Tourniquet-induced tissue hypoxia characterized by near-infrared spectroscopy during ankle surgery: an observational study

Table 3 Association of representative variables of tissue oxygenation with variables of resaturation and hyperemia following tourniquet deflation (n = 26)

Variable	Resaturation magnitude (∆T_post-end)		Resaturation rate (%/second)		Hyperemic response (∆T_post-0)
Variable	R value	P value	R value	P value	R value	P value
Baseline oxygenation (T₀)	0.02	0.92	−0.01	0.95	−0.87	< 0.001
Maximal hypoxia (T_end)	−0.94	< 0.001	0.43	0.03	−0.19	0.34
Hypoxic duration	0.26	0.20	−0.17	0.41	0.41	0.04
Hypoxic load (AUC)	0.66	< 0.001	−0.08	0.70	0.09	0.68

T₀ = immediately before tourniquet insufflation; T_end = immediately before tourniquet deflation; T_post = 3–5 min after tourniquet deflation. ∆T_post-end = difference between tissue oxygenation immediately before and after tourniquet deflation; ∆T_post-0 = difference between tissue oxygenation immediately after tourniquet deflation and before tourniquet inflation (baseline); AUC = area under curve

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