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Targets, Thresholds and Interventions

Adult rSO2 Targets and Thresholds

Using the INVOS® System, you can immediately detect rises and falls in rSO2 and intervene to help avoid potentially serious or fatal complications. Targets and thresholds1-4 are expressed in rSO2 numerical values and percent changes from baseline. With each patient serving as his/her own control, you can more easily customize your clinical decisions based on your patient's unique physiology and clinical situation.
  • Healthy Cerebral rSO2: 58 - 82 points
  • Intervention Threshold: <50 points (or ~20% from baseline)
  • Critical Threshold: <40 points (or ~25% from baseline)

rSO2 Reactions to Common Intra-op Events


Edmonds HL Jr, et al. Semin Cardiothorac Vasc Anesth 2004;8:147-66.
This aortic arch reconstruction with deep hypothermic circulatory arrest demonstrates common times when cerebral perfusion can be impacted both positively and negatively. Adequate rSO2 levels can provide confidence that the brain is well perfused, while dips in rSO2 near or past the patient's desaturation threshold indicate opportunities for therapeutic interventions.

Clinically Significant Declines

Cerebral declines in rSO2 below 50 or more than 20 percent from a patient's baseline are cause for concern and initiation of interventions. Clinical studies have shown that rSO2 values below 40 or declines of more than 25 percent from baseline are associated with neurologic dysfunction and other adverse outcomes.

The area under the curve (AUC), as indicated in red, calculates the cumulative time and depth below the 75% of baseline threshold. High AUC has been correlated with poor outcomes.

Graph Footnotes:
Edmonds HL Jr, et al. Semin Cardiothorac Vasc Anesth. 2004 Jun;8(2):147-66; Alexander HC, et al. Ann Thorac Surg 2002;73 373-C; Cho H, et al. J Neurosurg. 1998 Oct;89(4):533-8; Iglesias I, et al. Heart Surgery Forum 2003;6:204; Edmonds, HL Jr, et al. J Interv Cardiolog 1998;11:197-204; Yao FSF, et al. Anesthesiology 2001;95:A-152; Roberts KW, et al. Anesthesiology 1998;89:A934; Higami T, et al. Ann Thorac Surg 1999;67:1091-6; Singer I, et al. Pacing Clin Electrophysiol. 1999 Jan;22(1 Pt 2):216-22.

OR Interventions to Improve rSO2

rSO2 may be affected by a host of variables. Some may include mechanical issues, body positioning, muscular activity, circulating blood volume, cardiac function, peripheral vascular resistance, circulating hormones and venous pressure. While protocols vary by institution, the following interventions1-4 are used to improve rSO2 in the operating room.

Rule Out Mechanical Cause
  • Head position
  • Cannula position

Decrease O2 Demand (cerebral metabolism)
  • Increase anesthetic
  • Decrease temperature

Increase O2 Supply (oxygen delivery)
  • Increase cardiac output (or pump flow)
  • Increase blood pressure
  • Increase CO2 to physiologic level
  • Increase FiO2
  • Vasodilate cerebral blood vessels
  • Increase hematocrit

Footnotes:
1. Murkin et al. Anesth Analg 2007;104:51-58.
2. Yao FSF, et al. Anesthesiology 2001;95:A-152.
3. Edmonds HL Jr, et al. Semin Cardiothorac Vasc Anesth 2004;8:147-66.
4. Casati A, et al. Anesth Analg 2005;101:740.