Continuous intravascular blood gas monitoring

The benefit of a continuous intra-arterial blood gas monitor is apparent to any physician who has ever waited for the return of blood gas values at the bedside of a critically ill patient. The potential for rapid detection and prompt treatment of blood gas changes, coupled with immediate evaluation of the effectiveness of a therapeutic intervention, appears great. Whereas these systems may offer a tremendous advance in the physician's ability to track and treat alterations in cardiopulmonary physiology, no large-scale in vivo human trials have yet been reported. The only data available on accuracy, bias, precision, drift, and complication rate are from relatively small trials. Hopefully, when large-scale trials are completed, these systems will live up to their tremendous potential.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31921/1/0000874.pd

Dichloroacetate enhances myocardial functional and metabolic recovery following global ischemia

This study was undertaken to determine the effect of dichloroacetate (DCA) on myocardial functional and metabolic recovery following global ischemia. Sixteen isolated rabbit hearts were subjected to 120 minutes of mildly hypothermic (34[deg]C) cardioplegic arrest with multi-dose, modified St. Thomas' cardioplegia. Following ischemia, hearts were reperfused with either a physiologic salt solution (PSS) as controls, (CON, N = 10), or PSS containing DCA (DCA, N = 6) at a concentration of 1 mmol/L. Functional and metabolic indices were determined at baseline and at 15, 30, and 45 minutes of reperfusion. Results were analyzed using analysis of variance (ANOVA, Sheffe F test) and significance was defined as P 2) was increased in the DCA versus CON hearts (71 +/- 10% of baseline, v 51 +/- 19%). Diastolic compliance during reperfusion was improved in those hearts receiving DCA, as was myocardial mechanical use efficiency (DP/MVO2). Correction of myocardial tissue pH to baseline values was similar in both groups, indicating that the beneficial effect on functional recovery seen with DCA was not solely related to amelioration of acidosis. The enhanced myocardial function and improved metabolic status noted with DCA may result from increased oxidative phosphorylation due to altered pyruvate dehydrogenase (PDH) activity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31660/1/0000594.pd

Blood Substitutes in Cardiac Surgery

A safe, inexpensive, noninfectious substitute for red blood cells has long been sought. Despite tremendous advances in blood banking, the logistics of collecting, transporting, and storing human red blood cells contin ues to create infection and shortage problems. The two basic types of blood substitutes currently under devel opment are hemoglobin based and fluorocarbon based. Although they each transport oxygen differently, the basic advantages and limitations are the same. Blood substitute advantages include the unique capacity for room temperature storage, noninfectivity, adequate supply, and low toxicity. Restrictions include limited dosing in the acute period, limited intravascular half-life and, for the fluorocarbons, a requirement for a high PaO2. In addition, there remain questions about the relationship of nitric oxide metabolism to hypertension in hemoglobin solutions. Early clinical and laboratory trials have shown that both types of solutions are effective oxygen-delivery agents, with acceptable side- effect profiles. Clinical trials are currently underway to determine the safety and efficacy of these solutions in patients undergoing cardiopulmonary bypass.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68576/2/10.1177_108925329800200403.pd

Hemodynamic alterations and regional myocardial blood flow during supraceliac aortic occlusion in dogs with a critical coronary stenosis

The hemodynamic consequences and myocardial blood flow alterations associated with cross-clamping of the thoracic aorta were studied during pentobarbital (control), halothane (1 MAC), and isoflurane (1 MAC) anesthesia in dogs with a critical stenosis of the left circumflex coronary artery. Aortic clamping at the level of the diaphragm resulted in significant and equivalent increases in mean aortic pressure and left atrial pressure during the control clamp, halothane clamp, and isoflurane clamp periods. Likewise, aortic clamping resulted in a significant and equivalent decrease in cardiac output during control-clamp, halothane clamp, and isoflurane clamp. Myocardial contractility as assessed by dP/dt was depressed during halothane and isoflurane anesthesia when compared with control, but no further change in contractility was associated with aortic clamping. No signifcant alterations in regional or transmural myocardial bloc flow were found with halothane or isoflurane anesthesia, c with aortic clamping during halothane or isoflurane anesthesia. It is concluded that there are significant hemodynami consequences associated with aortic clamping, that neithe halothane nor isoflurane anesthesia alters these consequences when compared with pentobarbital anesthesia alone and that the deterioration in myocardial function observe during aortic clamping with halothane and isoflurane anesthesia cannot be attributed to any maldistribution of myocardh blood flow.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29461/1/0000544.pd

