Effect Of Intravenous Magnesium Sulfate Research Articles

Effect of intravenous magnesium sulfate on mortality in patients with severe acute asthma

Intravenous magnesium sulfate is used as adjunctive therapy for severe asthma exacerbations. However, previous randomized controlled trials of the administration of intravenous magnesium sulfate for asthma exacerbations have shown mixed results, and no study has evaluated its effect on mortality in patients with life-threatening asthma. The objective of this study was to investigate the association between intravenous magnesium sulfate administration and mortality in patients with severe asthma. Patients with severe asthma requiring intravenous corticosteroids and oxygenation were selected using the Japanese Diagnosis Procedure Combination inpatient database. One-to-one propensity score matching was performed between patients having received or not intravenous magnesium sulfate. Primary outcomes were 7-, 14- and 28-day mortalities. Secondary outcomes were total dose of intravenous corticosteroids during hospitalization, duration of mechanical ventilation and length of stay. Among 14,122 eligible patients, 619 received intravenous magnesium sulfate. Propensity score matching created a matched cohort of 599 pairs with and without intravenous magnesium sulfate. There were no significant differences between patients with and without intravenous magnesium sulfate in terms of 28-day mortality (1.3% vs 1.8%, P = 0.488), median total dose of intravenous corticosteroids (2400 mg vs 2400 mg, P = 0.580), median duration of mechanical ventilation (1 day vs 1 day, P = 0.118) and median length of stay (16 days vs 13 days, P = 0.640). This study found no significant benefit of intravenous magnesium sulfate use in terms of mortality in patients with severe acute asthma.

English

English

Beneficial effect of intravenous magnesium sulphate in term neonates with perinatal asphyxia

Background: The objective of the study was to determine the role of intravenous magnesium sulphate therapy in promoting early recovery and favourable neurological outcome at discharge for asphyxiated term neonates. Methods: Term neonates with birth asphyxia were assigned randomly, to either magnesium sulphate infusion (Study group) or Comparison group. Neonates in both the groups were treated according to routine NICU protocol for birth asphyxia. Study group in addition received magnesium sulphate intravenous infusion at 250 mg/kg/dose (1 ml/kg/dose in 20 ml of 5% dextrose solution) over 1 hour within 6 hours of birth with 2 additional doses repeated after 24 hours and later at 48 hours. Vitals were monitored continuously. Clinical assessments including detailed neurological examinations were done in both the groups till their discharge from NICU. Results: Each group included 60 neonates. More number of neonates in the study group had their seizures controlled by a single anticonvulsant as against the comparison group. In the study group 92% neonates had seizure control within 2 days as compared to 70% in the comparison group which was statistically significant(p=0.048). There was early establishment of feeds amongst the study group as against comparison group which was statistically significant. In study group, 47 neonates (84%) recovered from abnormal neurological examination within 4 days as compared to 26 (53%) in comparison group which was statistically significant (p=0.0001). Conclusions: Intravenous magnesium sulphate within 6 hours of life to term neonates with birth asphyxia helps in early seizure control, early recovery from abnormal neurological signs, early establishment of feeds and fewer chances of neurological abnormalities at discharge.

English

English

Effects of Intravenous Magnesium Sulfate on the Prevention of Pain Following Injection of Microemulsion Propofol

Objective: The aim of this study was to investigate the effects of intravenous magnesium sulfate on the prevention of pain during the injection of microemulsion propofol. Magnesium is a known calcium channel blocker and a physiological N-methyl-D-aspartate receptor antagonist. Methods: American Society of Anesthesiologists I and II adults (n= 114) undergoing general anesthesia for surgery were randomly assigned into two groups (n= 57 per group). This study was designed in prospective and double-blind manner. Patients in the LM group (n= 57) received pretreatment with 2% lidocaine (40 mg) and magnesium sulfate 10 mg/kg, while patients in group L (n= 57) received pretreatment with 2% lidocaine (40 mg) and normal saline (2 mL) accompanied by venous occlusion. Induction with microemulsion propofol (Aquafol) 2 mg/kg was accomplished following the release of venous occlusion. Pain intensity was assessed on a four-point scale according to patient movement (grade 0, no movement; grade 1, movement in wrist only; grade 2, movement in the upper arm & shoulder of injected arm; grade 3, generalized movement). Systolic blood pressure, diastolic blood pressure, and heart rate were evaluated. Results: A significant difference in pain intensity following injection of microemulsion propofol between the groups was found (P< 0.05). In addition, the incidence of hypertension after injection was lower in the LM group than in the L group (P< 0.05). Conclusion: The combination of magnesium and lidocaine are effective in attenuating the pain induced by microemulsion propofol injection when compared with lidocaine alone.

