Acute lung injury in thoracic surgery. Curr Opin Anaesthesiol. 2013;26:40-46. [PMID: 23235524 DOI: 10.1097/aco.0b013e32835c4ea2]

Anesthesia and fast-track in video-assisted thoracic surgery (VATS): from evidence to practice

In thoracic surgery, the introduction of video-assisted thoracoscopic techniques has allowed the development of fast-track protocols, with shorter hospital lengths of stay and improved outcomes. The perioperative management needs to be optimized accordingly, with the goal of reducing postoperative complications and speeding recovery times. Premedication performed in the operative room should be wisely administered because often linked to late discharge from the post-anesthesia care unit (PACU). Inhalatory anesthesia, when possible, should be preferred based on protective effects on postoperative lung inflammation. Deep neuromuscular blockade should be pursued and carefully monitored, and an appropriate reversal administered before extubation. Management of one-lung ventilation (OLV) needs to be optimized to prevent not only intraoperative hypoxemia but also postoperative acute lung injury (ALI): protective ventilation strategies are therefore to be implemented. Locoregional techniques should be favored over intravenous analgesia: the thoracic epidural, the paravertebral block (PVB), the intercostal nerve block (ICNB), and the serratus anterior plane block (SAPB) are thoroughly reviewed and the most common dosages are reported. Fluid therapy needs to be administered critically, to avoid both overload and cardiovascular compromisation. All these practices are analyzed singularly with the aid of the most recent evidences aimed at the best patient care. Finally, a few notes on some of the latest trends in research are presented, such as non-intubated video-assisted thoracoscopic surgery (VATS) and intravenous lidocaine.

Enhanced Recovery in Thoracic Surgery: A Review

The main goal of enhanced recovery program after thoracic surgery is to minimize stress response, reduce postoperative pulmonary complications, and improve patient outcome, which will in addition decrease hospital stay and reduce hospital costs. As minimally invasive technique, video-assisted thoracoscopic surgery represents an important element of enhanced recovery program in thoracic surgery. Anesthetic management during preoperative, intraoperative and postoperative period is essential for the enhanced recovery. In the era of enhanced recovery protocols, non-intubated thoracoscopic procedures present a step forward. This article focuses on the key elements of the enhanced recovery program in thoracic surgery. Having reviewed recent literature, the authors highlight potential procedures and techniques that might be incorporated into the program.

Anesthesia and analgesia: how does the role of anesthetists changes in the ERAS program for VATS lobectomy

Enhanced recovery after surgery (ERAS) programs are developed to prevent factors that delay postoperative recovery as well as issues that cause complications. The development of video-assist thoracoscopic surgery (VATS) techniques favors the fast recovery after thoracic procedures. ERAS strategies are based on multidisciplinary approach in which the anesthetist plays an important role from the preoperative to the postoperative phase with several goals. After preoperative evaluation and medical optimization, the anesthetist must ensure a tailored anesthetic plan aiming to a fast recovery and adequate pain relief to reduce the response to the surgical stress. The present narrative review presents the major parts of the ERAS anesthetic approach to VATS lobectomy like short-acting drugs, protective one-lung ventilation (OLV), fluid administration and opioid-sparing multimodal analgesia.

Care of the Postoperative Pulmonary Resection Patient

Patients undergoing pulmonary resection all exhibit, to some degree, a level of pulmonary dysfunction. This is due to the physiologic stress of the procedure performed, the patient’s comorbidities, and preexisting cardiopulmonary reserve. Although prognostic factors for intensive care requirement exist, to date, there is no consensus for postoperative admission. Institutional practices vary across the country, with patients often admitted to intensive care for surveillance. Guidelines published from the American Thoracic Society in 1999 emphasize that admission to the ICU be reserved for those patients requiring care and monitoring for severe physiologic instability. Admissions following pulmonary resection are typically due to respiratory complications and are an independent predictor of mortality. The following chapter will review the indications for admission to the ICU and common issues encountered following pulmonary resection and conclude with a discussion of the management of patients undergoing pulmonary transplantation.

