Relation between number of cardiovascular risk factors/events and noninvasive Doppler ultrasound assessments of aortic compliance

BACKGROUND: Health care episodes are traditionally created for a specific condition using defined relevant diagnosis and procedure codes and a start and end period. Our goal is to use 1987 to 1989 medical claims data to create distinct episodes of care as a result of injury. METHODS: Claims for 102,000 people younger than 65 years were obtained from Medstat Systems, Inc. Injury claims were identified by International Classification of Diseases, 9th Revision, Clinical Modification diagnosis codes and separated into 10 body regions. Using linked inpatient and outpatient claims data, we established clear zones--a maximum period for a return visit for medical treatment--for each of 10 body regions injured by hospitalization status. These clear zones were used to create episodes of injury. RESULTS: A total of 295,165 injury claims created 79,564 episodes of injury. Limb and trunk injuries typically have the most follow-ups in terms of number of claims and spacing between claims. Brain injuries, even for admitted patients, result in an average of fewer than two follow-up claims. On average, hospitalized patients require only one more follow-up than nonadmitted patients. CONCLUSIONS: This paper presents a method for identifying injury episodes using a medical claims database. The analysis suggests that follow-up to check for minor long-term sequelae of brain injury is rare.     

Residual dipolar couplings as new conformational restraints in isotropically 13C-enriched oligosaccharides

Closed-circuit anesthesia (CCA) has certain advantages such as decreased cost, decreased anesthetic gas pollution, improved inhalational gas humidity and temperature in comparison to conventional inhalational anesthesia using a high fresh gas flow, i.e. more than 2 L x min(-1), with a semi-closed breathing circuit. The main disadvantage of CCA is the possibility of hypoxic anesthetic gas delivery. This potentially lethal situation is caused by an insufficient oxygen flow rate for the body metabolism or by the accumulation of inactive gas, usually nitrogen, within the breathing circuit in spite of a sufficient oxygen concentration in the fresh gas supply to the breathing circuit. In the latter case, the accumulation of inactive gas may also lead an increased risk of awareness because of its dilution effect on the concentrations of inhalational anesthetics. We herein present a case of air contamination of the breathing circuit through a sampling line of an anesthetic gas monitor. The air caused a decrease in the oxygen concentration during closed circuit anesthesia.     

Procalcitonin as a marker of systemic inflammation after conventional or minimally invasive coronary artery bypass grafting

AIM: To undertake a review of cases from one dental advisory practice in England over a period of 5.5 years to provide a profile of the type of work undertaken. DESIGN AND SETTING: Compensation claims for dental negligence seen at one dental advisory practice between 1991 and 1996. METHODS: 437 claims were reviewed for: the nature of the complaint; defendant details; plaintiff details; method of funding; duration and outcome of claim. Comparisons were made with previously published data. The relationship between method of funding of a claim and the likelihood of the claim being successful was investigated. RESULTS: 28% of complaints concerned oral surgery and 24%, restorative procedures. In 72% of cases, the compensation claim was made directly against the dentist who had provided treatment for the patient. The majority of claims were gender and age biased; females (63%) and younger people (18-45 years of age) (68%) were more likely to bring actions for dental negligence. Only 3% involved elderly patients (> or = 60 years old). Claims supported by the government legal aid scheme were more likely to be withdrawn or rejected than those privately funded. Nearly all cases were completed in under one year (81%). CONCLUSIONS: Results are similar to previously published studies. A large proportion of claims concerned restorative or oral surgery procedures carried out in general or community practice.     

