Remifentanil and Laryngeal Reflex Responses in Pediatric Patients With URI

To describe respiratory and laryngeal responses to laryngeal stimulation during propofol anesthesia in children with upper airway infections. To determine whether the co-administration of remifentanil blunts these reflex responses. To test whether the co-administration of remifentanil results in a significant reduction of apnea with laryngospasm in these patients.

Hypotheses:

I: In children with a URI undergoing anesthesia with propofol, the incidence of apnea and laryngospasm after controlled stimulation is expected to occur 2.5 times more frequently than in children without URI (20 vs. 8%).

II: The incidence of apnea and laryngospasm is diminished after administration of remifentanil.

Patients undergoing anesthesia in the presence of an upper respiratory infection (URI) are very common in pediatric anesthesia practice. Although, clinical data confirm that children with URIs are at increased risk of perioperative complications, it has become standard practice not to postpone anesthesia in the presence of URI. While complications (such as cough, hypoxemia) can be anticipated, recognized, and treated, laryngospasm remains the most severe and dramatic complication. In clinical practice, patients who develop laryngospasm are greater than 2.5 times more likely to have an active upper respiratory infection; therefore, knowledge that allows for rational selections of anesthetic agents under this condition is highly warranted. Based on our results obtained in healthy children, the use of propofol appears to be most promising under these circumstances. For this reason, the laryngeal and respiratory reflex responses should be assessed in patients with URI anaesthetized with propofol.

Commonly held believes suggest, that the administration of opioids blunts airway reflexes, including laryngospasm. However, in a previous study of our group in children anesthetized with sevoflurane the administration of fentanyl effectively blunted all airway reflexes but laryngospasm. These results are in contrast to those obtained in adults anesthetized with propofol where fentanyl also effectively blunted laryngospasm.

In children the combined use of propofol and remifentanil has become more frequent, particularly because of its synergistic pharmacodynamic effect. Besides its use during surgical procedures, this regime is also being increasingly advocated for diagnostic procedures such as bronchoscopy and esophago-gastroduodenoscopy. These interventions include instrumentation of the airway in children that are at an increased risk of harmful effects of laryngeal reflex responses.

Despite their obvious clinical significance, reflexes that involve the function of the upper airway are only minimally understood and information on such reflexes is scarce in anesthetized humans. Nonetheless, a model was developed by analyzing respiratory variables and endoscopic images after stimulating the laryngeal mucosa with a small amount of distilled water. This model was successfully adapted to the pediatric setting by our group assessing the impact of propofol, sevoflurane, fentanyl and lidocaine administration on laryngeal reflex responses in preschool children.

Eligibility Criteria:
Inclusion Criteria:

* ASA I + II
* elective intervention under general anesthesia
* acute upper respiratory tract infection

Exclusion Criteria:

* chronic respiratory tract infection
* fever \>38,3° celsius
* productive cough
* neuromuscular disease
* malignant hyperthermia
* cardiac disease