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Is there a strong rationale for deferring elective surgery inpatients with poorly controlled hypertension?Barbara Casadei and Hala Abuzeid

Hypertension remains one of the most common avoidable

medical indications for deferring elective surgery, thereby

increasing both the financial and emotional burden of

having an operation. Although the evidence supporting the

current guidelines on management of hypertension is

among the best available in any field of medicine, our

knowledge on whether high blood pressure (BP) is an

independent perioperative risk factor is plagued by much

uncertainty. Indeed, it is still unclear whether postponing

surgery on the ground of elevated preoperative BP

measurements will lead to a reduction in perioperative

cardiac risk. Similarly, the importance of multiple versus

isolated BP measurements in predicting perioperative

complications has not yet been assessed. As most studies

have evaluated the predictive value of diastolic BP, the risk

of perioperative cardiovascular events associated with

isolated systolic hypertension remains uncertain. With no

controlled evidence to address these issues, no firm

recommendations can be made to improve patients’ safety.

These important issues now need to be addressed by

modern clinical trials. J Hypertens 23:19–22 & 2005

Lippincott Williams & Wilkins.

Journal of Hypertension 2005, 23:19–22

University Department of Cardiovascular Medicine, John Radcliffe Hospital,Oxford, UK.

Sponsorship: We are grateful for the generous support of the British HeartFoundation.

Correspondence and requests for reprints to Dr Barbara Casadei, UniversityDepartment of Cardiovascular Medicine, John Radcliffe Hospital, Oxford OX39DU, UK.Tel: +44 1865 220132; fax: +44 1865 768844;e-mail: [email protected]

Received 12 July 2004 Revised 12 August 2004Accepted 18 August 2004

IntroductionArterial hypertension is undoubtedly one of the most

important risk factors for cerebrovascular and coronary

heart disease (CHD). Robust epidemiological evidence

indicates that there is a log-linear relationship between

arterial blood pressure (BP) and incidence of stroke and

CHD across a wide range of BPs [1], and a number of

large controlled clinical trials have demonstrated that

lowering BP with antihypertensive medications de-

creases cardiovascular morbidity and mortality [2].

Does this evidence have a bearing in theperioperative risk assessment of surgicalpatients?This question is of great importance since cardiac

events, such as myocardial infarction or cardiac death,

are relatively frequent perioperative complications, oc-

curring in 1–5% of unselected patients undergoing

non-cardiac surgery [3,4]. Similarly, hypertension is a

common finding in the middle-aged/elderly population

presenting for major non-cardiac surgery, and the rate

of control, particularly of systolic BP, remains poor in

spite of ‘best’ available treatment strategies [5–7].

Anaesthetists are therefore often faced with patients

with poorly controlled hypertension and with the

unresolved question as to whether they should proceed

with anaesthesia, or delay surgery until additional BP-

lowering treatment is instituted. As the evidence for

either course of action is limited, it is not surprising to

observe wide variation in practice [8]. However, the

important fact is that hypertension remains the most

common avoidable medical indication for deferring

elective surgery [9,10].

Admission BP versus BP-related target organdamageWhile the evidence supporting the current guidelines

on management of hypertension [11,12] is amongst the

best available in any field of medicine, our knowledge

of hypertension as a perioperative risk factor is largely

based on small, mostly single-centre, observational

studies.

Classic investigations in the early 1970s showed a

higher incidence of intraoperative arrhythmias and

cardiovascular ischaemia in patients with severely ele-

vated diastolic BP (. 120 mmHg) [13], providing the

first rationale for deferring elective surgery on the basis

of preoperative BP measurements alone. These studies

also highlighted the risk associated with enhanced

reflex sympathetic and BP surges in hypertensive pa-

tients in response to noxious stimuli, such as tracheal

intubation [14,15], and pioneered the perioperative use

of beta-blockers. Later studies showed that uncon-

trolled (mostly systolic) hypertension was associated

with a greater incidence of pre- and postoperative

myocardial ischaemia in patients presenting for elective

non-cardiac surgery [16,17], supporting the notion that

severe hypertension may pose an immediate risk to

surgical patients. From these data it was inferred that

Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.

