 sheep showed no detrimental effects in any of the measured variables. Group 2 sheep could not be resuscitated. Group 3 sheep could be supported with epinephrine but had a 60% depression in left ventricular function and an ultimately high mortality rate (67%) when the infusion of epinephrine was discontinued. Group 4 sheep had a 100% survival rate and only a 20% deterioration in left ventricular function. CONCLUSIONS: Cardiopulmonary support improves survival and preserves left ventricular function compared with volume resuscitation with or without inotropic support in this model of hemorrhagic shock.

Use of Carmeda-coated femoral-femoral bypass during repair of traumatic aortic pseudoaneurysms.

OBJECTIVE: To compare the results and outcomes of three different approaches to posttraumatic pseudoaneurysm repair: clamp and sew, left heart bypass, and the most recent approach, cardiopulmonary support using femoral-femoral bypass. DESIGN: Retrospective series. SETTING: A university-based, level 1 trauma center. PATIENTS: Forty-two consecutive patients treated for posttraumatic aortic pseudoaneurysm whose mean (+/- SEM) Injury Severity Score was 37 +/- 1.7. INTERVENTION: Methods of repair included clamp and sew in nine patients, left heart bypass in 24 patients, and cardiopulmonary support in nine patients. METHODS: Student's t test was used to compare interoperative blood loss, need for blood transfusion, and aortic cross-clamp time. Complications and mortality were also reviewed. RESULTS: Mean (+/- SEM) aortic cross-clamp time for clamp and sew was 28.1 +/- 3.3 minutes vs 52.5 +/- 3.7 for left heart bypass and 49.3 +/- 5.6 for cardiopulmonary support. Blood loss and the need for transfusion were comparable between groups. Complications were also comparable. CONCLUSION: Femoral-femoral cardiopulmonary support is safe to use, has a very low risk of complications, and should provide protection for the spinal cord during aortic repair. We encourage a randomized prospective trial to determine if cardiopulmonary support has a significantly lower rate of paraplegia than the clamp- and -sew technique.

Posttransplantation function of hearts preserved with fluorochemical emulsion.

This study was designed to determine whether the novel perfluoroperhydrophenanthrene-egg yolk phospholipid emulsion, APE-LM, was an effective oxygen carrier for long-term hypothermic heart preservation. We postulated that hearts preserved with APE-LM would be well oxygenated during 24-hour preservation and that reperfusion of such hearts with blood would not produce functional or metabolic evidence of myocardial ischemia. Four groups of rabbit hearts were studied (n = 7 per group): fresh controls: nonpreserved, nontransplanted hearts; surgical controls: fresh hearts transplanted heterotopically for 75 minutes before explant and study for 4 hours as isolated working hearts perfused at 37 degrees C; crystalloid-preserved: hearts preserved with crystalloid medium, followed by transplantation and isolated heart perfusion; APE-LM-preserved: hearts treated as those in the crystalloid-preserved group, but preservation was with medium containing APE-LM emulsion (10 ml/dl). Preservation was with continuous coronary perfusion at 18 mm Hg pressure, 12 degrees C, and oxygen tension 838 +/- 11 mm Hg. During preservation, APE-LM hearts had significantly higher pyruvate consumption, and correspondingly higher oxygen consumption, than that of crystalloid hearts. No significant differences were found among fresh controls, surgical controls, and APE-LM-preserved hearts with respect to contractile or output function, oxygen consumption and efficiency indexes, or lactate production during in vitro perfusion. Left ventricular peak systolic pressure and peak rate of pressure development were significantly lower for crystalloid-preserved hearts than for fresh and surgical controls. Left ventricular end-diastolic pressure of crystalloid-preserved hearts was higher than that of the other three groups. The data indicate that rabbit hearts in this model were well preserved with APE-LM and that this emulsion produced better recovery of function than did crystalloid preservation, possibly as a consequence of the high oxygen delivery by the fluorocarbon during preservation.

Importance of substrate enhancement for long-term heart preservation.

These experiments tested the hypothesis that addition of pyruvate to a preservation medium would improve postpreservation cardiac function as quantified in an isolated working heart model after heterotopic transplantation. Four groups of rabbit hearts were studied (n = 5 per group): fresh controls, fresh hearts perfused as isolated working hearts; surgical controls, fresh hearts transplanted heterotopically and reperfused with blood for 75 minutes before being studied as isolated hearts; preserved without pyruvate, hearts perfusion-preserved with oxygenated extracellular-type crystalloid medium; preserved with pyruvate, same same as the group without pyruvate, but medium contained 20 mmol/L pyruvate. After preservation, the hearts in the two preserved groups were transplanted and studied as isolated hearts. Total ex vivo time for the preserved hearts was 24.5 +/- 0.2 hours. During preservation, glucose was not consumed by hearts in either preserved group. Pyruvate was used by the hearts to which it was provided (22.9 +/- 2.7 mumol pyruvate x hour-1 x gm dry weight-1). Performance of transplanted surgical control hearts was not significantly different from that of fresh controls. Function of the pyruvate-preserved hearts was similar to that of the fresh and surgical controls except that left ventricular peak systolic pressure and peak rate of pressure development were lower and that left ventricular end-diastolic pressure was higher for the pyruvate-preserved hearts. The hearts preserved without pyruvate had significantly lower compliance and function compared to the other three groups, which was evident in all indexes of contractility and output. We conclude that hearts preserved with pyruvate-containing crystalloid medium had better postpreservation, posttransplantation function than hearts preserved without pyruvate, although there was slight loss of compliance and decreased contractile function in the pyruvate-preserved hearts compared to controls.

Pericardial patch repair of left ventricular aneurysm.

Infectious complications associated with the use of Teflon felt buttresses in left ventricular aneurysm repair may result in serious morbidity. Use of an autologous pericardial patch is an alternative approach that should be considered. The technique, which we have used in 4 patients, is described.