Complications of anaesthesia

The question, ‘What are the complications of anaesthesia?’ would seem to be a very reasonable one to ask of an anaesthetist in training. There are several reasons why trainees should be able to answer this question – certainly to pass examinations, but more importantly to avoid these complications if possible, and to inform patients who need to understand the implications of consenting to have an anaesthetic. The last two reasons also apply to specialists. Surprisingly, the question is quite difficult to answer. One might expect that the answer would include certain categories of complication, and some indication of the likelihood of occurrence of each category. It would also seem reasonable to expect an understanding of how each complication might come about, how to avoid it and how to manage it if it actually does occur. The articles in this special edition of Anaesthesia go some way towards answering these questions. The hazards of anaesthesia are many and varied (Table 1), and may or may not result in harm to patients. However, every anaesthetic is associated with hazard, and a hazard is not in itself a complication; rather it is something that may manifest in an undesired way to create a complication. Dental trauma Soft tissue trauma Hypoxia Difficult airway Inexperience Urgency Hypoxia Airway trauma Surgical airway Abandoned surgery Death Difficult airway Inexperience Poor airway assessment Pulmonary barotrauma Pneumothorax Inadequate muscle relaxation Obesity Bronchospasm Pneumoperitoneum Inexperience Failure to auscultate chest Pneumonitis Prolonged ventilation Unfasted patient Reflux Difficult central line insertion Inexperience Myocardial ischaemia Cardiac arrest Brain injury Bleeding Sepsis Neuraxial block Hypovolaemia Bleeding Stroke Vascular accidents such as anastamosis or aneurysm rupture. Light anaesthetic Inadequate analgesia Awareness Peripheral nerve injury Weakness Pain Incorrect positioning of patient Inexperience Difficult epidural or spinal Inexperience Difficult procedure Long surgery Inexperience Anticoagulation Coagulopathy Bleeding disorder Awareness Psychological trauma High-risk surgery Comorbid patient Distraction Patient factors Inadequate history taking Patient factors Inadequate history taking Inadequate labelling Inattention Distraction Lack of drug effect Compartment syndrome Tissue necrosis Difficult i.v. access i.v. line in situ from the ward The hazards of anaesthesia can be considered in relation to the patient and the practitioner 1, 2. Is the same thing true of complications? For example, if an anaesthetist acquires hepatitis C from a patient, is that a complication of anaesthesia? What if he or she becomes addicted to opioids, or commits suicide because of the opportunities and stresses associated with giving anaesthetics? Interestingly, the idea that the well being of practitioners should be included in considerations of the outcomes of medical practice is receiving increased emphasis; for example, the suggestion that the Institute of Healthcare Improvement's Triple Aim for healthcare services 3, 4 should become quadruple and include the aim of ensuring the well being of staff 5. The Oxford English Dictionary provides several definitions of the word ‘complication’, some of which derive from the Latin ‘complicare’, meaning ‘fold together’, and conveys ideas of combining or interweaving 6. These are historically interesting, but the following more germane, although somewhat self-referential, definition is also given: ‘Something that complicates or adds difficulties; a complicating factor.’ In the shorter modern versions of the Oxford Dictionary, one finds ‘A circumstance that complicates something; a difficulty,’ and ‘An involved or confused condition or state’ 7. The Merriam-Webster dictionary gives, among other things, ‘a difficult factor or issue often appearing unexpectedly and changing existing plans, methods, or attitudes’ 8 and Collins English Dictionary suggests that ‘A complication is a problem or difficulty that makes a situation harder to deal with’ 9. The Oxford English Dictionary also provides an additional sense of the term: ‘A secondary disease or condition aggravating an already existing one’ 7 and Merriam-Webster similarly gives ‘a secondary disease or condition developing in the course of a primary disease or condition’ 8. Interestingly, two textbooks on the complications of anaesthesia appear to provide no definition of this term 10, 11, but a third, by Valchanov et al., offers the following, without citing any prior source: ‘a complication is an unfavourable evolution of a disease process or its management’ 12. The idea of a secondary disease or condition applies well enough to something like a postoperative infection or malignant hyperthermia as a complication of surgery and anaesthesia, respectively. However, in the present context, it seems important also to capture notions of unexpected difficulties or problems. A definition along these lines would clearly include the aforementioned examples and also events such as a ‘can't intubate, can't oxygenate’ crisis, which we think should probably be seen as a complication of anaesthesia even when resolved without any harm to the patient. On the other hand, this view draws wide boundaries around the scope of complications of anaesthesia. Are these boundaries too wide, and should we seek to narrow them a little? Or is it the case that this whole discussion is unnecessary. Surely, like an elephant, we know a complication of anaesthesia when we see one? But do we? What are some of the considerations that might matter in determining where this boundary should lie? One such consideration is the increasing emphasis on the importance of open disclosure 13 and duty of candour. The word ‘complication’ conveys a sense that something of importance has occurred. It has connotations of gravity. Thus, it would seem reasonable for a patient (or a patients’ family or other support people) to expect to be informed of any event worthy of being deemed a complication that occurred during his or her anaesthetic. In some cases, it would be obvious that a problem had occurred – if a patient died, aspirated gastric contents or suffered damage to a tooth, to give some examples. But, when certain other things go wrong, the accidental administration of a wrong drug during an anaesthetic perhaps, there would be no way for the patient to know about this unless it was disclosed, or unless some obvious effect followed. How many anaesthetists would deem it necessary, or even helpful, to disclose such an event to a patient? From the perspective of our linguistic definitions, the administration of a wrong drug does seem to be unexpected (at least in any particular anaesthetic) and to introduce at least some difficulty, even if this only extends to deciding whether now to give the intended drug. The view that drug administration errors matter is supported by the fact that various investigators have deemed drug errors worthy of reporting and analysing, and there have been numerous calls for action to reduce the incidence of these events 14-16. On the other hand, no surgical procedure or anaesthetic is in fact completely perfect, notwithstanding the view expressed below that we might like them to be. Some drug errors are trivial, and their significance lies predominantly in the fact that they