• Joseph D Tobias, Louis Del Campo, Keith Kenter, Kelly Groeper, Bruce Gray, and James Edwards.
• Department of Anesthesiology, University of Missouri, Columbia, MO 65212, USA. tobiasj@health.missouri.edu
• South. Med. J. 2004 Jan 1;97(1):21-4.

BackgroundWe used transcutaneous (TC) carbon dioxide (CO2) monitoring to prospectively evaluate changes in respiratory status after interscalene anesthesia in 45 adults (40 successful and 5 unsuccessful blocks).MethodsTC-CO2 oxygen saturation and respiratory rate were recorded every minute for 5 minutes before block and every 2 minutes for a total of 30 minutes (15 data sets) after injection of the local anesthetic solution.ResultsAfter successful block, TC-CO2 increased from 41 +/- 5 mm Hg to a maximum value of 44 +/- 6 mm Hg (P < 0.0001) and the respiratory rate increased from 14 +/- 2 breaths/min to a maximum of 20 +/- 4 breaths/min (P < 0.001). The increase in TC-CO2 was > or = 5 mm Hg in 11 patients and > or = 10 mm Hg in 4 patients, with a maximum increase of 12 mm Hg. Of the 600 TC-CO2 data points recorded (15 each from the 40 patients with a successful block), 62 (10.3%) showed a TC-CO2 value of 50 mm Hg or greater, with a maximum value of 57 mm Hg. No significant change in TC-CO2 or respiratory rate was seen in the five patients with unsuccessful block.ConclusionAfter interscalene blockade, we found an increase in respiratory rate and hypercarbia that resulted in no clinically significant effect.

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