Transcript MALAGNANT HYPERTHERMIA(MH)

MALIGNANT
HYPERTHERMIA(MH)
MH DEFINED
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A clinical syndrome of markedly accelerated
metabolic state characterized by fever(could go as
high as 110 degrees F/43.3 degrees C)
tachycardia,tachypnea,cyanosis, and hypercarbia.
It is a rare, but treatable mostly genetic autosomaldominant, life-threatening disease
Genetic autosomal-dominant means that 50% of
siblings or children will inherit the gene defect
EPIDEMIOLOGY(CONT)
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First documented case of MH in the 1960’s—a 21
yr.old trauma patient with a strong family history of
temperature-related complications of anesthesia
(including 10 deaths)
EPIDEMIOLOGY(CONT)
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The pt. experienced hypotension,
tachycardia and became cyanotic and
extremely hot after 10 minutes under general
anesthesia
Anesthesia was stopped and the pt. packed
in ice ~ he recovered without residual effects
EPIDEMIOLOGY(CONT)
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MH occurs most commonly between the
ages of 2-42 years
More than 2/3 are male
Incidence of MH ranges from 1:5,000 to
1: 65,000
High number of MH families in
Wisconsin,W,Virginia,Michigan, and
Nebraska
EPIDEMIOLOGY(CONT)
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Mortality during MH is a result of:
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Acidosis
Hyperkalemia
Organ failure, secondary to hyperthermia
Disseminated intravascular coagulation
Renal failure secondary to myoglobinuria
PATHOPHYSIOLOGIC MECHANISMS
OF MH
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MH is a fulminating hypermetobolic state
triggered by an abnormality of calcium
release or reuptake by the sarcoplasmic
reticulum with muscle contraction
MH occurs in genetically predisposed
individuals when exposed to triggering
agents
PATH MECH (CONT)
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Initially during an MH episode, there is increased
CA+ release in response to triggering agents
The resultant intracellular hypercalcemia leads to
hypermetabolism,which in turn results in increased
sympathetic activity, increased CO2 production,
increased O2 consumption, and disruption of the cell
membranes
Because of the inability of muscle tissue to return to
a resting state in the susceptible pt., the primary
signs of MH begin to occur
DIAGNOSING MH SUSCEPTIBLITY
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Only definitive diagnostic test for MH is a costly
caffeine halothane contracture test (CHCT) on
freshly biopsied muscle
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A portion of the quadriceps muscle is removed and
stretched on a clamp and immersed in a caffeine solution
When a baseline state is met, halothane (an anesthetic gas)
is introduced into the solution and contracture is observed
In a pt. who is positive for MH, the rate of contracture is
markedly higher than in a pt. who is negative for MH
DIAGNOSING MH
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A new option for diagnosing MH susceptible patients
has recently been developed—a molecular genetic
diagnostic test with DNA analysis-only detects 30%
of cases
The CHCT is a very sensitive test that detects
virtually all patients who are susceptible to MH
TRIGGERING AGENTS
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MH is most often associated with the use of
inhalational anesthetic gases and the use of the
muscle relaxant succinylcholine
Anesthetic agents that do not trigger MH include
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All local anesthetics
Barbiturates
Etomidate
Ketamine
Nitrous oxide
Other muscle relaxants
Propofol
CLINICAL SIGNS OF MH
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An MH event usually occurs within 10 minutes of
exposure to a triggering agent ~ delayed onset of as
long as 11 hrs. after exposure also has been
reported
Some health care workers mistakenly believe that
the most immediate symptom of MH is a rapid
sustained rise in body temperature~ (often greater
than 43 degrees C) ~although it is a cardinal sign of
MH, it is a relatively late symptom that actually
occurs in only 30% of pt’s experiencing MH
CLINICAL SIGNS (CONT)
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Unexplained increase in end-tidal CO2
during constant ventilation frequently
exceeding 80 mmHG (the most sensitive
sign)
Unexplained Tachycardia~96% of pt’s (the
most consistent clinical sign)
Unexplained tachypnea~ 85% of pt’s
CLINICAL SIGNS (CONT)
