Bedside Ultrasound in the Diagnosis and Treatment of Children with Respiratory Difficulty Following Cardiac Surgery

Figure 1. Illustrating image of transducer positions in postoperative cardiac children with respiratory difficulties; Zone 1: Imaging vocal cords in a transverse view of the larynx at the thyroid cartilage; Zone 2: Imaging lung sliding sign and lung point in each anterior chest in the mid clavicular line at 2nd–3rd intercostal space; Zone 3: Imaging lung point and lung sliding in each lateral chest in anterior axillary line inferior to nipple; Zone 4: Diaphragm function, hepatorenal fluid accumulation, pleural effusion, and lung consolidation, or collapse in each posterior chest in posterior axillary line; Zone 5: Subxiphoid window of the heart and both diaphragm; Zone 6: Imaging intraabdominal collection in each iliac fossa. Zone 7: The heart is screened to assess heart function, pericardial effusion and residual lesions.

Figure 2. Algorithm for enhanced ultrasound approach in postoperative cardiac children with respiratory difficulties. *Consider other causes of stridor in case of normal vocal cords movements (such as edema, subglottic stenosis).

Figure 3. Two neonates postcoarctation of the aorata repair through left thoractomy, developed stridor postextubation. Vocal cords ultrasound helps to visualize vocal cord function through transverse sonograms of the true vocal cords in abduction; (a): Normal movements, (b): Left vocal cord dysfunction. True vocal cords appeared as 2 hypoechoic structures (the vocalis muscles), outlined medially by the hyperechoic vocal ligaments (white arrow), extending from the inner cortex of the thyroid cartilage to the vocal process of the arytenoid cartilage. AC indicates arytenoid cartilage; asterisks: Thyroid cartilage, and VM: Vocalis muscle.

Video 1. A 3-week neonate postcoarctation of the aorata repair, developed sudden respiratory distress and stridor after extubation most likely related to edema; two-dimensional comparative sonogram imaging shows normal vocal cords movements. Arrows indicate right and left vocal cords.

Video 2. A 4-week neonate posttruncus arteriosis repair, developed sudden respiratory distress and stridor after extubation related to left vocal cord paralysis; two-dimensional comparative sonogram imaging of vocal cords movements shows left vocal cord paralysis; arrow indicates left vocal cord paralysis.

Video 3. A 4-week neonate postarterail switch operation and interrupted aortic arch repair developped respiratory distress after extubation with paradoxical breathing pattern; diaphragm ultrasound (two-dimensional) demonstrates left diaphragm paralysis in subcostal view with absent movement compared to the right diaphragm; diaphragm ultrasound (M-mode) shows a flat line of the left diaphragm.

Video 4. A 33-day infant with aortic stenosis, coarctation of the aorta and ventricular septum defect underwent for Yasui procedure, had difficulty to wean from ventilator and chest X-ray showed high cupula of the left diaphragm; diaphragm ultrasound (two-dimensional and M-mode) demonstrates left diaphragm paralysis in subcostal view with paradoxical movement compared to the right diaphragm; diaphragm ultrasound (M-mode) of the left diaphragm confirmed paradoxical movements during inspiration with negative excursions (−2 mm).

Figure 4. Diaphragm function by M mode ultrasound in four infants with extubation failure postcardiac surgery: (a) Normal right diaphragm movement in infant postventricular septum defect repair: Upward diaphragm motion with amplitude (5.8 mm) during inspiration in sagittal plane. (b) Left diaphragm paresis in infant postarterial switch operation: Normal direction toward the transducer, but the excursion is decreased (3.2 mm) in sagittal plane. (c) Left diaphragm paralysis in infant postglenn shunt: Flat M mode ultrasound tracing in oblique transverse plane in sub xiphoid window. (d) Left diaphragm paralysis posttetralogy of Fallot repair: Paradoxical inspiratory motion in oblique transverse plane in sub xiphoid window. In indicates inspiration.

Figure 5. A 2 month old infant post Blalock Taussig shunt with difficulty to liberate from ventilator: (a) Ultrasonographic longitudinal view of the left inferior chest region shows pleural effusion surrounding the collapsed lung, delimited by the costodiaphragmatic recesses (white arrow), and spleen; The distance is around 18 mm between diaphragm and collapsed lung (asterisks). (b) Ultrasound guided pleural centesis using linear probe; 100 ml (30 ml/Kg) serous fluid drained. (c) Chest X ray demonstrating minimal amount of the left pleural effusion blunting the costodiaphragmatic angle. (d) Chest X ray after pigtail insertion; The costodiaphragmatic angle is clearer. (e) Longitudinal ultrasonographic view after effusion drainage revealed reopening and expansion of the lung with the absence of pleural fluid.

Figure 6. A 4-year-old child with high pressure Fontan developed respiratory distress. Ultrasonographic longitudinal view of the left inferior chest region shows pleural effusion of a large size with heterogeneous consistency; Pleural fluid analysis revealed chylothorax.

Figure 7. A 2-year hypotonic child with persistent dyspnea and fever postbilateral pulmonary artery reconstruction: (a) Ultrasonographic longitudinal view of the right inferior chest region shows collapsed lung with mild pleural effusion; the airless lung is similar in echogenicity and echo-texture to liver. (b) Ultrasonographic longitudinal view of the left inferior chest region shows punctiform air bronchograms (white arrows) and branching tubular structures (black arrows) within the consolidated lung parenchyma. (c) M-mode of the left consolidated lung shows dynamic air bronchograms in sinusoidal line with the inspiratory excursion (in) of 2 mm.

Video 5. A 1-year-old infant with significant residual mitral valve regurgitation after repair; presented with difficulty to liberate from ventilator due to pulmonary interstitial syndrome with cardiogenic pulmonary edema; sonographic appearance of pulmonary congestion demonstrating multiple vertical hyperechoic B-lines (white-out) originating from the pleural line and spreading like a laser ray up to the edge of the screen, the pleural thickness looks normal. Sonographic follow-up of pulmonary congestion after diuresis and positive pressure ventilation shows some improvement (decrease) in B-lines intensity and number.