Effect of magnesium on functional outcome and paraclinical parameters of patients undergoing supratentorial craniotomy for brain tumors: a randomized controlled trial.

Several studies have demonstrated that magnesium (Mg) plays an important role in the prevention and treatment of central nervous system (CNS) insults. In this study, we tested the effect of intravenous magnesium sulfate (MgSO4) on the outcome of patients with brain tumors who underwent craniotomy. The outcome was defined clinically as the Barthel index score and paraclinically as blood levels of NSE (neuron-specific enloase) and S100Β protein. Sixty patients were randomly divided into two groups of 30 patients: the treatment and control groups. In the treatment group, 5 g of MgSO4 in normal saline was infused in 6 h 2 days before surgery, and the same dosage was repeated the day before and during surgery. The control group received placebo. Serum S100Β and NSE concentrations were measured at baseline before administration of magnesium, before surgery, and on the 2nd postoperative day. The Barthel index score was evaluated and registered before surgery, 3, and 6 months after the operation. The study results showed a significant change in S100Β protein levels before and after surgery (p < 0.05), but we could not find similar results for NSE protein and the Barthel index score. There was a correlation between NSE protein and the Barthel index. The results of this study revealed that administration of intravenous MgSO4 before and during surgery is safe and effective in reducing S100B protein levels in patients undergoing supratentorial craniotomy for brain tumors. Further studies to elucidate the pathophysiology of brain injuries and role of magnesium are warranted.

A Double Blind Comparative Study of Efficacy of Intravenous Magnesium Sulphate with Lignocaine and Intravenous Clonidine with Lignocaine in Attenuating Hemodynamic Response to Laryngoscopy and Tracheal Intubation during General Anaesthesia

Background and objectives: Laryngoscopy and tracheal intubation is invariably associated with a reflex sympathetic pressor response resulting in elevated heart rate and blood pressures. This may prove detrimental in high risk patients. The main objectives of the present study are: To study the effect of intravenous magnesium sulphate 30 mg/kg with intravenous lignocaine 1.5mg/kg, and intravenous clonidine 3mcg/kg with intravenous lignocaine 1.5mg/kg on changes in the Systolic blood pressure (SBP), Diastolic blood pressure (DBP) and Mean arterial blood pressure (MAP) during laryngoscopy and intubation under general anesthesia. Methods: 60 ASA I and II status normotensive patients scheduled for elective surgical Procedures were selected randomly and divided into three groups of 20 each. All patients received premedication with study drug. Induction of anesthesia was standardized for all patients who received, thiopentone 5 mg/kg i.v. and preservative free lignoaine 1.5mg i.v and were relaxed with succinylcholine 2mg/kg i.v. and laryngoscopy and intubation is done with appropriate sized endotracheal tube. HR, systolic, diastolic blood pressure were recorded noninvasively before induction, postintubation, 1,3,5,7 and 10 minutes from the onset of laryngoscopy. ‘z’ test was used for statistical analysis. Results: The basal and pre laryngoscopy mean SBP and standard deviations in CL group were 122.15 +/- 8.12 and114.50 +/- 7.30 respectively. In ML group basal systolic blood pressure was 117.30 -+-/- 9.78. After giving study drug prelaryngoscopy SBP decreased by 3mm of mm Hg to 114.15 +1- 15.26. Conclusion: Both study drugs were more effective in attenuation of pressor response to intubation than when lignocaine alone was used. Key words: Attenuation, Pressor response, Laryngoscopy, Intubation, Lignocaine, Magnesium sulphate, Clonidines

Comparison of Analgesic Effect of Intravenous Magnesium Sulphate &amp; Ketorolac in Management of Acute Pain in Upper Limb Orthopaedic Trauma

Comparison of Analgesic Effect of Intravenous Magnesium Sulphate &amp; Ketorolac in Management of Acute Pain in Upper Limb Orthopaedic Trauma

