- Please check and comment entries here.
Intraoperative Mechanical Ventilation
Mechanical ventilation (MV) is still necessary in many surgical procedures; nonetheless, intraoperative MV is not free from harmful effects. Protective ventilation strategies, which include the combination of low tidal volume and adequate positive end expiratory pressure (PEEP) levels, are usually adopted to minimize the ventilation-induced lung injury and to avoid post-operative pulmonary complications (PPCs). Even so, volutrauma and atelectrauma may co-exist at different levels of tidal volume and PEEP, and therefore, the physiological response to the MV settings should be monitored in each patient.
Mechanical ventilation (MV) is still necessary in many surgical procedures to provide gas exchanges during general anesthesia (GA) . The concept of ventilator-induced lung injury has long been known; indeed, inadequate MV settings can lead to both atelectasis and lung overdistention . Most studies on protective mechanical ventilation are focused on acute respiratory distress syndrome (ARDS) patients, where low tidal volume (VT) and an adequate positive end expiratory pressure (PEEP) are useful to minimize the dangerous effect of MV .
As described in ARDS patients, also during GA, higher tidal volume produces inflammatory reaction and pulmonary damages; as a result, many studies have found that the use of higher VT in patients undergoing GA increases morbidity and mortality . On the opposite side, the use of intraoperative low tidal volume can reduce postoperative pulmonary complications (PPCs) .
In the last decades, research focused on development of protective ventilation strategies to prevent PPCs; indeed, MV should provide gas exchanges while minimizing lung stress and strain . From the clinical point of view, this purpose can be reached by coupling a deep physiological understanding of the different ventilatory parameters and a continuous monitoring of their effects on the lungs. Several randomized clinical trials (RCTs) failed to find a specific ventilation strategy able to reduce PPCs . Patients’ heterogeneity may be one of the main confounding factors leading to negative RCT.
This narrative review aims to provide a current knowledge regarding how to set mechanical ventilation in different type of surgery (i.e., open abdominal surgery, laparoscopy and thoracic surgery) in order to reduce the risk of PPCs.
2. Mechanical Power
Due to the complexity of the interaction between the many respiratory variables, many efforts have been made to achieve a comprehensive analysis of the energy given by the ventilator to the patients. Mechanical power (MP) is a summary variable including all the components which can possibly cause VILI. where RR is respiratory rate, VT is tidal volume, ELrs is respiratory system elastance, and Raw is airway resistance . Higher values of MP have been associated lung injury; even so, studies performed in healthy lungs during general anesthesia are mostly conducted in animals .
The MP Formula can give to the anesthesiologist the ability to balance the effects of each respiratory parameter on the lungs. For example, the effect of tidal volume, which is squared in the Formula, is predominant. Further, it appears that the effect of PEEP is dichotomic: it increases the MP but also has the ability to reduce it through a reduction in ELrs. Finally, the MP Formula highlights that the respiratory rate, usually neglected when discussing the genesis of VILI, has a linear correlation with the amount of the energy delivered to the lungs.
Despite the robust physiological bases of MP, some limits should be considered. First, a validation of MP Formula in a large surgical population is still lacking, with only a small study performed in thoracic surgery . Second, due to the complexity of the Formula, easier equations are being tested to allow an easier bedside calculation of MP . Finally, despite low MP values, local damage is still possible in case of inhomogeneous ventilation with atelectasis and hyperinflation present at the same time.
3. Expiratory Flow Limitation
Expiratory flow limitation (EFL) is a pathological condition characterized by a sharp reduction of expiratory flow associated with increased risk of PPCs in patients undergoing general anesthesia . In mechanically ventilated patients, EFL is usually defined by the lack of increasing in the expiratory flow when PEEP is decreased, also called PEEP test . During anesthesia, FRC values may shift below the closing capacity, causing collapsible small airways and, consequently, the “opening-closing” phenomena.
This can contribute to PPCs through different pathways. Such cyclic closure results in a reduction on expiratory flow together with a physical stress to the airway wall, which promote inflammation . Moreover, EFL can cause an enhance of regional overdistention , which is difficulty detectable during GA. Furthermore, the occurrence of EFL during mechanical ventilation may impair the efficacy of postoperative cough and the clearance of secretions in smaller airways .
