An estimated 1.7 million people suffer from traumatic brain injuries (TBI) annually in the United States. In cases of blunt trauma, TBI emergencies often coincide with trauma in many organ systems, resulting in hemorrhagic shock. This type of shock causes severe blood loss that limits oxygen delivery to the body’s cells. This can make it difficult for clinicians to diagnose TBI as some early signs of TBI, such as irregular breathing and motor impairment, are also present in hemorrhagic shock.
Researchers recently developed a noninvasive diagnostic tool that can help diagnose TBI in the early stages of emergency care. This diagnostic tool uses heart rate variability, or modulation in the heart’s rhythm, as a measure of TBI. The heart rate is controlled by the autonomic nervous system, which controls involuntary processes such as breathing. Heart rate variability has been correlated with disruptions in the autonomic nervous system and increased intracranial pressure, a common complication of TBI.
The researchers studied the connection between heart rate variability and TBI during hemorrhagic shock. They used an animal model to monitor the heart rate of subjects with a hemorrhage alone and those with a TBI in addition to hemorrhagic injuries. The data obtained from the experiment was used to generate a predictive model for TBI in the early emergency setting.The results of the experiment showed that:
- The time interval between heartbeats was significantly different between the hemorrhage alone and hemorrhage with TBI groups.
- Changes in heart rate variability were seen as early as 15 minutes after TBI.
- A model using five heart rate factors was 91.8 percent accurate at distinguishing a solely hemorrhagic injury from a hemorrhage with a TBI.
These findings suggest that there is potential for improving the early diagnosis of TBI in the presence of hemorrhagic shock. Heart rate variability presents a noninvasive tool for the early detection of TBI following blunt trauma injuries, allowing for earlier treatment and better patient outcomes. Future research should investigate the predictive value of heart rate variability in TBI, as well as the implementation of this measure in clinical practice.
Zhu M, Blears E, Cummins C, et al. Heart rate variability can detect blunt traumatic brain injury within the first hour. Cureus. (July 2022).