Anesthesia guidelines and expert consensus on learning the expert consensus on perioperative central venous monitoring

Expert consensus on perioperative central venous monitoring Wang Haiying (co-author) Wang Xiangrui Wang Yuan (co-author) Feng Yi Liu Kexuan Yan Min Xia Zhongyuan Gu Erwei Yu Tian (responsible person) I.
Overview of central venous pressure (CVP) It refers to the pressure at the site where the superior or inferior vena cava is about to enter the right atrium.
The normal value of CVP in awake spontaneously breathing patients is 1 to 7 mmHg
.

It mainly reflects the preload of the right ventricle and the discharge capacity of the blood returning to the heart
.

The level of CVP value is related to venous return blood volume, pulmonary vascular resistance and right heart function, but it does not reflect left heart function
.

2.
Assessment before monitoring Central venous pressure monitoring is an important monitoring technique for observing patients' vital signs during the perioperative period
.

The main indications and contraindications are as follows: (1) Indications 1.
Preoperative severe trauma, dehydration, shock, large blood loss, acute circulatory failure,
etc.

2.
Major surgery, complicated or long surgery, and expected loss of body fluids or blood during surgery
.

3.
The surgery itself can cause significant changes in hemodynamics
.

4.
Intraoperative blood dilution or controlled blood pressure should be performed
.

5.
In cases where urine output is difficult to assess (eg, patients with renal failure), a central venous catheter should be placed for volume assessment
.

6.
It is difficult to establish peripheral venous access or the patient needs to replenish blood volume quickly, and peripheral venous access cannot meet the need for fluid replacement
.

7.
Long-term fluid infusion or intravenous antibiotic therapy and total parenteral nutrition are required after surgery
.

8.
A temporary pacemaker needs to be implanted through a central venous catheter
.

9.
Patients requiring temporary hemodialysis
.

10.
Others If the incidence of air embolism is expected to be high during the operation or the need for air embolism suction,
etc.

(2) Contraindications 1.
There is infection at the puncture site
.

2.
Patients with coagulation disorders are relatively contraindicated
.

In addition, it should be noted that for patients with superior vena cava syndrome and a recent pacemaker installation, pressure cannot be measured by catheterization of the upper extremity vein or internal jugular vein, but the femoral vein should be selected
.

 3.
Preparation before monitoring According to the practice guidelines for central venous puncture and cannulation published by the American Society of Anesthesiologists (ASA) in the journal Anesthesiology published in March 2012, the preparation before central venous puncture and cannulation mainly includes the following: Aspects: 1.
Sign the informed consent; 2.
The central venous catheter must be placed in a sterile environment; 3.
Prepare a standardized pressure monitoring device, mainly including a central venous catheter puncture bag, sterile gloves, disinfectant, syringe, Puncture needles, guiding wires, deep vein catheters, skin dilators, sterile saline, suture needles, sutures, pressure bags, disposable transducers, monitoring equipment, etc.
; Central vein puncture routes include: internal jugular vein, clavicle Inferior vein, external jugular vein, femoral vein, etc.
, among which the internal jugular vein and subclavian vein are the most commonly used
.

In clinical practice, the most appropriate method should be selected according to the patient's condition and the operator's clinical experience
.

The angle of the right internal jugular vein is relatively straight, so it is more convenient for catheter entry, and its anatomical position has less variation, obvious marking, and easy confirmation.
The right internal jugular vein is selected as the puncture point, and the success rate can reach more than 90%
.

There are three methods for puncture: anterior, middle or posterior: (1) the lateral side of the carotid artery at the midpoint of the anterior border of the sternocleidomastoid muscle; (2) the junction of the sternocleidomastoid muscle and the clavicular head, that is, the apex of the carotid triangle, to connect the carotid artery.
Push to the inside, the needle axis and the skin are at 30°～45°, and the needle tip points to the ipsilateral nipple; ③ The intersection of the intersection of the mastoid and the inner 1/3 of the midclavicular line and the outer edge of the sternocleidomastoid muscle is equivalent to the level of the cricoid cartilage.
The needle tip is directed towards the clavicle notch—the direction of the ipsilateral sternoclavicular joint
.

A thin pillow is placed under the patient's two shoulder blades, the head is slightly inclined to the opposite side, the neck is stretched, and then the head is lowered 15°~30° in the Qu's position to avoid excessive head tilt and deviation to the opposite side, so as to ensure that the puncture is not suitable.
into the air
.

Routine disinfection of drapes
.

