Preoperative hypertension: perioperative implications and management

Learning objectives.

By reading this article, you should be able to:

• •Describe the management of patients with hypertension presenting for surgery.
• •Identify target organ damage associated with hypertension.
• •Discuss the perioperative management of patients with hypertension.

Key points.

• •High systemic arterial blood pressure in isolation is not a reason to cancel elective surgery per se.
• •Preoperative decisions should be made on each patient's overall cardiac risk rather than solely on the blood pressure reading.
• •Lower community thresholds for treatment will lead to more patients being prescribed antihypertensive pharmacotherapy.
• •Combination tablets could complicate preoperative management of antihypertensive pharmacotherapy.
• •Preoperative hypotension may have implications for future preoperative risk stratification.

Systemic arterial hypertension is one of the most important treatable causes of population morbidity and mortality. It is common, affecting one in four adults in England (12.5 million), with a further 5.5 million likely remaining undiagnosed, but evidence to guide the preoperative optimisation of patients with hypertension is limited.^1,2 Of necessity, guidelines rely to a considerable extent on observational data and the results of studies in the non-operative setting. In the UK, the Association of Anaesthetists (AoA) and the British Hypertension Society (BHS) have published a joint statement on the management of perioperative hypertension, and more recently, the Perioperative Quality Initiative (POQI) Consensus Workgroup has provided guidance.^3,4 The AoA/BHS guidance suggests that surgery should be postponed if the patient's blood pressure is over 180/110 mmHg, whereas the more recent POQI consensus questions whether there is sufficient evidence to recommend a specific blood pressure to decide on whether to proceed with surgery or not. This review will update the reader regarding changes in the guidelines for management of hypertension in the community and the preoperative management of hypertensive medications. The impact of preoperative, intraoperative and postoperative blood pressure, and the importance of preoperative hypertension and hypotension on postoperative outcome will be discussed.

Long-term management and treatment of hypertension

Treatment targets

The aim of chronic blood pressure management is lifetime cardiovascular risk reduction, whereas perioperative blood pressure management goals focus on the avoidance of perioperative morbidity and mortality. However, guideline statements on the long-term management of hypertension set the context for the perioperative management of blood pressure.

The UK National Institute for Health and Care Excellence (NICE) classification of hypertension is given in Table 1. The diagnosis of stages 1 and 2 hypertension rests on the use of ambulatory and home blood pressure monitoring initiated on the basis of clinic blood pressure measurements (Fig. 1). Patients whose clinic blood pressure measurements are >140/90 mmHg are offered ambulatory blood pressure monitoring to confirm a diagnosis of hypertension. Ambulatory monitoring gives an average value for the blood pressure over the monitoring period. The NICE guidance recommends formulating an average from at least 14 blood pressure values taken during waking hours. Home blood pressure monitoring can be offered when ambulatory monitoring is not feasible. Patients with stage 1 hypertension are offered lifestyle advice and may receive pharmacological treatment based on their cardiovascular disease risk. Patients with stage 2 hypertension are offered pharmacological therapy alongside lifestyle advice. Patients aged over 40 yrs who are diagnosed with hypertension should be considered for a specialist referral to exclude secondary causes. Investigations to identify target organ damage and quantify cardiovascular risk should commence whilst awaiting diagnosis of suspected hypertension.

Table 1.

Stages of hypertension described in the National Institute for Health and Care Excellence (NICE) guidelines: hypertension in adults: diagnosis and management. ABPM, ambulatory blood pressure monitoring.⁶

Stage	Clinic blood pressure (mmHg)	ABPM daytime average (mmHg)
1	140/90–159/99	135/85–149/94
2	160/100–179/119	>150/95
3	Systolic >180 or diastolic >120

Fig 1.

Visual summary of the UK National Institute for Health and Care Excellence (NICE) recommendations for diagnosing and treating hypertension; hypertension in adults: diagnosis and treatment. Reproduced with permission from reference 6. ABPM, ambulatory blood pressure monitoring; CVD, cardiovascular disease; HBPM, home blood pressure monitoring.

