Continuous Oxygen Saturation Monitoring during Cardiac Catheterization in Adults: Results
The patient population had a mean age of 53 ±3 years (range, 21 to 83 years) and mean weight of 83 ± 3 kg. Nineteen patients were men, and ten were women. Eighteen patients (62 percent) had a history of smoking. Nineteen patients received sedation before or during catheterization (14 with diazepam [2 to 15 mg], two with morphine [3 to 9 mg], and three with combinations of diazepam and morphine). The mean duration of the procedure was 96 ±5 minutes. The baseline Sa02 was 96 ±0.4 percent (range, 93 to 100 percent). All patients had a decrease in Sa02 from baseline at some time during catheterization. The lowest Sa02 for the population was 90 ± 1 percent (range, 82 to 96 percent; p<0.01 compared to baseline). Decrease from baseline to lowest Sa02 was 6 ±0.5 percent (range, 2 to 11 percent). The time at which the lowest Sa02 occurred did not relate to any event during catheterization.
Of the 29 patients studied, 11 (38 percent) had a decrease in Sa02 to below 90 percent (Table 1). In these 11 patients, the Sa02 fell to a mean of 87±1 percent (range, 82 to 89 percent). The mean number of episodes of Sa02 below 90 percent among the 11 patients was 16 ± 7 (range, 1 to 86). The mean duration of these episodes was 53 ±25 seconds (range, 8 to 240 seconds). The longest cumulative time below Sa02 of 90 percent for any one patient was 40.58 minutes.
The minimum Sa02 for any patient was found by stepwise multiple regression analysis to be significantly related to the baseline Sa02 (p<0.01), the duration of the procedure (p<0.001), and end-diastolic volume (EDV) (p<0.01), according to the following regression equation: minimum Sa02 = 46.8 — 0.0580 (duration of procedure in minutes)-!-0.5362 (baseline SaO^-0.0159 (EDV in milliliters). This equation describes 69 percent of the variation in minimum Sa02. Other indices of left ventricular function, although related to minimum Sa02, were not independent predictors of minimum Sa02 because of their close correlation to end-diastolic volume. The patients age, sex, weight, hematocrit reading before catheterization, smoking history, extent of coronary artery or valvular heart disease, and dose of diazepam administered had no significant relationship to the minimum Sa02 (Table 2).
We evaluated patients for signs of congestive heart failure before catheterization. On physical examination before catheterization, five patients had evidence of right ventricular failure (peripheral edema, jugular venous distention, or hepatojugular reflux), while one patient had evidence of left ventricular failure (rales, S3, or abnormal chest x-ray film), and two patients had evidence of biventricular failure.
Table 1—Patients with Episodes cf Sa02<90%
PatientNo. |
No.Episodes
Sa02<90% |
LongestEpisode
Sa02<90% (min) |
Total Time Sa02<90% (min) |
BaselineSa02
(%) |
LowestSa02
(%) |
1 | 1 | 4.77 | 4.77 | 93 | 89 |
2 | 9 | 0.75 | 3.15 | 95 | 88 |
3 | 6 | 11.83 | 24.00 | 98 | 87 |
4 | 2 | 0.27 | 0.47 | 96 | 88 |
5 | 86 | 1.72 | 23.08 | 93 | 82 |
6 | 1 | 0.40 | 0.40 | 97 | 88 |
7 | 10 | 0.33 | 2.27 | 94 | 85 |
8 | 4 | 0.97 | 2.23 | 95 | 89 |
9 | 27 | 5.00 | 40.58 | 91 | 87 |
10 | 8 | 0.20 | 1.13 | 95 | 89 |
11 | 22 | 4.92 | 13.95 | 97 | 87 |
Mean ± SEM | 16 ±7 | 2.83± 1.08 | 10.55±4.01 | 95± 1 | 87 ± 1 |
Table 2—Determinants cf Minimum SaOt during Cardiac Catheterization
Regression Coefficient— Minimum Sa02 | |
Age | -0.228 |
Sex | 0.013 |
Weight | 0.023 |
Baseline Sa02 | 0.555 (p<.01)* |
Intraoperative diazepam (mg) | -0.165 |
Duration of procedure (min) | -0.661 (p<.001)* |
Number of diseased coronary arteries | 0.224 |
Valvular heart disease (yes/no) | -0.197 |
Symptoms of right ventricular failure (yes/no) | -0.248 |
Symptoms of left ventricular failure (yes/no) | -0.298 |
End-diastolic volume | -0.601 (p<.01)* |
Pulmonary artery diastolic pressure | -0.399 |
Pulmonary capillary wedge pressure | -0.372 |
Cardiac index | 0.193 |