The effects of one-lung ventilation mode on lung function in elderly patients undergoing esophageal cancer surgery

The objective of the present study was to explore the effects of different one-lung ventilation (OLV) modes on lung function in elderly patients undergoing esophageal cancer surgery. A total of 180 consecutive elderly patients (ASA Grades I-II, with OLV indications) undergoing elective surgery were recruited in the study. Patients were randomly divided into 4 groups (n = 45). In Group A, patients received low tidal volume (VT < 8 mL/kg) + pressure controlled ventilation (PCV), low tidal volume (VT < 8 mL/kg) + volume-controlled ventilation (VCV) in Group B, high tidal volume (VT ≥ 8 mL/kg) + PCV in Group C and high tidal volume (VT ≥ 8 mL/kg) + VCV in Group D. Two-lung ventilation involved routine tidal volume (8-10 mL/kg) at a frequency of 12 to 18 times/min, and VCV mode. Clinical efficacy among 4 groups was compared. The partial pressure of end-tidal carbon dioxide (PetCO2) did not significantly differ among 4 groups (all P > .05), and the oxygenation index and SO2 in Group A were significantly higher than in the other groups (P < .05). The PetCO2, peak airway pressure (Ppeak), platform airway pressure (Pplat), and mean airway pressure (Pmean) in Group A were significantly lower than those in the other groups (all P < .05). However, airway resistance (Raw) among 4 groups did not significantly differ (all P > .05). The incidence of pulmonary infection, anastomotic fistula, ventilator-induced lung injury, lung dysfunction, difficulty weaning from mechanical ventilation, and multiple organ dysfunction in Groups A and B were lower than that in Groups C and D (all P < .05). The expression levels of IL-6, tumor necrosis factor-α, and C-reactive protein in lavage fluid in Group A were significantly lower than those in the other groups (all P < .05). OLV with low tidal volume (VT < 8 mL/kg) + PCV (5 cmH2O PEEP) improved lung function and mitigated inflammatory responses in elderly patients undergoing esophageal cancer surgery.

[Pathogenic role of leukotriene B4 in pulmonary microvascular endothelial cell hyper- permeability induced by one lung ventilation in rabbits]

OBJECTIVE

To elucidate the pathogenic role of leukotriene B4 (LTB4) in increased pulmonary microvascular endothelial cell permeability induced by one lung ventilation (OLV) in rabbits.

METHODS

Forty-eight healthy Japanese white rabbits were randomly divided into control group (group C), saline pretreatment group (group S), bestatin (a leukotriene A4 hydrolase (LTA4H) inhibitor) plus saline pretreatment group (group B), OLV group (group O), saline pretreatment plus OLV group (group SO) and bestatin plus saline pretreatment with OLV group (group BO). ELISA was used to detect LTB4 content in the lung tissues, and LTA4H and phospholipase Cεl (PLCEl) expressions were examined by Western blotting and quantitative PCR. The wet/dry weight (W/D) ratio of the lung, lung permeability index and the expressions of myosin light chain kinase (MLCK) protein and mRNA in the lung tissues were determined to evaluate the permeability of the pulmonary microvascular endothelial cells (PMVECs). The severities of lung injury were evaluated by lung histomorphological scores.

RESULTS

No significant differences were found among groups C, S and B except that LTA4H expressions was significantly lower in group B than in groups C and S (P<0.05). OLV significantly increased the expressions of LTA4H (P<0.05) and resulted in LTB4 overproduction in the lungs (P<0.05) accompanied by significantly enhanced PLCE1 expression and PMVEC permeability (P<0.05). Pretreatment with bestatin, significantly reduced the expression of LTA4H and LTB4 production (P<0.05) and down-regulated the expression of PLCE1 in the lungs of the rabbits receiving OLV (P<0.05).

CONCLUSION

Bestatin plays a protective role in OLV-induced rabbit lung injury by downregulating LTA4H to reduce the production of LTB4 in the lungs. LTB4 can increase PMVEC permeability by up-regulating PLCE1 expression in rabbits with OLV-induced lung injury.

[Relationship between cytoplasmic phospholipase A2 and nuclear factor κB in one lung ventilation-induced lung injury in rabbits]

OBJECTIVE

To elucidate the mechanisms of up regulated expression of cytoplasmic phospholipase A2 (CPLA2) induced by one lung ventilation (OLV) by investigating the interactions between nuclear factor kappaB (NF-κB) and C-PLA2.

METHODS

Forty-eight healthy Japanese white rabbits were randomized into control group, solvent treatment group (group S), NF-κB inhibitor (PDTC)/solvent treatment group ( group PS), C-PLA2 inhibitor (AACOCF3)/solvent treatment group (group AS), OLV group (group O), solvent treatment plus OLV group (SO group), NFκB inhibitor (PDTC)/solvent treatment plus OLV group (group PSO) and CPLA2 inhibitor (AACOCF3)/solvent treatment plus OLV group (group ASO). ELISA was used to detect arachidonic acid (AA) content in the lung tissues, and NFκB and CPLA2 expressions were detected by Western blotting and quantitative PCR. Lung injuries were assessed based on the lung histological score, and the polymorphonuclear leukocyte count in the bronchial alveolar lavage fluid, myeloperoxidase (MPO) content in the lung tissues, and lung wet/dry weight (W/D) raito were determined.

