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Biomedical subjects

P S Myles

Publications and source records attributed to P S Myles.

At least 19 recordsLinked to original sources
PubMed2006

Prophylaxis of postoperative vomiting in children undergoing tonsillectomy: a systematic review and meta-analysis.

Postoperative vomiting (POV) remains one of the commonest causes of significant morbidity after tonsillectomy in children. A variety of prophylactic anti-emetic interventions have been reported, but there has only been a limited systematic review in this patient group. A systematic search was performed by using Cochrane Controlled Trials Register, MEDLINE and EMBASE to identify double-blind, randomized, placebo-controlled trials of prophylactic anti-emetic interventions in children undergoing tonsillectomy, with or without adenoidectomy. The outcome of interest was POV in the first 24 h. Summary estimates of the effect of each prophylactic anti-emetic strategy were derived using fixed effect meta-analysis. Where appropriate, dose-response effects were estimated using logistic regression and 22 articles were identified. Good evidence was found for the prophylactic anti-emetic effect of dexamethasone [odds ratio (OR) 0.23, 95% CI 0.16-0.33], and the serotinergic antagonists ondansetron (OR 0.36, 95% CI 0.29-0.46), granisetron (OR 0.11, 95% CI 0.06-0.19), tropisetron (OR 0.15, 95% CI 0.06-0.35) and dolasetron (OR 0.25, 95% CI 0.1-0.59). Metoclopramide was also found to be efficacious (OR 0.51, 95% CI 0.34-0.77). There is not sufficient evidence to suggest that dimenhydrinate, perphenazine or droperidol, in the doses studied, are efficacious, nor were gastric aspiration or acupuncture. In conclusion, dexamethasone and the anti-serotinergic agents appear to be the most effective agents for the prophylaxis for POV in children undergoing tonsillectomy.

Antiemetics↗
PubMed2006

Myocardial protection with volatile anaesthetic agents during coronary artery bypass surgery: a meta-analysis.

Previous studies have investigated the role of volatile anaesthetic agents in myocardial protection during coronary artery bypass graft (CABG) surgery, and some have identified beneficial effects. However, these studies have been too small to identify a significant effect on myocardial infarction (MI) or mortality. We undertook a systematic overview and meta-analysis of all randomized trials comparing volatile with non-volatile anaesthesia in CABG surgery. We identified 27 trials that included 2979 patients. There was no significant difference in myocardial ischaemia, MI, intensive care unit length of stay or hospital mortality between the groups (all P>0.05). Post-bypass, patients randomized to receive volatile anaesthetics had 20% higher cardiac indices (P=0.006), significantly lower troponin I serum concentrations (P=0.002) and lesser requirement for inotropic support (P=0.004) compared with those randomized to receive i.v. anaesthetics. Duration of mechanical ventilation was reduced by 2.7 h (P=0.04), and there was a 1 day decrease in hospital length of stay (P<0.001). Some of these outcomes were based on a smaller number of trials because of incomplete data, largely because the individual trials focused on one or more surrogate endpoints. We found some evidence that volatile anaesthetic agents provide myocardial protection in CABG surgery, but larger adequately powered trials with agreed, defined outcomes need to be done to fully assess a possible beneficial effect of volatile anaesthetic agents on the risk of MI and mortality.

Anesthetics↗
PubMed2006

Depth of anaesthesia monitoring: what's available, what's validated and what's next?

Depth of anaesthesia monitors might help to individualize anaesthesia by permitting accurate drug administration against the measured state of arousal of the patient. In addition, the avoidance of awareness or excessive anaesthetic depth might result in improved patient outcomes. Various depth of anaesthesia monitors based on processed analysis of the EEG or mid-latency auditory-evoked potentials are commercially available as surrogate measures of anaesthetic drug effect. However, not all of them are validated to the same extent.

Anesthesia, General↗
PubMed2006

A comparison of the analgesic efficacy and side-effects of paravertebral vs epidural blockade for thoracotomy--a systematic review and meta-analysis of randomized trials.

