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Biomedical subjects

R W Morris

Publications and source records attributed to R W Morris.

At least 19 recordsLinked to original sources
PubMed2007

Power calculations for likelihood ratio tests for offspring genotype risks, maternal effects, and parent-of-origin (POO) effects in the presence of missing parental genotypes when unaffected siblings are available.

Genotype-based likelihood-ratio tests (LRT) of association that examine maternal and parent-of-origin effects have been previously developed in the framework of log-linear and conditional logistic regression models. In the situation where parental genotypes are missing, the expectation-maximization (EM) algorithm has been incorporated in the log-linear approach to allow incomplete triads to contribute to the LRT. We present an extension to this model which we call the Combined_LRT that incorporates additional information from the genotypes of unaffected siblings to improve assignment of incompletely typed families to mating type categories, thereby improving inference of missing parental data. Using simulations involving a realistic array of family structures, we demonstrate the validity of the Combined_LRT under the null hypothesis of no association and provide power comparisons under varying levels of missing data and using sibling genotype data. We demonstrate the improved power of the Combined_LRT compared with the family-based association test (FBAT), another widely used association test. Lastly, we apply the Combined_LRT to a candidate gene analysis in Autism families, some of which have missing parental genotypes. We conclude that the proposed log-linear model will be an important tool for future candidate gene studies, for many complex diseases where unaffected siblings can often be ascertained and where epigenetic factors such as imprinting may play a role in disease etiology.

Algorithms↗
PubMed2007

Preoperative chemotherapy and the outcome of liver resection for colorectal metastases.

BACKGROUND: Neoadjuvant systemic chemotherapy is being increasingly used prior to liver resection for colorectal metastases. Oxaliplatin has been implicated in causing structural changes to the liver parenchyma, and such changes may increase the morbidity and mortality of surgery. PATIENTS AND METHODS: A retrospective study was undertaken of 101 consecutive patients who had undergone liver resection for colorectal metastases in two HPB centers. Preoperative demographic and premorbid data were gathered along with liver function tests and tumor markers. A subjective assessment of the surgical procedure was noted, and in-hospital morbidity and mortality were calculated. The effect of preoperative chemotherapy on short-term and long-term outcome was analyzed, and actuarial 1 and 3 year survival was determined. RESULTS: Patients who received neoadjuvant chemotherapy had a higher number of metastases (median 2, range 1-8 versus median 1, range 1-5; P = 0.019) and more had synchronous tumors (24 patients versus 8; P < 0.001). Overall morbidity was 37% and hospital mortality was 3.9%. Operative and in-hospital outcome was not influenced by chemotherapy. Long-term survival was worse in patients who had received preoperative chemotherapy (actuarial 3-year survival 62% versus 80%; P = 0.04). CONCLUSIONS: This study shows no evidence that neoadjuvant chemotherapy, and in particular oxaliplatin, increases the risk associated with liver resection for colorectal metastases. Long-term outcome is reduced in patients receiving preoperative chemotherapy, although they have more advanced disease.

Adult↗
PubMed2006

Knee versus thigh length graduated compression stockings for prevention of deep venous thrombosis: a systematic review.

OBJECTIVE: Graduated compression stockings are a valuable means of thrombo-prophylaxis but it is unclear whether knee-length (KL) or thigh length (TL) stockings are more effective. The aim of this review was to systematically analyse randomised controlled trials that have evaluated stocking length and efficacy of thromboprophylaxis. METHOD: A systematic review of the literature was undertaken. Clinical trials on hospitalised populations and passengers on long haul flights were selected according to specific criteria and analysed to generate summated data. RESULTS: 14 randomized control trials were analysed. Thirty six of 1568 (2.3%) participants randomised to KL stockings developed a deep venous thrombosis, compared with 79 of 1696 (5%) in the TL control/thigh length group. Substantial heterogeneity was observed amongst trials. KL stockings had a significant effect to reduce the incidence of DVT in long haul flight passengers, odds ration 0.08 (95%CI 0.03-0.22). In hospitalised patients KL stockings did not appear to be far worse than TL stockings, odds ratio 1.01 (95%CI 0.35-2.90). For combined passengers and patients, there was a benefit in favour of KL stockings, weighted odds ratio 0.45 (95% CI 0.30-0.68). CONCLUSION: KL graduated stockings can be as effective as TL stockings for the prevention of DVT, whilst offering advantages in terms of patient compliance and cost.

