Inhalational or total intravenous anaesthesia: is total intravenous anaesthesia useful and are there economic benefits?

PURPOSE OF REVIEW: The comparison of inhalational and intravenous anaesthesia has been the subject of many controlled trials and meta-analyses. These reported diverse endpoints typically including measures of the speed and quality of induction of anaesthesia, haemodynamic changes, operating conditions, various measures of awakening, postoperative nausea and vomiting and discharge from the recovery area and from hospital as well as recovery of psychomotor function. In a more patient-focused Health Service, measures with greater credibility are overall patient satisfaction, time to return to work and long-term morbidity and mortality. In practice, studies using easier to measure proxy endpoints dominate - even though the limitations of such research are well known. RECENT FINDINGS: Recent study endpoints are more ambitious and include impact on survival from cancer and the possibility of differential neurotoxic impact on the developing brain and implications for neuro-behavioural performance. SUMMARY: Economic analysis of anaesthesia is complex and most published studies are naive, focusing on drug acquisition costs and facility timings, real health economics are much more difficult. Preferred outcome measures would be whole institution costs or the ability to reliably add an extra case to an operating list, close an operating room and reduce the number of operating sessions offered or permanently decrease staffing. Alongside this, however, potential long-term patient outcomes should be considered

Propofol and children--what we know and what we do not know.

The pharmacokinetics of propofol are relatively well described in the pediatric population. Recent work has confirmed the validity of allometric scaling for predicting propofol disposition across different species and for describing pediatric ontogenesis. In the first year of life, allometric models require adjustment to reflect ontogeny of maturation. Pharmacodynamic data for propofol in children are scarcer, because of practical difficulties in data collection and the limitations of currently available depth of anesthesia monitors for pediatric use. Hence, questions relating to the comparative sensitivity of children to propofol, and differences in time to peak effect relative to adults, remain unanswered. K(eo) half-lives have been determined for pediatric kinetic models using time to peak effect techniques but are not currently incorporated into commercially available target-controlled infusion pumps

Depth-of-anaesthesia monitoring

All anaesthetists would like to be confident that their patients are asleep throughout surgery. Depth-of-anaesthesia monitors may contribute to reducing the incidence of perioperative awareness, but they are expensive, and typically require that consumables are purchased for every case.Recently, excessive depth of anaesthesia has been feebly associated with increased mortality, but this has not yet been proven, and may reflect patient co-morbidity, rather than clinician error

Response to Serrao and Goodchild

doi: 10.1016/j.bja.2018.01.00

Quest for new drugs: a way to solve anaesthesia neurotoxicity?

doi: 10.1016/j.bja.2018.01.02

Hypotension during propofol sedation for colonoscopy – an exploratory analysis

Background. Intraoperative and post-operative hypotension occur commonly and are associated with organ injury and poor outcomes. Changes in blood pressure during procedural sedation are not well described. Methods. Individual patient data from five trials of propofol sedation for colonoscopy and a clinical database were pooled and explored with logistic and linear regression. A literature search and focussed meta-analysis compared the incidence of hypotension with propofol and alternative forms of procedural sedation. Hypotensive episodes were characterised by the original authors’ definitions, typically systolic blood pressure 5 minutes and in 89 (23%) the episodes exceeded 10 minutes. Meta-analysis of eighteen Randomised Controlled Trials identified an increased Risk Ratio for the development of hypotension in procedures where propofol was used compared to the use of etomidate (2 studies, n=260, RR 2.0 [95% CI 1.37 – 2.92], p=0.0003), remimazolam (1 study, n=384, RR 2.15 [1.61 – 2.87], p=0.0001), midazolam (14 studies, n=2218, RR 1.46 [ 1.18 – 1.79], p=0.0004) or all benzodiazepines (15 studies, n=2602, 1.67 [1.41 – 1.98], p<0.00001). Hypotension was less likely with propofol than when dexmedetomidine was used (1 study, n=60, RR 0.24 [0.09 – 0.62], p=0.003). Conclusions. Hypotension is common during propofol sedation for colonoscopy and of a magnitude and duration associated with harm in surgical patients

