Use of failure-to-rescue to identify international variation in postoperative care in low-, middle- and high-income countries: a 7-day cohort study of elective surgery

Background

The incidence and impact of postoperative complications are poorly described. Failure-to-rescue, the rate of death following complications, is an important quality measure for perioperative care but has not been investigated across multiple health care systems.

Methods

We analysed data collected during the International Surgical Outcomes Study, an international 7-day cohort study of adults undergoing elective inpatient surgery. Hospitals were ranked by quintiles according to surgical procedural volume (Q1 lowest to Q5 highest). For each quintile we assessed in-hospital complications rates, mortality, and failure-to-rescue. We repeated this analysis ranking hospitals by risk-adjusted complication rates (Q1 lowest to Q5 highest).

Results

A total of 44 814 patients from 474 hospitals in 27 low-, middle-, and high-income countries were available for analysis. Of these, 7508 (17%) developed one or more postoperative complication, with 207 deaths in hospital (0.5%), giving an overall failure-to-rescue rate of 2.8%. When hospitals were ranked in quintiles by procedural volume, we identified a three-fold variation in mortality (Q1: 0.6% vs Q5: 0.2%) and a two-fold variation in failure-to-rescue (Q1: 3.6% vs Q5: 1.7%). Ranking hospitals in quintiles by risk-adjusted complication rate further confirmed the presence of important variations in failure-to-rescue, indicating differences between hospitals in the risk of death among patients after they develop complications.

Conclusions

Comparison of failure-to-rescue rates across health care systems suggests the presence of preventable postoperative deaths. Using such metrics, developing nations could benefit from a data-driven approach to quality improvement, which has proved effective in high-income countries.

Cardiovascular magnetic resonance assessment of acute cardiovascular effects of voluntary apnoea in elite divers

BACKGROUND

Prolonged breath holding results in hypoxemia and hypercapnia. Compensatory mechanisms help maintain adequate oxygen supply to hypoxia sensitive organs, but burden the cardiovascular system. The aim was to investigate human compensatory mechanisms and their effects on the cardiovascular system with regard to cardiac function and morphology, blood flow redistribution, serum biomarkers of the adrenergic system and myocardial injury markers following prolonged apnoea.

METHODS

Seventeen elite apnoea divers performed maximal breath-hold during cardiovascular magnetic resonance imaging (CMR). Two breath-hold sessions were performed to assess (1) cardiac function, myocardial tissue properties and (2) blood flow. In between CMR sessions, a head MRI was performed for the assessment of signs of silent brain ischemia. Urine and blood samples were analysed prior to and up to 4 h after the first breath-hold.

RESULTS

Mean breath-hold time was 297 ± 52 s. Left ventricular (LV) end-systolic, end-diastolic, and stroke volume increased significantly (p < 0.05). Peripheral oxygen saturation, LV ejection fraction, LV fractional shortening, and heart rate decreased significantly (p < 0.05). Blood distribution was diverted to cerebral regions with no significant changes in the descending aorta. Catecholamine levels, high-sensitivity cardiac troponin, and NT-pro-BNP levels increased significantly, but did not reach pathological levels.

CONCLUSION

Compensatory effects of prolonged apnoea substantially burden the cardiovascular system. CMR tissue characterisation did not reveal acute myocardial injury, indicating that the resulting cardiovascular stress does not exceed compensatory physiological limits in healthy subjects. However, these compensatory mechanisms could overly tax those limits in subjects with pre-existing cardiac disease. For divers interested in competetive apnoea diving, a comprehensive medical exam with a special focus on the cardiovascular system may be warranted.

TRIAL REGISTRATION

This prospective single-centre study was approved by the institutional ethics committee review board. It was retrospectively registered under ClinicalTrials.gov (Trial registration: NCT02280226 . Registered 29 October 2014).

[Perioperative risk and mortality after major surgery]

Although anesthesia-associated mortality has been significantly reduced down to 0.00068-0.00082% over the last decades, recent studies have revealed a high perioperative mortality of 0.8- 4%. Apart from anesthesia and surgery-induced major complications, perioperative mortality is primarily negatively influenced by individual patient comorbidities. These risk factors predispose for acute critical incidents (e.g., myocardial infarction); however, the majority of fatal complications are a result of slowly progressing conditions, particularly infections or the sequelae of systemic inflammation. This implicates a broad window of opportunity for the detection and treatment of slow-onset complications to improve the perioperative outcome. The term "failure to rescue" (FTR), i.e., the proportion of patients who die from major complications compared to the number of all patients with complications, has been introduced as a valid indicator for the quality of perioperative care. Growing evidence has already shown that FTR is an underestimated factor in perioperative medicine accounting for or at least being involved in the development of postoperative mortality. While the incidence of severe postoperative complications amazingly does not show much variation between hospitals, FTR shows significant differences implying a major potential for improvement. With 14 million surgical procedures per year in Germany, a postoperative mortality of approximately 1% and an avoidable FTR rate of 40% mean that there are an estimated 60,000 preventable deaths per year. Hence, in the future it will be imperative to (1) identify patients at risk, (2) to prevent the development of postoperative complications with the use of adequate adjunctive therapeutic strategies, (3) to establish surveillance and monitoring systems for the early detection of postoperative complications and (4) to treat postoperative complications efficiently and in time when they arise.

Preoperative abnormalities in serum sodium concentrations are associated with higher in-hospital mortality in patients undergoing major surgery

BACKGROUND

Abnormal serum sodium concentrations are common in patients presenting for surgery. It remains unclear whether these abnormalities are independent risk factors for postoperative mortality.

METHODS

This is a secondary analysis of the European Surgical Outcome Study (EuSOS) that provided data describing 46 539 patients undergoing inpatient non-cardiac surgery. Patients were included in this study if they had a recorded value of preoperative serum sodium within the 28 days immediately before surgery. Data describing preoperative risk factors and serum sodium concentrations were analysed to investigate the relationship with in-hospital mortality using univariate and multivariate logistic regression techniques.

RESULTS

Of 35 816 (77.0%) patients from the EuSOS database, 21 943 (61.3%) had normal values of serum sodium (138-142 mmol litre(-1)) before surgery, 8538 (23.8%) had hyponatraemia (serum sodium ≤137 mmol litre(-1)) and 5335 (14.9%) had hypernatraemia (serum sodium ≥143 mmol litre(-1)). After adjustment for potential confounding factors, moderate to severe hypernatraemia (serum sodium concentration ≥150 mmol litre(-1)) was independently associated with mortality [odds ratio 3.4 (95% confidence interval 2.0-6.0), P<0.0001]. Hyponatraemia was not associated with mortality.

CONCLUSIONS

Preoperative abnormalities in serum sodium concentrations are common, and hypernatraemia is associated with increased mortality after surgery. Abnormalities of serum sodium concentration may be an important biomarker of perioperative risk resulting from co-morbid disease.

