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Effects of rapid repetition of a vascular occlusion test on near-infrared spectroscopy-derived variables in healthy subjects and in critically ill patients

Introduction

Transient ischemia modifies cellular metabolism and microvascular physiology in order to limit damage from future hypoxic episodes, a phenomenon called preconditioning. Near-infrared spectroscopy (NIRS) is a non-invasive technique that, when coupled to a vascular occlusion test (VOT), provides an indirect measurement of muscle oxygen consumption (VO2) and microvascular reactivity. We hypothesized that: rapid repetition of a VOT may alter VOT-induced NIRS-derived variables and these changes could reflect preconditioning; and these alterations would be different in healthy volunteers and critically ill patients.

Methods

Continuous non-invasive measurements of thenar tissue oxygen saturation (StO2) were performed using NIRS technology (InSpectra 650; Hutchinson, USA). VOTs were performed by inflating a cuff to 50 mmHg above the systolic pressure for 3 minutes. In a group of healthy volunteers, the VOT was repeated after 5 minutes on day 1, after 15 minutes on day 2 and after 30 minutes on day 3. In a group of critically ill patients, the VOT was repeated after 5 minutes. For each VOT, we calculated the StO2 desaturation slope (DescSlope), StO2 resaturation slope (AscSlope) and the NIRS VO2 as the DescSlope×mean total hemoglobin index over the occlusion time. All statistical analyses were performed using SPSS 19.0 (IBM, USA).

Results

Twenty-one healthy volunteers (age 29 ± 6 years, heart rate 71 ± 6 bpm, mean arterial pressure 82 ± 6 mmHg) and 18 critically ill patients (age 59 ± 14 years, APACHE II score 21 ± 9, norepinephrine use in 10/18, ICU mortality 22%) were included. In the healthy volunteers, repetition of the VOT was associated with a decrease in the DescSlope and in NIRS VO2. This effect was not observed in the critically ill patients (Tables 1 and 2).

Table 1 Effects of a repeat VOT on VOT-induced NIRS-derived variables in healthy volunteers
Table 2 Effects of a repeat VOT on VOT-induced NIRS-derived variables in critically ill patients

Conclusion

Rapid repetition of a VOT alters VOT-induced NIRS-derived variables in healthy volunteers but not in critically ill patients. If these alterations reflect preconditioning, our results suggest that this phenomenon may be altered in critically ill patients.

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Correspondence to DO Cortes.

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Cortes, D., Puflea, F., Donadello, K. et al. Effects of rapid repetition of a vascular occlusion test on near-infrared spectroscopy-derived variables in healthy subjects and in critically ill patients. Crit Care 17, P2 (2013). https://doi.org/10.1186/cc12618

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Keywords

  • Healthy Volunteer
  • Muscle Oxygen
  • Occlusion Time
  • Vascular Occlusion Test
  • Tissue Oxygen Saturation