Labs and Lytes 029
Author: Eamon Raith
Reviewers: Sarah Yong, Chris Nickson
A 50-year-old man is admitted to ICU postoperatively, following a ‘pedestrian versus car’ motor vehicle accident. He requires ongoing haemodynamic support with noradrenaline. A left subclavian CVC is inserted with dynamic ultrasound guidance.
Q1. Describe and interpret the chest radiograph (CXR)
A systematic approach to the assessment of the chest radiograph is required. A simple structure takes the following approach:
- Technical aspects
- Lungs & pleural cavity
- Heart & mediastinum
- Soft tissues
- Indwelling devices
This is an AP film of a supine patient. The most striking finding is the presence of extensive ‘hardware’:
- L) subclavian and R) IJ central lines, tips appropriately placed
- Endotracheal tube
- Thoracic spinal fixation
- Thoracic aortic stent
- Surgical staples
- ECG leads
- Film is minimally rotated, adequately exposed
- All aspects of interest are located within the field
Lungs and pleural cavity:
- Prominent horizontal fissure (right)
- Mild alveolar opacification in the left lower lobe, consistent with possible pulmonary contusion, given the mechanism of injury
Heart and mediastinum:
- Cardiothoracic ratio is ~50%, although that can be accounted for by the AP projection
- Right and left mediastinal contours appear normal
- Thoracic aortic stent, extending to the level of the left subclavian artery
- Bilateral rib fractures
- Thoracic spinal fusion
- Normal diaphragmatic outlines
- Absence of deep sulcus sign
The patient has a weak left radial artery pulse, and it is suspected that the aortic stent has compromised distal flow to the left arm. A CT aortogram is ordered.
Q2. Describe and interpret the pilot image shown below.
The most striking finding is the presence of a ‘deep sulcus sign’ on the left, with hyperlucency and absence of lung markings, consistent with a left pneumothorax.
Other findings include:
- Left rib fractures
- Possible tracheal deviation to the right (difficult to determine given the presence of metalwork and the patient’s positioning)
- Hardware: ETT, L) internal jugular CVC, thoracic spinal fusion, pelvic external fixation and ECG leads
Q3. What is the ‘deep sulcus’ sign?
The deep sulcus sign is an indirect sign of a pneumothorax, found on supine chest radiographs. It is caused by the non-dependent distribution of intrapleural air, producing abnormal anterior diaphragmatic lucency, and thus a deepening of the costophrenic angle, as air tracks latero-caudally.2
Q4. How common is pneumothorax post CVC insertion? How can this risk be minimised?
Pneumothorax is a common complication of CVC insertion, representing up to 30% of mechanical adverse events. The likelihood of mechanical complications is largely determined by three categories of factors;1
- Patient-related factors (underlying disease, co-morbidity, anatomy, compromised procedural settings, patient restlessness or lack of co-operation, previous operations/trauma/radiotherapy).
- Catheter-related factors (site, catheter type).
- Clinical factors (Operator experience, previous catheterizations, catheterization attempts, emergency vs. elective situation).
Pneumothorax is the most likely mechanical complication associated with subclavian vein cannulation (see below).1
CVC-associated pneumothorax can be prevented or rapidly managed through the following:
- Recognition of risk factors for difficult catheterization
- Use of a standard method of CVC insertion
- Assistance from an experienced clinician,
- Use of ultrasound guidance
- Early recognition of the presence of pneumothorax
- Use of a standardized treatment algorithm.
The rationale for each of these interventions is outlined in the table below;1
References and Links
- Tsotsolis N, Tsirgogianni K, Kioumis I. Pneumothorax as a complication of central venous catheter insertion. Annals of translational medicine. 3(3):40. 2015. [pubmed] [free full text]
- Sabbar S, Nilles EJ. Images in clinical medicine. Deep sulcus sign. The New England journal of medicine. 366(6):552. 2012. [pubmed] [free full text]