1
Q
malignant hyperthermia:
- what is it?
- what happens?
- incidence (adults and children)?
- most prevalant in what country (race)?
- what age and or gender is most affected?
A
- inherited skeletal muscle disorder triggered by anesthetics and depolarizing MRs
- trigger sustained skeletal muscle hypermetabolism or contracture characterized by fever, tachycardia, hypercarbia and rigidity
- 1: 15,000 in childern and 1:50,000 in adults
- can happen in any race but most prevalent in north america (french canadians)
- children and men
2
Q
what is the number for M-haus?
A
1-800-MHhyper
5
Q
- MH?
- what chromosome has the MH defect?
- what is the test for it?
A
- abnormalities of calcium release at ryanodine receptor (RYR1:a major calcium release channel of the sarcoplasmic reticulum) of skeletal muscle
- located on chromosone 19; 25% of families in north america the variant RYR1 gene.
- caffiene/halothane test on muscle plug
6
Q
- what happens on a cellular level with actin/myosin and calcium release in a normal cell?
- what happens in MH?
A
- depolarization releases calcium from sarcoplasmic reticulum, this activates the crossbridges between actin and myosin filaments, causing them to interdigitate which causes a contraction. muscle relaxation follows with re-uptake of calcium into sarcoplasmic reticulum
- with MH, there is a failure in reuptake of calcium by the sarcoplasmic reticulum d/t permeability. The excess calcium causes inablilty to relax muscle, sustained activation of actin and myosin filaments, this causes heat, enhanced glycolysis, uncoupling of oxidative phosphorylation.
7
Q
clinical features of MH:
- what skeletal muscle disorders predispose persons to MH
- what operations are associated with MH?
- what unexplained conditions are related to MH?
- can MH present after 1 exposure?
- does MH manifest immediately?
- how close of a family member with MH means high risk?
A
- duchenne’s m.d., central core disease, osteogenesis imperfecta
- orthopedic, opthalmic (ptosis, strabismus repair), head and neck procedures
- unexplained fevers, intolerance to caffiene, muscle cramps
- can happen on first exposure or on future exposure. 30% of patients have had 3 prior un-eventful surgeries receiving anesthesia.
- sometimes manifests post op
- relative with MH especially first degree relative
8
Q
how is MH manifested?
- most sensitive sign?
- earliest and most consistent sign?
- signs r/t head and neck?
- respiratory signs?
- cardiac signs?
- skin signs?
- urinary signs?
- muscle signs?
A
- increased ETCO2
- tachycardia
- trismus or masseter spasm after sux
- tachypnea
- arrhythmias (PVCs, bigeminy, VT)
- increased temp, cyanosis, skin mottling, profuse sweating
- myoglobinuria Tea colored urine (from myoglobinemia)
- muscle rigidity
9
Q
what are late signs (actually side effects) of MH?
A
- DIC
- pulmonary edema
- acute renal failure
- CNS signs (blindness, seizure, coma, paralysis)
10
Q
how long does it take for signs of MH to mainfest?
A
signs related to increased metablolic rate may take minutes to hours
11
Q
how is initial diagnosis made based on circumstancial data?
- metabolic signs?
- what happens to co2 absorber?
- what is a sudden severe response to sux?
- what is a facial sign seen, what can it mean?
A
- increased O2 consumption and CO2 production
- co2 absorber may become hot and exhausted
- sudden hyperkalemic responses after administration of sux to children with undiagnosed myopathy
- masseter spasm after sux (50% of children with masseter spasm have succeptibility to MH). aka “jaws of steel”
12
Q
lab findings with MH?(13 things)
A
- acidosis
- hypoxemia
- hypercapnia (on ABGs)
- hyperkalemia
- hypercalcemia
- elevated magnesium (hypermagnesemia)
- hyponatremia
- increased lactate (lactic acid)
- increased pyruvate
- increased ck
- increased lactate dehydrogenase
- increased aldolase
- increased myoglobin
13
Q
treatment of MH
physical action
A
- —-depends on early recognition; causal and symptomatic
- terminate anesthetic / inhaled anesthesia
- stop surgery
- 100% oxygen
- active cooling (surface with ice, ice water lavage to stomach and bladder, cool IV fluids); stop cooling when temp gets down to 38 degrees
- alkalanization with bicarb
- hydrate and diurese (osmotic and tubular diuretics)
14
Q
dantrolene:
- whats dantrolene made of?
- what does it do?
- why dantrolene?
- what is the dose/ interval?
- how is it supplied and reconstituted?
- what speeds up reconstitution?
- how long does it take to work?
A
- hydantoin (dilantin) derivative
- interferes with muscle contraction at the RYR1 receptor calcium channel
- it is the only reliable treatment for MH
- 2-3 mg/kg (up to 5 mg/kg) iv every 5 minutes to max of 10mg/kg.
- comes in 20 mg lyphilized powder to be dissolved in 60cc of sterile water.
- warm diluent to (40 degrees C) to speed reconstitution
- should respond in 45 minutes
15
Q
prognsis post MH
- how long in ICU?
- what was mortality before dantrolene, what is mortality with?
A
- 72 hours in aicu
- without dantrolene 70% mortality;
with dantrolene 5% mortality
16
Q
how to identify MH patients
- what is the test?
- what is the accuracy?
A
- halothane contracture test (a muscle chunk is exposed to halothane and caffiene to see if it contracts).
- 97-99% sensitivity
10-20% false positive
0% false negative though
17
Q
what does duchennes muscluar dystrophy do in regards to anesthesia?
A
highly related to anesthesia induced rhabdomyolysis due to stress on fragile muscle cells; they will have more sux induced hyperkalemia
70% of these patients have increased resting concentrations of creatnine kinase (although this is not a definitive diagnosis).
18
Q
anesthesia for MH risk patient:
how would you remove risk of reaction? (1-4)
A
- remove triggering agents (take gasses out of machine, get rid of succ)
- remove co2 absorber
- change circuit
- flush gas machine with 10L o2 for 10-60 minutes
19
Q
what is the cause of the most serious complications of anesthesia
A
respiratory events:
- unrecognized breathing circuit disconnect - airway mismanagement - anesthetic machine misuse
19
Q
what agents are NOT safe for MH patient?
A
- ALL volitile agent (halo, sevo, iso, des) are bad
- sux is bad
- calcium channels can react with dantrolene to cause hyperkalemia and myocardial depression
20
Q
negative pressure pulmonary edema
- cause:
- to whom does it happen?
- pathophysiology?
- treatment:
- resolves within:
A
1.follows upper airway obstruction, laryngospasm (post op), epiglottis, tumors, obesity, hiccups and obstructive sleep apnea
2.young healthy males (can generate more negative intrapleural pressure)
3.
4.supplemental oxygen, usually self limiting, mechanical ventilation
5. 12-24 hours
20
Q
what are safe meds for MH patient?
A
- barbs
- propofol
- opiates
- benzos
- ketamine
- inapsine
- regional anesthesia (amides are ok)
- Non depolarizing MRs
(be careful…if pre treated with dantrolene, it will prolong response to NDMR).
21
Q
airway injury: (5 kinds)
A
- sore throat
- dysphagia
- dental trauma (most common permanent injury)
- TMJ (more common in females)
- soft tissue injury
b. princip. exam 2 (w13)
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