Louise O. Soltow

Perfluorocarbon emulsion in the cardiopulmonary bypass prime reduces neurologic injury

BACKGROUND Perfluorocarbon emulsion has proved beneficial in the prevention and amelioration of experimental air embolism. We examined whether the addition of perfluorocarbon to the prime solution could lead to a reduction in the incidence and severity of neurologic injury after the formation of a massive air embolism during cardiopulmonary bypass. METHODS Fourteen pigs underwent bypass in which either a crystalloid prime solution or a perfluorocarbon prime solution (10 mL/kg) was used. Ten minutes into bypass a bolus (5 mL/kg) of air or saline (control) was delivered via the carotid artery. The resulting cerebral infarcts were graded on the basis of the findings in triphenyltetrazolium chloride-stained cerebral sections. Colored microspheres were used to measure cerebral blood flow. Bitemporal electroencephalography was used to evaluate cerebral function. RESULTS Cerebral infarction was not found in the perfluorocarbon-air group (0 to 5 animals), as compared with its occurrence in 3 of the 5 animals in the crystalloid-air group. Cerebral blood flow was also maintained or increased in the perfluorocarbon-air group (p < 0.05), and the electroencephalogram total power showed less of a decrease and recovered more completely (p < 0.05) than it did in the crystalloid-air group. CONCLUSIONS The addition of perfluorocarbon emulsion to the cardiopulmonary bypass prime solution leads to a reduction in the incidence and severity of neurologic injury after the formation of a massive air embolism during bypass.

Ketamine Alters Calcium and Magnesium in Brain Tissue following Experimental Head Trauma in Rats

We previously reported that the N-methyl-d-aspartate receptor antagonists dizocilpine maleate and ketamine improved the neurological severity score (NSS) after head trauma in rats. Other investigators have reported increased calcium and decreased magnesium following head trauma in untreated rats. The present study was designed to determine whether ketamine influences the concentrations of calcium and magnesium in brain tissue following head trauma. Eighty-six male Sprague–Dawley rats (180 ± 15 g) were divided into eight groups. Groups A (no head injury) and C (head injury) received no treatment. Groups B (no head injury) and D–H (head injury) received ketamine. In groups D, E, and F, ketamine, 180 mg/kg i.p., was given 1, 2, and 4 h after head trauma, respectively. In groups G and H, ketamine, 120 and 60 mg/kg, respectively, was given 1 h after head trauma. After we killed the rats at 48 h, cortical slices were taken to measure tissue calcium and magnesium content by the inductively coupled plasma atomic emission spectroscopy method. In the contused hemispheres, calcium increased and magnesium decreased (p < 0.0001). Among the head-injured groups, the increase in brain tissue calcium was smaller in groups receiving 60 mg/kg of ketamine at 1 h or 180 mg/kg of ketamine at 1, 2, or 4 h than in the group not receiving ketamine. The decrease in brain tissue magnesium was smaller in the groups receiving 180 mg/kg of ketamine at 1 and 2 h than in the group not receiving ketamine. Temporalis muscle and rectal temperatures at 1, 2, 4, 24, and 48 h after head trauma were not significantly different between treated and untreated groups. It is concluded that, in this model of closed cranial impact, 180 mg/kg of ketamine given 1 or 2 h after injury reduced both the increase in brain tissue calcium and the decrease in brain tissue magnesium at 48 h following head trauma.

Heparin-coated bypass circuits (Carmeda) suppress the release of tissue plasminogen activator during normothermic coronary artery bypass graft surgery☆

OBJECTIVES To study fibrinolysis in a homogeneous first-time coronary artery bypass surgery (CABG) population in whom heparin-coated circuits were used. DESIGN A prospective, blinded, randomized, placebo-controlled study. SETTING A university hospital, tertiary care, intraoperative and postoperative intensive care unit. PARTICIPANTS Twenty-one adult elective primary CABG patients. INTERVENTIONS Randomized circuit-type centrifugal pump, membrane oxygenator, rigid cardiotomy reservoir, either placebo (n = 10) or heparin-coated (n = 11) (Carmeda; Medtronic Inc., Anaheim, CA). MEASUREMENTS AND MAIN RESULTS Blood samples were analyzed for tissue plasminogen activator (TPA) activity, TPA antigen, plasminogen activator inhibitor-1 (PAI-1) activity, prothrombin complex F1.2, and antithrombin III (AT-III) at the following times: before cardiopulmonary bypass (CPB), during CPB (30 and 60 minutes), post-CPB, and day 1 postsurgery. TPA activity and antigen increased fivefold in the placebo group during CPB, whereas it did not even double in the heparin-coated group. PAI-1, F1.2, and AT-III were not different between groups. CONCLUSIONS Heparin-coated CPB circuits reduced TPA release in this homogeneous CABG population with routine heparin/protamine management.

