High levels of IGF-1 predict difficult intubation of patients with acromegaly.

PURPOSE: To investigate the characteristics of difficult intubation and identify novel efficient predictors in patients with acromegaly.

METHODS: Patients with either untreated acromegaly or non-functional pituitary adenomas were enrolled. Patients with acromegaly underwent hormone assays, upper airway computed tomography and magnetic resonance imaging examinations and preoperative overnight polysomnography. The modified Mallampati classification, mouth opening, neck circumference, and neck extension were assessed, and the Cormack-Lehane grades and the time of tracheal intubation were recorded.

RESULTS: Patients with acromegaly had a higher incidence of difficult intubation (62.5%). The time of tracheal intubation was prolonged, the neck circumference was enlarged, and the neck extension was confined. In patients with acromegaly and difficult intubation, the insulin-like growth factor 1 levels and apnea/hypoxia index were significantly higher compared to patients without difficult intubation (1115.40 ± 253.73 vs. 791.67 ± 206.62 ng/ml, P = 0.020; 22.17 ± 23.25 vs. 2.47 ± 2.84, P = 0.026, respectively). The bilateral regression analysis revealed that high levels of insulin-like growth factor 1 were an independent risk factor for developing difficult intubation (p = 0.042, Exp B = 1.006). The modified Mallampati classification was positively correlated with apnea/hypoxia index and could be calculated using the following logarithmic equation: MMC = 0.2982 * ln (AHI) + 2.1836.

CONCLUSIONS: In patients with acromegaly, neck movement is confined, the time of tracheal intubation is prolonged, and the neck circumference is enlarged, and these patients suffer from an increased incidence of difficult intubation (62.5%) during anesthesia induction. The apnea/hypoxia index and insulin-like growth factor 1 levels are both increased in acromegalic patients with difficult intubation, and elevated insulin-like growth factor 1 levels are an independent risk factor of difficult intubation in acromegalic patients.