The trigeminocardiac reflex a comparison with the diving reflex in humans

ACUTE AND CHRONIC ORTHOSTATIC INTOLERANCE

Reflex tachycardia and blood pressure

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The student should be able to explain or describe ;, reflex tachycardia and blood pressure. The classes of pharmacologic agents used to treat hypertension as well as which of these agents are first and second line agents.

The mechanisms of action by which antihypertensive drugs reduce blood pressure. Of the top topiramate description and side effects by prescription sales see http: The goal of therapy is not the reduction in blood pressure per se. Rather, it is to decrease the end organ damage and subsequent pathophysiology that occurs with sustained, untreated elevated blood pressure.

Hypertension is a unique clinical problem because it is an asymptomatic disease. Therefore, if therapy with antihypertensive drugs causes unpleasant side effects, reflex tachycardia and blood pressure, patient compliance could be reduced. This report can be found at: Elevated blood pressure is the most common chronic illness in the United States, affecting more than 50 million people.

There are differences in the prevalence of this disease which are based on age, race, sex and socioeconomic status. Guidelines for the classification of hypertension are as follows:. Untreated hypertension leads to end-organ damage and death. Reduction of blood pressure is associated with a decrease in the morbidity and mortality of other cardiovascular diseases such as stroke, congestive heart failure, left ventricular hypertrophy reflex tachycardia and blood pressure renal failure, as well as an increase in the quality of life.

In addition to pharmacologic means to lower blood pressure, reflex tachycardia and blood pressure, life-style modifications can also decrease blood pressure, reflex tachycardia and blood pressure. These would include weight reduction, smoking cessation, decreases in alcohol consumption and an increase in regular exercise. These tables are not intended to be all inclusive but rather to give you an idea of number of drug classes and combination products available to treat hypertension.

The points listed below have been previously discussed. Key features are reiterated for emphasis. The major diuretic class used in the long term treatment of hypertension is the thiazides. Thiazides are one of the cornerstones of hypertensive therapy and are considered first line agents in the treatment of elevated blood pressure.

Numerous clinical studies have shown these agents to decrease the risks of other cardiovascular diseases. Diuretics can be used as monotherapy for mild hypertension as well as in combination with other antihypertensives. For examples see the above list of combination products for hypertension.

Many, but not all, antihypertensive agents induce water and salt retention. Diuretics counter this increase in fluid retention, reflex tachycardia and blood pressure. This allows for lower concentrations of both drugs to be used. Thiazide diuretics are particularly effective in African Americans and the elderly. These agents are available as generics, thus are not very expensive.

Potential side effects include hyponatremia, hypokalemia and the potential for rhythm disturbance, glucose intolerance and a reduction in the efficacy of oral hypoglycemic agents, impotence and increases in lipid and cholesterol levels. Despite these potential deleterious effects on glucose and lipids, diuretics can still decrease the risks of hypertension in diabetic patients or in those elevated lipids and cholesterol.

These agents increase uric acid levels and should be used carefully in individuals with gout, reflex tachycardia and blood pressure. Loop diuretics would be reserved for more severe forms of of hypertension. ACE inhibitors and AT1- receptor antagonists are first line agents for the treatment of hypertension. These drugs might have particular benefit in patients who also have congestive heart failure or following myocardial infarction.

Side effects to be aware of include: These side effects are less likely to occur with AT1-receptor antagonists. This drug, which inhibits the RAS in a unique manner, was approved for clinical use in March Aliskerin is a direct inhibitor of renin. Renin, of course, converts angiotensinogen to angiotensin I. Aliskerin binds to the active site of renin and blocks its catalytic activity. As a result the circulating level of angiotensin II is decreased.

This results in an inhibition of the biological activity of angiotensin II. Aliskerin can be used alone to decrease systemic arterial blood pressure. Clinical studies have also shown that aliskerin can be used with other antihypertensives agents such as diuretics. Beta blockers are first line agents in the treatment of hypertension. These drugs have reflex tachycardia and blood pressure effects on cardiovascular function and have a variety of cardiovascular and noncardiovascular uses.