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Acidosis occurs in 80% of all pt’s in response to
increased glygogenesis. This produces abnormal
amounts of CO2, lactic acid, and heat
O2 destruction during normal ventilation and sudden
increase in end-tidal CO2 both occur in 80% of pt’s
experiencing MH. The sustained contracture of
skeletal muscle groups leads to increased use of
ATP and oxygen. Maintenance of normal oxygen
saturation is usually dependent on increased
inspired oxygen content
CLINICAL SIGNS (CONT)
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Generalized muscle rigidity, is one of the
earliest signs of MH and the most specific
sign that is present in 80% of pt.’s
experiencing MH,especially in the presence
of muscle relaxants. The masseter muscle of
the jaw is one of the most prominent muscle
groups involved
CLINICAL SIGNS (CONT)
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Cyanotic or mottled skin is present in
approximately 70% of pt’s experiencing MH
and usually starts with generalized
erythematous flush
Altered blood pressure ~ occurs in 85% of
pt’s
CLINICAL SIGNS (CONT)
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Health care providers need to be aware that other conditions
have symptoms that are similar to those exhibited by MH and
must perform a rapid differential diagnosis to determine if MH is
occurring or another condition, such as:
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Cocaine toxicity
Hypoxic encephalitis
Intracranial trauma
Light anesthesia
Pheochromocytoma
Sepsis
Thyroid storm
Certain myopathies
Heat stroke, strenuous exercise exertion
MANAGEMENT OF MH ~
DANTROLENE
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Dantrolene is the drug of choice to treat a MH event.
It is a selective skeletal muscle calcium channel
blocker. It antagonizes sarcoplasmic CA+ release,
lowering high CA+ concentrations and thus reversing
the episode of MH
Dantrolene has little to no effect on cardiac muscle,
whereas, calcium channel blockers such as
verapamil or diltiazem lower cardiac output and have
had fatal results if given in acute MH
DANTROLENE
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After 30-40 minutes, the patient should be free of
signs and symptoms
The therapeutic effect (2.5 mg/kg) persists for 4-6
hrs; thereafter, supplemental doses (2.5mg/kg) are
administered every 4 hrs. for 24-36 hrs.
About 25% of pt’s have persistent signs and
symptoms that occur within hours of the first episode
and require aggressive treatment with Dantrolene
(10mg/kg IV bolus) followed by the usual IV
maintenance dose
MANAGEMENT ~ ANESTHESIA’S
ROLE
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If an MH event occurs notify the surgeon and
OR of the event
The anesthesia provider discontinues the
trigger (anesthetic agents)
Hyperventilate the pt. with 100% O2, change
ventilatory circuit, and CO2 absorber
Mobilize response effort
MANAGEMENT ~ THE
PERIOPERATIVE NURSES ROLE
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The role of the perioperative nurse is critical,
requiring rapid response and cooperation of
the entire perioperative team
Perioperative nurses should perform MH risk
assessments during their routine
preoperative interviews
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Identifying pt’s at risk for an MH crisis and
instituting proper precautions decreases the
mortality and morbidity associated with MH
PERIOPERATIVE NURSE ROLE
(CONT)
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Nurses (as well as anesthesia) should
assess pt’s for caffeine intolerance, a
personal or family history of MH,and prior
complications arising from anesthesia,
including
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Any unexplained fever;
Cola-colored urine; or
History of muscle weakness, cramps, or muscle
group hypertrophy
PERIOPERATIVE NURSE(CONT)
Perioperative nurses should ensure that
important parameters, including end-tidal
CO2,pulse oxymetry, and temperature be
monitored for all pt’s
If MH is suspected perioperative nurses
should be prepared to measure additional
hemodynamics,including invasive blood
pressure monitoring,CVP monitoring, and
urine output
PERIOPERATIVE NURSE (CONT)
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Perioperative nurses should be aware that pt’s with
MH will require 2 large bore peripheral IVs or a
central line
The Association of Operating Room Nurses (AORN)
has worked with experts from other groups such as
the ASA,AANA,MHAUS(the Malignant Hyperthermia
Association of the US) and the American Society of
