Author: Charlotte Davies, Philippa Peto, Jasmine Lee, Kate Wesseldine / Editor: Liz Herrieven / Codes: CC9, SLO1 / Published: 23/02/2021

Blood pressure is a fickle beast and one that I’m not sure many of us really understand. We’re fabulous at treating it if it’s too low… but when it’s too high, our practice is a bit more varied. The old adage of measuring it skin to skin looks to be dogma.

What is Blood Pressure? 

Medical school was a long time ago for many of us [Editor – speak for yourself, I’m a spring chicken…]. For a refresher on  BP physiology have a look at this website. 

Key Points:
BP = flow X resistance

MAP = cardiac output X total peripheral resistance

Short Term Control: detected by baroreceptors in the aorta and carotid sinus. Parasympathetic fibres reduce the BP via the vagal nerve. The sympathetic fibres increase the BP.

Long Term Control: managed by the renin angiotensin aldosteronesystem. ANP and prostaglandins also have an effect.

The differentiation between the two systems is important as the short term control system is likely to be the predominant one affecting blood pressure in the ED, and the effect of short term control is difficult to predict.

Symptomatic Blood Pressure Control

The first challenge in blood pressure control is deciding whether the patient before you is truly asymptomatic from their hypertension.

Headache is tricky as a headache might be a sign of a hypertensive emergency and is listed as a red flag by NICE. There’s a significant nocebo effect and I’m sure many of us have seen patients with a headache, who have a high BP because of the pain, or the anxiety or other things.

Epistaxis is commonly associated with hypertension but there is not enough evidence to prove causation. I would treat epistaxis related hypertension as “short term” control with analgesia and review.

Chest Pain is a worrying feature with hypertension as it may indicate ischaemia or an aortic dissection. We will cover treatment of hypertension associated with aortic dissection later in “special situations”.

Altered Consciousness and Confusion may be caused by a hypertensive emergency and consideration should be given to lowering the blood pressure.

Hypertensive emergencies are rare, and the patient normally looks very unwell, even if it’s triggered by a phaeochromocytoma. They should be treated with senior input and patients normally need IV treatment along with invasive monitoring in a critical care environment. For more information read the RCEMLearning reference or learning module on hypertensive emergencies, or have a listen to EMCrit.


Asymptomatic Blood Pressure Control

Look for hidden symptoms if BP >140/90mmHg. NICE Guidelines suggest looking for target organ damage:
*Retinal Haemorrhage
*New Onset Confusion
*Signs of heart failure
*Acute kidney injury

We should probably be looking at all of these factors in all patients who present with hypertension to the ED, although most of us aren’t very confident at looking for papilloedema. Acute kidney injury is normally defined by U&E results, but assessing for haematuria and proteinuria is also useful. Should these investigations be done by ED or by the GP? You could argue both sides, but I would say if the patient’s there in ED, getting an ECG and a set of bloods is easy for us to do, and easier for the patient.

Signs of heart failure can be tricky and I always consider these patients as signs of symptomatic heart failure. These are your patients with pitting oedema to their nose, or shortness of breath as their lungs are so full of fluid. The patient with a smidge of fluid in their horizontal fissure I don’t count as having heart failure. Do you need an ECG? Well – if you’re looking for left atrial enlargement  then it’s probably useful, as is LVH.

We should treat asymptomatic patients with any target organ damage straight away. There’s a great NICE infographic about what treatment to start first, although whether the racial differences are based on science is unclear. Blood pressure management is standardly the domain of the GP, however I think these patients should be commenced on antihypertensives in ED to prevent the target organ damage getting any worse.

Asymptomatic hypertension. Faded archery target at back. 1. Look for hidden or target organ damage. Picture of papilloedema captioned papilloedema and retnial haemorrhage. Picture of frothy urine with dipstick on top. Proteinuria, haematuria, altered U&E. ECG with ST depression. LVH left atrial enlargement. 4AT in a greyed out oval acute confusion. RCEMLearning logo. 2. If any target organ damage consider starting treatment as per NICE.

