J. J. Pandit

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.

Recommendations for standards of monitoring during anaesthesia and recovery 2015: Association of Anaesthetists of Great Britain and Ireland.

This guideline updates and replaces the 4th edition of the AAGBI Standards of Monitoring published in 2007. The aim of this document is to provide guidance on the minimum standards for physiological monitoring of any patient undergoing anaesthesia or sedation under the care of an anaesthetist. The recommendations are primarily aimed at anaesthetists practising in the United Kingdom and Ireland. Minimum standards for monitoring patients during anaesthesia and in the recovery phase are included. There is also guidance on monitoring patients undergoing sedation and also during transfer of anaesthetised or sedated patients. There are new sections discussing the role of monitoring depth of anaesthesia, neuromuscular blockade and cardiac output. The indications for end‐tidal carbon dioxide monitoring have been updated.

A comparison of superficial versus combined (superficial and deep) cervical plexus block for carotid endarterectomy: a prospective, randomized study.

Carotid endarterectomy may be performed by using cervical plexus blockade with local anesthetic supplementation by the surgeon during surgery. Most practitioners use either a superficial cervical plexus block or a combined (superficial and deep) block, but it is unclear which offers the best operative conditions or greatest patient satisfaction. We compared the two techniques in patients undergoing carotid endarterectomy. Forty patients undergoing carotid endarterectomy were randomized to receive either a superficial or a combined cervical plexus block. Bupivacaine 0.375% to a total dose of 1.4 mg/kg was used. The main outcome measure was the amount of supplemental lidocaine 1% used by the surgeon. Subsidiary outcome measures were postoperative pain score, sedative and analgesic requirements before and during surgery, and postoperative analgesic requirements. Median supplemental lidocaine requirements were 100 mg (range 30–180 mg) in the superficial block group and 115 mg (range 30–250 mg) in the combined block group. These differences were not statistically significant (Mann-Whitney U-test). There was no significant difference in the number of patients needing postoperative analgesia between the groups (11 of 20 in the deep block group versus 8 of 20 in the superficial block group) in the 24 h after surgery. The median time to first analgesia in the superficial block group was 150 min, more than in the combined block group (median time 45 min) but this difference, although large, was not statistically significant (Mann-Whitney U-test). We found no significant differences between the anesthetic techniques studied. All patients reported satisfaction with the techniques. Implications Carotid endarterectomy may be performed satisfactorily by using either superficial or combined block, and it is found that peroperative lidocaine requirements will be the same regardless of which block is used. The decision to use one block or the other might, therefore, reasonably be influenced by the relative safety of the superficial block compared with the combined block, because previous work suggests the deep injection is associated with a more frequent complication rate.

The concept of surgical operating list ‘efficiency’: a formula to describe the term

While numerous reports have sought ways of improving the efficiency of surgical operating lists, none has defined ‘efficiency’. We describe a formula that defines efficiency as incorporating three elements: maximising utilisation, minimising over‐running and minimising cancellations on a list. We applied this formula to hypothetical (but realistic) scenarios, and our formula yielded plausible descriptions of these. We also applied the formula to 16 consecutive elective surgical lists from three gynaecology teams (two at a university hospital and one at a non‐university hospital). Again, the formula gave useful insights into problems faced by the teams in improving their performance, and it also guided possible solutions. The formula confirmed that a team that schedules cases according to the predicted durations of the operations listed (i.e. the non‐university hospital team) suffered fewer cancellations (median 5% vs 8% and 13%) and fewer list over‐runs (6% vs 38% and 50%), and performed considerably more efficiently (90% vs 79% and 72%; p = 0.038) than teams that did not do so (i.e. those from the university hospital). We suggest that surgical list performance is more completely described by our formula for efficiency than it is by other conventional measures such as list utilisation or cancellation rate alone.

Total oxygen uptake with two maximal breathing techniques and the tidal volume breathing technique: a physiologic study of preoxygenation.

