Magnesium status and magnesium therapy in critically ill patients: A systematic review

The Stability of Analytes of Ionized Magnesium Concentration and Its Reference Range in Healthy Volunteers

This study aimed to determine the stability of refrigerated analytes of iMg concentration at different time intervals and to establish iMg reference range in a cohort of healthy Omani volunteers (≥18 years). The concentrations of iMg were measured using the direct ion-selective electrode technique. Pearson's and Lin's concordance correlation coefficients along with the Bland-Altman plot were used to assess the levels of agreement between iMg concentrations of fresh and refrigerated blood samples at different time intervals. The study included 167 volunteers (51% females) with a median age of 21 (range: 20-25) years. The median, 2.5th, and 97.5th percentiles for fresh iMg reference ranges were 0.55, 0.47, and 0.68 mmol/L, respectively. The overall agreement between the fresh and refrigerated iMg concentrations was poor (rho-c = 0.51; p < 0.001). However, according to Altman's definition, iMg concentrations of the refrigerated samples for a period of ≤1 h had an excellent correlation with the fresh iMg concentrations (Lin's rho-c = 0.80), with a small average bias difference of 0.009 (95%CI; -0.025-0.043). A cut-off refrigeration period within ≤1 h at 2-8 °C can be considered an alternate time frame for the gold standard measurement (fresh or within 0.5 h).

Massive Transfusion Increases Serum Magnesium Concentration

(1) Background: The massive transfusion of packed red blood cells (RBCs) is a lifesaving procedure, but it is associated with complications, e.g., dysmagnesemia. Since magnesium is an intracellular ion, the transfused RBCs can significantly influence the magnesium concentration in the recipient's blood. (2) Methods: A retrospective study was performed among 49 patients hospitalized in the Central Clinical Hospital of the Medical University of Warsaw who received a massive blood transfusion (≥4 units/h). Data on laboratory results and patient history were collected from the hospital database. The intracellular RBCs magnesium concentration was measured in 231 samples using the colorimetric method. (3) Results: There were statistically significant changes in the mean serum magnesium concentration preoperatively and 24 h postoperatively (0.87 ± 0.13 vs. 1.03 ± 0.14, p < 0.00001) and 48 h postoperatively (0.87 ± 0.13 vs. 1.06 ± 0.15, p < 0.00001). Patients who died had significantly higher serum magnesium concentrations (p < 0.05). The median intracellular magnesium concentration in RBCs was 0.91 (0.55-1.8) mmol/L, which is below the reference values of 1.65-2.65 mmol/L. (4) Conclusions: Transfused RBCs significantly increased the serum magnesium concentration 24 h and 48 h postoperatively. It could be a result of mild hemolysis, as the median intracellular magnesium concentration in RBCs was below the reference values.

Effects of magnesium, phosphate, or zinc supplementation in intensive care unit patients-A systematic review and meta-analysis

BACKGROUND

Low-serum levels of magnesium, phosphate, and zinc are observed in many intensive care unit (ICU) patients, but clinical equipoise exists regarding supplementation strategies. We aimed to assess the desirable and undesirable effects of supplementation with magnesium, phosphate, or zinc in adult ICU patients.

METHODS

We conducted a systematic review with meta-analysis of randomised clinical trials assessing the effects of supplementation with magnesium, phosphate, or zinc in adult ICU patients. Primary outcomes were mortality and duration of mechanical ventilation. We registered the protocol, followed the Preferred Reporting Items for Systematic Review and Meta-Analysis statement, used the Cochrane risk of bias 2 tool, and the grading of recommendations, assessment, development and evaluation (GRADE) approach for assessing the certainty of the evidence.

RESULTS

We identified no low risk of bias trials. For magnesium supplementation, we included three trials (n = 235); the relative risk (RR) for mortality was 0.54, 95% confidence interval (CI) 0.30-0.96 compared to no supplementation (very low certainty of evidence). For zinc supplementation, two trials were included (n = 168); the RR for mortality was 0.73, 95% CI 0.41-1.28 compared to control. No trials assessed the effects of phosphate supplementation on mortality. For outcomes other than mortality, only zero or one trial was available.

CONCLUSIONS

In adult ICU patients, the certainty of evidence for the effects of supplementation with magnesium, phosphate, or zinc was very low. High-quality trials are needed to assess the value of supplementation strategies in these patients.

