The next annual RAFT project will look at Intraoperative Hypotension in the Elderly (iHypE). Intraoperative hypotension frequently complicates anaesthesia and has been associated with multiple adverse outcomes, particularly in the elderly.

The aim of iHypE is to assess the incidence of intraoperative hypotension in the elderly, document associated outcomes, identify treatment thresholds and attitudes towards hypotension. This trainee-led project will also deliver a snapshot of UK anaesthetic practice which will complement emerging research on intraoperative hypotension to direct quality improvement strategies.

The project follows on from The Pan London Perioperative Audit and Research Network's QUINCE project which audited the quality of intraoperative cerebral protection in London and found significant rates of intraoperative hypotension.

iHypE was accepted by vote at the GAT ASM in June 2015. An ambitious project, RAFT hopes that it will be a great opportunity for trainees to collaborate nationally and share the experiences learned in the individual regions. The project has already generated much enthusiasm with suggestions from across RAFT and the HSRC. Twelve of the 15 trainee research networks, incorporating approximately 140 hospitals across the UK, have now confirmed they will recruit patients. Data will be collected in the spring/summer period of 2016. If you are interested in taking part, please contact your local trainee network, or if you don't have a network or would like further information please visit the iHype or RAFT websites.

Introduction

Intraoperative hypotension frequently complicates anaesthesia and is associated with adverse outcomes in the elderly [1]. In non-cardiac surgical populations it has been associated with increased risk of stroke [2], impaired neurological performance [3], myocardial injury [4], acute kidney injury [4, 5] and mortality [1, 6-8]. The longer hypotension persists, the greater the risk of injury [4].

Association of Anaesthetists of Great Britain and Ireland (AAGBI) guidelines recommend that intraoperative hypotension should be avoided in older patients [9], 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% [10]. 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 [11].

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.

Objectives

  1. To determine how frequently intraoperative hypotension occurs in elderly patients in comparison to the AAGBI standard.
  2. To determine anaesthetists perceptions of and treatment thresholds for hypotension by:
    1. Identifying blood pressure thresholds triggering vasopressor use.
    2. Surveying anaesthetist attitudes towards intraoperative hypotension.
  3. 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.

Standards

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 [9]) 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.\"

Methods

Design

Prospective two day snapshot audit

Audit population

    Inclusion:
    • Age >65
    • General anaesthesia ± regional anaesthesia
  • Exclusion:
    • Cardiac surgery or other procedure requiring cardiopulmonary bypass
    • Sedation only

Data collection

  • 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 [15]), 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.

Parameters recorded

  • Are detailed in appendix 1 (intraoperative hypotension data) and 2 (anaesthetist survey)

Data collation

  • Individual trust spreadsheets will be collated centrally via nhs.net email to a central data collector.

Clinical outcomes:

  • Retrospective analysis of electronic patient record.
  • The variables to be assessed are derived from Walsh et al. [4] and will include:
    • Mortality
    • 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 [16]).
      • 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 [17]. 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.

Analysis

  • Extrapolating from findings in London [10], 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.

Governance

  • 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:

  1. Document the national incidence of intraoperative hypotension in non-cardiac surgical populations.
  2. Elucidate anaesthetists' threshold for treating hypotension and compare this to their stated clinical opinion on treatment thresholds.
  3. 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:

  1. It will deliver the first national picture of the prevalence of intraoperative hypotension in the elderly, a problem linked to increased morbidity and mortality.
  2. A nationwide survey of anaesthetists perceptions of hypotension, in combination with the above results will provide a starting point from which to effect change.
  3. 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:

  1. 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.
  2. Individual departments will receive their results with comparisons against national figures to allow local quality improvement programmes.

