Hypertension

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Epidemiology
Pathophysiology
Longterm Treatment
Preoperative Considerations
Intraoperative Management
Postoperative Management

Epidemiology
-leading cause of death and disease in the western society
-overall prevalance is about 20-25%

pathophysiology
-long standing uncontrolled hypertension can accerlerate atherosclerosis
-chronic increased afterload may lead to concentric LVH and diastolic dysfunction

Possible mechanisms:
-vascular hypertrophy
-hyperinsulinemia
-abnormal increases in calcium concentration possibly from impaired renal excretion
-increased sodium concentration within the vascular smooth muscle
-increased arterial tone
-increased sympathetic tone
-increased renin-angiotensin-aldosterone system (RAAS)

Complications
-CNS : cerebrovascular accident (CVA "stroke")
-CVS : myocardial infraction, heart failure
-Renal: renal failure
-vasc : peripheral vascular disease

long-term treatment

Goal: decrease the progression of hypertension hence decreased complications (ex. CVA,MI,)

Drug therapy

-Beta Blockers
-Ace inhibitors
-Calcium channel blockers
-Diuretics

preoperative Considerations

History
-severity and duration of hypertension
-current drug therapy
-presence of complications
-myocardial ischemia
-ventricular failure
-impaired cerebral perfusion
-peripheral vascular disease

Signs/symptoms
-chest pain
-exercise intolerance
-shortness of breathe
-nocturnal dyspnea
-dependant edema
-postural light headedness
-syncope
-amarosis and claudication

Physical examination

-vitals
orthostatic hypotension implies
-volume depletion
-excessive vasodilation
-sympatholytic drug therapy

Ophthalmoscopic exam visual changes in retinal vasculature usually parallels the severity and progression of athersclerotic and hypertensive damange within other organs
-carotid bruits
-s4 gallop may be present in patients with LVH
-s3 gallop usually late finding in patients with CHF
-pulmonay rales usually late finding in patients with CHF

Electrocardiogram
-possible finding with longstanding hypertension
-evidence of ischemia
-conduction abnormailies
-old infarcation
-LVH
-LV strain

Chest x-ray
-normal chest xray does not exclude LVH
-boot shaped heart in LVH
-cardiomegaly
-pulmonary vascular congestion

Echocardiogram
-more sensitive in diagnosing LVH than other modalities
-evaluates ventricular systolic function and ventricular diastolic function

Labratory
-chemistry to rule out other causes of hypertension (ex.conns syndrome)
-evaulation of renal function

intraoperative management

OBJECTIVE: maintain stable blood pressure within 10-20% of preoperative levels
if marked hypertension (> 180/120) then maintain high level range (140-150/80-90)

MONITORING: most patients do not require special intraoperative monitoring

-arterial line patients with wide swings in blood pressure
surgical procedures associated with a rapid or marked changes in cardiac preload or cardiac afterload

-ecg monitor signs of ischemia

-urine output patients with renal impairment undergoing surgery greater than 2 hours

pulm art cath patients with hypertension may have reduced ventricular compliance secondary to LVH
therefore higher PAOP are generally needed (12-18) to maintain adequate LVEDV and CO

INDUCTION induction and intubation often are associated with periods of hemodynamic instability
-hypotensive response of induction and hypertensive response of intubation creates hemodynamic instability

Hemodynamic instability:
-induction: anesthetic agents tend to be cardiodepressant +/- vasodilation Hypotensive response
antihypertensive agents tend to be cardiodepressant +/- vasodilation

-intubation: direct laryngoscopy Hypertensive response
ETT intubation

Treatment of hypotensive response
-small doses of phenylephrine (25-50 ug)
-small doses of ephedrine (5-10 mg) if increased vagal tone

Treatment of hypertensive response to intubation
-deepening anesthesia before intubation
-short brief intubation ( duration has some correlation to the degree ofexaggeration hypertensive response)

Intravenous anesthetics
generally safe for induction for hypertensive patients
-benzodiapines
-barbituates
-propofol
-etomidate

induction should be performed under deep anesthesia yet avoiding hypotension

Several techniques for deep anesthesia induction include:
-volatile anesthetis for approx 5-10 mins
-bolus of opiod ( ex. 2.5 - 5 ug/kg)
-administering lidocaine (ex. 1.5mg/kg )
-beta blockade
-i.v Nitroglycerin
-topical anesthesia

-ketamine contraindicated because it may stimulate the sympathetic nervous system
increased sympathetic nervous stimulation may increase MAP

MAINTENENCE

-volatile anesthetics +/- N20
-balanced anesthetia: (volatile anesthetics +/- N20 + opiods + muscle relaxants)
-t.i.v.a.

volatile anesthetics vasodilate and allow for rapid and reversible titration of MAP
sufentanil may provide the greatest autonomic supression and control of blood pressure

Intraoperative hypertension
-exclude reversible causes
ex. inadequate anesthetic depth
hypoxemia
hypercarbia

Hypotensive agent depends on:
severity, acuteness and cause of hypertension
baseline ventricular function
heart rate
+/- bronchospastic pulmonary disease

Treatment of intraoperative hypertension

-beta blockers: patients with good ventricular function
accelerated heart rate
avoid in patients with bronchospastic disease
options:
- beta1 selective (ex. esmolol)
- beta nonselective (ex. propanolol)

mixed alpha/beta blockers able to decrease blood pressure without reflex tachycardia
avoid in patients with bronchospastic disease
ex. labetolol

calcium channel blockers nicardipine: useful in patients with bronchospastic disease
nimodipine: may be associated with reflex tachycardia
reflex tachycardia may be associated with myocardial ischemia

vasodilators nitroprusside: most rapid and effective in treatment in moderate-severe hypertension
nitroglycerin : less effective than NTP but useful in treating myocardial ischemia
hydralazaine: delayed onset but provides sustained blood pressure control
associated with reflex tachycardia

POSTOPERATIVE MANAGEMENT
-hypertension should be anticipated in patients with poorly controlled hypertension
-sustained increase in blood pressure may be contribute to:
-myocardial ischemia
-heart failure
-formation of wound hematoma
-dissruption of vascular suture line

-correctable contributing factors to hypertension:
-respiratory abnormalities
-volume overload
-bladder distension
-pain

once reveresible causes have been ruled out then drug therapy may be the next step