Association of Serum Magnesium and Risk of Morbidity and Mortality in ICU-Admitted Patients Based on COVID-19 Infection Classification

Background: Magnesium (Mg) deficiency is a common clinical electrolyte abnormality in critically ill patients, which is related to higher mortality and is easily ignored. Objectives: We aimed to investigate the association of Mg levels with mortality and comorbidity in patients admitted to the intensive care unit (ICU) based on COVID-19 infection classification. Methods: A total of 69 patients admitted to the ICU of Shahid Mohammadi Hospital, Bandar Abbas, Iran, from June to December 2021were included in the present study. The serum Mg was measured in these patients. Data from sequential organ failure assessment (SOFA), acute physiologic assessment and chronic health evaluation (APACHE), ICU stay length, mechanical ventilation duration, mortality, and comorbidity were determined. Moreover, the COVID-19 infection was detected by PCR. Results: The mean ± SD age of patients (34.8% male) was 52.56 ± 16.43 years. Out of 69 patients, 18 (26.1%) died during hospitalization, and 24 (34.8%) required mechanical ventilation. The prevalence of COVID-19 was 39.1% (27 patients). Our results showed no difference in serum Mg between patients based on mortality and comorbidity status. However, the Mg level of patients with kidney failure was significantly higher than patients without kidney failure (P < 0.05). Based on the COVID-19 classification, there was only a positive correlation between hypomagnesemia and the length of ICU hospitalization in patients without COVID-19 (P < 0.05). Conclusions: Our findings showed no difference in the Mg levels of patients based on mortality status. Patients with kidney failure had higher serum Mg than those without kidney failure. Furthermore, our results showed no difference in the Mg levels of critically ill patients based on COVID-19 infection status.

The effects of hypomagnesemia on delirium in middle-aged and older adult patients admitted to medical intensive care units

Background

In critically ill patients, the most common manifestation of brain dysfunction is delirium, which is independently associated with higher morbidity and mortality. While electrolyte imbalance is one of the precipitating factors, the impact of hypomagnesemia on the incidence of delirium remains unknown.

Methods

We retrospectively analyzed patients admitted to the medical intensive care unit (ICU) of a tertiary referral center between January and June 2020. Patients with ICU stay ≥48 hours and aged 40–85 years were included. The primary outcome was cumulative incidence of delirium in the ICU. Patients were divided into two groups based on serum magnesium level at ICU admission. Multivariable Cox proportional hazards regression analysis was performed, and covariates were selected using the least absolute shrinkage and selection operator (LASSO) method.

Results

A total of 109 patients included 43 (39.4%) women and had a median age of 69.0 years (interquartile range [IQR], 60.0–76.0 years). The median magnesium level was 1.7 mg/dl (IQR, 1.5–1.9 mg/dl), and the cumulative incidence of delirium was 32.1% (35 patients). Hypomagnesemia was independently associated with delirium (adjusted hazard ratio [aHR], 2.12; 95% confidence interval [CI], 1.03–4.38), along with prior use of immunosuppressants (aHR, 3.08; 95% CI, 1.46–6.48) or benzodiazepines (aHR, 4.02; 95% CI, 1.54–10.50), body mass index (aHR, 0.93; 95% CI, 0.84–1.02), and alcohol history (aHR, 1.68; 95% CI, 0.74–3.80).

Conclusions

In critically ill adults, hypomagnesemia increases the risk of delirium by more than two-fold compared to patients with normal magnesium level.

A pilot study of the pharmacokinetics of continuous magnesium infusion in critically ill patients

