INTRODUCTION

• Jurisdiction: Australia

Aim of the chapter and evidence-based medicine ....................................... [43.100]

Brief history of anaesthesia

Before 1846 .................................................................................................. [43.200]

Anaesthesia .................................................................................................. [43.220]

Definition of anaesthesia

Medical definition .......................................................................................... [43.400]

Extent of anaesthesia care ........................................................................... [43.420]

Definition of anaesthetist Medical practitioners

Specialists ..................................................................................................... [43.600]

Non-specialists .............................................................................................. [43.620]

Non-medical practitioners ............................................................................. [43.640]

Independent anaesthesia care providers ..................................................... [43.660]

Anaesthesia assistants ................................................................................. [43.680]

The anaesthesia care team Team components

Human factors ............................................................................................... [43.800]

[43.100] Aim of the chapter and evidence-based medicine

The aim of this chapter is to provide an overview of the specialty of anaesthesia, which is unfamiliar to many non-anaesthetist healthcare workers, let alone members of the legal profession. As detailed below, care provided by anaesthetists encompasses patients of all ages, sizes and types, in the periods before, during and after operations and other procedures and in a wide variety of settings in hospitals and clinics.

However, it is not within the realm of the chapter to provide the reader with an exhaustive and a complete description of every aspect of anaesthetic care. Rather, this chapter should be seen as providing an outline of the extent of the specialty and the various discussions as primers for specific topics.

In addition, this chapter is heavily referenced to facilitate access to further information. A range of references has been selected, from those existing only on the Internet to others in medical journals. Where possible, references from the evidence-based medicine (EBM) literature have been selected. EBM was developed at McMaster University, Hamilton, Ontario and has been defined as the "conscientious, explicit, and judicious use of the best evidence in making decisions about the care of individual patients". Evidence can be categorised according to the design of the studies from which the evidence was derived, should "reflect susceptibility to bias" and should help determine the strength of derived recommendations: Pedersen et al (2002). Table 1 below lists categories for the sources of evidence and strength of recommendations.

TABLE 1 Categories for the sources of evidence and strength of recommendations: Pedersen et al (2002]

Grade	Evidence source	Grade	Strength of recommendation for treatment
Ia	At least one meta-analysis of randomised controlled trials or systematic review	A	Good
Ib	A properly randomised controlled trial	A	Good
IIa	Well-designed controlled trial without randomisation	B	Fair
IIb	Other types of quasi-experimental studies	B	Fair
III	Descriptive studies, such as case-control	C	Insufficient evidence for or against, with treatment choice made on other grounds
IV	Opinions of respected authorities: clinical experience, textbooks, or expert committees	D	Fair evidence to exclude the treatment

Slightly different versions exist in other countries. For example, in Australia, the National Health and Medical Research Council developed an "approach to grading evidence recommendations, which should be relevant to any clinical guideline (not just those dealing with interventions)". In developing this approach, two public consultations and formal pilot testing were undertaken. The resulting documents provide a "new NHMRC hierarchy of levels of evidence and their role in the formulation of the new grades of recommendation" as well as a "process for grading recommendations": NHMRC (2013). Both documents have also undergone independent peer review before publication in a medical journal: Merlin et al (2009); Hillier et al (2011).

In the last few years another classification of the quality of evidence and strength of recommendations has been developed - Grading of Recommendations Assessment, Development and Evaluation (GRADE): Guyatt et al (2011). The developers wished to produce an "optimal system of rating quality of evidence and determining strength of recommendations for clinical practice guidelines" (Guyatt et al, 2011) because of a worldwide "inconsistent approach to grading evidence and making recommendations by guideline developers": Strauss & Sheppard (2011). In 2002 a systematic review of systems rating the strength of evidence determined that there were more than 100 such systems: West et al (2002). Not only do these systems vary but also recommendations (eg, for the treatment of low back pain) were shown to vary, depending on which system of evidence assessment was used: Ferreira et al (2002). These widely varying recommendations lead to "confusion for those trying to implement the guidelines" (Strauss & Sheppard, 2002) as well as the effects on patients are unknown.

One important point that the developers of GRADE made is that "in the absence of high-quality evidence, clinicians must look to lower quality evidence to guide their decisions". These authors argued that while "developing recommendations always requires the opinion of experts", which is based on numerous factors, including basic and applied knowledge and experience, "opinion is not evidence": Balshem et al (2011). The GRADE classification does not include "Opinions of respected authorities: clinical experience, textbooks, or expert committees" (Pedersen et al, 2002) as shown in Table 1.

Another centre, the Centre for Evidence-based Medicine (CEBM) in Oxford, produces and updates "The Oxford Levels of Evidence": Howick et al (2011). Unlike GRADE, these updates "refrain from making definitive recommendations", thus permitting use when "no systematic reviews available" (Howick et al, 2011).

In the specialty of anaesthesia, readers should note that application of EBM principles has been described as "slow". The most important factor is probably the lack of "hard evidence to support many treatments": Pedersen et al (2002). In the past this was because EBM studies had simply not been carried out. However, some studies cannot be undertaken. For example, the Multi-Centre Study of General Anaesthesia attempted to determine if there were differences in outcomes for patients randomly allocated to one of four different types of general anaesthetics: Forrest et al (1990a, 1990b, 1992). Importantly, no patient could be randomly allocated to a "no anaesthetic" group.

More recently, Bekkering and colleagues reviewed the relevant aspects of EBM germane to the anesthesiologist with a focus on implementation of EBM into daily practice (Bekkering et al, 2012). This involved following through the cyclical five steps required to complete the EBM cycle. First, one needs to ask a relevant clinical question. Second, one needs to find (if possible) any evidence to answer the question. Third, all evidence must be appraised. Fourth, the findings must be applied to clinical practice. This entails integrating the evidence, the practitioner's clinical experience and preferences expressed by patients. Fifth, the previous four steps should be reviewed. Needless to say, all of this requires effort on the part of the practitioner, to undertake each step, to be truly reflective of one's own practice and to consider any preferences expressed by patients without bias.

Since 2002, the number of EBM-related publications has greatly increased, from about 30 up to 2002 and nearly 240 towards the end of 2015. Topics covered range from a systematic review of randomised controlled trial of media-based interventions to educate patients about anaesthesia (Lee et al, 2003) to a systematic review of postoperative cognitive dysfunction after non-cardiac surgery (Newman et al, 2007) to an article on the ability to improve with change, which starts by quoting Charles Dicken's Great Expectations: "Take nothing on its looks; take everything on evidence. There's no better rule" (Beattie, 2015). The basic reason for the development of guidelines has been the wish to decrease variations in clinical practice and thus improve the quality of care. Evidence-based, clinical practice guidelines are therefore intended to "help clinicians, patients, and policy makers make decisions that are consistent with the evidence". However, as argued by Strauss and Sheppard (2011), the worldwide "plethora of guidelines has become a source of variation in care - rather than reduce such practice variation": Strauss & Sheppard (2011).

The term EBM has on occasion been replaced by the terms "evidence informed practice" (Glasziou, 2004) and "evidence informed medicine" (Glasziou, 2005). This seemingly slight modification of the term emphasises the importance of the fact that there are very few "absolutes" in medicine and that decision-making represents a series of "choices". Guidelines are neither rules nor standards. As the NHMRC described them, guidelines are "sets of non-mandatory rules, principles or recommendations for procedures or practices in a particular field". Another description is that of "systematically developed statements to assist practitioner and patient decisions about appropriate healthcare for specific clinical circumstances": Field & Lohr...