Does the Type of Surgery Effect Systemic Response Following Cardiopulmonary Bypass

Abstract  Background: Clinical studies conducted to elucidate the systemic response to cardiopulmonary bypass (CPB) did not differentiate possible effect of different types of cardiac surgical pathologies and operations on outcomes and have typically combined different procedures. We hypothesized that valve surgery induces more prominent systemic reaction compared to isolated on‐pump CABG. Methods: Twenty‐seven patients undergoing primary on‐pump CABG (Group 1, n = 14) or valve surgery with or without CABG (Group 2, n = 13) were prospectively enrolled. Heparin‐bonded circuits were used in all patients. Cardiotomy suction was only used in Group 2. Clinical and laboratory markers were evaluated. Results: Clinical measurements, including chest tube output, blood transfusion requirement, inotropic support requirement, and duration of ICU stay were not significantly different. Thrombin generation (PF‐1.2) was significantly higher in Group 2 (p = 0.001). tPA was also significantly higher in Group 2 at 15 and 60 minutes on CPB (p < 0.01). Group 2 had significantly higher inflammatory response shown by elevation of IL6 (p = 0.005). Neuronal injury markers, S100β and NSE, were significantly higher at the termination of CPB in Group 2 (p < 0.01). At no point of time course for any marker, Group 1 had significantly higher response compared to Group 2. Conclusions: Valve surgery induced more prominent systemic response than CABG. The possible explanations include the difference in baseline disease pathophysiology, and/or difference associated with the procedures such as open systems and use of cardiotomy suction. Future clinical studies assessing systemic response to CPB and therapies to blunt these need consider and account for these observed differences.

A second-generation blood substitute (perfluorodichlorooctane emulsion) does not activate complement during an ex vivo circulation model of bypass

OBJECTIVES To examine whether a second-generation perfluorocarbon (PFC) blood substitute added to the cardiopulmonary bypass (CPB) prime influences complement production. DESIGN A prospective, randomized, single-blinded, ex vivo model. SETTING A university hospital, laboratory, and clinics. PARTICIPANTS Ten healthy adult consented volunteer blood donors (five men, five women). INTERVENTIONS Ex vivo closed-loop extracorporeal circuit including membrane oxygenator, tubing, and filter primed with crystalloid or crystalloid plus PFC was circulated for 1 hour with the addition of 500 mL of heparinized fresh human whole blood. MEASUREMENTS AND MAIN RESULTS Laboratory specimens were drawn from the circuit at 10-minute intervals for 1 hour and measured for complement (C3a, Bb fragment) concentrations, blood gases, fibrinogen concentration, platelet count, and hematocrit. In the PFC group, C3a and Bb fragments were equal to or less than those in the group that received crystalloid alone. CONCLUSION The second-generation PFC added to the prime of a CPB circuit does not independently increase complement production.

The HPV response is different with constant pressure vs constant flow perfusion

Hypoxic pulmonary vasoconstriction (HPV) may be manifest in one of two ways: either an increase in the pulmonary artery pressure, or flow diversion away from the portion of the pulmonary bed with reduced conductance. We tested the hypothesis that the magnitude of the HPV response differs under conditions of constant flow perfusion, where pulmonary artery pressure (Ppa) rises during hypoxia, vs conditions of constant pressure perfusion, where Ppa remains constant and flow (Q) is diverted away from the lungs during hypoxia. In isolated, perfused rabbit lungs, the HPV response to four levels of hypoxia (12, 6, 3 and 0% oxygen) was of greater magnitude and more sustained under conditions of constant pressure perfusion as compared to constant flow perfusion. The possible significance of these findings as they relate to interpretation of studies in both the perinatal and mature pulmonary circulation is discussed.