Effect of Magnesium Sulphate on Fetal Heart Rate Parameters: A Systematic Review

ObjectiveTo examine the potential effects of intravenous magnesium sulphate (MgSO4) administration on antepartum and intrapartum fetal heart rate (FHR) parameters measured by cardiotocography (CTG) or electronic fetal monitoring (EFM). MethodsWe undertook a systematic review of randomized controlled trials, observational studies, and case series. Studies were reviewed independently by two reviewers and qualitatively analyzed with regard to CTG/EFM parameters (baseline FHR, variability and acceleration-deceleration patterns), types of participants, interventions offered, and outcomes reported. ResultsOf 18 included studies, two were RCTs (72 women); 12 were prospective observational studies (269 women), 10 of which were of a pre- and post-intervention design; one was a prospective cohort study (36 women) and three were retrospective cohort studies (555 women). Lower baseline FHR was associated with MgSO4 exposure in seven of nine relevant studies. Decreased FHR variability was reported in nine of 12 relevant studies. Reductions in reactivity or acceleration pattern were seen in four of six relevant studies without an increase in decelerative patterns. All changes were small and not associated with adverse clinical outcomes. ConclusionMaternal administration of MgSO4 for eclampsia prophylaxis/treatment, tocolysis or fetal neuroprotection appears to have a small negative effect on FHR, variability, and accelerative pattern, but is not sufficient clinically to warrant medical intervention.

The Effect of Intravenous Magnesium Sulphate Treatment on the Spinal Anaesthesia Produced by Bupivacaine in Pre-eclamptic Patients.

In our study, the effect of intravenous magnesium sulphate in normal and pre-eclamptic patients on spinal anaesthesia produced by bupivacaine was investigated. Sixty-four pregnant (32 normal and 32 pre-eclamptic) were accepted in this study. Pregnants were divided into four groups as patients given intravenous magnesium sulphate and as control. Spinal anaesthesia was induced with 12.5 mg 0.5% hyperbaric bupivacaine. Intraoperative and postoperative haemodynamic variables, sensorial block periods, onset times of sensorial and motor block, maximum sensorial block levels, the time to reach maximum block level, Bromage scores, consumptions of intraoperative analgesic and ephedrine, the quality of anaesthesia, the duration of spinal anaesthesia and magnesium levels in blood and cerebrospinal fluid were measured and recorded. The level of magnesium in blood and cerebrospinal fluid was significantly higher in the group given magnesium in pre-eclamptic patients (p<0.01). Onset of sensory block times were significantly longer in intravenous magnesium group than in groups 1, 2 and 3 (p<0.05). Onset of motor block times were significantly longer and the duration of anaesthesia was shorter in groups given magnesium (p<0.05). Although the quality of anaesthesia was similar, supplemental analgesic consumption was significantly higher in pre-eclamptic pregnants given magnesium sulphate than in pre-eclamptic pregnants who were not given magnesium sulphate (p<0.05). Intravenous magnesium sulphate treatment during the spinal anaesthesia produced by bupivacaine extended the onset of sensory and motor block times, shortened the duration of spinal anaesthesia and therefore led to early analgesic requirement.

Magnesium Sulfate in Exacerbations of COPD in Patients Admitted to Internal Medicine Ward.

The purpose of this study was to examine the effect of intravenous magnesium sulfate on patients with COPD exacerbation requiring hospitalization. In this randomized clinical trial 30 patients with COPD exacerbation were studied. Patients were randomly assigned to group A (case) who concurrent with standard therapy received 2 g magnesium sulfate in normal saline infused in 20 minutes on days one to three and group B (control) who received standard medications and placebo. PEFR and FEV1 were measured by before, 45 minutes and third day of entering the study. Vital signs HR, BP, RR, temperature and SpO2 were monitored during hospitalization. 21 males and 9 females patients with mean age of 68 ± 9 years, case 67 ± 10 and control 70 ± 8 were studied (15 patients in each arm of study). The mean pretreatment FEV1 was 26% ± 12, and 35% ± 18 in case and control groups respectively (P=0.137). FEV1 after 45 minutes in case group was 27% ± 9 and control group 36% ± 20 (p=0.122). FEV1 after 3 days of study was 32% ± 17 in case and 41% ± 22 in control groups (P=0.205). The mean pretreatment PEFR was 126 ± 76 l/min in case and 142 ± 62 l/min in control groups (P=0.46). Changes in PEFR were not significant 45 min (p=0.540) and 3 days (p=0.733) of the administration of intravenous magnesium sulfate. Duration of hospital stay between the two groups did not show any significant difference. This study showed that administration of intravenous magnesium sulfate in hospitalized patients with COPD exacerbation neither revealed any significant bronchodilating effect nor reduced duration of hospital stay.

