The two intervention groups had similar characteristics at baseline. In the intention-to-treat analysis, the primary outcome occurred in 21 of 200 patients (10.5%) assigned to lung-protective ventilation, as compared with 55 of 200 (27.5%) assigned to nonprotective ventilation (relative risk, 0.40; 95% confidence interval [CI], 0.24 to 0.68; P = 0.001). Over the 7-day postoperative period, 10 patients (5.0%) assigned to lung-protective ventilation required noninvasive ventilation or intubation for acute respiratory failure, as compared with 34 (17.0%) assigned to nonprotective ventilation (relative risk, 0.29; 95% CI, 0.14 to 0.61; P = 0.001). The length of the hospital stay was shorter among patients receiving lung-protective ventilation than among those receiving nonprotective ventilation (mean difference, −2.45 days; 95% CI, −4.17 to −0.72; P = 0.006). CONCLUSIONS As compared with a practice of nonprotective mechanical ventilation, the use of a lung-protective ventilation strategy in intermediate-risk and high-risk patients undergoing major abdominal surgery was associated with improved clinical out comes and reduced health care utilization. (IMPROVE ClinicalTrials.gov number, NCT01282996.)

https://www.nejm.org/doi/pdf/10.1056/NEJMoa1301082

A trial of intraoperative low-tidal-volume ventilation in abdominal surgery.

Background: Current knowledge of the risk for postoperative pulmonary complications (PPCs) rests on studies that narrowly selected patients and procedures. Hypothesizing thatPPCoccurrencecouldbepredictedfromareducedsetof perioperative variables, we aimed to develop a predictive index for a broad surgical population. Methods: Patients undergoing surgical procedures given general, neuraxial, or regional anesthesia in 59 hospitals were randomly selected for this prospective, multicenter study. The main outcome was the development of at least one of the following:respiratoryinfection,respiratoryfailure,bronchospasm, atelectasis, pleural effusion, pneumothorax, or aspiration pneumonitis. The cohort was randomly divided into a development subsample to construct a logistic regression model and a validation subsample. A PPC predictive index was constructed. Results: Of 2,464 patients studied, 252 events were observed in 123 (5%). Thirty-day mortality was higher in patients with a PPC (19.5%; 95% [CI], 12.5–26.5%) than in those without a PPC (0.5%; 95% CI, 0.2–0.8%). Regression modeling identified seven independent risk factors: low preoperative arterial oxygen saturation, acute respiratory infectionduringthepreviousmonth,age,preoperativeanemia, upper abdominal or intrathoracic surgery, surgical duration of at least 2 h, and emergency surgery. The area under the receiver operating characteristic curve was 90% (95% CI, 85–94%) for the development subsample and 88% (95% CI, 84–93%) for the validation subsample. Conclusion: The risk index based on seven objective, easily assessed factors has excellent discriminative ability. The index can be used to assess individual risk of PPC and focus further research on measures to improve patient care.

/pdf/prediction-of-postoperative-pulmonary-complications-in-a-24x3asnhsf.pdf

Prediction of Postoperative Pulmonary Complications in a Population-based Surgical Cohort