LAD-1 is absent in a subset of junctional epidermolysis bullosa patients

BACKGROUND: Awareness during anaesthesia has been estimated to occur in 0.2%-0.4% of patients undergoing general surgery. In Finland, according to the Patient Injury Act, compensation is paid for an injury caused by medical treatment. We have analysed the claims for compensation involving awareness under anaesthesia filed between May, 1987 and December, 1993. METHODS: Original claims, hospital notes, and expert advisor's comments as well as the comments of the anaesthesiologist in charge of the anaesthesia, and decisions of the Patient Injury Association, were reviewed. RESULTS: A total of 23363 claims of patient injury were made during the study period. Of these, 391 considered anaesthetic treatments, and there were four cases of awareness with recall. CONCLUSION: Claims of compensation for awareness during anaesthesia were surprisingly few, possible reasons of which are discussed. Compensations paid were low in comparison with some other countries.     

Partial cardiopulmonary bypass in rats for evaluating ischemia-reperfusion injury

The authors developed a miniaturized partial cardiopulmonary bypass model in rats by using membrane oxygenators. Sprague-Dawley rats underwent general anesthesia and tracheostomy for ventilation. Partial cardiopulmonary bypass was carried out through the jugular cannula (18 gauge) for venous blood drainage and through the femoral arterial cannula (24 gauge) at a flow of 50 ml/kg/min. Membrane oxygenators used in this study maintained arterial oxygen tensions (PaO2) at 300-500 mmHg and carbon dioxide tensions (PaCO2) at 25-35 mmHg, with a gas mixture of 95% O2 + 5% CO2 (n = 7) for at least 2 hr of bypass circulation. To test the feasibility of this system for investigation of ischemia-reperfusion injury, hypoxic challenges with gas mixtures of different oxygen concentrations were examined. After equilibration of the bypass circulation for 1 hr, the following gases were tested for 15 min: Group I, 95% air + 5% CO2 (FiO2 = 0.21, n = 5); Group II, 10% O2 + 5% CO2 + 85% N2 (FiO2 = 0.1, n = 5); and Group III, 95% N2 + 5% CO2 (FiO2 = 0, n = 5). Equilibrated PaO2 values after challenge with these gases for 15 min were as follows: Group I: 89.6 +/- 3.7, Group II: 53.8 +/- 1.4, Group III: 25.6 +/- 2.0 mmHg (p < 0.01 between Groups I and II, I and III, II and III; p < 0.01 vs. prehypoxic PaO2 values in all groups). PaO2 values returned to the previous level within 15 min after return to the standard gas mixture (95% O2 + 5% CO2) supply. This system provided stable cardiopulmonary bypass in rats for at least 2 hr and may be useful for investigation of ischemia-reperfusion injury.     

Channeling of three newly introduced antidepressants to patients not responding satisfactorily to previous treatment

OBJECTIVE: Trifluoromethane and CO are produced simultaneously during the breakdown of isoflurane and desflurane by dry CO2 absorbents. Trifluoromethane interferes with anesthetic agent monitoring, and the interference can be used as a marker to indicate anesthetic breakdown with CO production. This study tests representative types of gas monitors to determine their ability to provide a clinically useful warning of CO production in circle breathing systems. METHODS: Isoflurane and desflurane were reacted with dry Baralyme at 45 degrees C. Standardized samples of breakdown products were created from mixtures of reacted and unreacted gases to simulate the partial degrees of reaction which might result during clinical episodes of anesthetic breakdown using 1% or 2% isoflurane and 6% or 12% desflurane. These mixtures were measured by the monitors tested, and the indication of the wrong agent or a mixture of agents due to the presence of trifluoromethane was recorded and related to the CO concentration in the gas mixtures. RESULTS: When presented with trifluoromethane from anesthetic breakdown, monochromatic infrared monitors displayed inappropriately large amounts of isoflurane or desflurane. Agent identifying infrared and Raman scattering monitors varied in their sensitivity to trifluoromethane. Mass spectrometers measuring enflurane at mass to charge = 69 were most sensitive to trifluoromethane. CONCLUSION: Monochromatic infrared monitors were unable to indicate anesthetic breakdown via interference by trifluoromethane, but did indicate falsely elevated anesthetic concentrations. Agent identifying infrared and Raman monitors provided warning of desflurane breakdown via the interference of trifluoromethane by displaying the wrong agent or mixed agents, but may not be sensitive enough to warn of isoflurane breakdown Some mass spectrometers provided the most sensitive warnings to anesthetic breakdown via trifluoromethane, but additional data processing by some patients monitor units reduced their overall effectiveness.     