Objective: The pharmacokinetics and haemodynamic effect of continuous magnesium infusion in non-cardiac intensive care unit (ICU) patients are poorly understood. We aimed to measure serum and urine magnesium levels during bolus and continuous infusion in critically ill adults, compare serum levels with those of a control population, and assess its haemodynamic effect. Design: Pharmacokinetic study Setting: A single tertiary adult ICU. Participants: Mechanically ventilated adults requiring vasopressor support. Intervention: A 10 mmol bolus of magnesium sulfate followed by 1.5-3 mmol/h infusion for 24 hours. Main outcome measures: The primary outcome was the change in total serum magnesium concentration. The main secondary outcome was mean arterial pressure (MAP)- adjusted vasopressor dose. Results: We matched 31 treated patients with 93 controls. Serum total magnesium concentration increased from a median 0.94 mmol/L (interquartile range [IQR], 0.83-1.10 mmol/L) to 1.38 mmol/L (IQR, 1.25-1.69 mmol/L; P < 0.001) and stabilised between a median 1.64 mmol/L (IQR, 1.38-1.88 mmol/L) at 7 hours and 1.77 mmol/L (IQR, 1.53-1.85 mmol/L) at 25 hours. This was significantly greater than in the control group (P < 0.001). The MAP-adjusted vasopressor dose decreased during magnesium infusion (P < 0.001). Conclusion: In critically ill patients, a magnesium sulfate bolus followed by continuous infusion achieved moderately elevated levels of total serum magnesium with a decrease in MAP-adjusted vasopressor dose. Trial registration number: ACTRN12619000925145.

Associations between the serum magnesium and all-cause or cardiovascular mortality in chronic kidney disease and end-stage renal disease patients: A meta-analysis

BACKGROUND

Some studies have found that hypomagnesemia is associated with vascular calcification, atherosclerosis, and cardiovascular disease, which may lead to increased mortality in patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD) who need to maintain hemodialysis (HD). However, the conclusion of these studies remain controversial.

METHODS

Relevant literature was retrieved from the database of Cochrane library, PubMed, EMBASE, and CNKI until December 2020, without any language restrictions. The data was analyzed using the Stata 12.0 software.

RESULTS

A total of 31 studies were included, involving 205436 participants. The results showed that after multivariable adjusted, hypomagnesemia was significant associated with the risk of all-cause mortality in patients with CKD and end-stage renal disease (ESRD) (hazard ratios [HR] 1.955; 95% confidence interval (95% CI) 1.511-2.528; P = .000; hypomagnesemia vs normal magnesium or hypermagnesemia). In contrast, in patients with CKD and ESRD, hypermagnesemia was negatively correlated with all-cause mortality (HR 0.873; 95% CI 0.793-0.960; P = .005) (per unit increase). Moreover, in the adjusted model, it was observed that hypermagnesemia was significantly associated with a reduced risk of cardiovascular death (HR 0.598; 95% CI 0.094-1.102, P = .020). In addition, subgroup analysis found that hypomagnesemia was closely related to the increase of all-cause mortality in HD patients (HR 1.799; 95% CI 1.375-2.354; P = .000) (hypomagnesemia vs normal magnesium or hypermagnesemia).

CONCLUSION

Our results show that hypomagnesemia is significantly associated with cardiovascular and all-cause mortality in maintenance HD patients. Further studies should be conducted to evaluate the benefits of magnesium correction in maintenance dialysis patients with hypomagnesemia.

Notification of biochemistry critical results and its clinical impact on outpatient care: experience in a Spanish tertiary hospital

OBJECTIVES

The communication of critical results (CR) is considered an essential role in clinical laboratories to ensure patient safety. This is especially relevant to outpatients, who are non-hospitalized and more difficult to locate. In our laboratory, there is a specific protocol for CR management that sets up the communication pathway to adequately provide these results to clinicians. The aim of this study is to evaluate the impact of CR reporting on outpatient care.

METHODS

This is a retrospective study focused on CR for biochemistry parameters in a clinical laboratory of a Spanish tertiary hospital during 2019. A total of 156 CR were determined and properly provided to clinicians. We collected CR, age, gender, and the requesting department. We also collected the medical action data resulting from the communication of the CR.

RESULTS

Seventy-six outpatients (49%) were properly treated because of effective CR communication. Hypoglycemia was the most frequent event (33%), however, the greatest clinical impact was observed for patients with hyponatremia (100%), hyperkalemia (62%), hypokalemia (60%), and hypercalcemia (57%). Based on these findings, we evaluated new glucose alert thresholds depending on whether or not the outpatient was diabetic (1.7 and 2.2 mmol/L, respectively). Based on these new thresholds, we established a CR reporting protocol with 69% effectiveness in outpatients.

CONCLUSIONS

We demonstrate that CR communication in outpatients has a significant clinical impact. To increase the effectiveness of the CR reporting protocol, we propose to adjust alert thresholds according to pathology, department, and patient population.

