Increasing demands on the provision of anaesthetic services have been met with greater patient safety. While the primary determinant of anaesthetic safety is the presence of trained and experienced anaesthetists, human error remains unavoidable.1 Rather than prevent adverse incidents, patient monitoring may reduce the risk of harm by detecting and alerting the caregiver to a change in patient condition, thereby increasing the margin of safety.2-4
The Association of Anaesthetists of Great Britain and Ireland (AAGBI) has championed a multitude of safety standards, and the latest update on the anaesthesia standards of monitoring5 details practical and invaluable guidance to be implemented by both individual practitioners and institutions. While the 2015 recommendations are an update and replacement of the 4th edition of the guidelines, it provides a contemporary model to include modern technological and service provision advancements.
The anaesthetist’s presence during anaesthesia
During all forms of anaesthesia, including all periods of general anaesthesia, sedation, local or regional anaesthesia, an appropriately experienced anaesthetist must be present at all times. Trained Physician Assistants (Anaesthesia) (PA (A)) have recently been introduced into UK clinical practice, and can fulfil the requirement of anaesthetic presence under the supervision of a consultant anaesthetist. In patients who are not sedated, having local or peripheral nerve block techniques, this responsibility may be delegated to trained, competent, non-physician healthcare workers.6 Circumstances posing a potential hazard to the anaesthetist may arise during certain radiology and radiologically-assisted procedures, in which case, remote observation and monitoring facilities must be available.
Documentation at a minimum time interval of five minutes is recommended for heart rate, blood pressure, peripheral oxygen saturation, end-tidal carbon dioxide and, if anaesthetic gases are used, end-tidal vapour concentration. There is now a plethora of electronic anaesthetic record systems,7 and the uptake and use of such devices by departments is encouraged.
Handover of patient care under anaesthesia is an unavoidable inevitability at times, but efforts should be kept to minimise this process. If handover is to occur, the AAGBI recommends that a detailed handover that follows a checklist such as the ‘ABCDE’ 5th National Audit Project (NAP5) anaesthesia checklist,8 with all handovers documented in the anaesthetic record. Included in the handover should be a further check to ensure adequate provision of monitors and appropriate alarm limits are set.
In the event that a solo anaesthetist is called to perform or assist with a critical, life-saving procedure nearby, another anaesthetist, a trained PA (A) or, if neither is available, a trained anaesthetic assistant should be present to continue patient and monitoring observation. The AAGBI advises that departments should strive to have an experienced anaesthetist, either consultant or senior registrar, available to cover these potential eventualities. On the less time-critical end of the spectrum, adequate fatigue management9 for solo anaesthetists during long surgical procedures should be planned for with the presence of experienced anaesthetists in the theatre suite.
Anaesthetic equipment
Any item of equipment used by an anaesthetist should be familiar and appropriately checked prior to use.10
Oxygen supply
Continuous monitoring of delivered gas mixtures with an oxygen analyser should be used and must be checked and established, with audible alarms set to verified alarm limits.
Breathing systems
Continuous waveform carbon dioxide concentration monitoring (capnography) is mandatory for all unconscious patients irrespective of location, including in patients with tracheal tube, supraglottic airway devices, or moderately deeply sedated patients.11
Vapour analysers
Whenever volatile anaesthetic agents or nitrous oxide are used, vapour analysers must be used and end-tidal concentrations recorded.
Infusion devices
If an infusion device is to be used for any aspect of anaesthetic care, it must be checked before use, with appropriate infusion limits and alarm settings verified. The device should be connected to mains power and infusion lines connected to an intravenous cannula should ideally be observed throughout the duration of their use.
It is recommended that a depth of anaesthesia monitoring device is used whenever an anaesthetic is administered solely via the intravenous route in combination with the use of neuromuscular blocking drugs.
Alarms
Departmental agreement on alarm limits is recommended, and provision, maintenance, calibration and renewal of equipment are institutional responsibilities. However, all alarms should be set, reviewed and audibility checked by the individual anaesthetist before commencing use. Airway pressure alarms are included, particularly when positive pressure ventilation is to be used.
Monitor displays
The configuration of display set up should be considered before commencing anaesthesia. Non-invasive blood pressure (NIBP) monitors should be set at a time interval of at least every five minutes, with readings not remaining on display for longer than this interval.
Device monitoring
Cuff pressures of tracheal tubes and supraglottic airway devices should be monitored with manometers to reduce airway morbidity and improve the performance of the device.12
Patient monitoring
The use of patient monitoring devices should act to supplement clinical observation, for which the availability of a stethoscope is recommended at all times. For the safe conduct of anaesthesia, the minimum monitoring recommended by the AAGBI includes:
- Pulse oximeter
- NIBP
- ECG
- Inspired and end-tidal oxygen, carbon dioxide, and nitrous oxide and volatile agents if used
- Airway pressures
- Peripheral nerve stimulator if neuro-muscular blockade is undertaken
- Temperature if duration of anaesthesia is >30 minutes.
