Anaesthetic monitoring recommendations during general anaesthesia: how consistent are they across the globe? (Hendrickx, Feldman, Schüler)

Since patient safety is a universal concern for all anaesthesia professionals, one might expect monitoring recommendations to be consistent across the world. To evaluate this assertion, we reviewed the recommendations from several professional societies (AAGBI, ANZCA, ASA, EBA, HKCA, IFNA, WFSA, WHO) selected for varied geographic representation. Monitoring recommendations for parameters describing cardiac and pulmonary function were mostly consistent. Recommendations are less consistent for monitoring other physiological systems or the anaesthetic state, for example, unconsciousness and immobility.

Professional organisations provide practice recommendations, but there are also manufacturing standards from the International Organization for Standardization (ISO) and International Electrotechnical Commission governing how devices are designed and built for clinical use. In some cases, manufacturing standards exceed practice recommendations and therefore become de facto clinical standards. For example, ISO requires end-expired agent monitoring when inhalation anaesthetics are used which is not true for all practice recommendations.

Reconciling the inconsistencies between monitoring recommendations uncovered in this comparison is a challenge for the various professional organisations. Recommendations from professional societies can provide guidance to the practitioner about whether or not it is acceptable to proceed with an elective procedure if one or more monitoring modalities are not available. Standards provide a consistent approach to practice for clinicians and offer patients a guarantee that they will receive the safest possible care. We should seek to ensure that these standards are clear and provide common protections for all patients no matter where they live.


Monitoring recommendations for patients during anaesthesia care are intended to increase patient safety. Professional organisations develop these recommendations to provide guidance for safe anaesthesia practice. Since patient safety is a universal concern for all anaesthesia professionals, one might expect recommendations across the world to be consistent. But are they? In this nonsystematic review, the monitoring recommendations of seven different professional organisations and the relevant ISO anaesthesia workstation standards are compared. This work is a continuation of a project initiated by the Anesthesia Patient Safety Foundation (APSF) Committee on Technology (of which two authors are members) and published initially in the APSF Newsletter.481 At the invitation of the ESA PSQC, we have updated the original data with the recommendations of the Australian and New Zealand College of Anaesthetists and ISO anaesthesia workstation standards. The APSF kindly gave written permission to publish an update of the original article. The review is limited in scope to intra-operative monitoring recommendations during general anaesthesia.

Selection of standards: design and data sources

The monitoring recommendations of professional organisations were compared (Table 19). These organisations were selected as a cohort representative of standards in different parts of the world and varied practice settings. The list was not meant to be exhaustive – other professional organisations throughout the world such as the American Association of Nurse Anesthetists and those of many other countries offer important patient safety guidance to their constituents ( ISO standards for anaesthesia workstations were added to examine the congruency between manufacturing and practice standards. Anaesthesia workstation manufacturers have to comply with the mandatory ISO standards to achieve regulatory approval.

Table 19: Monitoring recommendations of professional organisations



‘Standards’: what’s in a name?

The ASA, IFNA, WHO–WFSA, AAGBI and ISO include the word ‘Standards’ in their title, whereas the EBA uses ‘Recommendations’ and the HKCA and ANZCA uses ‘Guidelines’. Further evaluation of these documents reveals nuances of language that are important to the practitioner. In particular, it is important to understand what is considered an absolute monitoring requirement for every anaesthetic vs. monitoring modalities that are useful but not essential. Reconciling the various approaches will require agreement on the implications of the terms used.

The EBA document defines ‘core standards’ for monitoring as to ‘be used whenever a patient is anaesthetised’.382 The WHO–WFSA uses a tiered approach.484 A ‘highly recommended’ standard is considered mandatory, that is, if not met, provision of anaesthesia for elective surgical procedures is unsafe and unacceptable. ‘Recommended’ and ‘suggested’ standards should be practiced ‘when resources allow and if appropriate for the healthcare being provided’.