Aircraft↗
PubMed2006

Inflammatory gene polymorphisms and risk of postoperative myocardial infarction after cardiac surgery.

BACKGROUND: The inflammatory response triggered by cardiac surgery with cardiopulmonary bypass (CPB) is a primary mechanism in the pathogenesis of postoperative myocardial infarction (PMI), a multifactorial disorder with significant inter-patient variability poorly predicted by clinical and procedural factors. We tested the hypothesis that candidate gene polymorphisms in inflammatory pathways contribute to risk of PMI after cardiac surgery. METHODS AND RESULTS: We genotyped 48 polymorphisms from 23 candidate genes in a prospective cohort of 434 patients undergoing elective cardiac surgery with CPB. PMI was defined as creatine kinase-MB isoenzyme level > or = 10x upper limit of normal at 24 hours postoperatively. A 2-step analysis strategy was used: marker selection, followed by model building. To minimize false-positive associations, we adjusted for multiple testing by permutation analysis, Bonferroni correction, and controlling the false discovery rate; 52 patients (12%) experienced PMI. After adjusting for multiple comparisons and clinical risk factors, 3 polymorphisms were found to be independent predictors of PMI (adjusted P<0.05; false discovery rate <10%). These gene variants encode the proinflammatory cytokine interleukin 6 (IL6 -572G>C; odds ratio [OR], 2.47), and 2 adhesion molecules: intercellular adhesion molecule-1 (ICAM1 Lys469Glu; OR, 1.88), and E-selectin (SELE 98G>T; OR, 0.16). The inclusion of genotypic information from these polymorphisms improved prediction models for PMI based on traditional risk factors alone (C-statistic 0.764 versus 0.703). CONCLUSIONS: Functional genetic variants in cytokine and leukocyte-endothelial interaction pathways are independently associated with severity of myonecrosis after cardiac surgery. This may aid in preoperative identification of high-risk cardiac surgical patients and development of novel cardioprotective strategies.

Aged↗
PubMed2006

Facilitating learning in the operating theatre and intensive care unit.

Almost every aspect of anaesthetic and intensive care practice can be taught within the operating theatre and intensive care unit. This includes knowledge in the areas of medicine, anatomy, pharmacology, physiology, measurement and statistics, invaluable psychomotor and global skills and abilities, as well as the many important non-clinical aspects of anaesthesia and intensive care including effective communication, leadership, management, ethics and teaching. The operating theatre and intensive care unit offer many advantages and pose numerous challenges to education. This paper briefly discusses what can be taught in the operating theatre and intensive care unit, the educational challenges and benefits of teaching in these unique environments, implications for teaching and what consultants and trainees can do to positively influence the educational activity. The paper concludes with suggestions for facilitating learning in the operating theatre and intensive care unit including the Soldier's Five, practice vivas, skills training, endoscopic dexterity, interesting article exchange, in-service sessions, electronic resources and use out of hours.

Anesthesiology↗
PubMed2005

Alcohol intake in middle age and risk of cardiovascular disease and mortality: accounting for intake variation over time.

Moderate alcohol consumption is associated with a decreased risk of cardiovascular disease. However, the impact of variation in alcohol intake over time on estimated risk relations has not been adequately addressed. In this study, 6,544 middle-aged British men without previous cardiovascular disease were followed for cardiovascular events and all-cause mortality over 20 years from 1978/1980 to 1998/2000. Alcohol intake was ascertained at regular points throughout the study. A total of 922 men had a major coronary event within 20 years, 352 men had a stroke, and 1,552 men died of all causes. Baseline alcohol intake displayed U-shaped relations with cardiovascular disease and all-cause mortality, with light drinkers having the lowest risks and nondrinkers and heavy drinkers having similarly high risks. However, the nature of these relations changed after adjustment for intake variation; risks associated with nondrinking were lowered, and risks associated with moderate and heavy drinking increased. Regular heavy drinkers had a 74% higher risk of a major coronary event, a 133% higher risk of stroke, and a 127% higher risk of all-cause mortality than did occasional drinkers (these estimates were 8%, 54%, and 44% before adjustment for intake variation). The findings suggest that considerable caution may be needed before any recommendations regarding acceptable limits of alcohol consumption are made.

