Jonathan H. Mackay

5th National Audit Project (NAP5) on accidental awareness during general anaesthesia: summary of main findings and risk factors

We present the main findings of the 5th National Audit Project (NAP5) on accidental awareness during general anaesthesia (AAGA). Incidences were estimated using reports of accidental awareness as the numerator, and a parallel national anaesthetic activity survey to provide denominator data. The incidence of certain/probable and possible accidental awareness cases was ~1:19,600 anaesthetics (95% confidence interval 1:16,700-23,450). However, there was considerable variation across subtypes of techniques or subspecialities. The incidence with neuromuscular block (NMB) was ~1:8200 (1:7030-9700), and without, it was ~1:135,900 (1:78,600-299,000). The cases of AAGA reported to NAP5 were overwhelmingly cases of unintended awareness during NMB. The incidence of accidental awareness during Caesarean section was ~1:670 (1:380-1300). Two-thirds (82, 66%) of cases of accidental awareness experiences arose in the dynamic phases of anaesthesia, namely induction of and emergence from anaesthesia. During induction of anaesthesia, contributory factors included: use of thiopental, rapid sequence induction, obesity, difficult airway management, NMB, and interruptions of anaesthetic delivery during movement from anaesthetic room to theatre. During emergence from anaesthesia, residual paralysis was perceived by patients as accidental awareness, and commonly related to a failure to ensure full return of motor capacity. One-third (43, 33%) of accidental awareness events arose during the maintenance phase of anaesthesia, mostly due to problems at induction or towards the end of anaesthesia. Factors increasing the risk of accidental awareness included: female sex, age (younger adults, but not children), obesity, anaesthetist seniority (junior trainees), previous awareness, out-of-hours operating, emergencies, type of surgery (obstetric, cardiac, thoracic), and use of NMB. The following factors were not risk factors for accidental awareness: ASA physical status, race, and use or omission of nitrous oxide. We recommend that an anaesthetic checklist, to be an integral part of the World Health Organization Safer Surgery checklist, is introduced as an aid to preventing accidental awareness. This paper is a shortened version describing the main findings from NAP5--the full report can be found at http://www.nationalauditprojects.org.uk/NAP5_home.

Guideline for resuscitation in cardiac arrest after cardiac surgery

The Clinical Guidelines Committee of the European Association for Cardio-Thoracic Surgery provides this professional view on resuscitation in cardiac arrest after cardiac surgery. This document was created using a multimodal methodology for evidence generation including the extrapolation of existing guidelines from the International Liaison Committee on Resuscitation where possible, our own structured literature reviews on issues particular to cardiac surgery, an international survey on resuscitation hosted by CTSNet and manikin simulations of potential protocols. This protocol differs from existing generic guidelines in a number of areas, the most import of which are the following: successful treatment of cardiac arrest after cardiac surgery is a multi-practitioner activity with six key roles that should be allocated and rehearsed on a regular basis; in ventricular fibrillation, three sequential attempts at defibrillation (where immediately available) should precede external cardiac massage; in asystole or extreme bradycardia, pacing (where immediately available) should precede external cardiac massage; where the above measures fail, and in pulseless electrical activity, early resternotomy is advocated; adrenaline should not be routinely given; protocols for excluding reversible airway and breathing complications and for safe emergency resternotomy are given. This guideline is subject to continuous informal review, and when new evidence becomes available.

Increasing organ blood flow during cardiopulmonary bypass in pigs : comparison of dopamine and perfusion pressure

OBJECTIVE To determine whether low-dose dopamine infusion (5 micrograms/kg/min) during cardiopulmonary bypass selectively increases perfusion to the kidney, splanchnic organs, and brain at low (45 mm Hg) as well as high (90 mm Hg) perfusion pressures. DESIGN Randomized crossover trial. SETTING Animal research laboratory in a university medical center. SUBJECTS Ten female Yorkshire pigs (weight 29.9 +/- 1.2 kg). INTERVENTION Anesthetized pigs were placed on normothermic cardiopulmonary bypass at a 100-mL/kg/min flow rate. After baseline measurements, the animal was subjected, in random sequence, to 15-min periods of low perfusion pressure (45 mm Hg), low perfusion pressure with dopamine (5 micrograms/kg/min), high perfusion pressure (90 mm Hg), and high perfusion pressure with dopamine. Regional perfusion (radioactive microspheres) was measured in tissue samples (2 to 10 g) from the renal cortex (outer two-third and inner one-third segments), stomach, duodenum, jejunum, ileum, colon, pancreas, and cerebral hemispheres. MEASUREMENTS AND MAIN RESULTS Systemic perfusion pressure was altered by adjusting pump flow rate (r2 = .61; p < .05). In the kidney, cortical perfusion pressure increased from 178 +/- 16 mL/min/100 g at the low perfusion pressure to 399 +/- 23 mL/min/100 g at the high perfusion pressure (p < .05). Perfusion pressure augmentation increased the ratio of outer/inner renal cortical blood flow from 0.9 +/- 0.1 to 1.2 +/- 0.1 (p < .05). At each perfusion pressure, low-dose dopamine had no beneficial effect on renal perfusion or flow distribution. Similar results were found in the splanchnic organs, where regional perfusion was altered by perfusion pressure but not by dopamine. In contrast, neither changing perfusion pressure nor adding low-dose dopamine altered blood flow to the cerebral cortex. CONCLUSIONS These data indicate that the lower autoregulatory limits of perfusion to the kidneys and splanchnic organs differ from those limits to the brain during normothermic bypass. Selective vasodilation from low-dose dopamine was not found in renal, splanchnic, or cerebral vascular beds. Increasing the perfusion pressure by pump flow, rather than by the addition of low-dose dopamine, enhanced renal and splanchnic but not cerebral blood flows during cardiopulmonary bypass.

