Patients undergoing coronary artery bypass graft (CABG) surgeries face a lot of potential challenges. Risk of cardiovascular events, stroke, sepsis, excessive bleeding, and respiratory failure are just a few of the intra and post operative complications associated with CABG surgeries.[1]
Cerebral desaturation is another complication that can occur in nearly six out of every ten CABG or valve surgeries performed.[2] Neurological events including stroke can happen when prolonged cerebral desaturation occurs and this risk is higher among bypass patients, especially when it involves aortic surgery.[3]
Additionally, many of the strokes that occur happen in patients who had a low to medium preoperative risk making them difficult to predict. It also suggests that these events may have the potential to be prevented with adequate monitoring in place intraoperatively.3
Regional oximetry allows clinicians to assess real time cerebral tissue oxygenation continuously during surgery to inform interventions and improve patient outcomes. Today’s article reviews regional oximetry and how this noninvasive monitoring practice improves patient outcomes, particularly in patients undergoing CABG and other cardiac procedures.
What is Regional Oximetry?
Measuring tissue oxygenation in real time wasn’t always possible but now, surgical teams can capture regional tissue oxygenation, including cerebral tissue oxygenation. Near-infrared spectroscopy (NIRS) is noninvasive and allows for continuous monitoring of cerebral tissue oxygenation.3
Baseline readings are measured prior to surgery and changes from baseline are often used to trigger interventions to support oxygenation.
Obtaining a baseline cerebral oxygenation value is key as cardiac surgery patients tend to have lower values prior to surgery. In addition to capturing cerebral oxygenation, NIRS regional oximetry readings can provide an overview of a patient’s cardiopulmonary function as well as their systemic oxygen needs.3
Regional oximetry monitoring is noninvasive and typically involves applying adhesive pads to the patient’s scalp, typically over the frontal lobe.3
There are different practices when it comes to deciding when to intervene based on regional oximetry readings. A couple of parameters include if the rSO2 value drops to 50% or is a 20% or greater drop from baseline, then clinicians may consider intervening.3
Interventions Improve Patient Outcomes
Cerebral desaturation can lead to poor patient outcomes and increased postoperative complications and costs.2 In a multicenter pilot study, researchers found that 61% of patients undergoing CABG or valve surgery experience a cerebral desaturation event which was defined as an rSO2 decrease of greater than 20% from the patient’s baseline.2 Not only that, nearly 75% of patients who experienced a cerebral desaturation event had more than one event during surgery.
10% of those events were not detected by clinicians highlighting the importance of monitoring systems to alert clinicians so interventions can be implemented in a timely manner.2
This high incidence of cerebral desaturation events means interventions to help detect and manage these events is critical in this patient population. Thankfully, research also shows interventions involving regional oximetry can help. Cognitive decline may be reduced, intensive care unit (ICU) stays are reduced, and major organ morbidity and mortality may be reduced.[4],[5]
A study of 200 patients found when the INVOS™ technology was used to measure and monitor regional oximetry, and guide intraoperative intervention, cognitive decline seven days post-operative was lower. Over half of patients that were not monitored with INVOS™ technology experienced cognitive decline while those with the INVOS™ Regional Oximetry monitoring only experienced cognitive decline 28% of the time.4
In addition to reducing neurological decline, monitoring cerebral oxygenation, and intervening as needed has been shown to reduce the time patients spent in the ICU after CABG surgery.5 The same study found that when patients did not have regional oximetry driven interventions, they had significantly more major organ morbidity defined as a composite endpoint of prolonged ventilation, myocardial infarction, stroke, and return to the operating room for re-exploration.5
A study involving goal-directed hemodynamic therapy with regional oximetry involving 120 patients found when used, 60% fewer patients suffered from kidney injury. Additionally, there was a reduction in how many units of red blood cells needed to be used during surgery. Patients also had fewer strokes in this same study.[6]
Regional Oximetry with CARESCAPETM Monitors
GE Healthcare’s CARESCAPE monitors with 3.2 software are integrated with regional oximetry capabilities using the INVOS™ technology. By using Medtronic’s INVOS™ technology, clinicians are now able to seamlessly monitor regional oximetry along with other vital parameters.
INVOSTM is compatible to be used simultaneously with ENTROPYTM depth of anesthesia monitoring, adding another layer to patient safety.
Cerebral oxygenation can be monitored intraoperatively and captured data can follow the patient into the PACU and ICU to provide a more complete picture of the patient’s status during the whole patient´s journey.
Summary
- CABG surgical patients are at risk for several complications related to surgery, including cerebral desaturation
- Regional oximetry is a noninvasive method to capture real time cerebral tissue oxygenation readings during surgery
- When patients received interventions based on cerebral oximetry changes, patient outcomes are improved including fewer incidences of cognitive decline, stroke, and major organ dysfunction4,5
- GE’s CARESCAPE v3.2 incorporates Medtronic’s INVOS™ system to allow seamless regional oximetry monitoring for clinicians to utilize intraoperatively and post-surgery
References
[1] Reiche, S et al. (2021). Perioperative outcomes of coronary artery bypass graft surgery in Johannesburg, South Africa. Journal of Cardiothoracic Surgery. 16(1). 7.
[2] Subramaniam, B. (2016). A multicenter pilot study assessing regional cerebral oxygen desaturation frequency during cardiopulmonary bypass and responsiveness to an intervention algorithm. Anesthesia and Analgesia. 122(6). 1786-93.
[3] Vretzakis, G. (2014). Cerebral oximetry in cardiac anesthesia. Journal of Thoracic Disease. 6(Suppl 1). S60-S69.
[4] Colak, Z et al. (2015). Influence of intraoperative cerebral oximetry monitoring on neurocognitive function after coronary artery bypass surgery: a randomized prospective study. European Journal of Cardiothoracic Surgery. 47(3). 447-54.
[5] Murkin, J et al. (2007). Monitoring brain oxygen saturation during coronary bypass surgery: a randomized, prospective study. Anesthesia and Analgesia. 104(1). 51-8.
[6] Anastasiadis K, et al. (2017). A multidisciplinary perioperative strategy for attaining “more physiologic” cardiac surgery. Perfusion. 32(6):446–453.
Disclaimer: The INVOS™ Regional Oximetry Technology should not be used as the sole basis for diagnosis or therapy and is intended only as an adjunct in patient assessment.