Chapter 11 Intensive Care Unit

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SECTION 1 • Techniques and Methods in Critical Care

45-degree bisecting line, which passes through the middle of the aortic knob.) ET tubes move with flex- ion, extension, and rotation of the neck. Contrary to what might be expected, the tube tip moves cau- dally when the neck is flexed (i.e., chin down = tip down). Conversely, head rotation away from the midline and neck extension elevates the ET tube tip. Total tip excursion may be as much as 4 cm. The normal ET or tracheostomy tube should occupy one half to two thirds of the tracheal width and should not cause bulging of the trachea in the region of the tube cuff. Bulging is associated with an increased risk of subsequent airway stenosis, pre- sumably the result of tracheal wall ischemia from cuff overinflation. Gradual dilation of the trachea may occur during long-term positive pressure ven- tilation, but every effort should be made to prevent this complication by minimizing both ventilator cycling pressure and cuff sealing pressures. After tracheostomy, a CXR may detect subcu- taneous air, pneumothorax, pneumomediastinum, or malposition of the tube. The T3 vertebral level defines the ideal position of the tracheostomy site. (This usually places the tip halfway between the stoma and the carina.) Unlike the orally placed ET tube, the tracheostomy tube does not change posi- tion with neck flexion or extension. Lateral radio- graphs are necessary for evaluation of anteroposterior angulation. Sharp anterior angulation of the tracheal tube is associated with the development of tracheo- innominate fistulas, whereas continued posterior angulation risks erosion and tracheoesophageal fis- tula. Massive hemoptysis usually signals the former condition, whereas sudden massive gastric disten- tion with air occurs in the latter. Fortunately, both complications are quite rare in modern practice. In patients with previous intubation or trache- ostomy, the tracheal air column should be exam- ined for evidence of stenosis. Tracheal narrowing is relatively common and can occur at the level of the tracheal tube tip, at the cuff, or at the tracheostomy tube stoma (most common site). The typical hour- glass-shaped narrowing can be hard to visualize on a single AP radiograph, and stenosis must be substan- tial (luminal opening <4 mm) to be symptomatic. CT establishes a definitive diagnosis. Central Venous Catheters For accurate pressure measurement, the tip of the CVC should lie within the thorax, well beyond any venous valves. These valves are typically located in the

subclavian and jugular veins, approximately 2.5 cm from their junctions with the brachiocephalic trunk (at the radiographic level of the anterior first rib). Because CVC catheters in the right atrium or ven- tricle may cause arrhythmias or perforation, the desir- able location for these lines is in the midsuperior vena cava, with the tip directed inferiorly. Radiographically, catheter tips positioned above the superior mar- gin of the right mainstem bronchus are unlikely to rest in the atrium. Catheters should have no sharp bends along their course and should descend lateral and parallel to the spine. Stiff catheters, particularly hemodialysis lines inserted through the left subcla- vian vein may impinge on the lateral wall of superior vena cava, potentially resulting in vascular perfora- tion. Complications resulting from vascular puncture include air embolism, fluid infusion into the pericar- dium or pleural space, hemopneumothorax, and peri- cardial tamponade. Imaging studies reveal that partial thrombosis occurs distressingly often with CVCs and peripherally inserted central catheters (PICC lines). Postprocedure radiographs reveal complications in up to 15% of CVC placements. On occasion, cath- eters inserted via the subclavian route can pass across the midline into the contralateral subclavian vein, or even turn cephalad entering the internal jugular veins. Similarly, catheters inserted in the internal jugular veins may track into the subclavian vein of either side. The phenomenon of a subclavian catheter crossing the midline is most common when a triple-lumen catheter is threaded through a larger bore channel already in placed in the right subclavian vein. Many clinicians are comfortable leaving CVCs, which ter- minate in the contralateral subclavian in place, pro- vided there are no clinical effects but are less at ease with CVCs terminating in the internal jugular vein. As a general rule, it is a good idea to obtain a CXR following failed attempts at CVC placement before attempting insertion on the contralateral side. Doing so reduces the already tiny chance of producing bilateral pneumothoraces. Obviously, this safeguard must be abandoned under truly emergent circumstances where venous access must be obtained immediately. Pulmonary Artery (Swan–Ganz) Catheter Every insertion-related complication of CVCs, including pneumothorax, pleural entry, and arterial injury, can result from the placement of the pulmo- nary artery catheter (PAC) as well. Unique complica- tions of PAC placement include knotting or looping