Don’t blow a gasket! #FOAMed #FOAMcc

Introduction

This is a very common scenario on the ICU. Hypertension and what to do about it…if anything?

There’s a cohort of diversity in front of you:

the post-operative patient who had their anti-hypertensives stopped prior to surgery, but now has a blood pressure of 165/95mmHg
the elderly patient with a list of comorbidities and an incidental persistently high blood pressure of 175/100mmHg
the post-operative patient with an arterial trace of 205/115mmHg

So, are we merely treating the monitor to make ourselves feel better, or are we actually intervening to minimise the all important morbidity?

A preventative approach to post-operative hypertension, such as substituting usual medications for long-acting preparations in the immediate days pre-operatively is possible, but often an opportunity missed. Patients having their antihypertensive medication discontinued peri-operatively or at admission to intensive care should have their prescriptions reviewed regularly, aiming to restart normal medications as soon as feasible. This is particularly the case if their blood pressure is in excess of 180mmHg systolic. I believe this is an area we are all guilty of overseeing often and it’s where our brilliant pharmacists come in…so listen to them!

So, to get back on track we need to focus in on the morbidity associated with uncontrolled hypertension. Why are these elevations of any importance? Is leaving it and just watching going to render the patient at an increased risk of morbidity?

Such elevations are known to increase cardiac risk, particularly if end-organ damage has occurred. Immediately post-operatively, patients often experience a rise in systolic blood pressure of between 20-30mmHg, which often settles back to baseline within a few hours without intervention. But all patients should be assessed for easily correctable causes of hypertension – are they analgesed, is their catheter draining, are they agitated, is their stomach full requiring a NG tube, or has a new medication caused hypertension? Take a peek at the drug chart for precipitant pharmacology, i.e. monoamine oxidase inhibitors, steroids, tricyclic antidepressants or even non-steroidal anti-inflammatories. A persistent blood pressure above 180/110mmHg that is not due to other reversible causes requires relatively immediate intervention with intravenous medication to obtain rapid control. It is also prudent to ensure you re-initiate their usual medications to target a blood pressure of <140/90mmHg.

Immediate Hypertension Control

Immediately acting intravenous drug preferences include:

Esmolol
- load 500-1000mcg/kg then 25-50mcg/kg/min
- ultra-short acting and very useful in post-operative hypertension causing angina, but should be avoided in acute heart failure.
Labetolol
- 20mg bolus then 1-2mg/min infusion titrated to blood pressure
- drug of choice for post-operative blood pressure control, acting within 2 minutes and lasting 2-4 hours with titratable infusions giving good results.
Nitroglycerin
- up to 200mcg/min
- infusions act in 2-5 minutes and effects last 10-20 minutes but should only really be used as an adjunct to other therapies in pulmonary oedema or acute coronary syndrome.
Nicardipine
- 5mg/hr – max 15mg/hr
Enalapriliat
- 1.25mg 6 hourly – max 5mg 6 hourly
- generally avoided in post-operative hypertension due to a slow onset and long duration of action, as well as precipitating worsening renal function in hypovolaemic patients or acute kidney injury.
Nitroprusside has gone out of fashion owing to risk of cyanide toxicity after only 3 hours of infusion so should only be used if other agents are not available.

Patients who cannot take oral medications for whatever reason can be switched temporarily to parenteral preparations such as furosemide if taking diuretics, esmolol or propranolol as alternative beta blockers, enalaprilat for ACE-inhibition, or nicardipine as a blocker of calcium channels.

Long-term Hypertension Control

NICE Guidelines for hypertension change regularly so you can be forgiven for not having a clue which ‘stage’ of hypertension is treated and which agents are in vogue. Currently hypertension is divided into three stages, each more severe than the last and treatment is tailored at reducing blood pressure to a target of less than 140/90mmHg, (but of course there are caveats). GPs have the luxury of ambulatory or home readings and start medication after confirming hypertension outside the clinic room (numbers in brackets). Intensivists however have the benefit of invasive arterial pressure monitoring for accurate (and sometimes worrying) beat-to-beat reading of blood pressure.

Normotension

<140/90mmHg (<135/85mmHg)

Stage 1 Hypertension

<160/100mmHg (<150/95mmHg)

Stage 2 Hypertension

<180/110mmHg

Severe Hypertension

>180/110mmHg

Treatment of stage 2 hypertension is desirable, as is stage 1 hypertension

if end-organ damage or co-existing renal/cardiac/vascular disease/diabetes is present
if 10 year risk of cardiac disease is above 20%.

We can be slightly more generous in the over 80 age group and typically aim for <150/90mmHg as a target blood pressure owing to a less compliant vascular tree.

The best way to think about managing stable hypertension in hospital and in the community is by applying a menu of drugs. But the first question is: “Do you really need to do anything at all?” Always consider the context of hypertension and whether it will settle without treatment. Post-operative and acutely unwell patients may be hypertensive for many reasons that should be addressed first. Only after rectifying problems can you think about what they need from the pharmacological menu using a step-wise approach to therapy. Here’s the menu….

