Comparative flow rates of thin-walled and conventional-walled intravenous catheters.

The rapid administration of intravenous fluids is often a major consideration during the course of an anesthetic. This in vitro study was undertaken to compare fluid flow rates through 18- and 20-gauge intravenous catheters in both thin-wall and conventional-wall designs. All brands and types of catheters of similar sizes have the same outer diameter; however, the inner diameter may vary according to individual design. Comparison of the thin-wall and conventional-wall catheters reveals a larger inner lumen in the thin-wall catheter, because of its thinner wall construction. Six 18-gauge, 1 1/4-inch catheters and three 20-gauge, 1 1/4-inch catheters were studied by measuring the average flow rate of 100-mL of water through each catheter. Four of the 18-gauge catheters and two of the 20-gauge catheters were of the thin-wall design. Results showed that the flow rates through the thin-wall catheters were greater than (P less than .05) those found with the conventional-wall catheters in both the 18- and 20-gauge catheters. However, the clinical significance of these differences is debatable.