Adult↗
PubMed2005

A Markov chain model for animal estrous cycling data.

Estrous cycling data contain sequences of characters (e.g., DPEMD). Each sequence represents an animal's estrous cycle, with each character indicating the daily estrous cycle stage. Changes in the estrous cycle pattern, which is determined by estrous stage lengths, can provide information on adverse events. Stage lengths are not directly observable. However interval censored lengths for all but the first and the last stages in a sequence can be extracted from the data. We propose a Markov chain model to approximate the estrous cycling process. The transition probabilities from one stage to another can be derived by conditioning on stage lengths. Assuming Weibull distribution for stage lengths, with the second Weibull parameter depending upon treatment effects and animal-specific random effects, regression models on censored stage lengths are fitted. A Bayesian approach is used for inference on dose effects. The analysis is implemented with MCMC method in WinBUGS. An estrous cycling data set from a National Toxicology Program study is analyzed as an example.

Animals↗
PubMed2005

Inequalities in coronary revascularisation during the 1990s: evidence from the British regional heart study.

OBJECTIVE: To investigate the influence of age and social circumstances on probability of revascularisation among British men. DESIGN: Prospective population based study SETTING: 24 medium sized British towns, none of which contained a hospital undertaking coronary artery bypass surgery. SUBJECTS: 5814 surviving participants of the BRHS (British regional heart study), aged 52-73 years, with no history of revascularisation when responding to a questionnaire in November 1992. MAIN OUTCOMES: Incident coronary revascularisations, as documented in general practitioner records, over the following 7.1 years and coronary angiography investigations reported by men in a further questionnaire in November 1996. RESULTS: 160 men underwent at least one revascularisation during this period (4.2/1000 person-years). In multifactorial analysis, which included adjustment for incidence of major coronary heart disease or angina, a lower incidence of revascularisation was found among men aged over 65 years in November 1992 (hazard ratio 0.62, 95% confidence interval (CI) 0.44 to 0.87), among men with manual occupations (0.73, 95% CI 0.53 to 1.02), among men living in households possessing no car (0.44, 95% CI 0.24 to 0.80) or one car (0.60, 95% CI 0.42 to 0.87) compared with two or more cars, among council tenants (0.49, 95% CI 0.25 to 0.97), and among men living outside southern England (0.71, 95% CI 0.51 to 0.99). Only car ownership was related to the incidence of diagnostic angiography: the odds ratio for angiography for those owning fewer than two cars was 0.62 (95% CI 0.42 to 0.89). CONCLUSION: During the 1990s, there were major inequalities in the probability of undergoing coronary revascularisation between British men according to socioeconomic status, age, and geographic location.

Age Factors↗
PubMed2005

Crisis management during anaesthesia: the development of an anaesthetic crisis management manual.