Determinants of serum magnesium abnormalities and outcome among admissions to the intensive care unit

Serum magnesium is a frequently measured and treated electrolyte. However, few studies have examined magnesium level abnormalities and outcome in critically ill patients. Our objective was to determine the epidemiology and outcome of magnesium abnormalities among patients admitted to intensive care units (ICU). A retrospective cohort including adult patients admitted to three ICUs in southeast Queensland was assembled. Magnesium levels < 0.7, 0.7-1.0, and > 1.0 mmol/L were classified as low, normal, and high, respectively. Among 14,101 patients, the median age was 59.3 (interquartile range; IQR, 45.1-70.5), 7493 (56.4%) were male, and the median APACHE III score was 48 (IQR, 34-66). At admission, 3357 (23.8%) patients were classified as having hypomagnesemia, 1682 (11.9%) hypermagnesemia, 165 (1.2%) mixed, and 8897 (63.1%) as normal. Patients with magnesium abnormalities were more likely to be underweight and to have higher APACHE III scores. The overall 30-day case fatality was 8.2% (1155/14,101). Compared to those with normal levels, patients with hypermagnesemia at admission were at two-fold increased crude risk for death (relative risk; RR, 2.09; 95% confidence interval; CI, 1.83-2.39; p < 0.0001). After controlling for confounding variables in logistic regression analysis, neither admission hypo- nor hypermagnesemia was associated with death. However, development of ICU acquired hypermagnesemia among those with normal (odds ratio; OR, 1.34; 95% CI, 1.02-1.77; p = 0.034) and low (OR, 1.67; 95% CI, 1.15-2.41; p = 0.006) admission magnesium levels increased the risk for death. Magnesium abnormalities are common among patients managed in ICUs. The determinants of ICU-acquired hypermagnesemia and its adverse effect on outcome warrants further investigation.

Effects of magnesium, phosphate and zinc supplementation in ICU patients-Protocol for a systematic review

BACKGROUND

Depletion of the trace elements magnesium, phosphate and zinc is common in patients admitted to the intensive care unit (ICU). Observational studies have suggested worse outcome in patients with hypomagnesaemia, hypophosphataemia or hypozincaemia, but also inverse associations with worse outcome with too high serum levels. However, it is unclear whether data from randomised clinical trials (RCTs) confirm this. Accordingly, we plan to assess the balance between benefits and harms of supplementation as compared with placebo or no supplementation in adult ICU patients.

METHODS

We will conduct a systematic review of RCTs with meta-analysis and trial sequential analysis in accordance with the Cochrane Handbook for Systematic Reviews of Interventions, the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statement and the Grading of Recommendation, Assessment, Development and Evaluation (GRADE) approach. We will assess the effects of any supplementation with magnesium, phosphate or zinc vs. placebo or no treatment in adult ICU patients. We will systematically search the Cochrane CENTRAL, Embase, PubMed, and for unpublished trials: ClinicalTrials.gov, the EU clinical Trials Register and the WHO International Clinical Trials Registry Platform. The primary outcomes will be days alive without mechanical ventilation and overall mortality. Secondary outcomes include use for mechanical ventilation, tachy-arrhythmias, use of vasopressors, length of hospital stay and use of renal replacement therapy.

DISCUSSION

The benefits and harms of supplementation therapy with magnesium, phosphate and zinc in general ICU patients are unknown. This outlined systematic review will provide data on the evidence, on which future recommendations for supplementation may be founded.

Hypomagnesemia and Short-Term Mortality in Elderly Maintenance Hemodialysis Patients

Background

The relationship between magnesium and mortality in hemodialysis patients has been evaluated in several prospective studies, but few have assessed the risk of all-cause mortality in elderly hemodialysis patients. The aim of this study was to evaluate the association between magnesium levels and the risk of cardiovascular and overall mortality in elderly maintenance hemodialysis patients.

Methods

This was a retrospective study, and patients undergoing maintenance hemodialysis were screened for eligibility at a single dialysis center between July and December 2016. Patients were divided into two groups based on their magnesium levels: a low magnesium level group and a high magnesium level group. Associations between magnesium level and risk of cardiovascular and all-cause mortality were analyzed with a Cox proportional hazards regression model.

