Development and validation of a sensitive LC-MS/MS method for the determination of D-serine in human plasma.

A validated LC-MS/MS method was developed for the determination of d -Serine in human plasma. The method was fully validated for use with human plasma samples and was linear from 0.19 nmol/ml to 25 nmol/ml. The coefficient of variation was ≤5% for the high QC standards and ≤8% for the low QC standards in plasma. d -Serine and l -serine were resolved by pre-column derivatization using (R)-1-Boc-2-piperidine carbonyl chloride as the derivatizating agent. The method was used to determine the concentration of d-serine in plasma samples obtained in patients receiving a continuous 5-day intravenous infusion of (R,S)-ketamine. The changes in d-Ser levels varied in the six patients, with circulating d-Ser levels increasing as much as 35% in a patient, while decreasing 20% in a patient. While only preliminary data, the results suggests the potential importance in determining the d-Ser levels in plasma and their potential role in physiological response.

Evaluation of porous networks of poly(2-hydroxyethyl methacrylate) as interfacial drug delivery devices.

Long-term implantable drug delivery devices are desirable to achieve rapid and reliable delivery of bioactive substances to the body. The limitation of most implantable devices is the resulting chronic inflammatory response and fibrous encapsulation of the implant, which prevents effective drug delivery for prolonged periods. One method of overcoming this problem is the addition of an intermediary that could prevent capsule formation. Biocompatible materials with interconnected pore structures greater than 8-10 microm have been shown to support the ingrowth and maintenance of vascularized tissue. In this investigation, we evaluate the efficacy of using porous hydrogel sponges for the tissue interface in an implantable drug delivery device. Porous networks of poly(2-hydroxyethyl methacrylate) (PHEMA) were synthesized using a thermally initiated free-radical solution polymerization. To characterize the microstructure of the PHEMA networks, scanning electron microscopy and mercury porosimetry were used. By altering the solvent fraction in the reaction mixture, PHEMA sponges were synthesized with interconnected pores ranging in size from from 6 to 15 microm with porosities of 55% to 87%. Following the in vitro evaluation, sponges were attached to the distal end of a 20-gauge catheter tubing, and implanted subcutaneously and intraperitoneally. After 5 months implantation, insulin was infused into the devices from external pumps and rapid insulin absorption was observed in conjunction with dramatic lowering of blood glucose levels. From histological evaluation of explanted devices, we observed highly vascularized tissue surrounding the mesenteric implants. These results indicate that it may be possible to use PHEMA sponges for a tissue intermediary for long-term implantable drug delivery devices.

Accuracy of the hemocue portable glucose analyzer in a large nonhomogeneous population.

Several studies have reported inconsistent results between HemoCue (HC) whole blood glucose measurements compared to plasma glucose. We selected a large patient population with diverse pathologies and healthy volunteers to evaluate HC. For this comparison, whole blood glucose concentration was measured using HC and referenced to laboratory plasma glucose. The population (n = 512) included healthy volunteers, diabetics, and patients with heart failure, liver failure, renal failure, renal and liver transplant, and other chronic diseases. Patients were on a wide variety of medications, vitamins, and food supplements. Venous blood samples were collected in tubes containing potassium oxalate and sodium fluoride. Comparison of the results was made using the method of Bland and Altman and ANOVA at three selected glucose ranges. The glucose measurement ([HC + laboratory]/2) ranges were 24-75, 76-129, and 130-404 mg/dL. A positive bias for all three glucose ranges was observed: 38 +/- 17 mg/dL for the high glucose group compared to 24 +/- 9 mg/dL and 22 +/- 10 mg/dL for the middle and low groups, respectively. In the high glucose group 90% of the values were within 10% (R = 0.97) of the laboratory reference values compared to 81% and 55% in the normal and low glucose groups, respectively. HC glucose measurements were generally within two SD from the laboratory plasma reference. HC consistently yielded lower whole blood glucose measurements than plasma with the largest differences seen in the low glucose range (29%). HC measured more consistently at the higher glucose concentrations and was 16% lower than plasma, although the mean absolute error was highest for that range. No significant effects in the bias could be attributed to disease while possible effects from instrument modifications by the manufacturer remain uncertain.

Serum leptin during recovery following maximal incremental and prolonged exercise.

This study investigated the delayed circulating leptin response to maximal and prolonged treadmill exercise. Six healthy untrained males performed three sessions after an overnight fast: control, maximal exercise, and prolonged exercise at 50% of maximal oxygen consumption. Blood samples were collected prior to exercise, at the end of exercise, and at 60, 120, 180, and 240 min following exercise and control sessions. Blood samples were analyzed for serum leptin, insulin, glucose, free fatty acids, and glycerol. Hemoglobin and hematocrit were measured to correct for plasma volume changes. Resting energy expenditure (REE) and body fat (BF) were also assessed. Immediately at the end of maximal and prolonged exercise, and during the 4 hours of recovery, serum leptin levels did not change significantly compared to their respective baseline values. At 240 min of recovery serum leptin decreased 7% and 9% (p>0.05) from the baseline in the maximal and prolonged sessions, respectively. In the control experiment serum leptin decreased 27% from the baseline at 240 min of the recovery (p < 0.05). No significant differences were found in leptin values between the control and exercise sessions. Control serum leptin was positively correlated (p < 0.05) to BF (r = 0.88) and glucose (r=0.96), and negatively correlated to REE (r= -0.81). In conclusion, maximal or prolonged exercise do not appear to have an influence on circulating serum leptin in the delayed (4 hr) post exercise recovery period.

