Local application of volatile anesthetics attenuates the response to a mechanical stimulus in humans.
OBJECTIVE
Volatile anesthetics may cause local hyperalgesia and/or analgesia. This double-blind randomized study investigated the effect of these medications when applied locally on the response to a mechanical stimulus.


METHODS
In experiment 1, standard commercial preparations of halothane 1 mL, isoflurane 1.5 mL and sevoflurane 2.7 mL were randomly applied on the forearm of 30 volunteers for 30 min, after which the response to a mechanical stimulus was recorded. The other forearm received water as control. The next day, the experiment for each anesthetic was repeated in a reverse fashion. Thirty minutes after the application, the response to a standardized mechanical stimulus was recorded. In experiments 2 and 3, the response to the same mechanical stimulus was tested after local applications of 2, 4, and 6 mL of halothane or after a local application of 5 mL sevoflurane respectively.


RESULTS
Low doses of the three anesthetics did not alter the response to the mechanical stimulus (F = 3.055, df = 1,174, P = 0.082). Two, 4, and 6 mL of halothane attenuated the response to the mechanical stimulus by 36%, 27% and 29% respectively (F = 9.586, df = 1,114, P = 0.002). Five millilitres of sevoflurane attenuated the response to the mechanical stimulus by 36% (F = 5.111, df = 19, P < 0.001).


CONCLUSIONS
Low liquid volumes of volatile anesthetics, when applied locally to the skin, did not influence the response to a mechanical stimulus, but higher volumes attenuated this response.
Fassoulaki
Argyro
A
Department of Anesthesiology, Aretaieio Hospital, Medical School, University of Athens, Greece. fassoula@aretaieio.uoa.gr
Skouteri
Ioanna
I
Siafaka
Ioanna
I
Sarantopoulos
Constantine
C
D000287:Administration, Topical; D000328:Adult; D018685:Anesthetics, Inhalation / Q000008:administration & dosage* / Q000494:pharmacology*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D005542:Forearm / Q000502:physiology; D006221:Halothane / Q000008:administration & dosage / Q000494:pharmacology; D006801:Humans; D007530:Isoflurane / Q000008:administration & dosage / Q000494:pharmacology; D008297:Male; D008738:Methyl Ethers / Q000008:administration & dosage / Q000494:pharmacology; D010147:Pain Measurement / Q000187:drug effects*; D017288:Pain Threshold / Q000187:drug effects*; D010812:Physical Stimulation; D000077149:Sevoflurane
D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane; D007530:Isoflurane; D006221:Halothane