The Effect of Routine vs. P.R.N. Post-operative Analgesia on Pulmonary Complications: A Multicenter Trial

Abstract

Significant pulmonary complications have been estimated to occur in 20 percent to 70 percent of patients following abdominal surgery (Lattimer, Dickman, Day, Gunn Schmidt, 1971). Atelectasis is the most frequent pulmonary complication occurring during the first 48 hours (Bartlett, Brennan, Gazzaniga & Hanson, 1973; Rigg, 1981; Wightman, 1968). The belief that the pathogenesis of atelectasis and pneumonia are the same (Coryllos and Birnbaum, 1929) and that unresolved atelectasis leads to lung infection (Guis, 1966; Henderson, 1929) suggests that any degree of atelectasis renders the patient at risk to develop further pulmonary pathology and an extended hospital stay. Herein lies the importance of the prevention of atelectasis in post-operative patients. A number of demographic, disease, life-style and treatment variables have been shown to influence the rate of development of atelectasis (Rigg, 1981). Any influence that improves underventilation in dependent lung regions is shown to increase this tendency. Hence, when the discomfort of an abdominal or thoracic incision inhibits inspiration, the abdominal pain induces voluntary and reflex muscle spasm, affecting primarily the abdominal muscles and the diaphragm. This leads to more rapid but shallow respirations, poorly expanding the lower lobes of the lungs (Pflug & Bonica, 1977). Secretions accumulate and when the entering gas does not exceed the closing volume of the alveoli, the alveoli begin to collapse. Paradoxically, excessive analgesic control of abdominal pain may also lead to hypoventila-tion and predispose the patient to pulmonary complications (Rigg, Vedig & Isley, 1981). A variety of medication regimes and routes of administration of medication have been studied in the attempt to resolve this dilemma (Egbert