These INVOS® System graphs from real patient cases are a compelling way to see the true impact and value of cerebral/somatic monitoring. Each INVOS® System case graph reveals the patient's regional oxygen saturation (rSO2) values at each stage of surgery or critical care treatment, and its responses to events and interventions.
The following case graphs demonstrate how the INVOS® System can make a positive addition to patient care. Its objective, real-time and site-specific oxygenation data helps care teams react to oxygen imbalances, potentially reducing complications, including some potentially catastrophic in scale.
Optimizing rSO2 to Avert Potential Re-Operation
This case features a diabetic patient with extensive history and treatment for peripheral vascular disease. The surgical plan was to remove the left femoral stent and place a femoral to popliteal artery bypass graft. An attempt to remove the stent was unsuccessful because of extensive scar tissue. Alternatively, the surgeon decided to bypass the stent by placing the graft proximal to the stent and anastamosing it to the popliteal artery. The result was inadequate blood flow to the affected leg. This was observed by Doppler flow measurements and the INVOS® System oxygen trends. The surgeon then placed a cross over graft between the right femoral artery and left femoral to popliteal graft, increasing blood flow to the left leg. Once this second graft was complete, excellent blood flow was documented by both Doppler and the INVOS® System. This change in the surgical plan resulted in the patient's somatic rSO2 values improving in parallel with improved Doppler flow measurements, consistent with a successful outcome.
CEA Shunt Malfunction: Consequences to rSO2
The carotid shunt is one surgical method that secures cerebral blood flow during a carotid endarterectomy (CEA). The carotid shunt allows the blood to be rerouted around the operative site to the brain. However, shunts are not without complications. In this example, plaque disruption with shunt placement could potentially lead to cerebral embolism. When the shunt was inserted and opened in the left carotid, improvement in rSO2 measured by cerebral oximetry did not follow as expected. The surgeon used Doppler to measure blood flow in the shunt and check for kinks. The shunt was then manipulated until flow was restored. During this CEA, cerebral oximetry provided the surgeon with noninvasive, real-time measurement of cerebral oxygen changes during shunt placement and as it was manipulated.
rSO2 During a Change in Surgical Plan
Carotid endarterectomy (CEA) surgeons make their shunting decisions based on a variety of metrics. Here, the INVOS® System provided immediate information about a critical cerebral unilateral desaturation upon carotid clamping, potentially reflecting an incomplete Circle of Willis. This surgeon rarely shunted prior to using the INVOS® System for noninvasive cerebral oximetry. Beyond the angiogram, the only "metric" available to guide intraoperative decisions is observation of back bleeding after clamping with an open distal carotid vessel. On this day the back bleeding was poor. Within moments, the surgeon decided to shunt. The INVOS® System's rSO2 value was used to verify this patient's ability to perfuse the left side of this brain via the blood supply from the right hemisphere. Once identified by rSO2 trends that the right blood supply was insufficient for the left hemisphere oxygen levels, the shunt was placed. With the functional shunt in place, left sided rSO2 reflected an immediate increase in response to the established blood flow through the shunt. The CEA was completed successfully. The patient awoke in the OR without difficulty and moved all extremities on command.
Extremity Ischemia and Reperfusion
INVOS® System sensors were placed on the calf to monitor perfusion to the distal extremities while the patient's aorta was clamped during this aorto bifemoral bypass repair. As expected, rSO2 values desaturated in unison when the aorta was clamped. When the femoral clamps were removed, right leg rSO2 immediately returned to baseline, but left leg rSO2 only returned to 50. The surgeon used a Doppler that was audible on the new graft but the distal artery Doppler flow was faint. The surgeon explored the area and discovered the artery distal to the graft was damaged by the clamp. After reclamping and repairing the artery, suitable reperfusion was confirmed by left leg rSO2 returning to baseline. In this case, rSO2 values provided tangible data to help assess reperfusion in real-time, enabling the surgeon to address the complication intra-operatively. Without rSO2 readings, the patient would have gone into recovery with compromised limb perfusion and would have needed to return for a reoperation with all the associated risks and costs.
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