Overview

Cerebral desaturation results from an imbalance between cerebral oxygen supply and demand resulting from either limited cerebral blood supply, inadequate oxygen content, or unmet cerebral metabolic demand.

The etiology 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: limited cerebral blood supply, inadequate oxygen content, and unmet cerebral metabolic demand. Without real-time recognition and intervention to eliminate such imbalances, hypoxic/ischemic injury may result.
 

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.

Table 1. Causes of intraoperative cerebral desaturation during cardiac surgery and related interventions
  Condition Definition Common Causes
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
Cannula misplacement
Venous hypertension
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
Impaired autoregulation
Hypotension
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.([FOOTNOTE=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.],[ANCHOR=View Abstract],[LINK=/content/mitg/websites/languagemasters/na/en-us/support/clinical-evidence.html?id=297477]) 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.
Lighter depth of anesthesia