The ASA Policy Statement on Practice Parameters provides detailed definitions of standards, guidelines and advisories (which can be either evidence or practice based) ( Evidence-based standards provide rules or minimum requirements and are regarded as generally accepted principles of patient management, may be modified only under unusual circumstances, are supported by meta-analyses of findings from multiple clinical trials and are agreed upon by all or nearly all expert consultants and surveyed ASA members. A standard is the most stringent recommendation. Failing to comply with a standard would constitute a practice breech and not only put the patient at risk but expose the provider to liability that would be difficult to defend if an adverse event occurred. Evidence-based practice guidelines provide recommendations that describe a basic management strategy supported by meta-analyses of multiple clinical trials and are agreed upon by a majority of expert consultants and surveyed ASA members. Finally, evidence-based practice advisories provide statements to assist decision-making in areas of patient care where there is not a sufficient number of adequately controlled studies to permit meta-analysis. Evidence-based practice guidelines and practice advisories are not intended to be standards or minimum requirements. The ASA Committee on Standards and Practice Parameters is one such committee that supervises the creation of new and revision of older practice parameters.

Inconsistent monitoring requirements

Keeping in mind the ‘semantic modifiers’ alluded to in the previous paragraph, we provide a brief review of the recommendations contained in the ‘standards’ from these different organisations. All societies require that every anaesthetised patient be continuously attended by a qualified anaesthesia professional and have requirements for clinical monitoring. All require alarms to be activated and audible, with limits properly applied. There are, however, differences in recommendations for individual parameters. For purposes of this discussion, the term ‘standard’ will be used to indicate an absolute requirement. Because ISO standards pertain to manufacturers of anaesthesia workstations but not clinicians, they are considered in a separate paragraph.


Blood oxygenation monitoring by pulse oximetry is a universal standard among all organisations. Monitoring of the inspired O2 concentration accompanied by a low threshold alarm is a standard for all except the WHO–WFSA document where it is ‘recommended’. Monitoring skin colour is a standard for all except the AAGBI and EBA who state it ‘may be included as an appropriate clinical observation’.383,482


All organisations surveyed require end-expired carbon dioxide (CO2) to be detected after intubation or supraglottic airway placement, and all but the WHO–WFSA require end-expired CO2 to be monitored thereafter. WHO–WFSA cites cost and lack of robustness as the reasons for only ‘recommending’ continuous CO2 monitoring. Qualitative assessment of ventilation (movement of chest and breathing bag, auscultation) is considered standard by WHO–WFSA, IFNA and EBA, but not by ASA, AAGBI, HKCA. According to ANZCA, ventilation ‘must be monitored continually’. Monitoring cuff pressure of airway devices is considered a standard by the AAGBI and HKCA, and so is inspired CO2 concentration monitoring (HKCA only). Standards for monitoring during mechanical ventilation differ: ASA ‘strongly encourages’ and WHO–WFSA ‘suggests’ expired volume be measured; all but ASA, ANZCA, IFNA and WHO–WFSA explicitly require airway pressure monitoring as standard; and a disconnection detector with alarm is a standard for all except the WHO–WFSA which ‘recommends’ it.


ECG, intermittent BP measurements and heart rate (HR) monitoring are consistent standards, except for the WHO–WFSA who only ‘recommends’ ECG for rhythm monitoring; ANZCA requires ECG monitoring ‘as clinically indicated’. In the AAGBI and EBA guidelines, HR monitoring is present implicitly in the ECG and pulse oximetry is a monitoring requirement. All guidelines require confirmation of a pulse [i.e. mechanical activity resulting in cardiac output (CO)] in the form of at least one of these: palpation of a pulse, auscultation of heart sounds, monitoring of a tracing of intra-arterial pressure, ultrasound peripheral pulse monitoring, or pulse plethysmography or oximetry (Table 20). The AAGBI and HLCA standards require a stethoscope ‘be available’. The IFNA standards also refer to end-expired CO2 as a means to monitor CO.