Epidural analgesia is considered by many to be the best method of pain relief after major surgery. It is used routinely in many thoracic surgery centres. Although effective, side-effects include hypotension, urinary retention, incomplete (or failed) block, and, in rare cases, paraplegia. Paravertebral block (PVB) is an alternative technique that may offer comparable analgesic effectiveness and a better side-effect profile. We undertook a systematic review and meta-analysis of all relevant randomized trials comparing PVB with epidural analgesia in thoracic surgery. Data were abstracted and verified by both authors. Studies were tested for heterogeneity, and meta-analyses were done with random effects or fixed effects models. Weighted mean difference (WMD) was used for numerical outcomes and odds ratio (OR) for dichotomous outcomes, both with 95% CI. We identified 10 trials that had enrolled 520 thoracic surgery patients. All of the trials were small (n<130) and none were blinded. There was no significant difference between PVB and epidural groups for pain scores at 4-8, 24 or 48 h, WMD 0.37 (95% CI: -0.5, 121), 0.05 (-0.6, 0.7), -0.04 (-0.4, 0.3), respectively. Pulmonary complications occurred less often with PVB, OR 0.36 (0.14, 0.92). Urinary retention, OR 0.23 (0.10, 0.51), nausea and vomiting, OR 0.47 (0.24, 0.53), and hypotension, OR 0.23 (0.11, 0.48), were less common with PVB. Rates of failed block were lower in the PVB group, OR 0.28 (0.2, 0.6). PVB and epidural analgesia provide comparable pain relief after thoracic surgery, but PVB has a better side-effect profile and is associated with a reduction in pulmonary complications. PVB can be recommended for major thoracic surgery.

Analgesia, Epidural↗
PubMed2006

Communication deficiencies in research and monitoring by ethics committees.

AIM: To assess the range of issues that arise for researchers, research participants and ethics committee members in the setting of a hospital-based research environment and to develop a tool that could be used to assist in the process of monitoring. METHODS: A qualitative phase comprising focus group sessions and interviews involving research participants, researchers and ethics committee members of a public teaching hospital and a quantitative phase involving distribution of a questionnaire to research participants and researchers. The data from the qualitative phase were used to assist with the development of the quantitative instrument. Descriptive statistics were derived to describe the various attitudes and practices with respect to the conduct of research. RESULTS: The qualitative study identified issues concerning monitoring procedures and the quality of communication between researchers and study participants. The quantitative analysis showed that parts of the Explanatory Statement (also known as the Participant Information Statement) were incomprehensible to 21% of research participants; the Explanatory Statement was considered too long by 34% of researchers; 6% of researchers believed that explicit consent was not always necessary; of the participants who were out of pocket for attending a study, 53% were offered compensation; and 44% of research participants were unaware of the existence of the ethics committee. In addition, 12% of researchers felt that the quality of monitoring should be improved. CONCLUSIONS: Improvements are necessary in the communication between ethics committees and researchers and research participants, and there is a need for more effective monitoring by ethics committees of research practices. The questionnaire designed for this study could be applied in a prospective manner as a useful tool for monitoring the conduct of research.

Adult↗
PubMed2006

Quality of life at three years after cardiac surgery: relationship with preoperative status and quality of recovery.

A reduction in symptoms, increased longevity, and improved quality of life (QoL), are goals of cardiac surgery. We measured QoL in 108 adult cardiac surgical patients at about three years after cardiac surgery, and assessed the predictive ability of a 40-item quality of recovery (QoR-40) score. Our follow-up rate was 86% (n = 93). When compared with preoperative status, QoL was improved at three years after surgery (P < 0.0005). The dimensions of QoL that were most affected were physical functioning, role limitations due to physical problems, vitality, social functioning, and role limitations due to emotional problems (all P < 0.005). There was a mild correlation between the day 3 QoR-40 and the three year SF-36, r = 0.23 (P = 0.029). There was a strong correlation between the three year QoR-40 and the three year SF-36, r = 0.73 (P < 0.0005). The QoR-40 and SF-36 done at three years after cardiac surgery demonstrated good internal consistency, QoR-40 alpha = 0.86 (P < 0.0005), SF-36 alpha = 0.91 (P < 0.0005). A poor quality recovery in the days after surgery can predict a poor QoL at three years after surgery. The QoR-40 is a valid and reliable measure of quality of recovery after surgery and anaesthesia. The QoR-40 is a useful, patient-oriented method of assessing recovery from anaesthesia and surgery.

Cardiac Surgical Procedures↗
PubMed2006

Outcomes following a shortage of high dependency unit beds for surgical patients.

