How low do you go? An investigation of treatment thresholds for intraoperative hypotension in elder patients in the UK.

Wickham A1, Highton D2, Clark S3, Fallaha D4, Martin D2, Research & Audit Federation of Trainees (RAFT)
1 Imperial College Healthcare NHS Trust, London, UK; 2 University College London, London, UK; 3 Oxford University Hospitals, Oxford, UK; 4 Golden Jubilee National Hospital, Glasgow, UK

Background and Goal of Study: Intraoperative hypotension (IOH) is common in elder patients [1] and is associated with morbidity and mortality [2, 3]. Haemodynamic manipulation has the potential to reduce this burden, but there is no consensus definition of IOH, and thus treatment thresholds. This study aims to identify the target for IOH therapy commonly applied in UK anaesthetic practice.

Materials and Methods: Ethical approval was granted. Conducted as part of a larger study on IOH by the Research and Audit Federation of Trainees (RAFT), a national trainee research group. Using paper questionnaires administered by local trainees, we surveyed all anaesthetists, who provided general or regional anaesthesia to patients’ aged ≥65 years old over a 48 hour weekday period, about the IOH targets that would trigger intervention.

Results and Discussion: 2643 anaesthetists were surveyed from 147 centres. The majority of respondents were consultants (59.2%) or registrars (15.0%). Systolic (1863, 70.7%) and mean (2098, 79.7%) blood pressures were most frequently used to titrate vasopressor therapy. Stated blood pressure targets are summarised in table 1.
Blood Pressure Target	N (%) using target	Median value (25th – 75th quartile) triggering vasopressor use
Systolic BP	Absolute value	1832 (69.3%)	90.0mmHg (80.0 – 95.0)
	Relative reduction (%)	1929 (73.0%)	20.0% (20.0 – 30.0)
Mean BP	Absolute value	1597 (60.4%)	60.0mmHg (55.0 – 65.0)
	Relative reduction (%)	1365 (48.4%)	20.0% (20.0 – 20.0)

Conclusion: The majority of anaesthetists use a combination of targets, both absolute and relative, to trigger IOH therapy. There appears to be an inconsistency between the favoured 20% relative drop and the median absolute targets, which approach the limits associated with increased morbidity. This suggests that although anaesthetists may recognise a need for tighter, individualised treatment of IOH in older patients (via a small relative drop of 20%), it may not always be applied. Adherence to a relative target may have future potential to avoid IOH in older patients.

References:
1.	Wickham A et al. Care of elderly patients: an audit of hypotension. Periop Med 2016;5:12.
2.	Walsh M et al. Intraoperative mean arterial pressure and outcomes. Anesthesiology 2013;119:507.