Pediatric Anesthesia and Malignant Hyperthermia

1. Pediatric Anesthesia and Malignant Hyperthermia By: Ashley Evick, BSN, SRNA

2. Objectives • To identify the mechanism of thermoregulation for children of various ages • To identify risks of hypothermia • To define and be able to quickly identify a malignant hyperthermia emergency in the operating room • To be able to discuss the differences in malignant hyperthermia presentation in children versus the adult

3. Our patients… Children are NOT little adults They are a unique patient population Age groups: Neonate: less than 30 days Infant: 1-12 months Toddler: 13-23 months Preschool: 2-5 years School age: 6-11 years Adolescent: 12-18 years

4. Thinking about our care… You must consider a child’s developmental stage and the unique features of each stage Care must be appropriate to each developmental age Unique physiological aspects of each age group and patient must also be considered

5. What are our major anesthesia differences?

6. Airway Children have larger tongues Larger heads and shorter necks, larger occiput Larynx is at C 3-4 level Larger epiglottis, that is narrower and elongated Infant’s vocal cords slanted posterior and cephalad Anterior airway more prone to injury Narrowest part is cricoid cartilage (until 5 years old)

8. Major Lung Differences • Rapid breathing rate and increased alveolar ventilation • Prone to rapid desaturation due to high oxygen consumption • Small FRC, fast inhalation induction • Prone to atelectasis closing capacity may exceed FRC • Lung matures at 8 years old • Increased chest compliance • Herring-Breuer reflex- deep breath and kids stop breathing and vagal negative feedback loop via vagus nerve

9. Major Cardiac Differences • High CO • HR dependent • Non-compliant heart • Avoid air bubbles due to possible PFO • Vagal dominant and unopposed

10. Thermoregulation

11. Hypothermia • Defined as a core temperature below 35 degrees centigrade • Asystole occurs at 30 degrees centigrade

12. Pediatric Thermoregulation • Adults use shivering to increase heat production (increases O2 consumption, CO2 production, and CO) • Shivering is inefficient in young children • Non-shivering thermogenesis

13. Non-shivering thermogenesis • Cold induced O2 consumption and heat production • Primary means in infants to produce heat • Utilize brown fat- rich in mitochondria, dense capillary network, and innervated by SNS nerve endings • Brown fat is 6% of neonates total body weight

14. How it works….. • When norepinephrine is stimulated by SNS, triglycerides are hydrolyzed to fatty acids and glycerol with heat being released from enhanced oxygen consumption

15. Other Differences • Body surface area (BSA) to body mass is very high • Infant’s head is 20% of BSA and contributes to 40% of heat loss • Rapid heat loss

16. Mechanisms of Heat Loss • Evaporation • Conduction • Convection • Radiation

17. Evaporation • The energy of heat is consumed in the conversion of water to vapor • Example: sweating and respiration • Accounts for approximately 22% of heat loss (combined with convection) • How to counteract this: • Humidified circuits • Run lower gas flows

18. Conduction • The transfer of heat energy due to a temperature gradient • Example: skin touching metal OR table • Accounts for approximately 15% of heat loss (combined with convection) • Pediatric patients have a thinner layer of subQ fat so more heat is lost though conduction • Ways to counteract this loss: • No skin to metal contact • Irrigation solution warmed • Warm IV fluids

19. Convection • The warmed air or water must be moved away from the skin surface by currents • Example: laminar air flow in OR • Accounts for approximately 15% of heat loss (combined with conduction) • Ways to counteract this: • Limit air flow across patient • Warming blankets above and below patient

20. Radiation • Heat from core body tissues is transported in blood to subcutaneous vessels, where heat is lost to the environment through radiation. • Accounts for approximately 60% of heat loss • Major form of heat loss in surgical patients • Ways to counteract this: • Keep patient covered • Warming blankets • Keep room temperature elevated

21. The research says…. • Best to use a warmer ambient room temperature and warming blankets • Pre-warming proved beneficial in studies • Esophagus, nasopharynx or rectum (highly perfused tissues, the temperature of which is uniform and high in comparison with the rest of the body) best for measurement

22. Effect of General Anesthesia • With GA there is a redistribution of heat from core to periphery as a result of vasodilation • Anesthetic inhibits vasoconstriction • With GA heat production is decreased by 30% • See a rapid decrease in core body temperature

23. Risk with hypothermia • After cold exposure infant’s metabolic rate increases • Vasoconstriction (in un-anesthetized child) • Cellular hypoxia and metabolic acidosis • Pulmonary vasoconstriction= right to left shunting if PFO or ductus present • Worsening hypoxia

24. Additional Risks with Hypothermia • Adverse cardiac events • Prolonged stay in the recovery room and hospital • Delayed surgical wound healing and higher infection rates • Cold-induced coagulation dysfunction • Prolonged drug metabolism

25. Hyperthermia • Elevated body temperature due to failure of thermoregulation or other disorder • Heat stroke • Adverse reaction to drugs, such as malignant hyperthermia

26. Case Discussion

27. History • 4 month old male • Wt. 6.48 kg • NKDA • No past surgical HX • No medications • HX of trigonocephaly and premature birth • No family HX of surgery

28. Surgical procedure Craniosynostosis GA with ETT Anticipation of large blood loss

29. Anesthetic plan • No premedication (child calm) • Inhalation induction with N2O and sevo • Intubation with ETT • Rectal temp placed • 22g, 24g, and 20g IV placed • A-line placed (took quite a long time) • Infant on under body blanket, heated circuit used, and room temperature increased • Remi and precedexgtts used • 0.9% NS and LR infusing • Maintained on Sevoflurane • Upper body blanket placed on infant, in addition to under body blanket

30. Case progression 90 minutes into case HR increased to 150s BP slight increase O2 saturation decreased to 97% EtCO2 gradually increasing to a peak of 53 (unresponsive to changes in ventilation) Temp. increasing 0.1 degree Celsius at a time (child hypothermic to begin 33 degrees Celsius) See next slide for graphic

32. Differential Diagnosis • Gave fentanyl and remi boluses to assure child was not too light • No change in EtCO2 in ventilation changes • ETT in good position and not obstructed • MALIGNANT HYPERTHERMIA!!!!

