The Story Behind the MH Hotline

An MH Hotline Consultant takes a call. The setting is a typical OR, pulse ox beeping, multiple voices in the background.

Consultant: Hi, I’m Dr. Pinyavat, the MH hotline consultant. How can I help you?

Caller: Thank you for taking my call. I’m an anesthesiologist in the OR with a 28-year-old male, 80 kg. We are four hours into jaw surgery and his temperature has crept up to 38.5°C. I turned off the warmer, but it is still climbing. His ET-CO₂ has also been slowly rising. It was in the 40s for most of the case and now it’s 55.

Consultant: That sounds concerning. Are the other vital signs stable? Any arrhythmias?

Caller: No, thankfully. The noninvasive blood pressure is 120/75. Heart rate is 110, EKG normal.

Consultant: Great. What medications has he received? Any other medical history?

Caller: He’s a healthy guy. He said he had a cold last week, but today he was asymptomatic, so we went ahead with the surgery. He did fine for the first few hours – easy I.V. induction with propofol, rocuronium, fentanyl, and no issues with nasal intubation. We’ve had him on sevoflurane 2% with fentanyl and rocuronium boluses. I just paused the procedure, called for help, and switched to propofol.

Consultant: Where is the temperate being measured?

Caller: It’s esophageal, and it’s been climbing quickly – it went from 37° C to 38.5° C over the last 15 minutes. And my CO₂ started rising around the same time.

Consultant: What are your vent settings?

Caller: I have a tidal volume of 500 and have been going up on the respiratory rate – from 15 to 22. FiO₂ is 40%. The capnogram waveform looks normal with no signs of obstruction. His chest is clear.

Consultant: Is there a Foley? Any discoloration of the urine? Do you have access to a blood gas machine?

Caller: Yes, the urine is clear. I can send a blood gas to the lab. Now my CO₂ is 60 and the temp is 39° C.

Consultant: Yes, please get a blood gas – either venous or arterial is fine – also check potassium, glucose, and lactate. In the meantime, I agree that this is concerning for malignant hyperthermia and you should begin treatment. Hyperventilate with 100% oxygen and turn up the fresh gas flow so it is greater than the minute ventilation. Put charcoal filters on each limb of the circle system. Get dantrolene and give the first loading dose of 2.5 mg/kg. Undrape the patient if possible and give cold I.V. fluids. I would start with 1 L. What I.V. access and which form of dantrolene do you have? I’d advise a discussion with the surgeon – can they can stop at this point, or can they quickly wrap up? Keep the propofol going.

Caller: I have two 18-gauge I.V.s. Not sure about the dantrolene. I’ve never given it before. Let me see.

Consultant: I’ll stay on the line.

Chaotic sounds in the background. “Hey, the MH hotline says to give dantrolene. Do we have it here? It’s 2.5mg/kg. I need a blood gas, refrigerated saline, and charcoal filters. Let’s put in an a-line!”

Caller: Okay, we have the new dantrolene, Ryanodex. Is the dose still the same?

Consultant: Yes, dilute with 5 mL sterile water and you will end up with 50 mg/mL. For your patient who weighs 80 kg, you will need 200 mg. That’s 4 mL given as a bolus through the 18-gauge I.V. Make sure the I.V. runs well and that the blood pressure cuff does not go up while the medication is going through. Because it is very alkaline, dantrolene can cause tissue necrosis if extravasated and thrombosis if given too slowly.

Caller: Okay, we are giving it now. And the arterial blood gas came back. pH 7.2, pCO₂ 70, pO₂ 204, BE -7. K is 5.0 and lactate is 5.0. The CO₂ started to come down – now it’s 50. Temperature is 39° C.

Consultant: Sounds like he is responding to the dantrolene. The temperature should follow soon. The fluids can be at room temperature when the temperature starts to come down – you don’t want to overcool. Keep a close eye on urine output and maintain at least 2 cc/kg/hr to prevent renal injury. Check another blood gas in a few minutes, along with a CK, CBC, chem 7, myoglobin serum and urine, and coags.

Caller speaking more calmly now to the team. “We’re going to need some more labs and I.V. fluids running. Let’s get another blood gas in a few minutes. Is the a-line in yet?” Pulse ox beeping steadily. A few minutes pass.

Caller: Thanks for your help. I think he’s stable now. Temperature is down to 37.5° C, CO₂ is 40, and I’m able to come down on the respiratory rate to 18 with a tidal volume of 600. We’re waiting for the next blood gas. I’ll call the ICU. How long should we watch him there?

Consultant: He should remain in the ICU for at least 24 hours. I would suggest keeping him intubated until you see a downward trend in CK – dantrolene can cause weakness. Dantrolene should be continued to prevent recrudescence – dosed at 1 mg/kg boluses every six hours. If CK is down-trending, and vitals and labs are stable, dantrolene can be stopped after 24 hours.

Caller: Can we call you from the ICU? Anything else I need to do?

Consultant: Yes, you can call the hotline and ask for me at any time. The patient and his family members should be referred for genetic testing and told they are MH-susceptible. Please add the patient to the North American MH Registry. After this call, you will receive an email with post-episode care reminders and links to the MHAUS and MH registry websites. Details for how to order genetic testing are on the MHAUS website.

Caller: Thank you so much. I have to run and take care of the patient, but I really appreciate your help!

This dialog is representative of a typical call to the MH Hotline (1-800-MH-HYPER), the only hotline of its kind that provides direct access to a physician for consultation during a crisis. It was founded by members of the Malignant Hyperthermia Association of the United States (MHAUS), a nonprofit patient advocacy organization which recognized that access to real-time expert guidance could save lives during an MH crisis.

Since its inception in 1982, the toll-free hotline has been in continuous operation 24-7, handling approximately 700 calls per year. Among other sources of funding, MHAUS receives a yearly grant from ASA to support operations. Caller questions range from simple inquiries about preparing for a patient with known MH susceptibility (MHS) to urgent questions regarding differential diagnosis and management of an unstable patient. Most of the callers are anesthesiologists, but calls also come from nurse anesthetists, pharmacists, registered nurses, critical care and emergency medicine physicians, surgeons, and trainees. The average call duration is 5-10 minutes. However, some calls last over an hour!

MH Hotline consultants are a group of highly dedicated, board-certified anesthesiologists who have expertise in MH. Three consultants are on-call for every two-week period, and most consultants cover two two-week periods annually. Many consultants have over 20 years of clinical experience; all volunteer their time to provide this important community service (see Table). Consultants form close bonds through their participation in biannual two-day meetings, breakfasts at the ASA annual meeting, virtual educational meetings, and ongoing communication through a closed email discussion group. Serving as a hotline consultant is a unique, rewarding, and educational experience with incredible opportunities for networking and professional growth.

Complementing the Hotline, MHAUS provides an informational website (mhaus.org) for patients and health care professionals. The MH poster, an early cognitive aid and a fixture in many ORs, is also published by MHAUS. Furthermore, MHAUS partners with the North American Malignant Hyperthermia Registry (NAMHR), which houses confidential patient data and hospital records from over 6,000 patients with suspected MH episodes.

In summary, the MH Hotline, one of several resources provided by MHAUS, is a unique and valuable service provided to the anesthesiology and wider medical community. MH consultants use their experience and data reported to the NAMHR to create expert guidelines and advance our understanding of this uncommon, unexpected, and deadly disorder. While we all hope never to encounter a case of MH, it’s comforting to know that timely, expert advice is just a phone call away.