Given the relationship between occurrence of EFL and PPCs, a routinely assessment of EFL is suggested; this is particularly relevant because intraoperative EFL is often at least partially reversible. In a study involving ARDS patients, extrinsic PEEP was able to reduce intrinsic PEEP in EFL patients . Accordingly, an observational study demonstrated a “paradoxical” response to PEEP in EFL patients, i.e., the decrease of hyperinflation when PEEP was increased . This is probably due to the fact that application of PEEP may stabilize small airways and consequently improve lung emptying.
4. From Protective to Personalized: The Future of Intraoperative Mechanical Ventilation
The continuous growing of monitoring tools available at bedside is challenging the actual concept of protective ventilation. EIT can give additional information to those given by respiratory mechanics. Respiratory mechanics can better asses the dynamic stress, whether EIT may help to optimize lung recruitment and homogeneity of ventilation . Moreover, data regarding regional air trapping are gaining importance in EIT evaluation and may represent an important adding to intraoperative MV knowledge .
The same concept (i.e., coupling monitoring ability with clinical intervention) can be extended to the usefulness of intraoperative lung ultrasound assessment. Perioperative lung ultrasound has been used to dynamically detect the development of intraoperative atelectasis  or alveolar consolidation  as well as postoperative diaphragm dysfunction . Given that lung ultrasound can assess PEEP-induced lung recruitment , its application could help to identify which patients could benefit from higher PEEP or recruiting maneuvers.
As resumed in this review, setting an adequate “personalized” MV able to optimize the lung function is far from being simple. Identifying the optimal MV strategy when considering the whole organism, and not only the lung, is even more challenging. Mechanical ventilation can affect the hemodynamic status of the patients in several ways, particularly with PEEP titration . Briefly, the same PEEP value able to optimize lung function can impair cardiac output while resulting in lower arterial oxygen delivery (DO2) despite higher alveolar oxygen content; only few studies investigated the effects of different PEEP values on lung protection and DO2, showing that in a consistent percentage of patients, incremental PEEP appears to protect alveoli but resulted in lower DO2.
The different systemic consequences of PEEP underline that the ventilator-induced lung injury is only one of the putative adverse effect of MV; recently, it has been shown that two MV strategies with same lung-protection ability can affect in different ways the cardiovascular system . How much is the acceptable fall in DO2, and how to balance the lung and hemodynamics effects of MV, are far from being demonstrated.
Finally, it is worth underlining that the microcirculatory effects of MV are not fully explainable with changes in cardiac output. For example, PEEP application can affect renal blood flow with a non-linear relationship difficult to predict . Therefore, specific organ monitoring is recommended particularly in the high-risk setting; recently, intraoperative Doppler-determined renal resistive index (RRI) has been identified as a risk factor for postoperative acute kidney injury in patients undergoing cardiopulmonary bypass .
The entry is from 10.3390/jcm10122656
- Severgnini, P.; Selmo, G.; Lanza, C.; Chiesa, A.; Frigerio, A.; Bacuzzi, A.; Dionigi, G.; Novario, R.; Gregoretti, C.; de Abreu, M.G.; et al. Protective Mechanical Ventilation during General Anesthesia for Open Abdominal Surgery Improves Postoperative Pulmonary Function. Anesthesiology 2013, 118, 1307–1321.
- Chiumello, D.; Coppola, S.; Froio, S. Toward Lung Protective Ventilation during General Anesthesia: A New Challenge. Rev. Esp. Anestesiol. Reanim. 2013, 60, 549–551.
- Pereira, S.M.; Tucci, M.R.; Morais, C.C.A.; Simões, C.M.; Tonelotto, B.F.F.; Pompeo, M.S.; Kay, F.U.; Pelosi, P.; Vieira, J.E.; Amato, M.B.P. Individual Positive End-Expiratory Pressure Settings Optimize Intraoperative Mechanical Ventilation and Reduce Postoperative Atelectasis. Anesthesiology 2018, 129, 1070–1081.
- Hedenstierna, G.; Strandberg, A.; Brismar, B.; Lundquist, H.; Svensson, L.; Tokics, L. Functional Residual Capacity, Thoracoabdominal Dimensions, and Central Blood Volume during General Anesthesia with Muscle Paralysis and Mechanical Ventilation. Anesthesiology 1985, 62, 247–254.
