What is the Calculation Formula for the Infusion Rate of Intravenous Fluids?

Intravenous infusion is a commonly used clinical procedure that involves the administration of sterile fluids, electrolytes, and medications into the body through a vein. This process can be categorized into peripheral intravenous infusion, central venous infusion, hyperalimentation, and blood transfusion. The speed of intravenous infusion can be controlled, particularly for specific diseases or medications, to ensure optimal therapeutic effects.

One crucial aspect of intravenous infusion is the calculation of the infusion rate. There are two main methods for determining the infusion rate:

(1) Calculating the hourly infusion volume based on the known number of drops per minute. The formula is: Hourly Infusion Volume (ml) = Drops per Minute × 60 (minutes) / Drops per Milliliter (typically 15 drops). For example, if the infusion rate is 54 drops per minute, the hourly infusion volume would be 54 × 60 / 15 = 216 ml.

(2) Calculating the number of drops per minute based on the total infusion volume and the planned duration of infusion. The formula is: Drops per Minute = Total Infusion Volume × Drops per Milliliter (15 drops) / Infusion Time. For instance, if the total daily infusion volume is 2000 ml and it needs to be completed in 10 hours, the infusion rate would be 2000 × 15 / (10 × 60) = 30000 / 600 = 50 drops per minute.

It's important to note that the infusion rate varies depending on the specific medication being administered.

Some medications, such as nitrates (e.g., nitroglycerin and isosorbide mononitrate), require strict control of the infusion rate. Administering these drugs too quickly can result in excessive doses entering the body in a short period of time, leading to adverse effects like hypotension, tachycardia, and flushing.

Similarly, the infusion rate of potassium chloride must be carefully monitored. Rapid infusion can cause significant irritation to the blood vessels, causing discomfort for the patient. Additionally, a rapid increase in blood potassium levels can suppress cardiac activity and, in severe cases, lead to cardiac arrest.

Quinolones, such as levofloxacin, also require controlled infusion rates to prevent vascular irritation, local pain, and the development of phlebitis.

Moreover, oxytocin, used for induction or augmentation of labor, must be administered at a controlled rate. Typically, the initial infusion rate should not exceed 0.001-0.002 units per minute, gradually increasing by 0.001-0.002 units every 15-30 minutes until a desired uterine contraction pattern is achieved. The fastest infusion rate should not exceed 0.02 units per minute, and the usual rate is between 0.002-0.005 units per minute. When controlling postpartum hemorrhage, the intravenous infusion rate should be maintained at 0.02-0.04 units per minute, and the infusion rate can be slightly increased after the placenta is delivered.

Overall, the administration of intravenous infusions requires careful consideration of the specific medication, the patient's condition, and the desired therapeutic outcome. Appropriate infusion rates are essential to ensure safe and effective drug delivery.