Do intravascular hypo- and hypervolaemia result in changes in central blood volumes?

BACKGROUND

Hypovolaemia is generally believed to induce centralization of blood volume. Therefore, we evaluated whether induced hypo- and hypervolaemia result in changes in central blood volumes (pulmonary blood volume (PBV), intrathoracic blood volume (ITBV)) and we explored the effects on the distribution between these central blood volumes and circulating blood volume (Vd circ).

METHODS

Six anaesthetized, spontaneously breathing Foxhound dogs underwent random blood volume alterations in steps of 150 ml (mild) to 450 ml (moderate), either by haemorrhage, retransfusion of blood, or colloid infusion. PBV, ITBV and Vd circ were measured using (transpulmonary) dye dilution. The PBV/Vd circ ratio and the ITBV/Vd circ ratio were used as an assessment of blood volume distribution.

RESULTS

68 blood volume alterations resulted in changes in Vdcirc ranging from -33 to +31%. PBV and ITBV decreased during mild and moderate haemorrhage, while during retransfusion, PBV and ITBV increased during moderate hypervolaemia only. The PBV/Vd circ ratio remained constant during all stages of hypo- and hypervolaemia (mean values between 0.20-0.22). This was also true for the ITBV/Vd circ ratio, which remained between 0.31 and 0.32, except for moderate hypervolaemia, where it increased slightly to 0.33 (0.02), P<0.05.

CONCLUSIONS

Mild to moderate blood volume alterations result in changes of Vd circ, PBV and ITBV. The ratio between the central blood volumes and Vd circ generally remained unaltered. Therefore, it could be suggested that in anaesthetized spontaneously breathing dogs, the cardiovascular system maintains the distribution of blood between central and circulating blood volume.

Pre-conditioning with synthetic CpG-oligonucleotides attenuates myocardial ischemia/reperfusion injury via IL-10 up-regulation

The aim of the study was to investigate whether pre-conditioning with CpG-oligodeoxynucleotides (CpG-ODN) may change cardiac ischemia/reperfusion (I/R)-dependent inflammation and modulates infarct size and cardiac performance. WT and TLR9-deficient mice were pre-treated with 1668-, 1612- and H154-thioate or D-Gal as control. Priming with 1668-thioate significantly induced inflammatory mediators in the serum and a concomitant increase of immune cells in the blood and spleen of WT mice. Furthermore, it induced myocardial pattern recognition receptors and pro-inflammatory cytokines peaking 2 h after priming and a continuous increase of IL-10. 16 h after pre-conditioning, myocardial ischemia was induced for 1 h. Infarct size determined after 24 h of I/R was reduced by 75 % due to pre-conditioning with 1668-thioate but not in the other groups. During reperfusion, cytokine expression in 1668-thioate primed mice increased further with IL-10 exceeding the other mediators by far. These changes were observed neither in animals pre-treated with 1612- or H154-thioate nor in TLR9-deficient mice. The 1668-thioate-dependent increase of IL-10 was further supported by results of a micro-array analysis 3 h after begin of reperfusion. Block of IL-10 signaling increased I/R size and prevented influence of priming. In the group pre-treated with 1668-thioate, cardiac function was preserved 24 h, 14 days and 28 days after I/R, whereas animals without pre-conditioning exhibited impaired heart function 24 h and 14 days after I/R. The excessive 1668-thioate-dependent IL-10 up-regulation during pre-conditioning and after I/R seems to be the key factor for reducing infarct size and improving cardiac function. This is in agreement with the finding that IL-10 block prevents cardioprotection by pre-conditioning.

Performance of a new pulse contour method for continuous cardiac output monitoring: validation in critically ill patients

BACKGROUND

A new calibrated pulse wave analysis method (VolumeView™/EV1000™, Edwards Lifesciences, Irvine, CA, USA) has been developed to continuously monitor cardiac output (CO). The aim of this study was to compare the performance of the VolumeView method, and of the PiCCO2™ pulse contour method (Pulsion Medical Systems, Munich, Germany), with reference transpulmonary thermodilution (TPTD) CO measurements.

METHODS

This was a prospective, multicentre observational study performed in the surgical and interdisciplinary intensive care units of four tertiary hospitals. Seventy-two critically ill patients were monitored with a central venous catheter, and a thermistor-tipped femoral arterial VolumeView™ catheter connected to the EV1000™ monitor. After initial calibration by TPTD CO was continuously assessed using the VolumeView-CCO software (CCO(VolumeView)) during a 72 h period. TPTD was performed in order to obtain reference CO values (COREF). TPTD and arterial wave signals were transmitted to a PiCCO2™ monitor in order to obtain CCO(PiCCO) values. CCO(VolumeView) and CCO(PiCCO) were recorded over a 5 min interval before assessment of CO(TPTD). Bland-Altman analysis, %(errors), and concordance (trend analysis) were calculated.

RESULTS

A total of 338 matched sets of data were available for comparison. Bias for CCO(VolumeView)-CO(REF) was -0.07 litre min(-1) and for CCO(PiCCO)-CO(REF) +0.03 litre min(-1). Corresponding limits of agreement were 2.00 and 2.48 litre min(-1) (P<0.01), %(errors) 29 and 37%, respectively. Trending capabilities were comparable for both techniques.

CONCLUSIONS

The performance of the new VolumeView™-CCO method is as reliable as the PiCCO2™-CCO pulse wave analysis in critically ill patients. However, an improved precision was observed with the VolumeView™ technique. CLINICALTRIALS.GOV IDENTIFIER: NCT01405040.

Infants born very preterm react to variations of the acoustic environment in their incubator from a minimum signal-to-noise ratio threshold of 5 to 10 dBA

INTRODUCTION

Very early preterm infants (VPIs) are exposed to unpredictable noise in neonatal intensive care units. Their ability to perceive moderate acoustic environmental changes has not been fully investigated.

RESULTS

Physiological values of the 598 isolated sound peaks (SPs) that were 5-10 and 10-15 dB slow-response A (dBA) above background noise levels and that occurred during infants' sleep varied significantly, indicating that VPIs detect them. Exposure to 10-15 dBA SPs during active sleep significantly increased mean heart rate and decreased mean respiratory rate and mean systemic and cerebral oxygen saturations relative to baseline.

DISCUSSION

VPIs are sensitive to changes in their nosocomial acoustic environment, with a minimal signal-to-noise ratio (SNR) threshold of 5-10 dBA. These acoustic changes can alter their well-being.

METHODS

In this observational study, we evaluated their differential auditory sensitivity to sound-pressure level (SPL) increments below 70-75 dBA equivalent continuous level in their incubators. Environmental (SPL and audio recording), physiological, cerebral, and behavioral data were prospectively collected over 10 h in 26 VPIs (GA 28 (26-31) wk). SPs emerging from background noise levels were identified and newborns' arousal states at the time of SPs were determined. Changes in parameters were compared over 5-s periods between baseline and the 40 s following the SPs depending on their SNR thresholds above background noise.

