Local anesthesia reduces the maximal skin vasodilation during iontophoresis of sodium nitroprusside and heating.
OBJECTIVE
To evaluate the effect of local anesthesia on the skin vasodilation induced by the iontophoresis of sodium nitroprusside and heating.


METHODS
Skin vascular reactivity, in response to iontophoresis of sodium nitroprusside (SNP), was evaluated at the forearm and foot in 13 neuropathic diabetic (DN) and 11 nonneuropathic diabetic (D) patients and 9 healthy, nondiabetic subjects who served as controls (C). The direct (DI) and nerve axon reflex-related (N-V) vasodilation were measured by using two single-point laser Doppler probes. The vasodilation in response to local warming was also assessed. A topical anesthetic was applied on the contralateral forearm and foot and all the measurements were repeated.


RESULTS
Dermal anesthesia resulted in a reduction of the direct vasodilation to SNP at the forearm [C: 58.1 +/- 16, D: 60.6 +/- 11%, and DN: 48.3 +/- 37% (postanesthesia percentage of reduction; mean +/- SEM), P<0.01] and at the foot in all three groups (D: 38.5 +/- 12%, P<0.01; C: 27.2 +/- 14% and DN: 11.3 +/- 17.5%, P=NS). The N-V related vasodilation was very low before and did not change after local anesthesia. The postanesthesia hyperemic response to warming was significantly reduced at low temperatures but did not change at 44 degrees C.


CONCLUSIONS
The sodium nitroprusside-related vasodilation is reduced after local anesthesia in a similar way in healthy subjects and diabetic patients with and without neuropathy. The response to heating is also reduced at low temperatures. This indicates a stabilizing effect of local anesthesia on the smooth muscle cell.
Caselli
Antonella
A
Joslin-Beth Israel Deaconess Foot Center, Department of Surgery, Microcirculation Laboratory, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
Uccioli
Luigi
L
Khaodhiar
Lalita
L
Veves
Aristidis
A
D000287:Administration, Topical; D000328:Adult; D000779:Anesthetics, Local / Q000494:pharmacology*; D003922:Diabetes Mellitus, Type 1 / Q000503:physiopathology; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology; D003929:Diabetic Neuropathies / Q000503:physiopathology; D005260:Female; D005542:Forearm / Q000098:blood supply; D006358:Hot Temperature; D006801:Humans; D007478:Iontophoresis; D017078:Laser-Doppler Flowmetry; D008297:Male; D008875:Middle Aged; D009599:Nitroprusside / Q000494:pharmacology*; D012867:Skin / Q000098:blood supply / Q000503:physiopathology; D014664:Vasodilation / Q000187:drug effects* / Q000502:physiology; D014665:Vasodilator Agents / Q000494:pharmacology*
D000779:Anesthetics, Local; D014665:Vasodilator Agents; D009599:Nitroprusside