Prognostic Value of Lung Ultrasound in Predicting Intensive Care Unit Length of Stay in Adult Cardiac Surgery
Condition: Coronary Artery Disease; Valvular Heart Disease
MeSH terms: Coronary Artery Disease; Heart Diseases; Heart Valve Diseases
Study type: Observational

Summary: 
      Being easy, bedside, non-expensive, noninvasive and radiation free, there has been a growing
      interest in the implementation of lung ultrasound in critical care management in the last
      decade, cardiac surgery was not an exception in both adult and pediatric surgeries Many
      predictors for open heart surgery outcomes have been studied in past years including The
      Society of Thoracic Surgeons (STS) risk score and the EuroSCORE (ES), preoperative clinical
      condition, associated chronic diseases, type of surgery, age, duration of cardiopulmonary
      bypass and brain natriuretic peptide (BNP), cystatin-C A recent study described the use of a
      novel postoperative lung ultrasound score scanning for B lines which denote subpleural
      interstitial edema in various lung regions for predicting critical care length of stay in
      pediatric cardiac surgeries.

      The objective of the current study is to evaluate the role of the new lung ultrasound score
      in predicting the length of postoperative intensive care stay after adult open heart
      surgeries.
    

Detailed description: 
      After approval of the local institutional ethics committee and local institutional review
      board. All patients scheduled for open heart surgery in Fayoum university hospital starting
      from August 2020 will be enrolled in this prospective observational study until fulfilling
      sample size. A detailed informed consent will be signed by the eligible participants before
      recruitment ANESTHETIC TECHNIQUE All patients will be preoperatively assessed and
      investigated by complete blood count, coagulation profile, Liver and kidney functions and
      serum electrolytes. Chest X-ray, Electrocardiography (ECG) and echocardiography will be
      routinely done. Coronary angiography and carotid arterial duplex will be requested if needed.

      Patient will be premedicated by 10 mg morphine intramuscularly at morning of the operation.
      Prior to induction of anesthesia, standard monitoring will be applied including a five-lead
      electrocardiography system, a pulse oximeter probe. A peripheral intravenous (IV) cannula
      will be placed. An arterial will be inserted using a 20 G cannula either right or left radial
      artery under local anesthesia. After pre-oxygenation, general anesthesia will be induced
      using midazolam 2-5 mg, fentanyl (3-10 μg/kg), propofol (1-1.5 mg/Kg), followed by atracurium
      (0.5 mg/kg).

      After trachea intubation, patients will be mechanically ventilated with oxygen in air so as
      to achieve normocarbia. A main stream capnogram, an esophageal temperature probe and a Foley
      catheter will also be placed. A triple-lumen central venous catheter will be placed usually
      through the right internal jugular vein.

      Maintenance of anesthesia will be achieved by inhaled Isoflurane 0.4 to 1% and atracurium
      infusion at a rate of 0.5 mg/kg/h. After initiating extracorporeal circulation, Propofol
      infusion at a rate of 50-100 µg/kg/min will be added to replace isoflurane inhalation.

      Patients will receive intravenous heparin (300-500 IU/kg body weight) before the initiation
      of cardiopulmonary bypass (CPB) to achieve an activated clotting time (ACT) of more than 480
      seconds. Cardiopulmonary bypass was instituted with the use of a non-pulsatile blood flow at
      2.4 L/min/m2, a non-heparin-coated circuit, and a membrane oxygenator. Mean arterial pressure
      will be adjusted to exceed 60mmHg before, during and after cardiopulmonary bypass (CBP) .
      Cardiac arrest will be induced using St Thomas crystalloid solution (Hamburg). Lactated
      Ringer's solution will be added to the CPB circuit to maintain reservoir volume if needed,
      and packed red blood cells will be infused when hemoglobin level drops to less than 7g/dl.
      After rewarming the patient to 37°C and weaning from CPB; Protamine sulfate will be used to
      reverse the effect of heparin.

      After skin closure and wound dressing, patients will be transferred to the intensive care
      unit intubated with manual ventilation and full monitoring during transfer.

      Intensive care Tracheal extubation will be performed when the patient meets the following
      criteria: awake or arousable, hemodynamically stable, no ongoing active bleeding, warm
      extremities, no electrolyte abnormalities, no or minimal inotropic support and a satisfactory
      arterial blood gas with a fraction of inspired oxygen (FiO2) < 0.5, Ventilator pressure
      support reduced to 10 CmH2O with Positive End Expiratory Pressure (PEEP) 5-7 CmH2O.

      ICU management and decisions will be left to the intensivist who is responsible of the
      postoperative cardiac critical care.

      Patient will be discharged from ICU when the following criteria are met: Awake patient with
      oxygen saturation (SpO2) < 90% at FIO2 > 0.5 by facemask, adequate cardiac stability, no
      intravenous inotropic or vasopressor supportive therapy, no hemodynamically significant
      arrhythmia, not dependent on epicardial external pacing no major bleeding i.e. chest tube
      drainage less than 50 ml/h, urine output of more than 0.5 ml/kg/h and no vital threats to
      other organ systems such as kidneys and liver.

      Lung Ultrasound scan (LUS) All patients will be examined at 12 hours postoperatively as per
      our institution routine using a convex ultrasound probe, any other LUS will be done upon
      demand.

      LUS will be performed by an experienced radiologist according to standardized protocols.

      This will be used to calculate total LUS-score (calculated as a sum of all quadrants score)
      and individual areas score.

      Sample size was calculated using (G power). Minimal sample size of patients was 191 needed to
      get power level 0.80, alpha level 0.05 (two tailed) and 0.20 as expected β (slope of
      regression line) for predicting intensive care Length of stay .

      Data management will be performed using the Statistical Package for Social Sciences (version
      22.0; SPSS Inc., Chicago, IL, USA). Descriptive statistics (mean, standard deviation for
      quantitative data, and number and percentages for qualitative data) will be used to summarize
      the data. Nominal data will be analyzed using simple chi squared test, while independent
      sample t-test or one-way ANOVA procedure will be used to compare means for two or three
      groups of cases, respectively. Regression analysis will be performed to determine the
      predictors for LOS. A probability value (P value) ≤ 0.05 is considered significant.
    

Intervention name(s): Lung ultrasound scan
Intervention type(s): Diagnostic Test
Intervention description(s): 12 hours postoperatively using a convex ultrasound probe LUS will be performed by an experienced radiologist according to standardized protocols. For each hemi-thorax 3 main areas (anterior (Ant), lateral (Lt) and posterior (Post)) marked by the para-sternal, anterior axillary and posterior axillary lines will be identified. Each one will be divided into upper and lower halves, making a sum of 6 different quadrants for each side: anterior superior, anterior inferior, lateral superior, lateral inferior, posterior superior, posterior inferior.
For each quadrant a score will be assigned based on B lines which are defined as comet like artifacts indicating subpleural interstitial edema as follows:
(0) normal aeration: A lines with lung sliding or fewer than two isolated B lines; (1) moderate loss of lung aeration: well-defined, multiple B lines ; (2) severe loss of lung aeration: multiple coalescent B lines; and (3) complete loss of lung aeration or lung consolidation.
Observational model: Cohort
Time perspective: Prospective
Sampling method: Non-Probability Sample
Study population: 
        patients admitted in Fayoum uniersity hospital who are candidates for open heart surgeries
      
Keywords: Lung ultrasound; coronary artery bypass graft (CABG); open heart surgery; ICU LOS