Prevalence of low blood vitamin levels in critically ill patients at intensive care unit admission: A cross-sectional study

Background and aims:
Low blood vitamin levels are common in intensive care unit (ICU) patients and may exacerbate clinical outcomes. Inflammatory status associated with critical illness is known to influence circulating concentrations. This study aimed to assess blood vitamin levels at ICU admission and explore the relationship between dietary intake and blood availability. It also examined the interconnection of multiple low blood vitamin levels, inflammatory status (C-reactive protein concentration), physical frailty and ICU characteristics. 

Methods:
A cross-sectional study was conducted in a tertiary teaching hospital ICU. Patient records were collected within 24 h after admission; phase angle and ultrasound measurements of rectus femoris muscle thickness (QMLT) were taken within 72 h. Pre-admission diet was retrospectively captured by structured recall (patient/proxy) with the Dutch Eetmeter. Blood vitamin and CRP levels were analysed according to ESPEN guidelines. Descriptive statistics, bootstrapping and regression analyses looking for association between CRP and vitamin levels were applied. 

Results:
A total of 79 ICU patients (69 years [95 % CI, 67–72]; 75 % men) were included; 67.1 % had two or more vitamins below reference range, predominantly in vitamin D (78.5 %), followed by vitamin A (43.0 %), and vitamin C (40.5 %). Significant differences in hospital length of stay were identified in patients with multiple low levels (10 [95 % CI, 7–14] vs 6 days [95 % CI, 5–9], p = 0.015). Discordance between estimated dietary intake and blood levels were observed, particularly for vitamins B6, B12 and E. Higher CRP was independently associated with lower vitamin C, A and B9, and higher vitamin B12 blood sample concentration. 

Conclusions:
Low blood vitamin levels and low dietary vitamin intake were common at ICU admission. Inflammation significantly affected circulating concentrations. Discordance between estimated intake and blood levels were frequent. Patients with multiple low blood vitamin levels had longer hospital trajectories. This study emphasizes the need for individual nutritional care in critical illness.