Hypertension: A Changing Role for Anesthesiologists

See Article, p 1401 In respect of patients with arterial hypertension presenting for surgery, the role of anesthesiologists is changing. Initially, the role had been purely to consider the cardiovascular risk of surgery in such patients and inform them and the surgeons of the risk and the best preoperative approach. Today this role is expanding: anesthesiologists play an increasing role as perioperative physicians. This is particularly important in respect of patients with arterial hypertension because worldwide over 1 billion people suffer from hypertension. With the increasing age and the greater sedentarity of the population, the prevalence of hypertension will continue to rise toward 1.5 billion by 2025.1 Undiagnosed hypertension is frequent, and its treatment is often suboptimal, particularly in sub-Saharan Africa.2 This is also the case in the Indian subcontinent, to cite only 2 examples. High-income countries suffer from the same problem as highlighted in a recent report from the British Heart Foundation. It states that nearly 30% of the population suffers from arterial hypertension. For 10 patients diagnosed with hypertension, there are another 7 with undiagnosed hypertension.3 The diagnosis of hypertension can also be delayed in the United States.4,5 Thus, the preoperative assessment of patients offers an opportunity to identify those with arterial hypertension thereby influencing their short- and long-term management. Before the introduction of efficacious drug therapy, hypertension was a major cause of perioperative mortality, as high as 30% in a study by Sprague in 1929. Fifty years ago, there was still widespread concern that antihypertensive drugs impaired the maintenance of homeostasis during anesthesia and surgery resulting in cardiovascular collapse. It was generally accepted that their administration should be stopped before surgery. All the antihypertensive agents used in the 1960s (bethanidine, bretylium, guanethidine, methyldopa, reserpine) figure in a “danger list” for cardiovascular collapse in surgical patients. Later β-blockers were regarded as potentially dangerous in surgical patients, and it was recommended to stop them before surgery. Adverse effects of maintaining drug therapy, including β-adrenoceptor blockers, were disproved in very detailed hemodynamic studies in severely hypertensive patients undergoing surgery under general anesthesia.6 Thereafter, it became customary to continue the antihypertensive medication throughout the perioperative period. Further studies in the 1980s confirmed that maintenance of antihypertensive medication did not cause significant hypotension.7 With the introduction of effective drugs for the treatment of hypertension and the development of guidelines for the management of hypertensive patients in the population, the role of arterial hypertension as a risk factor for perioperative complications of anesthesia and surgery declined. Indeed several frequently used cardiovascular risk indices do not include hypertension as a risk factor for cardiovascular complications of surgery.8 Arterial hypertension is not mentioned in the 2014 American College of Cardiology/American Heart Association (ACC/AHA) guideline for the management of patients with cardiovascular disease presenting for surgery,9 only briefly mentioned in the 2014 European Guideline on the same topic,10 and not discussed at all in the 2018 European Society of Cardiology/European Society of Hypertension (ESC/ESH) guideline on hypertension.1 As a result, a recent guideline for the management of hypertensive patients presenting for surgery11 considers that a blood pressure <160/100 mm Hg in the community indicates that no further blood pressure measurements are needed at the time patients present at preoperative assessment clinics. In secondary care, pressures <180/110 mm Hg are regarded as adequate for surgery to proceed. The guideline was developed to reduce the number of cancellations of surgery based on hypertension alone. A comparison of cancellations before and after publication of the guideline shows a reduction of cancellations from 1.34% to 0.54%.12 While the guideline may adequately represent the modest role of moderately elevated blood pressure in the perioperative risk assessment of the planned surgery, and reduced the number of cancellations, it may lead to missing an important opportunity by the anesthesiology team for the treatment of hypertension to be initiated or optimized, especially in view of the fact that many patients with stage 1 hypertension are at moderate or high risk for long-term adverse events.13 Over the years, studies have shown that it is the presence of target organ involvement that is associated with adverse surgical outcome rather than the level of blood pressure on admission to hospital for surgery14; modest elevations of blood pressure can be associated with target organ damage.15 In sub-Saharan Africa, a systematic review based on 33 surveys involving over 110,414 participants of mean age 40 years found that of those with hypertension only between 7% and 56% were aware of their hypertensive status before the surveys, with a pooled prevalence of 27% (95% confidence interval, 23%–31%). Equally importantly, only 18% of hypertensive patients were receiving treatment and, ominously, in only 7% was blood pressure adequately controlled. The authors concluded that there is need for strategies for the diagnosis, control, and prevention of hypertension.2 This view is supported by the recent British Heart Foundation report showing that undiagnosed hypertension remains frequent even in a high-income country.3 This clearly indicates that poorly controlled or uncontrolled hypertension is a very common problem not just in low-income countries but also in