Liu, JiTong

Background: Enteral phosphate replacement offers multiple advantages over intravenous phosphate replacement, but optimal dosing and administration are unclear. Objective: This study aimed to compare 2 different dosing strategies (PRE vs POST) of enteral phosphate replacement for mild hypophosphatemia (serum phosphorus = 2.1-2.5 mg/dL) and to evaluate our dosing strategy for moderate hypophosphatemia (serum phosphorus = 1.5-2 mg/dL) in critically ill patients. Methods: This single-center quasiexperimental, institutional review board–approved study was conducted in adult patients admitted to an intensive care unit (ICU) who received enteral phosphate replacement with a follow-up serum phosphorus level obtained within 24 hours of replacement. Patients were excluded if they had diabetic ketoacidosis, acute kidney injury, or received total parenteral nutrition or targeted temperature management. The mild PRE and POST groups received 48 and 72 mmol of enteral phosphate, respectively. The moderate group received 72 mmol of enteral phosphate. Effectiveness outcomes included normalization of serum phosphorus, defined as 2.6 to 4.5 mg/dL, and median change in phosphorus concentration. Safety outcomes included the incidence of new onset diarrhea and hyperphosphatemia (serum phosphorus >4.5 mg/dL) within 24 hours after phosphate replacement. Results: Of the 138 patients included, the median age was 59 (44-70) years and 69.6% were admitted to the surgical trauma ICU. Normalization of serum phosphorus occurred in 55 (58.2%) patients in mild PRE and 44 (72.7%) patients in mild POST ( P = 0.13). Change in serum phosphorus was 0.4 (0.1-0.9) mg/dL in mild PRE vs 0.7 (0.3-1.2) mg/dL in mild POST ( P = 0.06). Normalization occurred in 39 (66.7%) patients in the moderate group with a change in serum phosphorus of 1.0 (0.6-1.6) mg/dL. Rates of new onset diarrhea and hyperphosphatemia were not significantly different between groups. Conclusion and Relevance: Enteral phosphate replacement appears safe and effective in critically ill patients with mild-to-moderate hypophosphatemia and may serve as an alternative to intravenous phosphate.

ABSTRACT Background Critically ill patients may be overexposed to valproate because altered protein binding leads to a disproportionate free valproate fraction. The Fraser equation was derived and internally validated to estimate critically ill patients' free valproate concentrations, but it requires external validation. Methods Adult intensive care unit (ICU) patients at two academic centers with concurrently measured free and total valproate concentrations were included. Free valproate concentrations were estimated using the Fraser equation which includes total valproate, albumin and BUN concentration, and whether the patient received propofol or aspirin. The primary outcome was Fraser equation performance, assessed using Bland–Altman methods. Comparative performance against estimates from the Doré equation (an alternative predictive equation), therapeutic concordance using a target free valproate range of 5–15 mg/L, and equation improvements were explored. Results Overall, 315 patients and 556 free‐total valproate concentration pairs were included. The mean (±SD) age was 58 (±17) years and 90 (29%) patients were on valproate prior to hospital admission. The Fraser equation estimated free valproate concentrations were correlated with measured concentrations ( r = 0.728) with a negative bias (mean bias −2.77 mg/L, 95% LOA –18.9, 13.4). The Fraser equation increasingly underestimated measured concentrations as measured concentrations increased. 71% of Fraser equation estimates were therapeutically concordant (e.g., estimate and measured both within reference range) compared to 61.9% of Doré estimates ( p = 0.001). Fraser equation modifications led to minor performance improvements but did not overcome worsening underestimation with higher measured free valproate concentrations. Conclusion The Fraser equation was moderately accurate and corresponded with an appropriate interpretation for 71% of free valproate concentrations. Worse underestimation with higher measured free valproate concentrations suggests direct measurement of free valproate concentrations is warranted. While the Fraser equation could complement therapeutic decision making at centers where direct free valproate measurements are unavailable or slow to return, its accuracy is currently insufficient to replace direct measurement.