Hypomagnesemia is common following cardiac surgery

Prevention of Atrial Fibrillation After Cardiac Surgery: A Review of Literature and Comparison of Different Treatment Modalities

Atrial fibrillation is the most common arrhythmia to occur after cardiac surgery, with an incidence of 10% to 50%. It is associated with postoperative complications including increased risk of stroke, prolonged hospital stays and increased costs. Despite new insights into the mechanisms of atrial fibrillation, no specific etiologic factor has been identified as the sole perpetrator of the arrhythmia. Current evidence suggests that the pathophysiology of atrial fibrillation in general, as well as after cardiac surgery, is multifactorial. Studies have also shown that new-onset postoperative atrial fibrillation following cardiac surgery is associated with a higher risk of short-term and long-term mortality. Furthermore, it has been demonstrated that prophylactic medical therapy decreases the incidence of postoperative atrial fibrillation after cardiac surgery. Of note, the incidence of postoperative atrial fibrillation has not changed during the last decades despite the numerous preventive strategies and operative techniques proposed, although the perioperative and postoperative care of cardiac patients as such has improved.

Total serum and ionized magnesium concentrations in healthy and hospitalized dogs

OBJECTIVE

To determine if an association between ionized magnesium (iMg) and total magnesium (tMg) exists in healthy and hospitalized dogs admitted through an emergency service and to assess the associations between iMg and tMg with total protein, albumin, ionized calcium, and total calcium.

DESIGN

Prospective cohort study.

SETTING

Veterinary teaching hospital.

ANIMALS

Sixty-nine dogs were enrolled. The healthy control group (group 1) included 24 dogs, and the hospitalized group (group 2) included 45 dogs.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

For both groups, signalment, a venous blood gas, and serum biochemistry were obtained. In addition, the presumptive diagnosis was recorded for group 2. Blood was obtained prior to any therapeutic interventions. Group 1 tMg was within the reference interval (RI), and the values for iMg were used to provide a healthy group range (HGR) of 0.44-0.50 mmol/L. Group 2 tMg was within the RI, but iMg was below the calculated HGR range (group 2 median iMg = 0.4 mmol/L; range = 0.27-0.70). There was a significant positive correlation between iMg and tMg in each group (group 1: r = 0.6713, P = 0.0003; group 2: r = 0.5312, P = 0.0002). Ionized Mg and tMg were not significantly associated with any of the other evaluated variables in either group.

CONCLUSIONS

Ionized Mg and tMg were significantly associated in both healthy and hospitalized dogs, but the relationship was weaker in the hospitalized dogs compared with the healthy population. For hospitalized dogs, the relationship was weak enough to question the validity of using iMg and tMg interchangeably to track magnesium status.

Role of Magnesium in the Intensive Care Unit and Immunomodulation: A Literature Review

Both the role and the importance of magnesium in clinical practice have grown considerably in recent years. Emerging evidence suggests an association between loss of magnesium homeostasis and increased mortality in the critical care setting. The underlying mechanism is still unclear, but an increasing number of in vivo and in vitro studies on magnesium's immunomodulating capabilities may shed some light on the matter. This review aims to discuss the evidence behind magnesium homeostasis in critically ill patients, and its link with intensive care unit mortality via a likely magnesium-induced dysregulation of the immune response. The underlying pathogenetic mechanisms, and their implications for clinical outcomes, are discussed. The available evidence strongly supports the crucial role of magnesium in immune system regulation and inflammatory response. The loss of magnesium homeostasis has been associated with an elevated risk of bacterial infections, exacerbated sepsis progression, and detrimental effects on the cardiac, respiratory, neurological, and renal systems, ultimately leading to increased mortality. However, magnesium supplementation has been shown to be beneficial in these conditions, highlighting the importance of maintaining adequate magnesium levels in the intensive care setting.

The Role of Hypomagnesemia in Cardiac Arrhythmias: A Clinical Perspective

The importance of magnesium (Mg2+), a micronutrient implicated in maintaining and establishing a normal heart rhythm, is still controversial. It is known that magnesium is the cofactor of 600 and the activator of another 200 enzymatic reactions in the human organism. Hypomagnesemia can be linked to many factors, causing disturbances in energy metabolism, ion channel exchanges, action potential alteration and myocardial cell instability, all mostly leading to ventricular arrhythmia. This review article focuses on identifying evidence-based implications of Mg2+ in cardiac arrhythmias. The main identified benefits of magnesemia correction are linked to controlling ventricular response in atrial fibrillation, decreasing the recurrence of ventricular ectopies and stopping episodes of the particular form of ventricular arrhythmia called torsade de pointes. Magnesium has also been described to have beneficial effects on the incidence of polymorphic ventricular tachycardia and supraventricular tachycardia. The implication of hypomagnesemia in the genesis of atrial fibrillation is well established; however, even if magnesium supplementation for rhythm control, cardioversion facility or cardioversion success/recurrence of AF after cardiac surgery and rate control during AF showed some benefit, it remains controversial. Although small randomised clinical trials showed a reduction in mortality when magnesium was administered to patients with acute myocardial infarction, the large randomised clinical trials failed to show any benefit of the administration of intravenous magnesium over placebo.

Preoperative Oral Magnesium loading to prevent postoperative Atrial Fibrillation following Coronary Surgery (POMAF-CS): A prospective randomized controlled trial

OBJECTIVES

Postoperative atrial fibrillation is common following coronary artery bypass grafting surgery. Hypomagnesemia is frequent after coronary artery bypass grafting surgery. No previous trials have assessed the effect of preoperative magnesium loading on postoperative atrial fibrillation incidence.

METHODS

Design: This was a single-center, double-blind, placebo-controlled, parallel-group trial, with balanced randomization [1:1]. Participants: were recruited from November 2018 until May 2019. Patients received either 3.2 g of magnesium daily (4 tablets of 0.4 g each twice daily) for 72 hours preoperatively and 1.6 g of magnesium (4 tablets) on the day of surgery, or placebo tablets.

RESULTS

The primary outcome was the incidence of postoperative atrial fibrillation. Secondary outcomes included time to extubation, transfusion rate, critical care unit and hospital length of stay. Of the 210 randomized participants, 200 (100 in each group) completed the study. 10 (10%) and 22(22%) subjects developed postoperative atrial fibrillation in the magnesium and placebo groups, respectively (RR = 0.45, 95% CI: 0.23 - 0.91). Hospital and critical care unit length of stay were comparable between the 2 groups. No side effect related to magnesium administration were documented.

CONCLUSION

In this randomized controlled trial, preoperative loading with oral administration of magnesium for 3 days in patients admitted for coronary artery bypass grafting surgery decreases the incidence of postoperative atrial fibrillation compared to placebo (NCT03703349).

CLINICAL TRIAL REGISTRY NUMBER

NCT03703349.

A novel electrocardiographic parameter for the prediction of atrial fibrillation after coronary artery bypass graft surgery "P wave peak time"

OBJECTIVES

Patients with postoperative atrial fibrillation (POAF) have increased risk of both short- and long-term mortality and morbidity; therefore, prediction of POAF is crucial in the preoperative period of the patients undergoing coronary artery bypass graft surgery. Electrocardiography (ECG) is the simplest and cost-effective tool in the preoperative workup of the patients for the prediction of POAF. A newly defined ECG parameter P wave peak time (PWPT) has been shown as a marker of atrial fibrillation development in non-surgical patients and we investigated its role in patients undergoing cardiac surgery.

METHOD

A total of 327 patients undergoing isolated or combined cardiac surgery were involved and the primary endpoint was defined as the development of POAF. The study population was divided into two groups based on the presence or absence of POAF. Groups were compared for both standard P wave parameters and for PWPT on surface ECG. The predictors of POAF were assessed by multivariate regression analysis.

