Effect of cerebral hypoxia on NMDA receptor binding characteristics after treatment with 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) in newborn piglets.

Previous studies have shown that hypoxia modifies the NMDA receptor/ion channel complex in cortical brain cell membranes of newborn piglets. The present study tests the hypothesis that blockade of the glutamate recognition site of the NMDA receptor with the competitive antagonist 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic acid (CPP) prevents modification of the receptor during hypoxia. Twenty seven anesthetized, ventilated newborn piglets were randomized into four groups: 7 normoxic (Nx), 6 CPP-treated normoxic (CPP-Nx), 8 hypoxic (Hx) and 6 CPP-treated hypoxic (CPP-Hx). Treatment groups received CPP 2 mg/kg i.v. The CPP-Hx group received CPP 30 min prior to hypoxia, which was induced by lowering the FiO2 to 5-7% for 1 h. Physiologic data showed no change in heart rate, blood pressure, arterial blood gas values, glucose or lactate following CPP administration. During hypoxia there was a significant decrease in PaO2, pH and an increase in lactate compared to baseline values. The CPP-Hx group had significantly higher lactate levels than the Hx group during hypoxia. P2 membrane fractions were prepared and thoroughly washed. Characteristics of the NMDA receptor ion channel were determined by [3H]MK-801 binding assays and characteristics of the glutamate recognition site by specific NMDA-displaceable [3H]glutamate binding assays. Brain tissue ATP and PCr levels confirmed tissue hypoxia, and were not preserved by CPP administration. [3H]MK-801 binding assays revealed that CPP treatment attenuated the hypoxia-induced decrease in the number of receptors (Bmax) and receptor binding affinity (Kd) during hypoxia. CPP treatment also decreased receptor affinity (increased Kd) for [3H]MK-801 binding during normoxia and hypoxia. Assays of [3H]glutamate binding revealed that hypoxia decreased both the Bmax and the Kd of the NMDA receptor for [3H]glutamate and both were preserved by CPP treatment prior to hypoxia. CPP had no effect on [3H]glutamate Bmax or Kd during normoxia. We conclude that hypoxia decreases the Bmax and Kd of the NMDA receptor glutamate recognition site for [3H]glutamate and the ion channel site for [3H]MK-801 in newborn piglets. These changes are prevented by CPP administration prior to hypoxia. The different effects of CPP binding during normoxia and hypoxia suggest a use-dependent mechanism for CPP binding during hypoxia, possibly through an hypoxia-induced alteration of the high-affinity binding site for CPP. During both normoxia and hypoxia CPP binding appeared to induce a conformational change in the receptor causing a decrease in binding affinity for [3H]MK-801. CPP administration did not preserve brain tissue ATP or PCr levels during hypoxia and may alter cellular metabolism in addition to its action at the NMDA receptor. However, even with depletion of the energy precursors ATP and PCr, and with higher lactate levels in the CPP-Hx group, CPP was able to maintain NMDA receptor binding characteristics during hypoxia and may decrease excitotoxic cellular damage from hypoxia.

Quality standard for the treatment of bacteremia. The Infectious Diseases Society of America.

OBJECTIVE: The objective of this quality standard is to optimize the treatment of bacteremia in hospitalized patients by ensuring that the antibiotic given is appropriate in terms of the blood culture susceptibility of the pathogen. Although this standard may appear to be minimal in scope, it is needed because appropriate antimicrobial treatment is not given in 5% to 17% of cases. To implement the standard, physicians, pharmacists, and microbiologists will need to devise a coordinated strategy. OPTIONS: We considered criteria for appropriate dosing, most cost-effective selection, proper antibiotic levels in serum, least toxicity, narrowest spectrum, specific clinical indications, and optimal duration of treatment. All these criteria were rejected as the basis for the standard because they were too controversial and too difficult to be applied by a nonphysician chart reviewer. In contrast, the selection of an antibiotic to which the pathogen is sensitive is a noncontroversial criterion and easy for a chart reviewer to apply. OUTCOMES: The standard is designed to reduce the incidence of adverse outcomes of septicemia such as renal failure, prolonged hospitalization, and death. EVIDENCE: Several well-designed clinical trials without randomization as well as case-controlled studies have confirmed the benefit of using an antibiotic that is appropriate in light of the susceptibility of the isolate in blood culture. Prospective, randomized, placebo-controlled trials are not available. VALUES: Our premise is that the presence of bacteremia is a risk factor for serious adverse outcomes. We also believe that the administration of antibiotics must always be guided by the susceptibility report for the pathogen(s) obtained from blood cultures. This concern is more critical for pathogens from the blood than for those from most other body sites. We had evidence that susceptibility reports for pathogens from positive blood cultures were not always used properly. We used group discussion to reach a consensus among the members of the Quality Standards Subcommittee. BENEFITS, HARMS, AND COSTS: Through the implementation of this standard, at least 5% of bacteremias could be treated more appropriately. An unknown number of deaths would likely be prevented, and mortality from bacteremia treated inappropriately would probably be reduced. The primary undesirable feature of the standard is an increased workload of pharmacists and microbiologists. RECOMMENDATIONS: Treatment of bacteremia with an antibiotic that is appropriate in terms of the pathogen's blood-culture susceptibility is a minimal standard of care for all patients. VALIDATION: We consulted more than 50 experts in infectious diseases from the fields of medicine, surgery, pediatrics, obstetrics and gynecology, nursing, epidemiology, pharmacology, and government. In addition, the methods for its implementation were reviewed by the American Society of Hospital Pharmacists and were tested by one of the members of the Quality Standards Subcommittee. SPONSORS: The Quality Standards Subcommittee of the Clinical Affairs Committee of the Infectious Diseases Society of America (IDSA) developed the standard. The subcommittee was composed of representatives of the IDSA (Drs. Gross and McGowan), the Society for Hospital Epidemiology of America (Dr. Wenzel), the Surgical Infection Society (Dr. Dellinger), the Pediatric Infectious Diseases Society (Dr. Krause), the Centers for Disease Control and Prevention (Dr. Martone), the Obstetrics and Gynecology Infectious Diseases Society (Dr. Sweet), and the Association of Practitioners of Infection Control (Ms. Barrett). Funding was provided by the IDSA and the other cooperating organizations. This standard is endorsed by the IDSA.

Low serum levels of oral antimycobacterial agents in patients with disseminated Mycobacterium avium complex disease.

Twenty-seven human immunodeficiency virus-infected patients with disseminated Mycobacterium avium complex disease who were treated with oral antimycobacterial agents (clofazimine, ciprofloxacin, ethambutol, and rifampin) were studied to evaluate the usefulness of monitoring serum drug concentrations and testing in vitro susceptibility of M. avium complex (MAC) isolates. Twenty patients tolerated treatment with three or four antimycobacterial agents for at least 8 weeks; mycobacteremia was eradicated in 7 (35%). The in vitro susceptibilities of MAC isolates to antimycobacterial agents were similar for these 7 and for the 13 who did not respond to antimycobacterial treatment. Serum drug levels were below the expected range in 6 of the 7 whose mycobacteremia was cleared and in 9 of the 13 nonresponders (P = .41). These low serum concentrations of antimycobacterial drugs may be due to impaired drug absorption in patients with AIDS and disseminated MAC disease.