Enoxaparin for unstable angina and ancrod for cardiac surgery following heparin allergy

OBJECTIVE: To describe a patient who presented with heparin allergy and required alternate anticoagulation for unstable angina and coronary artery bypass surgery. To review therapeutic alternatives to porcine heparin for patients with hypersensitivity or intolerance to standard heparin anticoagulation. CASE SUMMARY: A 74-year-old man with a 15-year-old coronary artery bypass graft presented to the emergency room with unstable angina and was scheduled for urgent coronary artery revascularization. A bolus dose of porcine heparin was administered followed by a continuous infusion. Shortly afterward the patient developed a type I allergic reaction to the porcine heparin that was confirmed by rechallenge. Three alternatives to porcine heparin were tried, including bovine lung heparin, low-molecular-weight heparin (enoxaparin), and ancrod. The patient was found to be cross-sensitive to bovine lung heparin, but tolerated enoxaparin for unstable angina without cross-sensitivity. Anticoagulation for cardiopulmonary bypass was achieved with an infusion of ancrod that was later reversed with cryoprecipitate. The patient was discharged postoperatively on day 5 without the complication of excessive bleeding. DISCUSSION: Type I allergic reaction to unfractionated heparin is a rare occurrence and could be the result of a variety of factors. Possible causes for the reaction include a porcine protein, a preservative contained in the heparin solution, or a hapten formed between heparin and a plasma protein. We considered four alternatives to heparin anticoagulation: rush desensitization, bovine lung heparin, low-molecular-weight heparin, and ancrod. The patient was cross-sensitive to bovine lung heparin, but was able to tolerate low-molecular-weight heparin (enoxaparin). This was unexpected because enoxaparin is derived from unfractionated porcine heparin. Testing for cross-sensitivity had no value in this case, as two negative subcutaneous test doses were followed by dramatic reactions when the drugs were given intravenously. Although enoxaparin has been used for anticoagulation during bypass surgery, there is more experience with ancrod as an alternative to heparin. Repeat bypass surgery, which normally results in above-average blood loss, was successfully performed with a very low fibrinogen concentration (< 0.15 g/L) during ancrod anticoagulation. CONCLUSIONS: We conclude that ancrod was a safe and effective alternative to heparin for coronary artery bypass surgery in this patient in whom a heparin product had caused a hypersensitivity reaction. We discovered on two occasions that a negative subcutaneous test dose for heparin allergy did not predict a severe type I allergic reaction when the heparin was later administered intravenously. Furthermore, we found that a low-molecular-weight heparin administered subcutaneously for a short period of time did not cause cross-sensitivity in a patient with a type I allergy to unfractionated heparin.     

Rat model for a vascularized laryngeal allograft

A new rat model was developed to reexamine the potential for laryngeal transplantation. The final anatomic derivation evolved from two earlier developmental phases. The first model had only a single arterial anastomosis; the second had an end-to-end arterial anastomosis with an end-to-end arteriovenous shunt. The final product employed an end-to-side arterial shunt and an end-to-side arteriovenous shunt for revascularization. The allografts were sited in tandem with the intact recipient larynges and were not innervated. A total of 16 animals were studied in phase 3; 2 died and the remaining 14 had a 64% arterial patency at intervals of 1 to 14 days. Our purpose is to detail the relevant technical considerations of this new model and compare it with historical controls.     

Pericyte loss and microaneurysm formation in PDGF-B-deficient mice

Platelet-derived growth factor (PDGF)-B-deficient mouse embryos were found to lack microvascular pericytes, which normally form part of the capillary wall, and they developed numerous capillary microaneurysms that ruptured at late gestation. Endothelial cells of the sprouting capillaries in the mutant mice appeared to be unable to attract PDGF-Rbeta-positive pericyte progenitor cells. Pericytes may contribute to the mechanical stability of the capillary wall. Comparisons made between PDGF null mouse phenotypes suggest a general role for PDGFs in the development of myofibroblasts.     

Leydig cell steroidogenesis in aging rats

Recent studies from our and other laboratories have shown that Leydig cells, the testicular cells responsible for testosterone production; become steroidogenically hypofunctional with age. Herein we review some of what we now know about the mechanisms by which this occurs, and some among the many remaining uncertainties in our understanding of Leydig cell aging. To help shed light on how Leydig cells age, we also briefly discuss the regulation of Leydig cell differentiation during puberty and of Leydig cell function in adult animals.     

Patient selection in outpatient parenteral antimicrobial therapy

Outcome data as well as reported anecdotal experience over the past 20 years indicate that any infection can be safely treated with parenteral antimicrobials outside the hospital setting. However, outpatient parenteral antimicrobial therapy (OPAT) is a reasonable option only when the final decision for patient selection is based on the judgment of a knowledgeable, experienced physician, and when an experienced qualified provider is available. Criteria to be considered include clinical status, patient acceptance, ability to comply with the plan of treatment, home environment, support systems, and reimbursement. Physician direction and participation in appropriate patient selection will become increasingly important as the growth of managed care increases the importance of cost-savings.     

Leukocyte Adhesion Deficiency Type II is a generalized defect of de novo GDP-fucose biosynthesis. Endothelial cell fucosylation is not required for neutrophil rolling on human nonlymphoid endothelium

Leukocyte Adhesion Deficiency Type II (LAD II) is a recently described syndrome and the two patients with this defect lack fucosylated glycoconjugates. These glycoconjugates include the selectin ligand, sialyl LewisX, and various fucosylated blood group antigens. To date, the molecular anomaly in these patients has not been identified. We localized the defect in LAD II to the de novo pathway of GDP-fucose biosynthesis, by inducing cell-surface expression of fucosylated glycoconjugates after exposure of lymphoblastoid cell lines from the LAD II patients to exogenous fucose. This defect is not restricted to hematopoietic cells, since similar findings were elicited in both human umbilical vein endothelial cells (HUVEC) and fibroblasts derived from an affected abortus. We have used these LAD II endothelial cells to examine the consequence of fucosylation of endothelial cells on the rolling of normal neutrophils in an in vitro assay. Neutrophil rolling on LPS-treated normal and LAD II HUVEC was inhibited by an E-selectin monoclonal antibody at both high and low shear rates. LAD II HUVEC lacking fucosylated glycoproteins supported leukocyte rolling to a similar degree as normal HUVEC or LAD II cells that were fucose-fed. At low shear rates, an L-selectin antibody inhibited neutrophil rolling to a similar degree whether the LAD II cells had been fucose-fed or not. These findings suggest that fucosylation of nonlymphoid endothelial cells does not play a major role in neutrophil rolling and that fucose is not a critical moiety on the L-selectin ligand(s) on endothelial cells of the systemic vasculature.