BACKGROUND: All anaesthetists have to handle life threatening crises with little or no warning. However, some cognitive strategies and work practices that are appropriate for speed and efficiency under normal circumstances may become maladaptive in a crisis. It was judged in a previous study that the use of a structured "core" algorithm (based on the mnemonic COVER ABCD-A SWIFT CHECK) would diagnose and correct the problem in 60% of cases and provide a functional diagnosis in virtually all of the remaining 40%. It was recommended that specific sub-algorithms be developed for managing the problems underlying the remaining 40% of crises and assembled in an easy-to-use manual. Sub-algorithms were therefore developed for these problems so that they could be checked for applicability and validity against the first 4000 anaesthesia incidents reported to the Australian Incident Monitoring Study (AIMS). METHODS: The need for 24 specific sub-algorithms was identified. Teams of practising anaesthetists were assembled and sets of incidents relevant to each sub-algorithm were identified from the first 4000 reported to AIMS. Based largely on successful strategies identified in these reports, a set of 24 specific sub-algorithms was developed for trial against the 4000 AIMS reports and assembled into an easy-to-use manual. A process was developed for applying each component of the core algorithm COVER at one of four levels (scan-check-alert/ready-emergency) according to the degree of perceived urgency, and incorporated into the manual. The manual was disseminated at a World Congress and feedback was obtained. RESULTS: Each of the 24 specific crisis management sub-algorithms was tested against the relevant incidents among the first 4000 reported to AIMS and compared with the actual management by the anaesthetist at the time. It was judged that, if the core algorithm had been correctly applied, the appropriate sub-algorithm would have been resolved better and/or faster in one in eight of all incidents, and would have been unlikely to have caused harm to any patient. The descriptions of the validation of each of the 24 sub-algorithms constitute the remaining 24 papers in this set. Feedback from five meetings each attended by 60-100 anaesthetists was then collated and is included. CONCLUSION: The 24 sub-algorithms developed form the basis for developing a rational evidence-based approach to crisis management during anaesthesia. The COVER component has been found to be satisfactory in real life resuscitation situations and the sub-algorithms have been used successfully for several years. It would now be desirable for carefully designed simulator based studies, using naive trainees at the start of their training, to systematically examine the merits and demerits of various aspects of the sub-algorithms. It would seem prudent that these sub-algorithms be regarded, for the moment, as decision aids to support and back up clinicians' natural responses to a crisis when all is not progressing as expected.

Algorithms↗
PubMed2005

Crisis management during anaesthesia: recovering from a crisis.

Preventing harm to the patient is the priority during a crisis. After a major incident, and especially when a patient has been harmed, there are a number of matters to be addressed: the ongoing care of the patient; documentation of the incident; investigation of the root causes; completion of reports; interviews with the patient and/or the next of kin, together with apologies and expression of regret; updates and ongoing support for friends and relatives; a word of thanks to the staff involved for their assistance; formal debriefing of staff for quality assurance and possibly ongoing support and a separate debriefing for psychological purposes; ensuring that the recommendations of the root cause analysis are carried out; or, failing that, that the issues are logged on a risk register. The extent and depth of the follow up protocol depends on what, if any, harm may have been done. This may constitute completion of an incident report; notification of an equipment failure to a federal regulatory authority; arranging consultations with a mental health professional to manage psychological sequelae (especially following an awareness episode); follow up during weeks of intensive care treatment; or, when a death has occurred, a full medico-legal and/or coronial set of procedures. A precis is appended in an action card format.

Algorithms↗
PubMed2005

Crisis management during regional anaesthesia.

BACKGROUND: Regional anaesthesia is widely used and has been considered to pose few risks once the block is established. However, life threatening problems can occur both during the establishment and maintenance phases of a regional block which require prompt recognition and management. OBJECTIVES: To examine the role of a previously described core algorithm "COVER ABCD-A SWIFT CHECK", supplemented by a specific sub-algorithm for regional anaesthesia, in the management of problems arising in association with regional anaesthesia. METHODS: The potential performance of this structured approach was assessed for each of the relevant incidents among the first 4000 reported to the Australian Incident Monitoring Study (AIMS). RESULTS: There were 252 incidents involving regional anaesthesia, 6.3% of the first 4000 reports to AIMS. Of these, the majority (78%) involved the use of epidural or spinal anaesthesia. The core algorithm AB COVER CD properly applied, would have accounted for 45% of all problems, and is worth applying to eliminate unexpected problems unrelated to the regional anaesthesia technique itself. Hypotension and dysrhythmias made up over 30% of all incidents and accounted for all six deaths in the 252 incidents. The specific sub-algorithm for regional anaesthetic techniques accounted for 55% of all incidents: problems with delivery to the site of action, 49 cases (19%); problems with the block, 30 cases (12%); local anaesthetic toxicity, 30 cases (12%); trauma, infection, or pain, 14 cases (6%), wrong side or wrong patient, five cases (2%). CONCLUSION: Based on an analysis of 252 incidents, the core algorithm and the regional anaesthesia sub-algorithm, properly applied, would lead to swift recognition and appropriate management of problems arising in association with regional anaesthesia.

