Inhaled nitric oxide administration during one-lung ventilation in patients undergoing thoracic surgery

Inhaled pulmonary vasodilators: a narrative review

Pulmonary hypertension (PH) is a severe disease that affects people of all ages. It can occur as an idiopathic disorder at birth or as part of a variety of cardiovascular and pulmonary disorders. Inhaled pulmonary vasodilators (IPV) can reduce pulmonary vascular resistance (PVR) and improve RV function with minimal systemic effects. IPV includes inhaled nitric oxide (iNO), inhaled aerosolized prostacyclin, or analogs, including epoprostenol, iloprost, treprostinil, and other vasodilators. In addition to pulmonary vasodilating effects, IPV can also be used to improve oxygenation, reduce inflammation, and protect cell. Off-label use of IPV is common in daily clinical practice. However, evidence supporting the inhalational administration of these medications is limited, inconclusive, and controversial regarding their safety and efficacy. We conducted a search for relevant papers published up to May 2020 in four databases: PubMed, Google Scholar, EMBASE and Web of Science. This review demonstrates that the clinical using and updated evidence of IPV. iNO is widely used in neonates, pediatrics, and adults with different cardiopulmonary diseases. The limitations of iNO include high cost, flat dose-response, risk of significant rebound PH after withdrawal, and the requirement of complex technology for monitoring. The literature suggests that inhaled aerosolized epoprostenol, iloprost, treprostinil and others such as milrinone and levosimendan may be similar to iNO. More research of IPV is needed to determine acceptable inclusion criteria, long-term outcomes, and management strategies including time, dose, and duration.

Intraoperative Anesthetic Management of the Thoracic Patient

The intraoperative anesthetic management for thoracic surgery can impact a patient's postoperative course, especially in patients with significant lung disease. One-lung ventilation poses an inherent risk to patients, including hypoxemia, acute lung injury, and right ventricular dysfunction. Patient-specific ventilator management strategies during one-lung ventilation can reduce postoperative morbidity.

Effects of Inhaled Iloprost on Lung Mechanics and Myocardial Function During One-Lung Ventilation in Chronic Obstructive Pulmonary Disease Patients Combined With Poor Lung Oxygenation

BACKGROUND

The ventilation/perfusion mismatch in chronic obstructive pulmonary disease (COPD) patients can exacerbate cardiac function as well as pulmonary oxygenation. We hypothesized that inhaled iloprost can ameliorate pulmonary oxygenation with lung mechanics and myocardial function during one-lung ventilation (OLV) in COPD patients combined with poor lung oxygenation.

METHODS

A total of 40 patients with moderate to severe COPD, who exhibited the ratio of partial pressure of arterial oxygen to the fraction of inspired oxygen (PaO2/FIO2) <150 mm Hg 30 minutes after initiating OLV, were enrolled in this study. Patients were randomly allocated into either ILO group (n = 20) or Control group (n = 20), in which iloprost (20 μg) and saline were inhaled, respectively. The PaO2/FIO2 ratio, dead space, dynamic compliance, and tissue Doppler imaging with myocardial performance index (MPI) were assessed 30 minutes after initiating OLV (pre-Tx) and 30 minutes after completion of drug inhalation (post-Tx). Repeated variables were analyzed using a linear mixed-model between the groups.

RESULTS

At pre-Tx, no differences were observed in measured parameters between the groups. At post-Tx, PaO2/FIO2 ratio (P < .001) and dynamic compliance (P = .023) were significantly higher and dead space ventilation was significantly lower (P = .001) in iloprost group (ILO group) compared to Control group. Left (P = .003) and right ventricular MPIs (P < .001) significantly decreased in ILO group compared to Control group.

CONCLUSIONS

Inhaled iloprost improved pulmonary oxygenation, lung mechanics, and cardiac function simultaneously during OLV in COPD patients with poor lung oxygenation.

A Simple Effective Pharmacological Treatment of Hypoxemia During One-Lung Ventilation

Hypoxemia during one-lung ventilation is a challenge in the clinical practice. Moving from the results of the study conducted by Choi et al., we discuss the possibility to modulate hypoxemia by administering iloprost via inhalation, in the light of the physiological mechanisms.

