Clinical trial NCT01119248: Pediatric Temperature Variation in the MRI Scanner Under General Anesthesia
Official title: Pediatric Temperature Variation in the MRI Scanner Under General Anesthesia
Study type: OBSERVATIONAL
Overall status: COMPLETED
Conditions: Children Requiring MRI
Keywords: Children MRI General Anesthesia
Lead sponsor: Rutgers, The State University of New Jersey
Sponsor class: OTHER
First posted: 2010-05-07
Enrollment: 120
Sex: ALL
Minimum age (years): 6
Maximum age (years): 8
Standard ages: CHILD
Accepts healthy volunteers: no
Observational model: CASE_ONLY
Time perspective: PROSPECTIVE
Sampling method: PROBABILITY_SAMPLE
Study population: Children 6 months to 8 years

Brief summary: The number of children undergoing MRI imaging has increased significantly in the past years, because many young children cannot stay still for the duration of the scan, have difficulty tolerating the confined space and the noise produced by the Magnetic Resonance Imaging (MRI) machine, sedation or General Anesthesia is required in these cases. In the investigators institution, the investigators use General Anesthesia for children undergoing MRI.

Because children have a larger surface area to body weight ratio; hypothermia from passive heat loss is one of the anesthesiologists' concerns.

MRI requires a cool environment with low humidity; this specialized environment represents a significant thermal challenge to the anesthetized children. Since most temperature devices are not compatible with the MRI, the simple task to measure temperature change has never been investigated.

Detailed description: It is known that following the induction of anesthesia, core hypothermia occurs in three stages;

1. Redistribution
2. Linear phase
3. Plateau phase Redistribution This accounts for the largest drop in core temperature of the three stages. Vasodilatation causes redistribution of heat from the core to the periphery.

Linear Phase This begins at the start of surgery as the patient is exposed to cold cleaning fluids and cool air flow in the theatre. Heat loss exceeds heat production, and most surgery does not extend past the linear phase.

* Radiation contributes the most (40%) and is proportional to environment/core, temperature difference to the power of four.
* Convection contributes up to 30% and is proportional to air velocity.
* Conduction contributes up to 5% and is proportional to the difference in surface temperatures.
* Evaporation contributes up to 15% and occurs from cleaning fluids, skin, respiratory and wound. A laparotomy can contribute up to 50% of the total.
* Respiratory contributes 10% (8% evaporation of water; 2% heating of air) and is enhanced by the cooling effect of cold anesthetic gases.
* Cold intravenous fluids. Plateau Phase Once core temperature falls below the thermoregulatory threshold, peripheral vasoconstriction increases and acts to limit the heat loss from the core department. When core heat production = heat loss to the peripheral compartment, core temperature reaches a plateau. Patients with an autonomic neuropathy (diabetics) have impaired sympathetic vasoconstriction and are unable to establish a core plateau in phase 3. Combined general and regional anesthesia will have a similar effect as the regional anesthetic (spinal/epidural) will prevent vasoconstriction in the legs; i.e. failure to establish a core plateau.

The ability to maintain body temperature is also compromised because anesthesia impairs intrinsic thermoregulatory response.

Heating devices including fluid warmers and bear huggers, commonly used in the Operating Room theaters, are incompatible with MRI.

On the other hand, MRI produces Radiofrequency Energy that transforms into heat within the patient's tissues. This may partially offset the heat loss.

The purpose of our study is to determine if children undergoing MRI under General Anesthesia become hypothermic and whether aggressive measures should be taken to prevent passive heat loss during MRI studies.

Study Design This is an observational, prospective non blinded study.

Eligibility criteria: Inclusion Criteria:

* 6 months to 8 years undergoing general anesthesia for elective MRI of brain, spine and extremities. Patients who were ASA physical status 1-3 only were included.

exclusion criteria: Patients who were ASA 4-5 were excluded from the study. Patients not NPO for solids for 8 hours and liquids for 2 hours were excluded.

Primary outcomes:
measure: Change in Body Temperature in Children Undergoing MRI Under General Anesthesia (GA)and Change in Room Temperature Before and After MRI
timeFrame: prior to induction of general anesthesia and at conclusion of MRI an average of two hours
Secondary outcomes:
measure: Relationship Between Pre MRI Body Temperature and Change in Body Temperature After MRI
timeFrame: Prior to start of general anesthesia and immediately after completion of MRI an average of two hours
measure: Relationship Between Body Surface Area (BSA) and Change in Body Temperature After MRI
timeFrame: Prior to start of general anesthesia and immediately after completion of MRI scan an average of two hours
Other outcomes:
Locations:
city: Newark
country: United States
facility: University Hospital
state: New Jersey
Study officials:
affiliation: Rutgers-NJMS
name: Anuradha Patel, MD
role: PRINCIPAL_INVESTIGATOR
References: