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Effect of oxygen on postoperative cardiovascular response to exercise
M Kjaersgaard1, C Lie, T Bisgaard
1Department of Surgical Gastroenterology, Hvidovre University Hospital, Denmark.
Objective:
To evaluate the effect of supplemental oxygen on postoperative cardiovascular response to submaximal exercise.
Design:
Randomised, controlled study.
Setting:
University hospital, Denmark.
Subjects:
16 patients having major abdominal operations.
Interventions:
A submaximal exercise test (heart rate up to 120 min(-1)) done twice on the third day after operation. Patients were given either 100% oxygen (4 L min(-1)) or air (21% oxygen, 4 L min(-1)) 30 minutes before and during the test in randomised order. During the tests they were monitored with a Holter tape recorder and a pulse oximeter.
Main Outcome Measures:
Heart rate during exercise.
Results:
At similar workloads there were significantly lower heart rates (median decrease 3 min(-1)) during exercise tests with oxygen compared with air (p < 0.05). Holter monitoring showed signs of myocardial ischaemia in 6 patients in relation to exercise testing, 4 of them related to both tests, 2 of them only when breathing air. Signs of myocardial ischaemia disappeared when the exercise ended.
Conclusion:
During the late postoperative period supplementary oxygen reduced heart rate in response to exercise to the same degree as observed previously in non-surgical patients and surgical patients not taking exercise. These findings do not suggest that decreased peripheral tissue oxygenation is responsible for the impaired cardiovascular response to exercise in postoperative patients.