- Fernández-Pérez, E.R.; Sprung, J.; Afessa, B.; Warner, D.O.; Vachon, C.M.; Schroeder, D.R.; Brown, D.R.; Hubmayr, R.D.; Gajic, O. Intraoperative Ventilator Settings and Acute Lung Injury after Elective Surgery: A Nested Case Control Study. Thorax 2009, 64, 121–127.
- Acute Respiratory Distress Syndrome Network; Brower, R.G.; Matthay, M.A.; Morris, A.; Schoenfeld, D.; Thompson, B.T.; Wheeler, A. Ventilation with Lower Tidal Volumes as Compared with Traditional Tidal Volumes for Acute Lung Injury and the Acute Respiratory Distress Syndrome. N. Engl. J. Med. 2000, 342, 1301–1308.
- Futier, E.; Constantin, J.-M.; Paugam-Burtz, C.; Pascal, J.; Eurin, M.; Neuschwander, A.; Marret, E.; Beaussier, M.; Gutton, C.; Lefrant, J.-Y.; et al. A Trial of Intraoperative Low-Tidal-Volume Ventilation in Abdominal Surgery. N. Engl. J. Med. 2013, 369, 428–437.
- Ladha, K.; Vidal Melo, M.F.; McLean, D.J.; Wanderer, J.P.; Grabitz, S.D.; Kurth, T.; Eikermann, M. Intraoperative Protective Mechanical Ventilation and Risk of Postoperative Respiratory Complications: Hospital Based Registry Study. BMJ 2015, 351, h3646.
- Fernandez-Bustamante, A.; Frendl, G.; Sprung, J.; Kor, D.J.; Subramaniam, B.; Martinez Ruiz, R.; Lee, J.-W.; Henderson, W.G.; Moss, A.; Mehdiratta, N.; et al. Postoperative Pulmonary Complications, Early Mortality, and Hospital Stay Following Noncardiothoracic Surgery: A Multicenter Study by the Perioperative Research Network Investigators. JAMA Surg. 2017, 152, 157.
- Lellouche, F.; Dionne, S.; Simard, S.; Bussières, J.; Dagenais, F. High Tidal Volumes in Mechanically Ventilated Patients Increase Organ Dysfunction after Cardiac Surgery. Anesthesiology 2012, 116, 1072–1082.
- Güldner, A.; Kiss, T.; Serpa Neto, A.; Hemmes, S.N.T.; Canet, J.; Spieth, P.M.; Rocco, P.R.M.; Schultz, M.J.; Pelosi, P.; Gama de Abreu, M. Intraoperative Protective Mechanical Ventilation for Prevention of Postoperative Pulmonary Complications: A Comprehensive Review of the Role of Tidal Volume, Positive End-Expiratory Pressure, and Lung Recruitment Maneuvers. Anesthesiology 2015, 123, 692–713.
- PROVE Network Investigators. High versus Low Positive End-Expiratory Pressure during General Anaesthesia for Open Abdominal Surgery (PROVHILO Trial): A Multicentre Randomised Controlled Trial. Lancet 2014, 384, 495–503.
- Bluth, T.; Serpa Neto, A.; Schultz, M.J.; Pelosi, P.; Gama de Abreu, M.; Writing Committee for the PROBESE Collaborative Group of the PROtective VEntilation Network (PROVEnet) for the Clinical Trial Network of the European Society of Anaesthesiology. Effect of Intraoperative High Positive End-Expiratory Pressure (PEEP) with Recruitment Maneuvers vs. Low PEEP on Postoperative Pulmonary Complications in Obese Patients: A Randomized Clinical Trial. JAMA 2019, 321, 2292.
- Karalapillai, D.; Weinberg, L.; Peyton, P.; Ellard, L.; Hu, R.; Pearce, B.; Tan, C.O.; Story, D.; O’Donnell, M.; Hamilton, P.; et al. Effect of Intraoperative Low Tidal Volume vs. Conventional Tidal Volume on Postoperative Pulmonary Complications in Patients Undergoing Major Surgery: A Randomized Clinical Trial. JAMA 2020, 324, 848.