Repinotan, a selective 5-HT1A-R-agonist, antagonizes morphine-induced ventilatory depression in anesthetized rats

BACKGROUND

Spontaneous breathing during mechanical ventilation improves arterial oxygenation and cardiovascular function, but is depressed by opioids during critical care. Opioid-induced ventilatory depression was shown to be counteracted in anesthetized rats by serotonin(1A)-receptor (5-HT(1A)-R)-agonist 8-OH-DPAT, which cannot be applied to humans. Repinotan hydrochloride is a selective 5-HT(1A)-R-agonist already investigated in humans, but the effects on ventilation and nociception are unknown. In this study, we sought to establish (a) the effects of repinotan on spontaneous breathing and nociception, and (b) the interaction with the standard opiate morphine.

METHODS

The dose-dependent effects of repinotan, given alone or in combination with morphine, on spontaneous minute ventilation (MV) and nociceptive tail-flick reflex latencies (TFLs) were measured simultaneously in spontaneously breathing anesthetized rats. An additional series with NaCl 0.9% and the 5-HT(1A)-R-antagonist WAY 100 135 served as controls.

RESULTS

(a) Repinotan dose-dependently activated spontaneous breathing (MV, mean [95% confidence interval]; 53% [29%-77%]) of pretreatment level) and suppressed nociception (TLF, 91% maximum possible effect [68%-114%]) with higher doses of repinotan (2-200 μg/kg). On the contrary, nociception was enhanced with a small dose of repinotan (0.2 μg/kg; TFL, -47% maximum possible effect [-95% to 2%]). Effects were prevented by 5-HT(1A)-antagonist WAY 100 135. (B) Morphine-induced depression of ventilation (MV, -72% [-100% to -44%]) was reversed by repinotan (20 μg/kg), which returned spontaneous ventilation to pretreatment levels (MV, 18% [-40% to 77%]). The morphine-induced complete depression of nociception was sustained throughout repinotan and NaCl 0.9% administration. Despite a mild decrease in mean arterial blood pressure, there were no serious cardiovascular side effects from repinotan.

CONCLUSIONS

The 5-HT(1A)-R-agonist repinotan activates spontaneous breathing in anesthetized rats even in morphine-induced ventilatory depression. The potency of 5-HT(1A)-R-agonists to stimulate spontaneous breathing and their antinociceptive effects should be researched further.

The Entropy Module® and Bispectral Index® as Guidance for Propofol-Remifentanil Anaesthesia in Combination with Regional Anaesthesia Compared with a Standard Clinical Practice Group

This study was designed to investigate the impact of the Entropy Module® and Bispectral Index® (BIS) monitoring on drug consumption and recovery times compared with standard anaesthetic practice in patients undergoing orthopaedic surgery using a combination of regional and general anaesthesia as performed by an experienced anaesthesiologist. We hypothesised that electroencephalogram monitoring would lead to a lower drug consumption as well as shorter recovery times.

With institutional review board approval and written informed consent, 90 adult patients undergoing surgery to the upper or lower extremity received regional anaesthesia for post- and intraoperative pain control and were randomised to receive general anaesthesia by propofol/remifentanil infusion controlled either solely by clinical parameters or by targeting Entropy or BIS values of 50. Recovery times and drug consumption were recorded.

Data from 79 patients were analysed. Compared with standard practice, patients with Entropy or BIS monitoring showed a similar propofol consumption (standard practice 101±22 μg/kg/minute, Entropy 106±24 μg/kg/minute, BIS 104±20 μg/kg/minute) and showed similar Aldrete scores (10/10) one minute after extubation: 9.1∓0.3, 9.2±0.6 and 9.3±0.5, respectively. Time points of extubation were 7.3±2.9 minutes, 9.2∓3.9 minutes and 6.8±2.9 minutes, respectively, demonstrating a significant difference between Entropy and BIS (P=0.023).

Compared with standard practice, targeting an Entropy or BIS value of 50 did not result in a reduction of propofol consumption during general anaesthesia combined with regional anaesthesia as performed by an experienced anaesthesiologist in orthopaedic patients.

Multiplex real-time PCR and blood culture for identification of bloodstream pathogens in patients with suspected sepsis

Severe sepsis is increasingly a cause of death. Rapid and correct initial antimicrobial treatment reduces mortality. The aetiological agent(s) cannot always be found in blood cultures (BCs). A novel multiplex PCR test (SeptiFast (alpha version)) that allows identification of 20 bacterial and fungal species directly from blood was used, comparatively with BC, in a multicentre trial of patients with suspected bacterial or fungal sepsis. Five hundred and fifty-eight paired samples from 359 patients were evaluated. The rate of positivity was 17% for BC and 26% for SeptiFast. Ninety-six microorganisms were isolated with BC, and 186 microorganisms were identified with SeptiFast; 231 microorganisms were found by combining the two tests. Of the 96 isolates identified with BC, 22 isolates were considered to be contaminants. Of the remaining 74 non-contaminant BC isolates available for comparison with SeptiFast, 50 were identified as a species identical to the species identified with SeptiFast in the paired sample. Of the remaining 24 BC isolates for which the species, identified in the BC, could not be detected in the paired SeptiFast sample, 18 BC isolates were identified as a species included in the SeptiFast master list, and six BC isolates were identified as a species not included in the SeptiFast master list. With SeptiFast, 186 microorganisms were identified, 12 of which were considered to be contaminants. Of the 174 clinically relevant microorganisms identified with SeptiFast, 50 (29%) were detected by BC. More than half of the remaining microorganisms identified with SeptiFast (but not isolated after BC) were also found in routine cultures of other relevant samples taken from the patients. Future clinical studies should assess whether the use of SeptiFast is of significant advantage in the detection of bloodstream pathogens.

A single exposure to hyperbaric oxygen increases levels of circulating nucleosomes but does not induce mononuclear cell apoptosis in divers

Recent reports that hyperbaric oxygenation (HBO2) induced apoptosis in T-cell lines raised concern about a possible immunosuppressive effect of HBO2. Nucleosomes, DNA fragments wrapped around a histone core, have been observed in the circulation in diseases with increased cell death such as sepsis. Our aim was to investigate, whether HBO2 increases circulating nucleosomes as a marker of cell death and induces apoptosis of peripheral blood mononuclear cells in vivo. After informed consent 29 healthy volunteers were exposed to a 30 minute dive at 2.8 atmospheres absolute in a pressure chamber under resting conditions, while breathing 100% oxygen. Samples were obtained before and 24 hours after exposure. Circulating nucleosomes were measured in serum. Caspase-3 activation, Bcl-2 expression and mRNA of Bcl-2, Bcl-xl and Bax were analyzed in mononuclear cell extracts. Nucleosomes were elevated markedly 24h after exposure (p<0.01), while caspase-3 was not activated significantly. mRNA levels of Bcl-2, Bcl-xl and Bax were not altered. In conclusion, while evidence of elevated levels of circulating nucleosomes was found, mononuclear cell apoptosis was not affected by a single exposure to hyperbaric oxygen.

