Hypertensive Crisis Flashcards
what is a hypertensive crisis
systolic BP >180/110 either diastolic or systolic
Differentiate hypertension urgency vs emergency
Urgency BP >180/110 with progression to end organ damage
Emergency BP >180/110 with progression to end organ damage
Describe proposed mechanisms of acute elevation in
BP involved in urgency and emergency
Thought to be secondary to elaboration of hormonal substances like chatecholamines and the activation of RAS leading to severe vasoconstriction
Marked increase in BP leads to sheer damage of vasculature and activation of clotting cascade. More sustained hypertension can lead to fibrinoid necrosis of the arterioles and lost of autoregulation
Discuss autoregulation
Blood pressure is a balance between cardiac output and total peripheral resistance. Hypertensive crisis are usually due to rapid increase in vascular resistance
Autoregulation is the phenomenon by which vascular beds perfusion pressure constant for a range of systemic blood pressures.
Chronic high blood pressure will shift the lower and upper boundaries of this to the right. As such they will tolerate higher blood pressures better but will be more susctible to hypotension that would be easily tolerated in a normotensive patient. It is therefore important when neurological symptoms appear secondary to hypertensive emergency to only lower the systolic by 20-25% from presenting levels to ensure nil neurological damage.
Discuss volume status of patient with hypertensive emergency in general
In general hypertensive emergency patient are fluid deplete due to pressure natriuresis. This relative hypovolaemia activates the RAS and the sympathetic nervous system which exacerbate the condition
Discuss ECG changes that can occur with lowering of BP in hypertensive emergency
Non specific t-wave flattening or inversion can occur and while it may reflect true ischaemia is thought to represent decrease in ventricular chamber size. This will occur regardless of agent used
Discuss possible presentation of hypertensive crisis
CVS: aortic dissection left heart failure MI Unstable angina
Neuro: CVA -- thrombotic subarach interparenchymal htn encphalopathy
Micelanneous: Phaeo Mao overdose Pre-eclampsia renovascular hypertension
Discuss general approach to blood pressure management
Insert art line especially if soidum nitroprusside is being used as an infusion
neurological emergency should be reduced over hours compared to minutes if cvs
Discuss approach to neurological presentations
avoid antihypertensive that can alert mental state (clonadine, methyldopa, reserpine)
Employ short acting agents and be prepared to reduce IV dose if neurological symptoms worsen
Start with sodium nitroprusside to aim diastolic under 140, then wait 20 minutes for diastolic to 120-140 or if sytsolic greater then 230 then start labetalol
Discuss approach to cardiovascular emergency
In patient with left sided failure and htn sodium nitroprusside and nitroglycerin infusion have been effective but sodium nitro works quicker
With unstable angina nitroglyceron is preferred due to coronary artery dilatory affect and less coronary artery steal syndrome
Can use B blocker esmolol and labetalol for rate control and further reduction in BP
Discuss the use of diazoxide in hypertensive crisis
Thiazide diuretic
Some patient experienced hypotensive episode with use of this drug needed pressor support where as other had worsening of angina (due to increase in heart rate)
Also can cause hyperglycaemia (thiazide) fludi retnetion and tachycardia.
Also increases shear stress and should not be used in dissection
Discuss hydralazine and its use in hypertensive crisis
Acts directly on smooth muscle primarily in resistance arterioles
Does cause reflex tachy and should not be used in unstable angina, Mi or dissecton
There is a short latent period of 5-15 then a precipitous fall in blood presure with antihypertenive effect lasting from 10-12 hours
used to be drug of choice in pregnancy but risk of precipitous and unpredictable BP drop maybe harmful to foetus
Discuss labetalol and its use in hypertensive crisis
Has both Alpha and beta blocker components
ratio of Alpha to beta depends on delivery
Oral it is 1:3 A:B and IV is 1:7
Does not cause reflex tachy
should be avoided in left heart failure
Discuss esmolol and its use in hypertensive crisis
Very short acting B blocker may be administered IV as bolus or infusion
elimination half life of 9 minutes it is metabolised by RBC esterases oblviating the need for renal or hepatic monitoring
Unlike labetalol has nil direct vasodilatory affect – works by reducing inotropy and heart rate
Should again not be used in left heart failure
Discuss nitroglycerin and its use in hypertensive crisis
Nitrate –> CGMP and vasovenodilation
at low doses mostly veno then at higher doses vaso
risk of methaemaglobinaemia – also reflex tachy
drug of choice for unstable angina also good for heart failure MI
