Using a monitored test to assess risk of aspiration in postoperative patients

Incidence of and risk factors for postoperative pneumonia in dogs anesthetized for diagnosis or treatment of intervertebral disk disease

OBJECTIVE

To determine incidence of and risk factors for postoperative pneumonia in dogs anesthetized for diagnosis or treatment of intervertebral disk disease (IVDD).

DESIGN

Retrospective case-control study.

ANIMALS

707 dogs that underwent general anesthesia for the diagnosis or treatment of IVDD between 1992 and 1996 or between 2002 and 2006.

PROCEDURES

Postoperative pneumonia was diagnosed if compatible clinical signs (cough or hypoxemia) and radiographic abnormalities (alveolar infiltrates) developed within 48 hours after anesthesia. To identify risk factors for postoperative pneumonia, findings for dogs that developed postoperative pneumonia between 2002 and 2006 were compared with findings for a randomly selected control group of unaffected dogs from the same population.

RESULTS

There were no significant differences in age, breed, body weight, sex, location of IVDD, or survival rate between the 2 time periods, but there were significant differences in the use of magnetic resonance imaging, computed tomography, and hemilaminectomy and in the percentage of dogs that developed postoperative pneumonia in the later (4.6%) versus the earlier (0.6%) years. Significant risk factors for postoperative pneumonia included preanesthetic tetraparesis, cervical lesions, undergoing magnetic resonance imaging, undergoing > 1 anesthetic procedure, longer duration of anesthesia, and postanesthetic vomiting or regurgitation.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that at this institution, the incidence of postoperative pneumonia in dogs anesthetized for diagnosis or treatment of IVDD had increased in recent years.

Role of pathogenic oral flora in postoperative pneumonia following brain surgery

BACKGROUND

Post-operative pulmonary infection often appears to result from aspiration of pathogens colonizing the oral cavity. It was hypothesized that impaired periodontal status and pathogenic oral bacteria significantly contribute to development of aspiration pneumonia following neurosurgical operations. Further, the prophylactic effects of a single dose preoperative cefazolin on the oral bacteria were investigated.

METHODS

A matched cohort of 18 patients without postoperative lung complications was compared to 5 patients who developed pneumonia within 48 hours after brain surgery. Patients waiting for elective operation of a single brain tumor underwent dental examination and saliva collection before surgery. Bacteria from saliva cultures were isolated and periodontal disease was scored according to type and severity. Patients received 15 mg/kg cefazolin intravenously at the beginning of surgery. Serum, saliva and bronchial secretion were collected promptly after the operation. The minimal inhibitory concentrations of cefazolin regarding the isolated bacteria were determined. The actual antibiotic concentrations in serum, saliva and bronchial secretion were measured by capillary electrophoresis upon completion of surgery. Bacteria were isolated again from the sputum of postoperative pneumonia patients.

RESULTS

The number and severity of coexisting periodontal diseases were significantly greater in patients with postoperative pneumonia in comparison to the control group (p = 0.031 and p = 0.002, respectively). The relative risk of developing postoperative pneumonia in high periodontal score patients was 3.5 greater than in patients who had low periodontal score (p < 0.0001). Cefazolin concentration in saliva and bronchial secretion remained below detectable levels in every patient.

CONCLUSION

Presence of multiple periodontal diseases and pathogenic bacteria in the saliva are important predisposing factors of postoperative aspiration pneumonia in patients after brain surgery. The low penetration rate of cefazolin into the saliva indicates that its prophylactic administration may not be sufficient to prevent postoperative aspiration pneumonia. Our study suggests that dental examination may be warranted in order to identify patients at high risk of developing postoperative respiratory infections.