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

Pediatric Anesthesia and Malignant Hyperthermia

By: Ashley Evick, BSN,

SRNA

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

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

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

What are our major anesthesia differences?

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)

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

Major Cardiac Differences

• High CO

• HR dependent

• Non-compliant heart

• Avoid air bubbles

due to possible PFO

• Vagal dominant and

unopposed

Thermoregulation

Hypothermia

• Defined as a core

temperature below

35 degrees

centigrade

• Asystole occurs at

30 degrees

centigrade

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

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

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

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

Mechanisms of Heat Loss

• Evaporation

• Conduction

• Convection

• Radiation

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

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

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

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

•

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

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

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

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

Hyperthermia

• Elevated body

temperature due to

failure of

thermoregulation or

other disorder

• Heat stroke

• Adverse reaction to

drugs, such as malignant

hyperthermia

Case Discussion

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

Surgical procedure

• Craniosynostosis

• GA with ETT

• Anticipation of large blood loss

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 precedex gtts

used

• 0.9% NS and LR infusing

• Maintained on Sevoflurane

• Upper body blanket placed

on infant, in addition to

under body blanket

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

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!!!!

Labs time 1013 1112 1129 1200 1448

ph 7.29 7.17 7.29 7.21 7.39

CO2 48 60 39 51 38

O2 97 71 250 393 419

K 3.6 5.1 5.1 3.7 4.0

temp 33.5 38.1 37.2 35.0

Bicarb 22.3 19.4 19.3 19.3 23.6

FiO2 60 100 100 100 100

Ca 1.26 1.24 1.55 1.40 1.45

time 1130 1357 1911 0116 0500 0841 2350 0438

CK 155 192 197 245 199 202 213 83

Myoglobin in urine: negative

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 precedex gtts 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

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

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)

A Published Case ReportThe Case:

• 7-year-old boy with cholesteatomas

underwent tympanoplasty.

• Three previous anesthetics with

sevoflurane induction 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

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)

Another Case Report

• Two cases of MH triggered 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)

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

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.

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.

Thank You

Questions?