The 2019 NICE guidance increases the emphasis on maintaining blood pressure consistently below target levels. Target blood pressures in patients aged under 80 yrs are <140/90 mmHg (clinic measurement) or <135/85 mmHg (ambulatory or home measurement). The target is slightly higher in patients over 80 yrs at <150/90 mmHg (clinic measurement) and <145/85 mmHg (ambulatory or home measurement). Currently, it is estimated that only 50% of patients with hypertension actually achieve clinic blood pressures below 140/90 mmHg.⁵

The 2018 European Society of Cardiology/European Society of Hypertension guidelines are more demanding than the NICE guidelines with regard to blood pressure targets.⁵ They advise that treatment should be initially targeted to reduce blood pressures to below 140/90 mmHg and if tolerated further to 130/80 mmHg, and state that in patients under 65 yrs the systolic blood pressure should be reduced to 120–129 mmHg.⁵ The European guidance also recommends lower blood pressure targets in diabetics, whereas NICE makes no distinction.

Both the UK and European guidelines advocate the use of ambulatory blood pressure monitoring for diagnosing hypertension. Ambulatory monitoring gives a better indication of the ‘true’ blood pressure and correlates well with invasive blood pressure measurements.⁶ It can identify white coat and masked hypertension, and also provides additional information on 24 h blood pressure variability.⁵ When available, ambulatory monitoring gives a robust baseline pressure that can be used to guide intraoperative care. Despite the cost of equipment, ambulatory monitoring is likely to be the most cost-effective method for diagnosing hypertension.⁶

Blood pressure management

Lifestyle

Appropriate lifestyle modifications should be suggested to patients with suspected or confirmed hypertension.⁶ Such management rests on establishing an effective collaboration between the patient, the doctor and other healthcare staff.⁷ Advice includes weight loss, healthy eating, smoking cessation, increased physical activity and reduced alcohol consumption. Some patients with stage 1 hypertension can delay or avoid the need for pharmacotherapy by following this advice. However, most patients with hypertension will require drug treatment, and this should not be delayed in patients with a high cardiovascular risk or related organ damage.⁵

Pharmacotherapy

In the UK, NICE recommends pharmacotherapy in patients aged <80 yrs with stage 1 hypertension together with target organ damage, cardiovascular disease, renal disease, diabetes or 10 yrs CVD risk of >10%. The guidance was updated in 2019 with a major change that pharmacological treatment is now offered to patients with stage 1 hypertension under the age of 80 who have 10 yrs cardiovascular risk of >10%, a reduction from the previous 20% threshold.⁶ This equates to an additional 450,000 men and 270,000 women being eligible for treatment.⁸ It is important to mention that under the NICE guidelines, patients aged under 80 yrs with systolic blood pressures <139 mmHg would not be offered treatment regardless of cardiovascular risk.⁸

With more people being eligible for treatment and greater emphasis on tight blood pressure control, the number of patients taking antihypertensive therapy presenting for surgery may increase significantly.

The recommended tool for cardiovascular risk calculation in the UK is currently the QRISK3 calculator (https://qrisk.org/three/),⁹ which incorporates a number of variables, such as mental health and corticosteroid use, not included in the previously used QRISK2 calculator. The European guidance uses the Systemic Coronary Risk Evaluation score. It uses fewer variables than the QRISK3 calculator and is also available online (https://www.heartscore.org/).¹⁰ The American College of Cardiology uses the Atherosclerotic Cardiovascular Disease score (https://tools.acc.org).¹¹

For patients over 80 yrs of age, NICE advises considering starting drug treatment at blood pressures >150/90 mmHg. The UK NICE guidance recommends a stepwise approach to commencing antihypertensive therapy and highlights that compliance with treatment must be explored before commencing another drug class. There are various treatment options at each step to allow for intolerance of particular treatments, as detailed in Figure 2.

Fig 2.

Visual summary of the UK National Institute for Health and Care Excellence (NICE) recommendations for diagnosing and treating hypertension; choice of antihypertensive drug, monitoring and targets. Reproduced with permission from reference 6. ABPM, ambulatory blood pressure monitoring; ACEI, angiotensin-converting enzyme inhibitor; ARB, angiotensin receptor blocker; CCB, calcium channel blocker; HBPM, home blood pressure monitoring.