RESULTS

Treatment of the rabbits with the solvent did not produce any adverse effects. OLV caused obvious lung injury in the rabbits and up regulated the expressions of CPLA2 and NFκB in the lung tissues (P<0.05). In rabbits without OLV, treatment with AACOCF3 or PDTC significantly down regulated both CPLA2 and NFκB expressions without affecting the other parameters. In rabbits with OLV, treatment with AACOCF3 or PDTC obviously lowered CPLA2 and NFκB expressions and lessened the OLV-induced lung injuries.

CONCLUSION

Both C-PLA2 and NF-κB play important roles and show interactions in OLV-induced lung injury in rabbits.

The Society for Translational Medicine: clinical practice guidelines for mechanical ventilation management for patients undergoing lobectomy

Patients undergoing lobectomy are at significantly increased risk of lung injury. One-lung ventilation is the most commonly used technique to maintain ventilation and oxygenation during the operation. It is a challenge to choose an appropriate mechanical ventilation strategy to minimize the lung injury and other adverse clinical outcomes. In order to understand the available evidence, a systematic review was conducted including the following topics: (I) protective ventilation (PV); (II) mode of mechanical ventilation [e.g., volume controlled (VCV) versus pressure controlled (PCV)]; (III) use of therapeutic hypercapnia; (IV) use of alveolar recruitment (open-lung) strategy; (V) pre-and post-operative application of positive end expiratory pressure (PEEP); (VI) Inspired Oxygen concentration; (VII) Non-intubated thoracoscopic lobectomy; and (VIII) adjuvant pharmacologic options. The recommendations of class II are non-intubated thoracoscopic lobectomy may be an alternative to conventional one-lung ventilation in selected patients. The recommendations of class IIa are: (I) Therapeutic hypercapnia to maintain a partial pressure of carbon dioxide at 50-70 mmHg is reasonable for patients undergoing pulmonary lobectomy with one-lung ventilation; (II) PV with a tidal volume of 6 mL/kg and PEEP of 5 cmH₂O are reasonable methods, based on current evidence; (III) alveolar recruitment [open lung ventilation (OLV)] may be beneficial in patients undergoing lobectomy with one-lung ventilation; (IV) PCV is recommended over VCV for patients undergoing lung resection; (V) pre- and post-operative CPAP can improve short-term oxygenation in patients undergoing lobectomy with one-lung ventilation; (VI) controlled mechanical ventilation with I:E ratio of 1:1 is reasonable in patients undergoing one-lung ventilation; (VII) use of lowest inspired oxygen concentration to maintain satisfactory arterial oxygen saturation is reasonable based on physiologic principles; (VIII) Adjuvant drugs such as nebulized budesonide, intravenous sivelestat and ulinastatin are reasonable and can be used to attenuate inflammatory response.

One-lung Ventilation for Thoracic Surgery: Current Perspectives

One-lung ventilation (OLV) is an anesthesiological technique that is increasingly being used beyond thoracic surgery. This requires specific skills and knowledge about airway management, maintenance of gas exchange and prevention of acute lung injury. Sometimes maintaining adequate gas exchange and minimizing acute lung injury may be opposing processes. Parameters validated for OLV titration still have not been found, but a multimodal approach based on low tidal volume, end-expiratory pressure application and alveolar recruitment maneuvers is considered the best way to ensure protective ventilation and reduce lung damage. The purpose of this review is to analyze all these factors using the latest scientific evidence and the opinions of the most influential authors.

Pressure-controlled versus volume-controlled ventilation during one-lung ventilation for video-assisted thoracoscopic lobectomy

BACKGROUND

It is controversial as to which ventilation mode is better during one-lung ventilation (OLV). This study was designed to figure out whether there was any difference between volume controlled ventilation (VCV) and pressure controlled ventilation (PCV) on oxygenation and postoperative complications under the condition of protective ventilation (PV).

METHODS

Sixty-five patients undergoing video-assisted thoracoscopic lobectomy were randomized into two groups. Patients in group V received VCV mode during OLV while patients in group P received PCV. The tidal volume (VT) in both groups was 6 mL per predicted body weight (PBW). Positive end-expiratory pressure (PEEP) was set at the level of 5 cmH₂O in both groups. Arterial gas analysis were performed preoperatively with room air (T₀), at 15 mins (T₁) and 1 h (T₂) after OLV, at the end of OLV (T₃), 30 min after PACU admission (T₄), 24 h after surgery (post-operative day 1, POD₁) and 48 h after surgery (post-operative day 2, POD₂). Peak inspiratory airway pressure (Ppeak) and plateau airway pressure (Pplat) were recorded at T₁, T₂ and T₃. The perioperative complications were also recorded.