Optimal depth and duration of mild hypothermia in a focal model of transient cerebral ischemia: effects on neurologic outcome, infarct size, apoptosis, and inflammation

BACKGROUND and PURPOSE: Mild hypothermia is possibly the single most effective method of cerebroprotection developed to date. However, many questions regarding mild hypothermia remain to be addressed before its potential implementation in the treatment of human stroke. Here we report the results of 2 studies designed to determine the optimal depth and duration of mild hypothermia in focal stroke and its effects on infarct size, neurological outcome, programmed cell death, and inflammation. METHODS: Rats underwent a 2-hour occlusion of the left middle cerebral artery. In the first study (I) animals were kept (intraischemically) at either 37 degreesC (n=8), 33 degreesC (n=8), or 30 degreesC (n=8). Study II consisted of 4 groups: (1) controls (37 degreesC, n=10), (2) 30 minutes of hypothermia started at ischemic onset (33 degreesC, n=9), (3)1 hour (33 degreesC, n=8), and (4) 2 hours (33 degreesC, n=8). Brain temperature was measured by a thermocouple probe placed in the contralateral cortex. After suture removal, all animals were rewarmed and reperfused for 22 hours (I) or 70 hours (II). RESULTS: Mild hypothermia to 33 degreesC or 30 degreesC was neuroprotective (17+/-7% and 27+/-6%, respectively) relative to controls (53+/-8%, P<0.02), but 33 degreesC was better tolerated and recovery from anesthesia was faster. The neurological score of hypothermic animals was significantly better than that of controls (I & II) at both 24 and 72 hours postischemia except for the 30-minute group (II), which showed no improvement. In Study II, 2 hours of hypothermia reduced injury by 59%, 1 hour reduced injury by 84% whereas 30 minutes did not reduce injury. Normalized for infarct size, 2 hours of mild hypothermia decreased neutrophil accumulation by 57% whereas both 1 hour and 30 minutes had no effect. At 72 hours, 1 and 2 hours of mild hypothermia decreased transferase dUTP nick-end labeling (TUNEL) staining by 78% and 99%, respectively, and 30 minutes of hypothermia had no effect. CONCLUSIONS: Intraischemic mild hypothermia must be maintained for 1 to 2 hours to obtain optimal neuroprotection against ischemic cell death due to necrosis and apoptosis.     

Humidification during anesthesia

Humidification during anesthesia is important to prevent adverse changes in the upper airways and possible pulmonary compromise. These changes may take place in less than 1 hour using dry nonhumidified anesthetic gases. Consequently, some method of humidification should be employed for all but the shortest of surgical procedures requiring general anesthesia. Methods of humidification include the anesthesia breathing system itself, passive humidification or conservation of moisture (the use of HMEs), and active humidification. The simplest system providing good levels of humidification and warming of anesthetic gases is the Circle system, which uses a fresh gas flow of less than 2 L/min. Its success can be further enhanced by use of a coaxial circuit. The minimum levels of water output or humidity required in the breathing circuit remain controversial. It may be preferable to have a gas with a lower temperature and higher relative humidity because a warmer gas that is less saturated may result in increased desiccation from the upper airways. Humidification for neonatal and pediatric patients requires special consideration of resistance, work of breathing, and dead space. Further work is necessary with regard to the use of HMEs in this population of patients undergoing general anesthesia.     