Review 19

0263-6352 & 2005 Lippincott Williams & Wilkins

deferring surgery in order to lower BP, even in the

short term, may lead to a reduction in perioperative

cardiovascular complications. More recently, investiga-

tions have indicated that a history of hypertension is a

predictor of perioperative cardiac death in elective

cardiac and non-cardiac surgery [18,19]. Interestingly,

however, these studies have not been able to demon-

strate a direct relationship between high BP measure-

ments taken at the time of hospital admission and

perioperative cardiac complications [20,21] (Fig. 1),

suggesting that target organ damage associated with

long-standing hypertension may have a stronger prog-

nostic predictive value than the BP level per se [22]. A

similar conclusion can be derived from an earlier study

by Goldman and Caldera [23], who showed that most

of the perioperative complication in patients with a

previous diagnosis of hypertension occurred in the

treated/controlled group, casting some doubt on the

prognostic significance of admission BP measurements,

as these are unlikely to reflect the patient’s ‘usual’ BP.

As there is now compelling evidence indicating that

multiple BP readings by means of ambulatory or home

BP monitoring are better predictors of cardiovascular

events than isolated ‘office’ BP measurements [24–30]

(Fig. 2), it would be important to evaluate whether the

BP burden assessed using these techniques will prove

to be a more accurate predictor of cardiovascular

complications in surgical patients.

Although the potential predictive value of ‘white-coat’

hypertension in surgical patients has never been investi-

gated, the aforementioned absence of a relationship

between elevated admission BP and cardiac complica-

tions [20,21], would support the idea that these patients

may have a significantly lower surgical risk than ‘true’

hypertensive subjects, reflecting their lower ‘usual’ BP

and hypertension-related target organ damage. How-

ever, it could equally be reasoned that these subjects’

hyper-reactivity to stress and reduced ability to control

surges in sympathetic activity may be particularly hazar-

dous in the context of anaesthesia and surgery [31].

Systolic or diastolic BP?If hypertension-related target organ damage (rather

than the BP level at the time of hospital admission)

were a better predictor of perioperative complications,

we may expect different types of hypertension to have

a different impact on the perioperative risk of surgical

patients. For instance, there are epidemiological data

indicating that systolic BP is a more accurate predictor

of cardiovascular events than diastolic BP, particularly

in older subjects [32,33]. Isolated systolic hypertension

and high pulse pressure are well-established markers of

stiffness of the large arterial vessels and important

determinants of left ventricular afterload [34]. Recent

controlled trials have confirmed that antihypertensive

treatment in these patients is highly effective in redu-

cing the risk of stroke, dementia and heart failure [35–

40]; however, the percentage of patients achieving a

‘normal’ systolic BP in response to treatment is rela-

tively low (c. 40–50% versus . 90% control rate for

diastolic BP [6,7,41]). Thus, risk stratification of pa-

tients on the basis of diastolic BP values alone in earlier


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100

150

200

250

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pressure

Controls:systolic

pressure

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Controls:diastolicpressure

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mH

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Fig. 1

Admission systolic and diastolic pressures of patients who died of acardiovascular cause within 30 days of anaesthesia and surgery(Cases) and matched patients who did not die of a cardiovascularcause in the perioperative period (Controls). The boxes indicate themedian values and 25th and 75th centiles. There were no significantdifferences between admission blood pressure in the two groups (fromref. 20, with permission).

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Fig. 2

Incidence of cardiovascular events according to office and 24-hsystolic blood pressure (BP). In each range of office systolic BP, a 24-hambulatory systolic BP > 135 mmHg predicted a higher incidence ofcardiovascular events than a 24-h ambulatory systolic blood pressure, 135 mmHg (from ref. 29, with permission).

20 Journal of Hypertension 2005, Vol 23 No 1

studies might have been potentially misleading, parti-

cularly in older patients where isolated systolic hyper-

tension is common. Indeed, in a recent study, systolic

hypertension (. 180 mmHg) alone was found to be a

strong predictor of adverse cerebral outcome and

cardiovascular complications in patients undergoing

coronary bypass surgery [42].

