Date of Award


Document Type

Open Access Thesis

Degree Name

Medical Doctor (MD)

First Advisor

Douglas A Ross MD

Second Advisor

Clarence T Sasaki


CAPILLARY BLOOD GAS MEASUREMENT AS A NOVEL MEANS OF ASSESSING FLAP PERFUSION IN FREE TISSUE TRANSFER. Aaron K. Remenschneider and Douglas A. Ross (Sponsored by Dr. Clarence Sasaki). Section of Otolaryngology, Department of Surgery, Yale University, School of Medicine, New Haven, CT. To demonstrate that in comparison to implantable O2 microelectrodes, Capillary Blood Gas measurements represent a reliable, accessible and easy method of identifying failing free flaps, and furthermore, to assess post-operative free-flap monitoring techniques nation-wide, determining the openness of surgeons to new surveillance modalities. Groin fasciocutaneous flaps were elevated in 10 rats and following arterial or venous occlusion, oxygen microelectrode measurements (pO2 and flow) and Capillary Blood Gas measurements (pO2, pCO2, pH, HCO3) were obtained at 0, 10 and 20 minutes. A nine question, Internet based survey on post-operative flap surveillance techniques was sent to the personal email addresses of 238 microvascular surgeons from around the country. Response data were collected and analyzed utilizing an online resource. Measurements with capillary blood gas paralleled measurements with O2 microelectrodes. Average capillary blood gas pO2 fell from 42.72 mm Hg at 10 minutes and then to 28.67 mm Hg at 20 minutes. Average pH fell from 7.38 to 7.33 at 10 minutes and to 7.30 at 20 minutes. Results were statistically significant with both the paired Students t test and the Wilcoxon signed rank test. 75% of survey respondents indicated that clinical assessment was more important than available adjunctive tests in the decision to re-explore the vascular pedicle in a threatened free flap and 56% listed pinprick with flap bleeding as an important marker of flap health in their practice. 90% of respondents indicated they are open to new quantitative monitoring techniques. While providing users the ability to simultaneously monitor accepted modalities of flap surveillance, pH and pO2, the capillary blood gas is a reliable and reproducible marker of flap tissue health. Given that no single monitoring modality enjoys a clear preference among microvascular surgeons and that more than half of these surgeons already utilize pinprick assessment of the flap, this study demonstrates that the capillary blood gas may be well positioned for further study in humans.