Table 1.

Baseline characteristics in the cohort

	P-Na < 135 mmol/l (n = 60)	P-Na ≥ 135 mmol/l (n = 28)	p value
Severe NEC, n (%)	43 (71.7)	11 (39.3)	0.005
Gestational age at birth (weeks), median (IQR)	25.92 (24.85–28.86)	26.35 (24.86–29.14)	0.37
Birth weight (g), median (IQR)	810 (678–1162)	820 (702–1191)	0.62
Male, n (%)	45 (75)	15 (53.6)	0.05
SGA, n (%)	14 (23.3)	4 (14.3)	0.40
Cesarean section, n (%)	39 (65.0)	18 (64.3)	1.00
Any IVH, n (%)	27 (45.0)	9 (32.1)	0.35
PDA, n (%)	45 (75.0)	22 (78.6)	0.79
RDS, n (%)	47 (78.33)	22 (78.57)	1.00
Post-natal age at NEC onset (days), mean (SD)	15.3 (1.7)	12.0 (2.1)	0.253
Post menstrual age NEC onset (weeks), median (IQR)	28.93 (26.7–31)	28.07 (26.42–32.57)	0.87
Pneumoperitoneum, n (%)	20 (33.3)	10 (35.7)	0.82
Inotropes at NEC onset, n (%)	4 (6.7)	1 (3.6)	1.00
P-Na before NEC onset (mmol/L) median (IQR)	135 (133–138)	139 (137–142)	0.0001
Missing data, n (%)	4 (6.7)	1 (3.5)
P-Na at NEC onset (mmol/L), median (IQR)	129 (127–132)	137.5 (136–141.5)	0.000
Na difference (mmol/L), median (IQR)	5 (3–9.5)	1 (2–3)	0.000
Glucose at NEC onset (mmol/l), median (IQR)	10.6 (7.6–14.5)	9.4 (8.2–17.2)	0.99
Missing data, n (%)	14 (23.3)	13 (46.4)
Lactate at NEC onset (mmol/l), median (IQR)	2.3 (1.4–3.5)	1.6 (1.1–2.5)	0.04
Missing data, n (%)	12 (20)	9 (32.1)
Platelet count at NEC onset (10^9/L), median (IQR)	104.5 (60–195)	111 (64–187)	0.81
Missing data, n (%)	4 (6.7)	2 (7.1)
Creatinine at NEC onset (µmol/L), median (IQR)	64 (39–80)	59.5 (43.5–69.5)	0.66
Missing data, n (%)	4 (6.7)	4 (14.3)
CRP max during NEC episode (mg/L), median (IQR)	115 (53.5–190)	67.5 (31.5–187)	0.44

IQR interquartile range, SGA small for gestational age, IVH intraventricular hemorrhage, PDA patent ductus arteriosus, CRP C-reactive protein, P-Na plasma sodium, (ΔNa) Sodium difference = P-Na before NEC-onset – P-Na at NEC-onset