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Mayeur C, Campard S, Richard C, Teboul JL. Int Care Med. 2009;35(Suppl 1):S81.
Introduction: A recently commercialised near infrared spectrometry (NIRS) device provides the continuous measurement of the haemoglobin saturation in the terminal vascularisation within tissues (StO2) of thenar eminence. Changes in StO2 can be monitored during a vascular occlusion test (VOT) aimed at detecting microcirculatory disturbances. The VOT consists of performing a transient occlusion of the upstream arterial circulation (ischemic phase) and then a release of the arterial occlusion (hyperaemic phase). The StO2 recovery slope has been shown to be a better prognostic factor than the baseline StO2 in septic shock. However, there is no consensual way to perform the VOT in terms of location of the cuff (arm or forearm) and of duration of the arterial occlusion. Standardisation of the technique is needed. In this study we compared the data provided by four VOTs used in the literature in the aim to determine the more relevant VOT.
Methods: We enrolled healthy volunteers and septic shock patients. In each subject, we performed four different VOTs in a random order using the InSpectra StO2 650 monitor (Hutchinson, MN). The cuff was inflated to 220 mmHg. Arm (A) or forearm (FA) occlusion was maintained until StO2 decreased to 40% (VOTA40% and VOTFA40%) or lasted 3 min (VOTA3min and VOTFA3min). The recovery slope was calculated off-line by InSpectra Analysis Program V4.00.
Results: We included 14 healthy volunteers (27 ± 4 years) with a baseline StO2 of 81 ± 4% and 18 septic shock patients (61 ± 14 years) with a baseline StO2 of 79 ± 10%. In septic shock patients, SAPS 2 was 58 ± 16, mean arterial pressure was 76 ± 13 mmHg (94% received norepinephrine) and mortality was 50%.
[HEALTHY VOLUNTEERS VALUES]
|
VOTA40% |
VOTA3 min |
VOTFA40% |
VOTFA3 min | |
|
Recovery slope (%/s), mean (range) |
5.4 (3.8-7.3) |
4.5 (2.6-6.6) |
6.3 (4.6-7.9) |
4.8 (1.3-6.3) |
|
Duration of occlusion (min), mean ± SD |
4.2 ± 0.8 |
3.0 ± 0.0 |
4.9 ± 0.8 |
3.0 ± 0.0 |
|
Minimal StO2 (%), mean ± SD |
40 ± 0 |
53 ± 6 |
40 ± 0 |
55 ± 6 |
SAPTIC SHOCK PATIENTS VALUE
|
VOTA40% |
VOTA3 min |
VOTFA40% |
VOTFA3 min | |
|
Recovery slope (%/s), mean (range) |
2.5 (0.4-5.6) |
2.2 (0.4-5.3) |
2.8 (0.7-5.7) |
2.2 (0.3-4.9) |
|
Number of patients within the normal range, n (%) |
2 (11) |
6 (33) |
1 (5) |
12 (67) |
|
Duration of occlusion (min), mean ± SD |
5.4 ± 2.8 |
3.0 ± 0.0 |
6.7 ± 3.9 |
3.0 ± 0.0 |
|
Minimal StO2 (%), mean ± SD |
40 ± 0 |
52 ±14 |
40 ± 0 |
54 ± 13 |
As expected, all septic shock patients, except one (for the VOTFA40%) and two (for the VOTA40%) had a recovery slope lower than normal when StO2 decreased to 40% during arterial occlusion. By contrast, when occlusion lasted 3 min, many patients including patients who eventually died, were misclassified since their recovery slopes were in the normal range. These results could be due to the smaller decrease of StO2 and in turn a less strong hyperemic response when ischemia lasted only 3 min. Additionally, a significantly (p<0.03) shorter time to reach 40% was required when arm (compared to forearm) occlusion was performed.
Conclusion: When a VOT is required for assessing microcirculatory disturbances in septic shock, we recommend performing it using an arm occlusion until StO2 reach 40%.