Perioperative Lung Protective Ventilatory Management During Major Abdominal Surgery: A Hungarian Nationwide Survey

Lung protective mechanical ventilation (LPV) even in patients with healthy lungs is associated with a lower incidence of postoperative pulmonary complications (PPC), resulting in better outcomes, shorter length of hospital stay, and lower healthcare-associated costs [1,2]. The multifactorial pathophysiology of ventilator-induced lung injury (VILI), the surgery, the anaesthesia and the patient-related risk factors of PPCs have been widely reported in the literature [3, 4, 5, 6, 7]. Based on this, the concept of perioperative lung protective management emerged, including preoperative breathing physiotherapy, positive pressure respiratory support, prophylactic perioperative positive pressure ventilation (POP-ventilation), continuous positive airway pressure (CPAP), non-invasive ventilation (NIV), intraoperative LPV, applying low tidal volumes, moderate levels of positive end-expiratory pressure (PEEP) and regular ARM has been elaborated [8,9,10]. Despite the well-known advantages, Schultz MJ et al. (2017) concluded that intraoperative LPV is still not widely implemented in everyday anaesthesia practice even in high-risk surgical patients and it has been suggested that much more attention should be given to the use of lung protective strategies during general anaesthesia [11,12].

Several differences are known to exist between Eastern and Western Europe health care systems and patient management[13]. As no data exists from Eastern Europe, including Hungary, a decision was made to survey members of the Hungarian Society of Anaesthesiology and Intensive Therapy (HSAIT) regarding the routine anaesthetic care, awareness and adherence to the LPV concept during major abdominal surgery.

A questionnaire of thirty-six “mandatory-to-answer” multiple-choice questions divided into five sections had been prepared and tested on a pilot sample of three expert anaesthesiologists to check the clarity and validity of the questions and to estimate the completion time of the survey. Agreement of any ethics committee was not necessary as the questionnaire was about the professional practice of anaesthesiologists, and participation was voluntary and anonymous. There were no exclusion criteria and the study complied with the survey-reporting list.

After the questionnaire was considered appropriate, Hungarian anaesthesiologists were invited by email and by a newsletter, to participate in an online survey between January 1st to March 31^st, 2018, using the public e-mail database of the Hungarian Hospital Federation (Magyar Kórházszövetség). A cover letter containing the investigators’ names and contact details, the objectives, aims and methodology of the study was attached. The online questionnaire was published using Google Forms (Google Inc., Mountain View, CA).

Demographic data of respondents, routine preoperative, intraoperative and postoperative pulmonary management and opinions of participants about the risk factors of PPCs were evaluated in different sections. The primary endpoint was the frequency of consistent application of the three basic elements of LPV: low tidal volume (TV) ≤ 6 ml/kg ideal body weight (IBW), PEEP of 6 cmH₂O at least and regular ARMs. Secondary endpoints were the respiratory rate, application of permissive hypercapnia [end tidal carbon dioxide tension (EtCO₂) 35-40 mmHg], low plateau pressure (Pplat < 25 cmH₂O) and low driving pressure (ᐃPaw < 20 cmH₂O), use of neuromuscular blocking agent antagonists (NMBA-A) and prevalence of perioperative pulmonary management protocols. The tertiary endpoint was the opinion of respondents about the risk factors of PPCs.

The difference, if any, in the way trainees and specialists practised and the difference in the standard of care between university hospitals and other hospitals was assessed.

The questionnaire was designed to evaluate the routine perioperative pulmonary management practice during major abdominal surgery in Hungary. The reporting list described by Story et al., (2017) was used to obtain consistency, clarity, reproducibility and validity of the survey report [14].

Major abdominal surgery is considered a high-risk intervention associated with the risk of development of PPCs [6,15]. Furthermore, it is often an urgent or vital procedure performed in high-risk patients with serious comorbidities such as cardiovascular and chronic pulmonary diseases, life-threatening intraabdominal

infections or malignancies leading to chronic malnutrition. Applying LPV during major abdominal surgery is considered rational or even appropriate.

