S. M. Yentis

The Pharmacology of Sevoflurane in Infants and Children

Background:Sevoflurane is a new volatile anesthetic with physical properties that should make it suitable for anesthesia in children. In this study, the minimum alveolar concentration (MAC) of sevoflurane in oxygen alone and in 60% nitrous oxide, the hemodynamic, induction and emergence responses to sevoflurane and the metabolism to inorganic fluoride were studied in 90 ASA physical status 1 or 2 neonates, infants, and children. Methods:MAC of sevoflurane in oxygen was determined in six groups of subjects stratified according to age: full-term neonates, infants 1-6 and > 6-12 months and children > 1- 3, > 3-5 and > 5-12 yr. MAC in 60% nitrous oxide was determined in a separate group of children 1-3 yr of age. After an inhalational induction, the trachea was intubated (except for neonates in whom an awake intubation was performed). MAC for each age group was determined using the Up-and-Down technique of Dixon. Results:MAC of sevoflurane in neonates, 3.3 ± 0.2% and in infants 1-6 months of age, 3.2 ± 0.1%, were similar; MAC in older infants 6-12 months and children 1-12 yr was constant at ≈ 2.5%; MAC of sevoflurane in 60% nitrous oxide in children 1-3 yr of age was 2.0 ± 0.2%. Systolic arterial pressure decreased significantly at 1 MAC before skin incision compared with awake values in all subjects except children 1-3 yr with 60% nitrous oxide and children 5-12 yr in oxygen, and then returned toward awake values after skin incision. Heart rate was unchanged at ≈ 1 MAC sevoflurane before incision compared with awake values in all subjects except children > 3-5 and > 5-12 yr in whom heart rate increased before incision. Induction of anesthesia, particularly with respect to airway irritability, and emergence from sevoflurane anesthesia were not remarkable. The plasma concentration of inorganic fluoride reached maximum values (8.8-16.7 µM) 30 min after discontinuation of anesthesia. Conclusions:We conclude that sevoflurane appears to be a suitable anesthetic agent for use in neonates, infants and children undergoing ≤ 1 h of anesthesia.

Pregnancy and congenital heart disease

Congenital heart disease occurs in 0.8% of newborn infants around the world. Advances in medical and surgical treatments over the past decades has led to more than 85% of these infants surviving to adulthood.1 2 Most interventions, however, have not been curative and about half of adults with congenital heart disease face the prospect of further surgery, arrhythmia, heart failure, and—if managed inappropriately—premature death. The burden of pregnancy represents a new challenge in women with congenital heart disease. In the United Kingdom about 250 000 adults have congenital heart disease (also known as “grown up congenital heart disease (GUCH)” patients), and this number is growing.3 Half of these patients are women, most of reproductive age. After suicide, cardiac disease is now the leading cause of maternal death in the UK, with most of these casualties having had congenital heart disease.4 The medical profession should therefore be aware of the risks that women with congenital heart disease face during pregnancy so that they can be given adequate preconception counselling and optimal care during pregnancy, delivery, and the postpartum period.5–7 Discussions about future pregnancies, family planning, and contraception should begin in adolescence to prevent accidental and potentially dangerous pregnancies in women with congenital heart disease. The impact of heart disease on childbearing potential needs to be explained clearly and sympathetically. Counselling has to address how pregnancy may affect not just the mother but also the fetus and the rest of the family (box 1). This allows women to make an informed choice whether they wish to accept the risks associated with pregnancy. The counselling should ideally be provided in a joint clinic by an obstetrician with expertise in heart disease and a cardiologist with special training in adult congenital heart disease. ### The risk for the mother The risk for pregnant women …

The effect of neuromuscular blockade on the efficiency of mask ventilation of the lungs.

Summary We conducted a two‐part study to assess the practice of withholding neuromuscular blockade until the ability to ventilate the lungs using a bag and face mask (mask ventilation) has been established following induction of anaesthesia. The first part of the study consisted of a postal survey (71% response rate) of 188 anaesthetists in the Oxford region to assess their current practice. Thirty per cent of respondents always checked mask ventilation before administering a neuromuscular blocking drug, whereas 39% of respondents (all them consultants) never did this. A further 31% only did so in the case of known or anticipated difficulty with the airway. In the second part of the study, we measured inspired (VTI) and expired (VTE) tidal volumes before and after neuromuscular blockade in 30 patients undergoing general anaesthesia. The ratio VTE/VTI was used as a measure of the efficiency of ventilation. There was no difference in VTE/VTI before [mean (SD) 0.47 (0.13)] and after [0.45 (0.13)] neuromuscular blockade. We conclude that neuromuscular blockade does not affect the efficiency of mask ventilation in patients with normal airways.

