Adverse physiological events under anaesthesia and sedation: a pilot audit of electronic patient records

Review of perioperative activity including adverse events, throughput and compliance with 'best practice', can theoretically be used to optimise healthcare delivery. Computer-based analysis of electronic patient records could provide a practical means to manage quality improvement. This pilot study examined the effectiveness of such a system in practice. All intraoperative patient notes and physiological data were collected over 17 months in a rural hospital using data from an electronic record-keeping system. Algorithms were developed to automatically identify potential adverse events based on physiological measures. Each computer-identified event was reviewed by a panel of three anaesthetists and assessed for validity, severity and probable cause. Two areas were identified to pilot quality improvement activities-sedation for colonoscopies and inhalational anaesthesia with desflurane. Specific 'in-house' guidelines were created for these procedures and feedback on the patterns of adverse events were provided to anaesthetic staff A total of 138 separate adverse events were identified for all operative cases over 17 months, with an overall adverse event incidence of 3.3%. The adverse event incidence during colonoscopy and laryngospasm/hypoxia during desflurane anaesthesia was 6.3% and 1.3% respectively. This decreased to 2.8% (P <0.005) and 0.13% (P <0.0001) respectively for the nine months following feedback and the introduction of guidelines. Anaesthesia information systems can be an effective quality improvement tool and may enhance existing tools such as incident reporting systems.

Comparison of the analgesic effects of xylazine in sheep via three different administration routes

OBJECTIVE

To examine the influence of administration route on the analgesic effects of identical doses of xylazine in sheep. A prospective, linear, randomised laboratory study.

PROCEDURE

The analgesic response to the administration of 2.5 mg of the alpha2 agonist xylazine either intravenously, intramuscularly or subcutaneously was assessed using an analgesia testing method based upon a learned response to a painful electrical stimulus.

RESULTS

Intravenous administration achieved the most rapid onset and highest peak analgesic values of all administration methods, but was characterised by a shorter duration of action (25 min). Intramuscular and subcutaneous administration resulted in a longer duration of action (40 min) and a greater total analgesic response.

CONCLUSION

For the routine management of acute pain, intramuscular administration provided the best combination of onset, duration and total analgesic response of the routes examined. The absence of adverse side effects, such as sedation, normally associated with the administration of alpha2 agonists should also encourage the use of this method as a simple and effective means of providing significant analgesia in the sheep.

Magnetic resonance imaging of abdominal adiposity in a large cohort of British children

OBJECTIVE

To describe abdominal adipose tissue distribution in a large sample of contemporary British children; to determine the influence of gender, stage of maturation and body mass index (BMI) on abdominal adipose tissue distribution; and to compare the ability of BMI and waist circumference to predict abdominal adipose tissue.

SUBJECTS AND METHODS

A total of 74 boys (mean age 13.4+/-0.4 years) and 96 girls (mean age 13.5+/-0.5 years) were selected from volunteer children enrolled in the Avon Longitudinal Study of Parents and Children (ALSPAC). Height, weight and waist circumference were measured and BMI calculated. Stage of sexual maturation was available for 113 children using a self-report questionnaire based on Tanner's criteria. Magnetic resonance imaging was used to assess subcutaneous abdominal adipose tissue (SAAT) and intra-abdominal adipose tissue (IAAT) volumes and patterning.

RESULTS

Boys had lower levels of IAAT (P=0.036) and SAAT (P=0.003) than girls. IAAT and SAAT were higher in overweight and obese boys and girls when compared with normal weight children (P<0.0001). This pattern was also reflected in waist circumference groups. Boys had higher IAAT/SAAT ratios than girls, indicating proportionately more adipose tissue deposited intra-abdominally (P=0.002). However, both boys and girls deposited less than 10% of their abdominal fat as internal adipose tissue. WC predicted 67.4% of the variance in IAAT (P<0.001), and BMI predicted 84.8% of the variance in SAAT (P<0.001). However, BMI as the best single predictor explained only 8.4% of the variance in the IAAT/SAAT ratio (P<0.001).

CONCLUSIONS

At this age and stage of sexual maturation, the amount of IAAT remains relatively small. WC and BMI offer a feasible alternative to the MRI estimation of IAAT and SAAT, respectively, in a population-based sample of boys and girls. International Journal of Obesity (2008) 32, 91-99; doi:10.1038/sj.ijo.0803780; published online 27 November 2007.