RESULTS

The frequency of POAF was 20.4% (n = 67). P wave peak time in leads D2 (65.1 ± 11.8 vs 57.2 ± 10, p < 0.01) and V1 (57.8 ± 18 vs 44.8 ± 12.3, p < 0.01) were longer in patients with POAF. In multivariate regression analysis, PWPT in leads DII and V1 were independent predictors of POAF (OR: 1.11, 95%CI: 1.02-1.21, p = 0.01, OR: 1.06, 95%CI: 1.00-1.13, p = 0.03 respectively).

CONCLUSION

PWPT in leads DII and V1 can predict the development of POAF in patients undergoing cardiac surgery.

Effects of magnesium on the dose of rocuronium for deep neuromuscular blockade: A randomised controlled trial

BACKGROUND

Magnesium is known to enhance the effect of rocuronium, but the extent is not quantified.

OBJECTIVES

We aimed to quantify the effect of magnesium on the dose of rocuronium for deep neuromuscular blockade.

DESIGN

A randomised controlled study.

SETTING

A single tertiary care hospital.

PATIENTS

Seventy males scheduled to undergo robot-assisted laparoscopic prostatectomy, aged between 20 and 80 years with American Society of Anesthesiologists physical status classification 1 or 2, were enrolled.

INTERVENTIONS

Patients were randomised to either the magnesium group or control group. The magnesium group were infused with 50 mg kg-1 of magnesium, followed by a continuous intra-operative infusion at 15 mg kg-1 h-1 while the control group were infused with the same volumes of 0.9% saline. Deep neuromuscular blockade was maintained with a continuous infusion of rocuronium and was reversed using sugammadex.

MAIN OUTCOME MEASURES

The primary outcome was the dose of rocuronium administered to maintain deep neuromuscular blockade. The secondary outcomes were recovery time, defined as the time from the administration of sugammadex to train-of-four ratio 0.9, and the incidence of postoperative nausea and vomiting.

RESULTS

The dose of rocuronium administered to maintain deep neuromuscular blockade was significantly lower in the magnesium group (7.5 vs. 9.4 μg kg-1 min-1, P = 0.01). There was no difference in recovery time or the incidence of nausea and vomiting.

CONCLUSION

Magnesium reduced the dose of rocuronium required for deep neuromuscular blockade by approximately 20% without affecting the recovery time after administration of sugammadex.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT04013243.

Continuous Magnesium Infusion to Prevent Atrial Fibrillation After Cardiac Surgery: A Sequential Matched Case-Controlled Pilot Study

OBJECTIVE

The authors aimed to test whether a bolus of magnesium followed by continuous intravenous infusion might prevent the development of atrial fibrillation (AF) after cardiac surgery.

DESIGN

Sequential, matched, case-controlled pilot study.

SETTING

Tertiary university hospital.

PARTICIPANTS

Matched cohort of 99 patients before and intervention cohort of 99 consecutive patients after the introduction of a continuous magnesium infusion protocol.

INTERVENTIONS

The magnesium infusion protocol consisted of a 10 mmol loading dose of magnesium sulphate followed by a continuous infusion of 3 mmol/h over a maximum duration of 96 hours or until intensive care unit discharge.

MEASUREMENTS AND MAIN RESULTS

The study groups were balanced except for a lower cardiac index in the intervention cohort. The mean duration of magnesium infusion was 27.93 hours (95% confidence interval [CI]: 24.10-31.76 hours). The intervention group had greater serum peak magnesium levels: 1.72 mmol/L ± 0.34 on day 1, 1.32 ± 0.36 on day 2 versus 1.01 ± 1.14 and 0.97 ± 0.13, respectively, in the control group (p < 0.01). Atrial fibrillation occurred in 25 patients (25.3%) in the intervention group and 40 patients (40.4%) in the control group (odds ratio 0.49, 95% CI, 0.27-0.92; p = 0.023). On a multivariate Cox proportional hazards model, the hazard ratio for the development of AF was significantly less in the intervention group (hazard ratio 0.45, 95% CI, 0.26-0.77; p = 0.004).

CONCLUSION

The magnesium delivery strategy was associated with a decreased incidence of postoperative AF in cardiac surgery patients. These findings provide a rationale and preliminary data for the design of future randomized controlled trials.

New-onset postoperative atrial fibrillation after heart surgery

BACKGROUND

New-onset postoperative atrial fibrillation (poAF) complicates approximately 20-60% of all cardiac surgical procedures and is associated with an increased periprocedural mortality and morbitity, prolonged hospital stay, increased costs, and worse long-term survival. Unfortunately multiple advances in surgery and perioperative care over the last two decades have not led to a reduction in the incidence of poAF or associated complications in the daily clinical practice.

METHODS

A narrative review of the available literature was performed.

RESULTS

An extensive review of the pathophysiology of poAF following cardiac surgery, clinical, and procedural risk-factors is provided, as well as prophylactic measures and treatment.

CONCLUSION

Multiple strategies to prevent and manage poAF following heart surgery already exist. Our hope is that this review will facilitate more rigorous testing of prevention strategies, implementation of prophylaxis regimens as well as optimal treatment of this common and serious complication.

Atrial Fibrillation Post Coronary Artery Graft Surgery: A Review Of Literature

Atrial fibrillation (AF) is a failure that is observed in heart disease and is also known to be the most common heart rhythm disturbance post coronary artery bypass surgery. Although AF is considered a transient problem, it is usually accompanied with a variety of complications and morbidity for patients and may result in death. In the present study, pre- and post-operative considerable factors which may increase the risk and mortality of AF, and possible treatments have been concisely reviewed.

Intraoperative magnesium sulphate decreases agitation and pain in patients undergoing functional endoscopic surgery: A randomised double-blind study

BACKGROUND

Postoperative agitation is harmful for the patient as it may be associated with removal of catheters, nasal packs, oxygen masks and self-injury, and pose a danger to operating theatre staff.

OBJECTIVE

The current study investigated the potential role of magnesium sulphate in treatment of postoperative agitation following functional endoscopic sinus surgery.

DESIGN

A randomised, double-blinded, placebo-controlled trial.

SETTING

ENT operating room, Menofia University Hospitals, Egypt.

PATIENTS

A total of 312 adult patients (171 men and 141 women) were enrolled in the study. Eighteen patients (10 men and eight women) were excluded; data from 294 patients were analysed. Inclusion criteria were age between 20 and 60 years, American Society of Anesthesiologists' physical status 1 or 2 scheduled for functional endoscopic sinus surgery. Exclusion criteria were hypertension, cardiac ischaemia, cerebrovascular insufficiency, neuromuscular diseases, pregnancy, prolonged treatment with calcium-channel blockers, diabetic neuropathy or a known allergy to magnesium compounds.

INTERVENTIONS

Patients were allocated randomly to either the magnesium group (a magnesium infusion of 30 mg kg in the first hour followed by 9 mg kg h until the end of the surgical procedure) or the control group (0.9% saline at the same volume and rate). Hypotensive anaesthesia was induced by nitroglycerine 5 to 20 μg kg min. In the postanaesthetic care unit (PACU), patients were assessed for agitation and pain using the Richmond agitation-sedation scale and numerical rating scale, respectively.

PRIMARY OUTCOME

The incidence and severity of agitation measured 5 min after admission to the PACU.