RESULT

Sixty-four patients completed this study. Ppeak in group V was significantly higher than that in group P (T₁ 22.3±2.9 vs. 18.7±2.1 cmH₂O; T₂ 22.2±2.8 vs. 18.7±2.6 cmH₂O). There were no differences with Pplat and intraoperative oxygenation index (T₁ 203.3±109.7 vs. 198.1±93.4; T₂ 216.8±79.1 vs. 232.1±101.4). The postoperative oxygenation index (T₄ 525.0±160.9 vs. 520.7±127.1, post-operative day 1 (POD₁) 452.1±161.3 vs. 446.1±109.1; post-operative day 2 (POD₂) 403.8±93.4 vs. 396.7±92.8) and postoperative complications were also comparable between these two groups.

CONCLUSIONS

When they were utilized during OLV, PCV and VCV had the same performance on the intraoperative oxygenation and postoperative complications under the condition of PV.

Oxygenation, inflammatory response and lung injury during one lung ventilation in rabbits using inspired oxygen fraction of 0.6 vs. 1.0

Maintaining adequate oxygenation during one-lung ventilation (OLV) requires high inspired oxygen fraction (FiO₂). However, high FiO₂ also causes inflammatory response and lung injury. Therefore, it remains a great interest to clinicians and scientists to optimize the care of patients undergoing OLV. The aim of this study was to determine and compare oxygenation, inflammatory response and lung injury during OLV in rabbits using FiO₂ of 0.6 vs. 1.0. After 30 minutes of two-lung ventilation (TLV) as baseline, 30 rabbits were randomly assigned to three groups receiving mechanical ventilation for 3 hours: the sham group, receiving TLV with 0.6 FiO₂; the 1.0 FiO₂ group, receiving OLV with 1.0 FiO₂; the 0.6 FiO₂ group, receiving OLV with 0.6 FiO₂. Pulse oximetry was continuously monitored and arterial blood gas analysis was intermittently conducted. Histopathologic study of lung tissues was performed and inflammatory cytokines and the mRNA and protein of nuclear factor kappa B (NF-κB) p65 were determined. Three of the 10 rabbits in the 0.6 FiO₂ group suffered hypoxemia, defined by pulse oximetric saturation (SpO₂) less than 90%. Partial pressure of oxygen (PaO₂), acute lung injury (ALI) score, myeloperoxidase (MPO), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), mRNA and protein of NF-κB p65 were lower in the 0.6 FiO₂ group than in the 1.0 FiO₂ group. In conclusion, during OLV, if FiO₂ of 0.6 can be tolerated, lung injury associated with high FiO₂ can be minimized. Further study is needed to validate this finding in human subjects.

Fast track in thoracic surgery and anaesthesia: update of concepts

PURPOSE OF REVIEW

Update of key elements on enhanced recovery after thoracic anaesthesia and surgery.

RECENT FINDINGS

Pathways to enhance recovery after thoracic surgery ('fast-track') aim to improve response to lung surgery, reduction of postoperative pulmonary complications, and restore patient's vital function. Uncomplicated recovery after lung surgery reduces morbidity, hospital stay, and costs. Video-assisted thoracoscopic surgery is a major part of enhanced recovery minimizing tissue injury and stress response. Maintaining patient's physiology throughout perioperative processes by optimized anaesthesiological management and effective pain control present a crucial role in improving outcome.

SUMMARY

The concept of enhanced recovery ('fast-track') after thoracic surgery and anaesthesia was developed in recent years making allowance to the increased number of video-assisted parenchymal lung resections in managing primary lung cancer. Current studies promote the benefit in thoracic surgical patients, if an established departmental protocol-based algorithm is implemented.

Intraoperative mechanical ventilation strategies in patients undergoing one-lung ventilation: a meta-analysis

BACKGROUND

Postoperative pulmonary complications (PPCs), which are not uncommon in one-lung ventilation, are among the main causes of postoperative death after lung surgery. Intra-operative ventilation strategies can influence the incidence of PPCs. High tidal volume (V T) and increased airway pressure may lead to lung injury, while pressure-controlled ventilation and lung-protective strategies with low V T may have protective effects against lung injury. In this meta-analysis, we aim to investigate the effects of different ventilation strategies, including pressure-controlled ventilation (PCV), volume-controlled ventilation (VCV), protective ventilation (PV) and conventional ventilation (CV), on PPCs in patients undergoing one-lung ventilation. We hypothesize that both PV with low V T and PCV have protective effects against PPCs in one-lung ventilation.

METHODS

A systematic search (PubMed, EMBASE, the Cochrane Library, and Ovid MEDLINE; in May 2015) was performed for randomized trials comparing PCV with VCV or comparing PV with CV in one-lung ventilation. Methodological quality was evaluated using the Cochrane tool for risk. The primary outcome was the incidence of PPCs. The secondary outcomes included the length of hospital stay, intraoperative plateau airway pressure (Pplateau), oxygen index (PaO2/FiO2) and mean arterial pressure (MAP).

RESULTS

In this meta-analysis, 11 studies (436 patients) comparing PCV with VCV and 11 studies (657 patients) comparing PV with CV were included. Compared to CV, PV decreased the incidence of PPCs (OR 0.29; 95 % CI 0.15-0.57; P < 0.01) and intraoperative Pplateau (MD -3.75; 95 % CI -5.74 to -1.76; P < 0.01) but had no significant influence on the length of hospital stay or MAP. Compared to VCV, PCV decreased intraoperative Pplateau (MD -1.46; 95 % CI -2.54 to -0.34; P = 0.01) but had no significant influence on PPCs, PaO2/FiO2 or MAP.

CONCLUSIONS

PV with low V T was associated with the reduced incidence of PPCs compared to CV. However, PCV and VCV had similar effects on the incidence of PPCs.

Efficacy of a Low-Tidal Volume Ventilation Strategy to Prevent Reperfusion Lung Injury after Pulmonary Thromboendarterectomy

RATIONALE

Reperfusion lung injury is a postoperative complication of pulmonary thromboendarterectomy that can significantly affect morbidity and mortality. Studies in other postoperative patient populations have demonstrated a reduction in acute lung injury with the use of a low-tidal volume (Vt) ventilation strategy. Whether this approach benefits patients undergoing thromboendarterectomy is unknown.

OBJECTIVES

We sought to determine if low-Vt ventilation reduces reperfusion lung injury in patients with chronic thromboembolic pulmonary hypertension undergoing thromboendarterectomy.

METHODS

Patients undergoing thromboendarterectomy at one center were randomized to receive either low (6 ml/kg predicted body weight) or usual care Vts (10 ml/kg) from the initiation of mechanical ventilation in the operating room through Postoperative Day 3. The primary endpoint was the onset of reperfusion lung injury. Secondary outcomes included severity of hypoxemia, days on mechanical ventilation, and intensive care unit and hospital lengths of stay.

MEASUREMENTS AND MAIN RESULTS

A total of 128 patients were enrolled and included in the analysis; 63 were randomized to the low-Vt group and 65 were randomized to the usual care group. There was no statistically significant difference in the incidence of reperfusion lung injury between groups (32%, n=20 in the low-Vt group vs. 23%, n=15 in the usual care group; P=0.367). Although differences were noted in plateau pressures (17.9 cm H2O vs. 20.1 cm H2O, P<0.001) and peak inspiratory pressures (20.4 cm H2O vs. 23.0 cm H2O, P<0.001) between the low-Vt and usual care groups, respectively, mean airway pressures, PaO2/FiO2, days on mechanical ventilation, and ICU and hospital lengths of stay were all similar between groups.

CONCLUSIONS

In patients with chronic thromboembolic pulmonary hypertension undergoing pulmonary thromboendarterectomy, intra- and postoperative ventilation using low Vts (6 mg/kg) compared with usual care Vts (10 mg/kg) does not reduce the incidence of reperfusion lung injury or improve clinical outcomes. Clinical trial registered with www.clinicaltrials.gov (NCT00747045).

A novel method for right one-lung ventilation modeling in rabbits

There is no standard method by which to establish a right one-lung ventilation (OLV) model in rabbits. In the present study, a novel method is proposed to compare with two other methods. After 0.5 h of baseline two-lung ventilation (TLV), 40 rabbits were randomly divided into sham group (TLV for 3 h as a contrast) and three right-OLV groups (right OLV for 3 h with different methods): Deep intubation group, clamp group and blocker group (deeply intubate the self-made bronchial blocker into the left main bronchus, the novel method). These three methods were compared using a number of variables: Circulation by heart rate (HR), mean arterial pressure (MAP); oxygenation by arterial blood gas analysis; airway pressure; lung injury by histopathology; and time, blood loss, success rate of modeling. Following OLV, compared with the sham group, arterial partial pressure of oxygen and arterial hemoglobin oxygen saturation decreased, peak pressure increased and lung injury scores were higher in three OLV groups at 3 h of OLV. All these indexes showed no differences between the three OLV groups. During right-OLV modeling, less time was spent in the blocker group (6±2 min), compared with the other two OLV groups (13±4 min in deep intubation group, P<0.05; 33±9 min in clamp group, P<0.001); more blood loss was observed in clamp group (11.7±2.8 ml), compared with the other two OLV groups (2.3±0.5 ml in deep intubation group, P<0.001; 2.1±0.6 ml in blocker group, P<0.001). The first-time and final success rate of modeling showed no differences among the three OLV groups. Deep intubation of the self-made bronchial blocker into the left main bronchus is an easy, effective and reliable method to establish a right-OLV model in rabbits.

