Advances in the application of ultrasound imaging technology in clinical anesthesia

Authors: Zhong Mingqiang, Wang Jinying, Department of Anesthesiology, Zhucheng People's Hospital, Weifang Medical College; Ji Fan Layer, Department of Anesthesiology, Weifang People's Hospital, Shandong Province

Ultrasound medicine is a set of medicine, acoustics, computer science in one of the disciplines, because of its non-invasive, convenient, efficient and other advantages, has been widely used in the diagnosis and treatment
of multiple organs.
In recent years, ultrasound technology has received widespread attention and application
in the perioperative period.
Anesthesiologists use ultrasonography for preoperative evaluation, intraoperative testing, and invasive procedures to guide themselves in developing better anesthesia programs and reducing the occurrence of complications and adverse events, so as to achieve the purpose of
implementing precision anesthesia and comfortable medical treatment.

1.
Ultrasound-guided nerve block technique

Traditional nerve blocks require the use of anatomical markers on the surface of the body and the search for anomalies to probe for localization
.
Because of the presence of structural variations in the human body, even if the operator has solid anatomical knowledge and rich clinical experience, it may still lead to the failure of the operation, and even the injection of local anesthesia into blood vessels or damage nerves causing serious complications
.
Ultrasonography can determine the adjacent location and interrelationship of nerves, blood vessels and muscles around the puncture site, provide real-time images when blocking the target nerve, make nerve localization more intuitive and accurate, and greatly improve the success rate
of puncture.
In addition, ultrasonography can monitor the spread of local anesthetics in real time, avoiding nerve damage
.

At present, the application scope of ultrasound-guided nerve block mainly includes different approaches to brachial plexus block, femoral nerve block, sciatic nerve block, hidden nerve block, popliteal nerve block, obliteral nerve block, etc
.
Brachial plexus block is the most commonly used nerve block in upper extremity surgery, and studies have shown that ultrasound-guided brachial plexus block operation has a high success rate and perfect blocking effect, which can be safely used for upper extremity surgery
.

Lower extremity surgery often uses spinal anesthesia, but intraspinal anesthesia is extremely detrimental
to the elderly because it blocks the sympathetic nerves and can lead to hemodynamic changes.
Studies have shown that ultrasound-guided sciatic nerve combined with occult nerve block for knee-to-knee surgery can provide perfect anesthesia and a long postoperative analgesia with little
effect on respiratory circulation.

2.
Application of ultrasonography in the positioning and guidance of intraspinal anesthesia

Spinal canal anesthesia is a commonly used anesthesia method in clinical practice, because of its rapid onset of action and accurate effect, it is often used in lower limb and abdominal pelvic surgery
.
Accurately locating the puncture point is the first step
in performing intraspinal anesthesia.
The traditional method of positioning is palpation and localization of the body surface, but due to the variation of individual anatomy, it often leads to difficulty in manipulation, failure of puncture, and even serious complications
.
Ultrasonography can visualize the anatomy of the spinal canal and its surrounding tissues, measure the distance from skin to spinal canal, and improve the success rate
of puncture.
Clinical use of spinal anesthesia in obese, elderly, scoliosis, patients with a history of previous spinal surgery has unique advantages
.
Intraspinal anesthesia
is most commonly used for caesarean section.

Due to maternal abdominal distension and excessive obesity, the anatomical signs on the surface of the body are often unclear-touched
.
Ultrasonography can precisely locate the midline of the spine and the spinous space, reducing the number of punctures
.
In elderly patients, due to degenerative changes in the spine, ligament calcification, anatomical markers are difficult to palpate
.
Some scholars have found that for elderly patients with difficulty touching anatomical markers, preoperative ultrasonography helps to identify the spinous space, which can significantly improve the accuracy
of spinal puncture positioning.

Compared with pre-puncture ultrasonography positioning, ultrasound-guided puncture can display the direction of needle entry and needle depth in real time, visualizing
intraspinal anesthesia.
Chong et al.
conducted a randomized controlled trial that showed a high success rate of real-time ultrasound-guided single punctures, a reduction in the total number of punctures, and improved the safety of
intraspinal anesthesia.

3.
Ultrasound-guided vascular puncture technique

In clinical anesthesia and intensive care, vascular puncture is an important means of
monitoring and treatment.
This consists mainly of arterial puncture and central venous puncture
.
The traditional operation relies on the positioning of anatomical signs, which is easy to cause mispenetration and injury, resulting in complications
such as hematoma and pneumothorax.
Especially in infants, obesity and vascular variants, puncture is difficult
.
Ultrasonography can clearly show the blood vessels requiring puncture and their adjacent structures, distinguishing between arteries and veins
.

Real-time ultrasound-guided arteriovenous puncture catheterization improves the success rate of puncture and reduces the occurrence
of complications such as bleeding and damage to surrounding tissue.
Ultrasound-guided internal jugular venous puncture catheterization has been widely used for perioperative central venous pressure monitoring and to establish an effective route
of infusion administration.
It has been found that ultrasound-guided placement of a central venous catheter significantly improves the success rate of puncture catheterization, reduces the number of punctures, and reduces the incidence
of puncture complications.
Vascular puncture is very difficult
in infants and young children due to their special physiological characteristics.