Prevention of contamination with a heat-and-moisture-exchanger (HME) and bacterial filter during clinical anesthesia

Although the use of HME and bacterial filter is a common practice to protect the anesthesia machine as well as the patients from bacterial contaminants, there is no report demonstrating the effectiveness of this filter in clinical anesthesia setting. We evaluated the actual effectiveness of the filter during clinical use. While the anesthesia breathing circuit, two bacterial filters (BB 50 T, Nihon PALL) and anesthesia bag, which were sterilized with ethylen oxide gas (EOG), were connected to the anesthesia machine and used continuously for one week, EOG sterilized HME and bacterial filter (BB 25 A, Nihon PALL) were changed before each anesthesia. Culture samples were taken from the BB 25 A, the breathing circuit and the machine side of the BB 50 T. Of the 117 BB 25 A samples taken, 6 were positive for Micrococcus, alpha-Streptococcus, Bacillus, and Staphylococcus epidermidis. From 21 breathing circuit "internal" samples, one was positive for Bacillus, Staphylococcus epidermidis. But the contamination from outside sources was suspected, since all the BB 25 as used with this circuit were negative. Use of BB 25 A prevents contamination of the breathing circuit for a period of one week. If we use BB 25 A in every anesthesia case, the changing of the breathing circuit is unnecessary, reducing the cost and simplifying procedures during clinical practice.     

Use of the Physician Insurers Association of America database as a surveillance tool for diabetes-related malpractice claims in the U.S

OBJECTIVE: To examine the available national surveillance data on malpractice claims associated with diabetes and to determine the medical specialties having the highest number of claims and the classes and costs of filed claims relating to diabetes. RESEARCH DESIGN AND METHODS: Data was abstracted from the Data Sharing Reports (DSRs) of the Physicians Insurers Association of America (PIAA), as well as a search of the PIAA's computerized database for the period spanning 1 January 1985 to 31 December 1996. Data on numbers of claims, medical causes of loss, indemnity paid, demographics of claimants and physicians, severity, and medical specialties with diabetes-related claims were available. RESULTS: A total of 906 diabetes claims were reported to PIAA, and the total indemnity paid was $26,892,848. A significant downward trend (P = 0.004) was noted for the period between 1993 and 1996. Diabetes claimants were older and predominantly male, relative to all claimants. Ophthalmology, internal medicine, and general and family practice had the highest rates of reported claims at 16.5, 13.6, and 13.4 diabetes claims per 1,000 claims, respectively. Of the diabetes-related injuries, 44% occurred in the practitioners office, as compared with 27% for all claims. A greater proportion of diabetes claims were associated with the highest level of severity of injury with respect to all claims compiled by the PIAA. CONCLUSIONS: The database of the PIAA can be a useful resource to monitor trends in diabetes-related malpractice. Further study into whether claims result from lack of adherence to practice guidelines is needed. Prevention programs designed to reduce the liability among high-risk specialties may also lead to improved care for the patient with diabetes.     

Absence of renal and hepatic toxicity after four hours of 1.25 minimum alveolar anesthetic concentration sevoflurane anesthesia in volunteers

Sevoflurane is degraded by CO2 absorbents to Compound A. The delivery of sevoflurane with a low fresh gas flow increases the generation of Compound A. The administration of Compound A to rats can produce injury to renal tubules that is dependent on both the dose and duration of exposure to Compound A. The present study evaluated renal and hepatic function in eight volunteers after a 1-L/min delivery of 3% (1.25 minimum alveolar anesthetic concentration) sevoflurane for 4 h. Volunteers gave their informed consent and provided 24-h urine collections before and for 3 days after sevoflurane anesthesia. Urine samples were analyzed for glucose, protein, albumin, and alpha- and pi-glutathione-S-transferase. Daily blood samples were analyzed for markers of renal and liver injury or dysfunction. Circuit Compound A and plasma fluoride concentrations were determined. During anesthesia, the average maximal inspired Compound A concentration was 39 +/- 6 (mean +/- SD). The median mean arterial pressure, esophageal temperature, and end-tidal CO2 were 62 +/- 6 mmHg, 36.5 +/- 0.3 degrees C, and 30.5 +/- 0.5 mm Hg, respectively. Two hours after anesthesia, the plasma fluoride concentration was 50 +/- 9 micromol/L. All markers of hepatic and renal function were unchanged after anesthesia (repeated-measures analysis of variance P > 0.05). Low-flow sevoflurane was not associated with renal or hepatic injury in humans based on unchanged biochemical markers of renal and liver function. IMPLICATIONS: Sevoflurane delivered in a 3% concentration with a fresh gas flow of 1 L/min for 4 h generated an average maximal Compound A concentration of 39 ppm but did not result in any significant increase in sensitive markers of renal function or injury, including urinary protein, albumin, glucose, and alpha- and pi-glutathione-S-transferase.     