Monitoring must commence as soon as feasibly possible before induction of anaesthesia and commence until full recovery from anaesthesia. Any circumstances necessitating an absence of one or more monitor(s) must be documented.
Recovery from anaesthesia
Full recovery is defined as a patient who no longer requires airway support, is spontaneously ventilating, alert, responsive and, when appropriate, speaking. It is recognised that the period of transfer from theatre to recovery represents an increase in risk, and it is therefore recommended that departments provide the same minimum monitoring as above, particularly if airway devices remain in situ. Supplemental oxygen should always be administered at least until full recovery from anaesthesia.
The AAGBI has also introduced guidelines for the monitoring of patients in the immediate post-anaesthesia recovery period,13 and this includes monitoring:
- Pulse oximeter
- NIBP
- ECG
- Capnography if an airway device is in situ or deeply sedated
- Temperature monitoring.
Additional monitoring
Cardiac output monitoring
The most accurate cardiac output monitor is the pulmonary artery catheter, but the AAGBI no longer recommends the routine use of this device anywhere but specialist cardiac surgical centres. A plethora of less invasive devices is now available, but the accuracy of most devices is debatable and no single device can be recommended over another. However, cardiac output monitors may have a role to play in assessing fluid responsiveness, with some evidence supporting their application for this purpose. The use of echocardiography is also recognised as an alternative for estimating cardiac function and fluid status. Whichever device or technique is used, training of anaesthetists using them is imperative.
Depth of anaesthesia monitoring
Although there are limited data demonstrating a reduction of accidental awareness during general anaesthesia (AAGA), depth of anaesthesia monitors may supplement clinical information. The incidence of AAGA is highest when neuromuscular blocking drugs are used with total intravenous anaesthesia (TIVA),8 therefore the AAGBI recommend using these monitoring devices in this clinical setting in particular.
When used, depth of anaesthesia monitoring should commence at induction of anaesthesia until the end of surgery and anaesthesia.
When maintaining anaesthesia with inhalation anaesthetic agents, end-tidal anaesthetic vapour monitoring is recommended with low agent alarms set. The isolated forearm technique may also be used,14 but care interpretation and management must be taken.
Neuromuscular blockade monitoring
The use of neuromuscular blocking drugs mandates monitoring from induction through to full recovery of blockade and consciousness. Older, qualitative peripheral nerve stimulators are less reliable and the AAGBI encourages replacing these older devices with more objective quantitative monitoring devices. Ideally, quantitative monitoring using train-of-four assessment, with a ratio of >0.9 representing a return of motor function, should be used. Stimulation of the ulnar nerve in particular is ideal, however the facial or posterior tibial nerves are alternatives. The importance of neuromuscular blockade monitoring can be appreciated by the finding of residual neuromuscular blockade in up to 40% two hours after administration, and the high risk of both AAGA8 and postoperative pulmonary complications associated with their use.
Regional anaesthesia and sedation for operative procedures
As a minimum, the AAGBI recommends that patients having regional anaesthesia procedures require pulse oximeter, NIBP, ECG and, if sedated, end-tidal carbon dioxide monitoring. The AAGBI recommends that patients be monitored with capnography whenever an anaesthetist administers sedation, in any situation or location that this may occur.
Monitoring during intra-hospital transfer
As previously noted, any anaesthetised or sedated patient should have the same standard of monitoring throughout transfer, be it within hospital or without.15 Before transfer, physiological status should be optimised, a sufficient oxygen supply to last the entire duration of transfer should be checked, and a pre-transfer checklist8 should be used. Monitors must include pulse oximetry, NIBP and ECG for all patients, as well as end-tidal carbon dioxide, airway pressure, tidal volumes and respiratory rate in anaesthetised and ventilated patients. Although portable depth of anaesthesia monitors are not broadly available yet, the AAGBI suggests that if available they should also be applied as a standard of monitoring for patient transfers when TIVA is being used.
Anaesthesia outside the operating theatre
Irrespective of location, the AAGBI recommends the same minimum standards of monitoring depending on whether general anaesthesia, regional anaesthesia or sedation.
Conclusions
The 2015 standards of monitoring during anaesthesia and recovery is a landmark guideline that builds upon previous recommendations. The use of capnography in all areas of anaesthetic care, from sedation, to intra-hospital transfer, and during recovery/waking up from anaesthesia or sedation, is a progressive development in response to a number of studies demonstrating the utility of this monitor. The data from NAP58 has stimulated encouragement for the use of both depth of anaesthesia monitors and a more continuous
use of neuromuscular blockade monitors.
The recommendations also outline a minimum standard of monitoring in a wide range of clinical scenarios (Table 1), and describes the value of cardiac output monitors in the assessment of fluid responsiveness. By implementing the recommendations made in this safety guideline, anaesthetists and departments are best positioned to deliver safe anaesthesia irrespective of location.
References
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