PURPOSE: The adverse events associated with long-term intubation may have their origins in tracheal changes resulting from the initial response of the airway to the endotracheal tube. We hypothesize that endotracheal intubation produces inflammation of the tracheal mucosa.
METHODS: After induction of general anesthesia the pigs (30 kg) were intubated with a modified 6.5 endotracheal tube. A catheter (14 Fr double-lumen) was glued to the ETT with the tip ending about 5 mm proximal to the cuff: this catheter was used for lavaging the upper airway. Each peritracheal lavage was carried out using a single injection of sterile saline. The recovered lavage was analyzed for polymorphonuclear cells (PMN), protein content and cytokine levels (TNF-α, IL-1beta, IL-6, and IL-8). The cytokine levels were measured using the R&D Elisa assay with antibodies specific for porcine cytokines.
RESULTS: Our pilot study found a hyperbolic elevation of PMNs over time from an average of 10% at 0 hour, to 89% at 6 hours. The PMNs in the lavage fluid were significantly elevated at 4 and 6 hours (p>0.001). The protein content in the lavage had a similar trend over 6 hours. Cytokines were measureable in the lavage fluid without the need for concentration. All of the cytokines increased with the duration of intubation. Lavage levels of IL-1 beta, IL-6 and IL-8 were significantly elevated at 6 hours (see Figure). Plasma cytokines were also measured and no detectable levels were observed. The PMNs in the lavage were highly correlated with the levels of IL-8 (R-squared = 0.83).
CONCLUSION: Our study shows a broad range of inflammatory markers released in response to uncomplicated endotracheal intubation. We consistently found elevated PMNs and proteins in the peritracheal area indicating inflammation. The increase in cytokines were most likely due to local events and not a result of systemic contamination.
CLINICAL IMPLICATIONS: A clear understanding of the local inflammatory process during endotracheal intubation is essential for improving the management of the intubated patient.
DISCLOSURE: Carlos Puyo, None.