Saliva cyclic GMP increases during anaesthesia

Background. Cyclic GMP (cGMP) has been implicated in modulatingthe effects of general anaesthesia. Changes in cGMP in humansundergoing anaesthesia have not been reported previously. Methods. In this pilot study we measured cGMP in the salivaof six healthy volunteers and eight patients undergoing generalanaesthesia for minor gynaecological procedures. Samples wereobtained using a commercially available sampling device andcGMP was determined with an enzyme immunoassay and results expressedas a cGMP per mg protein. Results. There was no statistically significant variation insalivary cGMP either day-to-day or between time points in healthyvolunteers. Analysis of variance of salivary cGMP of patientsundergoing general anaesthesia showed that cGMP increased significantlyintraoperatively and returned to preoperative levels after surgery(P=0.03). Conclusions. This is the first time that real time in vivo changesin salivary cGMP levels during general anaesthesia in humanshave been demonstrated and may allow an alternative techniquefor measuring depth of anaesthesia in the future. Br J Anaesth 2002; 89: 635–7     

Midlatency auditory evoked potentials in children: effect of age and general anaesthesia

BACKGROUND: Midlatency auditory evoked potentials (MLAEP) are a promising tool for monitoring suppression of sensory processing during anaesthesia and might help to avoid awareness. MLAEP in children are different to those in adults and the exact changes during general anaesthesia are unknown. METHODS: In 49 children of age between 2 and 12 yr, MLAEP were recorded before anaesthesia, during tracheal intubation, at steady-state balanced anaesthesia, and after extubation. RESULTS: MLAEP were recordable in all children in the awake (premedicated) state with latencies but not amplitudes dependent on children's age. MLAEP latencies significantly increased during tracheal intubation and steady-state anaesthesia. Changes in amplitudes were inconsistent. All MLAEP variables returned to near baseline values after extubation. CONCLUSIONS: The results of this study imply that MLAEP can successfully be recorded during anaesthesia in children above the age of 2 yr. Further studies are necessary before MLAEP might be applicable for monitoring purposes in paediatric anaesthesia.     

Assessment instruments used during anaesthetic simulation: review of published studies

This review was undertaken to discover what assessment instrumentshave been used as measures of performance during anaesthesiasimulation and whether their validity and reliability has beenestablished. The literature describing the assessment of performanceduring simulated anaesthesia amounted to 13 reports publishedbetween 1980 and 2000. Only four of these were designed to investigatethe validity or reliability of the assessment systems. We concludethat the efficacy of methodologies for assessment of performanceduring simulation is largely undetermined. The introductionof simulator-based tests for certification or re-certificationof anaesthetists would be premature. Br J Anaesth 2001; 86: 445–50     

Test of neural inertia in humans during general anaesthesia

Background

Neural inertia is defined as the tendency of the central nervous system to resist transitions between arousal states. This phenomenon has been observed in mice and Drosophila anaesthetized with volatile anaesthetics: the effect-site concentration required to induce anaesthesia in 50% of the population (C₅₀) was significantly higher than the effect-site concentration for 50% of the population to recover from anaesthesia. We evaluated this phenomenon in humans using propofol or sevoflurane (both with or without remifentanil) as anaesthetic agents.

Medical aerosol propellant interference with infrared anaesthetic gas monitors

Background. 1,1,1,2 Tetrafluoroethane is a hydrofluoroalkane(HFA) that is replacing chlorofluorocarbons (CFC) as a medicalaerosol propellant in an attempt to reduce damage to the ozonelayer. This study compared the effects of HFA- and CFC-basedinhalers on four anaesthetic gas monitoring systems. Methods. The HFA- and CFC-based inhalers were activated in closeproximity to the sample line of two Datex Ohmeda, an Agilentand a Siemens infrared anaesthetic agent monitoring systems.The effects were recorded on each system for five common anaestheticagents. Results. The HFA inhaler caused either maximal false positivereadings (with the exception of desflurane) or transient measurementfailure on all systems. The Datex Ohmeda AS/3 system misidentifiedthe HFA inhaler as carbon dioxide at low concentration (2 ±0 mm Hg). The CFC-based inhaler caused a minor false-positivereading (0.4 ± 0%) for halothane only on the Datex OhmedaAS/3 system only and was misidentified as carbon dioxide at33.3 (SD 2.1) mm Hg and 22.4 (8.9) mm Hg by the Agilent andSiemens systems. Conclusions. The HFA inhaler adversely affected all equipmenttested. The infrared spectra of HFA and the common anaestheticgases have considerable overlap at the 8–12 µm rangethat is not shared by the CFCs. The differences in spectraloverlap explain the different effects of the HFA and CFC propellants.Anaesthetic gas concentration data may be erroneous using theHFA-based inhalers. Br J Anaesth 2004; 92: 865–9     

