Endotracheal and Tracheostomy Tubes
Both endotracheal intubation and tracheostomy may cause potentially serious complications. Malpositioning of the endotracheal tube (ETT) occurs in approximately 15% of endotracheal intubations. The clinical assessment of tube location is frequently inaccurate, and a chest radiograph should be obtained immediately following intubation. With the neck in neutral position, the ideal position of the tube tip is 5 to 7 cm above the carina; flexion of the head and neck causes a 2-cm descent of the tip of the tube, whereas extension of the head and neck causes a 2-cm ascent of the tip. In 90% of patients, the carina projects between the fifth and seventh thoracic vertebrae on the portable radiograph; when the carina cannot be clearly seen, the ideal positioning of the ETT is at the T2-T4 level. The aortic arch also may be used to estimate tube location because the carina is typically at the level of the undersurface of the aortic arch. If the ETT is too high, there is a risk of either inadvertent extubation or hypopharyngeal intubation, which can cause ineffective ventilation, gastric distention, or vocal cord injury. If the ETT is too low, selective intubation of the right mainstem bronchus may occur, resulting in segmental or complete collapse of the left lung, hyperinflation of the right lung, and possible pneumothorax (Figure 11–1). The balloon cuff should fill but not dilate the trachea. Cuff overinflation can cause tracheal injury, including tracheomalacia, tracheal stenosis, or acute tracheal rupture.
Right mainstem intubation. A. Placement of the endotracheal tube (arrow) into the right mainstem bronchus with resulting collapse of the left lung. B. Reexpansion of the left lung after retraction of the endotracheal tube.
Inadvertent placement of the ETT into the esophagus is uncommon but may be catastrophic when it does occur. Esophageal intubation may be difficult to diagnose on the portable chest film because the esophagus frequently projects over the tracheal air column. Gastric or distal esophageal distention, location of the tube lateral to the tracheal air column, and deviation of the trachea secondary to an overinflated intraesophageal balloon cuff are radiographic signs of esophageal intubation. The right posterior oblique view with the patient's head turned to the right allows ease of separation of the esophagus and trachea and can be obtained in equivocal cases.
Tracheostomy is typically performed in the patient who requires relatively long-term ventilatory support. The tip of the tracheostomy tube should be located at approximately one-half to two-thirds of the distance from the stoma to the carina, and unlike the ETT's position, the tracheostomy tube's position is not changed by extension or flexion of the patient's head. Although small amounts of subcutaneous emphysema and pneumomediastinum may be seen after an uncomplicated tracheostomy tube placement, significant emphysema may be a sign of tracheal perforation. Pneumothorax can occur after tracheostomy tube placement and may also be a sign of tracheal perforation. Late complications include tracheal stenosis, stomal infection, aspiration, tube occlusion, and development of a fistula between the trachea and esophagus, pleura, or mediastinum. The fistula is caused by erosion through the posterior tracheal membrane and usually occurs at the level of the tracheal cuff. If the fistula develops below the level of the cuff, gastric contents may be aspirated into the lungs. If the fistula develops above the level of the cuff, gastric contents may collect in the upper trachea.
CVCs are used frequently in the ICU patient for venous access, monitoring central venous pressure, and hemodialysis. The subclavian, internal jugular, and femoral veins are the sites of venous access used most commonly; smaller-caliber central catheters can also be peripherally inserted via antecubital veins. CVCs inserted via a thoracic vein are visible on the chest radiograph, and knowledge of normal thoracic venous anatomy is required to assess catheter location. The subclavian vein originates by the lateral aspect of the first rib and courses posterior to the clavicle, and anterior to the first rib. The internal jugular vein courses vertically in the neck; its convergence with the subclavian vein to form the brachiocephalic vein usually occurs behind the sternal end of the corresponding clavicle. Whereas the right brachiocephalic vein has a vertical course as it forms the superior vena cava, the left brachiocephalic vein crosses the mediastinum from left to right in a retrosternal position to enter the superior vena cava. The superior vena cava is formed by the junction of the right and left brachiocephalic veins at the level of the first anterior intercostal space, with its upper border usually just superior to the angle of the right mainstem bronchus and the trachea. On a chest radiograph, the junction of the superior vena cava and right atrium lies approximately 4 cm below the carina, or 1 to 2 cm below the superior right heart border. CVCs are optimally positioned when the tip within the superior vena cava, ideally slightly above the right atrium.