Pre- and Postinjury Substance Misuse Among Veterans With Spinal Cord Injury.

Objective: To identify rates of substance misuse with onset before and after spinal cord injury (SCI) and to investigate whether patients with a history of substance misuse are more likely to report being intoxicated at the time of injury. Participants: One hundred twenty-four veterans with traumatic SCIs. Measures: Alcohol and nonalcohol psychoactive substance use disorder (PSUD) sections of the Structured Clinical Interview for DSM-III-R. Results: Forty (32%) had a lifetime PSUD. Of those, 55% recalled the onset of their PSUD occurring preinjury, 27.5% recalled the onset occurring postinjury, and 17.5% could not recall their age at onset. Compared with participants who reported postinjury onset of PSUD, those with reported preinjury onset were more likely to report intoxication at time of injury. No significant relation was found between intoxication at injury and presence of a lifetime PSUD. Conclusion: Intoxication at injury does not necessarily substantiate the existence of an underlying substance misuse problem. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of cuffed and uncuffed endotracheal tubes in young children during general anesthesia

BACKGROUND: Uncuffed endotracheal tubes are routinely used in young children. This study tests a formula for selecting appropriately sized cuffed endotracheal tubes and compares the use of cuffed versus uncuffed endotracheal tubes for patients whose lungs are mechanically ventilated during anesthesia. METHODS: Full-term newborns and children (n = 488) through 8 yr of age who required general anesthesia and tracheal intubation were assigned randomly to receive either a cuffed tube sized by a new formula [size(mm internal diameter) = (age/4) + 3], or an uncuffed tube sized by the modified Cole's formula [size(mm internal diameter) = (age/4) + 4]. The number of intubations required to achieve an appropriately sized tube, the need to use more than 21.min-1 fresh gas flow, the concentration of nitrous oxide in the operating room, and the incidence of croup were compared. RESULTS: Cuffed tubes selected by our formula were appropriate for 99% of patients. Uncuffed tubes selected by Cole's formula were appropriate for 77% of patients (P < 0.001). The lungs of patients with cuffed tubes were adequately ventilated with 2 1.min-1 fresh gas flow, whereas 11% of those with uncuffed tubes needed greater fresh gas flow (P < 0.001). Ambient nitrous oxide concentration exceeded 25 parts per million in 37% of cases with uncuffed tubes and in 0% of cases with cuffed tubes (P < 0.001). Three patients in each group were treated for croup symptoms (1.2% cuffed; 1.3% uncuffed). CONCLUSIONS: Our formula for cuffed tube selection is appropriate for young children. Advantages of cuffed endotracheal tubes include avoidance of repeated laryngoscopy, use of low fresh gas flow, and reduction of the concentration of anesthetics detectable in the operating room. We conclude that cuffed endotracheal tubes may be used routinely during controlled ventilation in full-term newborns and children during anesthesia.     

