Concussion in the Perioperative Period: A Common Condition Requiring More Investigation
The CDC estimates that 2.5 million traumatic brain injuries (TBI) in the United States alone require either a hospital visit or result in death, annually. Seventy-five to 95% of these are considered to be mild TBI’s (mTBI), most often secondary to motor vehicle accidents, sports-related injuries or falls. Concussion has been defined as a brain injury induced by biomechanical forces, that may or may not include loss of consciousness, and typically results in a rapid onset of short-lived impairment of neurological function with no abnormalities visible on standard structural neuroimaging studies – in essence, a mTBI with functional manifestations. These functional manifestations can be quite diverse, ranging from cognitive and affective impairments to disordered gait and level of consciousness. The most common symptoms are headache, dizziness and difficulty concentrating. For the majority of patients, symptoms resolve within seven to ten days of the injury. The high incidence of concussions and their potential impact on cerebral physiology has recently lead anesthesiologists to question which unique perioperative considerations, if any, apply to this patient population. Martin Smith, MBBS, FRCA, FFICM, Monica S. Vavilala, MD, Jeffrey J. Pasternak, MD, and Deepak Sharma, MBBS, MD, DM, introduced attendees to this bourgeoning field of inquiry.
Patients with concussive symptoms presenting for surgery, either related or unrelated to the concussion-causing injury, are quite common, with estimates ranging from 6 – 7%. Furthermore, approximately 8-12% of patients who have suffered a concussion will present for surgery within one year of their injury, most often in the first month. However, screening tests such as the concussion symptom checklist or sports concussion assessment tool (SCAT 5) are rarely implemented pre-operatively, suggesting that these figures underestimate the true prevalence of this condition. In fact, a recent survey conducted by the Society for Pediatric Anesthesia revealed that most anesthesiologists do not use any screening measures for concussion but would if they had access to one, with the appropriate training. Although it remains unclear whether perioperative concussions alter patient outcomes, most surveyed anesthesiologists stated that they would delay elective surgery until concussive symptoms resolved.
While we are still waiting for formal practice advisories and guidelines, Dr. Vavilala recommended against using any preoperative markers or imaging studies in patients with suspected concussion; instead favoring screening at-risk patients with a validated tool such as SCAT 5. Urgent and emergent cases should proceed to surgery without delay, with special attention paid to minimizing the risk of secondary brain injury by maintaining physiological homeostasis (especially blood pressure and carbon dioxide concentration). For elective surgery, you may consider delaying cases until resolution of concussive symptoms.
Although the pathophysiological mechanisms underlying concussion and their contribution to perioperative care are still under investigation, insights from the TBI literature can help anesthesiologists guide care using a physiologically-principled approach. It is well established that mTBI can impair cerebral autoregulation, CO2 reactivity and cerebral blood flow, rendering the brain susceptible to secondary insults. Furthermore, these physiological changes appear to persist beyond the resolution of concussive symptoms. Although these effects may not manifest in all concussed patients, anesthesiologists should pay special attention to optimizing cerebral perfusion pressure and partial pressures of carbon dioxide in patients with suspected mTBI to mitigate the risks of cerebral hypoperfusion. Concussion has also been shown to disrupt microtubules and alter measures of anatomical and functional connectivity, which may affect patients’ sensitivity to general anesthetics, although this has not yet been systematically studied.
In summary, future studies are needed to extend the concept of readiness for return to play and learn, to readiness for surgery and anesthesia. Until such data is available, anesthesiologists should consider the perioperative period as a potential time for secondary brain injury in patients who have recently suffered a concussion. Although we do not have any data on how anesthetic plans may influence outcomes in this patient population, maintaining adequate cerebral perfusion pressures and normal-range CO2 partial pressures may help mitigate risks of secondary brain injury.
*Coverage from Panel session, Impact of Anesthesia in Patients with Concussion