RESULTS

Magnesium reduced postoperative agitation at time 0 (P = 0.009) and 5, 10, 15 and 30 min after PACU admission (P < 0.0001) as well as total agitation score [3 (0 to 6) versus 9 (0 to 12), P < 0.0001]. Magnesium also reduced pain [4.5 (4 to 5) versus 6 (5 to 6.25), P < 0.0001] and length of PACU stay (88 ± 23 versus 111 ± 31 min, P < 0.0001). The magnesium group consumed less pethidine in PACU compared with the control group (43 ± 15 and 59 ± 19 mg, respectively, P < 0.0001). The intraoperative end-tidal CO2 tension was comparable between groups (4.7 ± 0.7 versus 4.8 ± 1.2 kPa).

CONCLUSION

Intraoperative infusion of magnesium in patients undergoing endoscopic sinus surgery reduced postoperative agitation, pethidine consumption and pain assessed in the PACU. It also decreased the length of stay in PACU compared with the control group.

TRIAL REGISTRATION

The current study was registered according to WHO and ICMJE standards on 7 January 2014, under registration number PACTR 201402000737691.

Serum Magnesium after Kidney Transplantation: A Systematic Review

Magnesium (Mg) status has recently drawn close attention in chronic kidney disease and in kidney transplant recipients. This review aims to evaluate the body of evidence linking hypomagnesemia to clinical consequences in these specific populations. After a brief summary of the main mechanisms involved in Mg regulation and of Mg status in end-stage renal disease, the review focuses on the relationship between hypomagnesemia and cardiovascular risk in kidney transplant recipients. A body of evidence in recent studies points to a negative impact of hypomagnesemia on post-transplant diabetes mellitus (PTDM) and cardiovascular risk, which currently represent the main threat for morbidity and mortality in kidney transplantation. Deleterious biological mechanisms induced by hypomagnesemia are also discussed. While data analysis enables us to conclude that hypomagnesemia is linked to the development of PTDM, studies prospectively evaluating the impact of hypomagnesemia correction after kidney transplantation are still lacking and needed.

Influence of Perioperative Serum Magnesium for Cardiac and Noncardiac Morbidity and Mortality Following Emergency Peripheral Vascular Surgery

OBJECTIVES

To examine the influence of serum magnesium on 30-day mortality and cardiac and noncardiac morbidity.

DESIGN

Retrospective cross-sectional observational study of routinely collected prospective data.

SETTING

Single-center tertiary vascular center in the United Kingdom.

PARTICIPANTS

All patients undergoing arterial peripheral vascular surgery during an unplanned admission.

INTERVENTIONS

Observational, no interventions implemented.

MEASUREMENTS AND MAIN RESULTS

In the study, n = 197. One hundred thirty-eight were male (70.1%). Median age at procedure was 70.0 years (interquartile range 20.0). Of those with a documented history, 37.9% had diabetes, 81.7% had a smoking history, 63.7% had hypertension, and 26.5% had known ischemic heart disease or heart failure. There was a significant perioperative change in magnesium (p < 0.001), calcium (p < 0.001), and creatinine (p = 0.004), with no significant alteration in potassium (p = 0.096). Thirty-day mortality was 4.6%. Thirty-day cardiac morbidity was 4.1%. Thirty-day noncardiac morbidity was 32.3%. Postoperative magnesium was independently predictive for 30-day mortality (p = 0.02, odds ratio [OR] 0.96, 95% confidence interval [CI] 0.94-0.99) and cardiac morbidity (p = 0.03, OR 0.97, 95% CI 0.95-1.00). Only a previous smoking history was independently predictive of noncardiac morbidity (p = 0.03, OR 9.67, 95% CI 1.20-78.15).

CONCLUSION

Perioperative changes in serum magnesium may have an influence on short-term mortality and cardiac complications. This should be considered in the management of patients undergoing unplanned peripheral vascular surgery; however, further research is needed to examine the benefit of supplementation perioperatively and to explore the exact mechanisms.

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.

Rhythm Disturbance After Myocardial Revascularization

Introduction

Heart rhythm disorders are common in the post-operative period following surgical myocardial revascularization (CABG). The incidence of any type of arrhythmia in the postoperative period can go up to 85%. While most are transient and short-term, it does not lead to deterioration of the postoperative course, in a smaller number of patients they can be predictors of various events that result in fatal outcome. Arrhythmias occur suddenly and need to be recognized and reacted in time. Standard monitoring consists of 12-channel electrocardiogram (ECG), laboratory findings and, if necessary, 24-hour HOLTER monitoring. Persistent arrhythmias increase overall morbidity and mortality, and costs treatments are increasing enormously.

Patients and methods

The prospective study analyzed patients of all age groups and sexes in whom angiographically coronary arterial disease was confirmed and who underwent surgery CABG. A total of 60 patients were screened during 2016. All age groups of both sexes in whom no rhythm disorders were previously recorded were included in the study.

Results

A total of 60 patients undergoing CABG were analyzed. The average age of patients was 63.56 8.55 years. The most preoperative factor was hypertension, which was recorded in 53 (88.33%) patients. The higher number of patients was operated using CPB 75.86%. The most commonly performed 3 aorto-coronary by-pass 45 (75%). The most common form of rhythm disorder was POAF, which occurred in 18 (30%) patients. In 24 patients, a change in heart rhythm was observed in the postoperative period in the group of operated ON pump techniques, while in the case of the application of Off pump technique only 5 patients were present, which was statistically significant (p <0.05).

Conclusion

Preoperative patient preparation and prophylaxis with good anesthesia monitoring and minimal trauma during surgery are the main preconditions for reducing the incidence of postoperative heart rhythm disorders.

Total and ionized serum magnesium and calcium levels during magnesium sulfate administration for preterm labor

Objective

This study aimed to estimate the association between total and ionized magnesium, and the changes in serum magnesium and calcium levels in patients with preterm labor during magnesium sulfate (MgSO₄) administration.

Methods

The study population included 64 women who were candidates for intravenous MgSO₄ treatment for preterm labor. Serial blood samples were taken and measured total magnesium (T-Mg), ionized magnesium (I-Mg), total calcium (T-Ca), and ionized calcium (I-Ca) levels every one-week interval (1st, 2nd, 3rd).

Results

There was no significant difference in T-Mg and I-Mg levels during MgSO₄ administration (P>0.05). There was no significant difference in T-Ca and I-Ca levels during MgSO₄ administration (P>0.05). Compared before and after administration of MgSO₄, T-Mg and I-Mg levels and T-Ca levels were changed allow statistically significant (P<0.05). But, there was no significant difference in the I-Ca serum levels before and after MgSO₄ administration (P=0.495). The I-Mg levels for patients with adverse effect were higher than other group but did not reach statistical significance (P>0.05). There was significant correlation between levels of I-Mg and T-Mg (I-Mg=0.395×T-Mg+0.144, P<0.01).

Conclusion

There were no significant differences in serum Mg and Ca levels during MgSO₄ administration for preterm labor. Compared to the before and after administration of MgSO₄, only I-Ca levels were not substantially changed. There are significant correlations between I-Mg and T-Mg levels during administration of MgSO₄ and I-Mg level seemed to have more correlation with adverse effect than T-Mg.

Hypomagnesemia Is Prevalent in Patients Undergoing Gynecologic Surgery by a Gynecologic Oncologist

OBJECTIVE

The aim of this study was to assess the incidence of and risk factors for hypomagnesemia in patients undergoing gynecologic surgery by a gynecologic oncologist.

METHODS

A retrospective chart review was performed on all patients undergoing surgery for gynecologic pathology from July 2011 to July 2015 by a single surgeon. Demographic data, surgical indication, surgery performed, preoperative laboratory values, postoperative laboratory values, and medical history were examined. Hypomagnesemia was defined as less than 1.8 mg/dL. Hypermagnesemia was defined as greater than 2.5 mg/dL.