One-Lung Ventilation with Additional Ipsilateral Ventilation of Low Tidal Volume and High Frequency in Lung Lobectomy

BACKGROUND To investigate the protective effects of additional ipsilateral ventilation of low tidal volume and high frequency on lung functions in the patients receiving lobectomy. MATERIAL AND METHODS Sixty patients receiving lung lobectomy were randomized into the conventional one-lung ventilation (CV) group (n=30) and the ipsilateral low tidal volume high frequency ventilation (LV) group (n=30). In the CV group, patients received only contralateral OLV. In the LV group, patients received contralateral ventilation and additional ipsilateral ventilation of low tidal volume of 1-2 ml/kg and high frequency of 40 times/min. Normal lung tissues were biopsied for the analysis of lung injury. Lung injury was scored by evaluating interstitial edema, alveolar edema, neutrophil infiltration, and alveolar congestion. RESULTS At 30 min and 60 min after the initiation of one-lung ventilation and after surgery, patients in the LV group showed significantly higher ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen than those in the CV group (P<0.001). Lung injury was significantly less severe (2.7±0.7) in the LV group than in the CV group (3.1±0.7) (P=0.006). CONCLUSIONS Additional ipsilateral ventilation of low tidal volume and high frequency can decrease the risk of hypoxemia and alleviate lung injury in patients receiving lobectomy.

Adrenaline aggravates lung injury caused by liver ischemia-reperfusion and high-tidal-volume ventilation in rats

BACKGROUND

We often administer adrenaline to improve hypotension of patients undergoing systemic inflammation that is not treated with volume resuscitation. The effects of adrenaline on injured lungs during shock status have not been elucidated. We previously demonstrated that hepatic ischemia-reperfusion followed by high-tidal-volume ventilation-induced systemic inflammation, hypotension, and lung injury in rats. Using this animal model, we investigated the effects of adrenaline on lung injury and hemodynamics.

METHODS

Anesthetized rats were ventilated and underwent hepatic inflow interruption for 15 min twice. After the second liver ischemia-reperfusion, the tidal volume was increased to 24 ml · kg(-1) body weight from 6 ml · kg(-1), and 12 rats in each group were observed for 360 min after reperfusion with or without continuous intravenous adrenaline administration. Extra fluid was administered according to the decline in the arterial blood pressure.

RESULTS

Adrenaline administration significantly reduced the volume of intravenous resuscitation fluid. The wet-to-dry weight ratio of the lungs was higher (7.53 ± 0.37 vs. 4.63 ± 0.35, P < 0.001), the partial oxygen pressure in arterial blood was lower (213 ± 48 vs. 411 ± 33, P = 0.004), and the tumor necrosis factor-α concentration in bronchoalveolar lavage (BAL) fluid was higher (10(2.64) ± 10(0.22) vs. 10(1.91) ± 10(0.27), P = 0.015), with adrenaline. Histopathological examinations revealed marked exudation in the alveolar spaces in rats receiving adrenaline.

CONCLUSIONS

Continuous administration of adrenaline partially prevented a rapid decline in blood pressure but deteriorated lung injury in a rat model of liver ischemia-reperfusion with high-tidal-volume ventilation. A possibility that adrenaline administration aggravate ventilator-induced lung injury during systemic inflammation should be considered.

Lung Injury After One-Lung Ventilation: A Review of the Pathophysiologic Mechanisms Affecting the Ventilated and the Collapsed Lung

