MH and Dantrolene Flashcards
dantrolene
Side effects
Significant muscle weakness
- can last long → ICU for 36h
Phlebitis - especially through peripheral IV
- watch it
MH monitor equipment
- Esophageal or other core temperature probes
- CVP kits: size appropriate to patient population
- Transducer kits for arterial & central venous cannulation
Drugs needed in the MH cart/kit
- Dantrolene 36 vials
- Sterile water to reconstitute dantrolene: 1,000 ml x 2
- Sodium bicarbonate (8.4%): 50 ml x 5
- Furosemide: 40 mg/amp x 4 ampules
- D50: 50 ml vials x 2
- CaCl (10%): 20 ml vial x 2
- Regular insulin: 100 units/ml x 1 (refrigerated)
- Lidocaine HCl (2%): 1 box = 2 grams or 10 ml/100 mg preloaded vial
For each 1 degree fahrenheit change, basal metabolic rate will change how much?
7%
Pre-treatement with Dantrolene
Prophylaxis treatment is not recommended
MH kit - other supplies needed
- Large sterile Steri-Drape (for rapid drape of wound) – you may need to start CPR
- Three-way irrigating foley catheters → size appropriate for patient population
- Urine meter x 1
- Irrigation tray with piston syringe
- Rectal tubes [Sizes (Malecot Drain) 14F, 16F, 32F, 34F]
- Large clear plastic bags for ice x 4
- Small plastic bags for ice x 4
- Bucket for ice
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
Dantrolene
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)
What other conditions might look like MH?
Neuroleptic Malignant Syndrome
Light Anesthesia
Pain
Thyroid storm (Hyperthyroid)
Pheochromocytoma (esp if doing a bowel resection)
occult myopathy
Evaporation
- In a liquid the particles have a range of energies.
- At the surface of the liquid some particles will have enough energy to escape from the liquid and overcome the attraction of the other liquid particles.
- This leaves the less energetic particles still in the liquid and so the liquid is cooler.
H2O is transferred from the surface to the atmosphere, the process by which water changes from a liquid to a gas
Radiation
Electromagnetic waves that directly transport ENERGY through space
50% of heat loss
how much Dantrolene should you have in the cart
36 vials (720 mg) sufficient for a 70-kg person
each vial = 20 mg
Needed if succinylcholine is available for resuscitation even if it’s a facility in which volatile anesthetics are not used
What are triggers of MH?
- Inhalational agents (probably excluding nitrous oxide)
- Succinylcholine
- Mild MH triggers:
- exercise in hot conditions,
- neuroleptic drugs (haldol, dopamine),
- alcohol
- infections
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<strong>++</strong> release
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 ↑
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 muscle diseases are definitely associated with MH (predispose MH reactions)
- Central core disease
- King-Denborough syndrome
- Evan’s myopathy
Direct association with muscle dystrophy is not likely
- however, can still develop rhabdomylosis & hyperkalemia without hypermetabolic issues so avoid triggering agents anyway
Conduction
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
How does someone get tested for MH?
1 gram of muscle is tested with the halothane -caffeine contracture test
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
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
hyperkalemia
MH - laryngospasm treatment
rocuronium
positive pressure
propofol