In Europe, combination pills are recommended. This is based on the premise that monotherapy is often ineffective in achieving target blood pressures of below 130/80 mmHg, as recommended in the European guidelines, and most patients will therefore require combination therapy. Combination pills are single pills that contain two or three drugs or drug classes, such as an angiotensin-converting enzyme inhibitor (ACEI), calcium channel blocker and a diuretic. These may be only available in certain jurisdictions. Combination therapy can be quicker and more effective at reducing blood pressure than up-titrating monotherapy, and also improves treatment compliance.⁵ Whilst being useful at managing hypertension, combination tablets may pose a challenge in the perioperative period if one drug class is to be stopped and another continued.

Preoperative implications of hypertension

History and investigation

Hypertension is generally asymptomatic and may be picked on routine blood pressure screening or during the clinical assessment for another condition or for planned surgery.¹² Patients with hypertension can also present with papilloedema, new onset confusion, chest pain, signs of heart failure or acute kidney injury. Same-day specialist review should be sought in symptomatic patients with blood pressures >180/120 mmHg.⁶ Clinical review of the hypertensive patient should encompass assessment of overall cardiovascular risk and of the comorbidities for which hypertension is a risk factor.

Target organ damage and ‘hypertension-mediated organ dysfunction’ are terms often used to describe the pathologies associated with hypertension, such as renal impairment and cardiovascular and cerebrovascular diseases. Preoperative investigations of patients with diagnosed hypertension or raised blood pressure should be aimed at identifying and assessing these conditions. Recommended investigations include serum electrolytes, creatinine, estimated glomerular filtration rate, cholesterol, a 12-lead electrocardiogram and urinalysis. Hypertension and diabetes are associated; people with type 2 diabetes are approximately two and a half times more likely to develop hypertension. Measurement of glycosylated haemoglobin gives an indication of long-term glucose control. The UK NICE guidance also recommends fundoscopy to assess hypertensive retinopathy. However, this procedure would likely be impractical in the preoperative setting. Other preoperative investigations, such as echocardiography, should be guided by clinical judgement and surgical risk.

Preoperative hypertension

Historically, elective surgery in patients with poorly controlled blood pressure has been postponed because of perceived increased perioperative cardiovascular risk. This practice is based on older studies in patients who now would be classed as having severe hypertension, and it is inappropriate to use data from these studies to guide management of patients with stages 1 and 2 hypertension.¹³ An observational cohort study revealed no association between the stage of hypertension and significant haemodynamic instability, although just 3% of the study group had stage 3 hypertension (blood pressure >180/110 mmHg).¹⁴ There is insufficient evidence to suggest that one value of either the systolic pressure, diastolic pressure or MAP is superior at predicting risk.³

There is little evidence to suggest that lowering blood pressure preoperatively reduces risk and that patients with stage 1 or 2 hypertension without target organ damage have increased perioperative morbidity and mortality.^3,4

The AoA/BHS guidance advises that patients whose blood pressure in the community is <160/100 mmHg may be referred for elective surgery without delaying for further investigation or treatment of their blood pressure.⁴ In patients who are referred for elective surgery without a community blood pressure reading, surgery can proceed provided that the blood pressure measurement in the pre-assessment clinic is <180/110 mmHg. If the blood pressure is >180/110 mmHg, the guidelines suggest that surgery should ideally be delayed, allowing antihypertensive treatment to be initiated.

Where hypertension has been identified de novo at a preoperative assessment clinic, there is a responsibility to communicate this to the patient's primary care practitioner. The AoA/BHS guidance includes a draft letter that can be sent to them.

In 2019, the multinational Perioperative Quality Consensus multidisciplinary working group published a set of consensus statements and practical recommendations on preoperative blood pressure, risk and outcomes for elective surgery.³ These recommendations suggest that, whilst extremes of blood pressure may be associated with increased risk, there is no evidence to identify a specific blood pressure value above which would alter the decision whether to proceed with surgery.³

