Postprocedural chest radiograph: Impact on the management in critical care unit.

Postprocedural chest radiograph is done to illustrate the position of endotracheal tubes (ETTs), nasogastric and drainage tubes, indwelling catheters, and intravascular lines or any other lifesaving devices to confirm their position. These devices are intended to save life, but may be life-threatening if in the wrong place. The incidence of malposition and complications ranges from 3% to 14%, respectively. The portable chest radiograph is of tremendous value, inexpensive and can be obtained quickly at the patient's bedside in any location of the hospital. A systemic literature search was performed in PubMed and the Cochranre library by setting up the search using either single text word or combinations. Those studies were also included where the chest radiograph was compared with other imaging modalities. Its clinical efficacy, cost-effectiveness and practicality allow anesthesiologist to evaluate the post-procedural position and complications of ETT, indwelling catheters, and multi lumen intravascular lines. Knowledge of the radiological features of commonly used devices is of utmost importance.

INTRODUCTION

Chest imaging is an important component in diagnostic evaluation and assessment of prognosis of critically ill patients and chest radiograph plays a crucial role for evaluation of position of various tubes, lines, and other lifesaving devices by detecting the procedure related complications and pathological changes of exiting pulmonary disease.[1] These endotracheal tubes (ETTs), nasogastric tubes, indwelling catheters and intravascular lines do have the potential risk of coiling, misplacement, knotting, and fracture. Immediate postprocedural chest radiograph is recommended to check the position and to detect procedure related complications.[2] Bekemeyer et al. concluded that 27% of newly placed catheters or tubes were improperly positioned and 6% resulted in a radiological visible complication of the procedure. Although, many such abnormalities may not be immediately life-threatening but some require rapid correction to avoid clinical deterioration of critical ill patient with marginal cardiorespiratory reserve.[3]

Bedside chest radiographs are obtained in supine and semi-upright positions with the patient's back closest to the film cassette and the X-ray beam directed in the anterior to posterior direction. The part of the chest closest to the film cassette is the least magnified; therefore the cardiac silhouette is larger on the anterior-posterior (AP) projection. On an adequate inspiratory film, the hemi diaphragms are below the anterior end of the sixth rib or at least below the 10th posterior rib and lung expansion should be symmetrical.[4] Interpretation of bedside chest radiograph can be quite challenging because of the degree of variations in quality due to the ill-health of patient and multiple cumbersome life support devices limit proper positioning. Difficulty in controlling respiration and body motions also blur the chest radiograph, whereas the details of internal objects are masked by the shadows of overlying and underlying structures. Chest radiograph can still afford a composite survey of the chest at one quick glance regarding the post procedural position of ETT, Ryle's tube (RT), central venous catheter, pulmonary artery catheter and other lifesaving devices.[567]

It is important to understand the function of different tubes and intravascular lines as well as to recognize their normal and complications associated with its use. Here, we will now discuss the commonly used tubes and lines of intensive care unit.

NASOGASTRIC TUBE OR RYLE'S TUBE

The nasogastric tubes are used for gastric decompression or lavage, medication administration and to provide nutrition and hence the tip of nasogastric tube should lie with its side holes in the gastric antrum. These tubes are inserted through the nostrils and advanced into the stomach or duodenum. The length of the tube, must be advanced to reach the stomach, can be estimated by measuring the distance from the tip of the nose to the earlobe and then to the xiphoid process (approximately 50-60 cm). There are terminal lead balls to facilitate the identification of the tip on chest radiograph. When nasogastric tube is in place, it should more or less course inferiorly and to the left, toward the fundus of the stomach in the left upper quadrant. Pushing the air into the RT, while auscultating with a stethoscope over the stomach is the usual method to confirmed, its correct poisoning in stomach [Figure 1].

Figure 1

Normally positioned naso-gastric tube

The most common complication from insertion of enteric tube is the coiling in the pharynx or esophagus. If the side holes are positioned within the esophagus, there is increased risk of aspiration; hence, the tip of RT should be at least 10 cm caudal to location of the gastroesophageal junction. The inadvertent insertion into the trachea or bronchial tree occurs in 0.2-0.3% patients and can cause pneumonia, pulmonary contusion, or pulmonary laceration. Rarely, pharyngeal and esophageal perforations can occur with serious consequences [Figure 2].[89]

Figure 2

Abnormally placed Naso-gastric tube showing the tip in the left bronchial tree, x-ray showing pleural effusion and consolidation left side

ENDOTRACHEAL TUBE

The ETT is used to ventilate the patient. On the chest radiograph, position of an ETT is determined by the location of its tip in relation to the carina. The position of tip of ETT should be 5-7 cm above the carina in the neutral position of neck. When the carina is not visible, the tip of the ET tube should lie over the second to fourth thoracic vertebrae (T2-T4) or at the level of medial ends of the clavicles as carina is located between T5 and T7. The location can vary approximately 2 cm in the caudal or cephalic directions with neck flexion and extension, respectively on chest radiograph. Projection of anterior portion of the mandible over the lower cervical spine indicates neck flexion whereas a non-obscured cervical spine denotes that the neck is in extension. The tip should lie midway between the larynx and carina to avoid injury to any structure, inadvertent extubation or bronchial intubation [Figure 3].