high-income countries. Any measure that leads to better blood pressure management in the population is likely to be highly beneficial, as even modest reductions in systolic blood pressure reduce the risk of all cardiovascular events, including all-cause mortality.16 Anesthesiologists are in a unique position to “set the ball rolling” in hypertensive patients presenting for surgery. Their possible role may be increasing as a recent study showed that over the past 10 years, mortality associated with arterial hypertension has increased in urban and even more so in rural populations in the United States, based on death certificates from Centers for Disease Control and Prevention Wide-Ranging Online Data for Epidemiologic Research in the years 2007 to 2017. This indicates that despite guidelines, arterial hypertension is a major risk factor for death. The size of the problem is likely to be greater in low-income countries. Thus, opportunities to diagnose arterial hypertension and to initiate treatment need to be taken very seriously. This issue is addressed by the article entitled A Multi-center, Cross-sectional Quality Improvement Project: The Perioperative Implementation of a Hypertension Protocol by Anaesthesiologists in this issue of the Journal.17 Arterial hypertension has a high prevalence in patients presenting for surgery, yet in limited resource environments hypertension can be underdiagnosed and/or inadequately treated in primary care. The perioperative period with appropriate preoperative assessment offers a unique opportunity for hypertension to be diagnosed and for treatment to be instituted or optimized. In this multicenter study in Western Cape, South Africa, adult in-patients had their blood pressure measured during their preoperative assessment. In addition, to identify patients with end-organ damage, baseline kidney function, fasting blood glucose, lipogram, hemoglobin A1C (HbA1C), urine dipsticks, and an electrocardiogram (ECG) to assess left ventricular hypertrophy were obtained, facilitating the evaluation of cardiovascular risk. For those with normal blood pressure or well-controlled hypertension (<140/90 mm Hg), no further management was needed. However, for patients with stage 1 or 2 hypertension (blood pressure [BP] = 140–160/mm Hg and 160–180/mm Hg, respectively), management followed a specific algorithm with drugs being started 1 day postoperatively. For stage 3 hypertension (BP > 180/110 mm Hg), patients were immediately referred to a Specialist in Internal Medicine before surgery. An important aspect of the study is that screening for target organ damage was part of the assessment. This was reported in a separate article.13 In stage 1 hypertension moderate, high, and very high risk according to the ESC/ESH SCORE system1 were observed in 35%, 33%, and 13% of patients, respectively. With 68% of patients at moderate or high risk, it is clear that initiating treatment as early as possible is essential. Thus, even stage 1 hypertension as diagnosed on blood pressure measurements alone may not be evidence of low risk. The algorithm specifies that treatment should be initiated or escalated in patients with stage 1 hypertension. This is in keeping with data showing that blood pressure-lowering therapy is likely to prevent stroke and death in patients with uncomplicated stage 1 hypertension. In addition, the proportional reduction in cardiovascular disease events was the same or similar regardless of pretreatment blood pressure and the presence or absence of existing cardiovascular disease.18 The number of patients with hypertension, 106 of 298 patients screened, is small, but adherence rate to the algorithm by anesthesiologists was high (84%). Moreover, 55.5% of patients in whom treatment was initiated were still on medication at discharge, and their general practitioner was made aware of their condition and treatment. Thus, it is likely that long-term treatment may have been initiated, and hopefully continued, in many otherwise untreated hypertensive patients. This would not have happened if the recent UK guideline11 of accepting patients with stage 1 hypertension for surgery without further questions had been followed. Because of the small number of patients, this study may be considered as a proof of concept study. Yet it is important because such a systematic approach to dealing with blood pressure at the time of admission, or assessment, for surgery offers a very low-cost approach to a life-long risk reduction program. As recent data show that the threshold for diagnosing hypertension should be reduced to 130 mm Hg systolic blood pressure,16 as opposed to the more conventional value of 140 mm Hg,19 the algorithm could be adapted to new definitions very easily and could produce even more long-term benefits, as the new goal proposed for the treatment of hypertension is clearly beneficial. However, there are still some doubts about the advantages of treating patients classified as hypertensive according to the new definition,20 as the therapeutic goal does not take into consideration age and comorbidity except for stroke.21 As arterial hypertension remains a major risk factor for morbidity and mortality, each and every opportunity for diagnosis and initiation of treatment should be taken. Anesthesiologists can make a significant contribution to the long-term prognosis of hypertensive patients who otherwise may remain undiagnosed, suboptimally treated, or untreated. This is likely to be true in high-, middle-, and low-income countries, as undiagnosed hypertension is a worldwide problem.2–5 DISCLOSURES Name: Pierre Foëx, MD, DPhil. Contribution: This author helped in writing the first draft. Name: John W. Sear, MBBS, PhD. Contribution: This author helped in finalizing the paper. This manuscript was handled by: Angela Enright, MB, FRCPC.