Research progress on the influencing factors of perioperative right heart function in patients with thoracic surgery

Authors: Yan Yan, Xie Fenglei, Ge Xiaoyan, Zhao Tengfei, Liu Wei, Du Kai, Department of Anesthesiology, Bozhou Hospital (Bozhou People's Hospital) affiliated to Anhui Medical University

The incidence of postoperative cardiovascular complications in patients with thoracic surgery is significantly higher than that of other types of surgery, which seriously affects the prognosis of
patients.
The postoperative right heart ejection fraction of patients with thoracic surgery can be reduced by 15% to 25% and lasted until 2 months after surgery, which significantly increases the incidence
of postoperative cardiopulmonary complications.
Decreased right heart function is mainly related
to preload, afterload, and myocardial contractility.

1.
Functional characteristics of the right heart in patients with thoracic surgery

Most of the patients with thoracic surgery are elderly patients, and most patients with chest surgery have different degrees of lung disease before surgery, such as chronic obstructive lung disease (COPD), interstitial lung disease, pulmonary fibrosis and obesity-related lung disease
.
Pulmonary artery hypertension (PAH) is pulmonary artery ≥ 25mmHg
on average.
Chronic lung disease is the second leading cause of PAH
.
Among them, the prevalence of PAH in patients with COPD is about 10% to 30%, and PAH is related to
the severity of COPD.
With idiopathic pulmonary fibrosis, the incidence of PAH can increase to 30% to 50%.

In patients with long-term concomitant PAH, long-term right ventricular pressure and volume overload, right ventricular remodeling, increased wall stress, decreased myocardial contractility, progressive tricuspid regurgitation, decreased effective cardiac output, and eventually right heart insufficiency
.
When pulmonary artery pressure exceeds 40 mmHg, the right ventricular ejection fraction decreases
in patients with normal right heart function.
In addition, increased right ventricular pressure and volume also reduces coronary blood flow and worsens right heart ischemia
.
Therefore, a full preoperative assessment of pulmonary artery pressure and right heart function is necessary
.

2.
Factors influencing the function of the right heart during perioperative period in patients with thoracic surgery

Single-lung ventilation: One-lung ventilation (OLV) is an important component of
anesthesia in thoracic surgery.
Anesthesiologists use a dual-lumen tracheal catheter or bronchial occlusion device to achieve lung isolation, causing the affected lung to collapse to expose the surgical field of vision and facilitate surgical operation
.
Hypoxemia and hypercapnia are often associated with increased intrapulmonary shunt and dead ventilation during OLV due to lung collapse on the affected side and atelectasis on the
healthy side.
Hypercapnia (PaCO2>48mmHg) is an independent predictor
of right-sided cardiac insufficiency in patients with chronic obstructive pulmonary disease who receive microtidal volume mechanical ventilation.
Both hypoxemia and hypercapnia can cause pulmonary vasoconstriction, resulting in increased right-sided epicardial afterload and decreased
right-hand artiac function.
In addition, hypoxia can also cause hypoxic ischemic cardiomyocyte death, leading to a decline in right heart function and even right heart failure
.

Netzer et al.
evaluated the right ventricular morphology of healthy subjects using transthoracic echocardiograms, and the results showed that hypoxemia can cause significant changes in right ventricular morphology, which is not proportional
to the estimated increase in pulmonary artery pressure.
At present, it is uncertain whether hypercapnia and/or hypoxemia can predict right-heart function
in healthy lung patients with OLV.
Although permissible hypercapnia is thought to have some lung-protective effect, it should be avoided in patients with thoracic surgery with
decreased right heart function.

Ventilation strategies: intraoperative non-physiological mechanical ventilation can independently adversely affect lung and right heart function and lead to ventilator-induced lung injury (VILI) and decreased
right heart function through different mechanisms.
Studies have shown that compared with traditional mechanical ventilation strategies, lung protective ventilation (LPV) can improve intraoperative oxygenation and lung compliance in patients with thoracoscopic surgery, reduce the degree of perioperative decline in T cells and NK cells, and reduce intraoperative IL-6 and C-reactive protein concentrations
in patients with coronary heart disease.

LPV consists mainly of
small tidal volume, positive end-expiratory pressure (PEEP), and/or alveolar recruitment maneuver (ARM).
Factors that affect cardiopulmonary function include:

(1) The amount of
moisture.
Volume injuries can be caused by high tide gas volume (>8 to 10 ml/kg), and barotrauma caused by high airway pressure (> 28 cmH2O) can affect mechanical ventilation lung function, and VILI and increased right-sided ventricular afterload are related
.
At the same time, VILI leads to a rapid increase in inflammatory mediators in the circulatory system, which can induce a decrease in right heart function within a
few hours.
Cherpanath et al.
compared the effects of different levels of tidal volume during mechanical ventilation on cardiac function in non-ARDS patients, and the results showed that compared with small tidal volume, moderate level tidal volume could lead to a decrease in the contractile function of the left and right ventricles of the patient, and a decrease in cardiac output, and did not affect the diastolic function
of the left and right ventricles of the patient.