In an environment of resource rationing there are numerous patients who are unable to be admitted to a high-dependency unit (HDU) postoperatively despite the belief that this is the optimal discharge destination for them from the recovery room. It is unknown if this is associated with an increase in adverse outcomes. We performed an observational study, over a two-month period, comparing outcomes between patients who were admitted to HDU postoperatively and patients who, although an HDU bed was preferred, were discharged from the recovery room to the general ward due to an unavailability of HDU beds. Our primary outcome variable was hospital length-of-stay. We found an almost twofold increase in hospital length-of-stay in the group of patients admitted to the HDU. ASA IV patients were more likely to be admitted to HDU. However, the increased length-of-stay in the HDU group persisted even after stratifying patients according to ASA status. There was no difference between groups in all other baseline demographic variables, including POSSUM score, which is used as a predictor of postoperative morbidity and mortality. We believe that the most likely explanation for our findings is that the baseline risk between groups is, in fact, subtly different. This is not detected by preoperative scoring systems. However, clinical judgement in the recovery room appears to select a group of patients for HDU admission who subsequently have a slower postoperative recovery, despite no measurable increase in complication rate. That there was no increase in adverse events in the group of patients unable to be admitted to HDU due to a lack of bed availability suggests that current clinical judgement in a resource-rationed environment is functioning adequately, but the study was not powered to detect such a difference.

Adult↗
PubMed2006

A comparison of patient self-administered and investigator-administered measurement of quality of recovery using the QoR-40.

A 40-item questionnaire (the QoR-40) had been previously developed to measure five dimensions of quality of recovery after anaesthesia and surgery. Each of the 40 items is rated on a scale of 1 to 5, with a maximum score of 200. In this study we compared patient self-administered with investigator-administered QoR-40. We studied 62 postoperative patients within 48 hours of their surgery. Agreement between the two methods was analysed using the intraclass correlation coefficient, bias and limits of agreement. There was strong correlation between the investigator-administered and patient self-administered QoR-40 scores, intraclass correlation coefficient 0.86 (95% CI: 0.77 to 0.92), P<0.001. The bias and limits of agreement were 3.1 and -22 to 28, respectively. There were 10 (16%) patient self-administered questionnaires that were not completed at first attempt. The time to complete the questionnaire when investigator-administered was 253 (16) s [mean, (SD)], and on first attempt for patients was 362 (19) s, P<0.001. The QoR-40 is as valid measure of postoperative recovery when administered with the assistance of an investigator as compared with the patient self-administered version. Investigator-administered measurement of the QoR-40 is a more efficient use of resources, as complete and more timely data are collected.

Adolescent↗
PubMed2005

Effect of clonidine pre-medication on propofol requirements during lower extremity vascular surgery: a randomized controlled trial.

BACKGROUND: Pre-medication with clonidine reduces the requirement for volatile agents during general anaesthesia. This may also be true for anaesthesia with propofol, but the amount of dose reduction has not been measured. Because clonidine also affects cardiac output and thus regional blood flow it could alter the pharmacokinetics of propofol. This randomized, double-blind placebo-controlled trial aimed to study the effect of clonidine pre-medication on dose requirement for propofol during lower extremity vascular surgery using the bispectral index (BIS) as a measure of anaesthetic depth. METHODS: After oral pre-medication with either clonidine 3 microg kg(-1) or placebo, 39 subjects had lower limb vascular surgery using propofol infusion for anaesthesia. Anaesthetic depth was adjusted to a BIS of 45. Predicted plasma propofol concentrations were noted every 30 min from a target-controlled propofol infusion pump and arterial samples were taken at the same time for propofol measurements. RESULTS: Patients in both groups were anaesthetized to similar depths of anaesthesia as indicated by BIS readings (P=0.44). The groups had comparable mean (95% CI) arterial concentrations of propofol, 4.8 (3.5-6.1) microg ml(-1) in the patients given clonidine, and 4.6 (3.4-5.7) microg ml(-1) in the patients given placebo (P=0.81). However, the average plasma concentration predicted by the target-controlled infusion was less in the clonidine group [3.2 (2.9-3.5)] than in the group given placebo [3.6 (3.3-3.9)] microg ml(-1) (P<0.05). CONCLUSIONS: Pre-medication with clonidine reduces the requirement for propofol, which is a pharmacokinetic effect and not a pharmacodynamic central sedative effect.

Aged↗
PubMed2005

Dreaming during anaesthesia in patients at high risk of awareness.

Dreaming during anaesthesia is commonly reported but remains poorly understood. In this study, adult surgical patients at high risk of awareness were randomly assigned to receive bispectral index (BIS)-guided anaesthesia or routine care, and were interviewed about dreaming three times postoperatively. Dreaming patients (n = 134) were compared with all other patients who were interviewed at least once (n = 2251). Intraoperative dreaming was reported by 4.2%, 3.9% and 3.4% of patients at 2-4 h, 24-36 h and 30 days after surgery, respectively. Fewer BIS-monitored patients reported intra-operative dreaming at 2-4 h than control patients (2.7% vs. 5.7%; p = 0.004). Reports of dreaming were similar in the two groups at 24-36 h and 30 days. Dreaming patients were younger (p = 0.001); healthier (p < 0.001) and more likely to be women (p < 0.001), and were less satisfied with anaesthetic care (p = 0.004) than other patients.

