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
- give lidocaine or procainamide 15mg/kg IV (NOT CCB)
- 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
- 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
What are triggers of MH?
Inhalational agents (probably excluding nitrous oxide)
Mild MH triggers: exercise in hot conditions, neuroleptic drugs (haldol, dopamine), alcohol, infections
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
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
- Cutaneous vasodilatation
- ↑ circulating catecholamines
- ↑ HR, ↑ SVR, ↑ CO
- Cutaneous vasoconstriction
- 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?
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
During episode - Very high, up to 100,000
May be elevated up to 2 weeks after the event
- 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?
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
Redosing Q 6hrs
What is the presentation of occult myopathy in young males having surgery?
Sudden cardiac arrest, especially soon after use of sux,
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
Dialysis & cardiopulmonary bypass may be required
Neuroleptic malignant syndrome presentation?
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
- 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
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 ↑