Magnesium and anesthesia

1. Dr. S. Parthasarathy MD., DA., DNB, MD (Acu), Dip. Diab.DCA, Dip. Software statistics PhD (physio) Mahatma gandhi medical college and research institute, puducherry, India Magnesium and anesthesia

2. Basic physiology

3. Na K Cl Then Mg . If we look intracellularly, it is the second most common cation after potassium. Fourth common but second inside cell

4. 99 % - intracellular Muscle , soft tissues, Bone RBCs 1% extracellular How it is present ??

5. Magnesium intake is 20-30 meq/day Kidneys elimination -- averages 6-12 meq/day. Plasma Mg is closely regulated between 0.7 to 1 mmol/litre Cereals and legumes but processing ??

6. Hypomagnesemia – causes

7. Hypertension Angina Arrhythmias Convulsions Coma , associated hypokalemia Neuromuscular disturbance Psychiatric Hypomagnesemia – clinical features

8. Normal homeostasis of Mg requires daily intake of 10-20 mmol Emergency- 10-20 mmol in 50 ml 5% D iv over 15-30mins, followed by 40 mmol over 4 hrs iv Replacement

9. Rare Mgso4 in renal dysfunction !! In PIH cases Nausea and vomiting Skeletal muscle weakness CNS depression Coma and death 2.5 to 5 m mol of calcium IV , fluid and diuresis , Mg free dialysis in CRF Magnesium toxicity

10. The physiological role of Mg is due to its calcium channel blocking properties at smooth muscle, skeletal muscle and conduction system levels. analgesic properties -- NMDA antagonism . Involvement of Mg in Na K ATPase cofactor in many enzyme pathways. Decrease catecholamine release Physiological role

11. Inhospital patients – 10 % Mg deficient hypokalemia and hypophosphatemia 40 % Mg deficient Also related to sodium and calcium deficiency Magnesium awareness

12. Hypocalcemia Associated hypomagnesemia Stimulates PTH Calcium mobilisation to correct If we give Mg it corrects both !!

13. PIH and eclampsia Problems : cerebral vasospasm and sensitivity to pressors MgSo4 – cerebral vasodilator and decreased sensitivity to catecholamines 4 gm IV followed by 1 gm/hour – Mg conc – 2-4 mmol/l Uteroplacental flow better , SVR decrease with better cardiac output. Obstetrics

14. Ritodrine Magsulf Nifedipine√ But neuroprotective and decreased CP incidence in MgSO4 treated preterm mothers Tocolysis

15. Attenuate sympathoadrenal response for intubation especially in preeclampsia !! IV 40 mg / kg Early magnesium correction in AMI decreases LVF and arrhythmias Magnesium has a role in the treatment of PPHN patients who do not respond to hyperventilation Magnesium and cardiology

16. The CABG with extracorporeal circulation resulted in a significant decrease in blood Mg concentration Component of some cardioplegic solutions- protects ischemic myocardium especially during reperfusion Cardiopulmonary bypass

17. Magnesium is effective at abolishing tachyarrythmias and is recommended for torsade de pointes, digoxin-induced and ventricular arrhythmias unresponsive to other treatment. A bolus of magnesium, 2g over 10 minutes should be given Cardiology

18. Other electrolyte disturbances Look for Mg Problems , correct and take up Beware myaesthenia and muscle dystrophies Premedication

19. Decreased twitch – no fade TOF Judicious use of NDP s inhibition of calcium-mediated release of acetylcholine from the presynaptic nerve terminal at the neuromuscular junction plays an important role. Use NMJ monitors Magnesium is an attractive anti-shivering agent Neuromuscular blockade

20. Magnesium is a calcium channel blocker and noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist with antinociceptive effects Large studies – postop pain relief – controversial Anaesthesia Enhancing effects of magnesium unknown. Competitive antagonism on hippocampalpresynapticcalcium channels that regulate neurotransmitter release in the central nervous system has been suggested. ( isoflurane – site of action) Analgesia and anaesthesia

21. High chances of stridor provoked by airway stimulation, upon induction of hypomagnesemic patients Avoid hyperventilation, as it further lowers Mg levels Vasodilation produced by volatile agents, narcotics may be exacerbated by Mg leading to hypotension Anaesthesia – implications

22. Other implications of magnesium disorders

23. Intra articular inj of MgSO4 enhances analgesic effect of intra articular Bupivacaine- Anaesth Analg 2008;106 MgSo4 attenuates arterial pressure increase during lap cholecystectomy - BJA (2009)103(4) Anaesthesia – implications

24. magnesium as an adjunct to lidocaine improves the quality of anaesthesia and analgesia in IVRA Epidural Co-administration of magnesium 50 mg for postoperative epidural analgesia results in a reduction in fentanyl consumption without any side-effects. Blocks Adding magnesium to levobupivacaine for axillary brachial plexus block in arteriovenous fistulae surgery. Regional anaesthesia

25. Intrathecal In patients undergoing lower extremity surgery, the addition of IT magnesium sulphate (50 mg) to bupi + fent spinal anaesthesia delayed the onset of both sensory and motor blockade, prolonged the period of anaesthesia without additional side-effects. ActaAnaesthesiologicaScandinavica11/2005; 49(10):1514-9.

26. Intra op muscle relaxant requirement and post op pain ??

27. I.V. magnesium sulphate during TIVA reduced rocuronium requirement and improved the quality of postoperative analgesia in O and G cases I.V. magnesium sulphate reduces the total anesthetic requirements, post-operative pain score and post-operative analgesic requirements in neuro surgery cases Various studies

28. BP of 80 and maintain

29. continuous infusion of magnesium sulphate led to a useful reduction in MAP, heart rate, blood loss and duration of surgery. Take care of relaxants and anesthetic doses Magnesium sulphate as a technique of hypotensiveanaesthesia

30. RLS Dementia Chronic fatigue syndrome Magnesium reduces spasms and autonomic instability in tetanus. Beware of side effects Possible role of magnesium

31. Traumatic brain injury Spinal cord injury Carotid surgery Subarachnoid haemorhage Possible role of magnesium

32. Increased duration Enhance membrane function Efficiency better Magnesium and sports medicine

33. routine use of intravenous magnesium in all asthmatic patients ?? appears beneficial in patients presenting with acute severe asthma. nebulized MgSO4 (95–385 mg or 250–280 mmol) to standard bronchodilator therapy -- controversial severe asthma

34. successful use of magnesium during pheochromocytoma crisis In a 5-yr-old boy undergoing laparoscopic tumor resection, intraoperative hemodynamic stability was successfully achieved with a loading dose of 40 mg/kg, followed by continuous infusion of 15–30 mg kg / h of MgSO4. In Pheo, use a and b blockers but Mg !!

35. Magnesium (Mg) deficiency commonly occurs in critical illness and correlates with a higher mortality and worse clinical outcome in the intensive care unit Hypo – poor prognosis in ventilated patients Role in Intensive Care Unit:

36. The essence in dosage

37. The essence in dosage

38. Magnesium – normal level – physiology Admitted patients ?? OBG, Cardio, Asthma, tetanus, analgesia anaesthesia , regional, ICU , neuro ,pheo, shivering Dosage Hypo and hyper Summary

39. Thank you all