The Effects of Iloprost on Oxygenation During One-Lung Ventilation for Lung Surgery: A Randomized Controlled Trial

Hypoxemia can occur during one-lung ventilation (OLV) in thoracic surgery, leading to perioperative complications. Inhaled iloprost is a selective pulmonary vasodilator with efficacy in patients with pulmonary hypertension. The purpose of this study was to evaluate the effects of off-label inhaled iloprost on oxygenation during OLV in patients undergoing lung surgery. Seventy-two patients who were scheduled for elective video-assisted thoracoscopic lobectomy were assigned to receive an inhaled nebulizer of distilled water (control group), 10 μg iloprost (IL10 group), or 20 μg iloprost (IL20 group). Arterial and venous blood gas and hemodynamic analyses were obtained. Changes in partial pressure of oxygen in arterial blood (PaO₂), after the initiation of OLV and the resumption two-lung ventilation (TLV), were similar in all three groups. However, PaO₂ in the IL10 group was comparable to that in the control group, whereas PaO₂ in the IL20 group was significantly higher than that in the control group at 10, 20, and 30 min after administration of iloprost (275.1 ± 50.8 vs. 179.3 ± 38.9, p < 0.0001; 233.9 ± 39.7 vs. 155.1 ± 26.5, p < 0.0001; and 224.6 ± 36.4 vs. 144.0 ± 22.9, p < 0.0001, respectively). The shunt fraction in the IL20 group was significantly higher than that in the control group after administration of iloprost (26.8 ± 3.1 vs. 32.2 ± 3.4, p < 0.0001; 24.6 ± 2.2 vs. 29.9 ± 3.4, p < 0.0001; and 25.3 ± 2.0 vs. 30.8 ± 3.1, p < 0.0001, respectively). Administration of inhaled iloprost during OLV improves oxygenation and decreases intrapulmonary shunt.

The Right Ventricle During Selective Lung Ventilation for Thoracic Surgery

The right ventricle (RV) has been an area of evolving interest after decades of being ignored and considered less important than the left ventricle. Right ventricular dysfunction/failure is an independent predictor of mortality and morbidity in cardiac surgery; however, very little is known about the incidence or impact of RV dysfunction/failure in thoracic surgery. The pathophysiology of RV dysfunction/failure has been studied in the context of acute respiratory distress syndrome (ARDS), cardiac surgery, pulmonary hypertension, and left ventricular failure, but limited data exist in literature addressing the issue of RV dysfunction/failure in the context of thoracic surgery and one-lung ventilation (OLV). Thoracic surgery and OLV present as a unique situation where the RV is faced with sudden changes in afterload, preload, and contractility throughout the perioperative period. The authors discuss the possible pathophysiologic mechanisms that can affect adversely the RV during OLV and introduce the term RV injury to the myocardium that is affected adversely by the various intraoperative factors, which then makes it predisposed to acute dysfunction. The most important of these mechanisms seems to be the role of intraoperative mechanical ventilation, which potentially could cause both ventilator-induced lung injury leading to ARDS and RV injury. Identification of at-risk patients in the perioperative period using focused imaging, particularly echocardiography, is paramount. The authors also discuss the various RV-protective strategies required to prevent RV dysfunction and management of established RV failure.

Management of Pulmonary Hypertension in the Operating Room

Pulmonary artery hypertension is defined as persistent elevation of mean pulmonary artery pressure > 25 mm Hg with pulmonary capillary wedge pressure < 15 mm Hg or elevation of exercise mean pulmonary artery pressure > 35 mm Hg. Although mild pulmonary hypertension rarely impacts anesthetic management, severe pulmonary hypertension and exacerbation of moderate hypertension can lead to acute right ventricular failure and cardiogenic shock. Knowledge of anesthetic drug effects on the pulmonary circulation is essential for anesthesiologists. Intraoperative management should include prevention of exacerbating factors such as hypoxemia, hypercarbia, acidosis, hypothermia, hypervolemia, and increased intrathoracic pressure; monitoring and optimizing right ventricular function; and treatment with selective pulmonary vasodilators. Recent advances in pharmacology provide anesthesiologists with a wide variety of options for selective pulmonary vasodilatation. Pulmonary hypertension is a major determinant of perioperative morbidity and mortality in special situations such as heart and lung transplantation, pneumonectomy, and ventricular assist device placement.

