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Key Study Findings - Vascular

The following Key Study Findings are just a sample of the more than 600 compelling clinical presentations, study abstracts and published papers documenting INVOS® System benefits.

To see the full bibliography, please visit Clinical Evidence.

Optimized Assessment of Dysoxygenation in CEA


Stump pressure (SP) has historically been used for assessing ischemic risk during carotid endarterectomy (CEA). Study authors state, "These findings suggest that cerebral oximetry can be used as an alternative to carotid stump pressure to provide noninvasive, inexpensive and continuous real-time monitoring during CEA."
  • rSO2 was measured continuously on 36 CEA patients prior to clamping (t1) and immediately after clamping but before shunt placement (t2).
  • rSO2 values on the operated side revealed a statistically significant change when comparing t1 and t2. The mean change in rSO2 was 6.03 ± 7.93 (p<0.00001 vs. preclamp value).
  • The drop in rSO2 that occurs after clamping on the operated side correlates significantly with changes in stump pressure.

The investigators state that cerebral oximetry (INVOS® System) is valuable in monitoring perfusion during shunting in order to alert the surgeon to possible shunt malfunction or inadequate placement.

Footnote:
Lee TS, Ann Vasc Surg 2007. DOI 10.1016j.avsg.2007.07.022.

Reliability of Monitors during CEAs

AUC represents the probability that a randomly selected subject will have correct prediction of ischemia.

The reliability of four cerebral monitoring systems was compared in detecting cerebral ischemia, defined as obvious neurologic change, during awake carotid endarterectomy (CEA). The study found that:
  • Transcranial Doppler Sonography (TCD), near-infrared spectroscopy (NIRS) and stump pressure (SP) measurement provide statistically similar accuracy for the detection of cerebral ischemia during carotid surgery.
  • The performance of somatosensory evoked potentials (SEP) was significantly poorer.
  • Due to technical difficulties, TCD and SEP were unable to be performed on 21% and 4% of patients respectively, making them unreliable in a portion of the population.
  • SP and NIRS (INVOS® System) were possible in all patients, prompting investigators to state that the use of NIRS and/or SP "might be superior in clinical practice."

Footnote:
Moritz et al. Anesthesiology 2007;107:563-9.

Monitoring of Limb Ischemia



(A) Occlusion of right aortofemoral graft owing to thrombus. (B) Right femoral arterial clamp. (C) Release of right femoral arterial clamp after thrombectomy of right aortofemoral graft. (D) Left femoral arterial clamp. (E) Release of left femoral arterial clamp after grafting of left aortofemoral bypass.

A patient scheduled for reconstructive surgery on an occluded left aortofemoral bypass graft was monitored bilaterally with INVOS® System sensors placed on right and left calf muscles. NIRS monitoring was used to provide detection of acute limb ischemia and assess the effectiveness of revascularization procedures.
  • A sharp decline in the right rSO2 indicated a perfusion problem, which was caused by a large thrombus blocking the right graft.
  • After successfully removing the blockage and clamp, rSO2 returned to its original level.
  • The INVOS® System provided an early warning of acute limb ischemia that may have gone unnoticed since it occurred in the contralateral leg.

Footnote:
Nakayama M, et al J Cardiothorac Vasc Anesth. 2001 Oct15(5):624-5.