English

AIMS AND OBJECTIVES: To compare the effect of intravenous Magnesium sulfate and Esmolol in attenuating the hemodynamic response to laryngoscopy and endo-tracheal intubation. METHODS: A prospective study was conducted with sixty ASA (American society of Anesthesiologists) grade I and II patients undergoing elective surgery under general anesthesia who were selected to receive Esmolol hydrochloride 1.5 mg/kg or Magnesium sulfate 50 mg/kg randomly. Heart rate and blood pressure recording were done pre-intubation, immediately after intubation and at 2 minutes and 5 minutes after intubation. RESULTS: There was a significant rise in heart rate in Group M as compared to Group E (P<0.05). No significant difference in mean arterial pressure was seen in both groups. CONCLUSION: Esmolol is a better agent to attenuate hemodynamic response to laryngoscopy and intubation than magnesium sulfate as it attenuates the rise in both heart rate and blood pressure.

The effect of intravenous magnesium sulfate and lidocaine in hemodynamic responses to endotracheal intubation in elective coronary artery bypass grafting: a randomized controlled clinical trial.

Background:There have been many concerns about alteration in hemodynamic parameters within and shortly after endotracheal intubation (ETI) in patients scheduled for elective coronary artery bypass grafting (CABG).Objectives:We compared the attenuation effect of magnesium sulfate and lidocaine on hemodynamic responses after ETI, in patients undergoing CABG.Patients and Methods:In this randomized controlled trial 150 patients undergoing elective CABG were enrolled. Included patients were randomly allocated to three groups and received lidocaine (1.5 mg/kg), magnesium sulfate (50 mg/kg within five minute), or normal saline, 90 seconds before ETI. Baseline hemodynamic parameters including heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) were recorded immediately before anesthesia induction, before intubation, immediately after intubation, and at second and fifth minutes after intubation.Results:The baseline hemodynamic variables had no deference among the three groups. HR between intubation and five minute after intubation was significantly lower in two groups received lidocaine or magnesium sulfate in comparison with placebo group. Lidocaine induced more than 20% decrease in HR and MAP immediately after intubation; hence, lidocaine group showed significant MAP reduction in comparison with the two other groups.Conclusions:Lidocaine induced hemodynamic instability but premedication of magnesium sulfate maintained hemodynamic stability after intubation. Therefore, in patients undergoing CABG who received high-dose intravenous analgesic for general anesthesia, the administration of magnesium sulfate might result in maintaining hemodynamic stability after ETI in comparison with lidocaine.

Effect of intravenous magnesium sulfate during operation on propofol,remifentanil consumption and postoperative adverse events

Effect of intravenous magnesium sulfate during operation on propofol,remifentanil consumption and postoperative adverse events

The effect of intravenous magnesium sulfate on serum levels of N-terminal pro-brain natriuretic peptide (NT pro-BNP) in elective CABG with cardiopulmonary bypass

Nowadays, many patients undergo coronary artery bypass grafting (CABG) with a cardiopulmonary bypass (CPB); while a number of therapeutic agents have been used to suppress its related inflammatory process. Magnesium sulfate (MgSO4) solution has been used as an anti-inflammatory agent. Among the cardiac biomarkers, N-terminal pro brain natriuretic peptide (NT Pro-BNP) is one of the most widely recognized. We performed this study to assess the effect of MgSO4 solution on NT Pro-BNP levels in patients undergoing CABG with CPB. In a double-blind clinical trial, after IRB approval for ethical considerations, during a 12-month period, 88 adult patients aged 40-70 years qualified for the study after inclusion and exclusion criteria were considered. After random allocation of the patients between the two groups, anesthesia, surgical procedure, cardiopulmonary bypass (CPB) methods, and postoperative care were made as similar as possible; however, one group received a MgSO4 infusion (15 mg/kg/h) and the other group saline (placebo). Pre- and post-operative levels of NT Pro-BNP were assessed using an electrochemical luminescence immunoassay in an Elecsys 2010 (Roche, Indianapolis, IN, USA). The results were compared using a Student's t-test. A P value less than 5% was considered significant. The MgSO4 group had shorter postoperative mechanical ventilation, lower postoperative morphine requirements and lower postoperative pain scores. Also, 24 h postoperative NT Pro-BNP levels were significantly lower in the MgSO4 group. Administration of MgSO4 in elective CABG with CPB can decrease the postoperative NT Pro-BNP levels; also, it decreases their time of postoperative mechanical ventilation.