RESULTS

Six hundred sixty-nine patients were identified for analysis. One hundred ninety-seven patients had hypomagnesemia (29.4%). Four hundred sixty-six patients had normal magnesium levels (69.5%), and 6 patients had hypermagnesemia (1%). Among patients with benign disease, 24.9% had preoperative hypomagnesemia compared with 32.7% of patients with a gynecologic malignancy. African American race (P = 0.041), diabetes mellitus (P < 0.001), and malignancy (P = 0.029) were all associated with preoperative hypomagnesemia. Diabetes and major surgery were associated with postoperative hypomagnesemia (P = 0.012 and P = 0.048, respectively). Hypomagnesemia was associated with increased preoperative and postoperative pain (P = 0.049 and P < 0.001, respectively) as well as postoperative hypokalemia (P = 0.001). Age, body mass index, hypertension, cancer type, hematocrit, surgical indication, and length of hospital stay were not associated with hypomagnesemia.

CONCLUSIONS

Perioperative hypomagnesemia is prevalent in patients undergoing gynecologic surgery by a gynecologic oncology, especially in patients who have a gynecologic malignancy. We recommend routine preoperative and postoperative evaluation of serum magnesium in all patients undergoing gynecologic surgery by a gynecologic oncologist.

A double-blind randomized clinical trial comparing different doses of magnesium in cardioplegic solution for prevention of atrial fibrillation after coronary artery bypass graft surgery

AIMS

This study aims to compare different doses of magnesium administered via cardioplegic solutions to prevent atrial fibrillation (AF) after coronary artery bypass graft (CABG) surgery.

METHODS

A total of 120 patients who were scheduled for elective CABG surgery using cardiopulmonary bypass were enrolled in this double-blind, randomized clinical trial. After fulfilling the inclusion criteria, they were randomly allocated into three groups (A, B, and C). Patients in groups A, B, and C received 60, 80, and 100 mg/kg of magnesium sulfate via cardioplegic solutions during aortic cross-clamp, respectively. Postoperative AF was assessed by continuous ECG monitoring during 3 days after surgery. Also serum magnesium, potassium, and calcium levels were assessed during the study period.

RESULTS

The findings revealed significant differences in four point measurements of serum magnesium level after surgery (P<.001). In particular, it was observed that 10 (26.3%) patients in group A, 4 (10%) patients in group B, and 2 (5.4%) patients in group C had AF after surgery. This indicates patients receiving magnesium at doses of 80 and 100 mg/kg had lower rates of AF occurrence than those receiving 60 mg/kg dose of magnesium (P=.02). Additionally, no significant difference was found in serum calcium and potassium concentration between the three groups throughout the study period.

CONCLUSION

Magnesium administration via the cardioplegic solution during aortic cross-clamping at doses of 80 and 100 mg/kg can reduce the risk of AF occurrence after CABG compared to the dose of 60 mg/kg. Considering the lower rate of AF incidence and shorter length of ICU stay in patients receiving 100 mg/kg of magnesium, it seems reasonable to administer 100 mg/kg magnesium during aortic cross-clamp to prevent postoperative AF.

Major publications in the critical care pharmacotherapy literature in 2015

PURPOSE

Recently published practice guidelines and research reports on pharmacotherapy in critical care patient populations are summarized.

SUMMARY

The Critical Care Pharmacotherapy Literature Update (CCPLU) Group is composed of over 50 experienced critical care pharmacists who evaluate 31 peer-reviewed journals monthly to identify literature pertaining to pharmacotherapy in critical care populations. Articles are chosen for summarization in a monthly CCPLU Group publication on the basis of applicability and relevance to clinical practice and strength of study design. From January to December 2015, a total of 121 articles were summarized; of these, 3 articles presenting clinical practice guidelines and 12 articles presenting original research findings were objectively selected for inclusion in this review based on their potential to change or reinforce current evidence-based practice. The reviewed guidelines address the management of intracranial hemorrhage (ICH), adult advanced cardiac life support (ACLS) and post-cardiac arrest care, and the management of supraventricular tachycardia (SVT). The reviewed research reports address topics such as nutrition in critically ill adults, administration of β-lactams for severe sepsis, anticoagulant selection in the context of continuous renal replacement therapy, early goal-directed therapy in septic shock, magnesium use for neuroprotection in acute stroke, and progesterone use in patients with traumatic brain injury.

CONCLUSION

Important recent additions to the critical care pharmacy literature include updated joint clinical practice guidelines on the management of spontaneous ICH, ACLS, and SVT.

Cardiology: Post-Cardiothoracic Surgery Atrial Fibrillation: A Review of Preventive Strategies

Objective:

To review the available literature addressing preventive strategies of post-cardiothoracic surgery atrial fibrillation (post-CTS atrial fibrillation).

Data Sources:

Pertinent articles related to the etiology, risk factors, and preventive strategies were identified through a MEDLINE search (1966–March 2007) using the MeSH terms atrial fibrillation, cardiothoracic surgery, cardiac surgery, etiology, neurohormonal, sympathetic, volume, fluid, inflammation, risk factors, operative, pacing, β-adrenergic blockers, amiodarone, sotalol, calcium-channel blockers, magnesium, HMG-CoA reductase inhibitors, statins, fatty acids, PUFA, steroids, and nonsteroidal antiinflammatory drugs.

Study Selection and Data Extraction:

Articles evaluated were limited to human studies, published in the English language, with a Jadad score greater than 3. References of identified articles were reviewed for additional pertinent articles.

Data Synthesis:

Post-CTS atrial fibrillation most commonly occurs on the second or third postoperative day, with an incidence of 20–50%. Etiology theories include neurohormonal activation, volume overload, and inflammation. Studies examining nonpharmacologic therapies have shown that maintenance of the anterior epicardial fat pad is not a viable prophylactic strategy. Biatrial cardiac pacing, especially in combination with amiodarone, is a viable preventive option. Withdrawal of preoperative β-blockers places patients at higher risk for atrial fibrillation; these drugs should be continued postoperatively. Evidence exists supporting the use of amiodarone, sotalol, and magnesium in addition to β-blockers. Since most of these strategies work by attenuating neurohormonal activation, adverse events, including hypotension and bradycardia, are of concern. Adding agents with antiinflammatory properties, including hydroxymethylglutaryl coenzyme A reductase inhibitors or corticosteroids, may prove to be of benefit. Additional studies using novel therapies are needed in addition to established preventive strategies.

Conclusions:

Available evidence supports the continuation of preoperative β-blockers, as well as prophylactic amiodarone, sotalol, and magnesium. Other novel therapies, mostly targeting inflammation, are under investigation and may provide additional strategies.

Atrial fibrillation and flutter following coronary artery bypass graft surgery: A retrospective study and review

Introduction and objectives

Atrial fibrillation is a common arrhythmia following coronary artery bypass graft surgery. Its incidence can range from 10 to 60% of patients undergoing coronary artery bypass graft. This rhythm can result in shorter or longer intervals between beats.

Methods

Medical records of 143 patients from the Queen’s Medical Center, Kuakini Medical Center, Saint Francis Medical Center, and Straub Hospital and Clinic, all of which are located in Honolulu, Hawaii were reviewed. An additional 39 records of patients who did not develop these complications were also reviewed as a control group. Patients were selected according to the ICD codes for atrial fibrillation/flutter and coronary artery bypass graft. Both anomalies can lead to increased health care costs, morbidity, and mortality. In this study, possible predisposing factors to these complications were investigated. The time of onset, weight gain, elapsed time, fluid status (in/out), hematocrit, and drug regimens were compared between the two groups.

Results

The differences in weight gain, fluid status, and hematocrit between the groups were not significant. There were a total of 17 different drugs prescribed to the group as a whole but not every patient received the same regimen.

Conclusions

Atrial fibrillation and flutter were found to be more common in males, particularly between the ages of 60 and 69 years. There were no other significant findings.