If the patient is awake, local infiltration anesthesia is administered first
.

After positioning, puncture with a 22G, 1.
5-inch (3.
8cm) probe connected to a 5ml syringe, and withdraw the needle while inserting the needle.
Generally, blood can be seen within 1cm~2cm; if no blood is returned after 3cm of needle insertion, keep the puncture needle under negative pressure.
It is slowly withdrawn to the subcutaneous area and probed in a small fan shape at the needle insertion site
.

After successful entry, the direction, angle and depth of needle insertion should be confirmed, and then the test probe should be pulled out, or the needle can be left in its original position
.

Then use the puncture needle to pierce the internal jugular vein according to the puncture direction of the test probe, and the blood return can be seen, and the withdrawal is smooth, then insert the guide wire from the needle cavity, and pay close attention to the change of heart rhythm during the insertion of the guide wire to avoid the guide wire being too deep.
cause arrhythmia
.

Subsequently, the fixed guide wire was withdrawn from the puncture needle, the puncture point was compressed, and the dilation tube was placed along the guide wire to dilate the subcutaneous tissue.
After the dilation was successful, the deep venous catheter was placed
.

After the returning blood is unobstructed, suture and fix it or protect it with a protective film, and connect the central venous pressure measuring tube or infusion.
The pressure measuring tube needs to be flushed with heparin saline to exhaust
.

(2) The right subclavian vein is often used for the access of the subclavian vein.
The patient is supine, the shoulders are raised, the upper limbs are placed on the side of the body and slightly abducted, the clavicle is kept forward, and the clavicle space is opened to facilitate needle insertion.
The puncture point is at At the junction of the middle and inner 1/3 of the clavicle, 1 cm below the clavicle, the puncture needle points to the outside of the ipsilateral sternoclavicular joint, and penetrates the subclavian vein through the space between the clavicle and the first rib.
After the blood return is unobstructed, follow the procedure for intubating the internal jugular vein
.

   4.
Determination of central venous pressure The measurement of central venous pressure includes the water column method and the transducer method.
Since the continuous pressure measurement of the transducer is more accurate and intuitive, it is now commonly used in clinical practice
.

(1) Principle of sensor zero-point setting Prepare a heparin saline bag, put it into a pressure bag, and inflate and pressurize it
.

Flush the transducer and attached extension tube with heparinized saline to vent
.

After successful puncture, connect the transducer with the extension tube and the central venous catheter, connect the transducer with the corresponding monitor lead, open the transducer tee and communicate with the atmosphere, and set the zero point with an atmospheric pressure
.

After the patient is in a good position, the position of the fixed transducer is consistent with the level of the fourth intercostal space (right atrium level) on the midaxillary line
.

(2) Factors affecting the accuracy of pressure readings 1.
Catheter placement depth If the catheter is too deep, the CVP pressure value will be low; if the catheter is too shallow, the CVP value will be high
.

Imaging techniques can be used to determine the placement of the catheter
.

2.
Operator management If the operator is unfamiliar, the liquid is not connected in time after the tube is placed; or there are air bubbles in the pressure measuring pipeline, and the exhaust is not timely; or even the pipeline joints are loose and leaking
.

3.
Zero-point positioning In clinical practice, the level of the middle of the right atrium is generally used as the standard zero-point
.

Keep the heart parallel to the bed to ensure the correct zero point determination
.

4.
Cardiac function, blood volume and vascular tone (Table 4-1)
.

5.
Intrathoracic pressure Mechanical ventilation, patient coughing, breath holding, wound pain, respiratory limitation, and anesthesia and surgical factors can all affect the value of central venous pressure by changing intrathoracic pressure
.

6.
The patency of the pressure measuring system When measuring the pressure, factors such as blood reflux, liquid viscosity, blood clot and other factors can cause the channel to be blocked and affect the accuracy of the pressure measurement value
.

Therefore, intermittent flushing with heparin saline is often used in clinical practice to ensure the smoothness of the pressure measurement system
.

 V.
Composition and clinical significance of CVP pressure waveform (1) Composition of CVP pressure waveform CVP basically reflects the change of right atrial pressure.
The CVP waveform generally consists of 3 peaks a, c, v and negative waves x, y, a total of 5 Wave composition, the last component of the CVP waveform is the h wave, which cannot be detected in normal conditions unless the heart rate is slow or the venous pressure is elevated (Figure 1)
.