33. Labs

34. Myoglobin in urine: negative

35. Treatment • Call for help!!!! • Sevo stopped, flows increased • CO2 absorber and circuit changed • Ice applied to infant, warming blankets turned off, and room temp decreased • Dantrolene 2.5 mg/kg initial dose • Insulin R • Dextrose • Gtts changed to plasma-lyte • Remi and precedexgtts ran as anesthetic agents • Calcium chloride given • MHAUS called and assisted in treatment plan • Emergency algorithm guide used • Versed given • Subsequent doses of Dantrolene given at 1.5 mg/kg then 1 mg/kg • Child transferred to PICU and remained on ventilator

38. Malignant Hyperthermia • Autosomal dominant genetic disorder of ryanodine receptor gene (RYR1) • Causes uncontrolled increase in skeletal muscle oxidative metabolism, overwhelming oxygen supply and removal of carbon dioxide, this reaction releases heat and causes acidosis and circulatory collapse • Triggers: volatile anesthetic gases, succinylcholine, and stress • Signs/symptoms: elevated temperature, increases HR, increased RR, acidosis, hypoxia, rigid muscles, rhabdomyolysis, myoglobin in urine, CK elevation

40. Differences in pediatrics • A study analyzed 264 records: 35 in the youngest age group (0-24 months), 163 in the middle age group (25 months- 12 years), and 66 in the oldest group (13-18 years). • Sinus tachycardia, hypercarbia, and rapid temperature increase were more common in the oldest age cohort. Higher maximum temperatures and higher peak potassium values were seen in the oldest age cohort. • Masseter spasm was more common in the middle age cohort. • The youngest age cohort was more likely to develop skin mottling and was approximately half as likely to develop muscle rigidity. The youngest age group also demonstrated significantly higher peak lactic acid levels and lower peak CK values. The youngest subjects had greater levels of metabolic acidosis. (Nelson, 2013)

41. A Published Case Report The Case: Discussion: MH-susceptible patient responds differently to various agents Atypical MH forms are problematic It is possible that the speed of onset reflects the rate of increase of the intracellular Ca2+ concentration, which depends on the particular drug used, its concentration in muscles and any number of physiological variables that dictate the efficacy of Ca2+ homeostatic processes in each patient. (BONCIU, 2007) • 7-year-old boy with cholesteatomasunderwent tympanoplasty. • Three previous anesthetics with sevofluraneinduction and maintenance with propofol infusion were not associated with MH symptoms. • No family history of MH or muscle disease • A minor rise of end tidal CO2 • Increased rectal temperature • Rhabdomyolysis and his father’s positive IVCT results

42. Another Case Report • Two cases of MHtriggered by sevoflurane: • First Case: 6 year old girl stabismus repair 30 min after induction, etCO2 was over 60 mmHg. Muscle rigidity of legs and elevation in temperature. Maximum esophageal temperature was noted to be 40.4 degrees Celsius. CK was 252 post-op and 1690 the next day. • Second Case: 1 year and 9 month boy undergoing accessory ear resection. Sevoflurane used. 40 min after induction temperature was 38.6 degrees Celsius, HR 191, and oxygen saturation 93%. Muscle rigidity of the legs was noted. Highest temperature was 39.3 degrees Celsius. Both parents had no history of MH. (Kinouchi,2001)

43. Take Home Message • Kids can present with MH differently than adults • If MH is suspected treat with MH protocols • Early interventions have the best outcomes

44. References • CASSEY , J., KING, R., & ARMSTRONG , P. (2009). Is there thermal benefit from preoperative warming in children?. Pediatric Anesthesia, 20(1), 63-71. Retrieved from http://onlinelibrary.wiley.com/doi/10.1111/j.1460-9592.2009.03204.x/abstract • Díaz, M., & Becker, D.(2010). Thermoregulation: Physiological and clinical considerations during sedation and general anesthesia. Anesthesia Progress, 57(1), 25-33. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2844235/ • Pearce, B., Christensen, R., & Voepel-Lewis, T. (n.d.). Perioperative hypothermia in the pediatric population: Prevalence, risk factors and outcomes. Journal of Anesthesia & Clinical Research, 1(1), 1-4. Retrieved from http://www.omicsonline.org/2155-6148/2155-6148-1-102.pdf • Sessler, D. (2011). Temperature monitoring: Consequences and prevention of mild perioperative hypothermia. American Society of Anesthesiologists, 109, 1-7.

45. References • BONCIU, M., DE LA CHAPELLE, A., DELPECH, H., DEPRET, T., KRIVOSIC-HORBER, R., & AIMÉ, M. (2007). Minor increase of endtidal CO2 during sevoflurane-induced malignant hyperthermia. Pediatric Anesthesia, 17(2), 180-182. doi:10.1111/j.1460-9592.2006.02051. • Kinouchi, K., Okawa, M., Fukumitsu, K., Tachibana, K., Kitamura, S., & Taniguchi, A. (2001). [Two pediatric cases of malignant hyperthermia caused by sevoflurane]. Masui. The Japanese Journal Of Anesthesiology, 50(11), 1232-1235. • Nelson, P., & Litman, R. (2013). Malignant Hyperthermia in Children: An Analysis of the North American Malignant Hyperthermia Registry. Anesthesia And Analgesia.

46. Thank You Questions?