Pilot study of oxygen transport rate of banked red blood cells.

BACKGROUND AND OBJECTIVES: Dynamic oximetry provides a new way to assess the effect of blood storage on the oxygen transport rate (OTR). MATERIALS AND METHODS: In dynamic oximetry, the rate at which oxyhemoglobin becomes deoxyhemoglobin is measured optically, thereby, indirectly measuring the rate at which oxygen leaves the red blood cell (RBC) making it available for transfer to tissues. Extending the physiologic diffusion time in an in vitro apparatus, consisting of a diffusion system and gas exchanger capable of controlling the surface area and the time of exposure for oxygenation and deoxygenation, makes OTR measurement feasible. Eight normal blood donor units, collected in adenine, dextrose, sorbitol, sodium chloride and mannitol , were stored for 8 weeks under standard conditions and serially sampled for OTR. RESULTS: We report that the OTR at the time of blood bank donation appears to be singular for each donor, that the interdonor differences are maintained over time, and that the individual OTR increased 1.72-fold (95% CI 1.51, 1.95) over 8 weeks, adjusting for sex, age and plasma cholesterol level. CONCLUSION: Oxygen transport rate increases during storage; blood units with similar haemoglobin content may have significant differences in OTR. Studies examining blood parameters at the time of donation and blood storage on patient outcomes should consider measuring OTR, as it may contribute to differences in observed efficacy of tissue oxygenation.

Effectiveness of immersion treatments with acids, trisodium phosphate, and herb decoctions in reducing populations of Yarrowia lipolytica and naturally occurring aerobic microorganisms on raw chicken.

Yarrowia lipolytica, one of the predominant yeasts in raw poultry, is believed to play a role in spoilage. This study was undertaken to investigate treatments to control the growth of Y. lipolytica on raw chicken stored at refrigeration temperature. Raw chicken wings inoculated with a mixture of five strains of Y. lipolytica isolated from raw poultry were dipped in solutions containing 2, 5, or 8% lactic acid, 2% lactic acid containing 0.2, 0.4, or 0.8% potassium sorbate or sodium benzoate, and 4, 8, or 12% trisodium phosphate solution. Populations of the yeast and total aerobic microorganisms were determined before and after treatment. Immersion of wings in 2% lactic acid (with or without 0.2% potassium sorbate or sodium benzoate) or 4% trisodium phosphate caused a significant (alpha = 0.05) reduction in numbers of Y. lipolytica and aerobic microorganisms. Treatment with 2% lactic acid containing 0.4 or 0.8% preservative did not result in additional significant reductions. Treatment of chicken wings with 2% lactic acid or 8% trisodium phosphate significantly reduced numbers of Y. lipolytica by 1.47 and 0.65 log10 cfu/g, respectively, and aerobic microorganisms by 2.60 and 1.21 log10 cfu/g, respectively, compared to controls. Growth of Y. lipolytica on wings stored at 5 degrees C for up to 9 days, however, was not affected by these treatments. Significant reductions in the population of Y. lipolytica occurred when the yeast was inoculated into 100% basil, marjoram, sage, and thyme decoctions, but not in 100% oregano or rosemary decoctions, held at 5 degrees C for 24 h. Treatment of chicken wings with 100% sage or thyme decoctions significantly reduced populations of Y. lipolytica but did not control its growth during storage at 5 degrees C for up to 9 days. The small, temporary decreases in numbers of Y. lipolytica and aerobic microorganisms resulting from immersion treatment of chicken wings with sage and thyme decoctions render these treatments of questionable value as preservation interventions.

Engineering specific cross-links in nucleic acids using glycol linkers.

One of the most convenient methods for generating oligonucleotides possessing intra- or interstrand cross-links is through incorporation of oligoethylene glycol bridges by solid-phase synthesis. The reagents are commercially available or can be synthesized in a few easy synthetic steps. Unlike many other DNA and RNA cross-links, aspects of the structural and thermodynamic impact of modifying nucleic acids with oligoethylene glycols have been studied. This unit covers protection, phosphitylation, and preparation of the glycol linker for oligonucleotide synthesis.

Effect of plasma cholesterol on red blood cell oxygen transport.

