Incidence and impact of skin mottling over the knee and its duration on outcome in critically ill patients

Purpose Skin mottling is frequent and can be associated with an increased mortality rate in ICU patients with septic shock. Its overall incidence in ICU and its impact on outcome is unknown. We aimed to assess the incidence of skin mottling over the knee among all critically ill patients admitted in ICU and its role on their outcome. Methods An observational study over a 1-year period in a 15-bed medical ICU of a teaching hospital. Skin mottling over the knee was prospectively and qualitatively assessed by trained nurses. Results Incidence of skin mottling was 29% (230 of 791 patients) in overall, and 49% (32 of 65 patients) in the subset of patients admitted for septic shock. Skin mottling was present on the day on admission in 65% of patients and persisted more than 6 h in 59% of cases. In-ICU mortality was 8% in patients without mottling, 30% in patients with short skin mottling and 40% in patients with persistent skin mottling ( p < 0.01 between all groups). In the overall population, skin mottling over the knee was associated with in-ICU mortality independently from SAPS II (aOR 3.29 [95% CI, 2.08–5.19], p < 0.0001). Among patients with skin mottling over the knee, persistence of skin mottling remained associated with increased in-ICU mortality independently of organ dysfunctions at the mottling onset (OR 2.77 [95% CI, 1.34–5.72], p = 0.004). Conclusions Skin mottling is frequent in the general population of patients admitted in ICU. Occurrence and persistence of skin mottling are independently associated with in-ICU mortality.