Results

In total, 413 patients were included with a median follow-up period of 12 months. We found that compared to patients with high magnesium levels, those with low magnesium levels had significantly lower levels of hemoglobin, urea, creatinine, uric acid, phosphate, potassium, chloride, albumin, and spKt/V (p < 0.05 for each parameter). There was a strong correlation between the baseline mean serum magnesium concentration 1 year prior and the concentration 1 year later (r² = 0.519, p < 0.001). After adjustment for confounding factors, multivariate Cox proportional hazards analysis showed hypomagnesemia to be an independent predictor of all-cause and cardiovascular mortality in chronic hemodialysis patients. Furthermore, subgroup analysis was performed, revealing that serum magnesium levels were still strongly associated with all-cause mortality and cardiovascular mortality in patients older than 60 years, with HR values of 0.020 (95% CI 0.001-0.415) and 0.010 (95% CI 0.000-0.491), respectively. In addition, there were still significant associations between the serum magnesium level and all-cause mortality and cardiovascular mortality in elderly dialysis patients at the 6-month follow-up visit.

Conclusion

Our study indicates that lower serum magnesium levels are strongly associated with cardiovascular and all-cause mortality in maintenance hemodialysis patients, especially in the short term and in those who are elderly. Factors affecting serum magnesium concentrations in hemodialysis patients should be investigated, and correcting hypomagnesemia may benefit elderly hemodialysis patients.

Effect of magnesium supplementation on lactate clearance in critically ill patients with severe sepsis: a randomized clinical trial

OBJECTIVES

In this study, changes in lactate clearance following magnesium supplementation were evaluated in critically ill patients with severe sepsis.

METHODS

Fifty-eight patients with severe sepsis were randomly assigned to receive either magnesium (n = 30) or placebo (n = 28). Patients in the magnesium group received intravenous magnesium sulfate to maintain serum magnesium level around 3 mg/dL for 3 days. The placebo group received the same volume of normal saline. Change in lactate clearance was considered primary outcome of the study.

RESULTS

Mean increase in the lactate clearance in the magnesium group was significantly higher than the placebo group on day 2 (27.53% vs. 23.79% respectively, p < 0.001) and day 3 (49.83% vs. 37.02% respectively, p < 0.001). Time to lactate clearance was also significantly shorter in the magnesium group than the placebo group (47.28 ± 20.59 vs. 61.20 ± 24.31 h respectively, p = 0.03). Sepsis-related mortality was not significantly different but median length of ICU stay was significantly shorter in the magnesium group than the placebo group (8 vs. 15 days respectively, p < 0.01).

CONCLUSIONS

Magnesium supplementation increased lactate clearance in critically ill patients with severe sepsis. Optimizing serum magnesium level near the upper limit of the normal range may improve severe sepsis outcomes.

Serum magnesium, mortality, and cardiovascular disease in chronic kidney disease and end-stage renal disease patients: a systematic review and meta-analysis

BACKGROUND

Previous studies reported that magnesium deficiency was associated with vascular calcifications, atherosclerosis and cardiovascular disease, which might play an independent pathogenic role in chronic kidney disease (CKD) and end-stage renal disease (ESRD) patients. However, the results of these studies were somewhat underpowered and inconclusive.

METHODS

Literature was identified by searching PubMed, EMBASE, Web of Science and the Cochrane Central Register of Controlled Trials (CENTRAL). We included studies that investigated the association between serum magnesium with mortality risk in CKD and ESRD patients. Unadjusted and adjusted hazard ratios (HRs) with 95% confidence intervals (95% CIs) were pooled.

RESULTS

Twenty studies involving 200,934 participants were included, and the results showed that there was a strong association between hypomagnesemia and the risk of all-cause mortality in patients with CKD and ESRD (HR 1.32; 95% CI 1.19-1.47; p < 0.00001) (hypomagnesemia vs. normal magnesium or hypermagnesemia) after multivariable adjusted. On the contrary, hypermagnesemia was inversely associated with all-cause mortality in patients with CKD and ESRD (HR 0.86; 95% CI 0.79-0.94; p = 0.001) (per unit increase). Moreover, a significant association between hypermagnesemia and decreased risk of cardiovascular mortality was observed (HR 0.71; 95% CI 053-0.97, p = 0.03) in the adjusted model. In addition, subgroup analysis found that hypomagnesemia was strongly associated with increased all-cause mortality in hemodialysis patients (HR 1.29; 95% CI 1.12-1.50; p = 0.0005) (hypomagnesemia vs. normal magnesium or hypermagnesemia).