Birth trauma. A five-year review of incidence and associated perinatal factors

OBJECTIVE: To determine the current incidence of clavicular fracture (CF), facial nerve injury (FNI) and brachial plexus injury (BPI) and identify the existence, if any, of associated perinatal factors with each injury. STUDY DESIGN: A case-controlled study design was selected and the study conducted for births between January 1, 1985 and January 1, 1990, at Christ Hospital and Medical Center, a tertiary care center with level III perinatal services in suburban Chicago. Among a population of 19,370 consecutive deliveries, we identified the occurrences of CP, FNI and BPI by database search, and maternal and neonatal chart reviews. A control group was randomly selected. Maternal, labor, delivery and neonatal variables were then compared between the birth trauma and control groups for each specific injury. RESULTS: The incidence per 1,000 live births and per 1,000 live-born cephalic singletons delivered vaginally for CF was 4.5 and 5.7; for FNI, 0.6 and 0.7; and for BPI, 0.9 and 1.1, respectively. To varying degrees, the data demonstrate that the occurrences of these injuries are associated significantly more often with prolonged gestation, epidural anesthesia, prolonged second stage of labor, oxytocin use, forceps delivery, shoulder dystocia, macrosomia, low Apgar scores and a previous maternal obstetric history of macrosomia when compared to controls. Other significantly associated variables include the presence of meconium in labor and neonatal hyperbilirubinemia. Despite the presence of multiple perinatal factors that are individually associated statistically with the injured groups, multiple logistic regression analysis predicted 44.2% of CF's, none of the FNIs and only 19% of the BPIs. CONCLUSION: While multiple perinatal variables are statistically associated with the specific birth injuries studied, the use of multiple logistic regression analysis shows that the ability to predict these injuries is markedly limited.     

Health information on the Internet and people living with HIV/AIDS: Information evaluation and coping styles.

[Correction Notice: An erratum for this article was reported in Vol 26(5) of Health Psychology (see record 2007-13009-005). Table 1 mistakenly reported that the correlation between total Internet use and gender was r = .14, which, given the coding for gender, would be interpreted as women using the Internet more than men. However, as correctly stated in the text and indicated throughout the rest of the article, men used the Internet significantly more than women. The correct correlation between total Internet use and gender in Table 1 should therefore be r = .14.] Individuals who seek information on the Internet to cope with chronic illness may be vulnerable to misinformation and unfounded claims. This study examined the association between health-related coping and the evaluation of health information. Men (n = 347) and women (n = 72) who were living with HIV/AIDS and reported currently using the Internet completed measures assessing their Internet use. Health Web sites downloaded from the Internet were also rated for quality of information. HIV-positive adults commonly used the Internet to find health information (66%) and to learn about clinical trials (25%); they also talked to their physicians about information found online (24%). In a multivariate analysis, assigning higher credibility to unfounded Internet information was predicted by lower incomes, less education, and avoidant coping styles. People who cope by avoiding health information may be vulnerable to misinformation and unfounded claims that are commonly encountered on the Internet. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Does airway pressure release ventilation alter lung function after acute lung injury?