reflect an underlying hazard that might manifest with more serious consequences next time. Nevertheless, the question arises of how certain one can be that no harm has ensued from such an event. Consider the specific example of the accidental omission of a prophylactic injection of antibiotic until after the surgical incision has been made. This could contribute to the subsequent development of a postoperative infection, which may not appear for some days or weeks, possibly long after the patient has been discharged from hospital. Is such an omission a complication (and should it be disclosed) or is it only the infection that constitutes a complication? What if an anaesthetic vaporiser was not switched on for rather longer than intended after the administration of neuromuscular blockers? Should this count, or is it only the actual development of an episode of awareness that constitutes a complication? Arguably, this example is made more difficult by the fact that awareness may occur but not be recalled 17, 18. Should awareness without recall be considered a complication? One's perspective may depend on whether one was being asked before or after being subjected to this particular experience! Putting oneself in the position of the patient, the test might well be whether one would oneself wish to know that something unusual had occurred, and one reason for such a wish would be the possibility of future consequences. Importantly, there are some undesirable or unfavourable evolutions of disease processes and their management (to use the terminology of Valchonov et al. 12), that are expected, at least in some patients, even if everything is done perfectly. For example, surgery will usually result in some sort of scar, and this would not normally be viewed as a complication. Anaesthesia will often result in nausea and vomiting and up to a certain level of severity, this would probably not be called a complication either. The occurrence of some degree of nausea and vomiting would more properly be called a side-effect of some of the drugs commonly used in anaesthesia. Its incidence and severity can be reduced, but it cannot be eliminated. Patients are simply expected to accept such statistically inevitable consequences of treatment, provided they have been informed about their likelihood and consented to the treatment. They have no grounds to complain, or to seek compensation or even an apology, although it would not be unreasonable for their doctors to express empathy if an opportunity arose. This brings us back to the question of human errors, including, but not limited to, those involving drug administration. Human errors are in fact statistically inevitable, so does the same thing apply? Few people would think so. Rather, most people would probably think that they should not occur, and that something has gone wrong if they do. In our chapters on hazards 1, 2, 19, 20, we discuss this issue in some depth, and argue more generally that the occurrence of an adverse event during or after the administration of an anaesthetic does not in itself mean that there has been any failure in the standard of care, even if an error contributed to it. At the same time, we make it clear that we believe every effort should be made to avoid errors and more generally to minimise the possibility of adverse events arising from anaesthesia. This slightly paradoxical position may perhaps provide a useful way of thinking about complications. We have come a long way from the time when Professor Robert Macintosh made a scathing call for a change in the way adverse events, including death, were viewed 21. He argued, unlike many others at that time, that these should no longer be attributed to some mysterious malevolent property of anaesthesia itself. Instead their causes should be understood and every effort made to avoid them in the future. We think most anaesthetists today aim for very high standards of practice. We think that, in general, any anaesthetist would find any harm to a patient very distressing. We also think most anaesthetists would very much prefer to avoid imperfections of any sort in the conduct of their anaesthetics, even when these do not result in harm. There is a growing appreciation of the direct relationship between the number of little things which go wrong in clinical practice and patient outcomes; on its own, each little deviation from the pathway of perfect care may make no perceptible difference, but the more such deviations there are, the more likely it is that there will be a negative impact on outcomes overall 22. It would be remiss to finish this discussion without noting that even when there is agreement that an adverse peri-operative event is a complication, it is often unexpectedly difficult to define it precisely, and sometimes even more difficult to judge whether it is related to, or attributable to anaesthesia. This becomes particularly important when complications are used as an endpoint in research. For example, what is a postoperative ‘chest infection’? Would a chest infection be deemed to have occurred merely because there is reference to clinical suspicion in the patient chart? Or would other criteria be required, such as a productive cough (and what does ‘productive’ mean?), positive auscultation signs, a threshold decrease in oxygen saturation on air or positive findings on a chest radiograph (and who interprets the radiographic findings?). How would linkage to ventilation during anaesthesia in the operating room be inferred? We do not pretend to have answers to these questions, but they are very typical of the sort of issues that require resolution when complications are used as outcome measures in research. Not surprisingly there are multiple examples of contemporary initiatives to establish definitions of complications a priori before embarking on large studies 23, 24. From this perspective, the definition of Valchanov et al. 12 is arguably a little too generic for our purposes. We suggest that a complication of anaesthesia could be defined as ‘anything arising during or attributable to anaesthesia that was unexpected and created a potential or actual problem or difficulty or made the patient's care harder to deal with.’ This definition is primarily patient-centred, as it should be, but one could take it to include problems arising for clinical staff as well. Trivial errors would not qualify, although this does not mean that lessons cannot be learned from them. The occurrence of a complication should not in itself be construed as evidence of a failure in the standard of care, but any event meeting this definition should normally be disclosed. Furthermore, such events should be recorded and reviewed, and every effort should be made to understand more about them in order to reduce their occurrence. In the simplest of terms, complications are something we do not want in our anaesthetics, for our patients or for ourselves. We should do everything reasonably possible to avoid them and to mitigate their effects when they do occur. We are grateful to Matthew R. Moore for compiling and formatting the manuscript for publications. AM has financial interests in and is a director of Safer Sleep LLC, is Chair of the Board of the Health Quality and Safety Commission in New Zealand, is a Board Member of the World Federation of Societies of Anaesthesiologists, and is a Board Member of Lifebox.