Adult↗
PubMed2005

The linearity of the visual analogue scale in patients with severe acute pain.

The visual analogue scale (VAS) is a standard measurement tool in pain research and clinical practice, and has been shown to have linear scale properties for mild to moderate pain. Our aim was to evaluate the scaling properties of the VAS in subjects with severe acute pain. After Ethics Committee approval we studied 22 patients and asked them to rate the severity of their pain on a 100 mm VAS at the initial assessment (VAS1), and again after administration of analgesic medication. The subject was asked to nominate when they considered their pain intensity had halved, and at this time they were asked to rate this on a second VAS (VAS0.5). When the subject had received satisfactory relief of their pain, they were asked to describe how much their pain had been relieved and were then asked to rate their final pain state using a third VAS (VASfinal). The mean (SD) scores were VAS1 84 (14) (range 56-100), VAS0.5 42 (13) and VASfinal 21 (16). The mean (95% CI) for VASratio was 0.51 (0.45-0.57). The mean (SD) patients' estimate of pain relief was 77 (21)% from that of baseline, with a mean (SD) VASfinal 0.26 (0.20), 95% CI 0.17-0.38. The correlation of the patients' estimate of pain relief with the VASfinal was r=0.89, rho=0.87, both P<0.001. The VAS is a linear scale in subjects with severe acute pain. Changes in the VAS score represent a relative change in the magnitude of pain sensation.

Adolescent↗
PubMed2005

Recovery from bispectral index-guided anaesthesia in a large randomized controlled trial of patients at high risk of awareness.

Electroencephalographic monitors of anaesthetic depth are reported to assist anaesthetists in reducing recovery times. We explored the effect of bispectral index (BIS) monitoring on recovery times in a double-blind, randomized controlled trial of 2,463 patients at high risk of awareness. Patients were randomized to BIS-guided anaesthesia or routine care. In the BIS group, anaesthesia was adjusted to maintain a BIS value of 40-60 from the commencement of laryngoscopy to the start of wound closure, and 55-70 during wound closure. In the routine care group, anaesthesia was adjusted according to traditional clinical signs. In multivariate models, BIS monitoring, female gender, lower American Society of Anesthesiologists' physical status and shorter duration of anaesthesia predicted faster time to eye-opening after anaesthesia, and faster time to post-anaesthesia care unit discharge. BIS monitoring did not affect times to tracheal extubation among patients admitted to the intensive care unit. We conclude that BIS monitoring has statistically significant, but clinically modest, effects on recovery times in high risk surgical patients.

Adult↗
PubMed2005

Relationship between journal impact factor and levels of evidence in anaesthesia.

Evidence-based medicine uses a hierarchy of publication types according to their vulnerability to bias. A widely used measure of journal "quality" is its impact factor, which describes the citation rate of its publications. We investigated the relationship between impact factor for eight anaesthesia journals and publication type with respect to their level of evidence 1-4 using Spearman rank correlation (rho). There were 1418 original publications during 2001 included in the analysis. The number (%) of publication types according to evidence-based medicine level were: level 1:6 (0.4%), level 2:533 (38%) level 3:329 (23%), level 4:550 (39%). There was no correlation between journal ranking according to impact factor and publication type (rho =-0.03, P=0.25). The correlation between journal rank and the proportion of publications that were randomized trials was -0.35 (P<0.001). The correlation between journal rank and number of publications was 0.65 (P<0.001). The correlation between journal rank and number of level 1 or 2 studies was 0.58 (P<0.001). The overall level of evidence published in anaesthesia journals was high. Journal rank according to impact factor is related to the number of publications, but not the proportion of publications that are evidence-based medicine level 1 or 2.

Anesthesia↗
PubMed2005

Anaesthetists' knowledge of the QT interval in a teaching hospital.

Many drugs used in anaesthesia may prolong the QT interval of the electrocardiogram (ECG), and recent U.S. Food and Drug Administration guidelines mandate monitoring of the ECG before, during and after droperidol administration. We surveyed 41 trainee and consultant anaesthetists in our Department to determine current practice and knowledge of the QT interval to investigate if this is a practical proposition. A response rate of 98% (40/41) was obtained. The majority of respondents expressed moderate to high levels of confidence in interpreting the ECG, and this was related to years of training (rho 0.36, P=0.024). A total of 27 respondents (65%) were able to correctly identify the QT interval on a schematic representation of the ECG, trainees 70% vs consultants 60%, P=0.51. When asked to name drugs that altered the QT interval, droperidol was included by 11 of the 40 respondents (28%); trainees 10% vs consultants 45%, OR 7.4 (95% CI: 1.3-41), P=0.013. Torsades de Pointes was correctly identified as a possible consequence of a prolonged QT interval by 65% of trainees and 70% of consultants, P=0.83. The results suggest that QT interval measurement is not widely practised by anaesthetists, although its clinical significance is well known, and interpretation would be unreliable without further education.

