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Hypertension is the commonest risk factor contributing to the global burden of disease. Public Health England estimates that, in England, 24% of the population are hypertensive, with 40% possibly undiagnosed. With this in mind, dentists, in particular those undertaking sedation, are in a perfect position to screen for high blood pressure and refer on for further detailed assessment. This paper outlines when a referral to the General Medical Practitioner (GP) should be considered, when sedation should be deferred and how hypertension is diagnosed and managed in primary care based on the National Institute for Health and Care Excellence (NICE)/British Hypertension Society (BHS) guidelines.
CPD/Clinical Relevance: The purpose of this article is to update General Dental Practitioners (GDPs), including those who practise IV Midazolam sedation, on how patients who present with suspected hypertension are managed by their GP. Consideration is given to what blood pressures are deemed safe to sedate and what blood pressures should be referred for further assessment, even if considered safe to sedate.
Article
Hypertension is outlined as the commonest risk factor contributing to the global burden of disease.1,2 Based on the health survey for England 2013/4, Public Health England estimates that 13.4 million people in England alone (24% of the population) are hypertensive, with possibly as many as 40% undiagnosed.3 This means that, potentially, two in five adults attending any dental practice, for any treatment, may be hypertensive and are, as yet, undiagnosed. It is one of the most important preventable causes of premature morbidity and mortality in the UK, being a major risk factor for stroke, myocardial infarction, heart failure, chronic kidney disease and cognitive decline.4 With each 2 mmHg rise in systolic BP associated with a 7% increased risk of mortality from ischaemic heart disease and a 10% increased risk of mortality from stroke, the individual and societal health burdens of the condition are clear.
At a population level, blood pressure (BP) follows a normal distribution, and in truth there is no natural cut-off as to where hypertension begins. But in light of the risks associated with increasing BP being cumulative, the National Institute for Health and Care Excellence (NICE) currently defines clinical hypertension as a sustained systolic BP of ≥140 mmHg and/or a sustained diastolic BP of ≥90 mmHg4 (Table 1).
Standard Clinic BP
Systolic (mmHg)
Diastolic (mmHg)
Stage 1
140–159
90–99
Stage 2
160–179
100–109
Stage 3
≥180
≥110
ABPM/HBPM
Systolic (mmHg)
Diastolic (mmHg)
Stage 1
≥135
≥85
Stage 2
≥150
≥95
Stage 3
≥180
≥110
Hypertension and dental treatment − risks and responsibilities
With hypertension increasing the risk of both ischaemic heart disease and stroke, undiagnosed and inadequately managed hypertension can have a significant impact on the provision of dental care.5,6 With this in mind, opportunities exist for the dental team to identify previously undiagnosed or inadequately managed hypertension. For those patients who require sedation for treatment, the pre-sedation assessment visit provides an excellent opportunity to screen for hypertension, allowing for prompt referral to the GP for further assessment where appropriate.
As a drug, the use of intravenous (IV) Midazolam sedation has been advocated for anxiolysis, but little research into its use in the management of hypertensive patients has been conducted.7 A recent study of 83 dental patients with stage 2 hypertension by Woolcombe et al revealed a profound antihypertensive effect of IV Midazolam in patients undergoing oral surgery procedures.8 The study reported a mean difference in systolic BP of 40 mmHg and diastolic BP of 21 mmHg at the end of the procedure between those patients treated with IV Midazolam sedation and those with local anaesthesia alone. Furthermore, the sedation group demonstrated a mean fall in BP of 27/11 mmHg in contrast to the local anaesthetic only group where a mean blood pressure rise of 8/1 mmHg was shown at the end of treatment. This would suggest that IV Midazolam sedation may have merit in the sedation of hypertensive patients. However, to draw conclusions, further research in the form of a well-designed randomized control trial would be needed and it should be noted that patients with hypertension are at risk of either increased hypertension with pain and anxiety, or decreases in blood pressure during sedation, and these changes may increase the potential risk of cardiovascular or cerebral complications.