Patient satisfaction with anaesthesia care: development of a psychometric questionnaire and benchmarking among six hospitals in Switzerland and Austria

Background. We describe the development and comparison of apsychometric questionnaire on patient satisfaction with anaesthesiacare among six hospitals. Methods. We used a rigorous protocol: generation of items, constructionof the pilot questionnaire, pilot study, statistical analysis(construct validity, factor analysis, reliability analysis),compilation of the final questionnaire, main study, repeatedanalysis of construct validity and reliability. We comparedthe mean total problem score and the scores for the dimensions:‘Information/Involvement in decision-making’, and‘Continuity of personal care by anaesthetist’. Theinfluence of potential confounding variables was tested (multiplelinear regression). Results. The average problem score from all hospitals was 18.6%.Most problems are mentioned in the dimensions ‘Information/Involvementin decision-making’ (mean problem score: 30.9%) and ‘Continuityof personal care by anaesthetist’ (mean problem score:32.2%). The overall assessment of the quality of anaesthesiacare was good to excellent in 98.7% of cases. The most importantdimension was ‘Information/Involvement in decision-making’.The mean total problem score was significantly lower for twohospitals than the total mean for all hospitals (significantlyhigher at two hospitals) (P<0.05). Amongst the confoundingvariables considered, age, sex, subjective state of health,type of anaesthesia and level of education had an influenceon the total problem score and the two dimensions mentioned.There were only marginal differences with and without the influenceof the confounding variables for the different hospitals. Conclusions. A psychometric questionnaire on patient satisfactionwith anaesthesia care must cover areas such as patient information,involvement in decision-making, and contact with the anaesthetist.The assessment using summed scores for dimensions is more informativethan a global summed rating. There were significant differencesbetween hospitals. Moreover, the high problem scores indicatea great potential for improvement at all hospitals. Br J Anaesth 2002; 89: 863–72     

Intercurrent drug therapy and perioperative cardiovascular mortality in elective and urgent/emergency surgical patientst

The Oxford Record Linkage Study (ORLS; an epidemiological database)was used to examine relationships between intercurrent cardiovasculardrug therapy and cardiac death within 30 days of electiveor emergency/urgent surgery under general anaesthesia. Casesidentified from the ORLS were paired with matched control patients.Clinical details were obtained from the patients’ medicalnotes. In elective surgical patients, there was no effect ofß-adrenoceptor or calcium entry channel blockade,diuretics or digoxin on cardiac death after adjusting for confoundingvariables. Use of nitrates was associated with an odds ratioof 4.79 [95% confidence interval (CI) 1.01–22.72] forcardiac death after adjustment for confounding by a historyof angina and residual age difference. In emergency/urgent patients,there were significant univariate associations with cardiacdeath for intercurrent use of angiotensin converting enzyme(ACE) inhibitors (odds ratio 1.18) and diuretics (odds ratio4.95; 95% CI 1.82–13.46). However, neither maintainedsignificance after adjustment for the confounding effect ofcardiac failure. We conclude that, with the possible exceptionof the use of nitrates in elective surgical patients, chronicintercurrent drug treatment alone does not significantly affectthe odds of cardiac death within 30 days of surgery. Br J Anaesth 2001; 86: 506–12     

Use of conventional ECG electrodes for depth of anaesthesia monitoring using the cerebral state index: a clinical study in day surgery

