Magnesium Levels and Neurologic Outcomes in Patients Undergoing Therapeutic Hypothermia After Cardiac Arrest

The role of magnesium in cardiac arrest

Cardiac arrest is a leading cause of death globally. Only 25.8% of in-hospital and 33.5% of out-of-hospital individuals who achieve spontaneous circulation following cardiac arrest survive to leave the hospital. Respiratory failure and acute coronary syndrome are the two most common etiologies of cardiac arrest. Effort has been made to improve the outcomes of individuals resuscitated from cardiac arrest. Magnesium is an ion that is critical to the function of all cells and organs. It is often overlooked in everyday clinical practice. At present, there have only been a small number of reviews discussing the role of magnesium in cardiac arrest. In this review, for the first time, we provide a comprehensive overview of magnesium research in cardiac arrest focusing on the effects of magnesium on the occurrence and prognosis of cardiac arrest, as well as in the two main diseases causing cardiac arrest, respiratory failure and acute coronary syndrome. The current findings support the view that magnesium disorder is associated with increased risk of cardiac arrest as well as respiratory failure and acute coronary syndrome.

Electrolyte considerations in targeted temperature management

PURPOSE

Targeted temperature management (TTM), including normothermia and therapeutic hypothermia, is used primarily for comatose patients with return of spontaneous circulation after cardiac arrest or following neurological injury. Despite the potential benefits of TTM, risks associated with physiological alterations, including electrolyte shifts, may require intervention.

SUMMARY

This review describes the normal physiological balance of electrolytes and temperature-related alterations as well as the impact of derangements on patient outcomes, providing general recommendations for repletion and monitoring of key electrolytes, including potassium, phosphate, and magnesium.

CONCLUSION

Frequent monitoring and consideration of patient variables such as renal function and other risk factors for adverse effects are important areas of awareness for clinicians caring for patients undergoing TTM.

Electrolyte profiles with induced hypothermia: A sub study of a clinical trial evaluating the duration of hypothermia after cardiac arrest

Background

Electrolyte disturbances can result from targeted temperature treatment (TTM) in out‐of‐hospital cardiac arrest (OHCA) patients. This study explores electrolyte changes in blood and urine in OHCA patients treated with TTM.

Methods

This is a sub‐study of the TTH48 trial, with the inclusion of 310 unconscious OHCA patients treated with TTM at 33°C for 24 or 48 h. Over a three‐day period, serum concentrations were obtained on sodium potassium, chloride, ionized calcium, magnesium and phosphate, as were results from a 24‐h diuresis and urine electrolyte concentration and excretion. Changes over time were analysed with a mixed‐model multivariate analysis of variance with repeated measurements.

Results

On admission, mean ± SD sodium concentration was 138 ± 3.5 mmol/l, which increased slightly but significantly (p < .05) during the first 24 h. Magnesium concentration stayed within the reference interval. Median ionized calcium concentration increased from 1.11 (IQR 1.1–1.2) mmol/l during the first 24 h (p < .05), whereas median phosphate concentration dropped to 1.02 (IQR 0.8–1.2) mmol/l (p < .05) and stayed low. During rewarming, potassium concentrations increased, and magnesium and ionizes calcium concentration decreased (p < .05). Median 24‐h diuresis results on days one and two were 2198 and 2048 ml respectively, and the electrolyte excretion mostly stayed low in the reference interval.

Conclusions

Electrolytes mostly remained within the reference interval. A temporal change occurred in potassium, magnesium and calcium concentrations with TTM’s different phases. No hypothermia effect on diuresis was detected, and urine excretion of electrolytes mostly stayed low.

The Association of Serum Magnesium Levels and QT Interval with Neurological Outcomes After Targeted Temperature Management

Targeted temperature management (TTM) is associated with corrected QT (QTc) prolongation and decrease in serum magnesium (Mg) levels that may lead to recurrent ventricular arrhythmia and poor neurological outcomes. We aimed to evaluate the association between QTc interval and Mg levels during TTM with neurological outcomes. We reviewed the electrocardiograms of 366 patients who underwent TTM during the induction, maintenance, and rewarming phase after cardiac arrest. We reviewed the association of change in QTc interval, and Mg levels with neurological outcomes. In total, 71.3% of the patients had a significant increase in QTc interval defined as >60 ms or any QTc >500 ms during TTM. Poor neurological outcome was associated with persistent prolongation of QTc after rewarming (507 vs. 483 ms, p = 0.046) and higher Mg levels at presentation (2.08 ± 0.41 mg/dL, p = 0.014). Supplemental Mg did not have any significant change in their QTc. Patients with prolonged QTc during TTM should be promptly evaluated for QTc-prolonging factors given its association with worse neurological outcomes. The inverse correlation between Mg levels and poor neurological outcomes deserves further investigation.

PROLOGUE (PROgnostication using LOGistic regression model for Unselected adult cardiac arrest patients in the Early stages): Development and validation of a scoring system for early prognostication in unselected adult cardiac arrest patients

BACKGROUND

Early prognostication after cardiac arrest would be useful. We aimed to develop a scoring model for early prognostication in unselected adult cardiac arrest patients.