Effect of pregnancy on clinical status and ventricular function in women with heart disease

BACKGROUND Pregnant women with heart disease (HD) are at an increased risk for maternal and neonatal adverse events. However, the effect of pregnancy on clinical status and ventricular function in women with HD has not been examined in a controlled study. METHODS AND RESULTS Ninety-three women with HD were studied longitudinally. Of these, fifty-three underwent clinical and echocardiographic evaluation before and 1.5+/-1.1 years after pregnancy (pregnancy group), whereas forty served as controls matched for age (28.6+/-4.6 versus 28.5+/-6.6, p=0.88), diagnosis, and length of follow-up (2.9+/-1.4 versus 2.6+/-1.1, p=0.23). NYHA functional class remained unchanged in both groups during follow-up. End diastolic and end systolic dimensions and shortening fraction of the morphologic left ventricle also remained unchanged. Furthermore, systemic and subpulmonary ventricular function remained unchanged in the pregnancy and control groups on semiquantitative analysis. Pregnancy, however, was associated with a persisting increase in subpulmonary ventricular size in patients with tetralogy of Fallot (ToF) which was not present in tetralogy controls. Furthermore, diagnosis of ToF was the only predictor of an increase in subpulmonary ventricular size after pregnancy on univariate logistic regression analysis (OR 8.8[95% CI 1.9-41.1], p=0.006). CONCLUSIONS In this longitudinal controlled study amongst women with HD no deleterious midterm effects of pregnancy on clinical status and right and left ventricular function were found. However, pregnancy was associated with a persisting increase in subpulmonary ventricular size, attributable to patients with repaired ToF. This may have prognostic implications and merits further investigation.

Intra-operative fluid warming in elective caesarean section: a blinded randomised controlled trial.

BACKGROUND We assessed the effect of warming intravenous fluids during elective caesarean section under combined spinal-epidural anaesthesia in a blinded, randomised controlled trial. METHOD Seventy-five women having elective caesarean section were randomly assigned to receive all intravenous fluids at room temperature, or heated in a cabinet set at 45 degrees C or via a Hotline fluid warmer (Smiths Medical International Ltd, Watford, Herts, UK). After 10 mL/kg crystalloid preload, combined spinal-epidural anaesthesia was performed. Core and ambient temperatures, thermal comfort and shivering were measured every 15 min thereafter. The primary outcome was the temperature at 60 min. RESULTS Temperature decreased in all groups. Although the temperature decrease at 60 min was similar in the heated cabinet and Hotline groups, the room temperature group exhibited a greater decrease [difference 0.4 degrees C (95% CI 0.2-0.6 degrees C); P=0.015]. More women felt cold in the room temperature group (8: 32%) than in the heated cabinet set (3: 12%) and Hotline (1: 4%) groups (P=0.02), but the incidence of shivering was similar: 11 (44%), 9 (36%) and 7 (28%) respectively. Apgar scores and neonatal cord gases were similar. CONCLUSION Warming intravenous fluids mitigates the decrease in maternal temperature during elective caesarean section under combined spinal-epidural anaesthesia and improves thermal comfort, but does not affect shivering. Intravenous fluids should be warmed routinely in elective caesarean section, especially for cases of expected long duration, but the use of pre-warmed fluids is as efficient and cheaper than using a Hotline fluid warmer.

Use of the bougie in simulated difficult intubation. 2. Comparison of single-use bougie with multiple-use bougie*

Summary We studied the success rates for tracheal intubation in 32 healthy, anaesthetised patients during simulated grade IIIa laryngoscopy, randomised to either the multiple‐use or the single‐use bougie. Success rates (primary end‐point) and times taken (secondary end‐point) to achieve tracheal intubation were recorded. The multiple‐use bougie was more successful than the single‐use one (15/16 successful intubations vs. 9/16; p = 0.03). With either device, median [range] total tracheal intubation times for successful attempts were < 54 [24–84] s and there were no clinically important differences between these times. We conclude that the multiple‐use bougie is a more reliable aid to tracheal intubation than the single‐use introducer in grade IIIa laryngoscopy.