Figure 3

Normally positioned endotracheal tube above the carina

The most common complication of ETT placement is inadvertent intubation of the right main bronchus because of the smaller angle of right main bronchus in relation to trachea [Figure 4]. Selective intubation can cause collapse of the contralateral lung, hyperinflation of the ipsilateral lung, or pneumothorax. Inadvertent esophageal intubation is a dreadful complication and mostly diagnosed clinically. Tracheal stenosis can occur following long-term ET tube placement.

Figure 4

Malpositioned Endo-tracheal tube showing in right main bronchus. Left lung shows consolidation

TRACHEOSTOMY TUBE

The tracheostomy tube (TT) is required in patients who need long-term assisted ventilation, tracheal suction or where oral or nasal tracheal intubation is not possible. The tip of TT should lay half way between the stoma and the carina, at the level of the T3 vertebra. Unlike with ETT, chin position does not affect the position of TT and its position is maintained with neck flexion and extension. The diameter of the TT should be 2/3rd of the tracheal width, and it should lie parallel to the trachea. Its cuff should not distend the tracheal wall [Figure 5].

Figure 5

Normally positioned tracheostmy tube above the carina

The presence of air in the subcutaneous tissue of the neck and upper mediastinum is usually an insignificant finding immediately after TT placement. The potential complications of TT placement are pneumothorax, surgical emphysema, pneumo-mediastinum and mediastinal hematoma and can be identified on post procedural chest radiograph as a widened superior mediastinum. The other possible complications are of false tract and tracheal stenosis.

INTERCOSTAL DRAINAGE TUBES

The intercostal drainage (ICD) tube is inserted through the 4th intercostal space in the anterior or mid-axillary line, directed posterior-inferiorly in cases of pleural effusion and antero-superiorly in case of pneumothorax. The ICD tube has a terminal hole as well as side holes. These side holes can be identified on Chest radiograph by the interruption in the radiopaque outline of the tube. No side holes should lie outside the chest or pleura and the tube should not float above the effusion.

ICD tube malposition occurs in about 10% of placements, rendering the tube malfunctioning or non-functioning. Occasionally, the tube tip may lie in the subcutaneous soft tissue, in inter lobar pulmonary fissure or rarely even within the lung parenchyma. Poor positioning of the thoracic tube is suspected when the tube does not drain as expected. Both AP and lateral views of chest radiograph are necessary to ensure proper positioning of ICD [Figures 6-8].

Figure 6

Chest x-ray showing malpositioned intercostal drainage tube in a case of pneumo-thorax with collapse on right side

Figure 8

Chest X-ray showing malpositioned intercostal drainage tube in a case of hydro-pneumothorax on the left side

Chest x-ray showing malpositioned intercostal drainage tube in a case of pleural effusion on left side

Mediastinal drains are usually inserted following sternostomy and resemble pleural tubes in all respects, except for their position.

CENTRAL VENOUS CATHETER

Central venous catheter placement is increasingly done in surgical and critically ill patients for hemodynamic pressure monitoring, hemodialysis, administration of medications, volume expansion and parenteral nutrition. They provide long term venous access. Central venous catheters are inserted through major veins such as the subclavian, internal jugular, or femoral veins to reach the superior vena cava (SVC). The tip of the line should be distal to last venous valve, which is located at the junction of internal jugular and subclavian veins. The preferred position of the catheter tip is in the distal third of the SVC to minimize complications of catheter migration, extravasation of irritant agents, vascular perforation, local vein thrombosis, catheter malfunction and cranial retrograde injection [Figure 3].

On the chest radiograph, the first anterior intercostal space corresponds to the approximate site of the junction of the brachiocephalic veins to form the SVC and the cavoatrial junction corresponds to the lower border of bronchus intermedius. The position of valve corresponds to the inner aspect of the first rib.

The right internal jugular vein is preferred for placement with success rate of 90-99% with fewer complications. The route via the internal jugular vein has the lowest incidence of misdirection. Complications vary with the type of line and the site of insertion. In about 30% of cases the initial radiographs show a malposition central venous line. Pneumothorax occurs in up to 6% of procedures and is more common with subclavian approach. If the central venous line tip touches the venous wall there is a risk of vessel perforation with resultant infusion of fluid into the mediastinum, pleural or pericardial space. This complication will appear as mediastinal widening, enlargement of cardiac silhouette or a new pleural effusion on chest radiograph.[1011]

Abnormal course or mal-positioning of a central venous catheter occurs when it enters a tributary such as the azygos vein, subclavian vein, internal mammary vein or an anomalous vein. It may even enter the carotid vessels.[12]

Stonelake et al. suggested three different zones for safe central venous catheter placement. According to them, Zone-A represents lower SVC and upper right atrium, safe for all left sided internal jugular venous catheter tip placement, Zone-B represents upper SVC and area around the junction of both innominate veins, safe for all right sided central venous catheter (CVC) placement and Zone-C represents the left innominate vein proximal to the SVC, should be used for central venous pressure monitoring and fluid therapy. A brief review of the literature suggested that the CVC tip in the SVC above the level of the carina, a radiological landmark, is ideal and safe.[13]

Though ultrasound has reduced some of the complications during its insertion, but cannot locate the catheter tip in relation to heart. Only transesophageal echocardiography can accurately detect a CVC tip in relation to SVC and right atrium, but its availability as a bedside is limited, so we routinely perform a post procedural chest radiograph to confirm its position.