Axiality of loading in the tensile test

Axiality of loading is very important in the tensile test, particularly under creep conditions. An experimental evaluation of bending of the test section using resistance strain gauges has been devised. This test showed that excessive bending was present in spite of the adoption of a coupling design recommended in the literature. The cause of bending was found to be solely due to a friction moment exerted by the pin joints which formed the essential feature of the couplings. A crossed knife-edge design was substituted for them with satisfactory results. Analysis of the pin joint showed it to be unsuitable for specimen alignment in the tensile test.

Blood-brain distribution of morphine-6-glucuronide in sheep

BACKGROUND AND PURPOSE

At present there are few data regarding the rate and extent of brain-blood partitioning of the opioid active metabolite of morphine, morphine-6-glucuronide (M6G). In this study the cerebral kinetics of M6G were determined, after a short-term intravenous infusion, in chronically instrumented conscious sheep.

EXPERIMENTAL APPROACH

Five sheep received an intravenous infusion of M6G 2.2 mg kg(-1) over a four-minute period. Non-linear mixed-effects analysis, with hybrid physiologically based kinetic models, was used to estimate cerebral kinetics from the arterio-sagittal sinus concentration gradients and cerebral blood flow measurements.

KEY RESULTS

A membrane limited model was selected as the final model. The blood-brain equilibration of M6G was relatively slow (time to reach 50% equilibration of the deep compartment 5.8 min), with low membrane permeability (PS, population mean, 2.5 ml min(-1)) from the initial compartment (V1, 13.7 ml) to a small deep distribution volume (V2) of 18.4 ml. There was some between-animal variability (%CV) in the initial distribution volume (29%), but this was not identified for PS or V2.

CONCLUSION AND IMPLICATIONS

Pharmacokinetic modelling of M6G showed a delayed equilibration between brain and blood of a nature that is primarily limited by permeability across the blood-brain-barrier, in accordance with its physico-chemical properties.

Measurement of maximal muscle cross-sectional area of the elbow extensors and flexors in children, teenagers and adults

The aims of this study were to examine age and sex differences in elbow extensor and flexor anatomical muscle cross-sectional area (mCSA) measured by magnetic resonance imaging (MRI) and the location of maximal mCSA as a percentage of the distance from the distal to the proximal end of the humerus. Ninety-five individuals spread across the age groups 9 - 10 years, 16 - 17 years and ?21 years participated in the study. Muscle cross-sectional area derived from the manual MRI tracing proved to be highly reliable in terms of limits of agreement (-2.5 to 1.5 cm(2)) and the intraclass correlation coefficient (ICC = 0.998). A sex-by-age group analysis of variance revealed significant effects (P < 0.01) of sex, group and a sex-by-group interaction, the latter reflecting a greater increase in males than females of upper arm mCSA from childhood to adulthood. Extensor mCSA was more proximal (55 +/- 6%) than that of the flexors (28 +/- 6%). A significant effect (P < 0.01) of group was found for location of maximal extensor mCSA, reflecting its more distal position with increasing age. Measurements of muscle size should be made at the individually determined position of maximal mCSA if interpreting data collected during growth and maturation, especially if the muscle group of interest is the elbow extensors and if different age groups are being monitored.

Cerebral cortical effects of desflurane in sheep: comparison with isoflurane, sevoflurane and enflurane

BACKGROUND

Different volatile anesthetic agents have differing propensities for inducing seizures. A measure of the predilection to develop seizures is the presence of interictal spike discharges (spikes) on the electrocorticogram (ECoG). In this study, we investigated the propensity of desflurane to induce cortical spikes and made a direct objective comparison with enflurane, isoflurane, and sevoflurane. The ECoG effects of desflurane have not been previously reported.

METHODS

After establishment of invasive monitoring and a parasagittal array of eight electrodes to record the ECoG; eight adult merino sheep were given a series of short inhalational anesthetics (using desflurane, enflurane, sevoflurane and isoflurane); each titrated to ECoG burst suppression. Anesthetic effect was estimated by the effects on the approximate entropy of the ECoG. The effect of anesthetic on the spike-rate in the ECoG was analyzed using a non-linear mixed-effect method with a sigmoid Emax model.