Algorithms↗
PubMed2005

Crisis management during anaesthesia: tachycardia.

BACKGROUND: Tachycardia during anaesthesia is a common event. In most cases the cause is easily identified and the problem promptly resolved. However, in some the cause may be rare or obscure. Under such circumstances, attempting to initiate appropriate supportive therapy and to consider a large differential diagnosis in a comprehensive manner may lead to delays which can put a patient at risk. OBJECTIVES: To examine the role of a previously described core algorithm "COVER ABCD-A SWIFT CHECK", supplemented by a specific sub-algorithm for tachycardia, in the management of tachycardia developing in association with anaesthesia. METHODS: The potential performance of this structured approach for each of the relevant incidents among the first 4000 reported to the Australian Incident Monitoring Study (AIMS) was compared with the actual management as reported by the anaesthetists involved. RESULTS: There were 145 causative events identified in 123 reports of tachycardia during anaesthesia which were extracted and studied from the first 4000 incidents reported to AIMS. Subgroups were identified based on blood pressure at the time of presentation. Of the 145 causes, tachycardia was associated with hypotension (33%), normotension (27%), hypertension (26%), and cardiac arrest (17%). For simplicity it is recommended that other cardiovascular sub-algorithms are followed when the blood pressure is also abnormal. This includes cardiac arrest and hypotension. In hypotensive states the tachycardia sub-algorithm should be followed until the cardiac rhythm is diagnosed. Sinus tachycardia and hypotension should be managed as hypotension. It was considered that, correctly applied, the core algorithm COVER would have diagnosed 35% of cases and led to resolution in 70% of these. It was estimated that completion of COVER followed by the sub-algorithm for tachycardia would have led to earlier recognition of the problem and/or better management in four cases when compared with actual management reported. CONCLUSION: Tachycardia during anaesthesia is frequently associated with a simultaneous change in other monitored vital signs. The differential diagnosis is large. Addressing it in a comprehensive fashion requires a structured approach. A specific sub-algorithm treatment for tachycardia based on the associated blood pressure and on the prevailing heart rhythm in the case of hypotension offers a systematic guide which complements the benefits obtained by employing the core algorithm COVER ABCD.

Algorithms↗
PubMed2005

Crisis management during anaesthesia: hypotension.

BACKGROUND: Hypotension is commonly encountered in association with anaesthesia and surgery. Uncorrected and sustained it puts the brain, heart, kidneys, and the fetus in pregnancy at risk of permanent or even fatal damage. Its recognition and correction is time critical, especially in patients with pre-existing disease that compromises organ perfusion. OBJECTIVES: To examine the role of a previously described core algorithm "COVER ABCD-A SWIFT CHECK", supplemented by a specific sub-algorithm for hypotension, in the management of hypotension when it occurs in association with anaesthesia. METHODS: Reports of hypotension during anaesthesia were extracted and studied from the first 4000 incidents reported to the Australian Incident Monitoring Study (AIMS). The potential performance of the COVER ABCD algorithm and the sub-algorithm for hypotension was compared with the actual management as reported by the anaesthetist involved. RESULTS: There were 438 reports that mentioned hypotension, cardiovascular collapse, or cardiac arrest. In 17% of reports more than one cause was attributed and 550 causative events were identified overall. The most common causes identified were drugs (26%), regional anaesthesia (14%), and hypovolaemia (9%). Concomitant changes were reported in heart rate or rhythm in 39% and oxygen saturation or ventilation in 21% of reports. Cardiac arrest was documented in 25% of reports. As hypotension was frequently associated with abnormalities of other vital signs, it could not always be adequately addressed by a single algorithm. The sub-algorithm for hypotension is adequate when hypotension occurs in association with sinus tachycardia. However, when it occurs in association with bradycardia, non-sinus tachycardia, desaturation or signs of anaphylaxis or other problems, the sub-algorithm for hypotension recommends cross referencing to other relevant sub-algorithms. It was considered that, correctly applied, the core algorithm COVER ABCD would have diagnosed 18% of cases and led to resolution in two thirds of these. It was further estimated that completion of this followed by the specific sub-algorithm for hypotension would have led to earlier recognition of the problem and/or better management in 6% of cases compared with actual management reported. CONCLUSION: Pattern recognition in most cases enables anaesthetists to determine the cause and manage hypotension. However, an algorithm based approach is likely to improve the management of a small proportion of atypical but potentially life threatening cases. While an algorithm based approach will facilitate crisis management, the frequency of co-existing abnormalities in other vital signs means that all cases of hypotension cannot be dealt with using a single algorithm. Diagnosis, in particular, may potentially be assisted by cross referencing to the specific sub-algorithms for these.

