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Summer '14 Pharm III > MH Dantrolene > Flashcards

MH Dantrolene Flashcards

1
Q

Temp regulation centers

A

Hypothalamus-
Gain center-posterior
Loss center-anterior

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2
Q

1 degree change in temp will alter BMR by

A

7%

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3
Q

Most heat loss is by

A

Radiation (40%)
Convection (30%)
Burn pts lose most via evaporation

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4
Q

Hypothermia phys changes

A

Increase SVR, decrease CO, myocardial depression, increases blood viscosity, Left shift, impaired coags, decrease CO2 production, decrease O2 consumption

Shivering increase cardiac work, O2 consumption

Drug elimination slowed

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5
Q

MH signs and symptoms

A 
Hypercarbia
Tachycardia/pnea
Hyperthermia (1-2c q5min)
HTN
Dysrhythmias
Acidosis
Skeletal muscle rigidity (Masseter muscle spasm after succs in children CPK >20,000 confirms)
Myoglobinuria
Hypoxia
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6
Q

MH incidence, genetics

A

1 in 15,000 anesthetics in children
1 in 50,000 anesthetics in adults
Dominant pattern of inheritance

Ryanodine receptor mutation found in 50% of MH families and 20% of all MH patients

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7
Q

Triggers

A

Full episodes- Halothane, Enflurane, Isoflurane, Desflurane, Sevoflurane, Succinylcholine

MIld episodes- Exercise in hot conditions, neuroleptic drugs, ETOH, infection

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8
Q

MH patho

A

Increased myoplasmic Ca+

Muscle spasms–> rhabdomyolysis

Heat production–>fever–> hypermetabolism

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9
Q

MH clinical features

A

Skeletal muscle involvement
SNS hyperactivity
Hypercapnia
Hyperthermia

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10
Q

Masseter muscle rigidity

A

May be normal sign after succs, but- if sustained immediately check a K+ and blood gas. Clinical MH occurs about 20% of the time after this.

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11
Q

Skeletal muscle in MH

A

Pain
Myoglobinuria
Cardiac arrhythmias

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12
Q

CPK in MH

A

> 20,000

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13
Q

What is the main concern with rapid rhabdomyolysis in MH

A

Rapid increase in K+

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14
Q

SNS hyperactivity

A

Tachy, acidosis, ATP depletion, hypoxemia, heat production, hyperventilation, CV instability

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15
Q

Labs

A

Get an A-line

Decreased PaO2, increased PaCO2
High lactate and low pH

CPK very high, up to 100,000
Elevation correlates best with rhabdomyolysis, less well with fever and acidosis
Resting CK mildly increased

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16
Q

MMR

A

Continue with agents that will not trigger MH or postpone elective surgery

Unless MH manifests, dantrolene is not recommended

Pts should be closely observed for 24 hours for signs of MH

Discuss muscle biopsy with MH expert

17
Q

MH testing

A

Halothane contracture test- gold standard

Caffeine contracture test- not reliable, many false positives

18
Q

MH treatment

A

Must be identified early

Call for Help/MH cart

Stop all volatile agents and succs, change circuit/soda lime, change to new machine if possible

Hyperventilation on 100% O2

Dantrolene 2.5mg/kg bolus followed by 2mg/kg IV q5 minutes to a total of 10mg/kg

Bicarb for acidosis

Monitor temp, aggressively cool to under 38C

Maintain 2ml/kg/hr UO with fluids, lasix

19
Q

Tx for dysrhythmias and hyperkalemia in MH

A

No Ca channel blockers

Other standard antiarrhythmics ok (Procainamide 15mg/kg IV)

Correction of hyperkalemia and acidosis correct most problems. Hyperventilation, dantrolene, and bicarb may be sufficient.