- Gattinoni, L.; Tonetti, T.; Cressoni, M.; Cadringher, P.; Herrmann, P.; Moerer, O.; Protti, A.; Gotti, M.; Chiurazzi, C.; Carlesso, E.; et al. Ventilator-Related Causes of Lung Injury: The Mechanical Power. Intensive Care Med. 2016, 42, 1567–1575.
- Vassalli, F.; Pasticci, I.; Romitti, F.; Duscio, E.; Aßmann, D.J.; Grünhagen, H.; Vasques, F.; Bonifazi, M.; Busana, M.; Macrì, M.M.; et al. Does Iso-Mechanical Power Lead to Iso-Lung Damage?: An Experimental Study in a Porcine Model. Anesthesiology 2020, 132, 1126–1137.
- Maia, L.D.A.; Samary, C.S.; Oliveira, M.V.; Santos, C.L.; Huhle, R.; Capelozzi, V.L.; Morales, M.M.; Schultz, M.J.; Abreu, M.G.; Pelosi, P.; et al. Impact of Different Ventilation Strategies on Driving Pressure, Mechanical Power, and Biological Markers During Open Abdominal Surgery in Rats. Anesth. Analg. 2017, 125, 1364–1374.
- Collino, F.; Rapetti, F.; Vasques, F.; Maiolo, G.; Tonetti, T.; Romitti, F.; Niewenhuys, J.; Behnemann, T.; Camporota, L.; Hahn, G.; et al. Positive End-Expiratory Pressure and Mechanical Power. Anesthesiology 2019, 130, 119–130.
- Chiumello, D.; Formenti, P.; Bolgiaghi, L.; Mistraletti, G.; Gotti, M.; Vetrone, F.; Baisi, A.; Gattinoni, L.; Umbrello, M. Body Position Alters Mechanical Power and Respiratory Mechanics During Thoracic Surgery. Anesth. Analg. 2020, 130, 391–401.
- Chiumello, D.; Gotti, M.; Guanziroli, M.; Formenti, P.; Umbrello, M.; Pasticci, I.; Mistraletti, G.; Busana, M. Bedside Calculation of Mechanical Power during Volume- and Pressure-Controlled Mechanical Ventilation. Crit. Care 2020, 24, 417.
- Chi, Y.; He, H.; Long, Y. A Simple Method of Mechanical Power Calculation: Using Mean Airway Pressure to Replace Plateau Pressure. J. Clin. Monit. Comput. 2020, 1–9.
- Spadaro, S.; Caramori, G.; Rizzuto, C.; Mojoli, F.; Zani, G.; Ragazzi, R.; Valpiani, G.; Dalla Corte, F.; Marangoni, E.; Volta, C.A. Expiratory Flow Limitation as a Risk Factor for Pulmonary Complications After Major Abdominal Surgery. Anesth. Analg. 2017, 124, 524–530.
- Volta, C.A.; Dalla Corte, F.; Ragazzi, R.; Marangoni, E.; Fogagnolo, A.; Scaramuzzo, G.; Grieco, D.L.; Alvisi, V.; Rizzuto, C.; Spadaro, S. Expiratory Flow Limitation in Intensive Care: Prevalence and Risk Factors. Crit. Care Lond. Engl. 2019, 23, 395.
- Kilic, O.F.; Börgers, A.; Köhne, W.; Musch, M.; Kröpfl, D.; Groeben, H. Effects of Steep Trendelenburg Position for Robotic-Assisted Prostatectomies on Intra- and Extrathoracic Airways in Patients with or without Chronic Obstructive Pulmonary Disease. Br. J. Anaesth. 2015, 114, 70–76.
- Zhao, Z.; Chang, M.-Y.; Frerichs, I.; Zhang, J.-H.; Chang, H.-T.; Gow, C.-H.; Möller, K. Regional Air Trapping in Acute Exacerbation of Obstructive Lung Diseases Measured with Electrical Impedance Tomography: A Feasibility Study. Minerva Anestesiol. 2020, 86, 172–180.
- Alvisi, V.; Marangoni, E.; Zannoli, S.; Uneddu, M.; Uggento, R.; Farabegoli, L.; Ragazzi, R.; Milic-Emili, J.; Belloni, G.P.; Alvisi, R.; et al. Pulmonary Function and Expiratory Flow Limitation in Acute Cervical Spinal Cord Injury. Arch. Phys. Med. Rehabil. 2012, 93, 1950–1956.
