Clinical significance of weight difference between donor and recipient in heart transplantation.

A standard and important criterion for donor acceptance is to match the donor's body weight to within 20% of the recipient's body weight. However, to meet the increasing demand of patients who need heart transplantation, frequently a heart that is below the standard criteria for donation is accepted. Of the 200 consecutive patients who underwent heart transplantation at the University of Arizona, 27 patients received a heart from a smaller donor with a weight difference of more than 30% (range 30% to 46%). The early mortality and late survival of these 27 patients were not different when compared with those of the patients who received transplants from donors with a weight difference of less than 30%. The probability of freedom from rejection and infection and postoperative ejection fraction were also similar between the two groups. Therefore, we believe that the widely accepted donor-recipient weight-match criterion of 20% can be safely extended.

Is it necessary to perform surveillance endomyocardial biopsies in heart transplant recipients?

BACKGROUND: Routine surveillance endomyocardial biopsies to diagnose unsuspected rejection are performed at 3- to 12-month intervals after heart transplantation. From 1979 to 1989, surveillance biopsies were routinely performed as a part of the yearly evaluation. METHODS: A retrospective analysis of the follow-up data showed that "routine surveillance biopsies" had an extremely low yield, and, on the basis of the results of this study, we discontinued to perform surveillance biopsies beyond 6 months after transplantation. To validate these results, we compared the outcome of two groups of patients who had similar demographics and identical immunosuppression, except that in one group the surveillance biopsies were not performed. RESULTS: No difference was found in either actuarial survival rate or freedom from late rejection between the two groups. CONCLUSIONS: These findings confirm that routine surveillance heart biopsies beyond 6 months after transplantation are not necessary and they should be performed only if there is clinical suspicion of rejection or as part of a research protocol.

Comparison of the CardioWest total artificial heart, the novacor left ventricular assist system and the thoratec ventricular assist system in bridge to transplantation.

BACKGROUND: Device selection has historically been supported by minimal comparative data. Since 1994, we have implanted 43 patients with the CardioWest Total Artificial Heart (CW), 23 with the Novacor Left Ventricular Assist System (N), and 26 with the Thoratec Ventricular Assist System (T). This experience provides a basis for our device selection criteria. METHODS: We reviewed retrospectively the results for survival, stroke, and infection in the CW, N, and T groups. Statistical methods included the Student's t-test, chi2 analysis, and Kaplan-Meier actuarial survival curves. RESULTS: The T group patients were younger and smaller sized than the CW or N group. The CW group had the highest mean central venous pressure (CVP) and lowest mean cardiac index. Survival to transplantation was 75% for CW, 57% for N, and 38% for T. Multiple organ failure postimplant caused most deaths in the CW and T groups. Right heart failure and stroke caused most N deaths. Linearized stroke rates (event/patient-month) were 0.03 for CW, 0.28 for N, and 0.08 for T. Serious infections were found in 20% of CW, 30% of N, and 8% of T patients, but linearized rates showed little difference and death from infection was rare. CONCLUSIONS: The N device should be used in "stable" patients with body surface area (BSA) greater than 1.7 m2 and with minimal right heart failure. Unstable patients with biventricular failure should receive a CW if the BSA is greater than 1.7 m2 or a T if they are smaller.

Guidelines for nutrition therapy in critical illness: are not they all the same?

In general, clinical guidelines identify, summarize, and evaluate the most current data concerning prevention, diagnosis, prognosis, therapy and cost for a specific patient population. This paper will briefly describe the authors' point of view regarding controversial aspects of adult critical care nutrition therapy guidelines published by preeminent professional societies in the United States (US), Canada, and Europe. The US guidelines were developed by subject matter experts to offer recommendations for specialized nutrition therapy that are supported by review and analysis of the pertinent current literature, other national and international guidelines, and by a blend of expert opinion and clinical practicality. A similar strategy was used to compile all three guideline publications resulting in many areas of common agreement, but disparate substantive recommendations do exist regarding: indirect calorimetry versus predictive equations, prokinetics in the intensive care unit (ICU), arginine use in the ICU, probiotic use in the ICU, and acceptable gastric residual volumes in the ICU patient. All of the guidelines are based on high quality studies in patients with critical illness, but like any other therapeutic modality for an ICU patient, nutritional interventions require a multidisciplinary approach that incorporates institutional best practices, individual patient considerations, and above all, clinical judgment.

Use of indirect calorimetry to optimize nutrition support and assess physiologic dead space in the mechanically ventilated ICU patient: a case study approach.

Indirect calorimetry (IC) is an accurate method of estimating a patient's energy expenditure, particularly the complex critically ill patient who benefits most from an individualized regimen of nutritional support. This bedside technique measures variables related to gas exchange and replaces assumptions about physiologic stress. When indirect calorimetry data are augmented by an arterial blood gas analysis of carbon dioxide (PaCO2), the dead space to tidal volume ratio (VD/VT) can be determined for an individual patient. These data can be valuable to the healthcare team when checking reasons for weaning failure. A case study approach to a 69-year-old man with acute respiratory distress syndrome and biliary sepsis will demonstrate the utility of this measurement. Attention to precise nutritional support and optimal gas exchange can influence the outcome of critically ill mechanically ventilated patients. This discussion highlights the potential benefits of indirect calorimetry for critical care nurses.

The effect of ascorbic acid on sodium nitrite-induced methemoglobin formation in glucose-6-phosphate dehydrogenase-deficient erythrocytes.

Ascorbic acid significantly reduced the occurrence of sodium nitrite-induced methemoglobin (METHB) formation in a dose-dependent manner in erythrocytes from glucose-6-phosphate dehydrogenase (G-6-PD)-deficient humans in vitro. The ascorbic acid treatment, however, also decreased levels of reduced GSH in a dose-dependent manner, a response indicative of oxidant stress to the erythrocyte membrane. The latter findings are inconsistent with the hypothesis that ascorbic acid supplementation in G-6-PD-deficient humans may help compensate for inherently low levels of erythrocyte GSH. Finally, the ascorbic acid-induced reduction of METHB values, while of statistical significance, does not appear to be of clinical significance.

The effect of ascorbic acid on copper-induced oxidative changes in the erythrocytes of rats, sheep, and normal humans.

Rats, sheep, and normal humans displayed a comparable sensitivity to copper acetate (3 mM)-induced changes in reduced glutathione (GSH) levels in vitro. However, the human erythrocytes were more sensitive than either animal to methemoglobin (METHB) formation with the rat being least sensitive. Ascorbic acid incubation markedly enhanced the occurrence of copper acetate-induced increases in METHB and decreases in GSH in the sheep and humans. However, ascorbic acid incubation reduced the occurrence of copper acetate-induced increases in METHB, while not effecting changes in GSH in rats.

The effect of ascorbic acid on nitrite-induced methemoglobin formation in rats, sheep, and normal human erythrocytes.

Interspecies differences were demonstrated with respect to the occurrence of sodium nitrite-induced methemoglobin (METHB) in the erythrocytes of rats, dorset sheep, and normal humans, with the rats displaying approximately 25-33% of the sensitivity of sheep and human erythrocytes. Ascorbic acid incubation along with the nitrite was able to significantly reduce METHB formation in a dose-dependent manner in both rats and humans but not in sheep.