Clinical PotpourriHypophosphatemia on the intensive care unit: Individualized phosphate replacement based on serum levels and distribution volume☆,☆☆,★
Introduction
Hypophosphatemia, defined as a serum phosphate level < 0.6 mmol/L, is a frequent finding in intensive care unit (ICU) patients. It may be caused by redistribution, gastro-intestinal loss, or renal phosphate loss. The reported prevalence of ICU hypophosphatemia ranges from 10–80%, with a mean of about 25% [1]. Severe hypophosphatemia, defined as a level < 0.3 mmol/L, can lead to respiratory insufficiency, heart failure, arythmias, rhabdomyolysis, neuropathy, and thrombocytopenia [2], [3]. The clinical significance of moderate hypophosphatemia (serum phosphate 0.3-0.6 mmol/L) is currently not exactly known. However, it is common practice to correct phosphate levels < 0.6 mmol/L in patients on the ICU because there is evidence to suggest that moderate hypophosphatemia may impair diaphragmatic contractility, reduce left ventricular stroke work and can lead to insulin resistance [4], [5], [6], [7].
Several phosphate replacement schedules have been proposed [1], [2], [8], [9], [10], [11], [12]. Most are based on the use of fixed doses without adjustment for the degree of hypophosphatemia or body weight, and most studies included only small numbers of patients. To date, no uniform policy or protocol has emerged from these data. There is no international guideline for phosphate replacement on the ICU, and thus, much variability exists between countries and individual hospitals. Based on a pilot-study in 7 subjects, French et al have proposed a protocol with individualized dose-calculation derived from the actual serum phosphate level and an apparent phosphate distribution volume [13]. This approach is attractive because physiologically it is the most rational approach of all previously proposed regimens. We therefore decided to implement this protocol as standard practice in our ICU, to assess its effects on serum phosphate levels, and to evaluate its safety. The present report describes the results of this analysis.
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Patients and methods
This study was performed in a 15 bed ICU of a large teaching hospital in the Netherlands. The ICU population mainly consisted of general medical and surgical patients. It did not include post-CABG (coronary artery bypass graft) or severe trauma patients. All patients admitted to this ICU are routinely screened for hypophosphatemia on day 1, 3, 5, and 7. The present study includes the first 50 patients who were found to have a serum phosphate level < 0.60 mmol/L during their stay. Exclusion
Results
Baseline characteristics such as age, gender, weight, APACHE score, and ICU admission diagnosis are summarized in Table 1.
Pre-infusion phosphate levels ranged from 0.18–0.58 mmol/L, with a mean of 0.46 ± 0.01 mmol/L. Two out of 50 patients had a serum P < .30 mmol/L. The mean phosphate replacement dose was 28 ± 1 mmol (range, 16-52 mmol). This was associated with a mean potassium infusion of 23 ± 1 mmol (range, 13–46 mmol). The mean infusion time was 2 hours and 45 minutes (range, 1.5-5.5
Discussion
This study demonstrates the effect and safety of a calculated phosphate loading dose based on a distribution volume of 0.50 L/kg body weight and a target serum phosphate of 1.25 mmol/L. Ninety-eight percent of the patients achieved a serum phosphate ≥ 0.6 mmol/L, and none of the patients developed clinically relevant hyperphosphatemia or hyperkalemia. In addition, the Ca × P product never exceeded the upper normal limit, and serum calcium did not change significantly. Thus, intravascular or
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Cited by (27)
Prescription of phosphorus, calcium and magnesium: Choice of the millimole unit to establish the equivalence of doses between oral and injectable forms
2022, Annales Pharmaceutiques FrancaisesHyperphosphatemia rather than hypophosphatemia indicates a poor prognosis in patients with sepsis
2021, Clinical BiochemistryCitation Excerpt :Third, patients with hyperphosphatemia have a higher risk of developing serious complications such as cardiovascular disease [28], acute kidney injury (AKI), and end-stage renal disease [8]. Several previous studies showed that critically ill patients with hypophosphatemia had a higher death risk compared with patients with normophosphatemia [15,18,29]. The study conducted by Shor et al. included 55 patients with sepsis who were divided into severe (serum phosphorus < 1.0 mg/dL) and non-severe (serum phosphorus > 1.0 mg/dL) hypophosphatemia groups based on serum phosphorus levels, and showed that the risk of death in the severe hypophosphatemia group was increased by nearly eight times [15].
Multicommutated flow analysis system based on fluorescence microdetectors for simultaneous determination of phosphate and calcium ions in human serum
2015, TalantaCitation Excerpt :Each 0.323 mmol L–1 increase phosphate in serum level was associated with about 23% increase in risk of death [6]. Lower than physiological levels of serum phosphate ions could cause arrhythmia, respiratory distress what is especially dangerous for patients at intensive care units [7]. Severe hypophosphatemia could serve as a strong mortality predictor in sepsis [8].
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Conception and design: AB, MB, DT, MR, HdB.
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Analysis and interpretation: AB, MR, MB, CM, HdB.
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Important intellectual content: AB, MB, HdB.