Algorithms↗
PubMed2005

Crisis management during anaesthesia: cardiac arrest.

BACKGROUND: Cardiac arrest attributable to anaesthesia occurs at the rate of between 0.5 and 1 case per 10 000 cases, tends to have a different profile to that of cardiac arrest occurring elsewhere, and has an in-hospital mortality of 20%. However, as individual practitioners encounter cardiac arrest rarely, the rapidity with which the diagnosis is made and the consistency of appropriate management varies considerably. OBJECTIVES: To examine the role of a previously described core algorithm "COVER ABCD-A SWIFT CHECK", supplemented by a sub-algorithm for cardiac arrest, in the management of cardiac arrest occurring in association with anaesthesia. METHODS: The potential performance of this structured approach for each the relevant incidents among the first 4000 reported to the Australian Incident Monitoring Study (AIMS) was compared with the actual management as reported by the anaesthetists involved. RESULTS: There were 129 reports of cardiac arrest associated with anaesthesia among the first 4000 AIMS incident reports. Identified aetiological factors were grouped into five categories: (1) anaesthetic technique (11 cases with this category alone; 32 with this and one or more of the other categories, representing 25% of all 129 cardiac arrests); (2) drug related (16; 32, 25%); (3) associated with surgical procedure (9; 29, 22%); (4) associated with pre-existing medical or surgical disease (30; 82, 64%); (5) unknown (8; 14, 11%). The "real life" presentation and management of cardiac arrest in association with anaesthesia differs substantially from that detailed in general published guidelines. Cardiac rhythms at the time were sinus bradycardia (23%); asystole (22%); tachycardia/ventricular tachycardia/ventricular fibrillation (14%); and normal (7%), with a further third unknown. Details of treatment were recorded in 110 reports; modalities employed included cardiac compression (72%); adrenaline (61%); 100% oxygen (58%); atropine (38%); intravenous fluids (25%), and electrical defibrillation (17%). There were no deaths or permanent morbidity in the 11 cases due solely to anaesthetic technique. 24 of the 25 deaths occurred in patients with significant pre-existing medical or surgical disease. CONCLUSION: Because there are often multiple contributing factors to a cardiac arrest under anaesthesia, a complete systematic assessment of the patient, equipment, and drugs should be completed. The "COVER ABCD-A SWIFT CHECK" algorithm was judged to be a satisfactory process in this context and should be carried out even if the cause of the cardiac arrest is already thought to have been found. The diagnosis and management of cardiac arrest in association with anaesthesia differs considerably from that encountered elsewhere. The outcome is generally good, with most patients leaving hospital alive and apparently well.

Algorithms↗
PubMed2005

Crisis management during anaesthesia: bradycardia.