GuidelinesSeveral guidelines suggest that anaesthesia and surgery

should be deferred in patients with moderate to severe

hypertension (diastolic BP . 110 mmHg) to allow BP

to be treated. Is this course of action associated with a

reduced number of perioperative cardiac complications?

There is surprising little evidence to support this well-

accepted practice. Randomized, placebo-controlled

studies have shown that perioperative treatment with

beta-adrenergic receptor blockers is associated with a

reduction in the incidence of cardiac death or myocar-

dial infarction in high-risk patients undergoing major

non-cardiac [43] or vascular surgery [44]. Although

hypertension was common in this cohort (present in

c. 70% of patients in the study carried out by Mangano

et al. [43]); the possibility that a reduction in BP might

have accounted for at least part of the favourable effect

of beta-adrenoceptor blockade on outcome was not

taken into account, and the protective effect of beta-

blockers was attributed to their preventive effect on

perioperative ischaemia. Nevertheless, perioperative

silent ischaemia has been shown to be more common

in patients with a diagnosis of hypertension, and Stone

et al. [45] demonstrated a significant reduction in

the incidence of postoperative myocardial infarction

in uncontrolled hypertensive subjects (160–200/90–

100 mmHg) treated with beta-blockers. These findings

therefore do not exclude that part of the beneficial

effect of beta-blockers in patients at high risk of

perioperative cardiovascular complications may result

from their BP-lowering effect.

Should all patients with a diagnosis of hypertension

who need major elective surgery be treated with beta-

blockers? Mangano et al. [43] considered beta-blocker

treatment for all patients who met at least two of the

following criteria: older than 65 years, hypertensive,

current smoker, cholesterol . 6 mmol/l or diabetes; that

is, in patients with a 10-year predicted risk of CHD

greater than 15%. Although in-hospital mortality was

similar (3%) in both groups, a 67% reduction in cardiac

events and a 50% reduction in all-cause mortality

become apparent in patients treated with beta-blockers

at 1 year and 2 years of follow-up, respectively.

It is significant that, of all the parameters that have

been tested as predictors of cardiac morbidity in

surgical patients, the most robust are a recent myocar-

dial infarction, a history of cerebrovascular disease and

a diagnosis of heart failure [22]. This suggests that the

main determinant of poor outcome in the perioperative

period is the a priori probability of that outcome. If this

were the case, one could argue that lowering BP shortly

before surgery may not be sufficient to yield a lower

perioperative risk, unless BP were high enough to

constitute an immediate risk to the patient, indepen-

dent of surgery. Furthermore, it is not clear whether

some antihypertensive agents or preparations (e.g. oral

beta-adrenoceptor blockers) would be more effective

than others (e.g. diuretics or calcium antagonists or i.v.

administration of short-acting agents) in preventing

cardiovascular events in the perioperative period.

SummaryThe management of hypertension in surgical patients is

a surprisingly dark corner in a field that is illuminated

by some of the strongest and most compelling evidence

available in clinical practice. To date it remains unclear

whether the BP level or BP-related target organ

damage at the time of surgery predicts perioperative

cardiovascular complications in patients undergoing

major surgery, and thus whether deferring surgery in

order to improve BP control will lead to a reduction in

perioperative cardiac risk. Obtaining a reliable assess-

ment of the patients BP by using 24-h home BP

monitoring may help in establishing the importance of

‘usual’ BP as a surgical risk factor. Although the use of

beta-blockers preoperatively has been associated with a

reduced risk of cardiac death, it is unclear whether the

reduction in BP elicited by these agents might have

played a significant part in this outcome.

Thus, in the absence of controlled evidence, no firm

recommendations can be made to improve patients’

safety and reduce the financial burden of postponing

surgery on the grounds of elevated preoperative BP

measurements. As suggested by Fleisher [46] in a

recent editorial, the practice of postponing surgery for

6–8 weeks in patients with a diastolic BP . 110 mmHg

‘must be balanced against the urgency of the surgery

and the acknowledgement of lack of data to determine

if such practices will improve outcome’. These impor-

tant issues now need to be addressed by modern

clinical trials.

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