What’s on the Menu!?

~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Starter (Step 1)

ACE-Inhibitor or Angiotensin 2 Receptor Blocker (people under 55 years old favour this option)

Calcium Channel Blocker or Thiazide-type Diuretic (people over 55 years old or black have a less responsive renin-angiotensin system)

Main (Step 2)

ACE-Inhibitor or Angiotensin 2 Receptor Blocker

AND

Calcium Channel Blocker or Thiazide-type Diuretic

Dessert (Step 3)

Is there enough starter and main on board?

No – titrate up to maximum

Yes – triple therapy of ACE-Inhibitor/A2RB, a Calcium Channel Blocker and a Thiazide-type Diuretic

Afters (Step 4)

Some may need more – conventional diuretics (furosemide, spironolactone); alpha blockers (doxazosin); beta blockers; centrally-acting agents (clonidine) are options

Extras

Supplement anti-hypertensive choices with lifestyle advice – dietary behaviour/salt intake, exercise, smoking/alcohol, caffeine intake

Look for end-organ damage – 12-lead ECG, urinalysis, fundoscopy and cholesterol / glucose / urea / electrolytes to predict 10 year cardiovascular risk

Special Occasions

If still not controlled or age <40 years consult a specialist for further management and investigation of hypertension.

~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Most people should have a once daily drug where possible, though occasionally patients may feel overwhelmed and have side-effects from a large dose which could be given in divided doses.

We all know that in acute kidney injury ACE-Inhibitors should be withdrawn temporarily, but in stable patients with diabetes or chronic kidney disease (CKD) ACE-Inhibitors are actually reno-protective, slowing progression of proteinuria and should be commenced at the earliest opportunity. In the special cases of diabetes and CKD hypertension guidelines are unchanged, however in diabetes stricter control is desired, targeting 140/80mmHg or 130/80mmHg if end-organ damage is apparent.

Hypertensive Urgency or Emergency?

So how about the case of the patient with a new severe hypertension exceeding 200mmHg? Is this an emergency or ‘urgency’? Both definitions feature severe hypertension, but the key difference is in the signs and symptoms.

EMERGENCY

A mild headache is common when blood pressure reaches significant highs, but features suggesting end-organ dysfunction make this an emergency.vascular bleeding

encephalopathy
chest pain
shortness of breath
raised intra-cranial pressure
- retinal changes, vomiting, papilloedema
Any of these in pregnant women

To clarify things further, tests of end-organ damage should include:

12-lead ECG
chest radiograph
troponins
electrolytes
urinalysis

Specific remedies in certain circumstances:

Hypertensive encephalopathy
- intravenous nitroprusside (0.25-0.5mcg/kg/min) or
- nicardipine (5mg/hr – max 15mg/hr) for rapid control
Cardiac failure
- diuresis with furosemide plus vasodilation with GTN infusion (5mcg/min – no upper limit) reduces cardiac afterload.
- Avoid beta blockers (i.e. labetalol) which suppress myocardial contractility, while hydralazine increases cardiac workload and ischaemia.
Acute Coronary Syndrome
- reduce myocardial workload and improve oxygenation with intravenous nitrates, esmolol and nicardipine.
Aortic dissection
- target systolic pressure of 100-120mmHg
- beta blockers reduce heart rate and aorta shear stress (esmolol, labetalol, metoprolol)
- vasodilators reduce afterload (nitroprusside)
Sympathetic over-activity
- withdrawing certain drugs causes reflex hypertension (clonidine)
- Short-term intravenous cover helps while restarting drugs
- Drug overdose or autonomic dysfunction is controlled with nitroprusside and benzodiazepines
- Avoid beta blockers which cause unopposed alpha vasoconstriction

URGENCY

Here, end organ damage is absent, most advocate 30% reduction in blood pressure in the hours or days, aiming for less than 140/90mmHg ultimately by following NICE guidelines. This approach avoids hypotension that causes impaired organ autoregulation or ischaemia. Consider a soft approach first i.e. correct the correctable causes mentioned above, provide a quiet and restful environment (this can settle blood pressure by up to 20mmHg prior to drugs). The best choices for slow reduction in blood pressure are oral furosemide in volume replete patients, captopril or amlodipine. Standard hypertension management for long-term blood pressure maintenance can then be initiated and continued in the community.

Conclusion

All of this really summarises what to do and what not to do in seeing hypertension oon the ICU. The recipe we offer simplifies things a little. The bottom line there is, we get nagged by it, but it’s only worth lowering it if you think it is actuallyrefractory to targeted management of causative factors. And also, more importantly, is the patient high risk anyway, waiting for even more morbidity as more end organs get damaged.

Treat carefully and sensibly folks!

Written By Dr Ben Noble – ICU Trainee

Edited by JW

December 2016 (almost 2017!!!)