Altun et al.
have found that ultrasound-guided central venous puncture catheterization is safe for low-weight infants and young children with a high
rate of success.
In clinical anesthesia, arterial puncture catheterization is mainly used for dynamic monitoring of perioperative blood pressure and examination
of changes in the internal environment.
Cao Lan et al.
performed radial artery puncture catheterization for 120 critically ill patients who needed arterial invasive blood pressure monitoring, and through control, ultrasound-guided radial artery puncture could dynamically observe radial artery blood vessels, facilitate the positioning of puncture points and guide puncture, improve the success rate of initial catheterization, and reduce the incidence of
complications.

4.
Application of ultrasonography in perioperative gastric volume assessment

Reflux aspiration of gastric contents is a common and serious anesthesia-related complication that is significantly associated
with perioperative morbidity and mortality.
Dietary abstinence before surgery is an important measure
to prevent perioperative reflux aspiration.
The risk of traditional perioperative aspiration is assessed primarily based on whether the patient is in a full stomach state and the length
of time the patient has been fasting before surgery.
However, due to individual differences, different physiological states and diseases may lead to delayed gastric emptying, although the fasting time exceeds 8 hours, there are still a considerable proportion of surgical patients who cannot achieve the purpose of
gastric emptying.
Even in the emergency department surgery, it is impossible to guarantee the time of fasting, which greatly increases the risk of
aspiration.

Gastric ultrasonography not only assesses the nature of gastric contents, but also estimates the volume of gastric contents by measuring the
cross-sectional area of the antral region.
It is difficult for children to abstain from drinking and fasting, especially infants and young children, and even if the diet is strictly forbidden before surgery, the possibility of reflux aspiration is still higher
than that of adults.
Therefore, the assessment of gastric volume in children is particularly important
.
The results of the study showed that the gastric content volume of preschool children was positively correlated with body weight, age, and height, and that the volume of gastric contents and gastric contents per kilogram of body weight were positively correlated with the cross-sectional area of the antrals under the right decubitus, so the measurement of the cross-sectional area of the antral antrals by right subsupine ultrasonography can be used to assess the volume
of gastric contents before surgery in preschool children.

After pregnancy, the lower esophageal sphincter is relaxed, and the enlarged uterus causes the stomach to move up, greatly increasing the risk of
reflux aspiration.
Amanal et al.
conducted gastric ultrasonography on 85 full-term pregnant women, and the results showed that by measuring the cross-sectional area of the antrum to estimate the gastric volume, it was possible to identify patients with pulmonary aspiration, and gastric ultrasonography was simple and effective
in measuring the antral cross-sectional area of pregnant women.

5.
Application of ultrasonography in perioperative blood volume assessment

Volumetric monitoring is an important item
of perioperative monitoring.
Dietary abstinence before surgery and loss of intraoperative fluids can lead to effective circulating volume depletion in patients and cause hemodynamic changes
.
Timely and correct assessment of the patient's blood volume contributes to the improvement
of circulatory function.
Traditional assessment indicators such as blood pressure, pulse rate, pulse pressure, urine output, etc.
, are less
sensitive.
Although the accuracy of central venous pressure, stroke index, and cardiac output monitoring is high, it is invasive and costly, and its clinical use is limited
.
The inferior vena cava is a volumetric blood vessel, and ultrasonography to measure the inner diameter of the inferior vena cava can accurately assess the patient's volume status and can be used as a noninvasive and reliable method
of assessing blood volume.

Older patients are poorly tolerated to volume depletion and are more likely to experience hemodynamic fluctuations, so ultrasonography measures the inner diameter of the inferior vena cava to assess the volume status of elderly patients in clinical anesthesia and intensive care units
.
Wang et al.
successfully used ultrasonography in the intensive care unit to measure the inner diameter of the inferior vena cava in 18 patients who were sedated after mechanical ventilation pulmonectomy to predict the fluid reactivity of patients with mechanical ventilation total pulmonectomy
.

Other studies have shown that ultrasonography measures the rate of variability of peak carotid artery velocity to predict volume reactivity
.
Especially when surgery requires special positions, such as prone positions, the internal pressure of the chest and abdomen increases, and volume depletion
is likely to occur.
Ultrasonography measures the rate of variability of peak carotid flow rate to make an accurate prediction
of patient volume responsiveness.

6.
Application of transesophageal cardiac ultrasound in perioperative period

Transesophageal cardiac ultrasound (TEE) is the placement of an ultrasound probe into the esophagus directly adjacent to the large blood vessel of the heart to perform a close probe
of the structure of the heart.
The perioperative period is mainly used to evaluate the clinical cause or cause of respiratory and circulatory dysfunction, including valvular changes, aortic lesions, intracardiac mass, thrombosis, confirmed diagnosis of localized pericardial tamponadis, unexplained hypoxia, hypotension, etc
.