Severity of obstructive sleep apnoea/hypopnoea syndrome and subsequent waking EEG spectral power

It is well known that most patients with obstructive sleep apnoea/hypopnoea syndrome (OSAHS) suffer sleepiness, although the underlying mechanisms of this relationship remain unclear. The present study examined the relationship between nocturnal variables and the subsequent waking electroencephalogram (EEG), in order to determine if sleepiness was related to OSAHS severity and due to sleep fragmentation or to nocturnal hypoxaemia. In total, 12 moderate-to-severe OSAHS patients underwent a total sleep night followed by a 24-h period of sustained wakefulness where the waking EEG was measured every hour. The results showed that alpha (7.9-12.6 Hz) and beta (12.7-29.2 Hz) activities were strongly related to OSAHS severity, mainly reflected by the apnoea index. Moreover, spectral power in most of the waking EEG components was significantly correlated with nocturnal hypoxaemia indices, namely alpha and beta activity when hypoxaemia becomes severe. However, no correlation was found between the waking EEG and sleep fragmentation parameters. In conclusion, the present results suggest that the difficulty in maintaining an optimal level of alertness, reflected by a higher activity in awake alpha and beta bands (7.9-29.2 Hz) in obstructive sleep apnoea/hypopnoea syndrome, was better explained by: 1) the apnoea as opposed to the hypopnoea index; and 2) nocturnal hypoxaemia as opposed to sleep fragmentation.

Are OSAS patients impaired in their driving ability on a circuit with medium traffic density?

OBJECTIVES

Many studies have demonstrated that patients with Obstructive Sleep Apnea Syndrome (OSAS), a very common sleep-related breathing disorder, are usually impaired in their driving ability because of decreased sleep quality. However, most of the simulation procedures in laboratories are designed to create monotonic conditions with low traffic density, if any, thereby leading to a dramatic decrease in performance in OSAS patients because of the lack of stimulation. The aim of this study was therefore to evaluate driving abilities in OSAS patients involved in a driving simulation task with medium traffic density, in order to replicate as far as possible real world conditions. The behavioral and physiological attributes likely to predict driving performance in these patients were also investigated.

METHODS

After a normal night of sleep, 12 OSAS patients and 8 healthy controls performed 6 driving sessions during a 24-h period of sustained wakefulness. Driving performances (speed, lateral position, distances...) were measured and correlated to sleep parameters and to a waking EEG recorded during the task.

RESULTS

Compared to controls, patients showed difficulties in speed adjustment. However, they maintained longer inter-vehicle distances, including during overtaking. Their waking EEG, while driving, showed increased spectral power in theta (3.9-7.8Hz) but also in beta (12.7-29.2Hz) activity, alpha power (7.9-12.6Hz) being increased in both groups due to sustained wakefulness. Poor sleep indices were correlated to increased theta and beta activities, as well as to more cautious behavior.

DISCUSSION

In medium traffic density conditions, driving performance in OSAS patients remained at near normal levels, but with more cautious behavior than controls. This could be the result of a bigger effort to stay awake, as suggested by an increased beta activity in these patients.

[Emergency physician and AutoPulse--a good duo in preclinical emergency services?: case example and report on experience]

Survival rates after cardiac arrest remain poor despite substantial efforts to advance the cardiopulmonary resuscitation algorithm in the last decades. Recent changes in the resuscitation guidelines in 2005 focused on minimizing interruptions during chest compressions. The aim to provide optimal chest compressions led to the development of automated mechanical chest compression devices, one of which is the AutoPulse resuscitation system. A case of successful use of the AutoPulse system in a 66-year-old patient with sudden cardiac arrest is presented and a review is given of more than 3 years experience in the routine use of this mechanical device for CPR in the emergency medical system in Bonn. Based on this experience, the AutoPulse system is considered to be a safe and effective technical advancement that under certain CPR conditions can be a helpful tool and provide an increased quality of chest compressions.

Effects of Age and Task Complexity on EEG and Performance in Relation to Psychological States

The purpose of the present study is to analyse the effects of task complexity on the EEG spectral parameters and the extent to which age modulates this relationship. Subjects were divided into a junior and a senior group and engaged in a simple and a complex version of “Go/No go” tasks. Cognitive, subjective and electrophysiological data were combined. Our results indicated that there was an increase in alpha power over time only in the junior group in the simple task and the senior group in the complex one, suggesting that, depending on age, the increase in alpha band vary in a different way according with the degree of task complexity and could reflect some different phenomena. Cognitive performance were independent of age but for the main dimensions of motivation, seniors had higher scores, and they were less sleepy than juniors. Finally, this study showed correlations between cognitive performance, subjective evaluations and electrophysiological measures, and their value for understanding the subject’s engagement in a task.

Interleukin-6 enhancement after direct autologous retransfusion of shed thoracic blood does not influence haemodynamic stability following coronary artery bypass grafting

BACKGROUND

Direct autologous retransfusion of shed thoracic blood is carried out to reduce homologous transfusion after cardiac surgery, but it contains high concentrations of inflammatory mediators. The purpose of the study was to investigate whether retransfusion of shed thoracic blood induces plasma interleukin-6 (IL-6) expression and influences haemodynamics.

METHODS

Following uncomplicated coronary artery bypass graft surgery, forty-four patients were randomised in case postoperative blood loss via thoracic drains exceeded 350 ml. The course of plasma IL-6 levels and haemodynamics including cardiac output, extravascular lung water and intrathoracic blood volume were investigated prior to (T0), 30 minutes (T1), 1 (T2), 3 (T3) and 12 hours (T4) after retransfusion of 350 ml shed blood in comparison to 350 ml saline.

RESULTS

Plasma IL-6 levels at T1 (1892 +/- 202 vs. 485 +/- 30 pg/ml) and T2 (1059 +/- 119 vs. 413 +/- 30 pg/ml) were significantly higher in the verum group (n = 20) compared to controls (n = 24) ( P < 0.01). Severe haemodynamic side effects were not detected.

CONCLUSION

This study found significantly elevated plasma IL-6 levels following direct autologous retransfusion of shed thoracic blood but failed to show severe adverse effects affecting haemodynamic stability.