Advantages of LPV in patients with acute respiratory distress syndrome (ARDS) were described in the early ‘90s leading to intensive research [16, 17, 18]. Amato et al. (1998) found significantly better survival rates in the LPV group than in the conventional ventilatory group, and this finding was strengthened by the investigators of the Acute Respiratory Distress Network (2000) [19,20].

Results of the study by Futier et al. (2013) emphasised that LPV during abdominal surgery, even in patients with healthy lungs, is associated with a lower incidence of PPCs, resulted in improved outcomes, shorter length of stay in a hospital and reduced health care utilisation.[1] These findings were confirmed and the multifactorial pathophysiology of VILI and the risk factors of PPCs had been thoroughly evaluated. [2,3,4, 9,10]. Based on this knowledge and the pathophysiological rationale, Futier et al. (2014) established a new integrated approach called “perioperative positive pressure ventilation” (POP concept) to improve pulmonary care [8]. Despite existing evidence, the work of Fischer et al. (2016) indicated that ventilatory management practice in cardiac surgery varied markedly between anaesthesiologists [21]. Colinet et al. (2017) were of the opinion that the use of protective ventilation during anaesthetic care is still not used frequently enough. This may be due to lack of knowledge and therefore indicates an urgent need for education and regular training [22]. Schultz et al. (2017) opined that intraoperative LPV is still not widely implemented in everyday anaesthesia practice even in high-risk surgical patients, further suggesting that attention should be given to the use of lung protective strategies during general anaesthesia [11].

The present results indicate that applying low TV based on IBW is common and it is implemented in everyday anaesthesia practice, although the use of moderate levels of PEEP and even more regular ARMs are usually ignored, not to mention that individually titrated levels of PEEP are seldom employed. In patients with a BMI greater than 30 kg/m², slightly higher levels of PEEP are accepted, and PEEP titration procedures seem to be employed more commonly in this patient group. Based on this survey, ARM is a procedure used when a decreasing oxygen saturation (SpO₂) is detected. Application of permissive hypercapnia and determination of appropriate respiratory rate based on capnography are common during general anaesthesia, but somewhat more sophisticated elements such as low Pplat and ᐃPaw are used only by experts, which may be due to the low availability rate of written intraoperative ventilatory protocols or the shortcomings of regular education and training sessions. A significant number of examinations such as chest X-ray, spirometry and ABGA are carried out during the preoperative assessment, especially in the high-risk patient groups with chronic obstructive pulmonary disease (COPD), patients with actual respiratory diseases or patients with decreased SpO₂.

However, perioperative pulmonary care, the socalled POP concept, is not generally used according to the survey findings. It is also important to note that constant access to CPAP or NIV devices is limited in several institutions. These findings altogether explain that consistent and entire application of LPV and POP concepts are rare, resulting markedly, but insignificant differences between anaesthesiologists and institutions.

The main risk factors of PPCs are well-known, but some issues such as chronic malnutrition or prolonged use of nasogastric tube after surgery as negligible factors indicate the absence of an ERAS approach, maybe due to reasons such as the absence of written protocols or the shortcomings of regular education, described earlier.

The survey suffers from some limitations. First, the survey was declarative, and the response rate was relatively low with only approximately 15% of all anaesthesiologists responding. Secondly, to maintain anonymity, sensitive personal or institutional data were not collected; therefore, neither the exact number of participating institutions nor regional distribution were evaluated. Thirdly, the anchoring effect may have influenced the answers to the subsequent questions. Randomising the order of questions could have eliminated this problem, however, this approach could have affected the coherence of the survey significantly.

The results of a nationwide survey are very similar to that of earlier international surveys and reports, indicating that variations in practice of perioperative respiratory management occur nationally and worldwide. More attention should be given to the use of lung protective strategies during general anaesthesia. Implementation of recent guidelines, developing local institutional protocols and continuous, high-quality education and regular training sessions are essential to improve postoperative outcomes in high-risk patients undergoing major abdominal surgery.