RESULTS

A similar 'depth of anesthesia' was achieved for each agent, as estimated by the approximate entropy. The mean (SD) values of Emax for the spike-rate vs. approximate entropy relationship were desflurane 0.5 (0.9), enflurane 17.2 (4.0), isoflurane 0.7 (1.2), and sevoflurane 5.3 (1.2) spikes/min. The spike rate caused by desflurane was similar to isoflurane and significantly lower than that of enflurane (P < 0.001), and sevoflurane (P = 0.009).

CONCLUSION

Desflurane induces minimal cerebral cortical spike activity when administered to burst suppression, consistent with its low propensity for inducing seizures in non-epileptic brains. The agents can be ranked by their relative ability to cause spike activity: enflurane >> sevoflurane > isoflurane = desflurane.

The Evolutionary State Equation of Creep

The state equation of creep deformation is generalized, and evolutionary internal state variables are introduced. These concepts are then used to rationalize several creep theories currently in use. Finally, a simple recovery model of creep deformation is proposed within the framework of the general evolutionary theory. The model exhibits several important characteristics of creep in metals and also illustrates some important features of the theory.

Randomized, double-blind comparison of growth in infants receiving goat milk formula versus cow milk infant formula

OBJECTIVE

To compare growth of infants fed goat milk infant formula (GMF) or cow milk infant formula (CMF) and to compare tolerability and safety of the two formulas.

METHODS

The study was conducted in Auckland, New Zealand. This was a double-blind randomized controlled trial. Newborn term infants were randomized within 72 h of birth to GMF or CMF. Milk formula powder in single serve sachets were reconstituted and fed to infants from trial commencement until age 168 days. No other formula given from randomization until age 168 days. Infant weight, length and head circumference were measured at birth and age 14, 28, 56, 84, 112, 140 and 168 days. Bowel motion frequency and consistency, sleeping and crying patterns and adverse events were also measured.

RESULTS

Seventy-two infants were randomized, 36 each to GMF or CMF, with 62 infants completing the intervention. At enrollment the average weight of infants in the GMF group (mean +/- SD) was 3.33 +/- 0.43 kg and in the CMF group 3.43 +/- 0.47 kg; and at study completion 8.07 +/- 0.90 kg (GMF) and 7.87 +/- 0.99 kg (CMF). The difference in average weight gain over the study period for the GMF group versus the CMF group was not significant (+309 g; 95% CI = -49 to +668, P = 0.09). Median daily bowel motion frequency was greater in the GMF group than the CMF group (2.4 vs 1.7, P = 0.01). There were no group differences in bowel motion consistency, duration of crying, ease of settling, or frequency of adverse events.

CONCLUSION

Growth of infants fed GMF is not different to that of infants-fed CMF.

Countercurrent compartmental models describe hind limb skeletal muscle helium kinetics at resting and low blood flows in sheep

AIMS

This study evaluated the relative importance of perfusion and diffusion mechanisms in compartmental models of blood : tissue helium exchange in a predominantly skeletal muscle tissue bed in the sheep hind limb. Helium has different physiochemical properties from previously studied gases and is a common diluent gas in underwater diving where decompression schedules are based on theoretical models of inert gas kinetics.

METHODS

Helium kinetics across skeletal muscle were determined during and after 20 min of helium inhalation, at separate resting and low steady-states of femoral vein blood flow in six sheep under isoflurane anaesthesia. Helium concentrations in arterial and femoral vein blood were determined using gas chromatographic analysis and femoral vein blood flow was monitored continuously. Parameters and model selection criteria of various perfusion-limited or perfusion-diffusion compartmental models of skeletal muscle were estimated by simultaneous fitting of the models to the femoral vein helium concentrations for both blood flow states.

RESULTS

A model comprising two parallel perfusion-limited compartment models fitted the data well but required a 51-fold difference in relative compartment perfusion that did not seem physiologically plausible. Models that allowed a countercurrent diffusion exchange of helium between arterial and venous vessels outside of the tissue compartments provided better overall fit of the data and credible parameter estimates.

CONCLUSIONS

These results suggest a role of arterial-venous diffusion in blood : tissue helium equilibration in skeletal muscle.