Concentrations of tramadol and O-desmethyltramadol enantiomers in different CYP2D6 genotypes

The influence of CYP2D6 genotype and CYP2D6 inhibitors on enantiomeric plasma levels of tramadol and O-desmethyltramadol as well as response to tramadol was investigated. One hundred and seventy-four patients received one hundred intravenous tramadol 3 mg/kg for postoperative analgesia. Blood samples drawn 30, 90, and 180 min after administration were analyzed for plasma concentrations of the enantiomers (+)-, (-)tramadol and (+)-, (-)O-desmethyltramadol by liquid chromatography-tandem mass spectrometry. Different CYP2D6 genotypes displaying zero (poor metabolizer (PM)), one (heterozygous individual (HZ)/intermediate metabolizer (IM)), two extensive metabolizer (EM), and three (ultra rapid metabolizer (UM)) active genes were compared. Concentrations of O-desmethyltramadol differed in the four genotype groups. Median (1/3 quartile) area under the concentration-time curves for (+)O-desmethyltramadol were 0 (0/11.4), 38.6 (15.9/75.3), 66.5 (17.1/118.4), and 149.7 (35.4/235.4) ng x h/ml for PMs, HZ/IMs, EMs, and UMs (P<0.001). Comedication with CYP2D6 inhibitors decreased (+) O-desmethyltramadol concentrations (P<0.01). In PMs, non-response rates to tramadol treatment increased fourfold compared with the other genotypes (P<0.001). In conclusion, CYP2D6 genotype determined concentrations of O-desmethyltramadol enantiomers and influenced efficacy of tramadol treatment.

Reduction in anaesthetic drug consumption is correlated with mean titrated intra-operative Bispectral Index values

BACKGROUND

Several studies have shown a reduction in anaesthetic drug consumption with Bispectral Index (BIS) titration compared with standard clinical practice. However, the amount of reduction varied widely between 1% and 40%. We investigated the correlation between reduction in anaesthetic drug consumption and mean titrated BIS values.

METHODS

An analysis upon randomized controlled trials cited until January 2006 in MEDLINE and other databases investigating the potential reduction in anaesthetic (hypnotic) drug consumption with BIS titration was performed. Investigations with a marked difference (> 15%) in opioid drug consumption between the BIS group and the standard practice group were excluded. Correlations between amount of reduction in hypnotic drug use and the mean titrated BIS value were analysed with linear regression.

RESULTS

Fourteen manuscripts covering 2582 patients were included into the analysis. The mean BIS value in the standard clinical practice group averaged over all studies was 43.6 +/- 3.2 and the mean BIS value in the BIS-titrated group was 49.9 +/- 5.4. The amount of reduction in hypnotic drug use correlated significantly with the mean BIS values in the BIS-titrated groups (r =0.68) and with the differences between the mean BIS value in the BIS-titrated group and the mean BIS value in the standard clinical practice group (r = 0.70). Every point of BIS difference between the two groups resulted in a reduced hypnotic drug use of approximately 2%.

CONCLUSION

Despite differences in the study designs and in the drugs used, a linear correlation between the mean titrated BIS value and the hypnotic drug saving potential was found.

Role of Toll-like receptor 4 for the pathogenesis of acute lung injury in Gram-negative sepsis

BACKGROUND AND OBJECTIVE

Proinflammatory cytokines as well as nitric oxide (NO) play a major role in mediating the response to lipopolysaccharide (LPS). The present study tested the hypothesis that LPS induces proinflammatory cytokines in the lung via the Toll-like receptor 4 (TLR4)/CD14 signalling cascade.

METHODS

Control mice and TLR4-deficient (TLR4-D) mice were used to test TLR4-mediated effects of LPS. Both strains received either Escherichia coli LPS (20 mg kg-1 intraperitoneal) or saline and their lungs were collected at different time points. Pulmonary nuclear factor kappaB (NFkappaB) activation was investigated with electromobility shift assay. mRNA expression of inflammatory mediators and their corresponding receptors were detected with Ribonuclease Protection Assay. Protein expression was detected by ELISA and western blotting. Inducible NO synthase (iNOS) expression was monitored by RT-PCR and iNOS activity by conversion of l-arginine to citrulline. Immune cells were sampled by bronchoalveolar lavage (BAL) and classified.

RESULTS

LPS application induced CD14-, but not TLR4 protein expression in control mice. Activation of pulmonary NFkappaB was observed within 60 min in control, but not in TLR4-D mice. Six hours of LPS administration induced a significant increase in pulmonary tumour necrosis factor alpha-, interleukin-1beta- and interleukin-6 mRNA and protein expression in control mice compared to TLR4-D mice. Furthermore, LPS induced a significantly higher increase of the iNOS expression and catalytic activity in control mice than in TLR4-D mice. BAL revealed an increase in total cell count in all LPS treated mice.

CONCLUSION

Our findings suggest that TLR4 plays a key role for regulating the expression of relevant cytokines within the lung during endotoxic shock.

Theophyllin bei Asystolie

We report the use of the non-specific adenosine antagonist theophylline (aminophylline) during a prolonged intraoperative cardiopulmonary resuscitation (CPR) due to myocardial infarction. In the 2005 guidelines of the European Resuscitation Council the general use of theophylline during CPR is not recommended, but in the case of an atropine and epinephrine resistant asystole, especially as a result of inferior myocardial infarction, theophylline might be a useful adjunct during CPR.

EEG spectral power and cognitive performance during sleep inertia: the effect of normal sleep duration and partial sleep deprivation

Sleep inertia (SI) is a transient period occurring immediately after awakening, usually characterized by performance decrement. When sleep is sufficient, SI is moderate, and produces few or no deficit. When it is associated with prior sleep deprivation, SI shows dose-dependent negative effects on cognitive performance, especially when subjects have been awaken in slow wave sleep (SWS). In the present study, spectral analysis was applied during the last 10 min before and the first 10 min after awakening, and during 1 h after awakening while subjects performed the Stroop test. Seventeen subjects were divided into a Control group who slept 8 h, and a Sleep Deprived group who slept only 2 h. The results show that performance was normal in the Control group, whereas reaction time was increased during the first half hour and error level during the second half hour in the Sleep Deprived group. Spectral analysis applied on the waking EEG during the whole test session showed that alpha activity was increased in both groups, but theta power only in the Sleep Deprived group. There was a high positive correlation in sleep deprived subjects between delta power during the last 10 min of sleep and subsequent performance decrement in speed and accuracy. Comparison of individual records showed a high positive correlation between spectral power before and after awakening in the Control group (generally in the sense of an increased frequency band), but no correlation was found in the Sleep Deprived group who exhibited a rather disorganized pattern. We discuss these results in terms of incoherence in the EEG continuity during sleep offset after prior sleep loss, which could partly account for the performance decrement observed during SI in sleep deprived subjects.

Akzidentelle urbane Unterkühlung

In emergency medicine accidental hypothermia (<35 degrees C) is a common epiphenomenon of many medical conditions. In contrast, severe hypothermia (<28 degrees C) occurs very seldom and presents a difficult medical situation. Here we present a female patient with severe urban hypothermia (core temperature of 20.7 degrees C) and circulatory arrest. An overview of the emergency treatment, rewarming strategy with extracorporeal circulation and the clinical course will be given. The survival of the patient and the favorable neurological outcome will be discussed considering the current literature. Due to the paucity of treatment guidelines or clear prognostic criteria of withholding or withdrawing treatment in severe hypothermia, the decision of prolonged resuscitation and rewarming strategy is solely dependent on the individual judgement and medical experience of the physician. The positive clinical outcome which can be gleaned from case reports or single retrospective studies should encourage the emergency physician to selectively rewarm a severe hypothermic patient with extracorporeal circulation under prolonged CPR.