They also block the release of renin mediated by beta1-receptors. There are selective and nonselective beta blockers. Prominent side effects include sedation, fatigue, and bradycardia. In addition, all beta blockers mask the tachycardia associated with hypoglycemia. As a result, the diabetic patient is deprived of one of the earliest physiologic responses to hypoglycemia. Despite this action on glucose or potential effects on lipid levels, beta blockers have been shown to be effective in improving outcomes in diabetic patients especially selective beta1-blockers and patients with elevated lipids.

Recall that a disadvantage of nonselective beta blockers is the fact that they will block beta 2 receptors associated with airway or vascular smooth muscle. Possible side effects for verapamil and diltiazem include bradycardia and atrio-ventricular node block. In general, patients tolerate diltiazem better than other calcium channel blockers.

The most significant drug interactions are with other drugs that have inhibitory effects on cardiac output beta-adrenergic blockers or conduction across the AV node beta-adrenergic blockers, digoxin. The dihydropyridines have a high incidence of side effects directly related to vasodilation, including edema and headache.

Reflex tachycardia due to rapid lowering of blood pressure can be a serious problem with some dihydropyridines. Reflex tachycardia and blood pressure and its analogs are selective alpha1-receptor blockers. These drugs are of particular benefit in hypertensive males who have BPH. Treatment with these drugs can result in fluid retention as a response to the lowering of blood pressure.

The hypotensive action of prazosin is decreased as a result of the expansion of plasma volume. Another side effect is first dose syncope and orthostatic hypotension.

These agents stimulate alpha 2 receptors in the nucleus tractus solitarius NTS to decrease sympathetic outflow to the heart and blood vessels resulting in a decrease in peripheral vascular resistance. These drugs have side effects typical of agents that work in the CNS including sedation, fatigue, dry mouth and sexual dysfunction. Methyldopa causes hemolytic anemia. The use of hydralazine has decreased due to the introduction of safer, more effective agents.

Hydralazine can induce a Lupus-like syndrome. Other side effects are typical arterial vasodilator side effects including headache and tachycardia. Hydralazine is not effective alone in the treatment of hypertension, reflex tachycardia and blood pressure. This is because of reflex tachycardia and water and salt retention.

Beta blockers and diuretics must be given to blunt these effects. Hence, hydralazine and minoxidil are reflex tachycardia and blood pressure for the treatment of moderate to severe hypertension and only then in combination with these other drugs.

This is an agent that has not been previously discussed. Minoxidil is also an reflex tachycardia and blood pressure vasodilator. Like hydralazine, minoxidil is reserved for the treatment of moderate to severe hypertension. It has typical arterial vasodilator side effects. In addition, minoxidil also causes hair growth. It is marketed as Rogaine for this use. Drug metabolism and distribution are altered.

Therefore, begin treatment with smaller doses. While beta blockers and diuretics have been proposed prozac and dramamine particularly effective in the elderly, any of the recommended drugs in the treatment algorithm can be used in the elderly. Hypertension is more prevalent and severe. There is also an increase in the incidence of diabetes, stroke and renal failure.

Diuretics are particularly effective in African Americans. ACE inhibitors are less effective. These agents blunt the hypotensive response to a variety of antihypertensives.

Hypertensive crisis is an elevation in blood pressure in which diastolic pressure exceeds mmHg. In the presence of ongoing end-organ damage this is referred to as a hypertensive emergency.

Without such complications, it is referred to as a hypertensive urgency. Hypertensive emergencies require blood pressure to be reduced within a few hours. The blood pressure in hypertensive urgencies can be lowered over a period of days. Intravenous medications are often used to treat these conditions. Some agents are used in the chronic treatment of hypertension while tumeric and colon cancer are reserved for hypertensive crises.

 

Reflex tachycardia and blood pressure

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