CONCLUSIONS

Our results indicate that hypomagnesemia is significantly associated with cardiovascular and all-cause mortality in patients with CKD and ESRD. Further studies evaluating benefits of magnesium correction in CKD and dialysis patients with hypomagnesemia should be performed.

Early Initiation of Post-Pyloric Feeding in Patients with Major Burns: Experience in Taiwan Formosa Water Park Dust Explosion Disaster

Early initiation of enteral nutrition improves clinical outcomes in critical patients with serious burns. Post-pyloric tube feeding is a valuable therapeutic option for severely burned patients with poor gastric emptying. How early post-pyloric feeding can be initiated to provide more benefits to patients has not yet been examined. A fire erupted at a recreational water park in New Taipei City, Taiwan, on June 27, 2015. The results of early initiation versus delayed post-pyloric feeding in severely burned patients in this mass-casualty incident were compared. Door-to-post-pyloric feeding time ≤ 24 h was considered as early post-pyloric feeding (EPF) and that > 24 h was considered as delayed post-pyloric feeding (DPF). Thirteen patients with severe burn injuries (> 40% of the total body surface area) were assigned to undergo either EPF (five patients) or DPF (eight patients). This study is a "fortuitously controlled" study, and the authors were able to formulate and test whether EPF is better than DPF by comparing the two groups. In patients in the EPF, the intake of calories increased rapidly and was maintained throughout the study period. In addition, rapid restoration of plasma magnesium concentrations as well as pronounced recovery of platelet count in the EPF group was observed. In conclusion, our findings indicate that the time from injury to the onset of post-pyloric feeding is crucial, and EPF allows for the administration of calculated caloric needs. Therefore, EPF can be successfully initiated with beneficial outcomes of nutritional reconstruction in severely burned patients.

Challenges in the Diagnosis of Magnesium Status

Magnesium is a critical mineral in the human body and is involved in ~80% of known metabolic functions. It is currently estimated that 60% of adults do not achieve the average dietary intake (ADI) and 45% of Americans are magnesium deficient, a condition associated with disease states like hypertension, diabetes, and neurological disorders, to name a few. Magnesium deficiency can be attributed to common dietary practices, medications, and farming techniques, along with estimates that the mineral content of vegetables has declined by as much as 80⁻90% in the last 100 years. However, despite this mineral's importance, it is poorly understood from several standpoints, not the least of which is its unique mechanism of absorption and sensitive compartmental handling in the body, making the determination of magnesium status difficult. The reliance on several popular sample assays has contributed to a great deal of confusion in the literature. This review will discuss causes of magnesium deficiency, absorption, handling, and compartmentalization in the body, highlighting the challenges this creates in determining magnesium status in both clinical and research settings.

Hypomagnesemia in critically ill patients

BACKGROUND

Magnesium (Mg) is essential for life and plays a crucial role in several biochemical and physiological processes in the human body. Hypomagnesemia is common in all hospitalized patients, especially in critically ill patients with coexisting electrolyte abnormalities. Hypomagnesemia may cause severe and potential fatal complications if not timely diagnosed and properly treated, and associate with increased mortality.

MAIN BODY

Mg deficiency in critically ill patients is mainly caused by gastrointestinal and/or renal disorders and may lead to secondary hypokalemia and hypocalcemia, and severe neuromuscular and cardiovascular clinical manifestations. Because of the physical distribution of Mg, there are no readily or easy methods to assess Mg status. However, serum Mg and the Mg tolerance test are most widely used. There are limited studies to guide intermittent therapy of Mg deficiency in critically ill patients, but some empirical guidelines exist. Further clinical trials and critical evaluation of empiric Mg replacement strategies is needed.

CONCLUSION

Patients at risk of Mg deficiency, with typical biochemical findings or clinical symptoms of hypomagnesemia, should be considered for treatment even with serum Mg within the normal range.

Is refeeding syndrome relevant for critically ill patients?

PURPOSE OF REVIEW

To summarize recent relevant studies regarding refeeding syndrome (RFS) in critically ill patients and provide recommendations for clinical practice.