Glove thermal insulation: local heat transfer measures and relevance

When exposed to cold, the hands need to be protected against heat loss not only in order to reduce thermal discomfort, but also to keep their efficiency. Although gloves are usually the most common protection, their thermal insulation is generally unknown. The aim of this study was to measure the heat losses from a gloved hand with a special interest in local variations. Using a calorimetric hand placed in a cold box, several types of gloves were tested. The results indicated that depending on the glove and on the area covered the heat loss reduction may vary from almost 60% to 90%. When the least efficient pair of gloves was excluded, heat exchange coefficients varied from 1.8 to 4.8 W/m2 per degrees C for the palm and from 4.2 to 6.2 W/m2 per degrees C for the back of the hand. The three medium fingers seemed to be equally treated, with a heat exchange coefficient variation of 6.3-9.0 W/m2 per degrees C. The thumb and the little finger, which require better insulation, exhibited higher local heat transfer coefficients of 8.3-12.7 W/m2 per degrees C. Some practical aspects are evoked.

Schmidt Syndrome Presenting as Acute Liver Failure

The Schmidt Syndrome (Type II Autoimmune-Syndrome) is characterised by an autoimmune adrenalitis in combination with a chronic lymphocellular thyreoiditis resulting in insufficiency of these organs in adulthood. Combination with diabetes is possible. The diagnosis is usually established by clinical examination and analysis of serum hormone levels (adrenocorticotropin hormone [ACTH], cortisol, thyroid stimulating hormone [TSH], triiodothyronine [fT3], thyroxine [fT4]). In the present case, initial diagnosis was rapid progressive liver failure of unknown origin with consecutive multiple organ dysfunction syndrome including dysfunction of heart, lungs, and kidneys. Frequent and less frequent causes of liver failure were ruled out, e.g. viral or autoimmune hepatitis, Budd-Chiari-syndrome, toxic, or drug induced liver failure. In retrospect, the multiple organ dysfunction syndrome was caused by hypoperfusion due to severe hypovolemia and hypoperfusion was induced by adrenocortical insufficiency proven by endocrinological testing. The clinical course of this case stresses the importance of the hormone balance in the critical ill patient. The guideline for treatment of patients with assumed hormonal dysregulation should include a full hormone status prior to substitution. The present case report also illustrates the importance of clinical signs and careful consideration of the medical history in detecting an autoimmune endocrine disease.

[Cytokines and heart failure]

Chronic heart failure is a major cause for mortality and morbidity in western civilizations. Previous hypothesises regarding the pathogenesis of chronic heart failure did not sufficiently explain the aetiology and the progression of the disease. However, it has been shown that a group of peptides called cytokines are expressed during chronic heart failure and that cytokines might play an important role for the pathogenesis. The expression of cytokines can be modulated from specific ACE-inhibitors as well as from different beta-blockers and angiotensin type 1 antagonists. Numerous investigations have shown that cytokines depress left ventricular function and can be responsible for different characteristics of chronic heart failure. The present article resumes experimental and clinical investigations and recent pharmacologic attempts for the treatment of chronic heart failure. The previous results demonstrate the importance to further investigate anti-inflammatory approaches to treat chronic heart failure.

Detection and differentiation of in vitro-spiked bacteria by real-time PCR and melting-curve analysis

We introduce a consensus real-time PCR protocol for the detection of bacterial DNA from laboratory-prepared specimens such as water, urine, and plasma. This prototype detection system enables an exact Gram stain classification and, in particular, screening for specific species of 17 intensive care unit-relevant bacteria by means of fluorescence hybridization probes and melting-curve analysis in a one-run experiment. One strain of every species was tested at a final density of 10(6) CFU/ml. All bacteria examined except Staphylococcus aureus and Staphylococcus epidermidis could be differentiated successfully; S. aureus and S. epidermidis could only be classified as "Staphylococcus species." The hands-on time for preparation of the DNA, performance of the PCR, and evaluation of the PCR results was less than 4 h. Nevertheless, this prototype detection system requires more clinical validation.

Piritramide and alfentanil display similar respiratory depressant potency

BACKGROUND

The question whether some opioids exert less respiratory depression than others has not been answered conclusively. We applied pharmacokinetic/pharmacodynamic (PKPD) modeling to obtain an estimate of the C50 for the depression of CO2 elimination as a measure of the respiratory depressant potency of alfentanil and piritramide, two opioids with vastly different pharmacokinetics and apparent respiratory depressant action.

METHODS

Twenty-three patients received either alfentanil (2.3 microg x kg(-1) x min-1, 14 patients, as published previously) or piritramide (17.9 microg x kg(-1) x min(-1), nine patients) until significant respiratory depression occurred. Opioid pharmacokinetics and the arterial PCO2 (PaCO2) were determined from frequent arterial blood samples. An indirect response model accounting for the respiratory stimulation due to increasing PaCO2 was used to describe the PaCO2 data.

RESULTS

The following pharmacodynamic parameters were estimated with NONMEM [population means and interindividual variability (CV)]: k(elCO2) (elimination rate constant of CO2) 0.144 (-) min(-1), F (gain of the CO2 response) 4.0 (fixed according to literature values) (28%), C50 (both drugs) 61.3 microg l-1 (41%), k(eo alfentanil) 0.654 (-) min(-1) and k(eo piritramide) 0.023 (-) min(-1). Assigning separate C50 values for alfentanil and piritramide did not improve the fit compared with a model with the same C50.

CONCLUSION

Since the C50 values did not differ, both drugs are equally potent respiratory depressants. The apparently lower respiratory depressant effect of piritramide when compared with alfentanil is caused by slower equilibration between the plasma and the effect site. Generalizing our results and based on simulations we conclude that slowly equilibrating opioids like piritramide are intrinsically safer with regard to respiratory depression than rapidly equilibrating opioids like alfentanil.

Effektivitäts- und Effizienzvergleich der Rettungsdienstsysteme in Birmingham (UK) und Bonn (D)

OBJECTIVE

Due to rising health care costs there is a need to verify that the treatment by Emergency Medical Services (EMS) systems is efficient and cost effective. The integration of emergency physicians is inherent part of out-of-hospital emergency care and regulated by law in Germany but not in England and the United States of America. Aim of this study therefore was to conduct a cost performance analysis by evaluating the underlying structure, the costs incurred and the achieved performance in two EMS systems with paramedics or emergency physicians on scene.

