The causes of cerebral desaturation during cardiac surgery is likely multifactorial, involving many patient-specific comorbidities or clinical scenarios that influence the balance between cerebral oxygen supply and demand. The most common factors leading to cerebral desaturation can be categorized as contributing to one of three processes that lead to imbalances between cerebral oxygen supply and demand:
Without real-time recognition and intervention to eliminate such imbalances, hypoxic/ischemic injury may result.
|LIMITED CEREBRAL BLOOD SUPPLY||Mechanical Obstruction to Cerebral Blood||Causes of mechanical obstructions to cerebral blood flow include circumstance that limit arterial inflow or venous outflow.||Malperfusion|
|Cerebral Hypoperfusion||Cardiac output, autoregulation, partial pressure of carbon dioxide, and mean arterial pressure all play a role in determine cerebral perfusion.||Hypocapnia|
|Reduced cardiac output|
|INADEQUATE OXYGEN CONTENT||Hypoventilation||Failed oxygen delivery may result in injury despite constant hemodynamics.||Systemic hypoxia|
|Anemia||Anemia may result in inadequate oxygen delivery or increase embolic load during cardiac surgery, increasing the potential for ischemic cerebral injury.1||Hemodilution|
|UNMET CEREBRAL METABOLIC DEMAND||Increased cerebral metabolic rate of oxygen||Increased cerebral metabolic rate may contribute to an imbalance between cerebral oxygen supply and demand, potentially resulting in hypoxic/ischemic neurological injury.||Rewarming|
|Lighter depth of anesthesia|
Cerebral oxygenation and perfusion can be monitored continuously and noninvasively during cardiac surgery utilizing the INVOS™ cerebral/somatic oximeter. In the event of cerebral desaturation, several interventions are possible for clinicians to correct a decrease in rSO2 values. These interventions target the optimization of those mechanisms that influence cerebral blood supply, inadequate oxygen content, and unmet cerebral metabolic demand.
1. Karkouti K, Djaiani G, Borger MA, et al. Low hematocrit during cardiopulmonary bypass is associated with increased risk of perioperative stroke in cardiac surgery. The Annals of thoracic surgery. 2005;80(4):1381-1387.