Intraoperative hypotension frequently complicates anaesthesia and is associated with adverse outcomes in the elderly . In non-cardiac surgical populations it has been associated with increased risk of stroke , impaired neurological performance , myocardial injury , acute kidney injury [4, 5] and mortality [1, 6-8]. The longer hypotension persists, the greater the risk of injury .
Association of Anaesthetists of Great Britain and Ireland (AAGBI) guidelines recommend that intraoperative hypotension should be avoided in older patients , however recent evidence suggests that it remains extremely common. A 25 centre investigation in London identified that up to 89% of 481 patients aged over 65 fulfil the AAGBI definition of hypotension and that it is often prolonged, persisting for over 20 minutes in 28% . The recent national AAGBI ASAP audit emphasised the large scale of this issue and potential burden of harm in the fractured neck of femur population .
Whilst optimal patient-specific blood pressure limits may exist, predicting these is not straightforward, and there is continued debate over appropriate population based definitions [12-14]. Thus \"intraoperative hypotension\" might range between an inadvertent or undertreated event, to different interpretation of an individual patient's requirements. The aim of this investigation is to audit the incidence of intraoperative hypotension in the elderly, and importantly, identify treatment thresholds and attitudes towards hypotension. Crucially this will deliver a snapshot of UK anaesthetic practice which will complement emerging research on intraoperative hypotension to inform improvement.
- To determine how frequently intraoperative hypotension occurs in elderly patients in comparison to the AAGBI standard.
- To determine anaesthetists perceptions of and treatment thresholds for hypotension by:
- Identifying blood pressure thresholds triggering vasopressor use.
- Surveying anaesthetist attitudes towards intraoperative hypotension.
- Inform an improvement strategy based on objectives 1 and 2.
There is considerable established and emerging work on the clinical relevance of intraoperative hypotension in the elderly, and this work will assist translating these findings into clinical practice by establishing the status of current practice.
The prevalence of intraoperative hypotension depends on the threshold used (relative reduction or absolute value) and component (systolic, diastolic or mean pressure), there being no universally agreed definition. We have chosen to use the AAGBI definition of intraoperative hypotension (taken from the AAGBI Safety Guideline Peri-operative Care of the Elderly 2014 ) as this is a suitably cautious physiological value for the older patient set by a national organisation that produces robust guidance. The guideline recommends that hypotension, including prolonged hypotension, be prevented.
The standard is: \"a fall in systolic blood pressure of more than 20% from pre-induction baseline... is a suitable limit.\"
Prospective two day snapshot audit
- Age >65
- General anaesthesia ± regional anaesthesia
- Cardiac surgery or other procedure requiring cardiopulmonary bypass
- Sedation only
- Will be delivered by regional trainee led research groups affiliated to the Research and Audit Federation of Trainees (RAFT).
- Data collection will take place over two weekdays between 0800hrs and 2000hrs in February 2016
- 1-2 volunteer anaesthetic trainees, independent of delivery of anaesthesia, will collect data from anaesthetic charts whilst patients are in recovery, or after lists on the same day.
- Paper proformas (see appendix 1 and 2) will be used to collect intraoperative blood pressure data.
- A survey (adapted from Burns SM et al ), will be given to anaesthetists whose patients were included in the project asking about definitions of and attitudes towards intraoperative hypotension.
- If more than one anaesthetist was present in theatre (e.g. a consultant and trainee), both will be asked to complete the survey.
- Data will be entered onto a pre-prepared excel spreadsheet.
- Are detailed in appendix 1 (intraoperative hypotension data) and 2 (anaesthetist survey)
- Individual trust spreadsheets will be collated centrally via nhs.net email to a central data collector.
- Retrospective analysis of electronic patient record.
- The variables to be assessed are derived from Walsh et al.  and will include:
- Renal injury:
- Defined by the difference between preoperative and postoperative creatinine values.
- Preoperative value: creatinine value measured closest to the time of surgery.
- Postoperative value: the highest creatinine concentration measured within 7 days of surgery.
- Patients will be considered to have Acute Kidney Injury if the highest postoperative creatinine had increased ?50% (1.5 fold) from baseline or ?26.4?mol/L (AKIN network definition ).
- If no creatinine test is performed, patients will be assumed to not have renal injury.
- Myocardial injury:
- Defined as a postoperative cardiac enzyme concentration within 7 days of surgery that is above the 99th percentile of the upper reference limit . The exact limit is dependent on the assay manufacturer.
- If no cardiac enzyme test is performed, patients will be assumed to not have myocardial injury.
- Extrapolating from findings in London , we predict the investigation will obtain data on ~3000 patients.
- Key results to obtain include:
- The incidence, depth and duration of hypotension compared with the AAGBI standard
- Blood pressure values triggering vasopressor use
- Anaesthetists perceptions of hypotension and management strategies
- Adverse outcomes associated with hypotension.
- Descriptive statistics will be used to describe national rates of AAGBI defined intraoperative hypotension, degree of hypotension and duration.
- The survey will be analysed using descriptive statistics, frequencies and one and two way tables. The intraoperative data will be compared to the survey data to identify any differences between practice and perceptions.
- Clinical governance:
- Discussion with Imperial College Healthcare NHS Trust Clinical Governance has confirmed this project meets the criteria for audit.
- Written confirmation of local clinical governance approval will be required prior to acceptance of data from any individual trust.
- Information governance:
- Data will be collected in individual hospitals on paper and then inputted onto a excel spreadsheet.
- No personal identifiable information will be transferred outside individual trusts.
- The data will be collated centrally at Imperial College Hospitals in an excel file (see below for data storage information).
- To ensure security, all data transfer between hospital trusts will take place via nhs.net (fully encrypted) e-mail.
- All data analysis will take place password protected trust desktops.
- Ethical considerations:
- This is an audit, no interventions or alterations to normal care are being made. No allocations or randomisation is to be made.
- As the aim is to improve intraoperative care and perioperative outcomes for elderly patients, we do not foresee any ethical problems.
Impact and study outputs.
The key intended outputs delivered from this audit project are:
- Document the national incidence of intraoperative hypotension in non-cardiac surgical populations.
- Elucidate anaesthetists' threshold for treating hypotension and compare this to their stated clinical opinion on treatment thresholds.
- Differentiate 'inadvertent hypotension' from disagreement with the AAGBI definition and suboptimal management.
The information gained from this will be valuable for a number of reasons:
- It will deliver the first national picture of the prevalence of intraoperative hypotension in the elderly, a problem linked to increased morbidity and mortality.
- A nationwide survey of anaesthetists perceptions of hypotension, in combination with the above results will provide a starting point from which to effect change.
- Publication will complement other planned studies (from different research/ audit groups) looking at intraoperative hypotension in hip fracture patients and the effect of hypotension on post-operative delirium.
Improving practice based on findings:
- The information gained will be presented and published to stimulate national and local debate on the importance of intraoperative hypotension and how best to address the problem.
- Individual departments will receive their results with comparisons against national figures to allow local quality improvement programmes.
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