Pulmonary Hypertensive Crisis on Induction of Anesthesia

Anesthesia for lung transplantation remains one of the highest risk surgeries in the domain of the cardiothoracic anesthesiologist. End-stage lung disease, pulmonary hypertension, and right heart dysfunction as well as other comorbid disease factors predispose the patient to cardiovascular, respiratory and metabolic dysfunction during general anesthesia. Perhaps the highest risk phase of surgery in the patient with severe pulmonary hypertension is during the induction of anesthesia when the removal of intrinsic sympathetic tone and onset of positive pressure ventilation can decompensate a severely compromised cardiovascular system. Severe hypotension, cardiac arrest, and death have been reported previously. Here we present 2 high-risk patients for lung transplantation, their anesthetic induction course, and outcomes. We offer suggestions for the safe management of anesthetic induction to mitigate against hemodynamic and respiratory complications.

Hypoxic pulmonary vasoconstriction: physiology and anesthetic implications

Hypoxic pulmonary vasoconstriction (HPV) represents a fundamental difference between the pulmonary and systemic circulations. HPV is active in utero, reducing pulmonary blood flow, and in adults helps to match regional ventilation and perfusion although it has little effect in healthy lungs. Many factors affect HPV including pH or PCO2, cardiac output, and several drugs, including antihypertensives. In patients with lung pathology and any patient having one-lung ventilation, HPV contributes to maintaining oxygenation, so anesthesiologists should be aware of the effects of anesthesia on this protective reflex. Intravenous anesthetic drugs have little effect on HPV, but it is attenuated by inhaled anesthetics, although less so with newer agents. The reflex is biphasic, and once the second phase becomes active after about an hour of hypoxia, this pulmonary vasoconstriction takes hours to reverse when normoxia returns. This has significant clinical implications for repeated periods of one-lung ventilation.

Hypoxic pulmonary vasoconstriction

It has been known for more than 60 years, and suspected for over 100, that alveolar hypoxia causes pulmonary vasoconstriction by means of mechanisms local to the lung. For the last 20 years, it has been clear that the essential sensor, transduction, and effector mechanisms responsible for hypoxic pulmonary vasoconstriction (HPV) reside in the pulmonary arterial smooth muscle cell. The main focus of this review is the cellular and molecular work performed to clarify these intrinsic mechanisms and to determine how they are facilitated and inhibited by the extrinsic influences of other cells. Because the interaction of intrinsic and extrinsic mechanisms is likely to shape expression of HPV in vivo, we relate results obtained in cells to HPV in more intact preparations, such as intact and isolated lungs and isolated pulmonary vessels. Finally, we evaluate evidence regarding the contribution of HPV to the physiological and pathophysiological processes involved in the transition from fetal to neonatal life, pulmonary gas exchange, high-altitude pulmonary edema, and pulmonary hypertension. Although understanding of HPV has advanced significantly, major areas of ignorance and uncertainty await resolution.

Anesthetic Considerations for Lung Transplantation

Lung transplantation is the definitive treatment for end-stage lung disease. The number of lung transplantations performed is limited by the number of donors available and is far outnumbered by the potential recipients on the waiting list. Advances in surgical methods, organ preservation, and immunosuppression have decreased the morbidity and mortality associated with this procedure during the last few decades. Specific anesthetic concerns are associated with lung transplantation, including careful preoperative assessment of pulmonary and cardiac function, adequate venous access and monitors, and ventilation techniques, such as 1-lung ventilation and lung-protective strategies to decrease the risks of reperfusion injury, barotrauma, and re-expansion pulmonary edema. Intraoperative transesophageal echocardiography, cardiopulmonary bypass, and inhaled nitric oxide can also be important tools for the anesthesiologist to optimize patient care during this challenging procedure.

Histochemical Alterations in One Lung Ventilation

BACKGROUND

One lung ventilation is a commonly performed surgical procedure. Although there have been several reports showing that one-lung ventilation can cause pathophysiological alterations such as pulmonary hypoxic vasoconstriction and intrapulmonary shunting, there have been virtually no reports on the effects of one-lung ventilation on lung histology.