The effect of magnesium sulfate on post off-pump coronary artery bypass grafting bleeding

BACKGROUND

Magnesium level alteration may cause coagulation abnormality resulting in bleeding complication after off-pump coronary artery bypass grafting. In this study, we investigated the effect of magnesium on the postoperative coagulation profile and bleeding in OPCAB patients.

METHODS

In a double blind clinical trial, six hundred patients were randomly allocated to two groups: group A (n=150) and group B (n=450). Group A received 50mg/kg of magnesium sulfate (MS) in 100ml 0.9% NaCl solution over 20min before the anesthesia induction. Group B or control group received only 100ml 0.9% NaCl solution at the same time points. OPCAB was performed with standard technique and device. Blood samples were collected 30min before and 6h after the surgery to analyze hemoglobin and blood coagulation tests. Postoperative exploration for bleeding, blood transfusion, and volume of transfusion was recorded. The two groups compared with t-test and χ(2) tests and p-valve <0.05 were considered as significant.

RESULTS

However, postoperative hemoglobin was statistically lower in group A compared with group B, but platelet, PT, and aPTT tests were not statistically different between two groups. The serum MS level, exploration for bleeding, volume of packed cell transfusion, and volume of postoperative bleeding were statistically different between group A vs group B.

CONCLUSION

Preoperative MS use may be associated with the postoperative platelet dysfunction and increased tendency to bleeding. This is an important risk factor for postoperative bleeding in the OPCAB in absence of CPB use.

The incidence of hypomagnesaemia following abdominal aortic aneurysm surgery

INTRODUCTION

Magnesium is important for cardiac function. Hypomagnesaemia is associated with a higher incidence of arrhythmias and poorer outcomes in cardiac surgery. No studies have investigated the incidence or impact of postoperative hypomagnesaemia after abdominal aortic aneurysm (AAA) surgery. We aim to assess the incidence of hypomagnesaemia after AAA repair in our population.

METHODS

Retrospective analysis was performed of patients who underwent elective AAA surgery at a single vascular centre. The last 110 patients undergoing open or endovascular AAA repair were identified. The hospital pathology system was used to identify the immediate postoperative serum magnesium levels as well as patient demographics and admission details. Hypomagnesaemia was defined as serum magnesium of <0.7 mmol/l.

RESULTS

A total of 211 patients were studied and there were 3 deaths. Of the patients included, 101 underwent open elective AAA repair and 110 underwent endovascular repair. In the elective open repair group, 73 patients (73%) were hypomagnesaemic. In the endovascular repair group, 35 (32%) had hypomagnesaemia. A t-test showed a statistically significant difference in hypomagnesaemia between the open and endovascular groups (p<0.001).

CONCLUSIONS

AAA surgery is associated with a high incidence of postoperative hypomagnesaemia, which is significantly greater among open repair patients. This is likely to have an effect on cardiac activity and lead to cardiac complications such as arrhythmias and poorer postoperative outcomes, especially in the open AAA repair subgroup. This stresses the importance of serum magnesium and cardiac monitoring in the postoperative phase. A prospective study is proposed to further investigate these findings, and their potential implications on perioperative morbidity and mortality.

Magnesium basics

As a cofactor in numerous enzymatic reactions, magnesium fulfils various intracellular physiological functions. Thus, imbalance in magnesium status-primarily hypomagnesaemia as it is seen more often than hypermagnesaemia-might result in unwanted neuromuscular, cardiac or nervous disorders. Measuring total serum magnesium is a feasible and affordable way to monitor changes in magnesium status, although it does not necessarily reflect total body magnesium content. The following review focuses on the natural occurrence of magnesium and its physiological function. The absorption and excretion of magnesium as well as hypo- and hypermagnesaemia will be addressed.

Postoperative atrial fibrillation in non-cardiac and cardiac surgery: an overview

Postoperative atrial fibrillation (POAF) is the most common perioperative cardiac arrhythmia. A major risk factor for POAF is advanced age, both in non-cardiac and cardiac surgery. Following non-cardiac surgery, it is important to correct reversible conditions such as electrolytes imbalances to prevent the occurrence of POAF. Management of POAF consists of rate control and therapeutic anticoagulation if POAF persists for > 48 h and CHADS2 score > 2. After cardiac surgery, POAF affects a larger amount of patients. In addition to age, valve surgery carries the greatest risk for new AF. Rate control is the mainstay therapy in these patients. Prediction, prevention, and management of POAF should be further studied.

Sheep (Ovis aries) as a model for cardiovascular surgery and management before, during, and after cardiopulmonary bypass

Because of its similarity to humans in important respects, sheep (Ovis aries) are a common animal model for translational research in cardiovascular surgery. However, some unique aspects of sheep anatomy and physiology present challenges to its use in these complicated experiments. In this review, we discuss relevant anatomy and physiology of sheep and discuss management before, during, and after procedures requiring cardiopulmonary bypass to provide a concise source of information for veterinarians, technicians, and researchers developing and implementing protocols with this model.

Hypomagnesemia: a clinical perspective

Although magnesium is involved in a wide spectrum of vital functions in normal human physiology, the significance of hypomagnesemia and necessity for its treatment are under-recognized and underappreciated in clinical practice. In the current review, we first present an overview of the clinical significance of hypomagnesemia and normal magnesium metabolism, with a focus on renal magnesium handling. Subsequently, we review the literature for both congenital and acquired hypomagnesemic conditions that affect the various steps in normal magnesium metabolism. Finally, we present an approach to the routine evaluation and suggested management of hypomagnesemia.

Postoperative arrhythmias after cardiac surgery: incidence, risk factors, and therapeutic management

Arrhythmias are a known complication after cardiac surgery and represent a major cause of morbidity, increased length of hospital stay, and economic costs. However, little is known about incidence, risk factors, and treatment of early postoperative arrhythmias. Both tachyarrhythmias and bradyarrhythmias can present in the postoperative period. In this setting, atrial fibrillation is the most common heart rhythm disorder. Postoperative atrial fibrillation is often self-limiting, but it may require anticoagulation therapy and either a rate or rhythm control strategy. However, ventricular arrhythmias and conduction disturbances can also occur. Sustained ventricular arrhythmias in the recovery period after cardiac surgery may warrant acute treatment and long-term preventive strategy in the absence of reversible causes. Transient bradyarrhythmias may be managed with temporary pacing wires placed at surgery, but significant and persistent atrioventricular block or sinus node dysfunction can occur with the need for permanent pacing. We provide a complete and updated review about mechanisms, risk factors, and treatment strategies for the main postoperative arrhythmias.

Management strategies in cardiac surgery for postoperative atrial fibrillation: contemporary prophylaxis and futuristic anticoagulant possibilities

With more than a third of patients expected to endure the arrhythmia at any given time point, atrial fibrillation after cardiac surgery becomes a vexing problem in the postoperative care of cardiac surgery patients. The impact on patient care covers a spectrum from the more common clinically insignificant sequelae to debilitating embolic events. Despite this, postoperative atrial fibrillation generally masquerades as being insignificant, or at most as an anticipated inherent risk, merely extending one's hospital stay by a few days. As an independent risk factor for stroke, early and late mortality, and being a multibillion dollar strain on the healthcare system annually, postoperative atrial fibrillation is far more flagrant than a mere inherent risk. It is a serious medical quandary, which is not recognized as such. Though complete prevention is unrealistic, a step-wise treatment strategy that incorporates multiple preventative modalities can significantly reduce the impact of postoperative atrial fibrillation on patient care. The aims of this review are to present a brief overview of the arrhythmia's etiology, risk factors, and preventative strategies to reduce associated morbidities. Newer anticoagulants and the potential role of these drugs on future treatment paradigms are also discussed.