Medical waste in the environment: do anesthesia personnel have a role to play?

STUDY OBJECTIVE: To conduct a feasibility study of the mechanics of recycling single-use anesthesia breathing systems and practices of anesthesiologists and nurse-anesthetists in a tri-state region. STUDY DESIGN: Two-part, open, prospective analysis using pre-printed questionnaire and cost/time analysis of labor and materials. SETTING: Questionnaire sent to 413 anesthesiology departments in Pennsylvania, New Jersey, and Delaware, and hospital/recycling facility for evaluation of time and cost. MEASUREMENTS AND MAIN RESULTS: Time to disassemble and sort the breathing circuits, analysis of costs and obtainable income from byproducts of recycling, and standard survey questionnaire concerning demographic characteristics of respondents and individual department/hospital practitioners. Data analysis included analysis of variance and Kruskal-Wallis tests. Pilot analysis: Sorting of circuits to economic component required ten minutes at an average cost of $1.60 Value of scraps obtainable was $3.44, leaving a gross margin of $1.84 for a box of 18 circuits. Benefit analysis: Extended reduction in the regulated medical waste in our operating room of 16,875 lb, saving $4,387.50 per year. With generation of revenue from scrap, the net gain is $5,994.64 per yr. Questionnaire: Majority (83%) of departments polled would participate in recycling implemented by suppliers. Most respondents would not consider (58%) recycling unless mandated by law. CONCLUSION: The program described is cost-effective and environmentally beneficial.

Preoperative glycopyrrolate: oral, intramuscular, or intravenous administration.

STUDY OBJECTIVE: To evaluate the effects of oral, intramuscular (i.m.) and intravenous (i.v. glycopyrrolate on oral and gastric secretions, and to assess how these routes of administration change intubating conditions. DESIGN: Randomized, double-blinded study. SETTING: University hospital operating room. PATIENTS: 37 ASA status I and II general anesthesia patients. INTERVENTIONS: Patients were randomized to receive glycopyrrolate or placebo just before surgery by three routes: oral, i.m., and i.v.. Glycopyrrolate was received once by one route and placebo by the other two routes. A placebo group received three placebos and no glycopyrrolate. MEASUREMENTS AND MAIN RESULTS: Mouth conditions and intubating conditions were qualitatively assessed by the patient and the intubating anesthesiologist. No difference between groups was noted. Oral and gastric volumes were measured and showed significantly less gastric volume for the i.v. group as compared with the other groups. Oral secretions were reduced in both the i.v. and i.m. groups when compared with placebo or glycopyrrolate administered orally. CONCLUSIONS: Preoperative glycopyrrolate is significantly more effective at reducing oral and gastric secretions if administered intravenously immediately before induction.

The effects of anesthetic technique on the hemodynamic response and recovery profile in coronary revascularization patients.

This study was undertaken to assess the effects of propofol (versus enflurane, fentanyl, and thiopental) on hemodynamic stability and recovery characteristics when used for maintenance of anesthesia during elective coronary artery bypass grafting (CABG) procedures. Ninety premedicated patients scheduled for elective coronary revascularization had anesthesia induced with fentanyl 25 micrograms/kg intravenously (i.v.). When the mean arterial blood pressure (MAP) increased 10% above preoperative baseline values, patients were randomized to receive one of four anesthetic treatments: enflurane, 0.25-2.0%; fentanyl, 10-20 micrograms/kg i.v. bolus doses; propofol, 50-250 micrograms.kg-1.min-1 i.v.; or thiopental, 100-750 micrograms.kg-1.min-1 i.v.. The maintenance anesthesia was titrated to achieve hemodynamic stability (i.e., maintain the MAP within 10% of the baseline values and heart rate [HR] within 20% of the baseline values). After bypass, anesthetic and cardiovascular drugs were titrated to maintain the MAP > 65 mm Hg and the cardiac index (CI) > 2.3 L.min-1.m-2. Recovery was assessed by noting the times at which patients first opened their eyes, responded to verbal communication, correctly responded to specific commands, underwent tracheal extubation, and were discharged from the intensive care unit (ICU). Although less intraoperative hypertension was noted in the propofol-treated patients (19 +/- 11 min vs 38 +/- 26 min, 30 +/- 24 min, and 30 +/- 23 min in the enflurane, fentanyl, and thiopental groups, respectively) (P = 0.04), the incidence of hypotension did not differ significantly among the groups. Vasopressor drugs were required more often during the prebypass period in fentanyl and propofol patients (4/22 and 5/23, respectively) compared to the thiopental group (0/21) (P < 0.05). During CPB, fentanyl-treated patients required vasoconstrictors more often than patients in the other three treatment groups (14/22 vs 6/24, 4/23, and 5/21 in the enflurane, propofol, and thiopental groups, respectively) (P < 0.01). Although fentanyl-treated patients had significantly greater requirements for inotropic support during weaning from CPB than propofol-treated patients (14/22 vs 7/23) (P < 0.038), there were no significant differences among the groups in the postbypass or ICU periods. Propofol-treated patients responded to verbal stimuli (2.1 +/- 1.3h vs 4.0 +/- 3.5h, 4.7 +/- 2.7h, and 5.6 +/- 3.6h in the enflurane, fentanyl, and thiopental groups, respectively) (P = 0.01) and followed commands earlier (propofol 7.3 +/- 5.2h vs enflurane 12.5 +/- 5.7h, fentanyl 13.1 +/- 6.6h, and thiopental 12.8 +/- 6.7 h) (P = 0.01).(ABSTRACT TRUNCATED AT 400 WORDS)

