Hypertension: is it a peri‐operative or a public health problem?

As consultant anaesthetists who have weekly sessions in a pre-operative assessment clinic, we read with great interest the consensus statement on hypertension in patients having elective surgery from the AAGBI and the British Hypertension Society 1. Although day of surgery cancellations are infrequently due to clinical reasons, hypertension is the commonest avoidable medical indication for postponement of elective surgery 2. For a condition that may affect up to 47% of patients presenting for surgery 3, there is little in the way of published evidence or guidelines concerning the blood pressure threshold (if indeed one exists) at which surgery should be deferred. As a result, there is a great variability between individual anaesthetists as to what degree of hypertension constitutes an excessive risk for elective surgery 2 which can be a cause of frustration and confusion amongst patients, pre-operative assessment practitioners and surgical colleagues. Consequently, clinical anaesthetists will welcome these guidelines; however, elements of the guidance do represent a sea change in certain aspects of peri-operative practice, which are likely to be debated at both national and departmental anaesthetic meetings. We have chosen three areas to discuss within this editorial. The key aspect of the entire pre-operative assessment process is the identification of pathologies and comorbidities that are associated with an increase in peri-operative morbidity and mortality. Some of these conditions will not be amenable to modification (e.g. chronic disease states that are already optimally or maximally managed), but early identification will allow an individualised risk assessment to made, aiding the decision making process for both patients and surgical teams. Conversely, other conditions may be perceived as having some room for further optimisation, and this has traditionally resulted in delays before surgery and referrals to other medical specialities in an attempt to reduce the risks associated with surgery. However, there is an increasing realisation that this pre-operative optimisation is a not always associated with a meaningful reduction in postoperative morbidity and mortality, even when the underlying physiological principles appear sound. For example, elective coronary artery revascularisation before major vascular surgery is not associated with long-term outcome benefits 4, and the link between poor long-term glycaemic control and increased postoperative complications has also recently been questioned 5. Hypertension is a common and (largely) treatable condition, but a meta-analysis of 30 observational studies suggested that an arterial blood pressure < 180 mmHg systolic or 100 mmHg diastolic was not associated with any increase in peri-operative complications 6. This meta-analysis, however, focussed primarily on major cardiovascular complications such as myocardial ischaemia/infarction, arrhythmias, and cerebrovascular accidents. A recent editorial in this journal also discussed the perceived risk of hypertension using similar endpoints 7. The impact of hypertension on complications and patient outcomes specific to individual surgical procedures, however, remains unclear. Postoperative hypertension remains a fear of several surgical specialities, most notably thyroid, ophthalmic and neurological surgery, all of which are included within the consensus statement. Hypertension has been implicated in the development of intra- and postoperative haemorrhage in neurosurgery and as such, hypertension is recommended to be ‘optimally managed’ pre-operatively and avoided in the peri-operative period 8. Similarly, systolic hypertension has been identified as an independent risk factor for haemorrhage after thyroid surgery 9, and for the development of delayed suprachoroidal haemorrhage after glaucoma and cataract surgery 10, 11. No precise thresholds have been suggested in the literature regarding a cut-off in terms of the risk of postoperative bleeding; however, it would seem reasonable that the surgical team is informed of patients who are hypertensive, so an individualised risk assessment can be made on a case-by-case basis. A recent editorial has highlighted the uncertainties surrounding the level of peri-operative risk associated with hypertension, and to what degree this could modified by therapeutic intervention 12. Further adequately powered research involving the analysis of large datasets is required in order to establish the precise association between pre-operative blood pressure readings and postoperative outcomes. If we accept that anaesthetists should now adopt a more relaxed approach to peri-operative hypertension, we must now consider whether these new guidelines will meet the needs of the patients from a public health perspective. Both authors work regularly in a centralised, integrated, pre-assessment clinic. Across the city of Sheffield, the service sees 26 000 patients a year, from a majority of surgical specialties, and we work with an ethos that not only is pre-operative assessment there to serve the needs of the hospital admission, but it can provide opportunistic screening and intervention. The surgical cohort are essentially ‘selected’ from the wider population due to the presence of one of more disease processes, and as such has a higher incidence of comorbidities. Some patients may be motivated to consider and adopt changes in health behaviour by impending surgery – and, where possible, we seek to capitalise on this for both short- and long-term gains. The first recommendation, that elective surgical referral should be made with hypertension controlled to < 160/100 mmHg is greatly welcome; this reflects a shift towards the concept of patients being ‘fit for referral’, as described in the Guidelines for the Provision of Anaesthetic Services (GPAS) 13, and aligns with recent multidisciplinary guidance on the peri-operative management of diabetes 14. However, the recommendation that potentially only a single blood pressure reading within the last 12 months is all that is required to ensure the control or absence of hypertension, appears a difficult concept to accept. Instinctively, this timescale appears generous, especially from an anaesthetic perspective when, for all but minor surgery in a fit patient, recent blood tests and ECG would be requested pre-operatively by many clinicians. Surgical referral can be indicative of a state of flux in the patient's health, making reliance on information obtained many months ago potentially hazardous. The evidence for optimal screening intervals to detect hypertension in the previously normotensive