PeriAnesthesia Nurses to develop a guideline for
care of pt’s suspected of having MH
MALIGNANT HYPERTHERMIA
EMERGENCY RESPONSE GUIDELINE
(suggested)
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Four nurses are given individual roles to
perform in response to exhibited signs and
symptoms of MH with induction of anesthesia
or if MH develops during the procedure
All perioperative team members must
respond promptly to this emergency
CIRCULATING NURSE (S)
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Initiates the MH protocol
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Calls for at least three additional nurses
Assist anesthesia personnel and record
Supplies needed ~(possible) New anesthesia
machine and/or new circuit filter and soda
absorber
CVP line and arterial pressure line x 2
Blood tubes x 6 for CPK,lactate,Na,K, Cl,
Ca,Mg,myoglobin
CIRCULATING NURSE (S)
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Heparinized 5 ml blood gas syringes x 6
Tubes for coagulation studies ~ PT,PTT,plt
count,fibrinogen,fibrin split products
Urine specimen cup for Myoglobin
Urine dipstick for hemoglobin
Record medications, dosages, time of
administration, and response
DESIGNATED DANTROLENE NURSE
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Bring MH box located in the anesthesia work room
Retrieve Dantrolene from Pyxis.
Mix and administer Dantrolene (probably will need at
least one more person to reconstitute Dantrolene)
DANTROLENE NURSE(S)
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Supplies needed:
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Dantrolene sodium IV( 20 mg vials),60 ml
syringes
2,000 ml sterile water for injection without
bacteriostatic agent
Mix:
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Dantrolene 20mg vial with 50 ml of sterile water
Administer Dantrolene 2.5 mg/kg IV for initial bolus
This dose may be repeated up to 10mg/kg per continued
MH signs and anesthesia order
MEDICATION NURSE (S)
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Bring crash cart
Mix and administer medications as needed
Supplies needed:
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Medications/syringes from MH box/crash cart
Draw, prepare and label medications
Administer medications per anesthesia orders
Prepare bicarb 1 to 2 mEq/kg and repeat as directed
Prepare 0.15 units/kg regular insulin in 1 ml/kg 50% glucose
MEDICATION NURSE(S)
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Prepare CaCl, 2 mg/kg
Prepare mannitol 500 ml x 2 or 10 50-ml
vials
Prepare lasix (40mg vial) 4ml x 2
Prepare antiarryththemic medications as
directed(lidocaine,procainemide)
COOLING NURSE (S)
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Cool the room
Bring cold saline and ice
Cool and monitor patient temperature
Supplies needed:
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NG/OG tube
Foley with urimeter
Rectal tube
Cold IV saline 1,000 ml x 3 or 4 for IV administration and several
for lavage cooling
Bags and bucket of ice
Hypothermia blankets
COOLING NURSE (S)
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Core temperature probe (esophageal steth)
Prepare and administer 15 ml/kg IV cold saline x 3
NG/OG/core temperature probe to anesthesia
Place foley catheter and rectal catheter
Lavage stomach, bladder, rectum, and open cavities
as appropriate with cold NS
Monitor and record patient temperature ~ stop
cooling when pt. temperature reaches 38 C
POST MH CARE
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Once the pt. has stabilized, prepare for
transfer to the ICU for further monitoring. The
patient should stay for at least 24 hours as
MH may recur within hours of the initial
episode. Temperature fluctuations may
continue for several days.
Side effects of Dantrolene may include
muscle weakness,drowsiness,nausea,and
fatigue
MHAUS
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The Malignant Hyperthermia Association of
the United States maintains a web site and a
24-hour hotline that is staffed by
anesthesiologists across the United States
and Canada who are available to help those
dealing with an MH event
IN CONCLUSION
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Malignant hyperthermia is a rare, hypermetobolic
syndrome that is a true perioperative emergency
The OR is a complex environment with many
expectations, and perioperative nurses play a critical
role in helping maintain a safe environment for the
patient in surgery
With proper preparation, training, and teamwork, an
MH crisis can be managed without loss of life or
serious adverse consequences