BACKGROUND: Bradycardia in association with anaesthesia may have many potential causes and associated conditions, some rare and/or obscure. A prompt appropriate response is important as some homeostatic mechanisms may be impaired under anaesthesia. OBJECTIVES: To examine the role of a previously described core algorithm "COVER ABCD-A SWIFT CHECK", supplemented by a specific sub-algorithm for bradycardia, in the management of bradycardia occurring in association with anaesthesia. METHODS: The potential performance of this structured approach for each of the relevant incidents among the first 4000 reported to the Australian Incident Monitoring Study (AIMS) was compared with the actual management as reported by the anaesthetists involved. RESULTS: From the first 4000 incidents reported to AIMS, 265 reports which described bradycardia during anaesthesia were extracted and studied. Bradycardia was associated with hypotension in 51% of cases, cardiac arrest in 25% of cases and hypertension in one case. In 22% of reports apparent desaturation or an abnormality of ventilation was described. Bradycardia was caused by drug events (28%), airway related events (16%), autonomic reflexes (14%), and regional anaesthesia (9%). Airway and drug events caused 75% of cases involving children. It was considered that, correctly applied, the core algorithm COVER would have diagnosed 53 cases (20%) and led to corrective management in 45 (85%) of these; this included an important subset of airway and ventilation problems. Completion of COVER ABCD-A SWIFT CHECK followed by the specific sub-algorithm for bradycardia would have resulted in diagnosis and appropriate management in all but two cases. It would have led to earlier recognition of the problem and/or better management in 11 cases (4%) when compared with the actual management described in the reports. CONCLUSION: Steps should be taken to manage bradycardia whilst associated conditions are managed concurrently. Analysis of cardiac rhythm should not be pursued to the exclusion of supportive therapy. The use of a structured approach in the management of bradycardia associated with anaesthesia is likely to improve management in the small percentage of cases in which the diagnosis of the cause may be missed or delayed.

Algorithms↗
PubMed2005

Trauma: development of a sub-algorithm.

BACKGROUND: Anaesthetists are regularly involved in the management of patients who have suffered trauma. Acute physiological derangements can occur at any time after the original injury, with life threatening sequelae. These problems may be complex in nature and evolve rapidly, often with an obscure aetiology, so a systematic approach to them is essential. OBJECTIVES: To examine the role of a previously described core algorithm "COVER ABCD-A SWIFT CHECK" supplemented by a specific sub-algorithm for trauma, in the management of anaesthesia involving trauma cases. METHODS: The potential performance of a structured approach for each of the trauma incidents among the first 4000 incidents reported to the Australian Incident Monitoring Study (AIMS) was compared with the actual performance as reported by the anaesthetists involved. RESULTS: There were 38 relevant reports relating to trauma in the first 4000 reports to AIMS. In 39% of these there was "emergency corner cutting", although in the majority the urgency was thought to have been more perceived than real. The previously described "core" crisis management algorithm for crises during general anaesthesia was an effective means of discovering (82%), diagnosing (68%), and correcting (66%) the majority of trauma incidents. However a sub-algorithm specific for the traumatised patient was required for unusual, obscure, or complex presentations. CONCLUSION: Although the small numbers preclude validation of the sub-algorithm, it would have successfully managed all the trauma cases reported to AIMS.

Algorithms↗
PubMed2005

How well can anaesthetists discriminate pulse oximeter tones?

The ability of experienced anaesthetists to discern oxygen saturation by listening to the tones of a Datex AS3 pulse oximeter was examined. Five-second samples were recorded using a high fidelity patient simulator and replayed singly and in pairs. Whilst the lower saturations were generally recognized as lower, the perceived range was greatly compressed. Median perceived estimates for 70% saturation was 89%, for 80% was 93% and for 94% was 94%. When comparing pairs of samples, the direction of the difference was correctly discerned by 70% of anaesthetists for differences of 2%, rising to 95% for differences of greater than 8% oxygen saturation. The magnitude of the difference was consistently underestimated. With an actual difference of 20%, the median estimate was 5%. The results indicate that while qualitative estimate changes in oxygen saturation are moderately reliable, quantitative estimation is severely limited by a compromised perceived scale. This may lead to underestimation of the severity if the auditory signal is relied on in isolation. A non-linear (musical) scale may prove more appropriate and should be investigated. Testing experienced anaesthetists demonstrated that most could detect the direction, but not the magnitude of a change in saturation by listening to the change in pitch of a Datex AS3 pulse oximeter tone.

Adult↗