Background Three common methods for preoxygenation are 3 min of tidal breathing, four deep breaths taken within 30 s (4DB), and eight deep breaths taken within 60 s (8DB). This report compares these three techniques in healthy volunteers. Methods Five healthy subjects breathed through a mouthpiece and wore a nose clip; oxygen was delivered at 180 l/min via a low-resistance T-piece. Each subject repeated each of the three oxygenation techniques four times. The end-tidal fraction of oxygen was measured, and the oxygen uptake at the mouth was measured breath by breath. The additional difference between oxygen uptake at the mouth during the period of breathing oxygen (as compared with that during air breathing) was taken to represent the total oxygen sequestrated into body stores. Results The mean ± SD maximum end-tidal fraction of oxygen after the 4DB method was 0.83 ± 0.09, which was significantly less than either after the 3-min method (0.92 ± 0.01; P < 0.04) or after the 8DB method (0.91 ± 0.04; P < 0.03). The mean additional oxygen taken up during oxygenation with the 4DB method was 1.67 ± 0.45 l, which was significantly lower than with the 3-min method (2.23 ± 0.85 l; P < 0.04) or with the 8DB method (2.53 ± 0.74 l; P < 0.01). There were no significant differences for these variables between the 3-min and 8DB methods. Conclusions For the physiologic measurements that were made, both the 3-min and the 8DB method are superior to the 4DB method. The 3-min and 8DB methods seem to be equally effective.

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.

Comparison of times to achieve tracheal intubation with three techniques using the laryngeal or intubating laryngeal mask airway

Summary We compared the times to intubate the trachea using three techniques in 60 healthy patients with normal airways: (i) fibreoptic intubation with a 6.0‐mm reinforced tracheal tube through a standard laryngeal mask airway (laryngeal mask−fibreoptic group); (ii) fibreoptic intubation with a dedicated 7.0‐mm silicone tracheal tube through the intubating laryngeal mask airway (intubating laryngeal mask−fibreoptic group); (iii) blind intubation with the dedicated 7.0‐mm silicone tracheal tube through the intubating laryngeal mask airway (intubating laryngeal mask−blind group). Mean (SD) total intubation times were significantly shorter in the intubating laryngeal mask−blind group (49 (20) s) than in either of the other two groups (intubating laryngeal mask−fibreoptic 74 (21) s; laryngeal mask−fibreoptic group 75 (36) s; p < 0.001). However, intubation at the first attempt was less successful with the intubating laryngeal mask−blind technique (15/20 (75%)) than in the other two groups (intubating laryngeal mask−fibreoptic 19/20 (95%) and laryngeal mask−fibreoptic 16/20 (80%)) although these differences were not statistically significant. We conclude that in this patient group, all three techniques yield acceptable results. If there is a choice of techniques available, the intubating laryngeal mask−blind technique would result in the shortest intubation time.

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.

If it hasn't failed, does it work? On 'the worst we can expect' from observational trial results, with reference to airway management devices.

1131 patients undergoing proximal femoral fracture repair: a retrospective, observational study of effects on blood pressure, fluid administration and perioperative anaemia. Anaesthesia 2011; 66: 1017–22. 21. White SM, Baldwin TJ. The Mental Capacity Act 2005 implications for anaesthesia and critical care. Anaesthesia 2006; 61: 381–9. 22. The National Hip Fracture Database. The National Hip Fracture Database National Report 2011 summary. http:// www.nhfd.co.uk/003/hipfractureR.nsf/ NHFDNationalReport2011_Final.pdf (accessed 24 ⁄ 01 ⁄ 2012). 23. Vandenbroucke JP. Why do the results of randomised and observational studies differ? British Medical Journal 2011; 343: d7020.

Bispectral index-guided management of anaesthesia in permanent vegetative state.

A patient in a permanent vegetative state required general anaesthesia for dental surgery. Because of the uncertainties involved in the appropriate monitoring and assessment of the conscious level of patients in a permanent vegetative state, it was decided to use the bispectral index to help guide the anaesthetic depth during surgery. We found that the bispectral index profile during anaesthesia and surgery was similar to that of a normal subject. The findings raise the possibility that patients in permanent vegetative states might sense noxious stimuli at a cortical level.