The prognostic significance of p53, p27 kip1, p21 waf1, HER-2/neu, and Ki67 proteins expression in gastric cancer: a clinicopathological and immunohistochemical study of 121 Arab patients

BACKGROUND

The variability of prognosis within a pathological stage of gastric cancer (GC) at presentation, underscores the need for specific biological markers to identify subgroups of patients with aggressive course for intensive treatment. To our knowledge, this is the first study from an Arab population reporting on the relationship of p53, p27 kip1, p21 waf1, HER-2/neu, and Ki67 expression, and clinicopathological features and their prognostic significance.

METHODS

Formalin-fixed paraffin-embedded tumors were studied by immunohistochemistry, using monoclonal antibodies to p53, p27 kip1, p21 waf1, HER-2/neu, and Ki67. The results were correlated with clinicopathological features and survival.

RESULTS

M:F = 80:41; median age = 60 years; stage III and IV = 71%; and median follow-up = 34.4 months. Positive expression rates of p53, p27 kip1, p21 waf1, Ki67, and HER-2/neu were 54%, 40%, 8.3%, 70%, and 12% respectively. p53 expression correlated with age <60 years (P = 0.03), tumor size >5 cm (P = 0.01), p27 kip1 and Ki67 expression (P = 0.0001), and HER-2/neu (P = 0.04). p21 waf1 correlated inversely with T-stage (P = 0.008) and Her-2/neu expression correlated with histological grade (P = 0.04) and T-stage (P = 0.008). Univariate analysis showed that p53 overexpression (P = 0.01), fungating and infiltrative macroscopic appearance (P = 0.02), size >5 cm (P = 0.0001), lymph node metastasis (P = 0.0001), p T3 and T4 disease (P = 0.01), and overall stage III and IV (P = 0.0001) disease were adverse prognostic factors. Patients with tumor profiles p53 (-)/p27 (+) had better survival than those with p53 (+)/p27 kip1 (-)(P = 0.02). On multivariate analysis by Cox regression model, the expression of p53 (P = 0.03) and lymph node involvement (P = 0.01) were significant adverse prognostic factors for overall survival.

CONCLUSIONS

The expression of p53 in Arab patients with GC correlates with aggressive tumor characteristics and is an independent prognostic factor. The combined analysis of p53 and p27 kip1 is of added prognostic value.

Association of the dopamine transporter (DAT1) 10/10-repeat genotype with ADHD symptoms and response inhibition in a general population sample

Association between attention-deficit hyperactivity disorder (ADHD) and the 10-repeat allele of the dopamine transporter gene (DAT1) has been reported in independent clinical samples using a categorical clinical definition of ADHD. The present study adopts a quantitative trait loci (QTL) approach to examine the association between DAT1 and a continuous measure of ADHD behaviours in a general-population sample, as well as to explore whether there is an independent association between DAT1 and performance on neuropsychological tests of attention, response inhibition, and working memory. From an epidemiological sample of 872 boys aged 6-11 years, we recruited 58 boys scoring above the 90th percentile for teacher reported ADHD symptoms (SWAN ADHD scale) and 68 boys scoring below 10th percentile for genotyping and neuropsychological testing. A significant association was found between the DAT1 homozygous 10/10-repeat genotype and high-scoring boys (chi(2)square=4.6, P<0.03; odds ratio=2.4, 95% CI 1.1-5.0). Using hierarchical linear regression, a significant independent association was found between the DAT1 10/10-repeat genotype and measures of selective attention and response inhibition after adjusting for age, IQ, and ADHD symptoms. There was no association between DAT1 and any component of working memory. Furthermore, performance on tasks of selective attention although associated with DAT1 was not associated with SWAN ADHD high scores after controlling for age and IQ. In contrast, impairment on tasks that tapped sustained attention and the central executive component of working memory were found in high-scoring boys after adjusting for age and IQ. The results suggest that DAT1 is a QTL for continuously distributed ADHD behaviours in the general population and the cognitive endophenotype of response inhibition.

Theory of mind deficits in children with fragile X syndrome

BACKGROUND

Given the consistent findings of theory of mind deficits in children with autism, it would be extremely beneficial to examine the profile of theory of mind abilities in other clinical groups such as fragile X syndrome (FXS) and Down syndrome (DS). Aim The aim of the present study was to assess whether boys with FXS are impaired in simple social situations that require them to understand their own and others' mental states - in essence: do they have a 'theory of mind'?

METHOD

Well-standardized tasks of theory of mind, the location change false belief task and the appearance-reality tasks were employed to examine whether any impairment might be specific to the FXS or part of a more generalized developmental deficit.