1. Oxygen (O2) transfer from the blood to tissues is a function of the red blood cell (RBC) O2 saturation (SO2), the plasma O2 content being negligible. Under conditions of increased tissue O2 demand, the SO2 of arterial blood does not change appreciably (97%); however, the SO2 of mixed venous blood, equal to that of the perfused tissues, can go as low as 20%. 2. Tissue O2 availability is limited by the exposure time to a RBC, which decreases under conditions of maximum stress (< 1 s). If the O2 unloading time was to increase significantly, because of a decrease in the RBC diffusion constant or an increase in the RBC membrane thickness, the RBC O2 unloading time would exceed tissue (e.g. cardiac) transit time and O2 transfer would be impaired. 3. Cholesterol constitutes the non-polar, hydrophobic lipid of the enveloping layer of the RBC membrane. As the cholesterol content of the RBC increases, the fluidity of the membrane decreases and the lipid shell stiffens. 4. Early studies demonstrated that high blood cholesterol concentrations were associated with reduced blood O2 transport; in essence, the haemoglobin dissociation curve was shifted to the left. 5. Current investigations have shown that the cholesterol RBC membrane barrier to O2 diffusion delayed O2 entry into the RBC during saturation and delayed O2 release from the RBC during desaturation. In an analysis of 93 patients divided by their cholesterol concentration into five groups, the percentage change in blood O2 diffusion was inversely proportional to the cholesterol concentration. 6. The RBC membrane cholesterol is in equilibrium with the plasma cholesterol concentration. It stands to reason that as the plasma cholesterol increases, the RBC membrane becomes impaired and O2 transport is reduced. 7. The implications of this new perspective on O2 transport include the ability to increase tissue oxygenation by lowering plasma cholesterol.

Plasma cholesterol: an influencing factor in red blood cell oxygen release and cellular oxygen availability.

BACKGROUND: A fairly immediate reduction in angina pectoris symptoms after cholesterol lowering has been described. Our previous findings in rabbits and in a four-patient human pilot study indicated the existence of an RBC membrane barrier to oxygen (O2) transport in the presence of hypercholesterolemia. Our current objective was to determine whether, and to what extent, the plasma cholesterol concentration is an influencing factor in RBC O2 release and cellular O2 availability. STUDY DESIGN: In an unique O2 diffusion analysis system, blood samples from 100 patients referred for lipid modification were analyzed. After 1 to 2 minutes of mixing in our diffusion analysis system, the next 1 to 2 minutes of circulation is comparable with 1 to 2 seconds of myocardial capillary flow. RBC O2 diffusion was defined by the depletion rate of total O2 content in blood from full O2 saturation (98%) to desaturation (approximately 60%). Relative tissue O2 availability was defined as the percentage decrease in O2 availability between the high-cholesterol group and the low-cholesterol group. RESULTS: The 100 patients were divided almost equally into two groups on the basis of plasma cholesterol ranges of 175 to 229 mg/dL (n=49) and 230 to 299 mg/dL (n = 51). The mean cholesterol concentrations and percentage increases in the high-cholesterol group over the low-cholesterol group were: for plasma, 206 +/- 0.3 and 256 +/- 0.4 mg/dL, 24.3% (p < 0.001); for RBCs, 93 +/- 0.2 and 106 +/- 0.2mg/dL, 14.0% (p < 0.001); and for RBC membranes, 41 +/- 0.1 and 54 +/- 0.2mg/dL, 31.7% (p < 0.001). The blood O2 diffusion curves were distinctly different between the high- and the low-cholesterol groups (p < 0.05). Blood O2 diffusion, defined by the blood O2 diffusion curves, was inversely proportional to the plasma, RBC, and RBC-membrane cholesterol concentrations. The relative tissue O2 availability, after a circulation period of more than 3 minutes in the diffusion system, showed a decrease of 17.5% (p < 0.05) between the plasma cholesterol groups. In comparing the two plasma cholesterol concentration extremes of less than 200mg/dL (n= 14) and greater than 275 mg/dL (n= 11) after a circulation period of more than 3 minutes in the diffusion system, we found a decrease in relative tissue O2 availability of 35.8% (p < 0.05). CONCLUSIONS: The plasma cholesterol concentration may be an influencing factor in RBC-membrane cholesterol content, which, in turn, may regulate RBC-membrane O2 transport, RBC O2 release, and cellular O2 availability. The implications of this work include the addition of angina pectoris control to the indications for appropriate lipid modification and the development of an in vitro blood stress test to replace patient cardiac stress testing.

A novel device for measuring the effect of cholesterol on the release of oxygen from red blood cells into myocardial tissue.

