Changes in transcutaneous carbon dioxide, oxygen saturation, and respiratory rate after interscalene block.
BACKGROUND
We 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).


METHODS
TC-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.


RESULTS
After 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.


CONCLUSIONS
After interscalene blockade, we found an increase in respiratory rate and hypercarbia that resulted in no clinically significant effect.
Tobias
Joseph D
JD
Department of Anesthesiology, University of Missouri, Columbia, MO 65212, USA. tobiasj@health.missouri.edu
Del Campo
Louis
L
Kenter
Keith
K
Groeper
Kelly
K
Gray
Bruce
B
Edwards
James
J
D000577:Amides / Q000494:pharmacology; D000701:Analgesics, Opioid / Q000627:therapeutic use; D000779:Anesthetics, Local / Q000494:pharmacology; D001132:Arm / Q000601:surgery; D001785:Blood Gas Monitoring, Transcutaneous; D001917:Brachial Plexus; D002045:Bupivacaine / Q000031:analogs & derivatives / Q000494:pharmacology; D005260:Female; D005283:Fentanyl / Q000627:therapeutic use; D006801:Humans; D006993:Hypnotics and Sedatives / Q000627:therapeutic use; D000077554:Levobupivacaine; D008012:Lidocaine / Q000494:pharmacology; D008297:Male; D008874:Midazolam / Q000627:therapeutic use; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods*; D011446:Prospective Studies; D015656:Respiratory Mechanics / Q000187:drug effects*; D000077212:Ropivacaine; D012782:Shoulder / Q000601:surgery
D000577:Amides; D000701:Analgesics, Opioid; D000779:Anesthetics, Local; D006993:Hypnotics and Sedatives; D000077212:Ropivacaine; D008012:Lidocaine; D000077554:Levobupivacaine; D008874:Midazolam; D005283:Fentanyl; D002045:Bupivacaine