Magnesium supplementation reduces postoperative arrhythmias after cardiopulmonary bypass in pediatrics: a metaanalysis of randomized controlled trials

Postoperative arrhythmia (POA) is the most common complication encountered after cardiopulmonary bypass (CPB). The preventive effect of magnesium in POA has been confirmed by metaanalyses in adults, but less is known in pediatric patients. A metaanalysis of published trials was conducted to examine the efficacy of magnesium supplementation in POA prevention among pediatric patients undergoing CPB. Relevant trials were identified from electronic databases (Medline, Embase, Web of Science, and Cochrane library). Pooled relative risk (RR) and 95 % confidence intervals (CI) were calculated using Mantel-Haenszel random-effects models, and heterogeneity was determined qualitatively according to I (2) and chi-squared statistical analyses. Among 121 potentially relevant studies, five randomized controlled trials met the inclusion criteria, resulting in a pooled total of 348 participants. Compared with placebo, magnesium supplementation decreased the incidence of arrhythmia after CPB in pediatric patients by 66 % (RR, 0.34; 95 % CI, 0.18-0.65; P = 0.001), with no heterogeneity between trials (heterogeneity P = 0.68; I (2) = 0 %). Magnesium supplementation significantly reduces the incidence of postoperative arrhythmias in pediatric patients undergoing CPB. Although the findings encourage the use of magnesium as an alternative to postoperative arrhythmias after CPB in pediatric patients, higher-quality randomized clinical trials are necessary before the findings can be generalized.

Magnesium: a versatile drug for anesthesiologists

Magnesium sulfate has been used in preeclampsia patients in order to prevent seizure. It is also used for the treatment of arrhythmia and asthma and as an anesthetic adjunct in patients undergoing surgery for pheochromocytoma. However, its potentiating effects on perioperative analgesia and muscle relaxation have drawn attention recently. These characteristics of magnesium (anesthetic- and analgesic-sparing effect) enable anesthesiologists to reduce the use of anesthetics during surgery and the use of analgesics after surgery. Magnesium sulfate has a high therapeutic index and cost-effectiveness. Considering these diverse characteristics useful for anesthesia, appropriate use of magnesium sulfate would improve surgical outcome and patients' satisfaction.

Magnesium adjunctive therapy in atrial arrhythmias

Magnesium (Mg) is an important intracellular ion with cardiac metabolism and electrophysiologic properties. A large percentage of patients with arrhythmias have an intracellular Mg deficiency, which is out of line with serum Mg concentrations, and this may explain the rationale for Mg's benefits as an atrial antiarrhythmic agent. A current limitation of antiarrhythmic therapy is that the potential for cardiac risk offsets some of the benefits of therapy. Mg enhances the balance of benefits to harms by enhancing atrial antiarrhythmic efficacy and reducing antiarrhythmic proarrhythmia potential as well as providing direct antiarrhythmic efficacy when used as monotherapy in patients undergoing cardiothoracic surgery.

Risk Factors for Post-Coronary Artery Bypass Grafting (CABG) Atrial Fibrillation and the Role of Aspirin and Beta Blockers in its Prevention

Background: Atrial fibrillation/flutter (AF) is the most common arrhythmia following coronary artery bypass grafting (CABG) and it increases morbidity and mortality associated with this procedure. The purpose of this study was to evaluate the predictability of this arrhythmia using previously identified risk factors and to assess the efficacy of recommended prophylactic beta blocker (BB) therapy in the prevention of post CABG AF. Methods: We performed a retrospective chart analysis of consecutive patients undergoing elective CABG during 1 year period. Patients who developed new onset AF after the surgery were designated as cases and those who did not, as controls. 41 different variables were analyzed using Chi-square test and independent sample t-test. Multivariate analysis was carried out using logistic regression model. Results: 23% patients undergoing CABG developed AF during post-operative period. Statistically significant differences were observed between the two groups in terms of age, use of peri-operative Aspirin (ASA), current smoking, previous history of AF, left atrial size, history of congestive heart failure (CHF) and brain natriuretic peptide (BNP) levels. In terms of prophylactic therapy, preoperative BB did not independently protect against post CABG AF. On multivariate analysis, only age, use of ASA and previous history of AF remained as independent predictors of post CABG AF. Conclusion: In our study population, the use of preoperative BB did not independently decrease the risk of post-CABGAF. Age, peri-operative ASA use and previous history of AF remained strong independent predictors of post- operative AF.

Serum and dietary magnesium and incidence of atrial fibrillation in whites and in African Americans--Atherosclerosis Risk in Communities (ARIC) study

BACKGROUND

Low serum magnesium (Mg) has been associated with an increased risk of cardiovascular disease (CVD), including ventricular arrhythmias, but the association between serum or dietary Mg and atrial fibrillation (AF) has not been investigated.

METHODS AND RESULTS

A total of 14,290 men and women (75% white; 53% female; mean age, 54 years) free of AF at baseline participating in the Atherosclerosis Risk in Communities study in the United States, were studied. Incident AF cases through 2009 were ascertained from electrocardiograms, hospital discharge codes, and death certificates. Multivariate Cox proportional hazards regression was used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for AF associated with serum and dietary Mg quintiles. Over a median follow-up time of 20.6 years, 1,755 incident AF cases were identified. In multivariate models, lower serum Mg was associated with higher AF risk: compared to individuals in the middle quintile (≥ 0.80-0.83 mmol/L), the HR (95% CI) of AF in quintiles 1, 2, 4, and 5 were 1.34 (1.16-1.54), 0.99 (0.85-1.16), 1.04 (0.90-1.22), and 1.06 (0.91-1.23), respectively. There was no evidence of significant interactions between serum Mg and sex or race. No association between dietary Mg and AF risk was observed.

CONCLUSIONS

Lower serum Mg was associated with a higher AF risk, and this association was not different between whites and African Americans. Dietary Mg was not associated with AF risk.

The effects of magnesium on the course of atrial fibrillation and coagulation in patients with atrial fibrillation undergoing mitral valve annuloplasty

Background

Atrial fibrillation (AF) is the most common cardiac arrhythmia. Magnesium has been reported to be effective in reducing the incidence or prophylaxis of AF. Magnesium is also an essential constituent of many enzyme systems and plays a physiological role in coagulation regulation. The aim of the present study was to examine the effects of magnesium, whether magnesium infusion might decrease the incidence of AF and induce hypocoagulable state in patients with AF, who were undergoing mitral valve annuloplasty.

Methods

This prospective laboratory study was performed using blood from patients with AF undergoing mitral valve annuloplasty. The radial artery was punctured with a 20 gauge catheter and used for monitoring continuous arterial pressure and blood sampling. After anesthesia induction, 4 g of magnesium was mixed with 100 ml normal saline and infused for 5 minutes. Magnesium, calcium, activated clotting time (ACT) and thromboelastographic parameters were checked before and 60 minutes after the magnesium infusion. The electrocardiography changes after magnesium infusion were also checked before commencing cardiopulmonary bypass.

Results

After magnesium infusion, the serum level of magnesium increased significantly but serum calcium did not change significantly. ACT did not change significantly before or after magnesium infusion. The thromboelastographic parameters showed no significant changes before or after magnesium infusion. None of the patients converted to sinus rhythm from AF after the magnesium infusion.

Conclusions

A magnesium infusion did not influence the course of AF and coagulation in patients during prebypass period with AF undergoing mitral valve annuloplasty.