Due to the absence of sternum and lung occlusion, TEE can develop all-round and detailed imaging of the cardiovascular, with the advantages
of high image quality, good stability, and real-time continuous monitoring.
In patients with postoperative and severe chest trauma, pericardial tamponade often caused by local hematomas or wrapping effusions, leading to severe hemodynamic disorders and increased case fatality, immediate cardiac ultrasonography is a key measure for
management.
TEE can accurately and quickly detect focal hematoma to guide further treatment
.

Some scholars have found that TEE is helpful in determining the cause of shock in trauma patients and further guiding circulatory management
.
Transesophageal real-time 3D echocardiography is a combination of esophageal ultrasonography and real-time 3D echocardiography technology, real-time acquisition and rapid imaging, which is used to diagnose lesions
in heart valves.
This technology can display the three-dimensional structure and functional state of the heart in the circulatory state in a multi-faceted and intuitive manner, which is not only a unique diagnostic tool, but also can be used to guide and monitor cardiac surgery and catheter interventional treatment, which has important clinical value
.

7.
Application of ultrasonic examination technology in airway management

Ultrasonography can visualize the anatomical structures associated with the upper respiratory tract and is increasingly used
in airway management.
The perioperative period is often used for difficult airway prediction, airway anatomical positioning, tracheal catheter positioning, etc
.
Identification of difficult airways is a crucial part of anesthesia practice, and preoperative airway assessment is a necessary step
for anesthesiologists to predict difficult intubation.
Commonly used assessment methods include Mallampati grading, mouth opening, nail and jaw distance, temporomandibular joint mobility, C-L classification, etc.
, but the sensitivity and specificity of a single assessment index to predict difficult airways are not high
.

While ultrasonography can observe and measure the structure and distance of airway-related tissues, Parameswari et al.
studied 130 patients with selective general anesthesia surgery, and observed that ultrasonography measured the level of the thyrohyoid periosteum skin to epiglottis < 18mm distance to predict intubation difficulties<b10>.
Of course, ultrasonography to locate the hyoid bone to measure the distance between the tongue and chin can also predict difficult airways
.
Endotracheal intubation is a common method of airway management, and it is important
to determine the location of the endotracheal tube quickly and accurately.

Ultrasonography can directly display airway anatomical images and confirm the location of the endotracheal catheter in
real time.
Some scholars used ultrasound to observe the "pulmonary sliding sign" and diaphragm movement in children, and compared auscultation and observation of the "pulmonary sliding sign" to judge the position of the tracheal catheter, and the results showed that the observation of the "pulmonary sliding sign" by ultrasonography was more accurate than auscultation to determine the optimal position
of the tracheal catheter.

8.
Application of lung ultrasonography in the perioperative period

Lung ultrasonography (LUS) has good diagnostic sensitivity and specificity, and the perioperative period is mainly used in the diagnosis and differentiation
of various chest diseases such as pneumothorax, atelectasis, pulmonary edema, ventilator-associated pneumonia, pulmonary congestion and fibrosis, and pulmonary embolism.
Compared with traditional X-ray photography and CT examination, LUS has the advantages
of fast and convenient, real-time non-invasive, and low price.
Pneumothorax is one of the most common causes of acute dyspnea, and LUS is primarily judged
by signs such as "pulmonary sliding signs," B-line, A-line, pulmonary point, and pulmonary pulse.

Zhang et al.
have found that LUS is highly sensitive and specific for pneumothorax diagnosis and avoids ionizing radiation compared to CT scans with the gold standard for pneumothorax diagnosis, especially in newborns
.
In patients with mechanical ventilation, lung tissue is at risk of alveolar collapse and is prone to atelectasis, leading to hypoxemia
.
Monastesse et al.
, conducted a study involving 30 patients with laparoscopic surgery and found that changes in LUS scores were associated with changes in oxygenation, and determined that the application of LUS could detect perioperative atelectasis
in time.

In summary, ultrasound imaging technology has been more and more used
in clinical anesthesia work because of its advantages of real-time, convenient and non-invasive.
The application of ultrasonography has greatly improved the safety and comfort of anesthesia
.
Due to the highly specialized nature of ultrasound technology, its application in clinical anesthesia work is still subject to many limitations
.
This puts forward higher requirements for anesthesiologists, requiring anesthesiologists to continuously learn and strive to expand their
knowledge.
Clinical anesthesia has entered the era of visualization, with the continuous development and improvement of ultrasound medicine and ultrasound equipment, as well as the unremitting efforts of anesthesiologists, the application of ultrasound imaging technology in clinical anesthesia will surely step to a new level
.

Source: Huang Ziling,Zhao Ning.
Research Progress on Independent Component Analysis of Poststroke Functional Networks[J].
Journal of Medical Imaging,2022,32(03):519-522.