Acute physiological changes following heart-lung allotransplantation in dogs

Ultrastructural damage to the preserved lung and its function after reperfusion

OBJECTIVE

This study was undertaken to clarify what damage to a lung during cold storage influenced the function of transplanted lung after reperfusion.

METHODS

We examined the ultrastructural damage in preserved right lung before reperfusion, and the function of transplanted left lung, in a same dog and measured the pulmonary artery oxygen pressure after reperfusion and the wet-to-dry-weight ratio. We compared these findings between those dogs that survived until six hours after reperfusion (Alive Group) and those dogs that did not survive (Dead Group). We also investigated any correlation between the ultrastructural damage in the preserved lung and the function of the transplanted lung.

RESULTS

The frequency of protrusion and destruction of the endothelial cells in the small pulmonary artery, and vacuolization of pneumocytes, in the Dead Group was significantly higher than that in the Alive Group. A correlation was found between the frequency of two kinds of ultrastructural damage; vacuolization in the endothelial cells in the small pulmonary artery and vacuolization in the pneumocytes, and the pulmonary artery oxygen pressure at 1-hour after reperfusion. A correlation was also found between the frequency of the vacuolization of pneumocytes and the wet-to-dry-weight ratio.

CONCLUSIONS

Findings suggested that a lung suffering severe damage to intracellular structure during hypothermic preservation is unable to function sufficiently after reperfusion and is at high risk for early graft failure.

Lung transplantation with cardiopulmonary bypass exaggerates pulmonary vasomotor dysfunction in the transplanted lung

Pulmonary vascular resistance is significantly increased in the transplanted lung. If cardiopulmonary bypass is required, the transplanted lung is reperfused with activated blood elements, which might exacerbate the reperfusion injury. The purpose of this study was to examine the influence of cardiopulmonary bypass on the following mechanisms of pulmonary vasomotor control in a dog model of autologous lung transplantation: (1) endothelium-dependent cyclic guanosine monophosphate-mediated relaxation (response to acetylcholine), (2) endothelium-independent cyclic guanosine monophosphate-mediated relaxation (response to nitroprusside), and (3) beta-adrenergic cyclic adenosine monophosphate-mediated relaxation (response to isoproterenol). Autologous right lung transplants were performed with (n = 4 dogs) and without (n = 5 dogs) bypass. Lungs were stored in cold saline solution (4 degrees C, 3 hours) before reimplantation. Pulmonary vasomotor control mechanisms were studied in isolated pulmonary arterial rings immediately after harvest and 1 hour after reimplantation. Ten rings were studied in each group at each time. Statistical analysis was by analysis of variance. Without bypass, endothelium-dependent cyclic guanosine monophosphate-mediated relaxation and beta-adrenergic cyclic adenosine monophosphate-mediated relaxation were significantly impaired, although endothelium-independent cyclic guanosine monophosphate-mediated relaxation was not. Use of bypass produced significantly greater impairment of both endothelium-dependent cyclic guanosine monophosphate-mediated relaxation and beta-adrenergic cyclic adenosine monophosphate-mediated relaxation. In addition, use of bypass produced significant dysfunction of endothelium-independent cyclic guanosine monophosphate-mediated relaxation as well. We conclude that using cardiopulmonary bypass to perform lung transplantation greatly exaggerates pulmonary vasomotor dysfunction in the transplanted lung. This dysfunction may contribute to significantly higher pulmonary vascular resistance in the transplanted lung if cardiopulmonary bypass is used.

Influence of pH of preservation solution on lung viability

Recently, various solutions for organ preservation have been introduced. Despite much debate regarding the composition of preservation solutions, the ideal pH of a preservation solution has not been determined. We investigated the effects of the pH of a lung preservation solution on viability using an isolated, ventilated lung perfusion model. Initially, we performed flush perfusion with solutions of five different pH groups (6.60, 7.00, 7.40, 7.80 and 8.20, measured at 10 degrees C). Lungs perfused with pH 6.60 solution had a significantly higher pulmonary vascular resistance than those perfused with pH 7.40, 7.80 and 8.20 solutions. Blood was washed out completely and uniformly with solutions of pH 7.40 and 7.80. After preservation the arterial oxygen tension was significantly greater in pH 7.40 and 7.80 groups than in pH 6.60, 7.00, or 8.20 groups. Moreover, pulmonary artery pressure, airway pressure, and wet/dry weight ratios in the pH 7.40 and 7.80 groups were lower than in the others. We conclude that for both pulmonary flush and storage preservation, solutions of pH 7.40 to pH 7.80 are optimal for lung preservation.