1.
The a wave is located after the P wave of the ECG, reflecting the systolic function of the right atrium, and its role is to discharge blood to the right ventricle at the end of the right ventricular diastole
.

2.
The c wave is located after the QRS complex and is caused by a transient increase in right atrial pressure due to the contraction of the right ventricle, the closure of the tricuspid valve and the protrusion of the right atrium
.

3.
X wave After the c wave, as the right ventricle continues to contract, the right atrium begins to dilate, resulting in a rapid drop in right atrial pressure
.

4.
The v wave is located after the x wave and is the result of rapid filling of the right atrium due to relaxation
.

5.
The y wave is located after the v wave and is caused by the rapid emptying of the right atrium due to the opening of the tricuspid valve
.

6.
The h wave is located after the y wave and occasionally manifests as a pressure plateau in the middle and late diastole
.

 Figure 1 The normal CVP waveforms are clearly marked for both diastolic components (y-descending, end-diastolic a wave) and systolic components (c-wave, x descending, and end-systolic v-wave)
.

Due to the slow heart rate, a mid-diastolic plateau waveform, or h wave, can also be seen
.

Waveform identification is aided by the temporal relationship between each waveform composition and the R-wave of the ECG
.

The waveform time of the arterial pressure (ART) trajectory is easily confused, which is due to the relative delay of the ascending branch of systolic arterial pressure.
(2) The clinical significance of CVP pressure waveform changes 1.
In sinus tachycardia, the a and c waves Fusion; in atrial fibrillation, the a waves disappear
.

2.
When the emptying of the right atrium is blocked, the a wave increases and becomes larger, which is more common in right ventricular hypertrophy, tricuspid valve stenosis, acute lung injury, chronic obstructive pulmonary disease, cardiac tamponade, constrictive pericarditis, pulmonary hypertension,
etc.

3.
The v wave increases during tricuspid regurgitation; the a and v waves increase when the right ventricular compliance decreases
.

4.
During acute tamponade, the x-wave becomes steeper and the y-wave becomes flat
.

 VI.
Clinical significance of monitoring CVP Clinical monitoring of CVP is mainly used to evaluate the return blood volume and right ventricular ejection function.
The normal range of CVP is 1~7 mmHg, less than 1 mmHg indicates insufficient circulating volume, and greater than 7 mmHg indicates right ventricular dysfunction or overcapacity In clinical practice, the changes of CVP should be dynamically observed and combined with arterial blood pressure to make a comprehensive judgment (see Table 4-1)
.

When determining CVP, attention should be paid to completing the zero point calibration in time
.

Table 4-1 Causes of CVP changes and treatment of CVP Arterial pressure Clinical judgment and measures to be taken , Diuresis, correct acidosis, properly control fluid replacement or use vasodilators cautiously, high normal volume vasoconstriction, increased pulmonary circulatory resistance to control fluid replacement, vasodilators to dilate volume vessels and pulmonary vascular normal, low cardiac output, reduced cardiac output, cardiotonic, fluid replacement In the test, if the blood volume is too large, the blood vessels are excessively contracted, and the blood volume is insufficient or the blood volume is insufficient.
7.
Complications Central venous puncture is an invasive operation.
and comprehensive understanding of complications that may occur during monitoring
.

Relevant complications mainly include the following aspects: 1.
Damage to blood vessels and heart, and pericardial tamponade may occur in severe cases.
This is mainly due to the deep insertion of the catheter, causing perforation of the right atrium.
Once it occurs, it is almost difficult to rescue
.

The pericardial tamponade is a fatal pericardial tamponade due to the insertion of the catheter into the pericardial cavity, causing pericardial effusion
.

The main clinical manifestations of pericardial tamponade include sudden dyspnea, cyanosis, restlessness, retrosternal pain, and distended jugular veins, accompanied by hypotension, azygos pulses, and low and distant heart sounds
.

2.
Pneumothorax, hemothorax or hemopneumothorax Mainly due to puncture of the pleura or penetration of veins or arteries and pleura during the procedure
.

When the puncture is difficult, the patient has a severe cough during the puncture, and the patient has difficulty breathing and the ipsilateral breath sound decreases after the puncture, the possibility of pneumothorax should be considered.
Drainage
.

During puncture, the apex of the lung is damaged, resulting in localized pneumothorax.
The patient may have no clinical symptoms, and the small puncture in the lung can also close on its own
.

However, if the patient is mechanically ventilated after puncture, it may cause tension pneumothorax, leading to serious consequences
.

