Effect of unidirectional airflow ventilation on surgical site infection in cardiac surgery: environmental impact as a factor in the choice for turbulent mixed air flow.

BACKGROUND: Surgical site infection (SSI) in the form of postoperative deep sternal wound infection (DSWI) after cardiac surgery is a rare, but potentially fatal, complication. In addressing this, the focus is on preventive measures, as most risk factors for SSI are not controllable. Therefore, operating rooms are equipped with heating, ventilation and air conditioning (HVAC) systems to prevent airborne contamination of the wound, either through turbulent mixed air flow (TMA) or unidirectional air flow (UDAF). AIM: To investigate if the risk for SSI after cardiac surgery was decreased after changing from TMA to UDAF. METHODS: This observational retrospective single-centre cohort study collected data from 1288 patients who underwent open heart surgery over 2 years. During the two study periods, institutional SSI preventive measures remained the same, with the exception of the type of HVAC system that was used. FINDINGS: Using multi-variable logistic regression analysis that considered confounding factors (diabetes, obesity, duration of surgery, and re-operation), the hypothesis that TMA is an independent risk factor for SSI was rejected (odds ratio 0.9, 95% confidence interval 0.4-1.8; P>0.05). It was not possible to demonstrate the preventive effect of UDAF on the incidence of SSI in patients undergoing open heart surgery when compared with TMA. CONCLUSION: Based on these results, the use of UDAF in open heart surgery should be weighed against its low cost-effectiveness and negative environmental impact due to high electricity consumption. Reducing energy overuse by utilizing TMA for cardiac surgery can diminish the carbon footprint of operating rooms, and their contribution to climate-related health hazards.

In vitro measurement of flow rate variability in neonatal IV therapy with and without the use of check valves.

BACKGROUND: In multi-infusion IV therapy, the actual volume delivered to the neonate can vary over time. To reduce flow rate variability, check valves can be used. A check valve allows flow through the valve in only one direction. OBJECTIVE: To evaluate flow rate variability in a low flow dual-infusion setup with and without check valves. METHODS: The effect of changing the height of and adding syringes to the IV-administration set was tested with and without check valves in an in vitro dual-infusion setup with in-line flow meters. The pre-programmed flow rates were 2.5 and 0.1 ml/h. RESULTS: Twenty-four tests of 90 minutes were performed. Time to reach 75% of the pre-programmed 0.1 ml/h flow rate was >20 minutes. The highest total delivered volume during a test was (mean ± SD) 56 ± 8% of the expected delivery for tests without check valves, and diminished to 12 ± 24% of the expected delivery for check valves with a higher opening pressure. CONCLUSIONS: The actual flows and the total delivered volume in low flow dual-infusion setups are less than expected on the pre-programmed flow-rate. These findings emphasize the need for the development of more accurate delivery systems for drugs and fluids in neonatology. Caregivers should be aware of these findings, and optimise the delivery of IV substances by making use of check valves with low opening pressures and by minimising compliance and volume of the IV-administration set. Furthermore, changes in the relative height between pumps and catheter tip should be minimized.