The NAP 5 handbook: queries over monitoring neuromuscular function, induction doses, processed EEG monitoring and RSI : a reply

We thank Drs Rodney and Checketts 1 for their interest in the 5th National Audit Project (NAP5) Handbook (https://anaesthetists.org/Home/Resources-publications/Guidelines/The-NAP5-Handbook). They go to some length to challenge the adequacy of some statements and recommendations. There is insufficient space to address each of these, but most are addressed by reading the handbook in full. Drs Rodney and Checketts believe we fail to emphasise the importance of use of a quantitative nerve stimulator to assess adequacy of reversal of neuromuscular blocking drug (NMBD) effect. Firstly, the handbook states “As recommended in the Association's minimum monitoring guidelines published after NAP5, the nerve stimulator, which establishes motor capacity, should be employed when NMBDs are used. An adequate response to nerve stimulation (e.g. return of a ‘train of four’ (ToF) ratio of > 0.9, or another suitable measure) is a minimum criterion for adequacy of motor capacity. As qualitative assessment (i.e. manual detection of ToF or double burst stimulation) cannot detect a difference in ToF ratio of 0.3–0.7 it is likely that quantitative neuromuscular monitoring is required to reliably detect adequate return of motor capacity. Anaesthetists should use additional signs such as spontaneous breathing and signs of spontaneous movement before adequate motor capacity is judged restored.” We find it difficult to imagine that anaesthetists would read either this alone (or this and the referenced Association monitoring guidelines 2) and not conclude that it needs quantitative monitoring. Secondly, they challenge the logic of recommending that standard induction doses are used as the norm and non-standard doses in exceptions and describe how adequacy of anaesthetic depth should be established during induction. It is self-evident that if we recommend that standard doses are used as a norm that this happens in most cases. The guideline states “Standard induction doses for intravenous agents should be the norm. Deviating greatly from these requires careful thought, justification and, where appropriate, prior explanation to the patient as part of the consent process.” And further that “At induction, the anaesthetist should always confirm loss of consciousness before administering NMBDs or before airway instrumentation by the following (notwithstanding RSI as discussed below): (a) loss of motor response to command … (b) loss of response to stimulating manoeuvres such as jaw thrust, prior to laryngoscopy or insertion of any airway device (c) where depth of anaesthesia monitoring is used, an appropriate monitor output”. Drs Rodney and Checketts seem to have largely duplicated in their letter what we have already written in the handbook. Notwithstanding this, there do arise circumstances where ‘standard’ doses of induction drugs might be significantly harmful. In these circumstances, significantly reduced doses are in the patient's best interests and deliberately to avoid communicating the resulting increased risk of awareness would seem, we (and we suspect many courts) would judge, to be unkind and unethical. Thirdly, they suggest that awareness need not be discussed if a processed EEG is used for all cases. There are important problems with this suggestion. There is no evidence that a processed EEG eliminates awareness; at best it reduces it. There were several cases reported to NAP5 where awareness occurred despite use of a processed EEG and a reading consistently below that level that would denote risk of awareness 3. Also, in much of the UK, there is inadequate provision of processed EEG monitoring and in 2015 ‘depth of anaesthesia monitoring’ was used in only 22% of all UK anaesthetics 4. Finally, they propose abandonment of RSI. Although this is a complex and controversial topic, they offer no robust rationale to support this. In NAP4, pulmonary aspiration of gastric contents was the commonest case of anaesthesia-associated airway mortality and morbidity 5. NAP5 identified thiopental, RSI and obstetric surgery to all be risk factors for awareness. It is, therefore, notable that since NAP5 the use of thiopental has almost halved in the UK and this includes during general anaesthesia for Caesarean section 6, the highest risk procedure for awareness seen in NAP5 7. The same applies for the use of succinylcholine. These changes, to a more modern form of RSI, may be of greater benefit than complete abandonment of RSI.