Perioperative Diaphragmatic Ultrasound as Predictive Index of Atelectasis in Bariatric Surgery (ECODIA)

Is the Perioperative Change in Ultrasound-based Diaphragmatic Inspiratory Amplitude Predictive of Postoperative Atelectasis: A Prospective Observational Study in Obese Patients Undergoing Bariatric Surgery

In this study the Authors assume that peri-operative changes in DIA are predictive of postoperative atelectasis, thus providing a clinically useful tool to stratify the need for high-intensity monitoring, including admission to intensive care. Aim of this prospective observational study, in obese patients undergoing sleeve gastrectomy, is to evaluate the relationship between pre to postoperative changes in US-DIA and PaO2/FiO2.

Obese patients undergoing bariatric surgery, are at high risk for postoperative respiratory complications but predictive variables, risk factors and criteria for postoperative ICU admission are debated. In these patients, postoperative respiratory complications are related to various pathophysiological mechanisms that include: decreased lung volumes, respiratory muscle dysfunction and atelectasis. Very recently it has also been demonstrated a possible role of molecules that would mediate the fibro-adipogenic remodeling of the diaphragm in the obese, thus increasing the respiratory disability. Pulmonary atelectasis appears within minutes after anesthesia induction, complicate 85-90% of the cases -involving up to 15% of the lungs and inducing a 5 to 10% of cardiac output intra pulmonary shunting- and determine an increased incidence of postoperative morbidity (with higher incidence of pneumonia). Furthermore, in the perioperative period, obese patients are more likely to develop atelectasis that resolves more slowly than in non-obese patients. Surgical handling of sub diaphragmatic region, as during sleeve gastrectomy, can impair diaphragmatic excursions thus contributing to postoperative pulmonary dysfunction. The same upper abdominal surgery represents a risk factor for the development of pulmonary complications in the perioperative period and alteration of the respiratory function indices. Ultrasounds (US) imaging is a real-time, bedside, non-invasive technique that allows the quantitative evaluation of amplitude, force and velocity of diaphragmatic movement, including: diaphragmatic inspiratory amplitude (DIA) and diaphragmatic thickening. The US-DIA is a qualified quantitative approach to assess diaphragmatic function and has been reported to linearly correlate with vital capacity. Recent studies have also correlated diaphragmatic dysfunction, which reduces the ability to generate total current volume, with the onset of atelectasis, but in a very specialized and dedicated area such as thoracic surgery. The originality of the study lies in the fact that the investigators have translated this method of evaluation of diaphragmatic function, as a predictive index of pulmonary complications in postoperative surgery, into a highly selected and clinically demanding type of patient, such as the patient suffering from pathological obesity. Several guidelines have been created at European level for the perioperative management of the obese patient. One of the most recent is the one created by the Italian Society of Anaesthesia Analgesia Rianimazione e Terapia Intensiva (SIAARTI), which commissioned an "Obesity Task Force" of the Airway Management Study Group to coordinate a multidisciplinary multi-professional consensus project to identify bundles of Good Clinical Practices (GCPs), useful to define the risks in adult obese patients in hospital. In obese patients undergoing sleeve gastrectomy there are no conclusive criteria for discharge and indications to postoperative ICU admission, as recently defined for patients with OSAS, the investigators hypothesize that perioperative change in US-DIA predicts postoperative atelectasis, thus providing a clinically useful tool to stratify the need for higher intensity monitoring including ICU admission.

Obesity is a progressively growing morbid condition in the world, and given the direct relationship between body mass index (BMI) and costs, this has a major impact on economic and health policy. Obese patients undergoing bariatric surgery are at high risk for postoperative respiratory complications. In these patients, postoperative respiratory complications are related to various pathophysiological mechanisms that include: decreased lung volumes, respiratory muscle dysfunction and atelectasis. Demographic (age, gender, BMI) and clinical features of the population included: ASA, comorbidity and pre and postoperative respiratory function [PaO2/FiO2, haemogasanalysis (EGA)]. Ultrasound evaluation of DIA was performed. T0: preoperative within 24h before surgery: DIA, haemogasanalysis; T1: Post operation: 60 min after extubation: Aldrete Score, DIA, EGA; T2: Post operation: 240 min after extubation: Aldrete, EGA.

Diaphragmatic ultrasound is non-invasive, portable, quick to perform, with a linear relationship between diaphragmatic movement and inspired volume. In eligible patients, a preoperative baseline ultrasound evaluation of the diaphragm and lungs is accomplished. Evaluation will be performed by a single operator, blinded to the arterial blood gas analysis values. In a semi recumbent position, patients will be asked to rest and breath quietly. An anterior approach will be carried out applying freehand transducer on abdomen at the right midclavicular line immediately below the costal margin with firm pressure, steering in cranial direction. A B-mode transverse scanning will be performed looking across the liver with gallbladder in the middle. Measurements will be recorded by the M-mode frozen images. The M-mode modality will be used to study DIA. The best sinusoidal curve will be considered for measurements.

to detect the relationship between perioperative changes in DIA, (unit of measurement "millimeters") finally expressed as percentage differences at the baseline, during forced breath and occurrence and severity of postoperative atelectasis (evaluated through PaO2/FiO2 R) at 240 min after extubation (T2), view with haemogasanalytic measurement.

concentration of myorelaxants, expressed in milligrams, used during surgery. Measurement tool is the TOF Ratio [TOF Ratio, is the ratio of the amplitude of the fourth muscle response to the amplitude of the first]. Monitoring guide acceleromyographic train-of-four stimulus to the adductor pollicis.

Quantification of the difference in diaphragmatic excursion, DIA (unit of measurement "millimeters") finally expressed as percentage differences at the baseline, during calm breathing between the pre-operative T0 time and the T1 time at 1 hour after the end of the operation.

The detection of pneumonia was carried out with CURB-65, a simple predictive clinical score based on mental confusion, azotemia (mg/dL), respiratory rate (n breaths/min), blood pressure (mmHg) and age (years). In addition, a chest X-ray was performed to highlight the presence of infiltrations.

% of the patients need recovery in intensive care due to the onset of a complication during the post-operative course.

Inclusion Criteria: morbid obesity undergoing bariatric surgery (BMI >30 Kg/m2) Exclusion Criteria: Heart Failure Neuromuscular Diseases Previous Thoracic Surgery, American Society of Anesthesiology physical (ASA) status >III.

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