Hypertension in the elderly

Hypertension is common in older patients, having a prevalence of over 60% in people aged >60 yrs.⁵ The European guidelines define ‘old’ as patients >65 yrs and ‘very old’ as those >80 yrs. There has previously been concern that antihypertensive treatment in elderly patients may increase mortality and morbidity if they have peripheral arterial disease or heart failure.¹⁵ Evidence from RCTs has demonstrated that antihypertensive therapy in the old and very old significantly reduces cardiovascular morbidity and all-cause mortality, with the caveat that frail and institutionalised patients have largely been excluded from such studies.⁵ The NICE guidance advises that blood pressure treatment targets should be higher (<150/90 mmHg) in patients aged > 80 yrs. The guidance emphasises the importance of using clinical judgement when deciding treatment targets in these groups. Postural hypotension is more common in this group, and these patients can be at increased risk of adverse events, such as falls, if treatment is commenced based solely on seated blood pressures. To screen for postural hypotension, seated blood pressures should be compared with standing blood pressures. If the standing systolic pressure decreases by more than 20 mmHg, then this should prompt a review of medication or specialist referral to avoid adverse effects from antihypertensive therapy.

Secondary hypertension

Hypertension resulting from an identifiable pathology is referred to as secondary hypertension and accounts for 5–15% of patients with hypertension.⁵ ‘Red flags’ include young patients with an absence of risk factors, sudden increases in blood pressure in previously stable patients and resistant hypertension. Common causes include obstructive sleep apnoea, renal disease and endocrine abnormalities. Non-urgent surgery should be delayed to enable these patients to have further investigations.

Preoperative hypotension

Recent observational data suggest a significant association between preoperative hypotension and increased mortality in patients aged >65 yrs.² A non-linear increase in postoperative mortality was reported with systolic pressures <119 mmHg and diastolic pressures <63 mmHg.² To put the results in context, the paper describes a preoperative systolic pressure of 100 mmHg as having a similar risk to a preoperative diagnosis of heart failure.²

Preoperative management of antihypertensive drugs

In patients who are still taking ACEIs or angiotensin receptor blockers (ARBs), hypotension may be more profound especially when in combination with diuretics.¹⁶ The 2017 Vascular events In noncardiac Surgery patIents cOhort evaluatioN (VISION) Study of 14,687 patients undergoing non-cardiac surgery showed that withholding ACEIs and ARBs before surgery was associated with a lower risk of death and postoperative vascular events.¹⁷ The practice of withholding ACEIs and ARBs preoperatively varies.¹² The concern with continuing these drugs is that intraoperative hypotension may result in organ hypoperfusion and acute organ injury. The recent POQI Group consensus recommends withholding ACEIs and ARBs 24 h before surgery.³ If ACEIs and ARBs are omitted before surgery, then they should be restarted as soon as appropriate after the operation, as observational data suggested that failure to do so was associated with adverse postoperative outcomes.³ In cardiac surgery, withholding ACEIs and ARBs preoperatively is reported to be associated with increased mortality.³

The American College of Cardiology and American Heart Association recommend that ACEI drugs and ARBs should be continued perioperatively, based on evidence in the non-surgical setting that inappropriate discontinuation is associated with worse outcomes.¹⁸ The 2014 European Society of Cardiology and European Society of Anaesthesiology guidelines on non-cardiac surgery also warn about the association between ACEIs and ARBs and intraoperative hypotension. However, they suggest continuing ACEIs and ARBs through the perioperative period in patients who have left ventricular dysfunction.¹⁹

Beta blockers are no longer first-line treatment for high blood pressure, but are prescribed for a number of conditions. Pre-existing beta-blocker treatment should generally be continued perioperatively.³ Fixed-dose beta blockade initiated de novo in the immediate perioperative period may be associated with an increased risk of perioperative death.^3,20

There is limited evidence available on the perioperative management of calcium channel blockers and diuretics. The POQI Group recommends that decisions regarding these drugs are made on an individual patient basis.³

Ultimately, in the absence of RCTs, and with conflicting views (particularly with regard to the management of ACEIs and ARBs), decisions on withholding antihypertensive therapy preoperatively should be made on a case-by-case basis and care taken to address episodes of hypotension that will arise if medications are continued. Expert opinion, such as that from the Perioperative Outcomes Quality Initiative, can help inform these decisions (Fig. 3).

Fig 3.

Infographic demonstrating the Perioperative Outcomes Quality Initiative (POQI) consensus recommendations on the management of blood pressure and antihypertensive agents in the preoperative period. Reproduced with permission from POQI. ACEI, angiotensin-converting enzyme inhibitor; ARB, angiotensin receptor blocker.

