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In this lesson, we'll go over the medication dopamine and all of its effects, including indications, precautions and contraindications, and adult dosages. And at the end of the lesson, we conclude our look at the various access routes for medication delivery.
Dopamine is a naturally occurring catecholamine – any of a class of aromatic amines that includes a number of neurotransmitters – that has direct alpha- and beta-adrenergic effects depending on the dose administered.
When medium doses are administered, like between 5 and 10 mcg/kg per minute in adult patients, dopamine will act directly on the beta 1 receptors, which causes an increase in both myocardial contractility and heart rate.
Pro Tip #1: Contractility is the inherent strength and vigor of the heart's contraction during systole. According to Starling's Law, the heart will eject a greater stroke volume at greater filling pressures. For any filling pressure, the stroke volume will be greater if the contractility of the heart is greater.
When dopamine is administered in doses greater than 10 mcg/kg per minute, the alpha receptors are typically stimulated. This causes an increase in systemic vascular resistance, also known as vasoconstriction.
Dopamine Indications
Now let's take a look at dopamine indications.
Dopamine can be quite effective in treating hypotension when there are signs and symptoms that the patient is in shock and is usually used as a second-line drug for symptomatic bradycardia after atropine.
Dopamine Precautions and Contraindications
Dopamine has a couple precautions and contraindications to be aware of.
Pro Tip #2: Dopamine can cause tachyarrhythmias and, as already mentioned, excessive vasoconstriction, which means that it should be used with caution in any patients who are suffering from cardiogenic shock with associated symptoms of congestive heart failure.
Warning: It's vitally important to correct hypovolemia with volume replacement before initiating dopamine therapy.
Adult Dosage of Dopamine
Now let's look at the adult dosage of dopamine.
The adult dosage of dopamine should be administered via IV and the most common infusion rate is between 5 and 20 mcg/kg per minute.
You want to be sure to titrate the dosage and drip rate to the patient's response slowly and carefully.
A Word About the Routes of Access for Drugs
In the last Word, we looked at the priorities of access routes along with some specifics concerning the intravenous route. In this Word section, we'll finish up by looking at both the intraosseous route and the endotracheal route, along with a little information on fluid administration.
Intraosseous (IO) Route
Medications and fluids administered during resuscitation can be safely and effectively delivered via the IO route if IV access is not available. Important points to remember about IO access are:
- IO access can be established in all age groups
- IO access can often be achieved in 30 to 60 seconds
- The IO route of drug administration is preferred over the endotracheal (ET) route and may also be easier to establish in cardiac arrest patients
- Any ACLS medication or fluid that is given via IV can also be administered via IO
IO cannulation provides access to a non-collapsible marrow venous plexus, which serves as a rapid, safe, and reliable route for the administration of medications, crystalloids, colloids, and blood during resuscitation. This technique uses a rigid needle, preferably a specially designed IO or bone marrow needle from an IO access kit.
Endotracheal (ET) Route
Both IV and IO routes of medication administration are preferred over the endotracheal route of administration. When considering the administration of medications via the endotracheal route during CPR, it's important to keep these concepts in mind:
- The optimal dosage of most medications delivered via the endotracheal route is not known
- The normal dosage of medications administered via the endotracheal route is roughly 2 to 2.5 times the intravenous route
- CPR will need to be interrupted so the medications don't regurgitate up the endotracheal tube
Studies have demonstrated that epinephrine, vasopressin, and lidocaine are absorbed into the circulatory system after administration via the endotracheal route. When administering medications via the endotracheal route, dilute the dose in 5 to 10 ml of normal saline or sterile water, then inject the medications directly into the endotracheal tube.
Fluid Administration
It's important that healthcare providers titrate fluid administration and vasoactive or inotropic agents as needed to properly optimize blood pressure, cardiac output, and systemic perfusion. The optimal post-cardiac arrest blood pressure isn't known. However, a mean arterial pressure of 65 mm Hg or greater is a reasonable goal.
In hypovolemic patients, the ECF volume is typically restored with normal saline or lactated Ringer's solution. Avoid D5W because it will reduce serum sodium too quickly. Serum electrolytes should be appropriately monitored.
D5W refers to 5 percent Dextrose in Water (also known as D5). It's an isotonic carbohydrate solution that contains glucose as the solute. When it's used, the glucose is quickly absorbed by the cells and utilized for energy, leaving only water behind, which is then a hypotonic solution.