PP024. Effects of intravenous magnesium sulfate on the characteristics of eclamptic seizures induced by electrical stimuli in a rat preeclampsia/eclampsia model

Eclampsia is a serious complication of pregnancy and remains a leading cause of maternal mortality worldwide. Magnesium sulfate is commonly used in the prophylaxis and treatment of eclampsia. However, uncertainty remain regarding its anticonvulsant mechanism(s) of action. This study examined the effects of intravenous magnesium sulfate on the characteristics of eclamptic seizures in a rat preeclampsia/eclampsia model. All rats were implanted with stainless nickel-cadmium alloy bipolar electrodes one week before fertilization. Next, an experimental rat preeclampsia (PE) model was induced on gestational day 14 by anaesthetising rats and infusing over 1 hour into their tail veins lipopolysaccharide (LPS) (1.0μg/kg body weight) (with control rats receiving normal saline). The rats were then divided into three groups: a normal pregnancy (NP) group (n=6) which received a continuous infusion of saline; a control PE model group (n=7) (which had previously received the LPS treatment) which also received a continuous infusion of saline; and a treated PE model group (n=8) (which had previously received the LPS treatment) which received a continuous infusion of magnesium sulfate (60mg/kg/day). The continuous infusions in all three groups were delivered by implanted osmotic minipumps . Measurements were made of blood pressure, albuminuria, serum ALT, AST, and creatinine, BUN and serum magnesium concentrations. On gestational day 18, all experimental rats received a standardized electrical stimulus. Seizure activity was assessed using electroencephalogram (EEG) recordings. Terminations of pregnancy were performed on gestational day 21. Resorptions and pup birth weights were recorded. The pregnant LPS treated rats developed many features of human PE (e.g. hypertension, proteinuria, liver and kidney dysfunctions). The mean concentration of Mg(2+) in the magnesium sulfate therapy group (0.86±0.24mmol/L) was significantly higher (p<0.05) than in both the control PE model group (0.61±0.12mmol/L) and the NP group (0.62±0.09mmol/L). The magnesium sulfate therapy group had a significantly (p<0.05) increased latency period (21.7±8.9min) to evoke a full motor seizure compared to both the NP group (4.8±2.2min)and the control PE model group (3.3±1.4min), there being no significant difference (p>0.05) between the latency periods of the NP group and the control PE model group. Overall, the magnesium sulfate therapy regimen completely prevented seizure activity in 3/8 (37.5%) of the treated PE model rats compared to 6/6 (100%) of the NP rats and 7/7 (100%) of the control PE rats. The treated PE model group also had significantly (p<0.05) reduced seizure duration (26±4s) compared to both the NP (40±7s) and the control PE model (45±9s) groups. As well, there was a significantly (p<0.05) shorter EEG seizure amplitude change in the treated PE model group (58±6μv). In this rat preeclamsia/eclampsia model, the anticonvulsant characteristics of magnesium sulfate have been shown to include significantly increasing seizure latency period, reducing seizure duration and decreasing seizure EEG amplitude.

The Effect of Intravenous Magnesium Sulfate on Acute Postoperative Bleeding in Elective Coronary Artery Bypass Surgery

Postoperative blood drainage is a great concern for health care providers when monitoring patients after cardiac surgery. In this study, the effect of intravenous magnesium sulfate infusion on postoperative bleeding in patients undergoing elective coronary artery bypass graft (CABG) surgeries was assessed. In a double-blind, randomized placebo-controlled clinical trial, 140 patients scheduled for elective CABG were randomly assigned into two groups; one group receiving intravenous magnesium sulfate and one receiving placebo. All the cases were similar regarding anesthesia and surgery. The magnesium group had less postoperative bleeding (465 ± 130 mL vs 680 ± 190 mL in the placebo group; P=.00) and less packed cell use (2.1 ± 0.6 packs vs 3.2 ± 0.8 packs in the placebo group; P < .05) as compared with placebo. The results demonstrated significantly less postoperative bleeding and packed cell use in the group receiving intravenous magnesium sulfate infusion during elective CABG surgery.

