Predictions and Prevention for Postoperative Remote Lung Injury
Postoperative remote lung injury and/or PPC are not uncommon following major surgical procedures.[57,59,60] As a result, it is important to be able to predict risk factors and consider appropriate precautions. In 1997, Brooks-Brunn analysed data from 400 patients underwent abdominal surgery. Six out of twenty-three risk factors were identified: age over 60, impaired preoperative cognitive function, smoking history within the past 8 weeks, body mass index over 27, history of cancer and the incision-site. In another prospective survey with patients underwent general elective surgery, postoperative nasogastric intubation, preoperative sputum production and longer duration of anaesthesia were identified as modifiable risk factors. Given the high rate of pulmonary complications and the high mortality rates following oesophagectomy, Law et al. analysed data from 421 patients to further investigate potential predictive factors for PPC. Logistic regression analysis identified three predictive factors for PPC: advanced age, operation period and proximal tumor location.
In 2010, a large prospective, multicentre study reported that 5% of patients developed PPC. Seven independent risk factors were identified, including low preoperative arterial oxygen saturation, acute respiratory infection in the last month, age, preoperative anaemia, upper abdominal or intrathoracic surgery, surgical operation lasting more than 2 h and emergency surgery. In another multicentre cohort research, Kor et al. re-evaluated the risk factors for post-surgical ARDS. In contrast to the previous study in 2010, they found nine independent risk factors contributed to postoperative lung injury: sepsis, high-risk aortic vascular surgery, high-risk cardiac surgery, emergency surgery, cirrhosis, admission locations other than home, increased respiratory rate, FIO2 greater than 35% and SpO2 less than 95%. This study also indicated that the surgical lung injury prediction (SLIP) score is of inferior power in this high-risk population than SLIP-2, which is more accurate in diverse and acutely ill patients. However, due to variation in clinical settings in different centres, there is still no standardized prediction scale available worldwide. Furthermore, one recent study reported by Fernandez-Bustamante et al. showed that PPCs are common in patients in spite of protective ventilation settings. They also revealed 3 non-modifiable risk factors as emergency, surgical site and age, and 5 modifiable factors of colloid administration, preoperative oxygenation, blood loss, anaesthesia duration and tidal volume. All those risk factors are summarized in the Table 1.
Identification of risk factors allows clinicians to predict postoperative remote lung injury. However, efforts to improve ventilation strategies during surgery are also vital. Amongst patients without ARDS at the onset of ventilation, fewer patients develop lung injury under protective ventilation compared to conventional ventilation. In a population underwent major abdominal surgery, lung protective ventilation during surgery was associated with a lower incidence of PPC and better clinical outcome. Furthermore, Severgnini et al. reported that protective ventilation during abdominal surgery correlated with improved pulmonary function after surgery. A meta-analysis by Serpa Neto et al. reported that patients ventilated with low tidal volume (VT) are less likely to develop PPC. While another large RCT compared the effect of high or low positive end expiratory pressure (PEEP) on PPC occurrence, surprisingly, the strategized combination of high PEEP and recruitment manoeuvres failed to protect against PPC. The authors, therefore, suggested that intraoperative protective ventilation should consist of a low VT and low PEEP without recruitment manoeuvres. Patients may respond to the same ventilation strategy and the same presumed protective ventilation strategy (low VT with high PEEP) may produce controversial results. Different from the result from the PROVHILO trial, Spadaro et al. showed that low VT together with PEEP at 10 cm H2O is protective during one lung ventilation.
BMC Anesthesiol. 2019;19(30) © 2019 BioMed Central, Ltd.