On receiving a referral, the GP will measure the BP in surgery. If the clinic BP is found to be ≥140/90 mmHg, the patient is offered ambulatory BP monitoring (ABPM) to confirm a diagnosis of hypertension. ABPM involves the patient being fitted with a blood pressure device with a cuff that inflates to measure BP at least twice per hour for a total of 24 hours. A minimum of 14 measurements taken during the individual's normal waking hours are used to calculate the mean ABPM over the course of the day. When ABPM is used, patients are encouraged to carry on with their daily activities as per normal to ascertain as reliable a reading as possible.
When ABPM is deemed unsuitable by or for a patient, home BP monitoring (HBPM) can be used as an alternative to investigate possible hypertension. With this method, patients measure their own BP. Two consecutive BP measurements are taken a minimum of 1 minute apart with the person seated and BP is recorded twice a day (am and pm), preferably for 7 days. Measurements from the first day are discarded and an average value from the remaining measurements is used as the mean HBPM.
Whilst awaiting the results of ABPM/HBPM to confirm a diagnosis of hypertension, a number of investigations are carried out to search for target organ damage (chronic kidney disease, left ventricular hypertrophy, hypertensive retinopathy), as well as a formal assessment of cardiovascular risk using the QRISK®2 tool. These investigations include:
Fasting glucose, U&Es, eGFR, Total & HDL cholesterol;
Urinalysis for haematuria;
ACR (Urinary Albumin to Creatinine Ratio);
12 lead ECG;
Retinal Fundoscopy.
Figure 1 outlines the assessment of hypertension in diagrammatic form.
Figure 1. Hypertension assessment flowchart.
What is QRISK®2?
QRISK®2 is a formal risk assessment tool used to assess the need for the primary prevention of cardiovascular disease in individuals up to and including 84 years of age. The risk assessment tool encompasses numerous patient specific parameters including: gender, smoking status, the presence of diabetes mellitus, a history of angina or heart attack in a first-degree relative less than 60 years, postcode (a crude measure of deprivation) and Body Mass Index. Importantly, those patients aged ≥85 years and those younger who have pre-existing cardiovascular disease, type 1 diabetes, chronic kidney disease stage 3−5 or familial hypercholesterolaemia are considered at an increased risk of cardiovascular events without the need to use the QRISK®2 tool.
Advise smokers to stop and non-smokers to avoid passive smoking;
Advise weight loss if clinically overweight or obese;
Advise to keep alcohol consumption to the recommended maximum 14 U/week;10
Advise to adopt a healthy diet, limit salt intake to <6 grams/day, reduce caffeine and limit liquorice intake;11
Advise significant physical activity to develop cardiac capacity.
Medications
Antihypertensive drug treatment is offered to people aged <80 years with stage 1 hypertension who have one or more of the following: target organ damage, established cardiovascular disease, renal disease, diabetes or a 10-year cardiovascular risk (QRISK®2) equivalent to ≥20%.
For people aged under 40 years with stage 1 hypertension (ABPM/HBPM ≥135/85) NICE guidance currently recommends GPs to consider seeking specialist evaluation of secondary causes of hypertension (Table 2) and a more detailed assessment of potential target organ damage. This is because the 10-year cardiovascular risk assessment can underestimate the lifetime risk of cardiovascular events in people within this age range.
*Liquorice increases BP due to its mineralocorticoid effect.
Antihypertensive drug treatment is offered to people of any age with stage 2 hypertension (ABPM/HBPM ≥150/95).4Figure 2 gives a summary of the antihypertensive drug treatment recommendations from NICE/British Hypertension Society (BHS) guidance.4
Figure 2. A summary of antihypertensive drug treatment from NICE/BHS guidance.4
Age <80 years = Aim for a target clinic BP <140/90 mmHg;
Age >80 years = Aim for a target clinic BP <150/90 mmHg;
Patients with diabetes and/or chronic kidney disease = Aim for a target BP <130/80 mmHg.
