• Children should be evaluated when healthy: hypoxia, hypercarbia, fever, sickle chest syndrome, pneumonia, hypoglycemia and other processes can result in increased cerebral blood flow velocities
• Hypocarbia and recent blood transfusions can decrease cerebral blood flow velocities. It is crucial to document if/when a transfusion has occurred
• Children must remain awake and alert during the TCD examination: sleeping results in increased CO2 and can cause increased velocities and misdiagnosis; crying may also result in hyperventilation, which can impact velocities
• Restless or agitated children may be unable to maintain appropriate positioning for a complete exam. Note any variations in exam performance in technical report.