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Flashcards in MH and Dantrolene Deck (53)
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MH incidence?

1:8,000 to 1:50,000 adults (depending on the source cited)

Higher in children


Sequence of events the second you realize your patient has MH

Call for help

get MH cart

D/C volatile agent, sux

Change circuit and soda, use highest flow possible of O2 through the machine or ideally change to new dedicated MH safe machine

hyperventilate 100% oxygen and switch to TIVA


Tx acidosis with sodium bicarb

  • Monitor with capnography & q 15 minute ABG

Monitor core temperature & Cooling to 38°C

Maintain urine output with diuretics and fluids (NOT LR) 

  • U/O >2 ml/kg/hr 

Tx dysrhythmias

  • give lidocaine or procainamide 15mg/kg IV (NOT CCB)

Tx hyperkalemia

  • 1mL/kg D50 glucose and 0.15 units/kg regular insulin
  • calcium chloride 5-10 mg/kg IV

Continue dantrolene sodium for at least 72 hours after control of episode (≈1 mg/kg q 6 hours)


Drugs needed in the MH cart/kit

  1. Dantrolene 36 vials
  2. Sterile water to reconstitute dantrolene: 1,000 ml x 2
  3. Sodium bicarbonate (8.4%): 50 ml x 5
  4. Furosemide: 40 mg/amp x 4 ampules
  5. D50: 50 ml vials x 2
  6. CaCl (10%): 20 ml vial x 2
  7. Regular insulin: 100 units/ml x 1  (refrigerated)
  8. Lidocaine HCl (2%): 1 box = 2 grams or 10 ml/100 mg preloaded vial


What are triggers of MH?

Inhalational agents (probably excluding nitrous oxide)


Mild MH triggers: exercise in hot conditions, neuroleptic drugs (haldol, dopamine), alcohol, infections


Dantrolene dose?

Bolus 2.5 mg/kg

Then maintenance dose 2 mg/kg IV q5min up to 10 mg/kg

Then 1 mg/kg q6h for 72h

Each vial of dantrole contains 20 mg dantrolene and 3g mannitol; needs to be diluted with 60 mL sterile water


How does basal metabolic rate (oxidative metabolic consumption) chnage in regards to change in °C?

1°C = 11.2% change in BMR


MH - laryngospasm treatment


positive pressure



what sould Dantrolene be mixed with?

Sterile water (without bacteriostatic agent) 


how does Succinylcholine trigger MH?

succinylcholine acts indirectly by activating the nicotinergic acetylcholine receptor (nAChR), a nonspecific cation channel, resulting in continuous local depolarization

The depolarization can trigger propagated action potentials and will further activate the dihydropyridine receptors (DHPR, CaV1.1)

this leads to the gating of both Ca++ release from the SR via RyR1 and L-type Ca++ current from the extracellular space


What area of the brain regulates temperature?


most improtant area for temp regulation

Gain center: posterior hypothalamus

Loss center: anterior hypothalamus


patient susceptible to MH - uneventful surgery

may be discharged on the day of surgery

Minimum of 4 hours observation is strongly suggested


MH Compensatory mechanisms

Heat loss

  • Sweating
  • Cutaneous vasodilatation

Sympathetic hyperactivity:

  • ↑ circulating catecholamines
  • ↑ HR, ↑ SVR, ↑ CO
  • Cutaneous vasoconstriction

↑ ventilation

  • as the CO2 increases,  minute ventilation goes up
  • may be masked by fentanyl 



Transfer of heat from one place to another by the actual movement of fluids (warmed matter, either liquids or gases)

Heat transfer in a gas or liquid by the circulation of currents from one region to another

30% heat loss


MH pathophysiology (generalized)?

It is a syndrome

a chain of clinical responses to muscle hypermetabolism ("decoupling"; ATP needed for Ca release)

issue with innapropriate Ca++ release



Electromagnetic waves that directly transport ENERGY through space

50% of heat loss


How does someone get MH?

Genetic susceptibility;

autosomal dominant RYR mutations are common in MH patients


How does dantrolene work?

Reduces muscle tone and metabolism

Prevents ongoing release of Ca++ from muscle (SR)

Blocks external entry of Ca++ into sarcoplasm

**Stabilizes calcium induced calcium release and stabilizes the negative feedback**


CPK levels in MH

↑ >20,000

During episode - Very high, up to 100,000


May be elevated up to 2 weeks after the event

Elevation correlates

  • Best with rhabdomyolysis
  • Less well with fever & acidosis


What lab tests do you want to get for someone having an MH episode?

ABG           CK            myoglobin        Electrolytes        thyroid 

LDH        PT/PTT         fibrinogen             FSP                 CBC

lactic acid                              Urine for myoglobin/hemoglobin


How does someone get tested for MH?

1 gram of muscle is tested with the halothane -caffeine contracture test


Myoglobinuria in MH

Myoglobin "leaked" from damaged cells → urine

may occur within a few hours

should be anticipated & treated to prevent acute tubular necrosis

  • Mannitol, diuresis, & ↑ fluids


You want the place you work to have how much dantrolene?

36 vials

Also lots of sterile water to mix with



Is the movement of thermal energy through a material without the particles in the material moving.

Transfer of energy through matter from particle to particle





E½t 10-15h

Redosing Q 6hrs 


What is the presentation of occult myopathy in young males having surgery?

Mimics MH

Sudden cardiac arrest, especially soon after use of sux,

muscle rigidity



how do inhalational agents trigger MH?

inhalational agents dirrectly on RYR1

they stimulate Ca++ release via RYR1


Occult Myopathy therapy

Therapy should be directed at treatment of hyperkalemia:

  • Calcium chloride
  • Bicarbonate
  • Insulin
  • Glucose
  • Hyperventilation
  • Dialysis & cardiopulmonary bypass may be required


Neuroleptic malignant syndrome presentation?

Mimics MH

Presents with muscle rigidity, fever (cardinal sign), autonomic instability, delirium & cognitive changes, elevated CPK

relieved by NMB (as opposed to MH)

pt population at risk: those on antipsychotics (haldol, prolixin, thorazine)


MH kit - other supplies needed 

  1. Large sterile Steri-Drape (for rapid drape of wound) – you may need to start CPR
  2. Three-way irrigating foley catheters → size appropriate for patient population
  3. Urine meter x 1
  4. Irrigation tray with piston syringe
  5. Rectal tubes [Sizes (Malecot Drain) 14F, 16F, 32F, 34F]
  6. Large clear plastic bags for ice x 4
  7. Small plastic bags for ice x 4
  8. Bucket for ice


Rapid rhabdomyolysis vs. slow rhabdomyolysis

Rapidly developing rhabdomyolysis includes rapid ↑ in  K+ → leading to dysrhythmias

Slowly developing rhabdomyolysis is safer → K+ is redistributed before blood levels can ↑