Appropriate catheter position must be verified radiographically, as malposition has been described in up to 40% of CVCs. Positioning of the catheter tip within the right atrium is common and may result in cardiac perforation and tamponade. Placement into the right ventricle may result in arrhythmias secondary to irritation of the endocardium or interventricular septum. A misplaced CVC may have its tip terminating in central systemic veins, which can result in inaccurate venous pressure readings as well as venous thrombosis or venous wall perforation. The most common location for a misplaced catheter entering the subclavian vein is the ipsilateral internal jugular vein. Less frequently, thoracic CVCs may enter the azygous, internal mammary, superior intercostal (Figure 11–2), thymic, left pericardiophrenic, or inferior thyroid veins. Looping, knotting, and kinking of the catheter may also occur (Figure 11–3), which can place mechanical stress on the vein and occasionally require removal by surgical or interventional radiology techniques.
Placement of central venous catheter in the left superior intercostal vein (red arrow).
Chest radiograph showing a central venous catheter forming a loop in the left brachiocephalic vein and terminating in the subclavian vein (arrow).
Other complications of central venous catheterization include pneumothorax, hemothorax, and perforation, which may result in pericardial effusion, hydrothorax, mediastinal hemorrhage, or ectopic infusion of intravenous solutions (Figure 11–4). Less common complications include air embolism and catheter fracture or embolism. Pneumothorax occurs in up to 5% of CVC insertions; the incidence of is higher with a subclavian approach than with an internal jugular approach. Pneumothorax may be clinically occult, and a chest radiograph should be obtained to exclude a pneumothorax following line placement. A radiograph should be obtained even following an unsuccessful attempted line placement.
Mediastinal hematoma following attempted central venous catheterization. A. Mediastinum appears unremarkable prior to catheter placement. B. Following attempted central line placement, there is widening of the superior mediastinum (arrows) secondary to mediastinal hemorrhage due to a lacerated subclavian artery. (Reproduced with permission from Bongard FS, Sue D, Vintch J: Current Diagnosis and Treatment Critical Care, 3rd edition. New York: McGraw-Hill Education; 2008.)
Venous air embolism is an uncommon complication of central venous catheterization. Radiographically, air in the main pulmonary artery is diagnostic, but other features include focal oligemia, pulmonary edema, and atelectasis. Intracardiac air or air within the pulmonary artery is seen easily on CT.
Long-term complications of venous access devices include delayed perforation, pinch-off syndrome, thrombosis, catheter knotting, and catheter fragmentation. Left-sided catheters have a greater risk for perforation, with increased risk in catheters abutting the right lateral wall of the superior vena cava. In pinch-off syndrome, the catheter lumen is compromised by compression between the clavicle and the first rib, leading to catheter malfunction and possible catheter fracture. This is frequently first observed as subtle focal narrowing of the catheter as it crosses the intersection of clavicle and rib.
Pulmonary Artery Catheters
The pulmonary artery catheter (PAC) plays an important role in the hemodynamic monitoring of the critically ill patient. The catheter is inserted via the subclavian or internal jugular vein and its tip should lie within the right or left main pulmonary artery. The catheter tip should remain within 2 cm of the hilum so that it does not extend beyond the proximal interlobar arteries. Complications related to CVC insertion, such as pneumothorax, vascular injury, infection, and knotting, kinking, or coiling of the catheter may also occur with PAC insertion. Ventricular arrhythmias are also common during PAC insertion, though usually self-limited. Another major complication is pulmonary infarction (Figure 11–5), usually caused by peripheral migration and occlusion of the vascular lumen by the catheter, or by continuous wedging of the inflated balloon in a central pulmonary artery. The radiographic appearance of pulmonary infarction secondary to a PAC is similar to that of infarction from other causes and consists of a wedge-shaped parenchymal opacity seen in the distribution of the vessel distal to the catheter. Management consists of removal of the catheter. Anticoagulation is generally not required, and resolution of consolidation usually occurs in 2 to 4 weeks.
