To the Editor
In 1989 we studied the questions about rebreathing and oxygenation during cataract surgery raised by your correspondents Drs. Shuput, Pollard, Shaw, and Mr. Simpson. (1)
We found that using an oxygen insufflating hoop gave the surgeon easy access to the eye and kept the drapes off the patients face. Oxygen at a flow rate of IOL. per minute was insufflated into the “tent” so formed. We then measured the PCO2 of the gas mixture under the drapes in 31 randomly selected patients. C02 accumulated in all 31 cases (mean +/- SD, 6.1 +/- 3.1 mm Hg). We did not measure arterial PCO2 and therefore do not know the clinical significance of this accumulation.
The fresh gas flow was reduced in a stepwise manner during the operation. One patient developed a headache as the fresh gas flow was reduced, and another patient exhibited PVCs. In both cases the experiment was abandoned, and the patients improved. All the patients remained fully saturated throughout. Reducing the oxygen flow below 10 L. per minute led to modest increases in C02 in the tent. At 5L. per minute the mean PCO2 was 10.1 +/- 3.2 mm. Hg. The application of suction at 8 to 10 L. per minute to the atmosphere in the tent resulted in only slight decreases in the C02 accumulation, ranging from 8 to 22%.
In an associated laboratory experiment, we found that paper drapes were permeable to C02 and plastic drapes were impermeable.
Gerald L. Zeitlin, M.D. Brigham and Women’s Hospital Boston, MA
- Zeitlin, GL, Hobin K, Platt J, Woitkoski N. Accumulation of C02 during eye surgery. J. Clin. Anesth., 1989; 1: 262-267.