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Joyce A Wahr

Publications and source records attributed to Joyce A Wahr.

5 recordsLinked to original sources
PubMed2003

Clinical potential of blood substitutes or oxygen therapeutics during cardiac surgery.

Several complications and unforeseen adverse side effects have colluded to keep commercially available blood substitutes or oxygen therapeutic agents tantalizingly "just out of reach." Because the three classes of agents under development have different oxygen-delivery mechanisms and side-effect profiles, each can be expected to have its own unique clinical applications, particularly in the cardiac surgery population. The fact that South Africa recently approved one HBOC for use as a transfusion alternative in patients with chronic anemia indicates that initial clinical use is near for a number of these agents. It is to be hoped that they will be used for several applications rather than just for a "transfusion alternative." Despite some frustrating limitations, all of these agents are antigen and pathogen free, have an acceptable side-effect profile, and have a long shelf life. Increasing volunteer-blood-donor shortages, coupled with increasing blood-transfusion needs, and expanding human immunodeficiency virus and hepatitis B and C epidemics, continue to fuel the demand for further development of these products. Transfusion alternatives will eventually become commercially available--the question is "when," not "if." Equally important, these agents' potential for serving as effective oxygen-delivery agents to ischemic tissues heralds an entirely new field of clinical investigation.

Blood Substitutes↗
PubMed2003

Reducing unnecessary cross-matching: a patient-specific blood ordering system is more accurate in predicting who will receive a blood transfusion than the maximum blood ordering system.

UNLABELLED: Most blood transfusions are given in the operating room. Adoption of the Maximum Surgical Blood Ordering Schedule in the 1970s reduced the amount of blood unnecessarily cross-matched, but the national cross-match-to-transfusion ratio remains at approximately two-to-one. We tested the ability of a patient-specific blood ordering system (PSBOS) to more accurately predict potential operative transfusion. All adult patients who had blood cross-matched before surgery (February through June 1999) for elective operative procedures at the University of Michigan Hospital were identified. Complex surgeries were excluded. Surgeons estimated the expected blood loss for their surgeries, and the expected postoperative hematocrit was calculated using the patient's blood volume, the surgeon-defined expected blood loss, and preoperative hematocrit. Lowest tolerated hematocrit was set at 21% except in patients with coronary artery disease or who were ASA physical status III or more (28%). Sensitivity, specificity, positive predictive value, and negative predictive value of the PSBOS were calculated. Our analysis included 178 cases in which blood was cross-matched before surgery, representing 69 different surgeries and 42 surgeons. Only 16% of patients received an intraoperative transfusion. Of the 156 patients that PSBOS predicted would not require an operating room transfusion, 139 were not transfused. Of the 21 patients PSBOS predicted would be transfused, 11 were. The sensitivity of the algorithm as tested was 41%, the specificity 93%, the positive predictive value was 55%, and the negative predictive value was 89%. We conclude that PSBOS, which includes patient and surgeon variables in transfusion prediction, is more accurate than the Maximum Surgical Blood Ordering Schedule, which uses only surgical procedure. IMPLICATIONS: Currently, many units of blood set aside for surgery are never required, resulting in extra work and expense for blood banks. A formula that included patient weight and hematocrit and typical surgery blood loss was used to predict who would require transfusions. We reduced the predicted number of patients who had blood set aside from 178 to 21.

Adolescent↗
PubMed2002

The use of bovine hemoglobin glutamer-250 (Hemopure) in surgical patients: results of a multicenter, randomized, single-blinded trial.

UNLABELLED: Hemoglobin-based oxygen carrier-201 (HBOC-201, hemoglobin glutamer-250 [bovine], Hemopure; Biopure Corporation, Cambridge, MA) is polymerized hemoglobin of bovine origin being developed as an oxygen therapeutic. In this study, we evaluated the tolerability of a single intraoperative dose of HBOC-201 in surgical patients. In a single-blinded, multicenter study, 81 patients were randomized to receive either a single infusion of HBOC-201 (55 patients) or an equivalent volume of lactated Ringer's solution (26 patients). Forty-two patients originally assigned to the HBOC-201 group received the entire planned treatment of only one of the following doses: 0.6, 0.9, 1.2, 1.5, 2.0, or 2.5 g/kg of body weight. Thirteen of the 55 patients in the HBOC-201-assigned group did not reach the trigger point for transfusion administration, and they were not included in the analysis. We studied clinical outcomes and compared hematologic findings, blood chemistry values, and blood use in the two treatment groups. There were no patient deaths in this study. No pattern of clinically significant laboratory abnormalities could be attributed to exposure to HBOC-201. In the HBOC-201 group, 2 patients had a transient increased concentration of serum transaminases and 6 had transient skin discoloration. One patient in the HBOC-201 group had mast cell degranulation with hypotension. Postoperatively, methemoglobin plasma concentrations increased in the HBOC-201 group in a dose-dependent manner, reaching maximal values of 3.7% +/- 3.2% (average of all doses given) on postoperative day 3. There was no difference in the mean number of allogeneic blood units transfused in the 2 groups (3.3 +/- 1.8 and 3.7 +/- 4.1 for the lactated Ringer's solution and HBOC-201 groups, respectively) over the course of hospitalization. The intraoperative administration of HBOC-201, up to a maximum of 245 g, was generally well tolerated. There was no relationship between HBOC-201 use and the number of allogeneic blood units transfused over the entire hospitalization course. The administration of HBOC-201 was associated with a delayed (third postoperative day) dose-dependent increase in the plasma methemoglobin concentration. We conclude that the intraoperative use of HBOC-201 was generally well tolerated. IMPLICATIONS: The intraoperative use of hemoglobin glutamer-250 (bovine) (HBOC-201, Hemopure was generally well tolerated. The administration of HBOC-201 was associated with a delayed increase in the plasma methemoglobin concentrations.

Adolescent↗
PubMed2002

Clinical potential of nonhemoglobin oxygen therapeutics in cardiac and general surgery.

Significant efforts have been made over the past 70 years to find a solution that could substitute for blood. Over the years, the focus has shifted to developing a solution capable of delivering oxygen to the tissues. Fluorocarbons (FC) are highly inert solutions with a high solubility for all gases, making them a prime candidate to become such an oxygen delivery agent. Although clinical research efforts into the use of these agents as substitutes for blood transfusions continue at present, the rapid disappearance of emulsified FCs from the vascular space and accumulation in the liver and spleen may well limit their usefulness as transfusion substitutes. Because of their ability to dissolve significant quantities of oxygen and carbon dioxide, these agents may be more attractive as oxygen delivery agents during periods of local or global organ ischemia, including preservation of organs for transplantation. FCs have also been tested in animal models of cardiopulmonary bypass, and may be efficacious in adsorbing the gases present in air emboli. Recently a second class of oxygen therapeutics (allosteric modifiers) has been developed, and these agents enhance oxygen delivery by shifting the oxygen dissociation curve to the right, thus increasing tissue PO(2). Allosteric modifiers have been shown to effectively shift the p50 of hemoglobin 10mm Hg at clinically relevant dosages, and have been shown (in animal models) to reduce cerebral infarct size following carotid ligation and to improve myocardial performance following myocardial ischemia. Despite significant research efforts, however, none of the solutions under development are currently approved for clinical use by the Food and Drug Administration, with the exception of myocardial contrast imaging agents.

Animals↗