Bb Malignant Hyperthermia

Front 1

What is the cause of NMS?

Back 1

chronic administration of psychoactive drugs
1. butyrophenones
2. phenothiazines
3. MAOI
4. lithium

Front 2

What are symptoms of NMS?

Back 2

1. rhabdo,
2. ARF,
3. impaired motor fxn (generalized rigidity),
4. mental status deterioration leading to coma,
6. delirium,
7. hyperpyrexia,
8. autonomic instability - labile BP, inc HR, inc RR
9. respiratory failure,
10. mortality of 15%

Front 3

What is the difference between NMS and MH?

Back 3

-MH is defect in skeletal muscle metabolism, has a genetic basis,
-NMBDs are able to produce flaccid paralysis in NMS but not MH

Front 4

Is MH susceptibility present in patients with NMS?

Back 4

probably not, can use SCh

Front 5

What is the therapy for NMS?

Back 5

no completely effective therapy,
-bromocriptine (dopamine agonist) can be used,
-dantrolene has also been effective

Front 6

What is the basic underlying problem in MH?

Back 6

SR loses it's ability to bind or reuptake calcium
-there is an intracellular buildup of Ca which leads to heat production, O2 consumption, and activation of contractile elements

Front 7

How does dantrolene work in MH?

Back 7

decreases the release of Ca from the SR

Front 8

How does MH work on the SR?

Back 8

leads to disruption of the ATPase in the SR, resulting in consumption of available energy resources and acidemia which is the hallmark of the condition

Front 9

What drugs are unsafe in MH susceptable pts?

Back 9

decamethonium, SCh, volatiles (not nitrous)

Front 10

Why should you not give verapamil to a patient being treated for MH?

Back 10

has been shown to depress cardiac function when given with dantrolene

Front 11

How should you give dantrolene for treatment of MH?

Back 11

-bolus 2.5mg/kg IV
-repeat every 5min until symptoms abate or a max of 10-20mg/kg is reached
-then 24 hours of 10mg/kg/day should be given

Front 12

What is troponin and what is tropomyosin?

Back 12

-troponin - inhibitory protein that binds to actin (thin filaments) in the resting state (calcium binds to troponin and inhibits the inhibition);
-tropomyosin - inhibitory protein that binds to myosin (thick filaments) in the resting state

Front 13

how do nondepolarizers affect the muscle rigidity of MH?

Back 13

they don't

Front 14

When in relation to the trigger does MH occur?

Back 14

either acute or delayed
-if delayed may not occur until the patient is in recovery

Front 15

When giving SCh what should raise your suspicion to the possibility of MH? Why? What else?

Back 15

trismus signals the onset of MH about 50% of the time,
-also failure to achieve muscle relaxation

Front 16

CPK levels of what postop signal MH?

Back 16

>20,000

Front 17

If a patient develops masseter spasm during or after a MH triggering anesthetic what should you do? What should you check?

Back 17

Should mandate conversion to a non-triggering anesthetic
-Other signs of MH should be present before anesthesia and surgery are stopped.
-serum creatinine kinase levels should be followed for 24 hrs after an episode of masseter spasm bc an elevation may indicate an underlying myopathy

Front 18

What are the earliest signs of MH?

Back 18

hypercarbia > tachycardia

Front 19

What are signs of MH?

Back 19

1. tachycardia,
2. tachypnea,
3. rigidity,
4. hypercarbia
5. hypoxemia
6. acidosis
7. cyanosis
8. hyperthermia,
9. arrhythmias,
10. hyperkalemia

Front 20

What are complications from MH?

Back 20

1. death from cardiac arrest,
2. death from cerebral or pulmonary edema,
3. renal failure,
4. DIC

Front 21

What is the differential diagnosis of MH?

Back 21

1. sepsis,
2. pheochromocytoma,
3. thyroid storm,
4. NMS

Front 22

How is dantrolene prepared?

Back 22

must be dissolved in sterile water (20mg vial with 60cc sterile water)

Front 23

What is the half life of dantrolene and what are the routes through which it can be given?