Table 20: Monitoring standards


Recommendations are inconsistent and range from ‘a means to measure temperature has to be available’ to ‘recommended’ to ‘essential for procedures more than 30 min’, to ‘when clinically significant changes in body temperature are intended, anticipated or suspected’. Temperature is not advocated as a standard to be adhered to throughout the entire procedure by any of the organisations except by the IFNA in paediatric patients and ANZCA ‘whenever warming devices are being used’.

Kidney function

Monitoring urine output is either not mentioned, or ‘suggested in appropriate cases’ (WHO–WFSA, AAGBI).

Neuromuscular transmission after administration of muscle relaxants

Recommendations range from being a standard (AAGBI) to not being mentioned (ASA) to variations in between. For example, the WHO–WFSA ‘recommends’ it, the EBA states that a nerve stimulator has to be available, and the HKCA states that ‘it should be used whenever the anaesthetist is considering extubation following the use of nondepolarising neuromuscular blockade’. The IFNA states that professionals should ‘measure, assess, and score neuromuscular function by a neuromuscular monitor (if available) when neuromuscular blocking agents are being used’.

Concentration of inhaled anaesthetics

Monitoring the end-expired concentration of inhaled anaesthetic agents is a standard for the AAGBI, EBA, ANZCA and the HKCA (the latter, in addition, requires automated agent detection). The WHO-WFSO ‘suggests’ both inhaled and exhaled concentrations to be measured. The ASA standards do not mention inhaled anaesthetic agent concentration monitoring. The IFNA recommends that both inspiratory and expiratory anaesthetic concentrations of volatile agents be measured continuously ‘if possible’.

Measure of drug effect on the central nervous system/unconsciousness

According to the HKCA, ‘When clinically indicated, equipment to monitor the anaesthetic effect on the brain should be applied, especially for patients at high risk of awareness, for example, those receiving total intravenous anaesthesia with a muscle relaxant’. The IFNA states that the application of an electronic device intended to measure cerebral function should be ‘considered’, particularly in cases with high risk of awareness under general anaesthesia. According to ANZCA, ‘When clinically indicated, equipment to monitor the anaesthetic effect on the brain should be available for use on patients, especially those at high risk of awareness, during general anaesthesia’. The WHO–WFSA states that its ‘use … while not universally recommended or used, is suggested, particularly in cases at risk of awareness under general anaesthesia or postoperative delirium’. The AAGBI recommends the ‘use of depth of anaesthesia monitors, for example processed EEG monitoring … when patients are anaesthetised with total intravenous techniques and neuromuscular blocking drugs, to reduce the risk of accidental awareness during general anaesthesia. However, there is no compelling evidence that routine use of depth of anaesthesia monitoring for volatile agent-based general anaesthetics reduces the incidence of accidental awareness when end-tidal agent monitoring is vigilantly monitored, and appropriate low agent alarms are set’. According to the EBA, ‘… their routine use has yet to be fully considered as part of our recommended minimum monitoring standards’. ASA does not consider EEG or EEG-derived indices in its Standards for Basic Anaesthetic monitoring.

International Organization for Standardization workstation standards

ISO workstation standards use the terms ‘shall, should and may’ to designate the degree of required compliance. ‘Shall’ indicates that compliance is mandatory, ‘should’ implies it is recommended but not mandatory and ‘may’ is used to describe a permissible way to achieve compliance. Mandatory monitoring recommendations for anaesthesia workstations include inspired O2 fraction monitoring with a low threshold alarm, quantification of respiratory volumes, capnography, and, during mechanical ventilation, airway pressure monitoring and a disconnection detector with an audible alarm. Anaesthetic agent monitoring is considered mandatory when inhalation agents are used. Since the ISO workstation standard applies to all devices used together to provide anaesthesia care, agent monitoring is not a required hardware component of the anaesthesia machine since separate free-standing devices for agent monitoring can be employed to be compliant.

To obtain regulatory approval (CE marking or Food and Drug Administration approval), manufacturers would be expected to comply with all essential requirements in the ISO standards, that is, those designated as ‘Shall’. For the recommendations designated as ‘should’ or ‘may’, regulatory approval will be influenced by the risk analysis required of the manufacturer as part of the regulatory submission.


