Plain English Summary
Background and study aims
Low blood pressure during surgery (also known as intraoperative hypotension or IOH) is thought to be very common. It happens as a side effect of the medicines used during anaesthesia (sedation during surgery). In patients aged over 65 years, this may lead to an increased risk heart attack, stroke, kidney failure and death following surgery. This risk increases as the degree and duration of low blood pressure increases. Patients aged over 65 years are at increased risk because their body is less able to cope with low blood pressure. Finding out how common IOH is can be difficult, as there is no clear and universally accepted definition. The purpose of this study is twofold. Firstly to determine how often low blood pressure occurs during operations in elderly patients in the UK and whether this is linked to a higher risk of complications. Secondly, to determine how and why anaesthetists treat low blood pressure during operations.
Who can participate?
Patients aged 65 years or older and having surgery under anaesthesia
What does the study involve?
Taking part in this study does not change the care patients would receive if they were not taking part. The researchers review the anaesthetic charts of participants undergoing surgery and record instances of IOH, as well as how serious it is and how long it lasts. Other key medical and background information is also recorded for each patient. Patients included in the study are followed up to assess their recovery up to 30 days after surgery. All information is obtained from patient records rather than face-to-face encounters. Anaesthetists, who looked after a participant, are given a questionnaire asking about individual practice in relation to the treatment of low blood pressure during surgery. The responses are collected and assessed to determine national consensus on this topic.
What are the possible benefits and risks of participating?
There are no notable benefits or risks involved with participating.
Where is the study run from?
University College Hospital and 200 of NHS hospitals (UK)
When is the study starting and how long is it expected to run for?
June 2015 to June 2017
Who is funding the study?
National Institute of Academic Anaesthesia (UK)
Who is the main contact?
Dr Alex Wickham
Dr Alex Wickham
Imperial School of Anaesthesia
+44 7734 819931
Intraoperative Hypotension in Elder Patients (IHypE): an observational study of intraoperative hypotension in patients aged over 65 in UK hospitals
The aim of this study is to determine how often low blood pressure occurs during operations in elderly patients in the UK and whether this is linked to a higher risk of complications, and to investigate how and why anaesthetists treat low blood pressure during operations.
West London & GTAC Research Ethics Committee, 09/08/2016, ref: 16/LO/1154
Observational; Design type: Cohort study
Primary study design
Secondary study design
Patient information sheet
See additional files
Specialty: Anaesthesia, perioperative medicine and pain management, Primary sub-specialty: Anaesthesia, Perioperative Medicine and Pain Management; UKCRC code/ Disease: Other/ General symptoms and signs
Patient Participants: No direct intervention is made as part of the study. Patient anaesthetic records are examined and data on pre-morbid health state and intraoperative blood pressure is collected. 30 day outcome data (mortality, troponin, creatinine and ischaemic stroke).
Anaesthetist participants: Anaesthetists who have anaesthetised a patient who meets the inclusion criteria will be asked to complete a short survey assessing their opinions on intraoperative hypotension in patients aged over 65 years.
Primary outcome measure
Proportion of elderly patients developing intraoperative hypotension (IOH), the percentage drop from baseline blood pressure and the duration of hypotension. IOH will be recorded from reviewing the patients anaesthetic chart within 24 hours of having surgery. Percentage drop from baseline will be calculated using baselines of pre-induction and pre-operative blood pressure and the lowest recorded value. Duration of IOH will be calculated as the time in minutes spent consecutively at or within 5mmHg of the lowest value recorded on the anaesthetic chart.
Secondary outcome measures
1. In hospital mortality at 30 days: assessed by review of the clinical record
2. Acute kidney injury within 7 days of surgery: defined as a postoperative creatinine increase ≥1.5 times the baseline value or ≥26.5μmol/L. Assessed by review of the clinical record
3. Myocardial injury: Defined as a postoperative troponin enzyme concentration within 7 days of surgery that is above the 99th percentile of the upper reference limit. Assessed by review of the clinical record
4. Stroke, defined as an ischaemic stroke reported from a computed tomography (CT) scan of the brain within 7 days of surgery. Assessed by review of the clinical record
5. Anaesthetist perceptions of and treatment thresholds for hypotension is determined by assessment of a questionnaire administered on the date of participant recruitment
Overall trial start date
Overall trial end date
Reason abandoned (if study stopped)
Participant inclusion criteria
1. Aged >65 years
2. Underwent general anaesthesia or regional anaesthesia either alone or in combination in an operating theatre
3. Emergency and elective surgery
Target number of participants
Planned Sample Size: 1700; UK Sample Size: 300
Participant exclusion criteria
1. Procedure requires cardiopulmonary bypass
2. The patient undergoes sedation alone (that is, not in combination with regional anaesthesia)
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
University College Hospital
University College London Hospitals NHS Foundation Trust Euston Road
University College London
Joint Research Office
+44 20 3447 7428
National Institute of Academic Anaesthesia
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
1. Planned presentation of selected abstracts from the study data at the British Journal of Anaesthesia/ Anaesthetic Research Society 2017 Spring meeting (London), Euroanaesthesia 2017 (Geneva) and the ANZCA ASM 2017 (Brisbane)
2. Planned publication in a high impact peer reviewed Anaesthetic journal by December 2017
IPD sharing statement:
The datasets generated during and/or analysed during the current study are not expected to be made available because the participants did not provide consent to disseminate participant level data.
Intention to publish date
Participant level data
Not expected to be available
Basic results (scientific)
- ISRCTN38968048_PIS_07Aug16_V2.2.pdf Uploaded 11/05/2017