person is relatively sparse. The current UK recommendation to measure blood pressure at least every five years does not appear to have a robust evidence base 15. Both the United States and Canada, who outperform the UK in regard to effective diagnosis and management of hypertension, have selected shorter intervals; the United States suggests biannual checks if normotensive and annual checks if blood pressure is in the pre-hypertensive range 16. The question of the shortest interval in which hypertension can develop was specifically considered for the United States recommendation. In unselected populations, 2.2-4.4% convert from normotension to hypertension at one year, with higher conversion rates seen in older persons, those with pre-hypertension and overweight and obese people. These latter groups are at particular risk, with a hypertension conversion rate of up to 7.6% of patients with a body mass index greater than 30 kg.m−2 17. Canadian guidance goes a step further, and recommends measuring a person's blood pressure at every appropriate primary care visit 18, given the potential value of detecting hypertension and the lack of evidence of harm associated with this screening. A further consideration is the issue of masked hypertension, which has a similar prevalence to white-coat hypertension. Masked hypertension may affect around one in eight people who demonstrate normotension in primary care but who will be found to be hypertensive on ambulatory or home measurements. This population has increased rates of target end-organ damage and a cardiovascular risk comparable to typical hypertensive patients 19. A high index of suspicion, particularly in the sedentary, obese, diabetic, and those with kidney disease, is required in order to institute ambulatory monitoring. A thorough pre-operative assessment (including a blood pressure reading and ECG) can elicit this sub-group for diagnostic work up in the community, helping to address the disease burden. The relevance of this issue may seem limited to peri-operative care and pre-operative assessment. However, the wider context of hypertension being a public health priority needs consideration, particularly given the mandate for services to work more effectively together and the increase in the role of anaesthetists as peri-operative physicians 20. Public Health England estimates 7000 lives and £120 million ($180 million; €163 million) could be saved in ten years with better detection of hypertension 21. A key approach in this strategy is for more frequent opportunistic testing in primary care. The consultation that leads to referral to any surgical clinic, on any care pathway, seems an ideal moment for opportunistic blood pressure measurement in this context. This places substantial pressure on the primary care consultation (which lasts on average approximately 11 minutes 22), particularly if other aspects of ‘fit for referral’ also need consideration. Conversely, within our institution, a full pre-operative assessment appointment allows patients on average 50 minutes face-to-face contact with trained nursing staff 23. Patients who attend often view this as a global health check-up and, with this luxury of time, we would argue that pre-operative assessment is an ideal opportunity to ensure accurate, repeated blood pressure measurements, taken according to national guidance, and delivered alongside other important health screening interventions such as informing patients of their BMI and offering referral for smoking cessation. We view this information as belonging to the whole team involved with the patient's care, and frequently relay blood pressures to general practitioners, without presuming to declare the patient hypertensive. In the event that treatment is required, the opportunistic blood pressure reading may allow the earlier institution, and if needed escalation, of antihypertensive drug therapy. This is important, as even short delays in treatment intensification of one to three months disadvantages patients in the community, exposing them to an increased risk of cardiovascular events 24. Therefore, we believe that pre-operative assessment clinics should continue to routinely measure blood pressure, as this low-cost, non-invasive intervention has the potential to benefit patients both during their short-term peri-operative admission and over a longer period of time following discharge back to the community. The consensus recognises that treatment should be based on cardiovascular risk rather than a threshold figure, but it appears likely that patients with blood pressures below 160/110 mmHg will be considered as being fit for surgery. However, the results of the recent SPRINT trial may mean such figures will be re-appraised in the future. In this study of participants with an increased cardiovascular risk, antihypertensive treatment targeted to a systolic blood pressure < 120 mmHg resulted in a mortality benefit, when compared to a target of < 140 mmHg 25. Work has also suggested that intensive treatment of patients with grade 1 hypertension may reduce cardiovascular mortality 26. A recent meta-analysis involving over 600 000 patients, in 123 trails, supports this assertion, with a decrease in cardiovascular risk seen with the treatment of hypertension to a target systolic blood pressure of < 130 mmHg across a range of baseline blood pressure values 27. In conclusion, it is our belief that this consensus statement will benefit all those involved in the peri-operative process: anaesthetists finally have some guidance as how to best to proceed when faced when a hypertensive patient on the day of surgery; general practitioners have a clear goal in terms of hypertension control before surgery; and patients will, in all likelihood, see a reduction in the cancellation and deferment of elective surgery. However, we feel that the opportunistic measurement of blood pressure, within the confines of a pre-operative assessment clinic, will continue to have the potential to benefit our patients’ long-term health. In addition, we should not lose sight of the increasing need for an individualised, patient-centred approach to peri-operative management 28, that is tailored to the particular surgical procedure; as such, there will be specific occasions when a more stringent control of blood pressure is necessary in order to deliver optimal peri-operative care. In the words of Douglas Bader: “Rules are for the obedience of fools and the guidance of wise men” 29. MDW is a member of the editorial board of Anaesthesia and this editorial has undergone additional external review as a result. No conflicts of interest declared.

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