The current brief review has identified a number of inconsistencies between the anaesthesia monitoring recommendations promoted by professional organisations in different parts of the world, and with manufacturing standards stipulated by ISO. In general, monitoring standards for parameters that describe the cardiopulmonary system are mostly consistent. This is less true for other physiological systems or for other aspects of the anaesthetic state like immobility or unconsciousness. In addition, ISO standards exceed certain monitoring requirements for which professional societies differ in opinion, for example, for tidal volume measurements and airway pressure monitoring during mechanical ventilation. As a result, ISO standards become de facto practice standards when using an ISO compliant anaesthesia workstation.

If safety is universal, why are recommendations not?

Published recommendations are developed by consensus within each organisation, so it is not surprising that the results are different around the world. For the developing world, professional organisations are sensitive to resource limitations and are reluctant to impose requirements that are difficult to comply with. Nevertheless, the importance of patient safety does not change by geography. The WHO–WFSA has made a major effort to reconcile guidelines by different societies and develop practical recommendations that can be followed anywhere in the world. In the developed world, the differences in recommendations are more difficult to understand as the resource constraints are not as significant.

Which important recommendations might merit reconciliation?

The recommendations for end-expired agent monitoring, anaesthetic depth monitoring and neuromuscular transmission monitoring are different from each organisation yet can be important tools for assessing anaesthetic effect and should be considered when thinking of aligning the various recommendations.

During surgery under general anaesthesia, the patient expects to be unconscious and to not experience pain. Both inhaled and intravenous agents are commonly employed to achieve that goal. When inhaled agents are used, end-expired anaesthetic agent monitoring can ensure that the inhaled anaesthetic agent is being delivered, and, in a dose that at least ensures unconsciousness.485 As noted above however, only four organisations consider end-expired agent monitoring a standard. WHO–WFSA ‘suggests’ that it be used whereas the ASA monitoring standard does not even mention inhaled agent monitoring. IFNA only recommend its use ‘if available’. In the authors’ opinion, sufficient rigorous scientific data exist to elevate end-expired anaesthetic agent monitoring to the status of standard. Three properties of inhaled agents provide the rationale for end-expired agent monitoring: the steep dose response curve of volatile anaesthetics; the small effect opioids have on this relationship [only a 10 to 15% reduction in minimal alveolar concentration (MAC) awake, the median anaesthetic level for patients to respond to verbal command]486; and the ease of continuous measurement of their concentration. The end-expired agent concentration is a good indicator of how likely it is the patient is unconscious after taking into account the short delay for the brain partial pressure to equilibrate with that in the blood and alveoli. With an expired concentration of 0.7 MAC, awareness is extremely unlikely.487,488 Fortunately, ISO workstation standards impose anaesthetic agent monitoring so all ISO compliant workstation configurations will offer anaesthetic agent monitoring either built into the anaesthesia machine or part of a bedside monitoring device. Practice recommendations from professional societies can provide guidance on the safety of proceeding with an inhaled anaesthetic if the agent-monitoring device is not functional.

When intravenous agents are used, we cannot assess the serum concentration quantitatively, so we are left with measures of drug effect such as processed EEG. Despite the technology limitations of processed EEG monitoring, more than one organisation (but not all) advocates that it be used, especially for patients at high risk for awareness. Whether or not the current technology for brain monitoring to assess anaesthetic depth is sufficiently robust to be a required monitor remains a matter of debate.489 Similarly, while there is inconsistency about requiring neuromuscular transmission monitoring when using neuromuscular blocking agents, it is notable that the Anesthesia Patient Safety Foundation clearly advocates for this requirement.490


The primary responsibility of the anaesthesia professional is to keep the patient safe. Resources, liability concerns, patient needs and clinical scenarios all play a role in determining the monitoring needs for any given patient. Standards provide a reference for practitioners and a guarantee to patients of a certain level of safety. We should seek to ensure that standards are as consistent as possible and provide common protections for all patients no matter where they live.

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