BACKGROUND: During airway pressure release ventilation (APRV), tidal ventilation occurs between the increased lung volume established by the application of continuous positive airway pressure (CPAP) and the relaxation volume of the respiratory system. Concern has been expressed that release of CPAP may cause unstable alveoli to collapse and not reinflate when airway pressure is restored. OBJECTIVE: To compare pulmonary mechanics and oxygenation in animals with acute lung injury during CPAP with and without APRV. DESIGN: Experimental, subject-controlled, randomized crossover investigation. SETTING: Anesthesiology research laboratory, University of South Florida College of Medicine Health Sciences Center. SUBJECTS: Ten pigs of either sex. INTERVENTIONS: Acute lung injury was induced with an intravenous infusion of oleic acid (72 micrograms/kg) followed by randomly alternated 60-min trials of CPAP with and without APRV. Continuous positive airway pressure was titrated to produce an arterial oxyhemoglobin saturation of at least 95% (FIO2 = 0.21). Airway pressure release ventilation was arbitrarily cycled to atmospheric pressure 10 times per minute with a release time titrated to coincide with attainment of respiratory system relaxation volume. MEASUREMENTS: Cardiac output, arterial and mixed venous pH, blood gas tensions, hemoglobin concentration and oxyhemoglobin saturation, central venous pressure, pulmonary and systemic artery pressures, pulmonary artery occlusion pressure, airway gas flow, airway pressure, and pleural pressure were measured. Tidal volume (VT), dynamic lung compliance, intrapulmonary venous admixture, pulmonary vascular resistance, systemic vascular resistance, oxygen delivery, oxygen consumption, and oxygen extraction ratio were calculated. MAIN RESULTS: Central venous infusion of oleic acid reduced PaO2 from 94 +/- 4 mm Hg to 52 +/- 9 mm Hg (mean +/- 1 SD) (p < 0.001) and dynamic lung compliance from 40 +/- 6 mL/cm H2O to 20 +/- 6 mL/cm H2O (p = 0.002) and increased venous admixture from 13 +/- 3% to 32 +/- 7% (p < 0.001) in ten swine weighing 33.3 +/- 4.1 kg while they were spontaneously breathing room air. After induction of lung injury, the swine received CPAP (14.7 +/- 3.3 cm H2O) with or without APRV at 10 breaths per minute with a release time of 1.1 +/- 0.2 s. Although mean transpulmonary pressure was significantly greater during CPAP (11.7 +/- 3.3 cm H2O) vs APRV (9.4 +/- 3.8 cm H2O) (p < 0.001), there were no differences in hemodynamic variables. PaCO2 was decreased and pHa was increased during APRV vs CPAP (p = 0.003 and p = 0.005). PaO2 declined from 83 +/- 4 mm Hg to 79 +/- 4 mm Hg (p = 0.004) during APRV, but arterial oxyhemoglobin saturation (96.6 +/- 1.4% vs 96.9 +/- 1.3%) did not. Intrapulmonary venous admixture (9 +/- 3% vs 11 +/- 5%) and oxygen delivery (469 +/- 67 mL/min vs 479 +/- 66 mL/min) were not altered. After treatment periods and removal of CPAP for 60 min, PaO2 and intrapulmonary venous admixture returned to baseline values. DISCUSSION: Intrapulmonary venous admixture, arterial oxyhemoglobin saturation, and oxygen delivery were maintained by APRV at levels induced by CPAP despite the presence of unstable alveoli. Decrease in PaO2 was caused by increase in pHa and decrease in PaCO2, not by deterioration of pulmonary function. We conclude that periodic decrease of airway pressure created by APRV does not cause significant deterioration in oxygenation or lung mechanics.     

Effect of pharmacokinetic sampling methods on aminoglycoside dosing in critically ill surgery patients

BACKGROUND: Airway obstruction after anesthesia may be caused or exaggerated by residual neuromuscular block, with loss of muscle support for collapsible upper airway structures. METHODS: Six male volunteers were studied before treatment, during stable partial neuromuscular block with vecuronium at a mean train-of-four (TOF) ratio of 50% (95% CI, 36-61%), and after reversal by neostigmine. Catheter-mounted transducers were placed in the pharynx and esophagus to estimate, respectively, the upper airway resistance, and the work of breathing (calculated as the time integral of the inspiratory pressure developed by the respiratory muscles, esophageal pressure time product) during quiet breathing, during breathing 5% carbon dioxide, and while breathing with an inspiratory resistor. Breathing with pressure at the airway opening held at pressures from -5 to 40 cm H2O were also tested to assess airway collapsibility. RESULTS: Although breathing through a resistor increased upper airway resistance from 1.2 (0.67, 1.72) cm H2O x l(-1) x s to 2.5 (1.32, 3.38) cm H2O x l(-1) x s, and carbon dioxide stimulation reduced resistance to 0.8 (0.46, 1.33) cm H2O x l(-1) x s, no effect of partial neuromuscular block (mean TOF ratio, 52%) on upper airway properties could be shown. CONCLUSIONS: Neuromuscular block with a TOF ratio of 50% can be present yet clinically difficult to detect in patients recovering from anesthesia. This degree of block has no effect on airway patency in volunteers, even during challenge. Airway obstruction during recovery from anesthesia thus is more likely to be caused by residual effects of general anesthetic agents or centrally acting analgesics, either alone or perhaps in concert with residual neuromuscular block.     

