Neutrophil sequestration and pulmonary dysfunction in a canine model of open heart surgery with cardiopulmonary bypass. Evidence for a CD18-dependent mechanism

Neutrophil expression of CD11b/CD18 and IL-8 secretion during normothermic cardiopulmonary bypass

OBJECTIVE

To assess blood polymorphonuclear neutrophil (PMN) activation status during normothermic cardiopulmonary bypass (CPB), the expression of the PMN adhesion molecule CD11b/CD18 was measured. Basal state as well as ex vivo capacity of PMN to be stimulated by a bacterial peptide (FMLP) were investigated. Because interleukin-8 (IL-8) is known to induce CD11b/CD18 expression in vitro in PMN, IL-8 plasma levels were concomitantly measured.

DESIGN

Prospective study.

SETTING

University hospital.

PARTICIPANTS

Thirteen patients scheduled for cardiac surgery.

INTERVENTIONS

Systemic arterial and pulmonary arterial blood samples were withdrawn at the same moment during the first 4 hours after the onset of CPB.

MEASUREMENTS AND MAIN RESULTS

Twenty minutes after the onset of CPB, basal expression of PMN CD11b/CD18 was upregulated, whereas IL-8 plasma levels remained unchanged. The increase in PMN CD11b expression was maintained until the fourth hour after the onset of CPB. At this time, elevation of IL-8 plasma levels was maximal. No differences were found between pulmonary and systemic arterial IL-8 plasma levels, even after aortic unclamping. The capacity of PMN to be stimulated ex vivo by FMLP remained normal.

CONCLUSIONS

Normothermic CPB induced a fast increase in CD11b expression, which appeared to be similar to that observed during hypothermia. IL-8 was probably not related to the very early CD11b upregulation, but could be involved in pulmonary PMN sequestration during pulmonary reperfusion and contribute to the maintained expression of PMN CD11b. Although partially activated, PMNs maintain a normal capacity to respond to a further FMLP stimulation and thus to bacterial infection.

Deep hypothermic low flow cardiopulmonary bypass in small dogs

OBJECTIVE

To evaluate the feasibility of and morbidity and mortality associated with cardiopulmonary bypass (CPB) using deep hypothermia and low flow perfusion in adult dogs weighing less than 10 kg.

STUDY DESIGN

Prospective, descriptive study.

ANIMALS

Two groups of three dogs underwent CPB. Group 1 dogs underwent deep hypothermia (15 to 18 degrees C), 45 minutes of low perfusion flow (20 mL/kg/min) and 1 hour of aortic cross clamp time. In group 2, ultrafiltration of perfusate before discontinuation of bypass was added to the standard treatment. Complete blood counts, serum biochemistry, urine output, ejection fraction, and cardiac output were monitored before and for 7 days after surgery.

RESULTS

All dogs were successfully weaned from bypass. Four of six dogs survived, three without major complications. One dog developed and recovered from septic pleuritis. Two dogs died or were euthanatized after surgery because of respiratory or gastrointestinal complications. Minor complications included anemia, hypoproteinemia, and electrolyte disturbances. Transfusion requirements and edema formation were reduced by ultrafiltration.

CONCLUSIONS

The observations in this study support the feasibility of low flow hypothermic CPB. Meticulous tissue handling, precise equipment, ultrafiltration, and aggressive postoperative potassium supplementation are recommended for smaller patients.

CLINICAL RELEVANCE

Increased sensitivity to adverse sequelae of CPB may be associated with small patient size. Further evaluation is necessary before routine clinical application of low flow hypothermic CPB in this patient population.

Brain death alters cardiopulmonary hemodynamics and impairs right ventricular power reserve against an elevation of pulmonary vascular resistance

Right ventricular (RV) failure, which is a leading cause of early morbidity and mortality following cardiac transplantation, is attributed to the inability of the donor RV to acutely compensate for the recipient's elevated pulmonary vascular resistance (PVR). Furthermore, the effect of donor brain death (BD) on RV function is unclear. The purpose of this study was to investigate the effects of donor BD on RV function in the setting of elevated PVR. The interactions of the RV and its afterload, the pulmonary vasculature, and left atrial pressure were assessed by measurements of pulmonary vascular energetics and their oscillatory nature using proximal ultrasonic pulmonary artery (PA) flow probe and micromanometers in the proximal and distal PA in 20 mongrel dogs (25.8 +/- 0.4 kg, five control animals). A band was placed around the distal PA (PA-systolic gradient > 15 mm Hg). BD was induced by rising intracranial pressure and was validated neuropathologically. Data were collected at 0, 2, 4, and 6 h after BD in both banded and control animals. Fourier analysis was used to calculate RV oscillatory power, mean power, and total power (TP). Comparison of changes due to banding were made to baseline measurements using multivariate analysis and paired Student's t test (p < 0.05). A significant twofold to fourfold increase in pulmonary impedance and PVR occurred with an acute rise in PA gradient. Control animals tolerated acute increases in PVR without significant changes in TP. There was a significant increase of RV TP from 73 (+/-11) to 98 (+/-10) mW at baseline after the acute rise in PVR and impedance. After BD, the response to increased PVR and impedance was abolished significantly compared with baseline and control animals, suggesting a significant loss of compensatory TP to sustain pulmonary vascular blood flow. The data indicate that BD is detrimental to RV mechanical function.