Back 23

T1/2 = 12 hrs,
-highly lipid solube and comes in PO and IV forms

Front 24

What is the treatment for MH?

Back 24

1. stop anesthesia and surgery,
2. hyperventilate with 100% O2,
3. dantrolene - 2.5 mg/kg Q 5min to 10 mg/kg
4. treat hyperthermia - institute cooling
5. treat hyperkalemia (insulin 10 units/glucose 50cc D50)
6. treat acidosis - bicarbonate 2-4 meq/kg
7. treat arrhythmias - Lidocaine 1-4 mg/kg slow IV push
8. place foley, arterial, and central lines

Front 25

What is the gold standard for evaluating patients possibly susceptible to MH?

Back 25

halothane contracture test,
-varying doses of halothane and caffeine and measuring muscle tension
-caffeine causes a muscle sample to contract when halothane is added muscle contraction is greater
-perform on a fresh sample of muscle

Front 26

What conditions were once thought to be more prevalent in MH pts, but were found to be no more than the general population?

Back 26

1. strabismus,
2. hernia,
3. kyphoscoliosis,
4. muscle cramps
5. muscle weakness

Front 27

What is the best indicator of MH risk?

Back 27

hx of MH episode in patient or relative

Front 28

How does pretreatment with dantrolene affect the occurence of MH?

Back 28

masks the early signs but doesn't prevent the actual event

Front 29

When should you do a muscle biopsy?

Back 29

history of masseter spasm or questionable MH (if for sure MH no reason to do the biopsy)

Front 30

When do you do a MH test in a child with a distant relative with MH?

Back 30

test the child's parent then only if the childs parent is positive do you test the child

Front 31

What size should a child be to test for MH?

Back 31

20kg minimum is recommended to avoid injury to the muscle group

Front 32

When is an optimal CPK test done?

Back 32

patient fasting and resting (no exercise for 1-2 days)

Front 33

Why should you not do the halothane contracture test in patients with NMS?

Back 33

patients with NMS can have an abnormal response to halothane

Front 34

Other than drugs, what are other possible triggers of MH?

Back 34

1. stress
2. high environmental temp
3. muscle trauma
4. exercise

Front 35

What may be useful for arrhythmias in MH?

Back 35

BBs or Lidocaine, but verapamil should be avoided

Front 36

What is the best tx for rhabdo that occurs with MH?

Back 36

Aggressive hydration with forced diuresis and urine alkanization

Front 37

What is the sarcotubular system?

Back 37

It is made of the T system and the sarcoplasmic reticulum and surrounds each muscle fiber
-the T system rapidly transmits an action potential to fibrils

Front 38

Explain the physiology of MH.

Back 38

- During contraction there is "sliding" between actin and mysosin as they break and reform cross linkages
- the action potential is transmitted to the fibrils via the T system and this triggers the release of Ca from the SR
- Ca initiates excitation contraction coupling - muscle contraction
- Ca inhibits the inhibition - it binds to troponin; in resting muscle, troponin is tightly bound to actin. Ca inhibits this binding and as the union is weakened, tropomyosin is then able to move laterally and actin comes into contact with myosin, ATP is split, and muscle contraction occurs
-Shortly after releasing Ca, the SR begins to reaccumulate and store released Ca in its cisterns by active transport (ATP is involved again) - when intracellular Ca falls sufficiently, contraction of muscle ceases
- If the SR can't reuptake Ca, muscle contraction continues and is sustained - referred to as contracture

Front 39

If symptoms of MH appear, what must you immediately do?

Back 39

Obtain an ABG and switch to a nontriggering anesthetic

Front 40

What is Dantrolene? How does it work?

Back 40

It is a hydantoin developed as a muscle relaxant
-it inhibits transmembrane Ca flux and excitation contraction coupling
-ie it decreases the release of Ca from the sarcoplasmic reticulum

Front 41

Management of MH susceptible or high risk pts.

Back 41

1. heightened awareness and readiness
2. non-triggering anesthetic techniques

Front 42

What neurotransmitter system does NMS involve?

Back 42

The dopaminergic system and has been associated with the withdrawal of L-Dopa