3.
Bleeding and hematoma are often caused by accidental injury to the artery during puncture
.

The hematoma was not obvious after compression
.

Patients who need anticoagulation therapy due to disease have a high incidence of hematoma.
Once it occurs, please consult relevant departments if necessary
.

4.
Air embolism Air may enter the blood vessel through the needle hole or the catheter when changing the connector, syringe, and checking whether the catheter is in place
.

Especially after subclavian vein puncture, because the venous pressure is relatively low, it can be negative pressure during inhalation, which increases the probability of air embolism
.

5.
Thrombophlebitis and infection Patients who need to indwell catheters for a long time after surgery may develop thrombophlebitis; in addition, infection may occur due to repeated puncture during the operation or the lack of strict aseptic manipulation
.

When the patient has inflammatory reactions such as chills, fever, increased blood count, tenderness or redness at the puncture site that cannot be explained by the original disease, the catheter should be removed and the catheter sample should be collected for bacterial culture
.

8.
Prevention and treatment of puncture-related complications (1) puncture-related infection 1.
When placing a central venous catheter, strict aseptic technique should be used
.

2.
For immunocompromised patients, in addition to strict aseptic operation, antibiotics should be given preventively according to the patient's condition, but should not be used routinely
.

3.
Antibiotics or coated catheters such as chlorhexidine and silver sulfadiazine should be selected based on infection risk, economic cost, and expected catheterization time
.

But insertion of an antimicrobial-coated catheter is not a substitute for other infection prevention measures
.

4.
The selection of the puncture site should be based on clinical needs, while taking into account that the puncture site should avoid contaminated areas or areas that may be contaminated or prone to contamination (such as burns or infected skin, adjacent to tracheostomy or open surgical wounds)
.

Adults should choose upper body puncture points as much as possible to reduce the incidence of infection
.

5.
Secure the catheter with sutures, staples, or sterile tape, and apply a transparent occlusive biological dressing to protect the central venous catheter from infection
.

6.
When injecting or aspirating through an existing central venous catheter, the catheter access port should be sterilized before each procedure and should be closed and covered when not in use
.

7.
Check the catheter insertion site daily for symptoms of infection.
When catheter-related infection is suspected, the catheter should be removed, and the puncture point should be replaced to re-puncture the catheter
.

8.
The duration of catheter indwelling should be determined based on clinical needs
.

(2) Prevention of mechanical trauma 1.
The selection of catheter puncture sites should be based on clinical needs and physician judgment, experience and skills
.

For adults, the upper body should be considered for the catheter insertion site to minimize the risk of thrombotic complications
.

2.
Selection of catheter size and model should be based on clinical needs to select the smallest size catheter
.

3.
The choice of the Seldinger technique (penetration method) or the modified Seldinger technique (penetration method) for catheter placement should be based on clinical needs and the operator's skills and experience
.

Before the dilator or large lumen catheter is placed, it is necessary to confirm that the guide wire is in the vein.
At this time, the use of the modified Seldinger technique can provide a more stable venous access
.

4.
During puncture and catheterization, ultrasound imaging can be used to guide blood vessel positioning and determine blood vessel patency
.

5.
After the catheter is placed through the guide needle, it should be determined that the catheter is in the vein.
Methods include ultrasound, manometry, pressure waveform analysis, and venous blood gas, etc.
, and should not be judged based on blood color or pulsatile blood flow.

.

6.
After the catheter is placed, the position of the catheter tip needs to be confirmed, including chest X-ray, fluoroscopy, and continuous electrocardiogram; position and consult a general surgery, vascular, or interventional radiologist immediately to discuss surgical or non-surgical removal of the catheter
.

8.
Lung injury and pneumothorax The direction and depth of needle insertion should be strictly controlled.
Once symptoms of lung compression such as dyspnea and decreased breath sounds occur during puncture, high alert should be exercised, the catheter should be withdrawn immediately, imaging examinations should be performed and corresponding treatment should be performed.

.

After evaluating and appropriately managing these injuries, anesthesiologists and surgeons should weigh the pros and cons before deciding whether to perform elective surgery
.

9.
Ultrasound-guided central venous puncture cannulation The commonly used central venous puncture and cannulation operation has certain risks, which can cause the above-mentioned adverse complications
.

At present, a large number of clinical studies at home and abroad have shown that compared with the empirical blind method, ultrasound-guided deep vein puncture can significantly improve the success rate of puncture and cannulation, reduce the time and frequency of puncture, and reduce the occurrence of related complications
.