METHODS

We retrospectively analysed data of adult non-traumatic cardiac arrest patients treated at a tertiary hospital between 2014 and 2018. The primary outcome was poor outcome at hospital discharge (cerebral performance category, 3-5). Using multivariable logistic regression analysis, independent predictors were identified among known outcome predictors, that were available at intensive care unit admission, in patients admitted in the first 3 years (derivation set, N = 671), and a scoring system was developed with the variables that were retained in the final model. The scoring model was validated in patients admitted in the last 2 years (validation set, N = 311).

RESULTS

The poor outcome rates at hospital discharge were similar between the derivation (66.0%) and validation sets (64.3%). Age <59 years, witnessed collapse, shockable rhythm, adrenaline dose <2 mg, low-flow duration <18 min, reactive pupillary light reflex, Glasgow Coma Scale motor score ≥2, and levels of creatinine <1.21 mg dl^-1, potassium <4.4 mEq l^-1, phosphate <5.8 mg dl^-1, haemoglobin ≥13.2 g dl^-1, and lactate <8 mmol l^-1 were retained in the final multivariable model and used to develop the scoring system. Our model demonstrated excellent discrimination in the validation set (area under the curve of 0.942, 95% confidence interval 0.917-0.968).

CONCLUSIONS

We developed a scoring model for early prognostication in unselected adult cardiac arrest patients. Further validations in various cohorts are needed.

A nationwide overview of 1-year mortality in cardiac arrest patients admitted to intensive care units in the Netherlands between 2010 and 2016

AIM

Worldwide, cardiac arrest (CA) remains a major cause of death. Most post-CA patients are admitted to the intensive care unit (ICU). The aim of this study is to describe mortality rates and possible changes in mortality rates in patients with CA admitted to the ICU in the Netherlands between 2010 and 2016.

METHODS

In this study, we included all adult CA patients registered in the National Intensive Care Evaluation (NICE) registry who were admitted to ICUs in the Netherlands between 2010 and 2016. The primary outcome was 1-year mortality which was analysed by Cox regression. The secondary outcomes were ICU mortality and hospital mortality. Hospital mortality was analysed by binary logistic regression analysis. Patients were stratified by whether they experienced in-hospital cardiac arrest (IHCA) or out-of-hospital cardiac arrest (OHCA). Finally, the outcome over calendar time was assessed for both groups.

RESULTS

We included 26,056 CA patients: 10,618 (40.8%) IHCA patients and 14,482 (55.6%) OHCA patients. The 1-year mortality rate was 57.5%: 59% for IHCA and 56.4% for OHCA, p < 0.01. This mortality rate remained stable between 2010 and 2016 for IHCA (p = 0.31) and declined for OHCA patients (p = 0.01). The hospital mortality rate was 50.3%: 50.5% for IHCA and 50.2% for OHCA, p = 0.66. This mortality rate remained stable between 2010-2016 for IHCA (p = 0.21) and decreased for OHCA patients (p < 0.01). An additional analysis with calendar year as a continuous variable showed a mortality decline of 1.56% per calendar year for 1-year mortality.

CONCLUSION

This nationwide registry cohort study reported a 57.5% 1-year mortality rate for CA patients admitted to the ICU between 2010 and 2016. We reported a decline in 1-year mortality for OHCA patients in these years.

Mechanisms Associated with the Adverse Vascular Consequences of Rapid Posthypothermic Rewarming and Their Therapeutic Modulation in Rats

We previously demonstrated that rapid posthypothermic rewarming in noninjured animals was capable of damaging cerebral arterioles both at endothelial and smooth muscle levels. Such adverse consequences could be prevented with antioxidants, suggesting the involvement of free radicals. In this study, we further investigate the mechanisms associated with free radicals production by using two radical scavengers, superoxide dismutase (SOD) and catalase. Employing rats, the cerebral vascular response was evaluated at 2, 3, and 4 hours after onset of hypothermia. Before rapid rewarming, SOD treatment, but not catalase, preserved the NO-mediated dilation induced by acetylcholine (ACh). On the contrary, catalase preserved the hypercapnia-induced relaxation of the smooth muscle cells, whereas SOD offered only partial protection. Adding SOD to catalase treatment offered no additional benefit. These results suggest that rapid posthypothermic rewarming impairs ACh- and hypercapnia-induced vasodilation through different subcellular mechanisms. In the case of diminished vascular response to ACh, it appears to act on the endothelial front primarily by superoxide anions, as evidenced by its full preservation after SOD treatment. In terms of impaired dilation to hypercapnia, hydrogen peroxide and/or its derivatives are the likely candidates in targeting the smooth muscle cells. The partial protection of SOD to hypercapnia-induced dilation is believed to be the reduced amount of superoxide that would otherwise spontaneously dismutate to produce hydrogen peroxide. Although SOD exerts some indirect influence on the hydrogen peroxide production downstream, catalase apparently has no influence on upstream superoxide production.