Lung infarction secondary to pulmonary artery catheterization. A. Initial radiograph after catheterization shows the tip of the catheter at the level of the right interlobar pulmonary artery (arrows). Mild redundancy of the catheter is present within the dilated heart. B. At 24 hours, the patient developed hemoptysis. Radiograph now shows migration of the catheter into a segmental arterial branch (arrows) with increased density in the right lower lobe. C. Follow-up film demonstrates dense consolidation of the right middle and lower lobes secondary to infarction. (Reproduced with permission from Aberle DA, Brown K: Radiologic considerations in the adult respiratory distress syndrome, Clin Chest Med. 1990 Dec;11(4):737-754.)
Pulmonary artery rupture is a catastrophic complication of pulmonary artery catheterization, with a reported mortality rate of 46%. The incidence is low—no more than 0.2% of catheter placements. Risk factors include pulmonary hypertension, advanced age, and improper balloon location or inflation. The mortality rate increases in anticoagulated patients. Pseudoaneurysm formation has been reported secondary to rupture or dissection by the balloon catheter tip. This appears radiographically as a well-defined nodule at the site of the aneurysm, but it may be obscured initially by extravasation of blood into the adjacent air spaces. Chest radiographic findings often precede clinical manifestations, and death due to rupture of pseudoaneurysm may occur weeks following catheterization. The CT appearance of a pulmonary artery pseudoaneurysm has been described as a sharply defined nodule with a surrounding halo of faint parenchymal density. Pulmonary artery pseudoaneurysm now may be treated in some patients with transcatheter embolization rather than surgical resection.
Intra-Aortic Balloon Counterpulsation
Intra-aortic balloon counterpulsation is used to improve cardiac function in patients with cardiogenic shock and in the perioperative period in cardiac surgery patients. The device consists of a fusiform inflatable balloon surrounding the distal portion of a catheter that is placed percutaneously from a femoral artery into the proximal descending thoracic aorta. The balloon is inflated during diastole, thereby increasing diastolic pressure in the proximal aorta and increasing coronary artery perfusion. During systole, the balloon is forcibly deflated, allowing aortic blood to move distally and decreasing the afterload against which the left ventricle must contract, thus decreasing left ventricular workload. The tip of the balloon ideally should be positioned just distal to the origin of the left subclavian artery at the level of the aortic knob (Figure 11–6). Complications occur in 8% to 36% of intra-aortic balloon pump (IABP) placements and are most often secondary to malpositioning of the catheter. Overadvancement of the catheter may cause occlusion of the left subclavian artery, resulting in arm ischemia, or obstruction of the left common carotid or left vertebral arteries, causing cerebral ischemia. Caudal placement of the catheter can obstruct renal or mesenteric arterial flow. Aortic dissection has been reported in 1% to 4% of IABP catheter insertions, and an indistinct aorta on chest radiographs has been suggested as an early clue to intramural location, requiring confirmation by angiography. Balloon leak or rupture with gas embolization has also been described as an extremely rare but potentially fatal complication.
Intra-aortic balloon pump positioned in the proximal descending thoracic aorta (red arrow). A pulmonary artery catheter is also seen with its tip located in the right main pulmonary artery (black arrow).
Cardiac Pacemakers and Automatic Implantable Cardioverter-Defibrillators
Cardiac pacemakers can be inserted by 3 approaches: transvenous, epicardial, and subxiphoid. Most often the transvenous approach is used, whereby an introducer sheath is used to establish central venous access and allow for insertion of the pacing wire, which is then guided into the right ventricle under electrocardiogram (ECG), ultrasound, or fluoroscopic guidance. The right internal jugular and the left subclavian veins are often preferred, as these routes take advantage of the natural curve of the pacing catheter, allowing for smoother, more direct placement of the wire.
