Objective: To determine and compare the concentration of gentamicin in the lower airways and serum of healthy spontaneously breathing dogs after nebulization with 5% undiluted gentamicin during 3 versus 10 minutes.
Animals: 10 healthy experimental Beagles.
Methods: This was a prospective crossover study. A standardized bronchoalveolar lavage (BAL) procedure was performed in each dog after 1 week of administration of each of 2 different gentamicin nebulization protocols separated by a 1-week washout period. The 2 protocols consisted of nebulization of 5% undiluted gentamicin (50 mg/mL) twice daily either during 10 minutes per session (± 95 mg; 10-minute protocol) or 3 minutes per session (± 28 mg; 3-minute protocol). BAL fluid (BALF) was obtained under general anesthesia using a bronchoscope within 15 minutes after administration of the last nebulization. Blood was collected within 5 minutes after BALF collection. BALF and serum gentamicin concentrations were determined by particle-enhanced turbidimetric inhibition immunoassay. Concentrations between protocols were compared using a paired t test.
Results: Both BALF and serum gentamicin concentrations were higher after the 10-minute protocol compared with the 3-minute protocol (mean ± SD: 2.41 ± 0.87 mg/L vs 1.25 ± 0.31 mg/L, P = .001; and 1.02 ± 0.59 mg/L vs 0.31 ± 0.24 mg/L, P < .0001 in BALF and serum, respectively), while the BALF-to-serum ratio did not differ between the protocols (3.75 [1.37 to 5.75] (median [IQR]) in the 3-minute protocol vs 2.48 [2.02 to 2.67] in the 10-minute protocol; P = .754).
Clinical relevance: A 3-minute nebulization of gentamicin seems to achieve sufficient concentrations of gentamicin in the BALF to have good efficacy against aminoglycoside-sensitive bacteria while remaining below the toxic range values in blood.
Keywords: bronchoalveolar lavage; nebulization; small animal respiratory tract.