The Impact of Anesthesia on Traumatic Brain
Injuries
Emma Watson, Amber Baranek, Ryoko Kausler, PhD, FNP-BC, MN, RN, and
Lucy Zhao, PhD, MSN, MPaff, RN
Boise State University School of Nursing
Abstract
This literature review examines potential risks of anesthesia in
traumatic brain injury (TBI) patients. Findings from 19 studies suggest
that TBI patients with anesthesia may be at risk for secondary insults
such as hypotension and delayed neurologic recovery. While evidence
suggests adverse outcomes, further research is needed to investigate
variable relationships. This review emphasizes the importance of
initiating additional studies to strengthen evidence and improve care
for TBI patients.
Background
Traumatic brain injuries (TBIs) frequently occur alongside injuries
requiring surgical intervention and anesthesia (Abcejo et al., 2017).
With approximately 214,000 TBI-related hospitalizations in the U.S.
(2020) and 5.3 million annual orthopedic surgeries, there is significant
overlap between these patient populations (Centers for Disease Control
and Prevention, 2024; Vavilala et al., 2017). Research indicates that
57% of TBI patients undergo surgery within a week of injury, yet without
standardized TBI diagnosis protocols, many cases may go unrecognized
before surgery (Abcejo et al., 2017; Romeu-Mejia & Goldman, 2019).
This timing creates concerns about the interaction between TBIs and
anesthetics during early interventions. Secondary insults (SIs) are
deficits caused by reduced cerebral blood flow, leading to brain
dysfunction. SIs include hypotension, hypercarbia, hypocarbia,
hyperglycemia, hypoglycemia, hyperthermia, and hypoxia (Algarra et al.,
2017). These complications warrant particular attention given the
potential dangers of anesthesia use. The rising incidence of TBIs and
their lasting effects make understanding this interaction increasingly
important (Vavilala et al., 2017). While limited research suggests
possible risks for TBI patients receiving general anesthesia, further
investigation is needed to determine whether they experience more
adverse reactions compared to non-TBI patients. The purpose of this
literature review is to identify current literature regarding the
potential risks associated with anesthesia use in TBI patients.
Methods
This literature review included sources from the databases CINAHL,
PubMed, and MEDLINE that were published between 1990 and 2024. The
following search terms were used with limiters and expanders: concussion
AND anesthesia, concussed patient anesthesia care, traumatic brain
injuries, intraoperative, and secondary insult. The quality of sources
was assessed using Melnyk's Rapid Critical Appraisal (RCA) Tool
(Melnyk & Fineout-Overholt, 2019).
Results
A total of 19 articles were selected. Based on the RCA Tool, levels
of evidence for the chosen articles were as follows: 2 level II, 2 level
III, 10 level IV, and 5 level VI. The strength of these articles
included 11 strong, 7 moderate, and 1 weak study (See Table 1).
Secondary Insults
SIs were a common theme in these findings. A retrospective study on
the prevalence of SIs in TBI patients undergoing an orthopedic surgery
within 2 weeks of their injury reported SIs such as systemic
hypotension, intracranial hypertension, and both hypercarbia and
hypocarbia. In this sample, 87% of patients experienced at least one SI
intraoperatively. The most common SI was systemic hypotension (Algarra
et al., 2017). Hypotension was likely a direct result of anesthesia
rather than trauma-induced hypovolemia. Since the surgeries were limited
to isolated orthopedic procedures with minimal average blood loss
(75--100 mL) the likelihood was low that hypovolemia from bleeding was a
significant contributing factor. While confounding variables cannot be
entirely ruled out, the data strongly suggest that anesthesia played a
primary role in the observed secondary insult of hypotension (Algarra et
al., 2017). Another sample noted that systemic hypotension occurred
46.41% of the time in TBI patients undergoing surgery. This study
identified two factors that influenced the occurrence of intraoperative
hypotension: duration of anesthesia and severity of the Glasgow Coma
Scale (GCS) score. When patients in this study were exposed to
anesthesia for longer than 135 minutes, they were four times more likely
to experience hypotension. If these patients had severe GCS scores, they
were seven times more likely to have intraoperative hypotension (Zewdu
et al., 2024).
Physiological Changes
In the setting of a TBI, multiple biomarkers have been identified
that can indicate brain damage. Biomarkers Tau and S100B have both shown
promise as clinical indicators of TBIs (Wang et al., 2021; Oris et al.,
2023).
The results showed that there may be some risks associated with
anesthesia for TBI patients. Propofol was found to limit the neurologic
recovery process in rats that were given a TBI. In this particular
study, it was also noted to increase the mortality rate and the overall
neurologic dysfunction in these animals (Thal et al., 2014).
Finally, beta A4 amyloid protein deposits were found to play a role
in the relationship between anesthesia and TBIs. Beta amyloid protein
deposits can develop in the brain following a concussion, as evidenced
by a study during which 38% of necropsies on deceased TBI patients under
the age of 65 found beta amyloid deposits. The prevalence of these
deposits in people under 65 years old is less than 0.01% (Roberts et
al., 1991). In a randomized controlled trial involving rats, multiple
mild head traumas resulted in the development of beta amyloid protein
deposits within the brain (Grant et al., 2018). Anesthesia may
exacerbate the growth of these accumulations. A randomized controlled
trial resulted in inhaled anesthetics increasing the oligomerization of
these protein deposits (Eckenhoff et al., 2004).