ContextHypoxemia complicates the recovery of 30% to 50% of patients after abdominal
surgery; endotracheal intubation and mechanical ventilation may be required
in 8% to 10% of cases, increasing morbidity and mortality and prolonging intensive
care unit and hospital stay.ObjectiveTo determine the effectiveness of continuous positive airway pressure
compared with standard treatment in preventing the need for intubation and
mechanical ventilation in patients who develop acute hypoxemia after elective
major abdominal surgery.Design and SettingRandomized, controlled, unblinded study with concealed allocation conducted
between June 2002 and November 2003 at 15 intensive care units of the Piedmont
Intensive Care Units Network in Italy.PatientsConsecutive patients who developed severe hypoxemia after major elective
abdominal surgery. The trial was stopped for efficacy after 209 patients had
been enrolled.InterventionsPatients were randomly assigned to receive oxygen (n = 104)
or oxygen plus continuous positive airway pressure (n = 105).Main Outcome MeasuresThe primary end point was incidence of endotracheal intubation; secondary
end points were intensive care unit and hospital lengths of stay, incidence
of pneumonia, infection and sepsis, and hospital mortality.ResultsPatients who received oxygen plus continuous positive airway pressure
had a lower intubation rate (1% vs 10%; P = .005;
relative risk [RR], 0.099; 95% confidence interval [CI], 0.01-0.76) and had
a lower occurrence rate of pneumonia (2% vs 10%, RR, 0.19; 95% CI, 0.04-0.88; P = .02), infection (3% vs 10%, RR, 0.27; 95%
CI, 0.07-0.94; P = .03), and sepsis (2%
vs 9%; RR, 0.22; 95% CI, 0.04-0.99; P = .03)
than did patients treated with oxygen alone. Patients who received oxygen
plus continuous positive airway pressure also spent fewer mean (SD) days in
the intensive care unit (1.4 [1.6] vs 2.6 [4.2], P = .09)
than patients treated with oxygen alone. The treatments did not affect the
mean (SD) days that patients spent in the hospital (15 [13] vs 17 [15], respectively; P = .10). None of those treated with oxygen plus
continuous positive airway pressure died in the hospital while 3 deaths occurred
among those treated with oxygen alone (P = .12).ConclusionContinuous positive airway pressure may decrease the incidence of endotracheal
intubation and other severe complications in patients who develop hypoxemia
after elective major abdominal surgery.

https://jamanetwork.com/journals/jama/articlepdf/200264/jce40057.pdf

Continuous positive airway pressure for treatment of postoperative hypoxemia: a randomized controlled trial

Atelectasis occurs in the dependent parts of the lungs of most patients who are anesthetized. Development of atelectasis is associated with decreased lung compliance, impairment of oxygenation, increased pulmonary vascular resistance, and development of lung injury. The adverse effects of atelectasis persist into the postoperative period and can impact patient recovery. This review article focuses on the causes, nature, and diagnosis of atelectasis. The authors discuss the effects and implications of atelectasis in the perioperative period and illustrate how preventive measures may impact outcome. In addition, they examine the impact of atelectasis and its prevention in acute lung injury.

Pulmonary atelectasis: a pathogenic perioperative entity.

Clinical and experimental studies have clearly established that mechanical ventilation with large tidal volumes is harmful to the lung. However, there is uncertainty about the micromechanics of injured lungs as well as many unanswered questions about the optimal levels of PEEP and tidal volume in individual patients. In this chapter we focus on the mechanical and molecular mechanisms of ventilator-induced lung injury, the characteristics of bronchopulmonary dysplasia and the eventual feasibility of selective targeted therapy for these conditions.

Ventilator-Induced Lung Injury

During mechanical ventilation, lung recruitment attenuates injury caused by high VT, improves oxygenation, and may optimize pulmonary vascular resistance (PVR). We hypothesized that ventilation without recruitment would induce injury in otherwise healthy lungs. Anesthetized rats were ventilated with conventional mechanical ventilation (VT 8 ml/kg; respiratory frequency 40 per minute) and 21% inspired oxygen, with or without a recruitment strategy consisting of recruitment maneuvers plus positive end-expiratory pressure, in the presence or absence of a laparotomy. Additional experiments examined the impact of atelectasis on right ventricular function using echocardiography, as well as functional residual capacity and PVR. Lack of recruitment resulted in reduced overall survival (59% nonrecruited vs. 100% recruited, p < 0.05), increased microvascular leak, greater impairment of oxygenation and lung compliance, increased PVR, and elevated plasma lactate. Echocardiography demonstrated that right ventricular d...

https://www.atsjournals.org/doi/pdf/10.1164/rccm.200210-1215OC

Atelectasis Causes Vascular Leak and Lethal Right Ventricular Failure in Uninjured Rat Lungs