MATERIALS AND METHODS

Yorkshire pigs (11-17 kg) were anesthetized, a tracheotomy performed and a tracheal tube inserted. The chest was opened and one lung ventilation (OLV), was induced by clamping of the right main bronchus. OLV was continued for 60 min before the clamp was removed and two lung ventilation (TLV) started. TLV was continued for 30 to 60 min. Blood and lung biopsies were taken immediately before OLV, 30 min and 60 min of OLV and after restoration of TLV.

RESULTS

Histological analyses revealed that the non-ventilated lung was totally collapsed during OLV. On reventilation, there was clear evidence of vascular congestion and alveolar wall thickening at 30 min after TLV. At 60 min of TLV, there was still vascular congestion. Serum nitrite levels (as an index of nitric oxide production) showed steady decline over the course of the experimental period, reaching a significantly low level on reventilation (compared with baseline levels before OLV). Lung MPO activity (marker of neutrophil sequestration) and serum TNFalpha levels were not raised during the entire experimental period.

CONCLUSIONS

These results suggest that there was lung vascular injury after OLV, which was associated with reduced levels of nitric oxide production and not associated with an inflammatory response.

Clinical review: Independent lung ventilation in critical care

Independent lung ventilation (ILV) can be classified into anatomical and physiological lung separation. It requires either endobronchial blockade or double-lumen endotracheal tube intubation. Endobronchial blockade or selective double-lumen tube ventilation may necessitate temporary one lung ventilation. Anatomical lung separation isolates a diseased lung from contaminating the non-diseased lung. Physiological lung separation ventilates each lung as an independent unit. There are some clear indications for ILV as a primary intervention and as a rescue ventilator strategy in both anatomical and physiological lung separation. Potential pitfalls are related to establishing and maintaining lung isolation. Nevertheless, ILV can be used in the intensive care setting safely with a good understanding of its limitations and potential complications.

Low- vs high-dose almitrine combined with nitric oxide to prevent hypoxia during open-chest one-lung ventilation

BACKGROUND

Almitrine combined with inhaled nitric oxide (NO) can prevent hypoxia during one-lung ventilation (OLV). The optimal dose of almitrine that would provide therapeutic advantage with few side-effects during open-chest OLV has not been established.

METHODS

Forty-two patients undergoing thoracotomy were randomly allocated to three groups: placebo, almitrine 4 microg kg(-1) min(-1) and inhaled NO 10 p.p.m. (ALM4+NO), and almitrine 16 microg kg(-1) min(-1) and inhaled NO 10 p.p.m. (ALM16+NO). Gas exchange, haemodynamic and respiratory variables and plasma concentrations of almitrine and lactate were monitored. Measurements were obtained with the patient awake (baseline), after induction of anaesthesia with two-lung ventilation (control 2LV), 20 min after treatment (2LV+T), and then at 10, 20 and 30 min of OLV (OLV10', OLV20' and OLV30') with FI(O2)1.

RESULTS

In the placebo group, OLV impaired Pa(O2) and increased pulmonary shunt [16 (SD 7) kPa and 42 (10)% respectively]. These improved with ALM4+NO [26 (10) kPa and 31 (7)%; P<0.001]. ALM16+NO further improved PaO2) to 36 (13) kPa (P<0.0001) but gave no improvement in the shunt. Mean pulmonary artery pressure was similar in the placebo and ALM4+NO groups [20 (4) vs 23 (5) mm Hg], whereas it was increased in the ALM16+NO group to 28 (8) mm Hg (P<0.01). Plasma concentrations of almitrine and lactate were unaltered by the treatments.

CONCLUSIONS

Low-dose almitrine (4 microg kg(-1) min(-1)) together with inhaled NO significantly improves oxygenation during open-chest OLV, without modifying pulmonary haemodynamics. An increased dose of almitrine (16 microg kg(-1) min(-1)) with inhaled NO further improves arterial oxygenation, but also increases mean pulmonary artery pressure.

Inhaled nitric oxide therapy in adults: European expert recommendations

BACKGROUND

Inhaled nitric oxide (iNO) has been used for treatment of acute respiratory failure and pulmonary hypertension since 1991 in adult patients in the perioperative setting and in critical care.

METHODS

This contribution assesses evidence for the use of iNO in this population as presented to a expert group jointly organised by the European Society of Intensive Care Medicine and the European Association of Cardiothoracic Anaesthesiologists.

CONCLUSIONS

Expert recommendations on the use of iNO in adults were agreed on following presentation of the evidence at the expert meeting held in June 2004.