Discussion
This literature review examined risks of anesthesia use in TBI
patients, revealing two major concerns: SIs and physiological changes.
SIs can exacerbate brain damage by reducing oxygen access, manifesting
as deteriorated CT scan results and decreased GCS scores (Algarra et
al., 2017). Systemic hypotension is particularly dangerous, with severe
TBI patients and those under prolonged anesthesia at highest risk (Zewdu
et al., 2024). Quick correction of these insults is crucial to prevent
further damage.
Physiological changes include alterations in blood and saliva
biomarkers, which could help identify at-risk patients (Di Battista et
al., 2018; Di Pietro et al., 2021). Beta amyloid protein deposits,
associated with Alzheimer's disease, have been found following severe
TBIs (Roberts et al., 1991) or multiple moderate head traumas (Grant et
al., 2018). These deposits can cause inflammation, oxidative stress,
decreased glucose metabolism, and synaptic dysfunction (Grant et al.,
2018). Common anesthetics like isoflurane, halothane, and high
concentrations of propofol can increase beta amyloid oligomerization,
potentially worsening concussion symptoms and impeding healing
(Eckenhoff et al., 2004). Animal studies have shown that propofol
specifically can increase mortality rates and exacerbate TBI symptoms
while disrupting brain healing processes. Propofol inhibited
neurogenesis in particular, and this was described to be an important
factor in memory function, healing, and cognitive function in both
humans and rats. While this study was performed on rats rather than
human subjects, this study emphasized that despite differences between
species, the results seen may have "a high relevance and impact on the
clinical application of propofol" (Thal et al., 2014). Confirmation of
these findings is needed before any alternative practices can be
recommended, however.
Nursing implications
In many cases involving severe trauma, surgical intervention cannot
be avoided or delayed when there is a TBI present. In these cases,
understanding the risk of anesthetic use is needed to address
complications that may arise as a result of intervention, such as
secondary insults, rather than preventing the use of anesthesia
entirely. In situations where an elective or less urgent surgery is
being performed, understanding the relationship between anesthetic use
and TBI patient outcomes can give patients an opportunity to be better
informed when giving consent to surgical intervention.
Clinical decision support systems have proven valuable in reducing
complications in TBI patients undergoing anesthesia. On-screen alerts
and real-time notifications help anesthesiologists respond quickly to
abnormal data, improving guideline adherence and allowing swift
correction of secondary insults with high accuracy (Colletti et al.,
2019). While implementation varies based on patient needs, nurses can
advocate for appropriate supervision levels, especially if there is an
understanding about the risk for patient complications (Vavilala et al.,
2017).
While MRI and CT scans are common diagnostic tools, they have
limitations. MRIs often show "mostly normal findings" despite TBI
presence, necessitating comprehensive physical and cognitive assessments
(Cohrs et al., 2018). Furthermore, their implementation varies despite
existing guidelines for their use (Lagares et al., 2022). As patient
advocates and educators, nurses must ensure thorough evaluations beyond
imaging alone.
Nurses can play a crucial role in TBI risk assessment through
screening questions about recent head trauma and implementing tools like
the Post-Concussion Symptom Scale. This quantitative scale measures
physical, cognitive, vestibular, ocular, sleep, and emotional symptoms
on a 0-6 severity scale (Sik et al., 2022). Additionally, neurocognitive
testing via iPad applications can be integrated into nursing assessments
(Lunter et al., 2018). If further research is conducted and confirms
that anesthetic use in the setting of a TBI diagnosis is linked with
complications, these assessments can allow nurses to determine if there
is a risk for adverse outcomes. From there, it is important for nurses
to educate patients regarding the risk of anesthesia use, and advocate
for further monitoring and intervention that a patient may need if there
are complications.
Limitations
Research in this area faces ethical constraints due to patient safety
concerns, limiting the ability to conduct randomized control trials.
This prevents direct human subject research that could cause harm,
adhering to the principle of nonmaleficence. This is why several studies
and randomized controlled trials that were included were performed on
animals rather than human subjects. The possible variance in data
between species must be acknowledged when examining the results within
this review. Due to these same ethical limitations, articles have been
included in this review that have ambiguous or unclear inclusion
criteria regarding what qualifies as a TBI. This potential variation may
also impact the validity of the results described and should be
considered in future research. The varying presentation of symptoms
between individuals and a lack of universal diagnostic criteria for a
TBI may contribute to the indistinct meaning ascribed to the term.
This analysis was conducted as part of an undergraduate
Evidence-Based Practice course project to increase nursing students'
competencies in analyzing research and does not include systematic
reviews or meta-analyses. In addition, articles that met literature
review criteria were recorded for inclusion rather than systematically
tracking excluded articles. This limitation provides an opportunity for
improvement in future scoping reviews. The date range in this study is
broad because the research in this area is currently limited,
necessitating an exploration of older articles. Research methods may
have changed with time, influencing these results. In addition, changes
in practice across this timespan may influence the interpretation of the
results within this review.
Conclusion
Current evidence may indicate an increased risk of adverse outcomes
in TBI patients undergoing anesthesia compared to those without a TBI;
however, further research is required to fully understand the scope of
anesthesia's effects in this population and confirm the data found in
the literature of this review. More research could provide an
opportunity to confirm or reject a causative relationship in this
matter, but it is difficult to produce due to ethical concerns. It is
important for nurses to recognize the risks associated with the use of
anesthesia in patients with TBIs, as emerging evidence may lead to new
protocols in clinical practice.
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