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MORPHOLOGICAL CHANGES IN CARDIAC TISSUE AFTER
MECHANICAL TRAUMA UNDER GENERAL ANESTHESIA: AN
EXPERIMENTAL ANALYSIS
Turniyozov Azamat Askarovich
Independent researcher, Bukhara State Medical Institute
https://doi.org/10.5281/zenodo.16024196
Abstract
This experimental study investigated morphological changes in rat heart
tissue subjected to mechanical trauma under general anesthesia (nitrous oxide –
N₂O). According to histological analysis, dystrophic changes in cardiomyocytes,
karyolysis, cytolysis, focal necrosis, interstitial edema, venous congestion, and
leukocytic infiltration were identified. These structural changes may impair
cardiac function and are essential indicators for evaluating the effects of
anesthesia. The study results are significant for early detection and prevention
of cardiac complications in clinical practice.
Keywords:
heart, morphological change, general anesthesia, N₂O,
mechanical trauma, experiment.
Materials and Methods
The research was carried out at the Scientific Research Laboratory of the
Bukhara State Medical Institute in accordance with institutional guidelines and
ethical standards for the use of laboratory animals. The experimental model was
based on the use of 30 clinically healthy, 9-month-old male and female albino
rats, each weighing between 200 to 250 grams. These animals were bred and
maintained under controlled conditions with a 12-hour light/dark cycle,
standard pellet diet, and ad libitum access to water.
Prior to experimentation, all animals were acclimatized to laboratory
conditions for 7 days. The rats were randomly allocated into two groups using a
computerized randomization algorithm to ensure unbiased distribution and
reduce potential selection bias:
Control Group (n = 10):
Animals in this group did not receive any
mechanical trauma or anesthetic exposure. They were used to represent the
normal, unaltered physiological state of cardiac tissue for baseline comparison.
Experimental Group (n = 20):
Animals were subjected to a controlled
mechanical trauma, specifically a blunt impact directed to the soft muscle tissue
of the right hind limb using a standardized calibrated device. Within 15 minutes
of injury induction, these rats were exposed to general anesthesia via inhalation
of nitrous oxide (N₂O) at a clinical concentration for a duration of 120 minutes in
a sealed chamber with regulated airflow.
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All procedures were approved by the Institutional Animal Ethics Committee
and followed international standards for animal care (ARRIVE guidelines). At
the end of the anesthesia period, animals were humanely euthanized via cervical
decapitation to preserve tissue integrity for downstream histological
assessment.
Immediately following euthanasia, the hearts were excised, rinsed in cold
saline, and fixed in 10% buffered formalin for 24 hours. Subsequently, standard
paraffin embedding protocols were followed. Thin sections (4–5 µm) of cardiac
tissue were obtained using a rotary microtome. The sections were stained with
hematoxylin-eosin (H&E) to evaluate general histoarchitecture, Van Gieson stain
to highlight connective tissue and collagen fibers, and toluidine blue for
identifying acidic tissue components and metachromatic structures.
Microscopic evaluations were performed under a Leica DM-LB light
microscope equipped with digital imaging. High-resolution images were
captured for documentation and comparative analysis.
Morphometric analysis was conducted using the DN-107T / Model NLSD-
307B ocular micrometer (Nobel, China). Diameters of cardiomyocytes were
measured across four cardiac regions: right atrium, left atrium, right ventricle,
and left ventricle. For each animal, at least 20–25 cardiomyocytes were
measured per anatomical location to ensure statistical relevance and accuracy.
Data obtained from morphometric measurements were subjected to
statistical analysis using GraphPad Prism 9 and Microsoft Excel 2019.
Descriptive statistics were computed, including mean values and standard
deviations. Student’s t-test was applied to determine the statistical significance
between control and experimental groups, with a p-value < 0.05 considered
statistically significant.
Results
In the control group, the cardiac tissues of rats exhibited normal anatomical
and histological architecture. The myocardium was characterized by uniformly
aligned cardiomyocytes with clearly distinguishable central nuclei, intact
sarcoplasm, and well-organized intercalated discs. No histopathological signs of
edema, inflammatory infiltration, hemorrhage, fibrosis, or vascular
abnormalities were observed. The diameters of arterioles and venules were
within physiological norms, and connective tissue fibers surrounding the
myocardium were sparse and evenly distributed. Collagen fiber presence was
minimal and restricted to the perivascular regions.
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In contrast, significant pathological changes were documented in the
experimental group, which underwent mechanical trauma followed by general
anesthesia. Histological sections revealed notable hypertrophy of
cardiomyocytes, evident from their increased transverse diameter, alongside
cytoplasmic vacuolization
,
nuclear pyknosis
,
karyolysis, and cytolysis. These
findings are indicative of cellular injury and early stages of myocardial
degeneration.
The interstitial compartment showed moderate to severe edema, often
separating adjacent muscle fibers. Van Gieson staining revealed a notable
increase in collagen deposition, particularly in the perivascular and intercellular
zones, suggestive of reactive fibrosis
.
Toluidine blue staining highlighted the
presence of granulocyte-dominant infiltration, with diffuse and focal
accumulations of neutrophils and eosinophils, indicating an acute inflammatory
response.
Additionally, venous congestion was prominent in small and medium-
caliber vessels, with erythrocyte stasis and vascular dilation
.
Hemosiderin-laden
macrophages were occasionally observed, pointing to minor extravasation and
degradation of erythrocytes. Thickening of arterial walls, with hyaline-like
changes and partial luminal narrowing, suggested early-stage arteriosclerosis,
possibly as a consequence of oxidative or mechanical stress induced by trauma
and anesthesia.
Morphometric Analysis
Quantitative morphometric analysis confirmed statistically significant
increases in cardiomyocyte transverse diameters in the experimental group
compared to controls. Specifically:
Right atrium: increased by 6.89%
Left atrium: increased by 3.4%
Right ventricle: increased by 10.25%
Left ventricle: increased by 3.63%
These differences were consistent across the sampled regions and were
statistically significant (
p
< 0.05). The findings indicate regional susceptibility of
cardiac structures, with the right ventricle being more vulnerable to the
combined effects of mechanical trauma and anesthetic-induced stress.
Anatomical Observation
In both groups, the gross anatomical configuration of the heart
corresponded to standard rodent cardiac anatomy. The heart was
asymmetrically positioned within the thoracic cavity, occupying a
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predominantly left-sided orientation relative to the midline. Its apex directed
caudally and ventrally, with the base anchored near the third to fifth costal
cartilages. The anterior surface of the heart was mostly covered by the lungs,
leaving a narrow cardiac notch visible through the thoracic wall.
No major anatomical displacements were noted in the control group, while
slight lateral deviation of the apex toward the left side and mild epicardial
thickening were noted in several rats from the experimental group, likely due to
subclinical edema or connective tissue expansion.
Conclusion
The combination of general anesthesia and mechanical trauma leads to
significant morphological and histostructural alterations in cardiac tissue.
Observed cardiomyocyte dystrophy, necrotic foci, and hemodynamic disorders
are factors that diminish cardiac functional capacity. This study highlights the
importance of cardiac monitoring in trauma patients under general anesthesia,
enabling early identification of risk markers and development of preventive
strategies. The findings are of practical importance in cardiology,
anesthesiology, and experimental morphology.
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