Pathophysiology and management of one-lung ventilation

The ability to manage OLV effectively in patients with significant pulmonary disease is increasing. Knowledge of pulmonary ventilation and perfusion physiology, improvements in the ability to prevent and treat hypoxia, and a thorough grasp of traditional and novel ventilatory techniques may promote improved perioperative outcomes.

Preload indexes in thoracic anesthesia

PURPOSE OF THE REVIEW

An adequate cardiac preload is essential in the treatment of critically ill patients. During anesthesia for thoracic surgery, volume and vasoactive therapy to optimize cardiac output, oxygen delivery (tissue perfusion) and to avoid pulmonary edema is a central therapeutic aspect. Cardiac preload has been estimated with different techniques in clinical practice, even though studies performed on thoracic anesthesia are lacking.

RECENT FINDINGS

We analyze the conventional pulmonary artery catheter, transesophageal echocardiography and the transpulmonary indicator dilution technique as preload monitoring devices with their indications and limits in thoracic anesthesia.

SUMMARY

The pulmonary artery catheter is confirmed as a fundamental device particularly in patients with pulmonary hypertension. For transesophageal echocardiography monitoring, the dependency on operator experience, the low repeatability and the high costs limit its interpretation and diffusion in clinical practice. During lung transplantation, Swan Ganz catheter monitoring is recommended. The optimization of fluid balance and vasoactive drug administration based on volumetric monitoring makes the transpulmonary indicator dilution technique a new option as an effective monitoring system during anesthesia for thoracic surgery when intravascular volume management is a primary objective.

Modulating the pulmonary circulation: an update

PURPOSE OF REVIEW

Disorders of the pulmonary circulation might develop as a primary disease process of the pulmonary vascular bed or, more often, as the acute or chronic consequence of pulmonary or cardiac pathologies. For the anaesthesiologist and intensivist it is particularly interesting to gain insight into the regulation of the pulmonary circulation since pulmonary hypertension and concomitant right heart failure contribute to high perioperative mortality rates in patients at risk, especially after cardiac surgery. Therefore, modulation of the pulmonary circulation may be a life-saving therapy in patients suffering from acute or chronic pulmonary circulatory disorders. Furthermore, routinely performed intra-operative interventions such as the use of volatile anaesthetics or cardiopulmonary bypass systems may have relevant side effects on the pulmonary circulation.

RECENT FINDINGS

This review focuses on new insights into the modulation of pulmonary circulation during general anaesthesia with volatile anaesthetics and anaesthesiological management during cardiopulmonary surgery. Recent publications in the field of cardiopulmonary bypass surgery, one-lung ventilation and heart and lung transplantation are discussed. Furthermore, the role of conventional and experimental therapeutic strategies to modulate pulmonary circulation in intensive care medicine is reviewed.

SUMMARY

Despite the performance of a large number of clinical and experimental studies, the pathophysiology of pulmonary circulatory disorders is not completely understood. Therefore, any new therapy has to be carefully evaluated as a therapeutic option. Several formerly experimental therapeutic interventions such as inhaled vasodilators, however, appear to have found their way into clinical practice for selected indications.

Anaesthesia in patients with cystic fibrosis

Cystic fibrosis is an autosomal-recessive disorder. In 1989 the gene mutation that causes cystic fibrosis was localized on the long arm of chromosome 7. Cystic fibrosis occurs in 1/2000 children and the majority now reach adulthood. In view of numerous clinical manifestations of cystic fibrosis, these patients frequently require surgery. Cystic fibrosis is therefore of increasing interest to anaesthesiologists. Preoperative assessment is reviewed. Pre-, intra- and postoperative care must be directed toward optimal clearance of viscous respiratory secretions, and should minimize the risk of postoperative respiratory complications. All procedures should be planned but it is very important to prepare patients for surgery, with daily physiotherapy, administration of therapeutic agents using aerosols, management of nutrition and pancreatic enzymes, and administration of vitamins and antibiotics if indicated. Currently, anaesthesia can safely be carried out in cystic fibrosis patients undergoing minor surgery, with very low incidence of postoperative respiratory complications. Finally, organ transplantation, and in particular lung transplantation, with all its attendant anaesthesiological implications, has improved the outcome for many patients with cystic fibrosis.