A novel method has been devised to measure the effect of cholesterol on the release of oxygen (O2) from the red blood cell (RBC) into a tailored environment, which can be made to mimic myocardial tissue. Cholesterol affects the cell membrane of the RBC and thus the release of O2 into tissue. While this is true of all tissue, the myocardium is especially sensitive because of its critical nature, its high O2 requirements, and the shortness of time that arterial blood spends in the muscle. Calculations are presented that show that the release time for O2 from RBCs is close to the residence time of the RBC in the coronary system. Sequential measurements of blood oxygen saturation (SO2) are made when oxygenated blood is subjected to conditions similar to those in the myocardium. The natural logarithm of the relative value of the SO2 at time t compared with the initial value of the SO2 can be fitted to a straight line whose slope is proportional to the parameters of the RBC membrane, the sample size, the hematocrit, and the diffusion parameters of the apparatus. This value is used to estimate the effects of cholesterol-lowering treatments on O2 release. This test will serve as a valuable adjunct to or replacement for stress tests in the evaluation of coronary artery disease, especially in patients whose physical conditions make standard stress testing painful or risky.

Predictors of intussusception in young children.

OBJECTIVE: To identify predictors of intussusception in young children. DESIGN: A retrospective cross-sectional study. SETTING AND PATIENTS: A consecutive sample of children younger than 5 years on whom contrast enemas were performed because of suspected intussusception seen at an urban children's hospital from 1990 to 1995. METHODS: We evaluated historical, clinical, and radiographic variables. Variables documented in 75% or more of the medical records and associated with intussusception (P< or =.20) in the univariate analysis were evaluated in a multiple logistic regression analysis. Variables retaining significance (P< or =.05) in the multivariate analysis were considered independent predictors of intussusception. We used bootstrap resampling techniques to validate the multivariate model. RESULTS: Sixty-eight (59%) of the 115 patients had intussusception. Univariate predictors of intussusception included male sex, age younger than 2 years, history of emesis, rectal bleeding, lethargy, abdominal mass, and a highly suggestive abdominal radiograph. In the multivariate analysis, we identified only 4 independent predictors (adjusted odds ratio; 95% confidence interval): a highly suggestive abdominal radiograph (18.3; 4.0-83.1), rectal bleeding (17.3; 2.9-104.0), male sex (6.2; 1.2-32.3), and a history of emesis (13.4; 1.4-126.0). We identified 3 of these 4 variables (all but emesis) as independent predictors in more than 50% of 1000 bootstrap data samples. CONCLUSIONS: Rectal bleeding, a highly suggestive abdominal radiograph, and male sex are variables independently associated with intussusception in a cohort of children suspected of having this diagnosis. Knowledge of these variables may assist in clinical decision making regarding diagnostic and therapeutic interventions.

The potential for radiation-induced skin damage in interventional neuroradiological procedures: a review of 522 cases using automated dosimetry.

The Food and Drug Administration (FDA) has recommended the monitoring of radiation skin dose to patients during procedures having the potential for radiation damage. Radiologists need information about typical radiation doses during interventional procedures. The skin doses to patients during 522 interventional neuroradiological procedures have been monitored using an automated dosimetry system. Estimated entrance skin doses (ESD) were binned into 0.5 Gy increments and compared to FDA recommended thresholds for inclusion in the patient record. Percentages of procedures exceeding the above mentioned thresholds are presented. In addition, the percentage of dose in each view and the percentage of dose in fluoroscopic and digital angiographic modes are shown. Six percent of embolization procedures and one percent of cerebral angiograms are estimated to have potential for main erythema (ESD>6 Gy). All types of procedures have potential for temporary erythema and exceed the threshold for inclusion in the patient record (ESD> 1 Gy) at the 95% percentile. The types of procedures with most potential for skin damage also have significant percentages of dose in the digital angiographic mode. Thus, monitoring fluoroscopic time alone underestimates the potential for skin injury. On the other hand, combining the doses in the posterior-anterior and lateral views, tends to overestimate the potential for radiation injury.

Establishing a quality control program for an automated dosimetry system.

Automatic dosimetry systems can provide instantaneous dose and dose-rate information during fluoroscopic procedures as well as long-term records of patient doses. For this information to be useful, it is necessary that the accuracy of such systems be maintained through a rigorous quality control program. Daily and weekly quality control checks were performed on a PEMNET automated dosimetry system to determine its stability and the value of such tests in a quality control program. Weekly tests included monitoring the accuracy of the measured doses under a variety of conditions. The results of the tests indicate possible improvements in test methodology and real and potential sources of system failure and provide a statistical basis for setting quality control limits for future system monitoring.

Radiation dose in interventional fluoroscopic procedures.

Vascular interventional procedures carried out under fluoroscopic guidance often involve high radiation doses. Above certain thresholds, radiation can cause significant damage to the skin including hair loss and severe necrosis. Such damage has been reported by several investigators. Many attempts have been made to quantitate the radiation doses to the skin involved with these procedures, but dosimetry methods are often flawed. To improve the situation better monitoring of radiation doses, fluoroscopist education, and changes in technology and methods are needed.