A national survey of obstetric anaesthetic handovers

The handover of patient information between shifts enables continuity of care and increases patient safety. We surveyed UK practice during handovers in obstetric anaesthesia. A questionnaire was sent to 239 lead consultant obstetric anaesthetists to record routine practice in their unit and individual opinion about handover procedures. Responses were received from 168 anaesthetists, a 70% response rate. Handover policies were available in 10% of units. Most (76%) responding units had an allocated time for handover. In most units (76%), the duration of handover was reported as being < 15 min but the actual duration and depth of any discussion involved were not specified. Handovers were rarely documented in writing (7%). Consultant anaesthetists were most likely to be present at the morning handover and few handovers were multidisciplinary. Four percent of units reported critical incidents following inadequate handovers in the past 12 months. We identify features in handover procedures that could be improved.

Calculating the probability of random sampling for continuous variables in submitted or published randomised controlled trials.

In a previous paper, one of the authors (JBC) used a chi‐squared method to analyse the means (SD) of baseline variables, such as height or weight, from randomised controlled trials by Fujii et al., concluding that the probabilities that the reported distributions arose by chance were infinitesimally small. Subsequent testing of that chi‐squared method, using simulation, suggested that the method was incorrect. This paper corrects the chi‐squared method and tests its performance and the performance of Monte Carlo simulations and ANOVA to analyse the probability of random sampling. The corrected chi‐squared method and ANOVA method became inaccurate when applied to means that were reported imprecisely. Monte Carlo simulations confirmed that baseline data from 158 randomised controlled trials by Fujii et al. were different to those from 329 trials published by other authors and that the distribution of Fujii et al.s data were different to the expected distribution, both p < 10−16. The number of Fujii randomised controlled trials with unlikely distributions was less with Monte Carlo simulation than with the 2012 chi‐squared method: 102 vs 117 trials with p < 0.05; 60 vs 86 for p < 0.01; 30 vs 56 for p < 0.001; and 12 vs 24 for p < 0.00001, respectively. The Monte Carlo analysis nevertheless confirmed the original conclusion that the distribution of the data presented by Fujii et al. was extremely unlikely to have arisen from observed data. The Monte Carlo analysis may be an appropriate screening tool to check for non‐random (i.e. unreliable) data in randomised controlled trials submitted to journals.

Epidural lidocaine-bicarbonate-adrenaline vs levobupivacaine for emergency Caesarean section: a randomised controlled trial*

Epidural mixtures containing lidocaine with or without additives are commonly used to convert epidural analgesia in labour to anaesthesia for emergency Caesarean section, but direct comparisons with alternative, single agents in this situation are few. In a prospective double‐blinded trial, we compared a freshly prepared lidocaine‐bicarbonate‐adrenaline mixture (final concentrations 1.8%, 0.76% and 1 : 200,000, respectively) with our standard agent, levobupivacaine 0.5%, for extending epidural blockade for emergency Caesarean section. Using a sequential analysis technique, with data analysed in blocks of 40, women receiving epidural analgesia in labour who required top‐up for Caesarean section were randomly assigned to receive 20 ml of epidural solution over 3 min. The first analysis (n = 40) indicated that the study should be stopped, as significant differences were found in our primary outcome data. Median (IQR [range]) times to reach a block to touch to T5 and cold to T4 were, respectively, 7 (6–9 [5–17]) min and 7 (5–8 [4–17]) min for lidocaine‐bicarbonate‐adrenaline, and 14 (10 −17 [9–31]) min and 11 (9–14 [6–30]) min for levobupivacaine (p = 0.00004 and 0.001, respectively). Pre‐ and intra‐operative supplementation/pain, maternal side‐effects and neonatal outcomes (excluding five women who underwent instrumental delivery) were similar between the groups. Intra‐operative maternal sedation (scored by the mother on a 10‐point scale) was greater with lidocaine‐bicarbonate‐adrenaline (4.5 (3–8 [1–9])) than with levobupivacaine (3 (1–4 [1–7])), but not significantly so (p = 0.07). We conclude that epidural lidocaine‐bicarbonate‐adrenaline halves the onset time when extending epidural analgesia for Caesarean section although there is a possibility of increased maternal sedation.

AAGBI: Consent for anaesthesia 2017: Association of Anaesthetists of Great Britain and Ireland

Previous guidelines on consent for anaesthesia were issued by the Association of Anaesthetists of Great Britain and Ireland in 1999 and revised in 2006. The following guidelines have been produced in response to the changing ethical and legal background against which anaesthetists, and also intensivists and pain specialists, currently work, while retaining the key principles of respect for patients’ autonomy and the need to provide adequate information. The main points of difference between the relevant legal frameworks in England and Wales and Scotland, Northern Ireland and the Republic of Ireland are also highlighted.