After CPR and defibrillation are underway, the team should attempt access for medication delivery. Attempts at access should not interfere with the delivery of chest compressions.  

Peripheral Intravenous (IV) Access

When medications for cardiac arrest are given via peripheral IV, they should be followed by a 20 mL bolus of IV fluid infusion. This helps to improve the delivery of the medication to the patient’s central circulation. Also, the extremity should be elevated for 10–20 seconds, which may aid delivery via gravity effects. However, this practice has not been effectively studied. The guidelines specify that IV is the preferred route for medication administration.

Peripheral IV Access

Intraosseous (IO) Access

IO access allows medication administration that is very similar to IV access. The bone marrow is made up of a noncollapsible plexus that provides access to the circulation. IO can be used for medication and fluid administration as well as for obtaining blood for laboratory evaluation. The skilled provider can obtain IO access efficiently in all age groups. Commercially manufactured kits for obtaining IO access are available.

Generally, IO access is considered an alternative to IV access. However, though all medication can be given via IO, not all medications have been studied using IO access. 

Central Intravenous (IV) Access

Central lines can also be established for medication delivery. This access should be obtained by well-trained responders and can access the internal jugular or the subclavian veins. This allows faster access to the central circulation, and access to the superior vena cava allows direct monitoring of central venous saturation of oxygen (ScvO₂) as well as CPP, which evaluates the effectiveness of resuscitation. 

However, central line placement is a process that can significantly interrupt chest compressions and does limit the ability to use fibrinolytic medications if needed. Additionally, there is an associated increased risk for infections and other adverse effects compared to peripheral access.

Endotracheal Access

Several medications used for cardiac arrest, including epinephrine, lidocaine, and naloxone, are absorbed in the trachea. However, this route of administration results in lower concentrations in the blood when compared to vascular access. Not only can this limit effectiveness, but in the case of epinephrine, it can lead to adverse effects as lower concentration may lead to more beta-adrenergic effects such as vasodilation, which can be very harmful during cardiac arrest. 

As a result, IV and IO access are always preferred for medication administration, and endotracheal delivery should only be used when vascular access is not available. Of note, endotracheal medication dosing is not the same as IV and IO dosing and can be extremely variable. Generally, the recommendation is to give 2–2.5 times as much as the typical IV dose. The medication should be diluted in 5–10 mL of fluid and injected into the endotracheal tube. The use of sterile water for dilution may improve medication absorption when compared to normal saline.