Oxygen free radical scavengers decrease reperfusion injury in lung transplantation

An in vivo canine model was used to assess the ability of an oxygen free radical scavenger to decrease reperfusion injury in lung transplantation. In 12 dogs, the left lungs were transplanted after they had been preserved for 24 hours at 4 degrees C after pulmonary artery flushing with modified Eurocollins solution. In 6 dogs, dimethylthiourea, a potent oxygen free radical scavenger, was added to the flush solution and was also given to the recipients just before reperfusion. In all animals, the contralateral pulmonary artery and bronchus were ligated and lung function was assessed for 12 hours or until death. Three dogs died prematurely in the control group, whereas only 1 dog died prematurely in the dimethylthiourea group. This resulted in a statistically significant difference in the average length of survival (p less than 0.05). Pulmonary artery and right atrial pressures were significantly lower in the dimethylthiourea group during the first 6 hours (p less than 0.05). Treatment with dimethylthiourea resulted in a significantly higher arterial oxygen tension at 4 hours, and intrapulmonary shunt tended to be lower. Thus, it would appear that dimethylthiourea has a protective effect on lungs preserved for 24 hours before transplantation in dogs.

The effects of a prostacyclin analog OP-41483 on pulmonary oxygen toxicity in an isolated heart-lung autoperfusion model

Using an isolated canine heart-lung autoperfusion model, the effect of prostacyclin analog (OP-41483) on pulmonary oxygen toxicity was investigated. Twenty-four mongrel dogs were divided into four groups. Groups 1 and 2 inspired oxygen at concentrations (FiO2) of 0.95 and 0.6, respectively, while groups 3 and 4 received OP-41483 (0.1 micrograms/kg/min) in addition to FiO2 of 0.95 and 0.6. Autoperfusion was performed for five hours, and during the experiments the systolic blood pressure was maintained at 100 mmHg and the cardiac output at 40 ml/kg/min. After five hours of perfusion, PaO2 decreased significantly (P less than 0.01) from 410 +/- 49 mmHg to 237 +/- 38 mmHg in group 1, and also decreased significantly (P less than 0.01) from 368 +/- 44 mmHg to 243 +/- 26 mmHg in group 2. However, no significant changes in PaO2 were observed in groups 3 and 4. The pathological examinations clearly revealed perivascular edema and vascular dilation in groups 1 and 2, whereas no abnormal pathological findings were seen in groups 3 and 4. The above results indicate that OP-41483, when administered at the low dose of 0.1 micrograms/kg/min, induces no circulatory changes and exerts an effective action with respect to the prevention of pulmonary edema.

Hypothermic preservation of the heart and lungs with Collins solution: effect on cardiorespiratory function following heart-lung allotransplantation in dogs

The effect of preserving the heart and lungs with hypothermia and Collins solution was studied in 13 mongrel dogs undergoing combined heart-lung transplantation. The five control animals who underwent an immediate transplant following Collins solution perfusion had small increases in extravascular lung water when measured 2.5 hours posttransplant as seen in a previous study. The eight animals who had hypothermic preservation following Collins solution perfusion had significantly higher extravascular lung water than controls (16.3 +/- 1.8 ml/kg in preserved animals; 11.2 +/- 1.7 ml/kg in controls p less than 0.05). The level of lung water reached at 2.5 hours postoperatively was similar to that reached with a previously reported, unacceptable preservation technique. Survival beyond this point was poor due to severe pulmonary edema. We conclude that the use of this solution, given under the experimental conditions which we describe, is not acceptable for hypothermic preservation of the heart and lungs for combined transplantation.

Prognosis in acute organ-system failure

This prospective study describes the current prognosis of patients in acute Organ System Failure (OSF). Objective definitions were developed for five OSFs, and then 5677 ICU admissions from 13 hospitals were monitored. The number and duration of OSF were linked to outcome at hospital discharge for each of the 2719 ICU patients (48%) who developed OSF. For all medical and most surgical admissions, a single OSF lasting more than 1 day resulted in a mortality rate approaching 40%. Among both medical and surgical patients, two OSFs for more than 1 day increased death rates to 60%. Advanced chronologic age increased both the probability of developing OSF and the probability of death once OSF occurred. Mortality for 99 patients with three or more OSFs persisting after 3 days was 98%. The two patients who survived were both young, in prior excellent health, and had severe but limited primary diseases. These results emphasize the high death rates associated with acute OSF and the rapidity with which mortality increases over time. The prognostic estimates provide reference data for physicians treating similar patients.

The effect of hypothermic preservation of the heart and lungs on cardiorespiratory function following canine heart-lung transplantation

The effect of hypothermic preservation of the heart and lungs with a crystalloid solution was evaluated in 12 mongrel dogs receiving heart-lung allografts. Six animals served as controls and received an immediate heart-lung transplant. Six animals were in the experimental group and received a heart-lung transplant after 5 hours of preservation at 4 degrees C following perfusion of both organs with a crystalloid solution. Physiological function of the heart and lungs was studied for 20 hours after transplantation. While cardiac function was minimally depressed following preservation, pulmonary function testing demonstrated significantly greater increases in extravascular lung water in experimental animals, suggesting that an ischemic lung injury occurred with this preservation technique. The model allows for future evaluation of other methods of combined preservation of both the heart and lungs for transplantation.