MALIGNANT HYPERTHERMIA(MH)

MH DEFINED 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 autosomal- dominant, life-threatening disease Genetic autosomal-dominant means that 50% of siblings or children will inherit the gene defect

EPIDEMIOLOGY(CONT) 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) 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) 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) Mortality during MH is a result of: – Acidosis – Hyperkalemia – Organ failure, secondary to hyperthermia – Disseminated intravascular coagulation – Renal failure secondary to myoglobinuria

PATHOPHYSIOLOGIC MECHANISMS OF MH 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) 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 Only definitive diagnostic test for MH is a costly caffeine halothane contracture test (CHCT) on freshly biopsied muscle – 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 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 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 – All local anesthetics – Barbiturates – Etomidate – Ketamine – Nitrous oxide – Other muscle relaxants – Propofol

CLINICAL SIGNS OF MH 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) 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) 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) 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) 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) 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: Cocaine toxicity Hypoxic encephalitis Intracranial trauma Light anesthesia Pheochromocytoma Sepsis Thyroid storm Certain myopathies Heat stroke, strenuous exercise exertion

MANAGEMENT OF MH ~ DANTROLENE 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 After 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 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 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 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 – 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) 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 – 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) 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) 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) Initiates the MH protocol – 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) 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 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) Supplies needed: – Dantrolene sodium IV( 20 mg vials),60 ml syringes – 2,000 ml sterile water for injection without bacteriostatic agent – Mix: 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) Bring crash cart Mix and administer medications as needed Supplies needed: – 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) Prepare CaCl, 2 mg/kg Prepare mannitol 500 ml x 2 or ml vials Prepare lasix (40mg vial) 4ml x 2 Prepare antiarryththemic medications as directed(lidocaine,procainemide)

COOLING NURSE (S) Cool the room Bring cold saline and ice Cool and monitor patient temperature Supplies needed: – 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) 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 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 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 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