Background: The cost–benefit relationship for depth of anaesthesiamonitors is complicated by the high cost of specially designedEEG electrodes. The cerebral state index (CSI) monitor willaccept regular ECG electrodes with snap connectors. The purposeof this study was to determine if generic ECG electrodes couldreplace the more expensive proprietary EEG electrodes for theCSI monitor. Methods: Two identical cerebral state monitors were used simultaneouslyduring sevoflurane anaesthesia for knee arthroscopy in 14 ASAI–II patients. One monitor used proprietary (Danmeter)EEG electrodes and the other used ECG electrodes (3M^TM Red Dot^TMDiagnostic ECG Electrodes). Paired CSI values were recordedevery other minute. Anaesthetic depth was titrated clinically.Sedation depth was scored according to the Observer's Assessmentof Alertness/Sedation (OAAS) scale. Results: The agreement between the two measures was found to be high,mean difference – 0.23, and the overall repeatabilitymean bias was 6.6 and 153/163 pairs (94%) were located withinthe 95% limits of agreement. No major difference was noted inimpedance, noise, or artifacts. A large overlap in CSI was notedfor each level of the OAAS scale; patients with CSI values aslow as 40–50 responded whereas patients not respondingto surgical stimulation had CSI values as high as 75. The directcost of disposables decreased from 4 to 0.50 per patient byusing ordinary ECG electrodes. Conclusions: Switching from proprietary EEG electrodes to ordinary genericECG electrodes maintains the same accuracy at about a 10th ofthe cost when measuring CSI during day surgery with sevofluraneanaesthesia.     

Haematoma and abscess after neuraxial anaesthesia: a review of 647 cases

Although rare, spinal haematoma and abscess after central neuraxial blocks may cause severe permanent neurological injury. Optimal treatment and outcome remain unclear. In order to identify possible predisposing patient characteristics and describe the ensuing clinical course, we searched Medline, Embase, and the Cochrane Library for reports of spinal haematomas and abscesses associated with central neuraxial blocks. Extracted data included patient characteristics, symptoms, treatment, and outcome. We analysed 409 reports, including 647 patients (387 patients with spinal haematoma and 260 patients with spinal abscess). Spinal haematoma and abscess occurred predominantly after epidural anaesthesia (58% and 83%, respectively). Neurological recovery was correlated with the severity of initial neurological deficit. When decompression of spinal haematoma was delayed for >12 h after clinical diagnosis, neurological outcome was worse compared with earlier decompression (odds ratio 4.5, 95% confidence interval 2.1–9.9, P<0.001, n=163). After spinal haematoma, 47% of published patients had full recovery, 28% had partial recovery, and in 25% no recovery was observed. Good outcome after conservative management was observed in patients with mild symptoms or with spontaneous recovery during the diagnostic and therapeutic workup. After spinal abscess, 68% of reported patients recovered fully, 21% showed partial recovery, and no recovery was reported in 11%. Persistent neurological symptoms after spinal haematoma and abscess are common and correlate with the severity of initial neurological deficit. Neurological outcome seems worse when decompressive surgery of haematoma is delayed. Notwithstanding the considerable risk of selection bias and publication bias, conservative management may be feasible in patients with mild symptoms or spontaneous recovery.     

Haemodynamic effects of oxytocin given as i.v. bolus or infusion on women undergoing Caesarean section

Background. The cardiovascular effects of oxytocin in animalmodels and women undergoing Caesarean section include tachycardia,hypotension and decrease in cardiac output. These can be sufficientto cause significant compromise in high-risk patients. We aimedto find a simple way to decrease these risks whilst retainingthe benefits of oxytocin in decreasing bleeding after delivery. Method. We recruited 30 women undergoing elective Caesareansection. They were randomly allocated to receive 5 u of oxytocineither as a bolus injection (bolus group) or an infusion over5 min (infusion group). These women had their heart rate andintra-arterial blood pressure recorded every 5 s throughoutthe procedure. The haemodynamic data, along with the estimatedblood loss, were compared between the groups. Results. Marked cardiovascular changes occurred in the bolusgroup; the heart rate increased by 17 (10.7) beats min^–1[mean (SD)] compared with 10 (9.7) beats min^–1 in theinfusion group. The mean arterial pressure decreased by 27 (7.6)mm Hg in the bolus group compared with 8 (8.7) mm Hg in theinfusion group. There were no differences in the estimated bloodloss between the two groups. Conclusion. We recommend that bolus doses should be used withcaution, and further studies should ascertain if oxytocin isequally effective in reducing blood loss when given at a slowerrate.     

