Magnesium and anesthesia

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Magnesium and anesthesia




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Presentations text content in Magnesium and anesthesia

Slide1

Magnesium and anesthesia

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

Slide2

Basic physiology

Slide3

Fourth common but second inside cell

Na

K

Cl

Then Mg

.

If we look

intracellularly

, it is the second most common

cation

after potassium.

Slide4

How it is present ??

99 % - intracellular

Muscle , soft tissues

,

Bone

RBCs

1% extracellular

Slide5

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 ??

Slide6

Hypomagnesemia – causes

Slide7

Hypomagnesemia – clinical features

Hypertension

Angina

Arrhythmias

Convulsions

Coma , associated hypokalemia

Neuromuscular disturbance

Psychiatric

Slide8

Replacement

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

Slide9

Magnesium toxicity

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

Slide10

Physiological role

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

Slide11

Magnesium awareness

Inhospital

patients – 10 % Mg deficient

hypokalemia and

hypophosphatemia

40 % Mg deficient

Also related to sodium and calcium deficiency

Slide12

Hypocalcemia

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

Slide13

Obstetrics

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.

Slide14

Tocolysis

Ritodrine

Magsulf

Nifedipine

But

neuroprotective

and decreased CP incidence in MgSO4 treated preterm mothers

Slide15

Magnesium and cardiology

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

Slide16

Cardiopulmonary bypass

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

Slide17

Cardiology

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

Slide18

Premedication

Other electrolyte disturbances

Look for Mg

Problems , correct and take up

Beware

myaesthenia

and muscle dystrophies

Slide19

Neuromuscular blockade

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

Slide20

Analgesia and anaesthesia

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

hippocampal

presynaptic

calcium channels

that regulate neurotransmitter release in the central nervous system has been suggested.

(

isoflurane

– site of action)

Slide21

Anaesthesia – implications

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

Slide22

Other implications of magnesium disorders

Slide23

Anaesthesia – implications

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)

Slide24

Regional anaesthesia

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.

Slide25

Acta Anaesthesiologica Scandinavica 11/2005; 49(10):1514-9.

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.

Slide26

Intra op muscle relaxant requirement and post op pain ??

Slide27

Various studies

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

Slide28

BP of 80

and maintain

Slide29

Magnesium sulphate as a technique of hypotensive anaesthesia

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

Slide30

Possible role of magnesium

RLS

Dementia

Chronic fatigue syndrome

Magnesium reduces spasms and autonomic instability in tetanus.

Beware of side effects

Slide31

Possible role of magnesium

Traumatic brain injury

Spinal cord injury

Carotid surgery

Subarachnoid

haemorhage

Slide32

Magnesium and sports medicine

Increased duration

Enhance membrane function

Efficiency better

Slide33

severe asthma

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

Slide34

In Pheo, use a and b blockers but Mg !!

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.

Slide35

Role in Intensive Care Unit:

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

Slide36

The essence in dosage

Slide37

The essence in dosage

Slide38

Summary

Magnesium – normal level – physiology

Admitted patients ??

OBG, Cardio, Asthma, tetanus, analgesia

anaesthesia

, regional, ICU ,

neuro

,

pheo

, shivering

Dosage

Hypo and hyper

Slide39

Thank you all


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