References

  1. Bijker JB, van Klei WA, Vergouwe Y, Eleveld DJ, van Wolfswinkel L, Moons KG, Kalkman CJ. Intraoperative hypotension and 1-year mortality after noncardiac surgery. Anesthesiology 2009; 111: 1217-26.
  2. Bijker JB, Persoon S, Peelen LM, Moons KG, Kalkman CJ, Kappelle LJ, van Klei WA: Intraoperative hypotension and perioperative ischemic stroke after general surgery: A nested case-control study. Anesthesiology 2012; 116: 658-64
  3. Yocum GT, Gaudet JG, Teverbaugh LA, Quest DO, McCormick PC, Sander Connelly Jr S, Heyer EJ. Neurocognitive Performance in Hypertensive Patients after Spine Surgery. Anesthesiology 2009; 110(2): 254-261
  4. Walsh M, Devereaux PJ, Garg AX, Kurz A, Turan A, Rodseth RN, Cywinski J, Thabane L, Sessler DI: Relationship between intraoperative mean arterial pressure and clinical outcomes after noncardiac surgery: Toward an empirical definition of hypotension. Anesthesiology 2013; 119: 507-15.
  5. Sun LY, Wijeysundera DN, Tait GA, Beattie WS. Association of Intraoperative Hypotension with Acute Kidney Injury after Elective Noncardiac Surgery. Anesthesiology 2015; 123: 00-00.
  6. Monk TG, Saini V, Weldon BC, Sigl JC: Anesthetic management and one-year mortality after noncardiac surgery. Anesthesia & Analgesia 2005; 100: 4-10.
  7. Monk TG, Bronsert MR, Henderson WG, Mangione MP, Sum-Ping STJ, Bentt DR, Nguyen JD, Richman JS, Meguid RA & Hammermeister KE. Association between Intraoperative Hypotension and Hypertension and 30-day Postoperative Mortality in Noncardiac Surgery. Anesthesiology 2015; 123: 307-19.
  8. Mascha EJ, Yang D, Weiss S & Sessler DI. Intraoperative Mean Arterial Pressure Variability and 30-day Mortality in Patients Having Noncardiac Surgery. Anesthesiology 2015; 123: 79-91.
  9. Griffiths R, Beech F, Brown A, Dhesi J, Foo I, Goodall J, Harrop-Griffiths W, Jameson J, Love N, Pappenheim K and White S. AAGBI working party: Peri-operative care of the elderly 2014. Anaesthesia 2014, 69 (Suppl. 1), 81-98.
  10. Wickham A & the Pan London Perioperative Audit and Research Network (PLAN). The quality of intraoperative cerebral protection in the elderly: an audit of London practice. Anaesthesia 2015; 70 (s2): 5-44.
  11. ASAP collaboration team. Falls and Fragility Fracture Audit Programme of the National Hip Fracture Database: Anaesthesia Sprint Audit of Practice 2014. 2014. Royal College of Physicians: London.
  12. Bijker BJ, van Klei Wa, Kappen TH van Wolfswinkel L, Moons KGM, Kalkman CJ. Incidence of Intraoperative Hypotension as a Function of the Chosen Definition. Anesthesiology 2007; 107: 213-20
  13. Warner MA & Monk TG. The impact of lack of standardised definitions on the speciality. Anesthesiology 2007; 107: 198-9.
  14. Brady K & Hogue CW. Intraoperative hypotension and patient outcome. Does one size fit all? Anesthesiology 2013; 119: 495-7.
  15. Burns SM, Cowan CM, Wilkes RG. Prevention and management of hypotension during spinal anaesthesia for elective Caesarean section: a survey of practice. Anaesthesia. 2001; 56(8):794-8.
  16. Mehta R, Kellum J, Shah S, Molitoris B, Ronco C, Warnock D, Levin A, AKINetwork: Acute Kidney Injury Network: Report of an Initiative to Improve Outcomes in Acute Kidney Injury. Critical Care 2007, 11:R31 (doi:10.1186/cc5713).
  17. Thygesen K, Alpert JS & White HD on behalf of the Joint ESC/ACCF/AHA/WHF Task Force for the Redefinition of Myocardial Infarction. Universal definition of myocardial infarction. European Heart Journal 2007, 28; 2525-2538.

Regional Leads

AARMY IT lead since 2015. iHypE and DALES EAST Yorkshire lead.
Consultant Committee Member iHypE West Yorkshire Lead