Does Levophed increase CVP? Need nice physiology type answer.

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    I had a patient the other day that was on 2 mcg/min of levophed with b/p of 110/50. His blood pressure 2 hours into the shift drops into the 60/40. I increased my levophed to 10 mcg/min and his blood pressure responded to 115/50. When I alerted the resisdent to this rapid increase in levophed he asked for a CVP. I measured a cvp of 12 (pt on vent with peep of 5) After informing him of the CVP, he states that b/c the CVP is adequate no fluid bolus is needed for the blood pressure drop(lasix drip on pt and urine output 50ml/hr). My question is if increasing my levophed causes an increase in CVP because of the increase peripheral vascular resistance(increasing central venous blood return). This would make the cvp measurement after the increase in levophed an inacurate measure of fluid volume staus. Can someone help me with a sound physiologic type answer?

    thanks
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    I would have to agree that the cvp was a bit of an illusion. Your reasioning sounds spot on to me. Did you happen to know what his cvp was at the time of the BP drop? Making a decision like that based on a single cvp reading is a little too simplistic. For instance... I am wondering why this patient was on a lasix drip. Has he been volume overloaded and has some renal insufficiency? If so they may want to use the drugs to control his BP rather than fluids. Why is he on levo anyway? With only 50 cc/h UOP and BP instability my instinct would be to give fluids but the reference to the Lasix drip makes me hesitate. Did his lungs sound wet or was he dry?

    So many questions and Critical care is often like putting together a living breathing jigsaw puzzle. Oh yeah, how were his pulses? People hold their pulses better on Levo if there is a little fluid in the tank.

    Remember you can also use colloid to expand volume and wean your pressors. Hespan is 5oocc's but is hard on the kidneys. Albumin is often a good choice and is small in volume. There is also plasmanate and plasma protein fraction. If he has had volume overload problems and renal insufficiency then he may have plenty of fluid in his tissues that needs to be shifted into his intravascular space. Colloids are the intervention of choice here.

    Or is it possible that they have dried him out too much with the lasix drip as evidenced by the drop in BP and a UOP of only 50 cc's/hr. In that scenario the cvp is certainly an illusion and this patient needs fluid. This is where daily weights and serial daily fluid balance calculations come in along with your physical assessment skills. Determining volume status in a critical patient is rarely as simple as taking a cvp reading. When discussing the patient with a doctor (especially a resident) it is a good idea to have a handle on all of these issues.

    P.S. I don't expect an answer to my questions. They are simply food for thought.


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