Faulty washers and soiled micropipettors may generate false positive serological results

BACKGROUND: Serological markers such as HBsAg and anti-HIV may be present in serum at very high concentrations and this may give rise to erroneous diagnoses due to cross-contamination. OBJECTIVES: To investigate poor equipment maintenance and use, including contamination with human serum, as a potential source of erroneous assay results. STUDY DESIGN: The potential of microtitre plate washers and micropipettors to transfer material between microplate wells and between specimens was examined. For the study of micropipettors we recruited 19 UK diagnostic laboratories. RESULTS: Four out of seven plate washers in use, until adjusted, had the potential to cause false positive HBsAg reactions. The centering of the probes that delivered the wash fluid, delivery pressure, wash volume and the use of a pre-programmed card to direct the washing procedure were important variables. We investigated soiling of tip cones of micropipettors. In every laboratory human IgG could be detected in at least a third of eluates from micropipettor tip cones; only 31 (14%) of 222 showed no evidence of contamination with human serum. Only one laboratory submitted eluates devoid of specific antibodies. Anti-HAV was the marker most commonly found (n = 68), followed by HBsAg (n = 27) and anti-HIV (n = 20). Seven micropipettor eluates from two laboratories were radioactively contaminated. CONCLUSIONS: Recommended precautions are regular checking, cleaning and servicing of equipment, care in interpreting weak reactions, reference back to serum left on the clot of the original specimen and testing of a follow up specimen. Poorly maintained immunoassay equipment can readily generate false positive results due to low-level cross-contamination, particularly with the current highly sensitive HBsAg and anti-HIV assays.     

Desflurane increases pulmonary alveolar-capillary membrane permeability after aortic occlusion-reperfusion in rabbits: evidence of oxidant-mediated lung injury

BACKGROUND: Pulmonary injury occurs after vascular surgery, with xanthine oxidase (an oxidant generator) released from reperfusing liver and intestines mediating a significant component of this injury. Because halogenated anesthetics have been observed to enhance oxidant-mediated injury in vitro, the authors hypothesized that desflurane would increase alveolar-capillary membrane permeability mediated by circulating xanthine oxidase after thoracic occlusion and reperfusion. METHODS: Rabbits were assigned to one of five groups: aorta occlusion groups administered desflurane (n=14), desflurane and tungstate (xanthine oxidase inactivator, n=12), fentanyl plus droperidol (n=13), and two sham-operated groups (desflurane, n=7 and fentanyl plus droperidol, n=7). Aortic occlusion was maintained for 45 min with a balloon catheter, followed by 3 h of reperfusion. Alveolar-capillary membrane permeability was assessed by measurement of bronchoalveolar lavage fluid protein. Xanthine oxidase activity was determined in plasma and lung tissue. Ascorbic acid content (an antioxidant) was determined in lung tissue. RESULTS: Desflurane was associated with significantly increased alveolar-capillary membrane permeability after aortic occlusion-reperfusion when compared with the fentanyl plus droperidol anesthesia or sham-operated groups (P < 0.05). Inactivation of xanthine oxidase abrogated the alveolar-capillary membrane compromise associated with desflurane. Although significantly greater than for sham-operated animals, plasma xanthine oxidase activities released after aortic occlusion-reperfusion were not different between the two anesthetics. There were no anesthetic-associated differences in lung tissue xanthine oxidase activity. However, desflurane anesthesia resulted in a significant reduction in lung ascorbic acid after aortic occlusion-reperfusion compared with the sham-operated animals. CONCLUSIONS: Desflurane anesthesia increased xanthine oxidase-dependent alveolar-capillary membrane compromise after aortic occlusion-reperfusion in concert with depletion of a key tissue antioxidant.