Asymptomatic patients with no target organ damage should have ambulatory blood pressure readings taken before starting treatment, so they should be advised to see their GP at the next available appointment for a review. Many GP practices have a long wait for ambulatory readings so do suggest a home spyhg and recording twice daily readings – guidance here. We should take the opportunity to give healthy lifestyle advice.

But what if the BP is really really high?
The NICE guidelines no longer have treatment cut-offs above which you MUST treat, and instead they rely on target organ damage. Despite this, many of us feel really uncomfortable discharging a patient with a BP of 240/150 or similar with no treatment at all. These are patients who would benefit from SDEC or ambulatory care management to observe the effect of BP control.

The general aim is to gradually lower the blood pressure over several hours using oral agents. If the patient is reliably taking a medicine from one class, choose another in addition:

*Nifedipine MR 20-30 mg. Anecdotally people have seen hypotension as a result of nifedipine for hypertension so I always start low – and make sure treatment of the hypertension is truly indicated. I also wonder if people are prescribing the modified release dose, and then giving the immediate release dose. This calcium channel blocker can be taken twice daily for several days before switching to longer-acting equivalents such as amlodipine.
*Doxazosin 4-8 mg immediate release
*Metoprolol 25-50 mg (three times daily, can be replaced later)

You’ll note that amlodipine and review is NOT a strategy recommended. It wasn’t  recommended in 2018, and won’t be recommended now. Amlodipine is a calcium ion influx inhibitor of the dihydropyridine group (slow channel blocker or calcium ion antagonist) and inhibits the transmembrane influx of calcium ions into cardiac and vascular smooth muscle. After oral administration of therapeutic doses, amlodipine is well absorbed with peak blood levels between 6-12 hours post dose with absolute bioavailability of between 64% and 80%. There’s more discussion around this on twitter.

When you feel comfortable to discharge, the patient can be discharged to their GP with a prescription of the medication that achieved the improved control. If control is incomplete, the patient will need a review.

Why don’t we just give everyone IV and send them home?
Lowering the blood pressure too quickly can trigger cerebral or myocardial ischaemia. The BP should be lowered gradually to minimise this risk against the potential risk of cardiovascular events. There is no proven benefit from rapid reduction of blood pressure in patients with severe asymptomatic hypertension and most such patients can be managed as outpatients.

Why don’t we treat everyone regardless of whether there’s target organ damage?
There are risks associated with over medicalising everything, and with inducing hypotension. Confirming hypertension and trying lifestyle modifications before pharmaceutical management is preferred – and the GP is the expert in managing this.

Special Considerations

Hypertension in Pregnancy – follow the latest NICE guidelines and liaise with your obstetrician. This may be a sign of pre-eclampsia – do an urgent urine dip before discussion with O+G.

Hypertension with Acute Aortic Dissection –  Reducing the blood pressure is a mainstay of treatment for aortic dissection. You want the blood pressure to be around 100 -120mmHg systolic – the lowest tolerated (ie. still perfusing brain). Stage one is reducing the heart rate with beta blockers like labetalol. Stage two is vasodilation with things like GTN. Stage one must be initiated before stage two as otherwise as the BP drops, short term BP control mechanisms senses the BP drop causing a reflex tachycardia.

Autonomic Dysreflexia is an uncontrolled sympathetic response in patients with spinal cord injury, normally above T6. It can be triggered by correctable causes like constipation and urinary retention and these should always be looked for and treated before prescribing medication. For more details have a look at this review article here


Hypertension and Acute Stroke – it is unclear whether treating hypertension acutely is beneficial, but as hypertension is generally considered a contraindication to thrombolysis, many thrombolysis centres treat it aggressively. Hypotension risks ischaemic injury after acute stroke so hypertension should only be managed under close monitoring, ideally by the hyperacute unit. I suggest seeking specialist advice from the stroke unit before starting anything.

Sub arachnoid haemorrhage requires swift blood pressure control to prevent the risk of re-rupture. Your neurosurgeonprobably has a preferred agent.

Head Injury and Raised ICP may present with hypertension as part of Cushing’s triad. Treatment with mannitol or hypertonic saline may be indicated.

Hypertension and the Elderly is often a balancing act to manage. There are now less specific targets and in the elderly this is particularly important as the ‘high’ blood pressure could be all that sustains them from falling over because of their very stiff vasculature. The MDTea podcast has covered this well.