PULMONARY ARTERY (SWAN-GANZ) CATHETER

The pulmonary artery catheter is a flow directed balloon tipped and is widely used for monitoring circulatory hemodynamic for the management of critical illness. The balloon is inflated to measure the pulmonary artery pressure and capillary wedge pressure. The balloon should not be overinflated to avoid rupture of the pulmonary artery. To measure pulmonary capillary wedge pressure, the tip of catheter needs to be in the right or left pulmonary artery and 1 cm lateral to the mediastinal margin. The catheter tip should not extend beyond the pulmonary hilum on the chest radiograph to avoid complications. If the tip extends beyond these larger arteries, pulmonary infraction from occlusion of the pulmonary vessel or pseudo-aneurysm can occur.[14]

Other potential complications are intra-cardiac knotting, pulmonary infection and thromboembolism, pulmonary artery perforation, arrhythmias, cardiac perforation and placement in inferior vena cava. The complication rate of pulmonary infraction can be reduced if balloon is inflated only during pressure measurement and insertion.

INTRA-AORTIC BALLOON PUMP

Intra-aortic balloon pump (IABP) is a long-balloon temporary circulatory assist device and works on the principle of cardiac counter pulsation. The IABP is used to assist the left ventricular function in patients with cardiac shock or serious left ventricular dysfunction to support the circulation. The 25 cm long balloon is mounted on a catheter tip, visible as a 3 mm × 4 mm rectangular metallic density on chest radiograph while rest of the catheter is radiolucent. The catheter is inserted through the femoral artery and balloon is inflated with gas during diastole and deflates during systole, resulting in increase in coronary blood flow and reduction in left ventricular afterload. The indications of IABP placement are acute myocardial infraction with cardiogenic shock, postcoronary artery bypass graft, acute mitral insufficiency, and cardiac transplantation and is contraindicated in aortic regurgitation, aortic dissection and in the presence of a prostatic graft in the thoracic aorta.

On chest radiograph, the tip of the balloon should be located within the descending thoracic aorta just distal to the origin of the left subclavian artery, generally at the level of aortic arch. A more proximal location of the balloon can result in occlusion of the subclavian and vertebral arteries, whereas a more distal location can lead to occlusion of the mesenteric and renal arteries. To avoid occlusion of the left subclavian artery and visceral and renal arteries, its tip should be slightly cephalad to the adjacent carina in the 2–3rd intercostal space. The balloon should not occlude more than 85–90% of the aortic diameter. IABP can migrate, so position should be reassessed on subsequent chest radiograph. Potential but rare complications are balloon rupture with air embolization and septicaemia.

Pacemaker

Pace makers are used in cases of severe sinus node dysfunction, complete heart block and various other arrhythmias. They have two main components; a pulse generator and a lead wire with electrodes. The single lead pacemaker is the most basic type and is positioned with its tip in the right ventricular apex. An atrioventricular two-lead sequential pacemaker has one electrode in the right atrium and the other at the right ventricular apex. Sometimes a third lead is placed in the coronary sinus to pace the left ventricle. It is not feasible to insert an electrode in the left side of heart due to high pressure in these chambers.

A lateral chest radiograph is usually required to confirm the position of the electrode in the right arterial appendage. The tip points anteriorly when correctly placed or may bends as it abuts the wall. The usual complications are malposition, intra-cardiac knotting, fracture, perforation, cardiac tamponade, arrhythmias, infection, and hemorrhage. Rarely twisting of the lead can occur either due to the patient's manipulation or spontaneously itself [Figure 9].

Figure 9

Two lead sequential pace maker with lead in the right atrium and right ventricle and one lead shows fracture

AUTOMATED IMPLANTABLE CARDIOVERTER DEFIBRILLATOR

Automated implantable cardioverter defibrillator is used in cases of recurrent refractory ventricular tachyarrhythmias. It has two electrodes, one electrode is placed in the right atrium and the other is placed in the right ventricle. The lead is wider compared to the pacemakers and has a coiled spring appearance. It senses ventricular tachycardia or fibrillation and responds with countershocks to the heart. The incidence of complications are 20% and similar to those with trans-venous pacemakers.

CONCLUSION

Postprocedural chest radiograph is a cost efficient examination to assess the position and monitor the complications of different tubes, intravascular lines, indwelling catheters and other lifesaving devices in critically ill patients at one quick glance and hence considered to be gold standard imaging modality in intensive care units.