Decreased blood oxygen diffusion in hypercholesterolemia.

BACKGROUND: Improvement of angina pectoris symptoms after cholesterol lowering has raised questions as to the underlying mechanisms. METHODS: Rabbit experiment: We compared arterial blood samples from New Zealand White cholesterol-supplemented rabbits (n = 6) with nonsupplemented rabbit samples (n = 4) in a closed-loop circulation diffusion system. The pH and partial pressures of oxygen (pO2) and carbon dioxide (pCO2) were measured continuously. The samples were first oxygen (O2) saturated (pO2, 160 mm Hg; pCO2, 4 mm Hg) and then desaturated in 100% nitrogen. Cholesterol levels were determined in whole blood, plasma (P Chol), red blood cells (RBCs), and RBC membranes. Human experiment: We exposed quadruple desaturated venous blood samples (n = 4) with P Chol levels of 87 to 400 mg/dL in a gas exchanger to capillary gas conditions (pO2, 23 mm Hg; pCO2, 46 mm Hg). After 15 minutes we performed blood gas analyses and compared our results to baseline values. RESULTS: In the rabbit experiment the cholesterol-supplemented group as compared to the control group showed higher plasma pO2 levels during the saturation phase and lower plasma pO2 levels during the desaturation phase. It also had a markedly increased RBC membrane cholesterol content: 121 +/- 3 (standard error of the mean [SEM]) mg/dL versus 22 +/- 1.7 mg/dL in the control group (P < .05). This barrier to RBC membrane O2 diffusion caused delayed O2 entry into the RBCs during saturation, with a higher plasma pO2, and delayed O2 release from the RBCs during desaturation, with a lower plasma pO2. In the human experiment the P Chol level was inversely correlated with the percentage change of O2 content in milliliters of O2 per deciliter of blood (P < .05). CONCLUSIONS: Increased RBC membrane cholesterol in hypercholesterolemia appears to decrease the transmembrane O2 diffusion rate.

Protecting the immunocompromised patient: the role of the hospital clinical engineer.

While the discipline of clinical engineering has long been limited to the area of medical equipment management, few areas in hospital engineering practice so closely meet the literal definition of "clinical" engineering as the care of the immunocompromised patient. Although ventilation has been the domain of the plant maintenance department, the increasing numbers of clinical engineers being given responsibility for plant functions, as well as the critical nature of the topic, make the care of the bone marrow transplant (BMT) patient an appropriate area of clinical engineering practice. Further, as clinical engineering branches out of the equipment management area, the clinical engineer can be truly termed the "hospital engineer".

Locus-specific analysis of human leukocyte antigen class I expression in melanoma cell lines.

Surface expression of human leukocyte antigen (HLA) class I antigens on melanoma lines was evaluated by locus-specific monoclonal antibodies (mAbs) with three different techniques: Fluorescence-activated cell sorting (FACS), immunohistochemistry with cytospin preparation (ICP), and complement-mediated cytotoxicity (CMC). Eleven HLA class I-expressing cell lines developed from metastases were used. Specific expression of HLA loci was examined under routine culture conditions and after 48-h incubation in interferon-gamma (IFN-gamma; 500 U/ml). Loss of allelic expression was seen in one line (586-MEL): Products of genes coding for HLA-A29 and -B44, in strong linkage disequilibrium, were not detectable. HLA-A antigens were consistently detected by all methodologies and minimally affected by pretreatment with IFN-gamma. HLA-B antigens were detectable in 8 of 11 lines by ICP and 3 of 11 lines by CMC. By FACS the supratypic specificity HLA-Bw6 was expressed at low levels in most lines (mean fluorescence 47.2 +/- 13.4 and rose to 259.8 +/- 45.9 after incubation with IFN-gamma; p < 0.001). HLA-Cw antigen detection by CMC correlated with HLA-B (p < 0.01), suggesting that down-regulation and sensitivity to IFN-gamma are shared by the two loci. This low expression of the HLA-B antigens may play a role in the evasion of the host immune response and its up-regulation may be useful in allowing tumor antigen recognition.

Splenic artery aneurysm rupture: the seventh instance of maternal and fetal survival.

Rupture of a splenic artery aneurysm is an uncommon occurrence but carries a high maternal and fetal mortality rate. This article presents the seventh case of both maternal and fetal survival and discusses some features salient to spontaneous rupture of a splenic artery aneurysm.