Confounding effects of blood hemoglobin and hematocrit levels on flap perfusion measurement with the Oxygen-to-see (O2C) analysis system in microvascular head and neck reconstruction– a retrospective study

Table 5 Association between flap perfusion parameters and blood hematocrit levels

Variable	RFFF (n = 69)		ALTF (n = 31)		FFF (n = 25)
Variable	r	p-value	r	p-value	r	p-value
Intraoperative measurement
Flow (AU)
8 mm	0.231	0.056	0.140	0.452	0.068	0.748
2 mm	0.036	0.772	0.177	0.342	-0.145	0.489
Hemoglobin concentration (AU)
8 mm	0.175	0.150	-0.167	0.369	-0.276	0.182
2 mm	0.190	0.117	0.311	0.089	0.285	0.168
Hemoglobin oxygen saturation (%)
8 mm	0.011	0.931	0.040	0.832	-0.080	0.703
2 mm	0.080	0.513	0.304	0.096	-0.033	0.877
Postoperative measurement
Flow (AU)
8 mm	0.102	0.405	-0.021	0.909	0.172	0.411
2 mm	-0.035	0.776	-0.236	0.202	0.017	0.935
Hemoglobin concentration (AU)
8 mm	0.093	0.447	-0.153	0.412	0.340	0.096
2 mm	0.268	0.026*	0.246	0.183	0.159	0.448
Hemoglobin oxygen saturation (%)
8 mm	0.016	0.899	-0.128	0.491	-0.100	0.635
2 mm	0.088	0.473	0.072	0.701	0.066	0.754

Parameters are indicated as Spearman correlation coefficient (r) calculated between flap perfusion parameters (flow, hemoglobin concentration, hemoglobin oxygen saturation) at 8- and 2-mm tissue depth and blood hematocrit levels (separately described for patients reconstructed with a RFFF, ALTF or FFF); p-values corresponding to calculation of Spearman correlation coefficient; significant p-values are bold (*p = 0.036 upon adjustment for ischemia duration (min), mean arterial blood pressure (mmHg) and administered catecholamine dose (µg/min per kg) in multiple regression analysis); abbreviations: RFFF = radial free forearm flap, ALTF = anterolateral thigh flap, FFF = fibula free flap, AU = arbitrary units

ISSN: 1471-2482