In most circumstances, it would be unlikely that patients would be cancelled for surgery if they had accidently taken their ACEIs on the morning of their procedure. Whilst this could potentially cause greater degrees of hypotension, this can be anticipated and management planned accordingly.

Intraoperative management of blood pressure

General anaesthetic agents can cause hypotension by causing vasodilation and by reducing cardiac output. Patients with hypertension can display greater cardiovascular lability during surgery with increases in blood pressure and heart rate at induction of anaesthesia and risks of hypotension in the intraoperative period.

An observational study of 33,000 patients demonstrated that an increasing intraoperative duration of a MAP <55 mmHg was associated with myocardial and acute kidney injury.²¹ A recent RCT looked at the effects of individualised vs standard blood pressure management strategies on postoperative organ dysfunction in patients undergoing major surgery.²² Patients in the standard arm received ephedrine for reductions in systolic blood pressure <80 mmHg or <40% of the patient's baseline. Patients in the treatment arm had their blood pressure maintained within 10% of baseline with a dilute infusion of noradrenaline (norepinephrine). Patients in the treatment arm, who had stricter control of their blood pressure, had significantly lower rates of postoperative organ dysfunction.²²

An adequate blood pressure is required to perfuse cells. However, this does not always guarantee adequate oxygenation to allow cellular respiration in all tissues.²³ For example, young patients can compensate for the physiological challenge of significant hypovolaemia and have normal blood pressure at the expense of areas of their body being hypoperfused. There are multiple factors that affect the perfusion pressure, including myogenic, neurogenic and metabolic components. Thus, blood pressure values must be interpreted in the context of the clinical situation.²⁰

Autoregulation in the circulation of individual organs may be altered in patients with hypertension, although this is not a consistent finding across studies.⁷

Recent publications emphasise the importance of avoiding intraoperative hypotension, but there is no universal consensus on thresholds to guide blood pressure management.^3,19,24,25 Maintaining a systolic arterial pressure of over 100 mmHg and a MAP over 60 mmHg may reduce risk.^3,24 Preoperative blood pressure may be used to guide intraoperative blood pressure management, with some opinions recommending that blood pressure should be kept within 10% of baseline, or within 20% of baseline in patients with higher baseline blood pressures (>130/80 mmHg).^19,25

Postoperative hypertension

Postoperative hypertension can occur in up to 20% of patients after elective non-cardiac surgery and is associated with adverse outcomes, including stroke, myocardial injury, arrhythmias and bleeding.²³ There is limited evidence for a threshold pressure above which harm occurs. However, systolic pressures over 180 mmHg as indicating high risk, have been included in a number of validated early warning systems.²³

Conclusions

Perioperative risk stratification for patients with hypertension is multifactorial and involves patient, anaesthetic and surgical factors. Changes in community guidelines and the demonstration of an association between preoperative hypotension and increased mortality have implications for perioperative care and risk stratification. Recent community hypertension guidelines have introduced more aggressive treatment targets, meaning more patients will be on antihypertensive medication, some of which may be ‘single pill’ combination therapy. Current practice is informed by observational studies and expert opinion. Guidance exists to help in decision making, but ultimately decisions should be made on a case-by-case basis. Elevated blood pressure in isolation is not a reason to cancel elective surgery per se with the current consensus being that it is not possible to set a ‘one size fits all’ threshold above which elective surgery should be deferred. We must consider each patient's overall cardiac risk and make decisions based on this rather than acting solely on isolated blood pressure readings.

Declaration of interests

SJH is a director and editorial board member of the British Journal of Anaesthesia. AT declares no conflicts of interest.

MCQs

The associated MCQs (to support CME/CPD activity) will be accessible at www.bjaed.org/cme/home by subscribers to BJA Education.

Biographies

Andrew Tait MBChB FRCA is a locum consultant at Leeds Teaching Hospitals NHS Trust.

Simon Howell MA(Cantab) MRCP FRCA MSc MD is an associate professor of anaesthesia at the University of Leeds and an honorary consultant anaesthetist at Leeds Teaching Hospitals NHS Trust. He is and editorial board member and director of the British Journal of Anaesthesia.

Matrix codes: 1A02, 2A03, 3I00