Polymerized bovine hemoglobin solution as a replacement for allogeneic red blood cell transfusion after cardiac surgery: Results of a randomized, double-blind trial

AbstractBackground: Blood loss leading to reduced oxygen-carrying capacity is usually treated with red blood cell transfusions. This study examined the hypothesis that a hemoglobin-based oxygen-carrying solution can serve as an initial alternative to red blood cell transfusion. Methods: In a randomized, double-blind efficacy trial of HBOC-201, a total of 98 patients undergoing cardiac surgery and requiring transfusion were randomly assigned to receive either red blood cell units or HBOC-201 (Hemopure; Biopure Corporation, Cambridge, Mass) for the first three postoperative transfusions. Patients were monitored before and after transfusion, at discharge, and at 3 to 4 weeks after the operation for subsequent red blood cell use, hemodynamics, and clinical laboratory parameters. Results: The use of HBOC-201 eliminated the need for red blood cell transfusions in 34% of cases (95% confidence interval 21%-49%). Patients in the HBOC group received a mean of 1.72 subsequent units of red blood cells; those who received red blood cells only received a mean of 2.19 subsequent units (P =.05). Hematocrit values were transiently lower in the HBOC group but were similar in the two groups at discharge and follow-up. Oxygen extraction was greater in the HBOC group (P =.05). Mean increases in blood pressure were greater in the HBOC group, but not significantly so. Conclusion: HBOC-201 may be an initial alternative to red blood cell transfusions for patients with moderate anemia after cardiac surgery. In a third of cases, HBOC-201 eliminated the need for red blood cell transfusion, although substantial doses were needed to produce this modest degree of blood conservation.J Thorac Cardiovasc Surg 2002;124:35-4

Accuracy and precision of a new, portable, handheld blood gas analyzer, the IRMA®

Objective. The accuracy and precision of the new IRMA® (Immediate Response Mobile Analysis System, Diametrics, Inc.®, St. Paul, MN) handheld blood gas analyzer was compared with that of two benchtop blood gas analyzers. The IRMA consists of a notebook-sized machine and disposable cartridges, each containing a pH, a CO 2 and an O 2 electrode, and provides bedside (point-of-care) blood gas analysis. Methods. A total of 172 samples (arterial and mined venous) were obtained from 25 informed, consenting patients undergoing cardiopulmonary bypass. The pH, PCO 2 and PO 2 of each sample was determined on four blood gas analyzers: NOVA Statlabs Profile 5 (NOVA Biomedical, Waltham, MA), the ABL-50 (Radiometer, West Lake, OH), and two IRMA machines. Linear regression and bias ± precision were determined, comparing each of the analyzers with the NOVA. Results. All three machines showed a similar, high degree of correlation with the NOVA for pH, PCO 2 , and PO 2 . The bias and precision of the IRMA machines compared with the NOVA was similar to that of the ABL compared with the NOVA for pH (NOVA:ABL −0.005 ± 0.011; NOVA: IRMA 1 = 0.0026 ± 0.025; NOVA: IRMA 2 = 0.0021 ± 0.025), for PCO 2 (NOVA:ABL = −1.4 ± 1.3 mmHg; NOVA: IRMA 1 = −1.3 ± 1.9 mmHg; NOVA: IRMA 2 = −1.2 ± 2.1 mmHg) and PO 2 (NOVA:ABL = 3.6 ± 21.1 mmHg; NOVA: IRMA 1 = 3.4 = 19.9 mmHg; NOVA: IRMA 2 = 6.3 ± 20.9 mmHg). The bias found for pH, PCO 2 , and PO 2 was not affected by extremes of temperature (range 25.5–40°C) or hematocrit (range 11–44%) for any machine. Conclusions. The new technology incorporated in the IRMA blood gas analyzer provides results with an accuracy that is similar to that of benchtop analyzers, but with all of the advantages of point-of-care analysis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43058/1/10877_2005_Article_BF02221753.pd

Patient Safety in the Cardiac Operating Room: Human Factors and Teamwork: A Scientific Study from the American Heart Association

The cardiac surgical operating room (OR) is a complex environment in which highly trained subspecialists interact with each other using sophisticated equipment to care for patients with severe cardiac disease and significant comorbidities. Thousands of patient lives have been saved or significantly improved with the advent of modern cardiac surgery. Indeed, both mortality and morbidity for coronary artery bypass surgery have decreased during the past decade. Nonetheless, the highly skilled and dedicated personnel in cardiac ORs are human and will make errors. Refined techniques, advanced technologies, and enhanced coordination of care have led to significant improvements in cardiac surgery outcomes