Lobectomy for cavitating lung abscess with haemoptysis: strategy for protecting the contralateral lung and also the non-involved lobe of the ipsilateral lung

We describe the anaesthetic management of a patient undergoinglobectomy for cavitating lung abscess complicated by haemoptysis.Surgery for lung abscess is one of the absolute indicationsfor the use of a double-lumen tube (DLT). Because pus or bloodcould impede fibreoptic- assisted DLT placement, a traditional,blind placement of the DLT was performed. To protect the uninvolvedparts of the operated lung, ventilation of the lung with theabscess was not performed until the resection of the involvedlobe had been completed. Br J Anaesth 2000; 85: 791–4 ^* Corresponding author     

Anaesthesia chapter from Saving mothers' lives; reviewing maternal deaths to make pregnancy safer

This chapter concerning maternal mortality due to anaesthesia, reprinted with permission from Saving Mothers' Lives, is the 18th in a series of reports within the Confidential Enquiries into Maternal and Child Health (CEMACH) in the UK. In the years 2003-05 there were six women who died from problems directly related to anaesthesia, which is the same as the 2000-02 triennium. Obesity was a factor in four of these women who died. Two of these deaths were in women in early pregnancy, who received general anaesthesia for gynaecological surgery by inexperienced anaesthetists who failed to manage the airway and ventilation adequately. When trainee anaesthetists are relatively inexperienced their consultants must know the limits of their competence and when close supervision and help may be needed. One death was due to bupivacaine toxicity due to a drug administration error when a bag of dilute local anaesthetic was thought to be intravenous fluid. In a further 31 cases poor perioperative management may have contributed to death. Obesity was again a relevant factor. Other cases could be categorized into poor recognition of women being sick and poor clinical management of haemorrhage, sepsis and of pre-eclampsia. Early warning scores of vital signs may help identify the mother who is seriously ill. Learning points are highlighted in relation to the clinical management of these obstetric complications.     

Setting priorities for improving the preoperative assessment clinic: the patients' and the professionals' perspective

BACKGROUND: The quality of the preoperative assessment clinic (PAC) is determined by many factors. Patients' experiences are important indicators, but often overlooked. We prepare to set priorities to improve the PAC by obtaining detailed patients' feedback on the quality of the PAC, and establishing the value patients and professionals attach to different care aspects, using the Patient Experiences with the Preoperative Assessment Clinic questionnaire. METHODS: The PAC's standard of service was determined for five care aspects (dimensions), using patients' feedback. The importance of a dimension to patients was determined by calculating the effects of the dimensions on patients' overall appraisal. In addition, professionals were asked to rate the importance of the different care aspects. RESULTS: Patients had the most positive experiences with the nurse, and the least positive experiences with waiting. However, waiting was least important to patients. When combining the PAC's standard of service with the value given to the dimensions by patients and professionals separately, we found in both instances that waiting was in greatest need of improvement. This was followed by reception, the anaesthetist, remaining experiences, and finally the nurse. CONCLUSIONS: Quality improvement of the PAC can be achieved by obtaining patients' feedback on the quality, determine a PAC's standard of service, recognize service areas that require improvement, and identify actions appropriate to bring about improvement. The value patients and professionals attach to different aspects of care can then be used to prioritize improvements.     

Spinal or general anaesthesia for surgical repair of hip fracture and subsequent risk of mortality and morbidity: a database analysis using propensity score-matching

