Objective: To determine the effect of syringe size on safety and reliability of low-flow infusions at rates relevant to hemodynamically unstable infants.
Design: In vitro study using readily available clinical equipment.
Setting: Medical–surgical pediatric intensive care unit of a university-affiliated hospital.
Interventions: Three-, 12-, and 60-mL syringes (Kendall Monoject) with extension tubing were mounted in identical Baxter AS50 infusion pumps. We determined time to alarm after occlusion of the distal tubing. We described and validated a method using capillary tubes to determine startup time to reach steady-state flow and variability of steady-state flow. Data were analyzed using single-factor analysis of variance or linear regression, as appropriate.
Measurements and Main Results: At 5 mL/hr flow, time to alarm occlusion (mean ± sd) was 1:08 ± 0:42, 3:35 ± 0:58, and 27:06 ± 3:26 minutes for 3-, 12-, and 60-mL syringes, respectively (p < .00001). At a lower flow of 0.2 mL/hr, none of the pumps alarmed despite 30 mins of distal occlusion, regardless of syringe size. Validation testing of the capillary tube volumetric method revealed a sd <5% of the average fluid column displacement. Startup time to reach steady-state flow of 0.2 mL/hr for 60-mL syringes was 76 ± 40 mins and significantly exceeded 24 ± 10 mins for 3-mL syringes (p = .041). In one test using a 60-mL syringe, flow remained below 20% of steady state for >3 hrs. Average steady-state flow was similar for the three syringe sizes (p = .2861), but sd of steady-state flow was directly related to syringe size and regressed to a line with r2 = 1.
Conclusions: Syringe size is related to time to reach steady-state flow, time to alarm occlusion, and variability of low-flow infusions.
From the Department of Pediatrics, David Geffen School of Medicine at University of California-Los Angeles, Los Angeles, CA.
This work was carried out at Santa Monica UCLA Medical Center and Orthopaedic Hospital, Los Angeles, CA.
Financial support for this study was obtained from departmental funds.
The authors have not disclosed any potential conflicts of interest.
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