491: Effect of intravenous magnesium sulfate on markers of oxidative stress in women with preelclampsia

Lipid markers of oxidative stress have found to be increased in patients with preeclampsia. Little is known concerning the effects of intravenous magnesium sulfate on markers of oxidative stress in patients with preeclampsia. We investigated the potential ameliorative effects of intravenous magnesium sulfate in preeclampsia by measuring its effects on 8-isoprostane and TBARS, both markers of oxidative stress.

490: Effect of intravenous magnesium sulfate on free intracellular calcium and magnesium measured in peripheral blood monocytes of women with preeclampsia

AND MAGNESIUM MEASURED IN PERIPHERAL BLOOD MONOCYTES OF WOMEN WITH PREECLAMPSIA JAY BRINGMAN, CHARLES GIBBS, ROBERT AHOKAS, RISA RAMSEY, SYAMAL BHATTACHARYA, ROBERT EGERMAN, University of Tennessee Health Science Center, Obstetrics and Gynecology, Memphis, Tennessee, University of Tennessee Health Science Center, Memphis, Obstetrics and Gynecology, Memphis, Tennessee, University of Tennessee, Obstetrics and Gynecology, Memphis, Tennessee, University of Tennessee Health Science Center, Memphis, General Surgery, Memphis, Tennessee, University of Tennessee Health Science Center, Department of Obstetrics and Gynecology and Internal Medicine, Memphis, Tennessee OBJECTIVE: Intracellular calcium and magnesium are responsible for many cellular functions, including vascular tone and arterial blood flow as calcium channels are known to be magnesium-dependent. We investigated the potential ameliorative effects of magnesium sulfate in preeclampsia by measuring its effect on intracellular free calcium and magnesium in peripheral blood mononuclear cells (PBMCs) as a surrogate of maternal smooth muscle. STUDY DESIGN: After informed consent was obtained, peripheral blood was obtained before and after magnesium sulfate administration to preeclamptic gravidas. Patients were determined to have preeclampsia by ACOG criteria. After Histopaque isolation of PBMCs, intracellular free calcium and magnesium levels were measured ratiometrically using the fluorescent molecular probes Fura-2 and mag Fura-2, respectively. RESULTS: Six patients were included in the study. Intravenous magnesium sulfate resulted in a significant decrease in free intracellular calcium and a significant increase in free intracellular magnesium levels in PBMCs (p 0.0313, p 0.0126, respectively). CONCLUSION: Magnesium sulfate infusion resulted in a lowering of free intracellular calcium and an elevation in free intracellular magnesium levels in PBMCs. Some of the ameliorative effects of intravenous magnesium sulfate may be produced by alterations in intracellular ionic calcium as either a direct effect on contractile proteins or as a secondary messenger for additional processes.

Differential Effects of Intravenous Magnesium on Atrioventricular Node Conduction in Supraventricular Tachycardia

Evidence from noninvasive studies suggests magnesium has a differential effect on atrioventricular nodal (AVN) pathways. To further explore the electrophysiologic effects of intravenous magnesium sulfate (MgSO(4)) on supraventricular tachycardia, with particular reference to AVN conduction pathways, we studied 23 patients with supraventricular tachycardia at the time of electrophysiologic study. Tachycardia cycle length; AH, HV, and VA intervals; anterograde and retrograde Wenckebach thresholds; slow and fast pathway effective refractory periods (ERPs); accessory pathway ERP; right atrial and ventricular ERPs; blood pressure; and serum magnesium were evaluated before and after administration of MgSO(4) during sustained tachycardia. AVN reentry was induced in 14 patients and atrioventricular reentry was induced in 9; 1 of the latter had dual AVN physiology with tachycardia using the slow pathway. Serum magnesium level increased from 0.88 +/- 0.11 to 1.79 +/- 0.14 mmol/L (p <0.0001). Magnesium increased tachycardia cycle length to a greater extent in those with dual AVN physiology than those without: 340 +/- 54 to 370 +/- 57 ms versus 347 +/- 29 to 350 +/- 30 ms (p = 0.01). This was associated with greater increase in AH interval in those with dual AVN physiology than in those without: 241 +/- 59 to 270 +/- 60 ms versus 144 +/- 16 to 140 +/- 20 ms (p = 0.003). Presence of dual AVN physiology was more frequently associated with reversion to sinus rhythm: 5 of 15 versus 0 of 8 (p = 0.06). MgSO(4) did not alter other measured parameters. In conclusion, magnesium increases tachycardia cycle length and AH interval in patients with dual AVN physiology through a dominant effect on the slow AVN pathway.