Overlapping meds & vaso-questions

nurseprnRN, BSN, RN · Dec 12, 2011

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1) ex. a patient has gravol ordered iv q4h and ondansetron iv q6h-q8h. if i gave the patient gravol at 0800 and the patient c/o of unrelieved nausea at 1000, would it be okay to give the ondansetron at 1000 (b/c they affect the body in different ways)...is this the same idea with pain meds like giving tylenol and 2 hrs later giving advil, b/c the two meds work in different ways? **please correct me if i am wrong! this kind of decision-making for medications makes me quite uneasy! *if two meds are ordered for the same thing, can it be implied that the doctor wants you to try one and than the other or use them together as needed (if safe of course)?"

short answer: yes, it's ok, but if when you look up the meds you find any reason they should not be given concurrently, be sure to ask the prescriber about that. there are, for example, many drugs with antiallergic effects that you don't think of as classic antihistamines. everybody knows about diphenhydramine (benadryl), but sometimes you need an everything-but-the-kitchen-sink approach and you see famotidine, cetirazine, doxepin, and hydroxyzine, and zafirlukast (accolate) thrown at a resistant condition. all are good with allergic reactions.

"vasoconstriction & vasodilation-> why do the vessels vasoconstrict in a stress response, i understand that the peripheral vessels will constrict to shunt the blood to the vital organs. but wouldn't the vasoconstriction actually work against the body which is trying to get more perfusion of oxygenated blood?? i hadn't really thought of it in so much depth, but now i'm questioning everything i know!."

the peripheral vasoconstriction shunts blood to more important organs that need more of it in an emergency or major stress, increasing bp to those central places (brain, heart, lungs, renals) and decreasing it to less-important places (skin, skeletal muscle, gut). the muscle can actually do some work, enough to help you run away from the tiger, maybe, on less oxygen, going anaerobic; hearts and brains, not so much. peripheral vasoconstriction also helps a little bit by making your peripheral arteries and capillaries a little less susceptible to trauma, makes them smaller-- less bleeding. it's not much, but in some circumstances it could be enough.

also, why does co2 cause vasodilation?? (if this is similar to vessels constricting to shunt blood, wouldn't the vessels want to constrict to shunt blood back to lungs to get rid of co2??)"

co2 causes dilation because it's acidic; another acidosis cause, anaerobic metabolism with lactic acid produciton, implies lack of decent (or enough for conditions) arterial flow. if you want to do a fun demo someday, pick someone who is very fair, with very translucent skin (redheads are good for this). have her raise her hand above her shoulder and make a fist hard and fast, repeatedly, as fast as possible, fast-fast-fast!!, while you compress her brachial artery without occluding venous return. she will cramp up; tell her to keep going until she totally can't do it any more. then release the artery. you will be able to see how the experimental arm is markedly flushed-- vasodilation. it's trying to flush away the accumulated co2 and, perhaps, the beginnings of lactic acidosis. since your lungs' primary job is excreting co2, not, as generally supposed, getting o2 in, normal circulation and lung function will take care of the excess in short order.

glovedgoddess · Dec 12, 2011

Thanks for your reply!

I'm just still a little bit stuck on the vasodilation/vasoconstriction...Your example of holding the brachial artery and witnessing vasodilation, I'm confused why it would vasodilate if the body wants to get rid of the co2, wouldn't it want to vasconstrict to build up more pressure to get blood flowing more quickly to the lungs?? (how does the vasodilation facilitate excretion of the c02?)

turnforthenurse, MSN, NP · Dec 12, 2011

Thanks for your reply!
I'm just still a little bit stuck on the vasodilation/vasoconstriction...Your example of holding the brachial artery and witnessing vasodilation, I'm confused why it would vasodilate if the body wants to get rid of the co2, wouldn't it want to vasconstrict to build up more pressure to get blood flowing more quickly to the lungs?? (how does the vasodilation facilitate excretion of the c02?)

Vasodilation = increased blood flow to the area = helps facilitate excretion of the CO2.

nurseprnRN, BSN, RN · Dec 13, 2011

"you will be able to see how the experimental arm is markedly flushed-- vasodilation. it's trying to flush away the accumulated co2 and, perhaps, the beginnings of lactic acidosis. since your lungs' primary job is excreting co2, not, as generally supposed, getting o2 in, normal circulation and lung function will take care of the excess in short order."

i hoped that saying, "normal circulation and lung function" would do the trick would explain that, but i am sorry i didn't make it clearer. the vasodilation increases the blood flow in and out of the recently-hypoxemic area, thus flushing out the excess co2 production. it will get to the lungs quite fast enough with normal circulation from there-- in seconds, really.

local problem, local solution-- local hypoxic episode with local hyperemia will fix it up jus' fine. hope this helps & thanks to turnforthenursern:up:.

glovedgoddess · Dec 13, 2011

yup makes sense! Thanks for taking the time to answer my questions :)