Investigations
1st investigations to order
blood chemistry
Test
Acute kidney injury may be the only sign of hypertensive emergency.
Result
may reveal elevated creatinine and urea
FBC with smear
Test
Microangiopathic haemolytic anaemia may occur in patients with hypertensive emergency and increases the risk of developing acute kidney injury.[70] Additional evidence for haemolysis may be obtained by checking a serum LDH, haptoglobin, and indirect bilirubin.
Result
may reveal schistocytes (red cell fragments) indicating the presence of haemolysis
urinalysis with microscopy
Test
Acute kidney injury as manifested by haematuria and proteinuria may be the only sign of hypertensive emergency.
Result
may reveal presence of red cells and protein
ECG
Test
If the patient has chest pain and there is ST elevation on the ECG, the patient should be sent for emergency revascularisation.
If the ECG is abnormal but the ST segment is not raised, biomarkers (high-sensitivity troponin), and echocardiogram are the first-line investigations in all patients to rule out ongoing ischaemia or infarction.
If the ECG is normal, aortic dissection should be considered in the context of unexplained chest pain.
Result
may reveal evidence of ischaemia or infarct such as ST- or T-wave changes
chest x-ray
Test
A chest x-ray is useful to assess for pulmonary oedema, left ventricular hypertrophy, and aortic dissection.
A plain chest x-ray is neither sufficiently sensitive nor specific for aortic dissection to be used as a diagnostic tool. If aortic dissection is suspected, urgent computed tomography angiography (CTA) with contrast should be ordered.
Result
may reveal evidence of pulmonary oedema indicating left ventricular failure or widened mediastinum indicating possible aortic dissection
Investigations to consider
thyroid function tests
Test
Indicated if signs/symptoms of hypothyroidism or hyperthyroidism.
Result
thyroid-stimulating hormone (TSH) high and thyroxine (T4) low in primary hypothyroidism; TSH low/normal and T4 low in central hypothyroidism; TSH low and T4 high in primary hyperthyroidism (e.g., Graves' disease); TSH high and T4 high in central hyperthyroidism (e.g., in rare pituitary tumours)
liver function tests
Test
Recommended in all women with suspected pre-eclampsia. Useful indicator of disease progression. Increased transaminase levels are partly diagnostic for HELLP (haemolysis, elevated liver enzymes, low platelets) syndrome.
Result
may be abnormal
cardiac enzymes
Test
Cardiac enzymes should be performed if acute coronary syndrome is suspected.
Result
raised in acute coronary syndrome
N-terminal pro-B-type natriuretic peptide (NT-proBNP)
Test
BNP should be measured if acute heart failure is suspected. If NT-proBNP levels are normal it is unlikely that the patient has heart failure.
Result
may be raised in acute heart failure
coagulation profile
Test
Coagulation profile should be performed if disseminated intravascular coagulation is suspected. Prolonged prothrombin time/partial thromboplastin time in addition to thrombocytopenia is indicative of progression to disseminated intravascular coagulation.
Result
may be abnormal
urine or serum pregnancy test
Test
Performed in women of childbearing age not known to be pregnant. All pregnant women presenting with hypertension and either proteinuria or evidence of systemic involvement require close assessment and monitoring for pre-eclampsia and its complications.
Result
positive in pregnancy
urine toxicology screen
Test
Performed in patients with suspected ingestion of illicit substances.
Result
may be positive for illicit substances
computed tomography angiography (CTA) scan
Test
If aortic dissection is considered possible, an urgent thoracic CTA scan with contrast is recommended.[64][65] For patients who cannot receive iodinated contrast, computed tomography (CT) without contrast is an acceptable alternative.
Transthoracic echocardiography (TTE) may be used in the accident and emergency department, intensive care unit (ICU), or operating room for acute proximal dissections if the patient is clinically unstable and there is any question about the diagnosis, or if CTA is unavailable or contraindicated.[64][65]
Result
evidence of two separate aortic lumens with dividing intimal flap in aortic dissection
transthoracic echocardiography (TTE)
Test
TTE may be used in the accident and emergency department, ICU, or operating room for acute proximal dissections if the patient is clinically unstable and there is any question about the diagnosis, or if CTA is unavailable or contraindicated.[64][65]
Result
evidence of two separate aortic lumens with dividing intimal flap in aortic dissection
renal ultrasound with Doppler
Test
Doppler ultrasound is usually the first-line imaging in clinical situations with high suspicion for renal artery disease. This may be followed by magnetic resonance angiography and/or CTA.[66] Due to the potential risks with invasive procedures, angiography is generally limited to visualisation and quantification of the stenosis before vascular intervention.[66]
Result
may reveal increased renal artery resistive indices
head CT without contrast
Test
Indicated if neurological complications are suspected. In patients suspected of having a stroke, CT or magnetic resonance imaging (MRI) of the brain is recommended to confirm the diagnosis of symptomatic ischaemic cerebral vascular disease. Typically patients initially undergo a non-contrast head CT, in order to exclude a brain haemorrhage and guide treatment.[67]
Result
may reveal evidence of infarct or haemorrhage
head MRI
Test
In patients suspected of having a stroke, CT or MRI of the brain is recommended to confirm the diagnosis of symptomatic ischaemic cerebral vascular disease. The mismatch between diffusion-weighted imaging and fluid-attenuated inversion recovery findings on MRI can be useful for selecting those who may benefit from intravenous thrombolysis.[67] However, MRI may take more than 30 minutes to complete, and is not universally available. The American College of Obstetricians and Gynecologists recommends evaluating headaches in pregnancy that warrant brain or vascular imaging with magnetic resonance techniques that limit the use of gadolinium.[55]
Result
may reveal evidence of infarct or haemorrhage
plasma renin activity and aldosterone level
Test
This test is an indirect measure of the activity of renin through measurement of the rate of production of angiotensin I, which increases as a result of renin stimulation. Aldosterone levels are usually measured at the same time. High plasma renin activity suggests hypertension from the vasoconstrictive effects of angiotensin.
Result
in primary hyperaldosteronism, renin activity will be decreased and aldosterone levels increased; in secondary hyperaldosteronism, both renin activity and aldosterone levels will be increased
spot urine or plasma metadrenaline (metanephrine)
Test
May be useful before initiation of drug therapy to rule out phaeochromocytoma. However, these tests need to be interpreted carefully, with consideration for possible confounding factors such as drugs (e.g., tricyclic antidepressants, clozapine, phenoxybenzamine, beta-blockers, sympathomimetics, buspirone) or major physiological stress.
Result
may reveal elevated metadrenaline levels
24-hour urine free cortisol
Test
Indicated when stigmata of Cushing's syndrome present.
Result
elevated in Cushing's syndrome
sleep study
Test
Sleep study may be considered in cases of resistant hypertension and also for patients with signs or symptoms of obstructive sleep apnoea.[34]
Result
may show results consistent with obstructive sleep apnoea
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