Question

Scenario: DW is a 65-year-old, 135 kg male who visited his primary care physician for a routine examination. His blood pressure was 158/100 mmHg and his heart rate was 71 bpm. Stroke volume and cardiac output were normal. Serum renin levels were in the normal range.   A chest x-ray revealed left ventricular hypertrophy. Other clinical findings were unremarkable.

For this problem, pharmacologic therapies include diuretics, ACE inhibitors, beta-adrenergic receptor antagonists, and vasodilators. Explain the physiological effects on the cardiovascular system for each of these 4 classes of drugs and why these could be helpful.

Answer 1

Patient is hypertensive and left ventricular hypertrophy. Categories of drugs used are diuretics, ACE inhibitors, vasodilators and adrinergic receptor vlockers.

Diuretics- These are standard antihypertensive drug more commonly used are thiazides. Mechanism of antihypertensive action is_1.initially diuresis reduces plasma and ecf volume,thus decreases cardicac output.2.subsequently compensatory mechanism to almost regain Na balance and plasma volume ;cardiac output is restored but fall imBP is maimtained by a slowly developing reduction in tissue peripheral registance(tpr).3.the reduction in tpr is most probably an indirect consequence of a small persisting Na and water deficit.The fall in BP is gradual over 2-4 wks.

High ceiling diuretics like furosemide can be used in low doses in cases of pulmonary edema in left ventricular failure.

2nd group are ACE Inhibitors _preferred group but now ARBs are preferreed over this.machanism of antihypertensive action is decreased production of angiotensin2;thus actions are _decreased aldosterone relese;decreased preload(dec cardiac output);decreased afterload(dec tpr);dilatation of vessels of kidney thus RBF is maintained(vasoconstricting action of angiotensin2 is antagonised);Regression of ventricular hypertrophy;decreased incidence of renal complications in high risk diabetic patients;increased cardiac output in CCF pts;and inc bradykinin level causes dry cough(ADEffect).

3rd group are adrenergic receptor blockers_2 parts_alpha and beta receptor blockers.

Alpha1 blockers like prazocin cause blockage of alpha1 in arterioles and venules causing dilatation ,dec tpr and hence dec BP with mild tachy cardia;major drawback is postural hypotension.

Beta blockers are mild antihypertensives_block cardiac beta 1 receptors_actions are_dec heart rate,and dec myocardial contractility and hence cardiac output; initially tpr increases due to action of beta 2receptors so little change inBP is seen but continued use leads to gradual adaptation ofvregistant vessels to decreased cardiac output,tpr;also dec SBP and DBP causes decreased BP.;dec Nor adrenaline release from sympathetic terminals due to beta receptor mediated release process;decreased renin release (beta 1 mediated);decreased central sympathetic out flow.Selective beta1 receptor blockers are preferred.

4 th group are vasodilators_hydralazine,minoxidil,diazoxide are used.thse are directly acting arteriolar dilators_decrease BP with tachycardia,dec renin release&fluid retention,coronary,cerebral and renal blood flow increased.

Sodium nitroprusside is rapidly acting vasofilator decreases both cardiac output and peripheral registance.

Thus these 4 classes of drugs can be helpful.