Hand hygiene compliance, nurse-to-patient ratio have interactive effect in reducing MRSA transmission in the ICU

BOSTON — Reducing the nurse-to-patient ratio to 1:1 yielded the most significant decreases in transmission of methicillin-resistant Staphylococcus aureus, according to results of a computational model presented here at the 50th Interscience Conference on Antimicrobial Agents and Chemotherapy.

“Despite the result that increasing the nurse-to-patient ratio to 1:1 was the best intervention, we saw different trends in MRSA acquisition rates depending on changes in the nurse-to-patient ratio and the hand hygiene compliance rates of nurses,” Sean L. Barnes, a PhD student at the University of Maryland, said during the presentation.

Barnes said the aim of the model was to help determine optimal methods to limit MRSA transmission between patients in the ICU.

“We wanted to determine whether increasing the hand hygiene compliance of nurses would have a greater effect than increasing the nurse-to-patient ratio from 1:4 to 1:1 in various increments,” Barnes said.

The model was based on a 20-bed ICU during a 1-year period. A stochastic, agent-based model was implemented to compare the return on the two strategies.

“For each of these factors, we assigned a baseline or minus level and a plus level that represents the level we would like to achieve at some point in the future,” he said. “We then ran simulations to measure the response, which we chose to be the number of MRSA acquisitions. With these data, we calculated the average number of prevented acquisitions attributable to increasing each factor from its minus to its plus level. We repeated this process over many levels of nurse hand hygiene and nurse-to-patient ratios.

“The results indicated that small changes in hand hygiene compliance do not do as well in preventing the transmission of MRSA as the corresponding changes in nurse-to-patient ratio,” Barnes said. “But if you start out at a higher baseline hand hygiene compliance level and continue to improve, you will do better than most changes in nurse-to-patient ratio.”

For a change of 1:3 to 1:2 in nurse-to-patient ratio, a similar trend held. For a change of 1:4 to 1:2, a larger change in hand hygiene compliance from a higher baseline level was required to prevent more MRSA acquisitions.

“When we finally reduced the nurse-to-patient ratio to 1:1, we saw that this intervention does better than all changes in hand hygiene,” Barnes said. “This is the best scenario, provided it is economically viable.”

Barnes said the two factors have a very strong interaction effect on each other, so it is important to consider the level of each factor when attempting to predict the effectiveness of the other.

“Regarding the method, we found that the simulation technique combined with the factorial design was a good tool,” he said. “It may be useful for examining other interventions in the future.”

For more information:

Barnes SL. K-509. Presented at: 50th Interscience Conference on Antimicrobial Agents and Chemotherapy; Sept. 12-15, 2010; Boston.

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