Pediatric Temperature Variation in the MRI Scanner Under General Anesthesia

Study Overview
=================
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; Redistribution Linear phase 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.

Official Title
-----------------
Pediatric Temperature Variation in the MRI Scanner Under General Anesthesia

Conditions
-----------------
Children Requiring MRI

Intervention / Treatment
-----------------
* Other: axillary temperature before MRI and after the MRI


Participation Criteria
=================
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.

Ages Eligible for Study
-----------------
Minimum Age: 6 Months
Maximum Age: 8 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
No

Study Plan
=================
How is the study designed?
-----------------

Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Children undergoing MRI<br>120 children ages of 6 months and 8 years for MRI and axillary temperature before MRI and after the MRI with MRI compatible device | Other: axillary temperature before MRI and after the MRI<br>* observation of body temperature changes with axillary temperature measurement with MRI compatible device<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in Body Temperature in Children Undergoing MRI Under General Anesthesia (GA)and Change in Room Temperature Before and After MRI | Axillary temperature was measured with MRI-compatible Tempa dot immediately before general anesthesia was induced. Second axillary temperature reading was taken at the conclusion of the MRI scan before emergence from general anesthesia. Room temperature was measured with a digital thermometer placed in scanner room outside the magnet range. | prior to induction of general anesthesia and at conclusion of MRI an average of two hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Relationship Between Pre MRI Body Temperature and Change in Body Temperature After MRI | Bivariate analysis between pre MRI body temperature and change in body temperature after MRI. Body temperature of the subjects was measured with MRI compatible Tempadot. Reported is the change in body temperature after MRI with 1 degree increase in body temperature between subjects after adjusting for body surface area (BSA), type of MRI and duration of MRI. A positive change value reflects a child who was 1 degree C warmer experienced greater warming. The negative change reflects that a child who was 1 degree C warmer experienced greater cooling. | Prior to start of general anesthesia and immediately after completion of MRI an average of two hours | 
| Relationship Between Body Surface Area (BSA) and Change in Body Temperature After MRI | Bivariate analysis between BSA and change in body temperature after MRI. Reported is the change in body temperature after MRI with 1m2 increase in BSA, after adjusting type of MRI and duration of MRI. A positive change value reflects increase in body temperature with an increase in BSA and vice versa | Prior to start of general anesthesia and immediately after completion of MRI scan an average of two hours | 

 Terms related to the study
=================
Keywords Provided by Centre Hospitalier Valida
-----------------
Children MRI General Anesthesia