Lung injury is the leading cause of death after thoracic surgery. Initially recognized after pneumonectomy, it has since been described after any period of 1-lung ventilation (OLV), even in the absence of lung resection. Overhydration and high tidal volumes were thought to be responsible at various points; however, it is now recognized that the pathophysiology is more complex and multifactorial. All causative mechanisms known to trigger ventilator-induced lung injury have been described in the OLV setting. The ventilated lung is exposed to high strain secondary to large, nonphysiologic tidal volumes and loss of the normal functional residual capacity. In addition, the ventilated lung experiences oxidative stress, as well as capillary shear stress because of hyperperfusion. Surgical manipulation and/or resection of the collapsed lung may induce lung injury. Re-expansion of the collapsed lung at the conclusion of OLV invariably induces duration-dependent, ischemia-reperfusion injury. Inflammatory cytokines are released in response to localized injury and may promote local and contralateral lung injury. Protective ventilation and volatile anesthesia lessen the degree of injury; however, increases in biochemical and histologic markers of lung injury appear unavoidable. The endothelial glycocalyx may represent a common pathway for lung injury creation during OLV, because it is damaged by most of the recognized lung injurious mechanisms. Experimental therapies to stabilize the endothelial glycocalyx may afford the ability to reduce lung injury in the future. In the interim, protective ventilation with tidal volumes of 4 to 5 mL/kg predicted body weight, positive end-expiratory pressure of 5 to 10 cm H2O, and routine lung recruitment should be used during OLV in an attempt to minimize harmful lung stress and strain. Additional strategies to reduce lung injury include routine volatile anesthesia and efforts to minimize OLV duration and hyperoxia.

Addressing the Global Burden of Trauma in Major Surgery

Despite a technically perfect procedure, surgical stress can determine the success or failure of an operation. Surgical trauma is often referred to as the "neglected step-child" of global health in terms of patient numbers, mortality, morbidity, and costs. A staggering 234 million major surgeries are performed every year, and depending upon country and institution, up to 4% of patients will die before leaving hospital, up to 15% will have serious post-operative morbidity, and 5-15% will be readmitted within 30 days. These percentages equate to around 1000 deaths and 4000 major complications every hour, and it has been estimated that 50% may be preventable. New frontline drugs are urgently required to make major surgery safer for the patient and more predictable for the surgeon. We review the basic physiology of the stress response from neuroendocrine to genomic systems, and discuss the paucity of clinical data supporting the use of statins, beta-adrenergic blockers and calcium-channel blockers. Since cardiac-related complications are the most common, particularly in the elderly, a key strategy would be to improve ventricular-arterial coupling to safeguard the endothelium and maintain tissue oxygenation. Reduced O2 supply is associated with glycocalyx shedding, decreased endothelial barrier function, fluid leakage, inflammation, and coagulopathy. A healthy endothelium may prevent these "secondary hit" complications, including possibly immunosuppression. Thus, the four pillars of whole body resynchronization during surgical trauma, and targets for new therapies, are: (1) the CNS, (2) the heart, (3) arterial supply and venous return functions, and (4) the endothelium. This is termed the Central-Cardio-Vascular-Endothelium (CCVE) coupling hypothesis. Since similar sterile injury cascades exist in critical illness, accidental trauma, hemorrhage, cardiac arrest, infection and burns, new drugs that improve CCVE coupling may find wide utility in civilian and military medicine.

Thoracic anesthesia in the elderly

PURPOSE OF REVIEW

The mean age of patients presenting for thoracic surgery is rising steadily, associated with an increased demand for thoracic surgical treatments by geriatric patients. With increasing age, physiologic changes and comorbidities have to be considered. Thoracic anesthesia for elderly patients requires greater specific knowledge.

RECENT FINDINGS

Respiratory mechanics change progressively during aging, and the pharmacology of different drugs is also altered with increasing age. This has implications for the preoperative, intraoperative and postoperative management of elderly patients scheduled for thoracic surgery. Special focus has to be placed on preoperative evaluation, the ventilation regime and general intraoperative management. Effective postoperative pain treatment after geriatric thoracic surgery requires careful pain assessment and drug titration.

SUMMARY

Considering key points of physiology and pharmacology can help to provide best possible care for the increasing number of elderly patients in thoracic surgery. Management of geriatric patients in thoracic surgery offer opportunities for anaesthetic interventions including protective ventilation, use of different anesthetics, anaesthesia monitoring, fluid management and pain therapy.

Step-by-step clinical management of one-lung ventilation: continuing professional development

PURPOSE

The purpose of this Continuing Professional Development Module is to review the issues pertinent to one-lung ventilation (OLV) and to propose a management strategy for ventilation before, during, and after lung isolation.

PRINCIPAL FINDINGS

The need for optimal lung isolation has increased with the advent of video-assisted thoracoscopic surgery, as surgical exposure is critical for successful surgery. Continuous positive airway pressure applied to the operative lung or intermittent two-lung ventilation should therefore be avoided if possible. Optimal management of OLV should provide adequate oxygenation and also prevent acute lung injury (ALI), the leading cause of death following lung resection. Research conducted in the last decade suggests implementing a protective ventilation strategy during OLV that consists of small tidal volumes based on ideal body weight, routine use of positive end-expiratory pressure, low inspired oxygen fraction, with low peak and plateau airway pressures. High respiratory rates to compensate for low tidal volumes may predispose to significant air trapping during OLV, so permissive hypercapnea is routinely employed. The management of OLV extends into the period of two-lung ventilation, as the period prior to OLV impacts lung collapse, and both the time before and after OLV influence the extent of ALI. Lung re-expansion at the conclusion of OLV is an important component of ensuring adequate ventilation and oxygenation postoperatively but may be harmful to the lung.

