Presented at the Neonatal Society 2006 Spring Meeting.
Thayyil S, Shaik S, Sinha AK, Kempley ST
Neonatal Unit, Royal London Hospital, Whitechapel, London, UK
Background: Early onset hyperkalemia is associated with a high morbidity and mortality in premature infants. It is thought to be due to a transient deficiency in Na/K ATPase (1).
Aim: To determine the incidence, risk factors and predictors of early onset hyperkalemia in extremely premature infants.
Methods: Analysis of plasma potassium levels in the first week of life from 154 consecutive premature infants ≤28 weeks gestation admitted to a single NICU between 2001-04. Infants with renal malformation or renal failure were excluded. Potassium ≥7 mmol/l was taken as hyperkalemia.
Results: 33 (21%) babies had hyperkalemia during the first 4 days of life (Group 1) with mean peak [SD] 7.7 [0.8] mmol/L, between 36-72 hours. 121 babies (Group 2) were normokalemic. Mean [SD] gestation (25.8 [1.6] vs 26 [1.67] wks), birth weight (915g [216] vs 892g [255]), CRIB score (5.5 [4.2] vs 5.2 [4.1]) and antenatal steroid use (67% vs 75%) were similar in the Group 1 & 2. The hyperkalemia group had a significantly higher phosphate, urea, potassium and lower calcium in the first blood sample after birth (Table 1). The phosphate and urea in the hyperkalemia group remained elevated during the first 48 hours (Table 1 & Figure 1). Infants with urea levels of ≥12 mmol/L or phosphate levels of ≥2.4 mmol/L at 24 hours had a significantly higher risk of developing hyperkalemia: Urea – 54% vs 11%, OR 9.3 (95% CI 3.2, 27); phosphate – 56% vs 13%, OR 8.5 (95% CI 3.3, 22). Calcium levels were inversely related to the potassium levels at 24 hours (r = -0.47, p<0.01).
Conclusions: Early onset hyperkalemia is common in the first 4 days of life in extremely premature infants. High phosphate, urea and potassium levels at birth may be used to predict early onset hyperkalemia. Persistently high phosphate & urea levels (without any increase in sodium & creatinine) suggest a transient catabolic state in hyperkalemic babies.
References
1. Stefano JL et al. J Pediatr. 1993;122 (2):276-84.