(1) Internal jugular vein puncture and cannulation At present, the commonly used clinical ultrasound-guided internal jugular vein puncture cannulation is mainly the right internal jugular vein puncture
.

Before the ultrasound-guided puncture operation, the probe should be used to find the internal jugular vein and artery first, to determine the specific location of the vein, and to avoid accidental perforation of the artery
.

Ultrasound positioning and specific puncture methods: (1) Routine disinfection of the puncture site and draping of towels; (2) Preparation of the ultrasonic probe: First, the probe should be disinfected, the couplant should be applied on the probe, and the probe and its connection should be wrapped with a sterile sleeve; (3) Ultrasound Image: Apply sterile paraffin oil and couplant to the patient's puncture site, keeping fluid between the skin and the probe at all times
.

A cross-sectional ultrasound image of the internal jugular vein can be obtained by placing the probe perpendicular to the longitudinal axis of the neck at the upper end of the carotid triangle (Figure 2)
.

The internal jugular vein is round or oval, and the diameter of the vein is significantly reduced or even atresia when the probe is pressurized
.

The superficial part is the sternocleidomastoid muscle, and the inner part is the carotid artery
.

Place the probe parallel to the longitudinal axis of the neck at the upper end of the carotid triangle slightly downward to obtain a longitudinal ultrasound image of the internal jugular vein (Figure 3)
.

⑷ Operation: After determining the marked side of the probe, the distance between the probe and the probe is 0.
5cm～1.
0cm, the puncture needle and the skin are at 30°～45°, and the probe and the puncture needle are on the same plane to ensure that the puncture needle and the vein are displayed on the screen at the same time, and The puncture needle needs to be within the ultrasound field of view
.

After the needle tip entered the blood vessel, the syringe was withdrawn and the blood returned smoothly, indicating that the oblique opening of the puncture needle was completely located in the internal jugular vein, and further routine catheterization was performed
.


Fig.
2 Two-dimensional images of carotid artery and internal jugular vein ultrasound cross-sectionFig.
3 Two-dimensional images of internal jugular vein ultrasound longitudinal puncture and catheterization Cross-sectional ultrasound image, keeping parallel to the direction of the probe, and inserting the needle from the outside of the probe
.

The disadvantage of this method is that the direction of needle insertion is perpendicular to the vein, and there will be resistance and difficulty in placing the guide wire and catheter
.

 Fig.
4 Schematic diagram of short-axis in-plane technique of internal jugular vein puncture ②Short-axis out-of-plane technique (Fig.
5): Place the probe vertically to obtain an ultrasound image of the internal jugular vein cross-section
.

The disadvantage of this method is that the position of the needle tip cannot be seen, so it is necessary to pay attention to the depth of needle insertion, which is generally not more than 4cm
.

There are few difficulties in placing guidewires and catheters with this method
.

Figure 5 Schematic diagram of the short-axis out-of-plane technique of internal jugular vein puncture ③ Long-axis in-plane technique (Fig.
6): Obtain the ultrasound image of the longitudinal section of the internal jugular vein
.

Insert the needle from the side of the probe head, and the needle insertion direction is parallel to the probe
.

This method is convenient and reliable when the patient's neck is long or the length of the probe is small
.

 Figure 6 Schematic diagram of the long-axis in-plane technique of internal jugular vein puncture (2) Ultrasound-guided deep subclavian vein puncture and cannulation is rarely used clinically
.

The specific method refers to the traditional empirical puncture and catheterization method
.

Routinely sterilize the towel, prepare the ultrasound probe so that its flat surface touches the skin, use the probe to scan the direction of blood vessels laterally or longitudinally, find the blood vessel cross section (Figure 7) or longitudinal section (Figure 8), and clearly detect the subclavian vein and artery
.

It is still necessary to ensure that the probe and the puncture needle are on the same plane, and the puncture needle is within the ultrasound field of view
.

After the needle tip entered the blood vessel, the syringe was withdrawn, and the blood returned smoothly.
The oblique opening of the puncture needle was completely located in the subclavian vein, and the catheter was further routinely fixed
.

 Figure 7 Ultrasound cross-sectional two-dimensional image of the subclavian veinFigure 8 The two-dimensional image of the subclavian vein ultrasound longitudinal section References are briefly asked: ① the meaning of CVP waveform ② the main points of ultrasound-guided central venous puncture ③ the causes and treatment of CVP changes Welcome to leave a message~ ~Thank you for your support and encouragement to move forward~~Recommended reading: Mr.
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