CONCLUSIONS

Optimal perioperative care of the thoracic patient includes a protective ventilation strategy from intubation to extubation and into the immediate postoperative period. Anesthetic goals include the prevention of perioperative hypoxemia and postoperative ALI.

Lung preconditioning in anesthesia: Review of the literature

Lung injury can arise during or after anesthesia and can lead to a complicated postoperative course with great implications for the patient. Unfortunately, treatment of acute lung injury is at the moment mainly supportive and rates of recovery have not really improved in the recent years. In many cases, lung injury can be anticipated and preventive measures seem possible. This represents a unique challenge to the anesthesiologist, as some new opportunities to reduce the frequency and/or severity of lung injury seem now available. These chances may arise from the potency of preconditioning the lungs before the main injury, with smaller injurious insults. Although preconditioning began to be applicated first on the myocardium, experimental studies have shown potentially beneficial results also for the lungs. This review summarizes the main methods of lung preconditioning that have been tried in experimental studies in the literature and the main mechanisms that are perhaps involved. Emphasis is given in the two main methods of preconditioning that seem readily applicable in the clinical praxis, that is ischemic preconditioning, as well as preconditioning with volatile anesthetics. The few, but interesting clinical studies are also summarized and the future research points in this evolving field of anesthesia are stressed.

Lung inhomogeneity in patients with acute respiratory distress syndrome

RATIONALE

Pressures and volumes needed to induce ventilator-induced lung injury in healthy lungs are far greater than those applied in diseased lungs. A possible explanation may be the presence of local inhomogeneities acting as pressure multipliers (stress raisers).

OBJECTIVES

To quantify lung inhomogeneities in patients with acute respiratory distress syndrome (ARDS).

METHODS

Retrospective quantitative analysis of CT scan images of 148 patients with ARDS and 100 control subjects. An ideally homogeneous lung would have the same expansion in all regions; lung expansion was measured by CT scan as gas/tissue ratio and lung inhomogeneities were measured as lung regions with lower gas/tissue ratio than their neighboring lung regions. We defined as the extent of lung inhomogeneities the fraction of the lung showing an inflation ratio greater than 95th percentile of the control group (1.61).

MEASUREMENTS AND MAIN RESULTS

The extent of lung inhomogeneities increased with the severity of ARDS (14 ± 5, 18 ± 8, and 23 ± 10% of lung volume in mild, moderate, and severe ARDS; P < 0.001) and correlated with the physiologic dead space (r(2) = 0.34; P < 0.0001). The application of positive end-expiratory pressure reduced the extent of lung inhomogeneities from 18 ± 8 to 12 ± 7% (P < 0.0001) going from 5 to 45 cm H2O airway pressure. Lung inhomogeneities were greater in nonsurvivor patients than in survivor patients (20 ± 9 vs. 17 ± 7% of lung volume; P = 0.01) and were the only CT scan variable independently associated with mortality at backward logistic regression.

CONCLUSIONS

Lung inhomogeneities are associated with overall disease severity and mortality. Increasing the airway pressures decreased but did not abolish the extent of lung inhomogeneities.

The postoperative airway: unique challenges?

PURPOSE OF REVIEW

The review is focused on the challenge of managing airway and ventilation in the intraoperative and postoperative period.

RECENT FINDINGS

In past years, a lot of attention was focused on tracheal intubation in difficult airway, whereas only in recent years extubation time of difficult airway is also covering an important role. Protective ventilation strategies have been studied in acute respiratory distress syndrome and then in general anesthesia, either for thoracic or bariatric surgery, whereas in general abdominal surgery, in healthy lung, few studies are present demonstrating the effective protective role of low tidal volume, lung recruitment maneuvers (LRM) and positive end-expiratory pressure (PEEP). In the early postoperative period, the role of noninvasive ventilation is growing as it reduces postoperative pulmonary complications, postoperative length of stay and costs.

SUMMARY

The combination of planning extubation of predicted and unpredicted difficult airway, both intraoperative low tidal volume and low FiO2 with LRM and PEEP at different points of surgery and postoperative noninvasive ventilation should be considered in patients undergoing surgery to decrease the rate of postoperative pulmonary complications and major fatal complications such as brain damage and death.