RECENT FINDINGS

Recent knowledge regarding epidemiology of refeeding syndrome among critically ill patients, how to identify ICU patients at risk, and strategies to reduce the potential negative impact on outcome are discussed.

SUMMARY

RFS is a potentially fatal acute metabolic derangement that ultimately can result in marked morbidity and even mortality. These metabolic derangements in ICU patients differ from otherwise healthy patients with RFS, as there is lack of anabolism. This is because of external stressors inducing a hypercatabolic response among other reasons also reflected by persistent high glucagon despite initiation of feeding. Lack of a proper uniform definition complicates diagnosis and research of RFS. However, refeeding hypophosphatemia is commonly encountered during critical illness. The correlations between risk factors proposed by international guidelines and the occurrence of RFS in ICU patients remains unclear. Therefore, regular phosphate monitoring is recommended. Based on recent trials among critically ill patients, only treatment with supplementation of electrolytes and vitamins seems not sufficient. In addition, caloric restriction for several days and gradual increase of caloric intake over days is recommendable.

Magnesium supplementation: Pharmacokinetics in cardiac surgery patients with normal renal function

BACKGROUND

Intravenous magnesium is routinely administered in intensive care units (ICU) to treat arrhythmias after cardiothoracic surgery. There are no data on the pharmacokinetics of continuous magnesium infusion therapy.

OBJECTIVE

To investigate the pharmacokinetics of continuous magnesium infusion, focusing on serum and urinary magnesium concentration, volume of distribution and half-life.

METHODS

We administered a 10 mmol bolus of magnesium-sulfate followed by a continuous infusion of 3 mmol/h for 12 h in twenty cardiac surgery patients. We obtained blood and urine samples prior to magnesium administration and after one, six, and 12 h.

RESULTS

Median magnesium levels increased from 1.09 (IQR 1.00-1.23) mmol/L to 1.59 (1.45-1.76) mmol/L after 60 min (p < .001), followed by 1.53 (1.48-1.71) and 1.59 (1.48-1.76) mmol/L after 6 and 12 h. Urinary magnesium concentration increased from 9.2 (5.0-13.9) mmol/L to 17 (13.6-21.6) mmol/L after 60 min (p < .001). Cumulative urinary magnesium excretion was 28 mmol (60.9% of the dose given). The volume of distribution was 0.25 (0.22-0.30) L/kg. There were no episodes of severe hypermagnesemia (≥3 mmol/L).

CONCLUSION

Combined bolus and continuous magnesium infusion therapy leads to a significant and stable increase in magnesium serum concentration despite increased renal excretion and redistribution.

Magnesium status and magnesium therapy in cardiac surgery: A systematic review and meta-analysis focusing on arrhythmia prevention

PURPOSE

To investigate magnesium as prophylaxis or treatment of postoperative arrhythmias in cardiac surgery (CS) patients. To assess impact on biochemical and patient-centered outcomes.

MATERIALS AND METHODS

We searched MEDLINE, CENTRAL and EMBASE electronic databases from 1975 to October 2015 using terms related to magnesium and CS. English-Language RCTs were included involving adults undergoing CS with parenterally administered magnesium to treat or prevent arrhythmias, compared to control or standard antiarrythmics. We extracted incidence of postoperative arrhythmias, termination following magnesium administration and secondary outcomes (including mortality, length of stay, hemodynamic parameters, biochemistry).

RESULTS

Thirty-five studies were included, with significant methodological heterogeneity. Atrial fibrillation (AF) was most commonly reported, followed by ventricular, supraventricular and overall arrhythmia frequency. Magnesium appeared to reduce AF (RR 0.69, 95% confidence interval (95%CI) 0.56-0.86, p=0.002), particularly postoperatively (RR 0.51, 95%CI 0.34-0.77, p=0.003) for longer than 24h. Maximal benefit was seen with bolus doses up to 60mmol. Magnesium appeared to reduce ventricular arrhythmias (RR=0.46, 95%CI 0.24-0.89, p=0.004), with a trend to reduced overall arrhythmias (RR=0.80, 95%CI 0.57-1.12, p=0.191). We found no mortality effect or significant increase in adverse events.

CONCLUSIONS

Magnesium administration post-CS appears to reduce AF without significant adverse events. There is limited evidence to support magnesium administration for prevention of other arrhythmias.