What BP is deemed safe to sedate?
Specific risk assessment of hypertension for sedation in the dental environment is missing from recent guidance documents.12,13 Even within anaesthetic practice, until 2016 there were no nationally agreed guidelines for the diagnosis and management of raised blood pressure before elective surgery.14 With evidence of hypertension with target end organ damage being associated with a small increased incidence of major peri-operative cardiovascular events15 and physiological derangements, including arrhythmia, the Anaesthetists of Great Britain and Ireland (AAGBI), together with the BHS, set out to devise a nationally agreed consensus document on how to deal with raised blood pressure in the pre-operative period.14
Extrapolation of these guidelines to dental sedation seems sensible and the following points laid out in the document translate well:
Elective surgery should proceed for patients who attend the pre-operative assessment clinic without documentation of normotension in primary care if their blood pressure is <180/110 mmHg when measured in clinic.8,14,15
If the blood pressure is ≥180/110 mmHg, treatment should be postponed, and patients should return to their general practice for primary care assessment and management of their blood pressure;
If the standard clinic blood pressure is ≥140/90 mmHg but <180/110 mmHg, the GP should be informed, but elective surgery should not be postponed, granted that many of the patients who appear to be hypertensive at the dental surgery may actually be normotensive on further investigation by the GP.8
Obviously, a degree of clinical judgement is warranted with blood pressures <180/110 mmHg, and some GDPs may feel that the BP is better investigated by the GP before commencing treatment under IV Midazolam sedation.
As an important red flag, should patients with a recorded BP ≥180/110 mmHg report visual disturbances, severe headache or have signs and symptoms suggestive of a phaeochromocytoma (labile or postural hypotension, headache, palpitations, pallor and diaphoresis), they should be referred to the nearest Accident and Emergency Department or Acute Medicine Department the same day.
But it's only the ‘White Coat Effect’ isn't it?
The ‘White Coat Effect’ is defined as a discrepancy of >20/10 mmHg between clinic and average daytime ABPM or average HBPM blood pressure measurements at the time of diagnosis.4 Meta-analysis has shown that it is associated with a higher risk of cardiovascular disease when compared to normotension.16 In this, NICE recommends considering ABPM or HBPM as an adjunct to clinic blood pressure measurements to monitor the response of lifestyle modifications in patients with suspected ‘White Coat Effect’ hypertension.4 This re-enforces the view that those patients presenting to clinic with a BP ≥140/90 mmHg should be referred to their GP for further work-up, as ‘White Coat’ hypertension in itself has been shown to increase cardiovascular risk.
Calcium channel blockers and IV Midazolam
When considering sedating patients who have hypertension treated with a rate limiting calcium channel blocker (eg Verapamil or Diltiazem) with IV Midazolam, specific care should be taken to ensure slow Midazolam titration and that a reduced total dose is used.17 The reason for this is that Midazolam is metabolized by the CYP3A cytochrome. This enzyme is inhibited by the rate limiting calcium channel blockers and hence the sedative effects of Midazolam may be both enhanced and prolonged in patients concurrently taking these medications, leading to enhanced, occasionally profound, hypotensive effects, especially when additional antihypertensive medications may have also been taken by the patient.
Conclusion
Hypertension poses a significant cardiovascular risk for the UK population, and whilst evidence is as yet lacking, this may have an impact on patient risk during dental sedation with IV Midazolam as an adjunct to dental treatment under local anaesthetic. With the routine pre-operative sedation assessment pathway incorporating blood pressure checks, it provides an excellent platform to screen for hypertension. Whilst patients with raised BP may be sedated, the increased risks associated with hypertension should be considered, and engagement with the patient's GP is essential for those who present with uncontrolled hypertension.
It is hoped that this article provides a useful update as to what blood pressures are deemed safe to sedate, what blood pressures should be referred for further assessment, even if judged safe to sedate, and how hypertension is diagnosed and managed in General Medical Practice.
