Correlation of Nasopharyngeal (NP) and Lower Oesophageal (LO) Temperatures in Ventilated Children

Not Applicable

Completed

Lead Sponsor: Great Ormond Street Hospital for Children NHS Foundation Trust

Brief Summary: Children lose heat under general anaesthesia, thus temperature is routinely monitored during anaesthesia for all but the shortest cases, and active warming can be used to prevent hypothermia and its resulting complications. Temperature can be measured at several sites dependent on the type of surgery and patient factors. Previously a temperature probe has been sited in the lower third of the oesophagus (swallowing tube) but it is difficult to accurately place this without an X-Ray. Consequently it is more common to use a temperature probe placed in the nasopharynx (where the nose and throat meet), when the child is anaesthetised.

However the investigators do not know if the temperature in the nasopharynx correlates well with the real core temperature or not.This prospective, unblinded, agreement study will seek to find an agreement of 2 methods to measure temperature in children undergoing general anaesthesia with a breathing tube that has a leak.

Detailed Description: It is known that temperature in the lower third of the oesophagus correlates well with the gold standard of core temperature measurement, namely the temperature of blood in the heart. It is not known if oesophageal and nasopharyngeal temperatures correlate in children on a breathing machine via a tube with leak. If this study were to find a good correlation between oesophageal and nasopharyngeal temperature, this would allow clinicians to confidently use the more feasible nasopharyngeal temperature probes.

For this study 100 children will have both nasopharyngeal and oesophageal temperatures measured during general anaesthesia, both in the presence and absence of a leak around the endotracheal tube.

It is hypothesised that even in the presence of a leak, the temperature difference between the two methods will be less than 0.5 degrees centigrade.

Recruitment & Eligibility

Inclusion Criteria

Patient requires general anaesthesia with endotracheal intubation for a procedure assisted by radiography (e.g. line insertion, line change).
Patient requires chest radiograph for procedure.
Expected anaesthetic time more than 30 minutes.

Exclusion Criteria

No written parental written consent.
Known oesophageal pathology (e.g. tracheo-oesophageal fistula, oesophageal strictures, oesophageal varices, oesophageal atresia).
Known base of skull or midface fractures.
Previous gastric bypass surgery or nasal surgery.
Known coagulopathy.
Previous alkaline ingestion.
High aspiration risk.
Significant respiratory co-morbidity requiring anticipated peak airway pressures > 25 cm of water
American Society Anaesthesiologists (ASA) grading 4 - 5.
Tracheostomy in situ.
Severe sepsis or septic shock or other other condition (such as bronchopulmonary fistula) that precludes use of tidal volume ventilation over 7 ml/kg.
Known airway abnormalities (e.g. subglottic stenosis) that preclude placement of a MicroCuff® endotracheal tube.
Oesophageal or nasopharyngeal probe contraindicated for reasons related to surgery / procedure.

Arm && Interventions

Group	Intervention	Description
Nasopharyngeal and oesophageal temperatures	Nasopharyngeal and oesophageal temperature probes	An oesophageal and nasopharyngeal temperature probe will be placed and temperature will be measured at these site

Primary Outcome Measures

Name	Time	Method
Temperature Difference (in Degrees Celsius) Between 2 Body Sites in Children Undergoing General Anaesthesia. The 2 Sites Are: (1) Lower Oesophagus; (2) Nasopharynx	6 months	Temperature will be measured in the lower oesophagus of a child ventilated with a cuffed Endotracheal Tube (ETT). Readings will be recorded when there is no leak (cuff up) and when there is a clinically determinable, soft, audible leak (cuff down) around the ETT. Simultaneously temperature will also be measured in the nasopharynx. This will occur during general anaesthesia for a procedure that entails the performance of a radiograph (X-Ray) of the chest. The X-Ray will be used by the investigators to confirm correct placement of the temperature probe in the lower third of the oesophagus. We aim to show that the temperature measured in the lower oesophagus is the same or does not significantly differ from the temperature in the nasopharynx, even in the presence of a leak around the ETT. Temperature differences in degrees celsius will be reported.

Secondary Outcome Measures

Name	Time	Method
Temperature Difference in the Presence of a Small Leak (Fractional Volume Loss < 21%) and Large Leak (Fractional Volume Loss > 21%)	6 months	Sub-group analysis: Fractional Volume Loss (FVL) will be determined using spirometry readings taken during temperature measurements.