A comparison of linear and logarithmic auditory tones in pulse oximeters

This study compared the ability of forty anaesthetists to judge absolute levels of oxygen saturation, direction of change, and size of change in saturation using auditory pitch and pitch difference in two laboratory-based studies that compared a linear pitch scale with a logarithmic scale. In the former the differences in saturation become perceptually closer as the oxygenation level becomes higher whereas in the latter the pitch differences are perceptually equivalent across the whole range of values. The results show that anaesthetist participants produce significantly more accurate judgements of both absolute oxygenation values and size of oxygenation level difference when a logarithmic, rather than a linear, scale is used. The line of best fit for the logarithmic function was also closer to x ¼ y than for the linear function. The results of these studies can inform the development and standardisation of pulse oximetry tones in order to improve patient safety

Sympathetic autonomic dysfunction and impaired cardiovascular performance in higher risk surgical patients: implications for perioperative sympatholysis

OBJECTIVE: Recent perioperative trials have highlighted the urgent need for a better understanding of why sympatholytic drugs intended to reduce myocardial injury are paradoxically associated with harm (stroke, myocardial infarction). We hypothesised that following a standardised autonomic challenge, a subset of patients may demonstrate excessive sympathetic activation which is associated with exercise-induced ischaemia and impaired cardiac output. METHODS: Heart rate rise during unloaded pedalling (zero workload) prior to the onset of cardiopulmonary exercise testing (CPET) was measured in 2 observation cohorts of elective surgical patients. The primary outcome was exercise-evoked, ECG-defined ischaemia (>1 mm depression; lead II) associated with an exaggerated increase in heart rate (EHRR ≥12 bpm based on prognostic data for all-cause cardiac death in preceding epidemiological studies). Secondary outcomes included cardiopulmonary performance (oxygen pulse (surrogate for left ventricular stroke volume), peak oxygen consumption (VO2peak), anaerobic threshold (AT)) and perioperative heart rate. RESULTS: EHRR was present in 40.4-42.7% in both centres (n=232, n=586 patients). Patients with EHRR had higher heart rates perioperatively (p<0.05). Significant ST segment depression during CPET was more common in EHRR patients (relative risk 1.7 (95% CI 1.3 to 2.1); p<0.001). EHRR was associated with 11% (95%CI 7% to 15%) lower predicted oxygen pulse (p<0.0001), consistent with impaired left ventricular function. CONCLUSIONS: EHRR is common and associated with ECG-defined ischaemia and impaired cardiac performance. Perioperative sympatholysis may further detrimentally affect cardiac output in patients with this phenotype

Patient-maintained sedation for oral surgery using a target-controlled infusion of propofol - a pilot study

OBJECTIVE: To assess the safety and efficacy of a new patient-maintained propofol system for conscious sedation in dentistry. DESIGN: Prospective clinical trial SETTING: Department of Sedation, Glasgow Dental Hospital and School, 2001 SUBJECTS AND METHODS: Patients scheduled for oral surgery with conscious sedation. Exclusions included ASA IV -V, inability to use the handset, opioid use and severe respiratory disease. INTERVENTIONS: Patients were given intravenous propofol to a level of 1.0 microg/ml (reducing from 1.5 microg/ml) using a target controlled infusion system, they then controlled their sedation level by double-clicking a handset which on each activation increased the propofol concentration by 0.2 microg/ml. MAIN OUTCOME MEASURES: Oxygen saturation, patient satisfaction, and surgeon satisfaction. RESULTS: Twenty patients were recruited, 16 female and four male. Nineteen patients completed sedation and treatment successfully. Mean lowest oxygen saturation was 94%. No patients were over-sedated. All patients successfully used the system to maintain a level of sedation adequate for their comfort. Patient and surgeon satisfaction were consistently high. CONCLUSIONS: Initial experience with this novel system has confirmed safety, patient satisfaction and surgeon satisfaction