Adult↗
PubMed2004

Double-blind randomized controlled trial to determine extent of amnesia with midazolam given immediately before general anaesthesia.

BACKGROUND: Anterograde, but not retrograde, amnesia has been demonstrated following midazolam administration. However, there have been no studies investigating whether or not immediate retrograde amnesia can be produced with midazolam. METHODS: After ethics committee approval and consent, 40 adult patients undergoing surgery and general anaesthesia were randomly allocated to one of four groups: midazolam 2 mg, midazolam 5 mg, midazolam 10 mg or control (normal saline). Measurements were made from 12 min prior to induction of anaesthesia, and the study drug was administered 8 min prior to induction of anaesthesia. Midazolam effects were measured using visual recognition of posters, recall of specific events, bispectral index (BIS) and sedation visual analogue score. RESULTS: Recognition and recall rates were similar between groups up until the time of study drug administration, with no evidence of retrograde amnesia (all P>0.3). There was a dose-dependent deterioration in visual recall (P=0.002), event recollection (P<0.001), BIS (P<0.001) and sedation score (P<0.001) following i.v. midazolam when compared with control. CONCLUSIONS: We found no evidence that i.v. midazolam 2-10 mg produces immediate retrograde amnesia. Midazolam causes anterograde amnesia in a dose-responsive manner.

Adult↗
PubMed2004

Bispectral index monitoring to prevent awareness during anaesthesia: the B-Aware randomised controlled trial.

BACKGROUND: Awareness is an uncommon complication of anaesthesia, affecting 0.1-0.2% of all surgical patients. Bispectral index (BIS) monitoring measures the depth of anaesthesia and facilitates anaesthetic titration. In this trial we determined whether BIS-guided anaesthesia reduced the incidence of awareness during surgery in adults. METHODS: We did a prospective, randomised, double-blind, multicentre trial. Adult patients at high risk of awareness were randomly allocated to BIS-guided anaesthesia or routine care. Patients were assessed by a blinded observer for awareness at 2-6 h, 24-36 h, and 30 days after surgery. An independent committee, blinded to group identity, assessed every report of awareness. The primary outcome measure was confirmed awareness under anaesthesia at any time. FINDINGS: Of 2463 eligible and consenting patients, 1225 were assigned to the BIS group and 1238 to the routine care group. There were two reports of awareness in the BIS-guided group and 11 reports in the routine care group (p=0.022). BIS-guided anaesthesia reduced the risk of awareness by 82% (95% CI 17-98%). INTERPRETATION: BIS-guided anaesthesia reduces the risk of awareness in at-risk adult surgical patients undergoing relaxant general anaesthesia. With a cost of routine BIS monitoring at US16 dollars per use in Australia and a number needed to treat of 138, the cost of preventing one case of awareness in high-risk patients is about 2200 dollars.

Anesthesia Recovery Period↗
PubMed2004

Detection of cognitive decline after coronary surgery: a comparison of computerized and conventional tests.

BACKGROUND: Postoperative cognitive decline is a common complication after coronary artery bypass graft (CABG) surgery. Postoperative cognitive decline is defined on the basis of change in cognitive function detected with repeated assessments using neuropsychological tests. Therefore improvement in neuropsychological testing instruments may increase our understanding of postoperative cognitive decline. METHODS: Fifty patients undergoing CABG surgery completed both a conventional and a computerized battery of tests before and 6 days after CABG surgery. Fifty age- and education-matched controls completed the same test batteries 6 days apart. The reliability and the sensitivity to postoperative cognitive decline were computed for each battery. RESULTS: Both test batteries detected postoperative cognitive decline 6 days after CABG surgery. For the computerized battery, the reliability of the reaction times (intraclass correlation 0.89-0.92) was greater than for any test from the conventional battery (intraclass correlation 0.56-0.71), although accuracy measures were less reliable (intraclass correlation 0.61-0.89). The computerized battery detected all the cases of POCD identified by the conventional test battery and also five cases that were classified as normal by the conventional tests. CONCLUSION: Computerized tests are suitable for measuring cognitive change after CABG surgery and may detect change in a greater proportion of patients 6 days after CABG surgery than conventional neuropsychological tests.

Aged↗