Around 76,000 people fracture their hip annually in the UK at a considerable personal, social and financial cost. Despite longstanding debate, the optimal mode of anaesthesia (general or spinal) remains unclear. Our aim was to assess whether there is a significant difference in mortality and morbidity between patients undergoing spinal anaesthesia compared with general anaesthesia during hip fracture surgery. A secondary analysis examined whether a difference exists in mortality for patients with pre-existing cardiovascular disease or chronic obstructive pulmonary disease. This was a clinical database analysis of patients treated for hip fracture in Nottingham, UK between 2004 and 2015. Propensity score-matching was used to generate matched pairs of patients, one of whom underwent each mode of anaesthesia. Data were analysed using conditional logistic regression, with 7164 patients successfully matched. There was no difference in 30- or 90-day mortality in patients who had spinal rather than general anaesthesia (OR [95%CI] 0.97 [0.8–1.15]; p = 0.764 and 0.93 [0.82–1.05]; p = 0.247 respectively). Patients who had a spinal anaesthetic had a lower-risk of blood transfusion (OR [95%CI] 0.84 [0.75–0.94]; p = 0.003) and urinary tract infection (OR [95%CI] 0.72 [0.61–0.84]; p < 0.001), but were more likely to develop a chest infection (OR [95%CI] 1.23 [1.07–1.42]; p = 0.004), deep vein thrombosis (OR [95%CI] 2.18 [1.07–4.45]; p = 0.032) or pulmonary embolism (OR [95%CI] 2.23 [1.16–4.29]; p = 0.016). The mode of anaesthesia for hip fracture surgery resulted in no significant difference in mortality, but there was a significant difference in several measures of postoperative morbidity.     

Patient Experiences with the Preoperative Assessment Clinic (PEPAC): validation of an instrument to measure patient experiences

BACKGROUND: Presently, no comprehensive and validated questionnaire to measure patient experiences of the preoperative assessment clinic (PAC) is available. We developed and validated the Patient Experiences with the Preoperative Assessment Clinic (PEPAC) questionnaire, which can be used for quantitative measurements of patient experiences of the PAC. METHODS: We adapted the National Health Service outpatient questionnaire, incorporating questions specific for anaesthesiology. To make the PEPAC appropriate for quantitative measurements, dimensions and single items suitable for statistical analysis were constructed. Each dimension consists of multiple items measuring the same aspect of care. Reliability was established by computing Cronbach's alpha coefficients. Construct validity was assessed by correlating the dimensions with the patient's overall appraisal (Pearson's r). These dimensions should explain a substantial level of variance of the patients' overall appraisal; therefore, regression analysis was performed. RESULTS: After a pilot phase, the questionnaire was sent to 700 consecutive patients (response 74%). Five scales measuring five dimensions of patient experiences were constructed. Cronbach's alpha ranged from 0.56 to 0.84, supporting reliability of the PEPAC. Correlations between the dimensions and patients' overall appraisal ranged from 0.22 to 0.56. Collectively, the five scales explained 51% of patients' overall appraisal. CONCLUSIONS: The PEPAC is a comprehensive, reliable, and validated questionnaire to measure patient experiences with the PAC. It might be a useful tool to identify the service areas of the PAC that require improvement and to determine which actions can bring about improvement.     

Efficacy of augmentation of epidural analgesia for Caesarean section

Background. Extension of a labour epidural for Caesarean deliveryis thought to be successful in most cases and avoids the useof general anaesthesia. However, most previous studies thathave estimated the failure rate of pre-existing epidural catheterswere performed in small numbers of patients. Methods. Therefore, we undertook to retrospectively measurethe failure rate of indwelling epidural catheters in a largenumber of patients. Results. The anaesthetic team was available at all times andwas permanently led by a senior anaesthetist specialized inobstetrics. Extension was performed using lidocaine 2% withepinephrine (mean 18 (SD 6) ml), combined in most patients withsufentanil (9 (2.2) µg) and/or clonidine (75 µg).Among 194 consecutive extensions performed in a 1-yr period,general anaesthesia was required in five patients (2.6%) whilesedation and/or i.v. analgesia were used in 27 patients (13.9%).In three cases where general anaesthesia was required, the intervalbetween decision to incision was <10 min. No factorassociated with failure could be identified. Addition of a lipophilicopioid or of clonidine did not modify the efficacy of the block(i.e. general anaesthesia or supplementation were required ina similar proportion). Conclusions. The augmentation of labour epidurals for Caesareansection using lidocaine 2% plus epinephrine is a reliable andeffective technique. No factor associated with failure couldbe identified. Br J Anaesth 2003; 91: 532–5     

Non-fatal amniotic fluid embolism after cervical suture removal

We describe a case of pulmonary oedema occurring at 37 weeksgestation, following the attempted removal of a cervical sutureunder general anaesthesia. The use of an ultrasound techniqueto demonstrate the patient’s fluid status is described.Signs of amniotic fluid embolism and how it exerts its influenceon the circulation are discussed. Br J Anaesth 2003; 90: 244–7     

