Bedside Chest Ultrasound in post operative pediatric Cardiac Surgery patients: Comparison with bedside chest radiography.
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2019-12-31
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Abstract
Traditionally, chest imaging in post operative cardiac surgical patients, is
performed using bedside chest radiography (CXR). It is considered as standard of care to
evaluate intra-thoracic structures including heart, lung, mediastinum and their
abnormalities. CXR also evaluates position of chest tubes, mediastinal tubes, central
venous lines, pulmonary artery catheters, endotracheal tubes and enteral feeding tube [1].
Respiratory complication is one of the major causes of morbidity and death in
cardiac post operative patients in adult and pediatric population. Whenever there is a
suspicion of intra thoracic pathology, including improper position of tubes and catheters,
the need for repeated bedside CXR and thus subsequent unavoidable radiation exposure
is inevitable. Other factors leading to the need for repetition of bedside CXR are
suboptimal X-ray films, improper positioning of patient and poor correlation with CT
scan [2].
Each bed side CXR exposes a patient to 0.02 milli-sieverts of radiation [3].
Though it looks invariably small, repeated CXRs exposes patient to increasing amounts
of radiation. Paediatric age group especially neonates , have greater areas of exposure,
due to small body surface area and are thus sensitive to hazardous effects of ionizing
radiation. The threat of developing immune dysfunction, cataract, cognitive decline and
malignancy in later part of life is a possibility [4]. Therefore, effort should be made to
minimize radiation exposure whenever possible [5].
Chest ultrasound (CUS) is a fast, repeatable and radiation free methodology. 2
It is simple to use and requires a limited period of training [6]. It allows for bedside
detection of primary pulmonary pathologies [7] such as pleural effusion, pneumothorax,
lung atelectasis, or secondary pulmonary pathologies due to cardiac causes (interstitial
pulmonary oedema, basal atelectasis) and conditions such as diaphragmatic palsy,
subcutaneous emphysema, pericardial effusion, cardiac tamponade and endobronchial
intubation [8]. Examination can be done alone or in combination with echocardiography
and intravascular volume assessment, thus reducing cost and time.
Diaphragmatic dysfunction, due to phrenic nerve injury, is a complication in
postoperative cardiac surgery patients, with an incidence between 0.3% - 20% [9]. Most
phrenic nerve injuries are due to transient neuroapraxia of the nerve, secondary to
traction, local application of cold solutions, or accidental injury [10]. Rarely, it is caused
by direct transection of the phrenic nerve. Diaphragmatic dysfunction impedes normal
lung expansion during inspiration [9] and weaning from mechanical ventilation becomes
difficult. It is associated with prolonged ventilatory support, intensive care stay, increased
risk of nosocomial infections, and an overall morbidity and death [11].
Chest fluoroscopy is the gold standard for diagnosis of diaphragmatic
dysfunction. But it is associated with shifting of critically ill children to radiology suite
and exposure to higher ionizing radiation. Other modalities include phrenic nerve
conduction studies and CUS. CUS being a rapid and easily available technique at the
bedside, allows for early diagnosis of abnormal diaphragmatic motion [12]. 3
The use of CUS in the post operative adult cardiac patients is gaining popularity
[6]. However, there is little data available concerning the use of CUS in the post
operative cardiac pediatric and neonatal populations [13]. To address the above issue, we
intend to study the degree of agreement between CUS and CXR; to compare the
diagnostic performance of bedside chest ultrasound (CUS) with bedside chest
radiography (CXR), for the detection of abnormalities of thorax including abnormal
diaphragmatic motion, in postoperative pediatric cardiac surgical patients. We also intend
to compare the therapeutic interventions done on basis of CUS and CXR derived
information in the postoperative setting.