Objective: Deliberate elevation of PaCO 2 (therapeutic hypercapnia) protects against lung injury induced by lung reperfusion and severe lung stretch. Conversely, hypocapnic alkalosis causes lung injury and worsens lung reperfusion injury. Alterations in lung surfactant may contribute to ventilator-associated lung injury. The potential for CO 2 to contribute to the pathogenesis of ventilator-associated lung injury at clinically relevant tidal volumes is unknown. We hypothesized that: 1) hypocapnia would worsen ventilator-associated lung injury, 2) therapeutic hypercapnia would attenuate ventilator-associated lung injury; and 3) the mechanisms of impaired compliance would be via alteration of surfactant biochemistry. Design: Randomized, prospective animal study. Setting: Research laboratory of university-affiliated hospital. Subjects: Anesthetized, male New Zealand Rabbits. Interventions: All animals received the same ventilation strategy (tidal volume, 12 mUkg; positive end-expiratory pressure, 0 cm H 2 O; rate, 42 breaths/min) and were randomized to receive FiCO 2 of 0.00, 0.05, or 0.12 to produce hypocapnia, normocapnia, and hypercapnia, respectively. Measurements and Main Results: Alveolar-arterial oxygen gradient was significantly lower with therapeutic hypercapnia, and peak airway pressure was significantly higher with hypocapnic alkalosis. However, neither static lung compliance nor surfactant chemistry (total surfactant, aggregates, or composition) differed among the groups. Conclusions: At clinically relevant tidal volume, CO 2 modulates key physiologic indices of lung injury, including alveolar-arterial oxygen gradient and airway pressure, indicating a potential role in the pathogenesis of ventilator-associated lung injury. These effects are surfactant independent.

Carbon dioxide attenuates pulmonary impairment resulting from hyperventilation.

Background:Atelectasis results in impaired compliance and gas exchange and, in extreme cases, increased microvascular permeability, pulmonary hypertension, and right ventricular dysfunction It is not known whether such atelectasis-induced lung injury is due to the direct mechanical effects of lung

Oxygen attenuates atelectasis-induced injury in the in vivo rat lung.

BACKGROUND Ultrasound-guided, internal jugular venous (IJV) cannulation is a core technical skill for anaesthesiologists and intensivists. OBJECTIVES At a modified Delphi panel meeting, to define and reach consensus on a set of objective ultrasound-guided IJV cannulation performance metrics on behalf of the College of Anaesthesiologists of Ireland (CAI). To use these metrics to objectively score video recordings of novice and experienced anaesthesiologists. DESIGN An observational study. SETTING CAI, March to June 2016 and four CAI training hospitals, November 2016 to July 2019. PARTICIPANTS Metric development group: two CAI national directors of postgraduate training (specialist anaesthesiolgists), a behavioural scientist, a specialist intensivist and a senior CAI trainee. Scoring by two blinded assessors of video recordings of novice (n = 11) and experienced anaesthesiologists (n = 15) ultrasound-guided IJV cannulations. MAIN OUTCOME MEASURES A set of agreed CAI objective performance metrics, that is, steps, errors, and critical errors characterising ultrasound-guided IJV cannulation. The difference in performance scores between novice and experienced anaesthesiologists as determined by skill level defined as being below or above the median total error score (errors plus critical errors): that is, low error (LoErr) and high error (HiErr), respectively. RESULTS The study identified 47 steps, 18 errors and 13 critical errors through six phases. Variability was observed in the range of total error scores for both novice (1 to 3) and experienced (0 to 4.5) anaesthesiologists. This resulted in two further statistically different subgroups (LoErr and HiErr) for both novice (P = 0.011) and experienced practitioners (P < 0.000). The LoErr-experienced group performed the best in relation to steps, errors and total errors. Critical errors were only observed in the experienced group. CONCLUSION A set of valid, reliable objective performance metrics has been developed for ultrasound-guided IJV cannulation. Considerable skill variability underlines the need to develop a CAI simulation-training programme using these metrics.

Development of objective performance metrics for ultrasound-guided internal jugular vein cannulation on behalf of the College of Anaesthesiologists of Ireland and observation of scores amongst novice and experienced operators

Michelle Duggan

Papers

Pulmonary atelectasis: a pathogenic perioperative entity.

Atelectasis Causes Vascular Leak and Lethal Right Ventricular Failure in Uninjured Rat Lungs

Carbon dioxide attenuates pulmonary impairment resulting from hyperventilation.

Oxygen attenuates atelectasis-induced injury in the in vivo rat lung.

Development of objective performance metrics for ultrasound-guided internal jugular vein cannulation on behalf of the College of Anaesthesiologists of Ireland and observation of scores amongst novice and experienced operators