Review: Beyond the Guidelines: New and Novel Agents for the Prevention of Atrial Fibrillation After Cardiothoracic Surgery

Postoperative atrial fibrillation (POAF), a common complication of cardiac surgery, can increase the morbidity and mortality, as well as the costs of the surgery being preformed. Guidelines recommend the use of β-blockers, amiodarone, or sotalol to decrease the risk of experiencing POAF. However, none of these agents fully protect the patient from POAF, thus newer agents are needed to be used in combination with them. Many different agents have been studied to fit this role and may be grouped into 2 categories: agents with antiarrhythmic activity such as magnesium and polyunsaturated fatty acids and agents with anti-inflammatory activity such as statins and free radical scavengers. Most of these novel agents have been studied in a wide variety of trials; however, some clearly have more effect than others. Although none of these newer agents have the data required to make blanket recommendations for use at this point, given the safety profile and low costs of some, many continue to be evaluated in randomized-controlled trials.

Postoperative Care of the Cardiac Surgical Patient

The subspecialty of interventional cardiology began in 1977. Since then, the discipline of interventional cardiology has matured rapidly, particularly with regards to ischemic heart disease. As a result, more patients are undergoing percutaneous catheter interventional therapy for ischemic heart disease and fewer patients are undergoing surgical myocardial revascularization. Those patients referred for surgical revascularization are generally older and have more complex problems. Furthermore, as the population ages more patients are referred to surgery for valvular heart disease. The result of these changes is a population of surgical patients older and sicker than previously treated.

Atrial Fibrillation After Cardiac Surgery: Does Prophylactic Therapy Decrease Adverse Outcomes Associated With Atrial Fibrillation

Atrial fibrillation is a common problem following cardiac surgery. Atrial fibrillation occurs in 30% to 50% patients during postoperative period. Postoperative atrial fibrillation often results in increased length of hospital stay, increased cost of postoperative hospitalization, heart failure, and, less frequently, cerebrovascular accident and death. Because postoperative atrial fibrillation is such a significant problem, several studies have attempted to find a safe and effective treatment for its prevention. In this article, we review the evidence for various prophylactic therapies and make an attempt to answer the following: (1) Can postoperative atrial fibrillation be prevented? (2) Is prophylactic therapy for postoperative atrial fibrillation safe? (3) Does prevention of postoperative atrial fibrillation prevent adverse outcomes associated with it? Evidence for safety and efficacy or lack of β-blockers, sotalol, amiodarone, intravenous magnesium, and atrial pacing is reviewed and current recommendations by the American College of Cardiology/American Heart Association/European Society of Cardiology are presented.

Meta-analysis of magnesium therapy for the acute management of rapid atrial fibrillation

The profile of electrophysiologic effects of magnesium on the heart suggests that magnesium might be effective in the treatment of atrial fibrillation (AF) in terms of rhythm and rate control. We aimed to investigate the efficacy of magnesium administration in the acute treatment of rapid AF. Randomized controlled trials comparing intravenous magnesium versus placebo or antiarrhythmic agents for the acute management of rapid AF were included. Nine electronic databases were searched for relevant trials from the earliest possible dates through June 2005, as were abstract books from 8 cardiovascular meetings held in the past 10 years. We analyzed all outcomes using a fixed-effect model because of the low number of trials in each comparison. The results were expressed as relative risks (RRs) or odds ratios (ORs) for dichotomous outcomes and weighted mean differences for continuous outcomes, along with their 95% confidence intervals (CIs). Data were pooled for 4 trials (n=303) and 8 trials (n=476), respectively, for rate control (<100 beats/min) and rhythm control. Magnesium was effective in achieving rate control (OR 1.96, 95% CI 1.24 to 3.08) or rhythm control (OR, 1.60, 95% CI 1.07 to 2.39). An overall response was achieved in 86% and 56% of patients in the magnesium and control groups, respectively (OR 4.61 95% CI 2.67 to 7.96). Time to response (in hours) was significantly shorter in the magnesium group (weighted mean difference, -6.98; 95% CI -9.27 to -4.68). The risk of having a major adverse effect in the magnesium group was similar to that in the placebo group (RR 0.85, 95% CI 0.44 to 1.61). In conclusion, the present meta-analysis of published data suggests that intravenous magnesium administration is an effective and safe strategy for the acute management of rapid AF.

The effects of surgery and anesthesia on blood magnesium and calcium concentrations in canine and feline patients

OBJECTIVE

To demonstrate the effect of anesthesia and surgery on serum ionized magnesium and ionized calcium concentrations in clinical canine and feline patients.

ANIMALS

37 client-owned dogs, ASA PS I-III and 10 client-owned cats, ASA PS I, all receiving anesthesia for elective or emergent surgery at a Veterinary Teaching Hospital.

MATERIALS AND METHODS

Plasma ionized and serum total magnesium, and plasma ionized calcium were measured prior to and after a group-standardized anesthetic protocol.

RESULTS

Regardless of pre-operative medication (hydromorphone or butorphanol), anesthetic induction (thiopental or lidocaine/hydromorphone/diazepam (LHD) and propofol combination), or type of surgical procedure (peripheral surgery or laparotomy), post-operative plasma ionized calcium concentration decreased in all groups of dogs, while post-operative plasma ionized magnesium increased in all groups, although the changes were not always significant. The dogs who were induced with an LHD and propofol technique had a greater increase in ionized magnesium (0.36 +/- 0.07 to 0.42 +/- 0.07 mmol L(-1)) than the group in which anesthesia was induced with thiopental (0.41 +/- 0.07 to 0.42 +/- 0.07 mmol L(-1), p = 0.009). The cats showed similar changes in ionized magnesium and ionized calcium, and also had a significant increase in serum total magnesium (2.17 +/- 0.20 to 2.31 +/- 0.25 mg dL(-1), p = 0.009) CONCLUSIONS, CLINICAL RELEVANCE: A post-operative decrease in ionized calcium was demonstrated in healthy animals, as well as an increase in ionized or total magnesium after various anesthetic protocols and surgeries. These changes, while statistically significant, do not appear to be clinically significant, as values remained within reference ranges at all times.

Prophylactic therapy to prevent atrial arrhythmia after cardiac surgery

PURPOSE OF REVIEW

Atrial fibrillation after cardiac surgery is associated with adverse outcomes and increased costs. Accordingly, therapy should be provided to prevent postoperative atrial fibrillation. The evaluation of therapies to do so is an area of active investigation with significant recent advances. The purpose of this review is to summarize these recent advances in the context of our previous knowledge base regarding the prevention of postoperative atrial fibrillation.

RECENT FINDINGS

Recent evaluations of therapy to prevent postoperative atrial fibrillation have raised the prominence of prophylactic amiodarone, redefined the efficacy of prophylactic standard beta-blockers in contemporary cardiac surgical populations, provided further evidence for the use of prophylactic sotalol, magnesium, and atrial pacing, and identified new approaches, including the use of combination therapy, for the prevention of postoperative atrial fibrillation.

SUMMARY

According to newly released ACC/AHA/ESC guidelines, use of standard beta-blockers or amiodarone to prevent postoperative atrial fibrillation have a level of evidence of A. Use of prophylactic sotalol has a level of evidence of B, while the use of prophylactic intravenous magnesium or atrial pacing has a lower level of evidence. The use of novel and combination therapies continues to be an area of active investigation.

Physiology of epithelial Ca2+ and Mg2+ transport

Ca2+ and Mg2+ are essential ions in a wide variety of cellular processes and form a major constituent of bone. It is, therefore, essential that the balance of these ions is strictly maintained. In the last decade, major breakthrough discoveries have vastly expanded our knowledge of the mechanisms underlying epithelial Ca2+ and Mg2+ transport. The genetic defects underlying various disorders with altered Ca2+ and/or Mg2+ handling have been determined. Recently, this yielded the molecular identification of TRPM6 as the gatekeeper of epithelial Mg2+ transport. Furthermore, expression cloning strategies have elucidated two novel members of the transient receptor potential family, TRPV5 and TRPV6, as pivotal ion channels determining transcellular Ca2+ transport. These two channels are regulated by a variety of factors, some historically strongly linked to Ca2+ homeostasis, others identified in a more serendipitous manner. Herein we review the processes of epithelial Ca2+ and Mg2+ transport, the molecular mechanisms involved, and the various forms of regulation.