METHODS

The study was carried out in West-Birmingham, a part of the West-Midlands-Ambulance-Service (WMAS), and the EMS of Bonn. Pre defined questionnaires, EMS protocols, calculations of purchasing power parity and recent publications concerning out-of-hospital resuscitation (CPR) were used to evaluate the operating costs, to describe the structure and to measure the quality of performance. Significance was assumed at p < 0.01 for CHI(2)- or t-test, respectively.

RESULTS

Birmingham used state of the art technology for dispatch and logistics whereas Bonn trusted in high qualified personnel. In the 1st quarter 1997 the Mainz-Emergency-Evaluation Score could be achieved before (MEES A) and after preclinical treatment (MEES B) in 3502 and 3422 patients in Birmingham and Bonn, respectively. In Birmingham 7.5 % and in Bonn 17 % of all patients could be improved by the EMS treatment, respectively (p < 0.01). Looking at severely ill patients (MEES A < 22) the EMS in West-Birmingham achieved an improvement in 27.9 % of these patients with an averaged change in MEES of 0.9 +/- 1.7 points in all of them. In contrast the Bonn EMS improved the status in 47.8 % of these patients and MEES A could be improved considerably by 2.3 +/- 3.4 points (p < 0.01). Pharmacological treatment was less frequently used in Birmingham than in Bonn (12.9 % vs. 32.4 %, respectively; p < 0.01). At equal incidences of CPR attempts discharge rate after CPR was only 4 % in WMAS compared to 14.7 % in Bonn-North (p < 0.01). Per inhabitant and year total costs amounted to 10.43 euro for the EMS system in Birmingham, which is 42 % less than in Bonn. Unit hour utilisation reached 0.6 in Birmingham and only 0.33 in Bonn. In severely ill patients the improvement of MEES A by 0.1 points cost per inhabitant and year 1.16 euro in Birmingham and only 0.65 euro in Bonn. The survival of one patient after CPR was calculated to 0.7 euro in Birmingham and 0.17 euro in Bonn.

CONCLUSIONS

The provider of the EMS in West-Birmingham--WMAS--organised a reliable system with high efficiency concerning unit hour utilisation and response time reliability. In the EMS of Bonn, in contrast, the complex therapy by the emergency physicians improved MEES considerably and increased probability of survival after CPR at a higher level of efficiency. Further investigations however are necessary to evaluate the presented parameter of efficiency.

Improved Mental Rotation by Near-Sighted Subjects

Several studies have shown significant correlations among factors such as sex, age, and hormone levels with performance on mental rotation tasks. To perform spatial rotation also seems to be related to cognitive abilities such as musical skills. The present experiment investigated a possible relationship for enhanced spatial abilities, as observed in near-sighted subjects, with mental rotation performance. 39 near-sighted and 21 normal-sighted subjects were tested on a mental rotation task using two-dimensional representations of three-dimensional objects. Near-sighted subjects displayed fewer errors in possible rotations than normal-sighted subjects. There was no difference in errors between groups in identification of mirror images (“impossible rotations”). Results were interpreted in terms of a relation between enhanced reliance on nonvisual information by near-sighted subjects and improved spatial representation.

Interaction of age with time of day and mental load in different cognitive tasks

Extensive research has demonstrated that shiftwork produces deleterious effects on health because of the desynchrony it induces in the biological clock. The problem is even more crucial for older workers who present, in addition, various decrements in their cognitive functioning, particularly on attention and memory. The present study assessed whether age was related to task complexity as a function of time of day and time-on-task in a rapid rotating work-rest schedule. 24 subjects (12 juniors: 20-30 years and 12 seniors: 50-60 years) performed either a simple task (visual discrimination) or a complex task (descending subtraction) on three different moments of the day simulating the main shifts (morning, evening, and night). Analysis indicated that an age effect was only present on the more complex task, which was demanding in attentional resources and memory load. Seniors had no deficit in performance on the simple task compared to juniors. The effect of time of day was restricted to the simple task for both age groups. However, some differential strategies appear to distinguish juniors and seniors, specifically on accuracy during the night, suggesting that subjects of different ages cope with cognitive tasks in different ways and that perhaps some adverse effects apparently associated with aging could be counteracted by efficient strategies, but not others.

A case study in designing speech interaction with a patient monitor

OBJECTIVE

New developments in speech interaction technology warrant the assumption that some of the interaction problems at anesthesia workplaces can be solved using speech interaction. One application might be the documentation of the anesthetic procedure.

METHOD

To investigate this hypothesis, a speech input system was developed for a commercially available patient monitor (Datex-Ohmeda AS/3 Anesthesia Monitor with Record-Keeper), which in addition to standard functions also facilitates the generation of the anesthesia record. The speech input system was based on the IBM ViaVoice speech recognition technology (version Millennium Pro). The speech input device was preliminarily tested by 5 anesthetists wearing surgical masks under laboratory conditions and through retrospectively documenting 4 to 5 anesthetic procedures (each 12 to 17 documentation entries) in a calm situation. The speech interactive documentation procedure was compared with the conventional keyboard documentation procedure.

RESULTS

The test persons achieved an overall word recognition rate between 72% and 92.4%. Between 76.5% and 97.7% of the single word commands could be completed without any corrections. The same qualifier held for 58.5% to 86.3% of the two- and three-word commands. Despite high speech recognition error rates, almost all documentation entries (236 of 238) could be finished using speech interaction. Comparing both documentation techniques, speech interaction was said to be more intuitive and caused less frustration than the keyboard documentation procedure. However, speech interactive documentation was rated less controllable because of the high speech recognition error rates and bccause the auditive feedback dialogues took too long.

CONCLUSIONS

Modern speech recognition tools are still not advanced enough to facilitate the design of applications with an almost natural speech interface and widespread user acceptance. Nevertheless, many tasks in anesthesia have the necessary characteristics to be optimally supported by speech interaction. In contrast to earlier approaches to speech-interactive anesthesia workplaces, successful application today depends on the question of design rather than solely on that of technology. Many of the constraints and drawbacks of current technology can be overcome through appropriate design measures. The goals must focus first on identifying task areas in intensive care where speech-interaction can yield real benefit in terms of work efficiency, and second on developing and evaluating an ergonomic design of speech interaction. The intended users seem to look forward to the incorporation of speech interaction at the workplace.

Evaluation of two new ecological interface approaches for the anesthesia workplace

OBJECTIVE

Currently, vital parameters are commonly displayed as trends along a timeline. However, clinical decisions are more often based upon concepts, such as the depth of anesthesia, that are derived by combining parameter relationships and additional context information. The current displays do not visualize such concepts and therefore do not optimally support the decision process. A new display should present an ecological interface (EI). The principle of EI design is to visualize all of the information necessary for decision making in one single display.

