Frequency domain near-infrared spectroscopy technique in the assessment of brain oxygenation: a validation study in live subjects and cadavers.

BACKGROUND: Studies with continuous wave near infrared spectroscopy (CW-NIRS) have shown little difference in brain oxygenation of dead compared to live subjects. We determined brain oxyhemoglobin (OHb) and deoxyhemoglobin (HHb) concentrations in healthy volunteers and cadavers using frequency domain near infrared spectroscopy (FD-NIRS). METHODS: Regional OHb and HHb, brain oxygen saturation (SO2), and total hemoglobin (tHb) were determined. Nine patients who died in the hospital were evaluated by FD-NIRS in the morgue 7-96 h after death was confirmed. Ten volunteers served as a control group. RESULTS: Absolute concentrations of brain tissue OHb and HHb were 24.9 +/- 9.1 uM and 13.8 +/- 32 uM, respectively, in live subjects. In dead subjects, OHb was 1.3 +/- 2.1 uM and HHb was 30.8 +/- 14.4 uM (both P < 0.05 compared to live). OHb showed a 90% decrease within 7h of death. There was a significant trend for a continued decrease in OHb from 7 to 96 h. CONCLUSION: OHb decreased and HHb increased in dead patients compared to live volunteers. Depletion of OHb primarily occurred within 7 h of death but continued gradually over 96 h. FD-NIRS was a novel technique for determining OHb and HHb changes following death.

Correlation of Inflammation in Frozen Sections With Site of Nonmelanoma Skin Cancer.

IMPORTANCE: During Mohs micrographic surgery of nonmelanoma skin cancer (NMSC), inflammation in histologic frozen sections has been found to occasionally presage the detection of tumors in frozen sections of adjacent excision specimens. OBJECTIVE: To quantify the correlation between the location of inflammation without visible tumor in histologic frozen sections and the location of subsequently detected NMSC. DESIGN, SETTING, AND PARTICIPANTS: A retrospective cohort study of 3148 cases pertaining to frozen sections associated with the staged excision of NMSC was performed from September 8, 2008, to September 18, 2009, at an urban academic medical center, with the collected data analyzed on May 9, 2013. EXPOSURES: Consecutive cases of Mohs micrographic surgery performed at an academic medical center. MAIN OUTCOMES AND MEASURES: For each wedge-shaped tissue segment corresponding with 1 hour of time on a clock face, the proportion of patients with inflammation at the source location of the segment who subsequently had a tumor at this same location; the proportion of patients who had neither inflammation nor subsequent tumor at the source location of the segment; the probability of subsequent tumor at this location given the prior finding of inflammation at the same location; and the probability that a location was without tumor in the absence of preexisting inflammation at that location. RESULTS: Of the medical records of 3148 cases of NMSC that were reviewed, 60 showed inflammation in histologic frozen sections from an excision specimen that was followed by tumor in the subsequent excision specimen. Of these 60, 39 (65%) were b asal cel carcinoma and 21 (35%) were squamous cell carcinomas; 53 (88%) were Mohs stage 1. In 7 of 12 segments, a significant positive correlation was found between the presence of inflammation and the presence of nearby tumor with correlation coefficients ranging from 0.196 to 0.384 (P < .05) . The probability that tumor was absent when inflammation was not seen at a particular location (ie, clock-face segment) in preceding sections from that location was 91%, with segment-specific probability values ranging from 82% to 96%. CONCLUSIONS AND RELEVANCE: During Mohs micrographic surgery of NMSC with the examination of frozen sections, histologic inflammation is modestly predictive of adjacent tumor whereas lack of inflammation strongly predicts that no additional tumor will be found.