Effect of Low-Dose Amiodarone and Magnesium Combination on Atrial Fibrillation After Coronary Artery Surgery

BACKGROUND

To evaluate whether postoperative administration of intravenous low-dose amiodarone and magnesium sulfate (MgSO(4)) combination would reduce the incidence of atrial fibrillation following coronary artery bypass grafting (CABG) in normomagnesemic high-risk patients for postoperative atrial fibrillation (POAF).

METHODS

A total of 136 patients undergoing elective CABG and had > or =3 risk factors for POAF were prospectively randomized to one of three groups, to receive a single dose of amiodarone (5 mg/kg) and MgSO(4) (1.5 g) (combination group, n = 44), or an equal dose of amiodarone (amiodarone group, n = 44) or equal volumes of saline (control group, n = 48) at early postoperative period. Continuous electrocardiographic (ECG) monitoring was performed for the first 48 hours and an ECG was recorded every 8 hours later. POAF longer than 30 minutes or for any length requiring treatment, and the drug-related side effects were recorded.

RESULTS

The study population showed a homogeneous distribution regarding risk factors for POAF and there was no significant difference in patient characteristics, echocardiographic variables, or operative variables among three groups. POAF developed in 4 patients in combination group, in 16 patients in amiodarone group and in 16 patients in control group, representing a 24% relative risk reduction between the combination group and control group (p = 0.023). No statistically significant difference regarding incidence of POAF was observed between amiodarone and control groups.

CONCLUSIONS

Combined prophylactic therapy with amiodarone and MgSO(4) at the early postoperative period without a maintenance phase is an effective, simple, well-tolerated, and possibly cost-effective regimen to prevent POAF in normomagnesemic, high-risk patients.

Serum ionized magnesium during magnesium sulfate administration for preterm labor and preeclampsia

OBJECTIVE

The purpose of this study is to estimate the relations between ionized and total Mg levels during MgSO4 administration in patients with preterm labor and preeclampsia.

METHODS

Forty-three pregnant patients who were candidates for MgSO4 were studied (preterm labor, 27; preeclampsia, 16). The administration method was intravenous injection of MgSO4 4 g over 30 min followed by 1-2 g/h. Ionized Mg was measured by the selective ion electrode method at bedside, and compared it with total Mg levels.

RESULTS

Significant correlation was existed between levels of ionized and total Mg throughout therapy for both preterm labor (ionized Mg=0.19 x total Mg+0.19; r=0.61, p<0.001) and preeclampsia (ionized Mg=0.20 x total Mg+0.14; r=0.60, p<0.001).

CONCLUSION

There are correlations between ionized and total Mg levels during administration of MgSO4 for both preterm labor and preeclampsia.

Atrial fibrillation post-cardiac surgery: changing perspectives

Perioperative atrial fibrillation (AF) is one of the most frequent complications of cardiac surgery. Its development is associated with an increased morbidity and mortality, for example from perioperative stroke, as well as ventricular arrhythmias, postoperative myocardial infarction, congestive cardiac failure, renal failure, increased use of inotropic medications and the need for intra-aortic balloon pump. Furthermore, AF after cardiac surgery results in prolonged hospitalization after the procedure, as well as an excess utilization of hospital resources and increased hospital costs. Given the importance of AF for patient outcome, a wide variety of prophylactic pharmacologic strategies have been evaluated. The risk of post-operative AF should be reduced by the administration of amiodarone, a beta-blocker, sotalol or rate-limiting calcium antagonists. In addition, in patients undergoing cardiac surgery on pre-existing beta-blocker therapy, this treatment should be continued unless contraindications develop (such as post-operative bradycardia or hypotension). Unless contraindicated, a rhythm control strategy is recommended as the initial option for the treatment of post-operative AF following cardiothoracic surgery. More recently, some data regarding magnesium, statins and n-3 polyunsaturated fatty acids in reducing post-op AF are available. Clearly, perspectives are changing in our management of this common arrhythmia.

Early postoperative arrhythmias after pediatric cardiac surgery

OBJECTIVE

Early postoperative arrhythmias are a known complication of cardiac surgery; however, little data exists specific to pediatrics. The purpose of this study was to determine the incidence and risk factors associated with the development of arrhythmias immediately after surgery in a pediatric population.

METHODS

Data were collected in a prospective observational format from pediatric patients undergoing cardiac surgery between September 2000 and May 2003. This format included age, anatomy, surgical repair, and serum magnesium and calcium levels, as well as cardiopulmonary bypass and aortic crossclamp times. Patients were continuously monitored, and hemodynamically significant arrhythmias were recorded.

RESULTS

Arrhythmias occurred in 28 of the 189 patients enrolled (15%) including 16 with junctional ectopic tachycardia, 7 with complete atrioventricular block, 4 with ventricular tachycardia, and 1 with re-entrant supraventricular tachycardia. Significant differences were found between the arrhythmia and nonarrhythmia groups with regard to age (22 vs 45 months), cardiopulmonary bypass time (189 vs 109 minutes), and aortic crossclamp time (105 vs 44 minutes); P < .05. Magnesium and calcium levels were not significantly different between the groups. Two repairs carried an increased risk: complete atrioventricular septal defect repair, 8 of 11 patients (72%), and the arterial switch 5 of 8 patients (62.5%); P < .05. Atrioventricular septal defects had an even higher incidence when controlled for age, bypass time, and crossclamp time (odds ratio = 7.65).

CONCLUSIONS

Hemodynamically significant postoperative arrhythmias are a frequent complication of pediatric cardiac surgery. Younger age and longer bypass and crossclamp times are risk factors for arrhythmia. In addition, the repair of atrioventricular septal defects carries an independent risk of arrhythmias.

Magnesium moderately decreases remifentanil dosage required for pain management after cardiac surgery †

BACKGROUND

Magnesium is a calcium and an NMDA-receptor antagonist and can modify important mechanisms of nociception. We evaluated the co-analgesic effect of magnesium in the postoperative setting after on-pump cardiac surgery.

METHODS

Forty patients randomly received either magnesium gluconate as an i.v. bolus of 0.21 mmol kg(-1) (86.5 mg kg(-1)) followed by a continuous infusion of 0.03 mmol(-1) kg(-1) h(-1) (13.8 mg kg(-1) h(-1)) or placebo for 12 h after tracheal extubation. After surgery, remifentanil was decreased to 0.05 microg kg(-1) min(-1) and titrated according to a pain intensity score (PIS, range 1-6) in the intubated, awake patient and a VAS scale (range 1-100) after extubation. If PIS was > or =3 or VAS > or =30, the infusion was increased by 0.01 microg kg(-1) min(-1); if ventilatory frequency was < or =10 min(-1) it was decreased by the same magnitude.

RESULTS

Magnesium lowered the cumulative remifentanil requirement after surgery (P<0.05). PIS > or =3 was more frequent in the placebo group (P<0.05). Despite increased remifentanil demand, VAS scores were also higher in the placebo group at 8 (2 vs 8) and 9 h after extubation (2 vs 7) (P<0.05). Dose reductions attributable to a ventilatory frequency < or =10 min(-1) occurred more often in the magnesium group (17 vs 6; P<0.05). However, time to tracheal extubation was not prolonged.

CONCLUSIONS

Magnesium gluconate moderately reduced the remifentanil consumption without serious side-effects. The opioid-sparing effect of magnesium may be greater at higher pain intensities and with increased dosages.