The use of dichloroacetate in the treatment of overwhelming hypoxic acidosis

Overwhelming hypoxic acidosis due to poor tissue oxygen delivery from low cardiac output, pulmonary failure, and other causes has devastating effects postoperatively on patient outcome. Whereas conventional therapeutics often can not reverse the downward spiral of these patients, dichloroacetate (DCA) has been shown to be beneficial. This study investigated the metabolic and hemodynamic effects of DCA given after the onset of overwhelming hypoxic acidosis in a canine model. A hypoxically ventilated canine model of severe induced acidosis was established and dogs surviving the development of acidosis were randomized to receive DCA or sodium chloride (NaCI) treatment. Dogs receiving DCA after development of hypoxic lactic acidosis showed no further change in metabolic parameters during the 90-minute treatment period (pH, 7.24 to 7.23; HC03, 17.7 to 18 mmol/L; lactate, 2.04 to 1.05 mM/L); whereas animals receiving an equivalent sodium load showed progressive, significant deterioration in all parameters (pH, 7.24 to 7.12; HCO3, 16.8 to 13.2 mM/L; lactate, 2.05 to 3.55 mM/L). Myocardial blood flow was significantly increased by hypoxia in all dogs. Finally, cardiac output and stroke volume were significantly increased at 90 minutes by DCA versus control. Myocardial oxygen utilization efficiency (LV work/ M VO2) was improved during DCA treatment. DCA, a carboxylic acid, increases pyruvate dehydrogenase activity, thereby enhancing lactate use as a metabolic substrate. DCA had an ameliorative metabolic effect, and benefitted myocardial performance without a direct inotropic effect. DCA treatment appears to enhance myocardial performance on a metabolic and not primarily inotropic basis, does not increase the "cost" of myocardial work, and warrants further study.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31792/1/0000733.pd

Monitoring oxygenation

The most basic goal of anaesthetists and intensivists is to assure that there is an adequate supply of oxygen to the mitochondria throughout the body to maintain aerobic metabolism and cellular function. The determination of adequate oxygenation has historically been monitored by the absence of organ dysfunction because techniques were not available to assess quantitatively the oxygenation of tissues. Over the past 40 years, measurement and monitoring methods have been developed to first quantitate oxygen supply and more recently to continuously asess both invasively and noninvasively the oxygenation of blood and tissue. 1This article will review the current status of the invasive and noninvasive techniques for monitoring oxygenation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30467/1/0000095.pd

The PROXIMAL trial: proximal protection during saphenous vein graft intervention using the Proxis Embolic Protection System: a randomized, prospective, multicenter clinical trial.

OBJECTIVES: To determine if outcomes could be further improved, we investigated an embolic protection device placed proximal to the target lesion that could provide protection before lesion instrumentation, allow the use of conventional guidewires, and permit embolic protection in anatomy unfavorable for distal devices. BACKGROUND: Embolic complications during stenting of degenerated saphenous vein coronary bypass grafts are reduced, but not eliminated, by distal protection. METHODS: A total of 594 patients undergoing stenting of 639 saphenous vein grafts were prospectively randomized, using a noninferiority design, to compare 2 treatment strategies: control (distal protection whenever possible) or test (proximal protection when possible, distal when not). RESULTS: The primary composite end point of death, myocardial infarction, or target vessel revascularization at 30 days by intention to treat analysis occurred in 10.0% of control and 9.2% of test patients; difference = -0.8% (95% confidence interval [CI] -5.5% to 4.0%); p for noninferiority = 0.0061. In device specific analysis, this composite end point occurred in 11.7% of distal protection patients and 7.1% of proximal protection patients (difference = -4.6% [95% CI -9.6% to 0.3%]; p for superiority = 0.10, p for noninferiority = 0.001). Finally, in the subset of patients with lesions amenable to treatment with either proximal or distal protection devices (n = 410), the primary composite end point occurred in 12.2% of distal protection patients and 7.4% of proximal protection patients; difference = -4.7% (95% CI -10.4% to 1.0%), p for superiority = 0.14, p for noninferiority = 0.001. CONCLUSIONS: Using proximal embolic protection whenever possible during treatment of diseased saphenous vein grafts produced outcomes similar to those with distal embolic protection