RESULTS

The results suggest that children with FXS do have impairment in theory of mind that is comparable to the deficit reported in other groups with learning disabilities such as DS. However, closer inspection of the impairment between these groups revealed qualitative differences in error types (realist vs. phenomenist), suggestive of atypical development that goes beyond general cognitive delay.

CONCLUSION

The findings are discussed in terms of the teasing apart of different components of social cognition in order to identify syndrome-specific deficiencies and proficiencies.

Cortical entropy changes with general anaesthesia: theory and experiment

Commonly used general anaesthetics cause a decrease in the spectral entropy of the electroencephalogram as the patient transits from the conscious to the unconscious state. Although the spectral entropy is a configurational entropy, it is plausible that the spectral entropy may be acting as a reliable indicator of real changes in cortical neuronal interactions. Using a mean field theory, the activity of the cerebral cortex may be modelled as fluctuations in mean soma potential around equilibrium states. In the adiabatic limit, the stochastic differential equations take the form of an Ornstein-Uhlenbeck process. It can be shown that spectral entropy is a logarithmic measure of the rate of synaptic interaction. This model predicts that the spectral entropy should decrease abruptly from values approximately 1.0 to values of approximately 0.7 as the patient becomes unconscious during induction of general anaesthesia, and then not decrease significantly on further deepening of anaesthesia. These predictions were compared with experimental results in which electrocorticograms and brain concentrations of propofol were recorded in seven sheep during induction of anaesthesia with intravenous propofol. The observed changes in spectral entropy agreed with the theoretical predictions. We conclude that spectral entropy may be a sensitive monitor of the consciousness-unconsciousness transition, rather than a progressive indicator of anaesthetic drug effect.

Recirculatory model of fentanyl disposition with the brain as the target organ

BACKGROUND

The factors affecting the concentrations of fentanyl in the brain after intravenous administration have not been completely quantified.

METHODS

A model integrating the role of brain, lung and systemic kinetics was developed based on data from conscious instrumented sheep. Brain kinetics were inferred from arterio-sagittal sinus concentration gradients and cerebral blood flow, and lung kinetics from the pulmonary artery-aortic gradient and cardiac output. The best models of the lung and brain were incorporated into a recirculatory model of the whole-body disposition of fentanyl. The validity of the model structure was tested by its ability to describe published data on the effect of hypo-, normo- and hypercarbia on the blood and brain concentrations of fentanyl in anaesthetized dogs.

RESULTS

The cerebral kinetics of fentanyl were consistent with partial membrane limitation: the time to 50% equilibration with arterial blood was 10.0 min. Lung kinetics had two distinct components: a shallow compartment that was 50% equilibrated with blood in 0.72 min, and a loss term probably representing sequestration. Despite its simplicity, the recirculatory model was an adequate description of the sheep data. The dog data could be described if cerebral blood flow and cardiac output in the model were allowed to differ between hypo-, normo- and hypercarbic states. The required flow changes were in good agreement with the known effect of these states in the dog.

CONCLUSIONS

A recirculatory model with the brain as a target organ defined the quantitative relationship between the brain concentrations of fentanyl and the circulatory state.

The outcome of treatment of breast cancer in a developing country--Oman

The aim of the present study was to evaluate the outcome of treatment of breast cancer in Oman with an analysis of clinico-pathological features, treatment modalities utilized, and prognostic factors. One hundred fifty-two breast cancer patients diagnosed between January 1996 and June 2002 were evaluated retrospectively. Their mean age was 48.5 (S.D. +/- 10.8) years, and 48% of the female patients were premenopausal. The mean tumor size according to pathology was 4.6 (S.D. 3.29)cm, and 34.9% and 15.8% of patients had stage III or IV disease, respectively. Only 26.3% of the patients had breast-conserving surgery, and neoadjuvant chemotherapy was underutilized. The overall 5-year relapse-free survival (RFS) and overall (OS) survival rates were 62% and 64%, respectively. On multivariate analysis, axillary lymph node involvement and tumor differentiation were predictive of RFS and OS, respectively. Thus, breast cancer patients in Oman present with advanced stages of the disease at younger ages than their counterparts in the West and have lower survival rates. Increasing awareness and the introduction of screening programs and of a multidisciplinary approach are essential in Oman and other developing countries to improve the outcome of treatment.