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Several years ago, a young, healthy, male patient arrived at my center for elective arthroscopy with no personal or family history of problems with malignant hyperthermia. The procedure was uneventful. In PACU, the patient was responsive to commands, denied discomfort and voiced no complaints. About 15 minutes into his recovery, however, he became unresponsive, tachycardic and, although warm to the touch, had a normal axillary temperature. As blankets were being removed, the patient began to display full-body muscle rigidity. We realized he was in the midst of an MH episode. It happened quickly and seemingly without warning.
The patient might have died if we had been unprepared to handle the crisis, but he was successfully treated, thanks to well-trained physicians and staff. Learn from our brush with disaster. Recognize MH, have easy access to the equipment and drugs necessary for treatment and master a response protocol. In short, you must:
1. Recognize early signs and symptoms. MH can occur at any time after a triggering agent has been administered. Fully investigate any symptom that you can attribute to MH. Don't dismiss these signs and symptoms of MH: an abnormally rising end tidal CO2 (early sign), trunk or total body rigidity, masseter rigidity, tachycardia, tachypnea, acidosis, hyperkalemia and fever that may exceed 110 ?F (often a later sign). Closely and continuously monitor patients' expired CO2 concentrations and temperatures. An MH crisis isn't limited to the operating room; it often occurs during the recovery phase, so continue close patient monitoring until discharge.
2. Maintain a stocked MH cart. Having an adequately stocked emergency MH cart nearby is essential any time triggering agents are administered. The cart must be easily recognizable and designated solely for MH response. It should be of sturdy construction and designed to avoid tipping if multiple drawers are open. This type of cart is available through medical supply catalogs and in some home improvement stores.
MH carts must be lockable. Avoid keyed locks; use breakaway fasteners instead. Post an inventory list on or in the cart, which will aid your staff in tracking expiration dates of supplies. Also include a flow sheet for recording the events of a crisis.
Your emergency cart should be big enough to house all necessary items in sufficient quantity. Neatly organize and clearly label inventory for easy access. MH treatment posters and other educational materials are available through the Malignant Hyperthermia Association of the United States (www.mhaus.org). Display these on and within the MH cart.
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Assembling Dantrolene Kits |
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Step 1: Connect fluid path to sterile water. Step 2: Connect stopcock to fluid path. Stopcock should be in "off" position. Step 3: Connect 60cc syringes to stopcock. Step 4: Puncture dantrolene sodium with mini-spike. |
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Mixing Dantrolene |
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Step 1: Team member No. 1 opens stopcock and withdraws 60cc sterile water. Step 2: Team member No. 1 reconstitutes dantrolene. Gently shaking while alternating aspiration and injection helps to speed the reconstitution process. Team member No. 2 prepares another syringe of water. Step 3: Have as many teams as possible working simultaneously, each using its own dantrolene kit. The process of aspirating water, mixing dantrolene and handing off reconstituted doses to the anesthesia provider continues until the crisis is over. |
3. Prepare dantrolene kits. Dantrolene sodium is the only specific treatment for MH. Always have a minimum of 36 vials of dantrolene on hand. After our MH event we assessed our response and created dantrolene kits (see photo) to improve our drug delivery process. The kits contain everything needed to prepare the drug: 1,000cc sterile water, 2 60cc syringes, a 3-way stopcock, a mini-spike dispensing pen and a fluid path. They're passed to responders as they arrive to help, which helps eliminate confusion and speeds the drug's preparation and delivery during chaotic emergency responses.
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When MH Occurs
Anesthetics to Avoid Patients susceptible to MH can safely receive anesthesia if triggering agents are replaced with alternatives, including:
Supply Essentials Keep these items refrigerated:
Other supplies:
Role Assignments
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4. Have a response plan in place. This plan should include a written step-by-step protocol for managing an MH crisis. As you prepare your protocol, keep in mind that trained anesthesia providers should be on site any time MH-triggering agents are used; they're the ones who should make the MH diagnosis. Once an MH diagnosis has been made, begin treatment with dantrolene immediately. Non-hospital facilities should initiate emergency transfer to a tertiary care facility. Do not delay treatment while waiting on a transfer. Once the patient is transferred, the anesthesia provider and the physician at the receiving facility should stay in touch.
