Nurse-to-Nurse Familiarity and Mortality in the Critically Ill: A Multicenter Observational Study.

Nurse-to-nurse familiarity at work should strengthen the components of teamwork and enhance its efficiency. However, its impact on patient outcomes in critical care remains poorly investigated. To explore the role of nurse-to-nurse familiarity on inpatient deaths during ICU stay. This was a retrospective observational study in eight adult academic ICUs between January 1, 2011 and December 31, 2016. Nurse-to-nurse familiarity was measured across day and night 12-hour daily shifts as the mean number of previous collaborations between each nursing team member during previous shifts within the given ICU (suboptimal if <50). Primary outcome was a shift with at least one inpatient death, excluding death of patients with a decision to forego life-sustaining therapy. A multiple modified Poisson regression was computed to identify the determinants of mortality per shift, taking into account ICU, patient characteristics, patient-to-nurse and patient-to-assistant nurse ratios, nurse experience length, and workload. A total of 43,479 patients were admitted, of whom 3,311 (8%) died. The adjusted model showed a lower risk of a shift with mortality when nurse-to-nurse familiarity increased in the shift (relative risk, 0.90; 95% confidence interval per 10 shifts, 0.82-0.98;  = 0.012). Low nurse-to-nurse familiarity during the shift combined with suboptimal patient-to-nurse and patient-to-assistant nurse ratios (suboptimal if >2.5 and >4, respectively) were associated with increased risk of shift with mortality (relative risk, 1.84; 95% confidence interval, 1.15-2.96;  < 0.001). Shifts with low nurse-to-nurse familiarity were associated with an increased risk of patient deaths.