（2）PEEP
。 As a core component of LPV, a certain level of PEEP can maintain the open state of alveoli, effectively reduce the occurrence of atelectasis during mechanical ventilation, and reduce the degree
of VILI.
However, the use of PEEP during mechanical ventilation often leads to an increase in intrathoracic pressure, venous reflux resistance and right-sided epicardiac afterload, limiting left ventricular diastolic filling and a decrease in
cardiac output 。 Kim et al.
compared the effects of applying different levels of PEEP during OLV on cardiac function in patients, and the results showed that compared with 0cmH2OPEEP and 5cmH2OPEEP, the right ventricular myocardial performance index [(isovolume contraction time + isotodiastolic time)÷ ejection time] was higher at 10cmH2OPEEP, and the right ventricular area change fraction was lower, and the right ventricular function gradually decreased
with the increase of PEEP level.

（3）ARM
。 ARM is one of the components of protective OLV, which can reverse the atelectasis induced by ARM anesthesia, prevent the release of inflammatory cytokines mediated by atelectasis, and exert lung protection
.
The incidence of acute lung injury after surgery (3.
1% to 4.
2%) was significantly higher in patients requiring OLV for pulmonectomy than in patients (1.
9% to 2.
6%)
after general surgery.

Non-operative lungs may be more likely to have atelectasis
due to pressure applied to the mediastinum, abdominal cavity, and outside the chest cavity.
During mechanical ventilation in patients with thoracic surgery, the application of ARM can increase the pulmonary volume at the end of expiratory by 20%, and at the same time reduce driving pressure, increase lung compliance, increase PO2, reduce hypoxic pulmonary vasoconstriction, and reduce right-sided heart afterload, and this effect can be maintained for 60 minutes
.
However, when performing ARM, it can lead to a rapid increase in intrathoracic pressure, a decrease in the right ventricular preload, an increase in the afterload, a decrease in the right ventricle stroke volume, and a decrease in cardiac output
.
Therefore, it is necessary to closely evaluate the circulating volume and monitor hemodynamics when performing ARM
.
The application of LPV in thoracic surgery has an indirect right heart protection effect, individualized LPV can maximize the lung protection effect, and the effect of individualized LPV on perioperative right heart function in patients with thoracic surgery needs to be confirmed
by a large number of clinical studies.

Ventilation mode: Mechanical ventilation may play an important role
in the decline of right-sided heart function.
Pressure-controlled ventilation (PCV) and volume-controlled ventilation (VCV) are commonly used ventilation modes during OLV, which ensures stable and accurate tidal volume, but produces higher airway peak pressure (Ppeak) resulting in barotrauma and uneven
gas distribution in the lungs 。 PCV is able to lower Ppeak, improve arterial oxygenation, rapidly slow inspiratory flow rates, and downregulate levels of pro-inflammatory factors such as TNF-a and IL-6, but the tone generated by PCV patterns on the lungs and alveoli may be related
to lung damage.
Therefore, the optimal ventilation mode during OLV remains controversial
.

Al et al.
evaluated the effect of PCV versus VCV on right ventricular function by transesophageal echocardiography, and compared with VCV, patients applying PCV during OLV had faster systolic and diastolic tricuspid annular rings, and differences in right heart function may be associated
with a 30% reduction in airway pressure in patients receiving PCV mode.
The pressure-controlled ventilation-volume guaranteed (PCV-VG) mode is a new ventilation mode
that can be used during OLV.

In PCV-VG mode, the initially preset tidal volume is transmitted
through a deceleration stream at low airway pressure.
After calculating the patient's lung compliance and inspiratory pressure, the ventilator can automatically adjust the airway pressure for the next breath based on the last measured tidal volume
.
Studies have shown that compared with VCV, the Ppeak is lower during the application of the PCV-VG mode, the lung compliance is greater, and the incidence of pulmonary complications in patients after 1 day of surgery is significantly reduced
.
At present, the effect of PCV-VG on the function of the right heart in patients during OLV is worth further exploration
.

Surgery: At present, thoracic surgery mainly includes open chest and thoracoscopic surgery
.
Thoracoscopic surgery has less trauma, faster postoperative recovery, and lower
complication rates than thoracoscopic surgery.
The effects of the two surgical modalities on the function of the right heart remain controversial
.
Compared with traditional thoracoscopic surgery, the right ventricular Tei index and pulmonary vascular resistance are lower after thoracoscopic surgery, the right ventricular ejection fraction is higher, and the Tei index can be restored to the preoperative level 1 month after thoracoscopic surgery, while the open chest surgery can not be restored to the preoperative level
until 3 months after surgery.
However, studies such as Gonzalez-Tallada have shown no statistically significant difference in plasma troponin I concentrations in patients after the two surgical modalities
.
Therefore, the effects of thoracoscopy and open chest on the function of the right heart in patients still need further clinical research and exploration
.