Two or more responders can work simultaneously with the same dantrolene kit to mix and pass the drug to the field for administration. Use expired dantrolene, which should be clearly marked as such and sequestered from your drug inventory, to practice the reconstitution technique. Conduct impromptu in-services throughout the year so all staff can practice their skills. As a result of our preparation and practice, our staff is confident that a future MH event will be as successful as our first.
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Just What Is MH? |
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Malignant hyperthermia is an inherited disorder of the skeletal muscle that's triggered by inhalation anesthetic agents and the paralyzing agent succinylcholine. MH-susceptible individuals have a presence of abnormal proteins in the muscle cells of their body. When exposed to certain anesthetic agents, an abnormal release of calcium occurs in muscle cells, resulting in sustained muscle contraction, which increases energy utilization and heat production and results in severe muscle damage. This severe muscle breakdown releases the muscle pigment myoglobin (manifested by the presence of brown urine) that can be toxic to the kidneys. Large amounts of potassium are released into the bloodstream, which can lead to heart rhythm abnormalities. In an MH-susceptible individual, this biochemical chain reaction can result in cardiac arrest, organ failure, blood coagulation problems, internal hemorrhaging and brain injury. An MH crisis can result in death even when properly treated. MH can occur in all races and ages, but it's more common in children. Because it's a dominantly inherited disorder, consider close relatives of those with known MH to be MH-susceptible and manage them accordingly. Children and siblings of MH-susceptible individuals have a 50% chance of inheriting the gene defect. An MH crisis may not occur every time anesthesia is delivered; MH deaths have occurred in patients that have undergone multiple surgeries without previous complications. Although the exact incidence of MH is unknown, the rate of occurrence is estimated to be 1 in 20,000 administrations of general anesthesia. — Cheryl Fielder, RN, CASC |
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Why So Much Dantrolene? |
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Ever wonder why it's recommended that you keep at least 36 vials of dantrolene on hand at your facility? Dantrolene sodium is supplied in 20mg vials. It's administered during an MH event at 2.5mg/kg up to a total of 10mg/kg. "? An average 70kg man would receive 2.5mg x 70kg = 175mg for the initial dose. "? A 175mg dose / 20mg vial = 9 vials per dose. "? Dantrolene may be administered as needed up to 4 times for a total dose of 10mg/kg. "? 9 vials per dose x 4 doses = 36 vials of dantrolene. |
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Preventative MH Measures |
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The best way to prevent a malignant hyperthermia crisis is to identify high-risk individuals before surgery and manage them accordingly. Perform a comprehensive pre-anesthetic evaluation on every patient, asking about personal and family history of adverse reactions to anesthetics. MH is thought to be associated with certain myopathies, so ask patients if they have a history of muscle disorder. Communicate risk factors to your surgical team. There is no simple diagnostic test for MH. The most accurate screening is the caffeine halothane contracture test, which involves skeletal muscle biopsy. This is an invasive test on fresh tissue and is usually performed only on patients that have a family history of MH or who have experienced adverse reactions to anesthesia believed to have been MH. Refer patients to the following locations for this high-level testing:
Take additional precautions with patients who have a known susceptibility to MH. Avoid inhalation anesthetics and succinylcholine; use non-triggering agents or local anesthesia instead. Propofol induction with nitrous, propofol for maintenance and narcotics are appropriate. Disable vaporizers, flush anesthesia machines and ventilators with oxygen at 10L/min for 20 minutes and change CO2 absorbents before surgery. Closely monitor the at-risk patient's temperature and keep dantrolene sodium at the ready. Monitor the patient for a minimum of 4 hours post-op. It's not recommended to treat patients with a known susceptibility to MH in an ambulatory surgery setting. — Cheryl Fielder, RN, CASC |
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