Introduction
Commercial off-the-shelf (COTS) intravenous fluid (IVF) containers contain residual air, introducing the risk of venous air embolism (VAE). Venous air embolism occurs when air displaces blood flow in vasculature. The danger from residual air is often negligible in terrestrial settings, where gravitational forces generate buoyancy, pushing residual air to the top of the IVF container. However, in microgravity there is no buoyancy to separate liquid and gas layers. We performed experiments to quantify the amount of air in COTS IVF containers (Experiment 1) and identify the variables that affect the stability of sterilely produced airless containers (Experiment 2).
Materials and Methods
Experiment 1: Residual air was quantified across varying volumes (100, 250, 500, and 1,000 mL), container design, and manufacturer (B. Braun, Baxter, ICU Medical, and Grifols) of 0.9% NaCl COTS IVFs. Each container was assessed for absolute volumes of air, as well as air:fluid ratios normalized to 1,000 mL. Experiment 2: 1,000 mL IVF containers from 3 manufacturers were filled with either (1) 100% saline or (2) 95% saline and 5% air by volume. Containers were stored for 168 days at 25°C or 40 °C. The containers were optically imaged to quantify the accumulation of air within each IVF container.
Results
Experiment 1: There was a trend toward larger container sizes and greater absolute volumes of residual air (R2 = 0.964). However, the smallest air:volume ratio occurred in the Baxter 500 mL VIAFLO Container (18.9 ± 3.8 mL air; 2.3% air by volume), whereas the largest ratio occurred in the B. Braun 250 mL EXCEL Container (55.0 ± 9.3 mL; 22.0% air by volume). Experiment 2: By day 168, 6 experimental containers had ruptured and 100% of the surviving containers (30/36) had an increase in air as compared to baseline. Containers placed at 40 °C had a larger increase in air (27.7 ± 6.6 mL) compared to containers stored at 25 °C (7.5 ± 4.1 mL; P < .0001).
Conclusions
Residual air has a wide variety of volumes in COTS IVFs. The average amount of residual air is high enough to contribute to clinically significant VAEs, although unlikely to be fatal. If airless IVF containers are produced for exploration missions, a progressive increase in the amount of residual air should be expected. Extremes of temperatures and humidity will increase the reaccumulation of residual air and decrease the shelf-life of airless IVFs.