The Effects of High Level Magnesium Dialysis/Substitution Fluid on Magnesium Homeostasis under Regional Citrate Anticoagulation in Critically Ill

BACKGROUND

The requirements for magnesium (Mg) supplementation increase under regional citrate anticoagulation (RCA) because citrate acts by chelation of bivalent cations within the blood circuit. The level of magnesium in commercially available fluids for continuous renal replacement therapy (CRRT) may not be sufficient to prevent hypomagnesemia.

METHODS

Patients (n = 45) on CRRT (2,000 ml/h, blood flow (Qb) 100 ml/min) with RCA modality (4% trisodium citrate) using calcium free fluid with 0.75 mmol/l of Mg with additional magnesium substitution were observed after switch to the calcium-free fluid with magnesium concentration of 1.50 mmol/l (n = 42) and no extra magnesium replenishment. All patients had renal indications for CRRT, were treated with the same devices, filters and the same postfilter ionized calcium endpoint (<0.4 mmol/l) of prefilter citrate dosage. Under the high level Mg fluid the Qb, dosages of citrate and CRRT were consequently escalated in 9h steps to test various settings.

RESULTS

Median balance of Mg was -0.91 (-1.18 to -0.53) mmol/h with Mg 0.75 mmol/l and 0.2 (0.06-0.35) mmol/h when fluid with Mg 1.50 mmol/l was used. It was close to zero (0.02 (-0.12-0.18) mmol/h) with higher blood flow and dosage of citrate, increased again to 0.15 (-0.11-0.25) mmol/h with 3,000 ml/h of high magnesium containing fluid (p<0.001). The arterial levels of Mg were mildly increased after the change for high level magnesium containing fluid (p<0.01).

CONCLUSIONS

Compared to ordinary dialysis fluid the mildly hypermagnesemic fluid provided even balances and adequate levels within ordinary configurations of CRRT with RCA and without a need for extra magnesium replenishment.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01361581.

Hypomagnesemia and mortality in patients admitted to intensive care unit: a systematic review and meta-analysis

BACKGROUND

Reports of mortality due to magnesium dysregulation in the critical care setting are controversial. We performed a systematic review and meta-analysis to evaluate the association between hypomagnesemia and mortality in patients admitted to the intensive care unit.

METHODS

Eligible studies assessing the association between hypomagnesemia or hypermagnesemia and mortality in the critical care setting were comprehensively searched in MEDLINE and EMBASE from their inception to September 2015. Inclusion criteria were published observational studies in adults who were admitted to the intensive or critical care setting with initial serum magnesium measurement. We used the definition of abnormal magnesium level defined by each study. Primary outcome was all-cause mortality. We performed meta-analysis using random-effects model and calculated pooled effect estimate of outcome comparing between hypomagnesemia and normal magnesium category.

RESULTS

From 30 full-text articles, 6 studies involving 1550 participants were included in the meta-analysis. There was a statistically significant higher risk of mortality in critically ill patients who had hypomagnesemia with RR of 1.90 (95% CI: 1.48-2.44, P < 0.001, I(2 )=( )63.5%). Risk for needing mechanical ventilation was also higher in the hypomagnesemia group with RR of 1.65 (95% CI: 1.12-2.43, P = 0.01, I(2 )=( )84%). Length of ICU stay was also higher in the hypomagnesemia group with mean difference of 4.1 days (95% CI: 1.16-7.04, P = 0.01).

CONCLUSION

The findings of this meta-analysis indicate hypomagnesemia is associated with higher mortality, the need of mechanical ventilation and also the length of ICU stay in patients admitted to ICU.

Proarrhythmic and Torsadogenic Effects of Potassium Channel Blockers in Patients

The most common arrhythmia requiring drug treatment is atrial fibrillation (AF), which affects 2 to 5 million Americans and continues to be a major cause of morbidity and increased mortality. Despite recent advances in catheter-based and surgical therapies, antiarrhythmic drugs continue to be the mainstay of therapy for most patients with symptomatic AF. However, many antiarrhythmics block the rapid component of the cardiac delayed rectifier potassium current (IKr) as a major mechanism of action, and marked QT prolongation and pause-dependent polymorphic ventricular tachycardia (torsades de pointes) are major class toxicities.