How to calculate and manage constant rate infusions
A constant rate infusion (CRI) is a medication continuously administered to a patient and is used to maintain consistent plasma levels of that medication. CRIs are commonly administered to patients to achieve appropriate levels of pain management, blood pressure management, sedation, anaesthesia, electrolyte supplementation, insulin, and liquid nutrition via a feeding tube. Delivering a CRI will avoid peak and trough levels of pain management and allow titration to suit the individual patient. When using a CRI to manage blood pressure, medication can easily be increased or decreased to obtain optimal effect and discontinued as needed. While CRI management requires 24 hour monitoring and specialised knowledge by the veterinary staff, the ability to maintain medications at therapeutic levels at all times make CRIs worth the time and knowledge. The veterinary nurse needs to not only understand the effects of the drugs being administered, but also how to calculate and create a variety of CRIs. This article will cover different types of CRI calculations and management.
A constant rate infusion (CRI) is prepared to give a patient a continuous dose of drug in intravenous (IV) fluids. This method is advantageous for administering continuous pain management or for drugs with a short half life, as the drug is maintained at effective plasma concentrations for the duration of the CRI (Creedon et al, 2012). CRIs can also be used to deliver liquid nutrition via feeding tubes for those patients unable to tolerate bolus feedings. CRIs can be utilized for many different patient needs such as pain management, blood pressure management, electrolyte supplementation, sedation, anaesthesia, and insulin administration. The drug can be administered without dilution, calculated to be mixed with concurrent IV fluids already being delivered at a pre-set rate, or prepared separate from IV fluids and titrated to different rates depending on patient needs (Silverstein and Hopper, 2009).