Hypertension in Children is increasing in frequency. Make sure you look carefully for renal causes and occult head injury, and refer to your friendly paediatric team – even if they don’t need acute management, these cases will need follow up.



Examples in Cases

Pete is a 42 year old overweight man. His blood pressure at a routine work medical was 180/120mmHg. He feels absolutely fine.
In ED I would accept the inevitability of this man being here, do bloods, ECG, urine dip and assuming they were all normal, send him on his way with lifestyle advice. Fundoscopy? I probably should but probably wouldn’t.

In GP, this is probably a telephone consultation because of COVID. I would ask:

1. Is this a genuine high BP?

  • What were the circumstances of his reading – had he rushed to get there? was it a one off reading? Did the medical outcome have consequences?
  • Has he measured his BP since?
    Does he wear a smart watch and measure all his vitals constantly?? If not genuinely high, have a conversation about healthy lifestyle and weight loss, and send him on his way.
  • If unsure, ask Pete to visit the machine in reception to measure his BP, height and weight and get baseline bloods (FBC, renal, liver, bone, HbA1c, thyroid and fasting cholesterol), urine dip and BMI.
  • If high, monitor – either ambulatory (best) or home monitoring. There’s some really good instructions on how to do this here – a resource well worth directing your patients too. There’s a great infographic you could also print out for your patients on the same site here. 

2. Patient education

Information sharing is super important to allow Pete to take control of his health. If assessment stretches across two appointments, I need to make sure he comes back. Needs to address why and how to control BP:

– risks and complications of hypertension

– factors that increase risk – high BMI, sedentary lifestyle, poor diet, smoking, alcohol, comorbidities including diabetes and hypercholesterolaemia, family history.

– that this could be a lifelong issue and to control his BP he may need tablets every day for the rest of his life

– management – medical and non-medical. See below.

– reassurance, that hypertension can be controlled and risk factors can be reduced, and we can help with this.

3. Treatment Plan

Medical and non-medical planning:

– put all the investigation results together

– check Pete’s QRISK2 (see here)

– initiate anti-hypertensives as per NICE guidelines +/- a statin

– round back on the lifestyle advice from the first consultation

– agree to see Pete back in 3 months to see how he is getting on with the medication, to check his BP review and for bloods.

– although he will be responsible for booking his follow up, set a diary note to check it happens

Carrie is a 98 year old lady who fell at home. Her blood pressure is 220/140mmHg. She’s got a lot of pain in her hip.
In ED I would provide analgesia and investigate the cause and result of the fall. This would involve ECG, bloods, CXR, hip x-ray and a urine dip (I know, asymptomatic bacteriuria is a thing in the >65s but it’s easier to do it and ignore the result than to debate not doing it… and in this instance it lets me know about target organ damage). I would be hesitant to provide any anti-hypertensives knowing that the BP was so high.
In GP I would send this patient to ED for x-rays and management of the hip!

Abhishek is a 69 year old with sudden onset central chest pain radiating to his back, as if he’s been unzipped. He’s quite uncomfortable. The CT scanner is broken and CT won’t be available for a few hours. He has no pericardial effusion or free flap noted on bedside echo, and his CXR is normal. You suspect acute aortic dissection. His BP is 220/140 and his HR is 80.
In this instance I would provide analgesia. When Abhishek was pain free if he was still hypertensive I would give some labetalol for rate control as I’m pretty convinced this is an acute aortic dissection – and as CT is delayed, think treatment is better.

Pallavi is a 52 year old lady with headaches. She had an argument at home, and felt a really strong headache afterwards so checked her BP at home and it was 180 / 100. She re-checked it and it went to 200/140.
In ED I would recheck the BP and explore the headache and the argument situation. I would be reluctant to start anti-hypertensive treatment.

Further Links

The Resus Room

About the Authors

Charlotte Davies and Liz Herrievan are ED Consultants, and members of the RCEMLearning blog editorial team. Phillipa Peto and Jasmine Lee are Acute Medicine and Renal Consultants. Kate Wesseldine is a GP trainee.