Power spectral analysis of the effects of epinephrine, norepinephrine, dobutamine and dopexamine on microcirculation following free tissue transfer.
BACKGROUND
The use of pressor drugs after microsurgical free tissue transfer remains controversial because of potential vasoconstrictor effects on the free flap. Noninvasive monitoring of free flaps with laser Doppler flowmetry may provide further information regarding the local regulation of blood flow in the flap tissues during pressor infusions. This study evaluated the effects of four commonly used pressor agents.


METHODS
Twenty four patients (25 data sets) undergoing head and neck cancer resection and free flap reconstruction were recruited. Epinephrine, norepinephrine, dopexamine, and dobutamine were infused in a random order at four infusion rates, after surgery, with free flap and control area (deltoid region) laser Doppler skin blood flow monitoring. Frequency analysis of the Doppler waveform was performed utilizing the time period immediately before the first drug infusion for each patient as baseline.


RESULTS
At baseline there was less power at the 0.002-0.6 Hz frequency in the flap compared with control tissue consistent with surgical denervation. At maximum epinephrine infusion rates, the control of blood flow moved toward (i.e., proportion of power increased in) the lower frequencies, as smooth muscle mediated (myogenic) control began to dominate blood flow, an effect most marked with norepinephrine. Dobutamine and dopexamine had little effect on control of blood flow.


CONCLUSIONS
Denervation of free flap tissue is demonstrable using spectral analysis of laser Doppler blood flow signals. With norepinephrine the control of blood flow shifts toward low frequency vasomotion where blood flow depends mostly on average blood pressure, making it potentially the most suitable agent following free tissue transfer.
Nuffield Department of Surgical Sciences, University of Oxford, John Radcliffe Hospital, Headley Way, Oxford OX3 9DU. Karen.a.eley@gmail.com
Karen A
KA
Eley
John Duncan
JD
Young
Stephen R
SR
Watt-Smith
D004280:Dobutamine / Q000008:administration & dosage / Q000494:pharmacology*; D004298:Dopamine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D004334:Drug Administration Schedule; D004837:Epinephrine / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D058752:Free Tissue Flaps / Q000098:blood supply* / Q000294:innervation / Q000637:transplantation; D006258:Head and Neck Neoplasms / Q000601:surgery; D006801:Humans; D007262:Infusions, Intravenous; D017078:Laser-Doppler Flowmetry; D008297:Male; D008833:Microcirculation / Q000187:drug effects*; D009638:Norepinephrine / Q000008:administration & dosage / Q000494:pharmacology*; D019651:Plastic Surgery Procedures / Q000379:methods; D013057:Spectrum Analysis; D014662:Vasoconstrictor Agents / Q000008:administration & dosage / Q000494:pharmacology*
D014662:Vasoconstrictor Agents; C046318:dopexamine; D004280:Dobutamine; D004298:Dopamine; D009638:Norepinephrine; D004837:Epinephrine