- Junhasavasdikul, D.; Telias, I.; Grieco, D.L.; Chen, L.; Gutierrez, C.M.; Piraino, T.; Brochard, L. Expiratory Flow Limitation During Mechanical Ventilation. Chest 2018, 154, 948–962.
- Koutsoukou, A.; Bekos, B.; Sotiropoulou, C.; Koulouris, N.G.; Roussos, C.; Milic-Emili, J. Effects of Positive End-Expiratory Pressure on Gas Exchange and Expiratory Flow Limitation in Adult Respiratory Distress Syndrome. Crit. Care Med. 2002, 30, 1941–1949.
- Kondili, E.; Alexopoulou, C.; Prinianakis, G.; Xirouchaki, N.; Georgopoulos, D. Pattern of Lung Emptying and Expiratory Resistance in Mechanically Ventilated Patients with Chronic Obstructive Pulmonary Disease. Intensive Care Med. 2004, 30, 1311–1318.
- Scaramuzzo, G.; Spadaro, S.; Dalla Corte, F.; Waldmann, A.D.; Böhm, S.H.; Ragazzi, R.; Marangoni, E.; Grasselli, G.; Pesenti, A.; Volta, C.A.; et al. Personalized Positive End-Expiratory Pressure in Acute Respiratory Distress Syndrome: Comparison Between Optimal Distribution of Regional Ventilation and Positive Transpulmonary Pressure. Crit. Care Med. 2020, 48, 1148–1156.
- Monastesse, A.; Girard, F.; Massicotte, N.; Chartrand-Lefebvre, C.; Girard, M. Lung Ultrasonography for the Assessment of Perioperative Atelectasis: A Pilot Feasibility Study. Anesth. Analg. 2017, 124, 494–504.
- Hollon, M.M.; Fiza, B.; Faloye, A. Intraoperative Application of Lung Ultrasound to Diagnose Alveolar Consolidation. Anesthesiology 2019, 131, 894.
- Spadaro, S.; Grasso, S.; Dres, M.; Fogagnolo, A.; Dalla Corte, F.; Tamburini, N.; Maniscalco, P.; Cavallesco, G.; Alvisi, V.; Stripoli, T.; et al. Point of Care Ultrasound to Identify Diaphragmatic Dysfunction after Thoracic Surgery. Anesthesiology 2019, 131, 266–278.
- Bouhemad, B.; Brisson, H.; Le-Guen, M.; Arbelot, C.; Lu, Q.; Rouby, J.-J. Bedside Ultrasound Assessment of Positive End-Expiratory Pressure-Induced Lung Recruitment. Am. J. Respir. Crit. Care Med. 2011, 183, 341–347.
- Luecke, T.; Pelosi, P. Clinical Review: Positive End-Expiratory Pressure and Cardiac Output. Crit. Care Lond. Engl. 2005, 9, 607–621.
- Chikhani, M.; Das, A.; Haque, M.; Wang, W.; Bates, D.G.; Hardman, J.G. High PEEP in Acute Respiratory Distress Syndrome: Quantitative Evaluation between Improved Arterial Oxygenation and Decreased Oxygen Delivery. Br. J. Anaesth. 2016, 117, 650–658.
- Fogagnolo, A.; Grasso, S.; Dres, M.; Gesualdo, L.; Murgolo, F.; Morelli, E.; Ottaviani, I.; Marangoni, E.; Volta, C.A.; Spadaro, S. Focus on Renal Blood Flow in Mechanically Ventilated Patients with SARS-CoV-2: A Prospective Pilot Study. J. Clin. Monit. Comput. 2021, 1–7.
- Andrew, B.Y.; Andrew, E.Y.; Cherry, A.D.; Hauck, J.N.; Nicoara, A.; Pieper, C.F.; Stafford-Smith, M. Intraoperative Renal Resistive Index as an Acute Kidney Injury Biomarker: Development and Validation of an Automated Analysis Algorithm. J. Cardiothorac. Vasc. Anesth. 2018, 32, 2203–2209.