The effects of ketorolac and fentanyl on postoperative vomiting and analgesic requirements in children undergoing strabismus surgery.

Fifty-four ASA I and II children 1 to 10 yr of age undergoing strabismus surgery were randomized to receive in a double-blind fashion intravenous ketorolac (0.9 mg/kg), fentanyl (1 microgram/kg), or saline placebo (2 mL) during a standardized general anesthetic. Patients received no analgesic or antiemetics intraoperatively except for the study drug. Patients receiving ketorolac or placebo compared to fentanyl had a significantly lower incidence of postoperative vomiting in the day surgery unit (DSU) (P = 0.03) and overall (DSU plus home) (P = 0.005). The severity (number of episodes) of post-operative vomiting was significantly lower in the DSU, at home (first 24 h after hospital discharge), and overall for patients receiving ketorolac or placebo compared to fentanyl (P < 0.01). Postoperative pain scores and frequency of acetaminophen administration did not differ among the study groups, suggesting that the intraoperative use of ketorolac or fentanyl during pediatric strabismus surgery is unnecessary. No patients required fentanyl postoperatively, indicating that rectal acetaminophen administered in the postanesthesia recovery room provides sufficient analgesia for pediatric strabismus surgery. In conclusion, neither ketorolac nor fentanyl was associated with less postoperative vomiting or analgesic requirements compared to saline placebo administered during pediatric strabismus surgery. Fentanyl should be avoided, as it was associated with a significantly greater incidence of postoperative vomiting compared to ketorolac or placebo.

An improved nasal prong apparatus for end-tidal carbon dioxide monitoring in awake, sedated patients.

We describe and evaluate a new apparatus that monitors end-tidal carbon dioxide (PETCO2) and augments the inspired oxygen concentration in awake, sedated patients. The unit was evaluated for its effectiveness as an oxygenation device and its accuracy as a predictor of PaCO2 through the correlation of PaCO2 with PETCO2. Twenty cardiac surgical patients, physical status ASA 2-4, participated in this study. The PETCO2 monitoring device consisted of a dual-prong nasal oxygen cannula and a 14-gauge intravenous catheter that was inserted into one limb of the oxygen supply tubing and connected to a Datex gas analyzer (Datex Instrumentation Corp, Helsinki, Finland) to measure PETCO2. The cross-over passage between the prongs was intentionally blocked with the end of a wooden-core cotton swab. The oxygen flow rates were randomly varied (2, 4, and 6 L/min) every 5 minutes, and values for PETCO2 as well as arterial blood samples for analysis of PaCO2 and PaO2 were obtained at the end of each 5-minute period. The accuracy of the system was assessed by comparing the PaCO2-PETCO2 differences (bias) at each oxygen flow rate. The ratios of PETCO2 compared with PaCO2 were 0.98, 0.94, and 0.85, with correlation coefficients of r = 0.81, 0.85, and 0.63, respectively. The PaO2 values were 114, 154, and 183 mm Hg for the corresponding nasal oxygen flow rates of 2, 4, and 6 L/min, respectively. This study indicates that this modified nasal cannula provides supplemental oxygen adequately and yields a satisfactory reflection of the PaCO2 depending on the oxygen flow rate delivered.

Denitrogenation in pregnancy.

This study measured nitrogen washout in ten pregnant and nine non-pregnant women to understand better how pregnancy effects denitrogenation. Nitrogen concentration was monitored continuously while the women breathed 100 per cent O2 for three minutes and took four deep breaths of 100 per cent O2 using a circle anaesthesia system and 8 L.min-1 fresh gas flow. Parturients achieved 95 per cent denitrogenation significantly (P less than 0.0005) faster than non-pregnant women (54.5 +/- 17.8 vs 110.8 +/- 35.7 sec). In parturients, denitrogenation for three minutes lowered expired N2 concentration to 1.0 +/- 0.2 per cent while four deep breaths lowered it to 5.1 +/- 1.7 per cent (P less than 0.0001). This difference, while statistically significant, is predicted to supply only 10-15 sec of extra protection against hypoxaemia, and thus is probably not clinically significant. The authors conclude that either two minutes of tidal breathing or four deep breaths of 100 per cent O2 provide adequate denitrogenation and similar protection against apnoeic hypoxaemia in normal parturients.