Understanding Inotrope Indications

[Catticus11]

So I've had patients who have CHF and receive weekly Milrinone infusions. I've also had patients who are awaiting Heart Transplants but weren't on any inotrope, but did have lower-ish BP.

I've had patients with new cardiogenic shock who were placed on an Impella with no inotrope. While I've had patients in a new acute cardiogenic shock with an IABP but on Dobutamine.

So yeah, I'm having trouble understanding the key take-aways for inotrope use. I understand the desire to avoid increasing myocardial oxygen demand that goes with inotrope use, but I'm having a bad time understanding why they are used and why they're not.

Sorry if this a dumb question!

[ghillbert, MSN, NP]

Overall, you want to maintain adquate end-organ perfusion. To that end, you will treat their disease etiology and comorbidities.

Cardiogenic shock with end organ malperfusion, low EF, low CI -you need to increase cardiac output. Often they have concomitant RV dysfunction and fluid overload, so you can't use as much fluid as they really need (Starling's law) to keep their cardiac index adequate for their tissue requirements. In that case, you fill the tank as much as you dare from a fluid perspective (CVP 10-15 ish), then you add some pump assistance with epi, dobutamine, milrinone.

The decision of WHICH inotrope is complex and depends on each patient's issues - for example, CGS with biventricular failure and elevated PA/RA pressures >> you may want to use dobutamine or milrinone but have inadequate systemic blood pressure to do so. So you may use dopamine instead. Or they may have tachyarrhythmias with one inotrope, so you try another. Or maybe they are acidemic and you don't want to worsen that with escalating inotrope gtts > so you use an IABP to reduce myocardial O2 demand and increase myocardial perfusion instead (or Impella, or Centrimag or other LVAD/ECMO etc).

There are many, many papers which can show you a decision algorithm for how to choose when and which drug to use. Best way for YOU to learn that is to clearly understand the pathophysiology of what you are trying to treat and reverse. Your job is to optimize tissue perfusion and minimize secondary complications. Choose the least invasive option to give you the result you're after.

Things to consider:

- High or low LVEF? (do you need pump or squeeze?)

- BP adequate or not?

- RV good or bad? (do you need a drug with pulmonary dilation such as dobutamine or milrinone?)

- Cardiac index and SvO2 adequate or not? (renal, liver function preserved or at risk? Mental status preserved?)

- Volume status high or low?

- Rhythm issues or not?

- Coronary perfusion issues? (eg. CGS due to MI - do you need revascularization, do you need nitroglycerin, do you need IABP or Impella to offload LV and improve coronary perfusion?)

- Comorbidities that would prohibit mechanical support? eg severe PVD, inability to anticoagulate, etc

Some resources:

- 2013 ACCF/AHA guideline for the management of heart failure

- The Role of Inotropic Agents in the Treatment of Heart Failure

- PubMed Central, Table 1: Circulation. 2