5th National Audit Project (NAP5) on accidental awareness during general anaesthesia: protocol, methods, and analysis of data

BACKGROUND Accidental awareness during general anaesthesia (AAGA) with recall is a potentially distressing complication of general anaesthesia that can lead to psychological harm. The 5th National Audit Project (NAP5) was designed to investigate the reported incidence, predisposing factors, causality, and impact of accidental awareness. METHODS A nationwide network of local co-ordinators across all the UK and Irish public hospitals reported all new patient reports of accidental awareness to a central database, using a system of monthly anonymized reporting over a calendar year. The database collected the details of the reported event, anaesthetic and surgical technique, and any sequelae. These reports were categorized into main types by a multidisciplinary panel, using a formalized process of analysis. RESULTS The main categories of accidental awareness were: certain or probable; possible; during sedation; on or from the intensive care unit; could not be determined; unlikely; drug errors; and statement only. The degree of evidence to support the categorization was also defined for each report. Patient experience and sequelae were categorized using current tools or modifications of such. CONCLUSIONS The NAP5 methodology may be used to assess new reports of AAGA in a standardized manner, especially for the development of an ongoing database of case reporting. This paper is a shortened version describing the protocols, methods, and data analysis from NAP5--the full report can be found at http://www.nationalauditprojects.org.uk/NAP5_home.

Impact of the Anesthesiologist and Surgeon on Cardiac Surgical Outcomes

OBJECTIVE To determine the impact of anesthesiologists, surgeons, and their monthly caseload volume on mortality after cardiac surgery. DESIGN Ten-year audit of prospectively collected cardiac surgical data. SETTING Large adult cardiothoracic hospital. PARTICIPANTS A total of 18,569 cardiac surgical patients in the decade from April 2002 through March 2012, plus 21 consultant surgeons and 29 consultant anesthesiologists. INTERVENTIONS Major risk-stratified cardiac surgical operations. METHODS The primary outcome was in-hospital death. Random intercept models for the surgeon and anesthesiologist cluster, respectively, were fitted, achieving risk-adjustment through the logistic EuroSCORE. The intraclass correlation coefficient (ICC) subsequently was used to measure the amount of outcome variation due to clustering. MEASUREMENTS AND MAIN RESULTS After exclusions (duplicates, very-short-term appointments, and cases performed by more than one consultant), there were 18,426 patients with 581 (3.15%) in-hospital deaths. The overwhelming factor associated with outcome variation was the patient risk profile, accounting for 97.14% of the variation. The impact of the surgeon was small (ICC = 2.78%), and the impact of the anesthesiologist was negligible (ICC = 0.08%). Low monthly surgeon volume of surgery, adjusted for average case mix, was associated with higher risk-adjusted mortality (odds ratio = 0.93, 95% CI 0.87-0.98). CONCLUSIONS Outcome was determined primarily by the patient. There were small but significant differences in outcome between surgeons. The attending anesthesiologist did not affect patient outcome in this institution. Low average monthly surgeon volume was a significant risk factor. In contrast, low average monthly anesthesiologist volume had no effect.

Hyperglycemia During Hypothermic Canine Cardiopulmonary Bypass Increases Cerebral Lactate

Background Hyperglycemia frequently occurs during cardiopulmonary bypass (CPB), although its direct effects on cerebral perfusion and metabolism are not known. Using a canine model of hypothermic CPB, we tested whether hyperglycemia alters cerebral blood flow and metabolism and cerebral energy charge. Methods Twenty anesthetized dogs were randomized into hyperglycemic (n ‐ 10) and normoglycemic (n ‐ 10) groups. The hyperglycemic group received an infusion of D50 W, and the normoglycemic animals received an equal volume of 0.9% NaCl. Both groups underwent 120 min of hypothermic (28 degrees Celsius) CPB using membrane oxygenators, followed by rewarming and termination of CPB. Cerebral blood flow (radioactive microspheres) and the cerebral metabolic rate for oxygen were measured intermittently during the experiment and brain tissue metabolites were obtained after bypass. Results Before CPB, the glucose‐treated animals had higher serum glucose levels (534 plus/minus 12 mg/dL; mean plus/minus SE) than controls (103 plus/minus 4 mg/dL; P < 0.05), and this difference was maintained throughout the study. Cerebral blood flow and metabolism did not differ between groups at any time during the experiment. Sagittal sinus pressure was comparable between groups throughout CPB. Tissue high‐energy phosphates and water contents were similar after CPB, although cerebral lactate levels were greater in hyperglycemic (37.2 plus/minus 5.7 micro mol/g) than normoglycemic animals (19.7 plus/minus 3.7 micro mol/g; P < 0.05). After CPB, pH values of cerebrospinal fluid for normoglycemic (7.33 plus/minus 0.01) and hyperglycemic (7.34 plus/minus 0.01) groups were similar. Conclusions Hyperglycemia during CPB significantly increases cerebral lactate levels without adversely affecting cerebral blood flow and metabolism, cerebrospinal fluid pH, or cerebral energy charge.