Expertise in practice: an ethnographic study exploring acquisition and use of knowledge in anaesthesia

Background. Expert professional practice in any field is knownto rely on both explicit (formal) and tacit (personal) formsof knowledge. Current anaesthetic training programmes appearto favour explicit knowledge and measurable competencies. Weaimed to describe and explore the way different types of knowledgeare learned and used in anaesthetic practice. Method. Qualitative approach using non-participant observationof, and semi-structured interviews with, anaesthetic staff intwo English hospitals. Results. The development of expertise in anaesthesia rests onthe ability to reconcile and interpret many sources of knowledge—clinical,social, electronic, and experiential—and formal theoreticallearning. Experts have mastered technical skills but are alsoable to understand the dynamic and uncertain condition of theanaesthetized patient and respond to changes in it. This expertiseis acquired by working with colleagues, and, importantly, byworking independently, to develop personal routines. Routinesmark the successful incorporation of new knowledge but alsofunction as a defence against the inherent uncertainty of anaestheticpractice. The habits seen in experts’ routines are preferredways of working chosen from a larger repertoire of techniqueswhich can also be mobilized as changing circumstances demand. Conclusions. Opportunities for developing expertise are linkedto the independent development of personal routines. Evidence-basedapproaches to professional practice may obscure the role playedby the interpretation of knowledge. We suggest that the restrictionof apprenticeship-style training threatens the acquisition ofanaesthetic expertise as defined in this paper. Br J Anaesth 2003; 91: 319–28     

Effects of protein binding on the placental transfer of propofol in the human dually perfused cotyledon in vitro

The placental transfer of propofol was investigated using thein vitro dually perfused cotyledon model of the human placenta,and the effects of protein binding in the foetal perfusate wereexamined. Both maternal and foetal circulations were perfusedin a single-pass mode and >30 min of stabilization was allowedbefore adding propofol and antipyrine to the maternal perfusate.The placental clearances of propofol were significantly increasedby the augmented albumin concentrations in the foetal perfusate(1.68 (SD 0.68), 3.08 (1.55), 4.79 (1.76), 5.75 (1.89) and 7.03(1.46) ml h^–1 g^–1 at the albumin concentrationsof 4.4, 11, 22, 33 and 44 g litre^–1, respectively).Although the total propofol concentration in the foetal veinincreased significantly with increasing albumin concentration,the concentration of free propofol remained unchanged. Theseresults indicate that binding to foetal albumin is a determiningfeature in the control of the placental transfer of propofol,and that the pharmacological effects of propofol on the foetuscan be expected to be fairly constant and predictable from thematernal propofol concentration. Br J Anaesth 2000; 84: 281–6 ^* Corresponding author     

Memory priming during light anaesthesia with desflurane and remifentanil anaesthesia

Background: Previous studies of memory priming during anaesthesia with EEGmonitoring have observed implicit memory effects for words presentedduring light and deep anaesthesia with and without surgicalstimulation. We hypothesized that memory priming occurs undereach of five different combinations of anaesthesia and surgery,and no significant differences occur in memory priming amongthe five conditions or between the two test points such as,12 vs 24 h after surgery. Methods: Forty gynaecological patients (aged between 28 and 66 yr, median44.5 yr) were included in the study. They received propofoland remifentanil induction followed by desflurane and remifentanilanaesthesia in conjunction with neuromuscular blocking agents.Each patient was exposed to 60 of 120 nouns in a double-blindrandomized design. These 60 nouns were divided into 5 groupsof 12 words, presented under one of the five different conditions,namely, intubation, skin incision, deep anaesthesia and moderateanaesthesia (both during surgery), and light anaesthesia duringthe emergence phase. The depth of anaesthesia was measured usingthe EEG monitor, Narcotrend^TM. Results: No explicit memories were observed in a free recall or in ayes–no recognition test. A word-stem completion test revealeda significant implicit priming only for light anaesthesia (P< 0.01). No significant differences were detected among thefive conditions. An overall implicit memory effect occurredfor the second test point (P < 0.05). Conclusions: Our hypotheses could not be verified. Implicit memory primingoccurred only under light anaesthesia, when the patients weremost probably conscious. Priming effects may be enhanced afternight's sleep.