When viewed on a chest radiograph, the pacemaker lead should terminate in the right ventricular apex, slightly to the left of the thoracic spine and at the anterior-inferior aspect of the cardiac shadow. A lateral view can be obtained to confirm that the catheter courses anteriorly to the right ventricle if proper placement is in question. The pacemaker lead should curve gently throughout its course, as regions of sharp angulation will have increased mechanical stress and enhance the likelihood of lead fracture. Excessive lead length can result in myocardial perforation, causing hemopericardium and cardiac tamponade. Shorter leads can become dislodged and enter the right atrium. Leads also may become displaced and enter the pulmonary artery, coronary sinus, or inferior vena cava. Other complications include venous thrombosis or infection, either at the pulse generator pocket or within the vein.
Nasogastric tubes are used frequently to provide nutrition and administer oral medications as well as for suctioning gastric contents. Ideally, the tip of the tube should be positioned at least 10 cm beyond the gastroesophageal junction. This ensures that all side holes are located within the stomach and decreases the risk of aspiration.
Small-bore flexible feeding tubes have been developed to facilitate insertion and improve patient comfort. However, inadvertent passage of the nasogastric tube into the tracheobronchial tree is not uncommon, most often occurring in the sedated or neurologically impaired patient. In patients with endotracheal tubes in place, low-pressure, high-volume balloon cuffs do not prevent passage of a feeding tube into the lower airway. If sufficient feeding tube length is inserted, the tube actually may traverse the lung and penetrate the visceral pleura (Figure 11–7). Removal of the tube from an intrapleural location may result in tension pneumothorax, and preparations should be made for potential emergent thoracostomy tube placement at the time of removal. Other complications of nasogastric intubation include esophagitis, stricture, and, rarely, rupture of the pharynx, esophagus, or stomach.
Malpositioned feeding tube. A. Feeding tube courses via the right mainstem bronchus with the tip (arrow) overlying the right costophrenic angle. An endotracheal tube is present. B. Following removal of the feeding tube, a pneumothorax is seen (arrow). (Reproduced with permission from Bongard FS, Sue D, Vintch J:urrent Diagnosis and Treatment Critical Care, 3rd edition. New York: McGraw-Hill Education; 2008.)
In addition to feeding tubes, balloon tamponade tubes occasionally are used for nasogastric intubation in the treatment of bleeding esophageal and gastric varices. The balloon can be easily recognized when distended, and correct positioning can be evaluated radiographically (Figure 11–8). Esophageal rupture complicates approximately 5% of cases in which balloon tamponade tubes are used.
An abdominal radiograph showing placement of a Blakemore tube. The distal (gastric) balloon has been inflated.
Thoracostomy tubes (“chest tubes”) are used for the evacuation of air or fluid from the pleural space. When chest tubes are used for relief of pneumothorax (Figure 11–9), apical location of the tip of the tube is most effective, whereas a tube inserted to drain free-flowing effusions should be placed in the dependent portion of the thorax. Chest radiographs, ultrasound, or CT should be used to guide correct placement of the tube for adequate drainage of a loculated effusion. Failure of the chest tube to decrease the pneumothorax or the effusion within several hours should arouse suspicion of a malpositioned tube. Tubes located within the pleural fissures are usually less effective in evacuating air or fluid collections. An interfissural location is suggested by orientation of the tube along the plane of the fissure on frontal radiographs and by lack of a gentle curvature near the site of penetration of the pleura, indicating failure of the tube to be deflected anteriorly or posteriorly in the pleural space. The lateral view may be confirmatory. Uncommonly, thoracostomy tubes may penetrate the lung, resulting in pulmonary laceration and bronchopleural fistula. Unilateral pulmonary edema may occur following rapid evacuation of a pneumothorax or pleural effusion that is of long standing or has produced significant compression atelectasis of lung.
Pneumothorax. A. Development of a right-sided pneumothorax (black arrows) after placement of a subclavian central venous catheter (CVC). B. Reexpansion of the right lung after placement of a chest tube (red arrow).