Treat hyperkalemia with glucose, insulin, and calcium

20
Q

MH care once initial episode is controlled

A

ICU for 36 hours (25% recrudescence rate)
Continue dantrolene for at least 24 hours, 1mg/kg q6 hrs

No K+ fluids, avoid LR
Follow coags as DIC may occur

Measure CK q6h until normal after pt has improved/stabilized
CK may remain elevated for 2 weeks

21
Q

MH cart drugs

A

36 vials of dantrolene, 20mg each with 60ml sterile water for each vial (1000ml x 2)
8.4% bicarb 50ml x 5
Lasix 40mg/amp x 4 amps
D50 50ml vials x 2
CaCl 10% 20ml vial x 2
Regular insulin 100units/ml x 1 (must be refrigerated)
Lidocaine HCl 2% 1 box = 2 grams or 10ml/100mg preloaded vial

22
Q

MH cart equipment

A

Syringes 60ml x 5 to dilute dantrolene
Mini-spike IV additive pins x 2 and multi-ad fluid transfer sets x2 (to reconstitute dantrolene)
Angiocaths 20g-2inch, 22g-1inch, 24g-3/4inch (4 each)
D5W 250ml x1, Microdrip IV set x 1
NG tubes
Irrigation tray with piston syringe x 1
Toomy irrigation syringes 60ml x 2

23
Q

MH monitoring

A

Core temp probes

CVP kits

A-line/CVP transducers

24
Q

Additional MH stuff

A 
Large sterile drap
Three-way irrigating foley
Urinometer 
Rectal tubes
Plastic bags for ice, large and small
Bucket for ice
25
Q

MH lab supplies

A

6 abg kits
CK myoglobine, SMA 19 (LDH, e-lytes, thyroid), PT/PTT, fibrinogen, fibrin split products, CBC, lactic acid (2 adult, 2 peds)

Urine cup x 2 myoglobin
Urine dipstick hemoglobin

26
Q

Dantrolene MOA

A

Reduces muscle tone and metabolism- prevents Ca release from sarcoplasmic reticulum. Restores Ca balance.

10-15h half-life

27
Q

Does dantrolene potentiate NDMR? Interfere with reversal?

A

No. No.

Do make sure muscle strength has returned prior to extubation.

28
Q

Dantrolene cautions

A

Significant muscle weakness in those with muscle diseases

Phlebitis is common

Ca channel blockers and dantrolene may produce life-threatening hyperkalemia and myocardial depression

Oral dantrolene may be used for several days after the acute phase has been controlled

29
Q

Who needs to have dantrolene stocked? How much?

A

Any place administering MH triggering agents must have a minimum of 36 vials of dantrolene at all times

Must be kept close to the OR and sterile water must be available for mixing

30
Q

Testing

A

11 North American centers

Muscle biopsy with halothane test is highly sensitive

30 mutations identified, but 50% of MH pts have no such mutations

31
Q

Machine prep for pt with MH

A

Remove vaporizers

Change absorbent

10L/m flow O2 for at least 20 minutes, change all circuit components at this time

Charcoal filter

32
Q

Management of known MH pt

A

No triggering agents

Dantrolene pretreatment not recommended

Treatment plan should be available, reviewed

Minimum 4 hr observations suggested

Can still be discharged same day if anesthetic is uneventful

33
Q

Diseases associated with MH

A

Central core disease, muscular dystrophy, Na channel forms of myotonia

34
Q

Diseases that mimic MH

A

Neuroleptic malignant syndrome- muscle rigidity, fever, autonomic instability, cognitive changes, such as delirium, and CPK increases.

Pts are on antipsychotics- haldol, prolixin, thorazine

35
Q

Succs in children

A

Best avoided

Only for emergencies, special situations

Sudden hyperkalemic cardiac arrest in pts with undiagnosed myopathies- young males, 40 cases since 1990, 50% mortality

36
Q

Tx for sudden unexpected cardiac arrest

A

CaCl
Bicarb
Insulin/Glucose
Hyperventilation

May require dialysis and CPB

Hyperkalemia treatment is key to good pt outcome, even with prolonged resuscitation effort

DON’T use succs in kids unless you have a really good reason!

Summer '14 Pharm III (7 decks)

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