METHODS

In the first approach, we developed an EI that visualizes 35 relevant parameters for anesthesia monitoring. All of the parameters are generated by an anesthesia software simulator. Sixteen anesthetists had to administer two simulated general anesthetics: in one setting working only with the simulator's monitors ("Sim Only"), and in another setting working with the simulator's monitors in combination with the EI ("Combi1"). During each experiment, one unexpected critical incident (either blood loss or a cuff leakage) had to be identified. The control and monitoring behavior was analyzed by recording the subjects' eye movements and think-aloud protocol. With the help of the eye-tracking results, we re-designed the EI. The new EI was then tested with no eye tracking ("Combi2") on eight anesthetists under analogous conditions as in "Combi1."

RESULTS

Cuff leakage was identified significantly quicker in "Combi1" (7 of 8 cases; time (T): 65 s +/- 73 s) than in "SimOnly" (6 of 8 cases; T: 222 s +/- 187 s). Blood loss was identified in 5 of 8 cases (T: 215 s +/- 76 s) in "Combi1" as quickly as in "SimOnly" (all cases; T: 217 s +/- 72 s). In "Combi1," the EI was used as the main source of information (in 43 +/- 19% of time) and was frequently favored when identifying an evolving critical incident. In "Combi2," cuff leakage was identified in 7 of 8 cases (T: 70 s +/- 111 s) as quickly as in "Combi1." Blood loss was identified significantly quicker in all cases (T: 147 s +/- 62 s) in "Combi2" than in "Combi1" and in "SimOnly."

CONCLUSION

The results have shown that appropriately designed EIs may improve the anesthetist's decision making and focus attention on specific problems. Now, the findings have to be tested in future studies by widening the scope using other simulated scenarios and being closer to reality under real conditions in the OR. Eye tracking proved to be a useful method to analyze the anesthetists' decision making and appropriately re-design interfaces.

Opioid-induced respiratory depression is associated with increased tidal volume variability

BACKGROUND AND OBJECTIVE

mu-agonistic opioids cause concentration-dependent hypoventilation and increased irregularity of breathing. The aim was to quantify opioid-induced irregularity of breathing and to investigate its time-course during and after an opioid infusion, and its ability to predict the severity of respiratory depression.

METHODS

Twenty-three patients breathing spontaneously via a continuous positive airway pressure (CPAP) mask received an intravenous (i.v.) infusion of alfentanil (2.3 microg kg(-1) min(-1), 14 patients) or pirinitramide (piritramide) (17.9 microg kg(-1) min(-1), nine patients) until either a cumulative dose of 70 microg kg(-1) for alfentanil or 500 microg kg(-1) for pirinitramide had been achieved or the infusion had to be stopped for safety reasons. Tidal volumes (VT) and minute ventilation were measured with an anaesthesia workstation. For every 20 breaths, the quartile coefficient was calculated (Qeff20V(T)).

RESULTS

Both the decrease of minute volume and the increase of Qeff20V(T) during and after opioid infusion were highly significant (P < 0.001, ANOVA). Patients in which the alfentanil infusion had to be terminated prematurely had lower minute volumes (P = 0.002, t-test) and higher Qeff20V(T) (P = 0.034, t-test) than those who received the complete dose. Changes in the regularity of breathing measured as Qeff20V(T) parallel those of minute ventilation during and after opioid infusion.

CONCLUSIONS

Opioids cause a more complicated disturbance of the control of respiration than a mere resetting to higher PCO2. Furthermore, Qeff20V(T) appears to predict the severity of opioid-induced respiratory depression.

Differential expression of alpha- and beta-defensins in human peripheral blood

BACKGROUND

Human defensin peptides with broad-spectrum antimicrobial activity have been implicated in the human defence response towards microbial invasion. Two families of defensins designated alpha- and beta-defensins, respectively, have been identified. Little is known about the expression of both defensin families in human peripheral blood. The purpose of this study was to examine the expression of alpha- and beta-defensin genes in human peripheral blood.

MATERIAL AND METHODS

Fifty-one healthy blood donors were screened for defensin expression. Blood from defensin responders was stimulated by lipopolysaccharide or heat-inactivated Pseudomonas aeruginosa ex vivo. Levels of mRNA were assessed by semiquantitative RT-PCR. Southern blot analysis and sequencing were used to confirm the identity of defensin gene transcripts. Western blotting analysis was used to detect the expression of defensin peptides.

RESULTS

beta-defensin was undetected in human peripheral blood without stimulation. Following stimulation by lipopolysaccharide or heat-inactivated bacterial cells, the majority (88.2%) of healthy individuals had a detectable expression for beta-defensin-1 gene and 39.2% for beta-defensin-2 gene, compared with none for beta-defensin-3. beta-defensin-1 and -2 mRNAs in the stimulated human peripheral blood of responders became detectable at 3 h and showed a maximum at 6 h following induction by 100 ng mL-1 of lipopolysaccharide or bacterial cells. In contrast, human alpha-defensins 1-3 mRNA are constitutively expressed in peripheral leukocytes but not up-regulated by lipopolysaccharide or bacterial cells.

CONCLUSIONS

In human peripheral blood, beta-defensin-1 and -2 genes were transiently transcribed and translated following the induction of lipopolysaccharide or heat-inactivated bacterial cells, whereas alpha-defensins 1-3 genes were constitutively transcribed, and beta-defensin-3 gene was not expressed. The inducible expression of beta-defensin-1 and -2 genes showed interindividual variability.

Application of semilinear canonical correlation to the measurement of the electroencephalographic effects of volatile anaesthetics

BACKGROUND AND OBJECTIVE

The common parameters of the electroencephalogram quantify a shift of its power spectrum towards lower frequencies with increasing anaesthetic drug concentrations (e.g. spectral-edge frequency 95). These ad hoc parameters are not optimized for the content of information with regard to drug effect. Using semilinear canonical correlation, different frequency ranges (bins) of the power spectrum can be weighted for sensitivity to changes of drug concentration by multiplying their power with iteratively determined coefficients, yielding a new (canonical univariate) electroencephalographic parameter.

METHODS

Electroencephalographic data obtained during application of volatile anaesthetics were used: isoflurane (n = 6), desflurane (7), sevoflurane (7), desflurane during surgical stimulation (12). Volatile anaesthetic end-tidal concentrations varied between 0.5 and 1.6 minimum alveolar concentration (MAC). The canonical univariate parameter and spectral-edge frequency 95 were determined and their correlation with the volatile anaesthetic effect compartment concentration, obtained by simultaneous pharmacokinetic-pharmacodynamic modelling, were compared.

RESULTS

The canonical univariate parameter with individually optimized coefficients, but not with mean coefficients, was superior to the spectral-edge frequency 95 as a measure of anaesthetic drug effect. No significant differences of the coefficients were found between the three volatile anaesthetics or between the data with or without surgical stimulus. The coefficients for volatile anaesthetics were similar to the coefficients for opioids, but different from coefficients for propofol and midazolam.

CONCLUSIONS

The canonical univariate parameter calculated with individually optimized coefficients, but not with mean coefficients, correlates more accurately and consistently with the effect site concentrations of volatile anaesthetics than with spectral-edge frequency 95.