pharm ? re: reflex tachycardia

[snwflknurse]

Hoping someone out there can help me. I have a question I am having trouble with and can find nowhere in my book (or anywhere else for that matter). The question states:

Describe what causes reflex tachycardia. What types of drugs would you anticipate might cause reflex tachycardia.

The chapter we just got done with is Adrenergic Agonists. For drugs that would cause a reflex tachycardia, I have all drugs that work on beta 1 receptors, since these increase heart rate, strength of contraction. This would include the prototype epinephrine, as well as norepinephrine, isoproterenol, dopamine, and dobutamine, all of which are catecholamines.

The problem I am having trouble with is "what causes reflex tachycardia". Can anyone help me out here? thanks.

[jenrninmi, MSN, RN]

I know that distention of the bladder causes reflex tachycardia...

CATECHOLAMINES, like ADRENALINE, are RELEASED DURING STRESS, CAUSING AN INCREASE IN HEART RATE. DRUGS are a common cause of change in the heart rate and most anaesthetic drugs can do this. HALOTHANE affects the SA node and will also depress the force of contraction of the heart. ISOFLURANE, by contrast has little direct affect on the heart, but causes peripheral vasodilation of the blood vessels. This will then decrease the blood pressure, and hence produce a reflex tachycardia.

Also: Heart rate variation during quite inspiration and expiration is lost with autonomic dysfunction. Heart rate response to standing. In order to compensate for the decrease in blood pressure from the lying to standing position there is a reflex tachycardia which is maximal after ~ 15 beats. Blood pressure is restored to above baseline which causes a reflex brady cardia which is maximal after ~ 30 beats. Sympathetic

Also: Postural hypotension.

On standing the decreased blood pressure is usually compensated for by a reflex tachycardia and vasoconstriction, neither of these mechanism work well in autonomic dysfunction leading to a marked difference in systolic blood pressure between lying and sitting / standing. The normal is 30mmHg.

[snwflknurse]

yay, thanks! I did some more searching and found that it seems to be triggered by low blood pressure, whether the cause is from antihypertensives or from reflexes of other drugs.

hope i can pass this test tomorrow!

I know that distention of the bladder causes reflex tachycardia...

CATECHOLAMINES, like ADRENALINE, are RELEASED DURING STRESS, CAUSING AN INCREASE IN HEART RATE. DRUGS are a common cause of change in the heart rate and most anaesthetic drugs can do this. HALOTHANE affects the SA node and will also depress the force of contraction of the heart. ISOFLURANE, by contrast has little direct affect on the heart, but causes peripheral vasodilation of the blood vessels. This will then decrease the blood pressure, and hence produce a reflex tachycardia.

Also: Heart rate variation during quite inspiration and expiration is lost with autonomic dysfunction. Heart rate response to standing. In order to compensate for the decrease in blood pressure from the lying to standing position there is a reflex tachycardia which is maximal after ~ 15 beats. Blood pressure is restored to above baseline which causes a reflex brady cardia which is maximal after ~ 30 beats. Sympathetic

Also: Postural hypotension.

On standing the decreased blood pressure is usually compensated for by a reflex tachycardia and vasoconstriction, neither of these mechanism work well in autonomic dysfunction leading to a marked difference in systolic blood pressure between lying and sitting / standing. The normal is 30mmHg.

[jenrninmi, MSN, RN]

yay, thanks! I did some more searching and found that it seems to be triggered by low blood pressure, whether the cause is from antihypertensives or from reflexes of other drugs.

hope i can pass this test tomorrow!

Good luck!!:)