Pulmonary and circulatory reactions during total hip replacement surgery.

The pulmonary and circulatory reactions to insertion of the acetabular and of the femoral prosthesis were studied during total hip replacement surgery in 22 patients with osteoarthrosis. The patients were given lumbar epidural analgesia and were divided into two groups. One group of 15 awake patients breathed air spontaneously (group A). The other group of seven patinets received additional anaesthesia with controlled ventilation with air (group B). This permitted an evaluation of the influence of the ventilatory pattern on the pulmonary and circulatory reactions to the surgical events. The greatest alterations were observed following impaction of the femoral prosthesis. This event caused the following statistically significant changes in both groups: An increase in total pulmonary venous admixture (from a mean value of 6.8 to 12.2% in group A and from 8.2 to 10.5% in group B) and a decrease in arterial oxygen tension (group A: 80.3 to 71.5 mmHg; group B: 82.6 to 76.9 mmHg); an increase in pulmonary vascular resistance (group A: 122 to 155 dyn -s- cm-5; group B: 129 to 164 dyn -s- cm-5) and an increase in mean pulmonary arterial pressure (group A: 17.3 to 19.0 mmHg; group B: 21.8 to 24.4 mmHg). Furtheremore, within the first 2 min after impaction a distinct transient rise in mean pulmonary arterial pressure by 2-4 mmHg was noted in a few patients, and in many patients the mean systemic arterial pressure decreased by 5 mmHg or more. No significant changes were found in cardiac output, pulmonary capillary wedge pressure, oxygen uptake, mixed venous oxygen tension, acid-base values, ratio of total dead space to tidal volume, or total airway resistance. The above findings indicate a tendency to pulmonary vascular and peripheral airway constriction leading to transient ventilation/perfusion disturbances and a decrease in arterial oxygen tension, and peripheral vasodilatation leading to a transient decrease in systemic arterial pressure.