Analgesic mode: The main causes of postoperative pain in patients with open chest surgery include retraction of the ribs, fractures and dislocation of the costal vertebrae, intercostal nerve injury, and stimulation of the pleura after the placement of a thoracic drainage tube
.
Although thoracoscopy can significantly improve postoperative pain, the incidence of chronic pain after thoracoscopic surgery is still as high as 25%, and effective postoperative analgesia can significantly reduce the incidence
of chronic pain.

Thoracic epidural analgesia (TEA) is an effective analgesic method after thoracic surgery, the analgesic effect is exact, can significantly reduce the incidence of postoperative pulmonary complications, analgesia at the same time anesthesia area arteriovenous dilation, venous return blood volume decreases, can reduce
the right heart preload.
Different ranges of blockage can affect cardiac afterload to varying degrees, lowering blood pressure and slowing down heart rate
.
In addition, studies such as Bulte have shown that TEA may also cause different degrees of cardiac sympathetic blockade, regulate myocardial blood flow through α and β receptors on myocardial blood vessels, dilate the heart microvessels, and increase myocardial blood flow
.
TEA has a protective effect
on the cardiovascular system.
However, Wink et al.
have shown that general anesthesia combined with TEA can weaken the right ventricular degeneration effect, slow down the right heart isovolume contraction, and reduce the right heart contraction
.

Therefore, TEA
should be used with caution in patients with right-sided ventricular insufficiency and pulmonary hypertension.
With the development of ultrasound visualization technology, thoracic nerve block has been widely used in thoracic surgery, including paravertebral nerve block, anterior serration plane block, vertical spinal muscle plane block and laminar block, etc.
, which can provide good analgesic effects
.
However, there are few reports of the effects of thoracic nerve blocks on right-sided heart function, and more clinical studies are needed to explore
them.

Fluid management: intraoperative fluid management strategies are associated
with prognosis in patients undergoing thoracic surgery.
Volume overload can lead to pulmonary edema and worsen right-sided epicardial afterload
.
Effective prevention of intraoperative volume overload can significantly reduce the incidence of postoperative pulmonary complications, and although the restrictive infusion strategy can reduce the preload of the right heart during surgery, it is easy to cause tissue hypoperfusion, resulting in postoperative renal insufficiency and acute kidney injury
.
In recent years, with the development of accelerated rehabilitation surgery concepts, goal-directed fluid therapy (GDFT) has become a hot topic
in clinical research.

Kaufmann et al.
have shown that the application of esophageal ultrasound-guided intraoperative GDFT during lobectomy can reduce the application of intraoperative vasoactive drugs and significantly reduce the incidence
of postoperative pulmonary complications in patients.
Li Guanzhu's systematic evaluation showed that the application of GDFT in thoracic surgery can effectively improve the intraoperative oxygenation, oxygen supply and cardiac index, reduce blood lactate levels, and reduce the incidence
of postoperative lung infection.
Therefore, the use of GDFT in thoracic surgery has the potential to improve the decline in right-sided heart function mediated by single-lung ventilation, lung injury, and volume overload
.

3.
Summary

Factors affecting the function of the right heart in patients undergoing thoracic surgery throughout the perioperative period
.
Prior to thoracic surgery, the anesthesiologist should fully assess the patient's pulmonary artery pressure and right heart function
.
The application of LPV during mechanical ventilation can effectively reduce the effect
of OLV-related complications on right-hand heart function.
Before ARM is implemented, attention should be paid to assessing the patient's volume status to avoid the effect of sharp changes in the pre- and post-post-load of the right heart on
the patient's right heart function.

Since TEA is able to block the sympathetic nerve of the heart, it should be used with caution in patients with pulmonary hypertension and right-sided heart insufficiency
.
Intraoperative GDFT reduces pulmonary complication and may have potential right-sided heart protection
.
With the continuous development of accelerated rehabilitation surgical concepts, individualized right-sided heart protective ventilation strategies, accurate analgesic effects, analgesic modes with less sympathetic effects, and more accurate fluid management will become the focus
of thoracic anesthesia.

Source: Yan Yang, Xie Fenglei, Ge Xiaoyan, Zhao Tengfei, Liu Wei, Du Kai.
Research progress on influencing factors of perioperative right heart function in patients undergoing thoracic surgery[J].
Journal of Clinical Anesthesiology,2022,38(03):318-321.