106 e1 Pulmonary Artery Catheter Information Acquisition and Interpretation Much hemodynamic and Do2 information can be obtained from the Swan Ganz–type PAC Multiple hemodynamic pressures can be obtai[.]
106.e1 Pulmonary Artery Catheter Information Acquisition and Interpretation Much hemodynamic and Do2 information can be obtained from the Swan-Ganz–type PAC Multiple hemodynamic pressures can be obtained, including RA, RV PA, and PAWP RA pressure is useful for determining preload of the RV Pulmonary artery pressure is useful for determining the presence of pulmonary hypertension both at baseline and with manipulation of oxygenation, ventilation, ventilator pressures, inhaled nitric oxide, and other procedures PAWP reflects left ventricular preload In most patients with normal cardiac function and anatomy, right atrial or central venous pressure adequately reflects LV preload as well However, in the presence of certain congenital heart defects, with significant ventricular dysfunction, or with high mechanical ventilatory pressures, a significant discrepancy may exist between right and left ventricular preload In such circumstances, measurement of PAWP may be useful for guiding fluid and inotropic therapy Mixed venous oxygen saturation (Svo2) can be determined directly and continuously with a catheter containing the fiberoptic oximeter In the absence of the oximeter, intermittent blood sampling from the distal port when in place in the PA allows for Svo2 measurement The thermistor at the tip of the catheter allows for measurement of cardiac output using the thermodilution method This method uses the Fick principle, based on the law of conservation of thermal energy A specific amount of known temperature fluid is injected in the proximal port (upstream), and the temperature change downstream (at the thermistor) is recorded The change in temperature over time allows for measurement of blood flow—in this case, cardiac output According to Jansen, this measure of cardiac output is accurate if the following conditions are met: (1) no loss of cold occurs between the injection site and the thermistor, (2) mixing of the cold injectate (indicator using Fick terms) and the blood is complete, and (3) the temperature change caused by the injection of cold fluid is sufficient to be detected by the thermistor To perform thermodilution cardiac output measurements, the catheter must be connected to the thermodilution computer, which is either freestanding or part of the cardiac monitor A specific volume of injectate, either room temperature or iced, is injected rapidly into the proximal port of the catheter The temperature difference over time that is detected at the thermistor is recorded as a curve The computer then integrates the area under the curve, which is inversely proportional to the cardiac output The cardiac output is calculated and projected For children, this number should be divided by their body surface area in square meters, deriving the cardiac index The injectate can be either iced or room temperature Although a greater signal-to-noise measurement is obtained, the disadvantages of iced injectate include risk of hypothermia in pediatric patients requiring frequent cardiac output measurements and the poor accuracy of the first injection because of warmer fluid in the catheter In conditions of high or low cardiac output, less variance occurs with iced injectate compared with room-temperature injectate However, for convenience and the safety of pediatric patients, room-temperature injectate is generally recommended Usually, three to five injections yield adequate results Some error can be introduced by faulty technique Injecting variable volumes or injecting with variable rates can result in inaccurate measures Multiple injections and averaging of the results can overcome these problems The presence of tricuspid or pulmonary insufficiency can lead to an overestimation of cardiac output Echocardiography may be necessary to rule out the presence of valvular insufficiency Intracardiac shunts, such as a ventricular septal defect, result in false values for cardiac output Mechanical ventilation has been shown to alter stroke volume, which can result in a variability of cardiac output measurements Therefore, one should perform the injection at the same time in the ventilator cycle to standardize the cardiac output measurements CHAPTER 14 Pediatric Vascular Access and Centeses remove and then replace the catheter if it is still clinically indicated As noted earlier, arrhythmias can occur, particularly if the catheter becomes dislodged A chest radiograph should be taken daily to assess for catheter position Complications PA catheterization is a significantly invasive procedure Complications can occur during the Seldinger procedure to access the vein, during the passage of the PAC (across two heart valves), or during catheter use Bleeding, infection, and pneumothorax may occur during venous access Arrhythmias can be encountered during placement of the PAC or due to dislodgment of the catheter Arrhythmias include supraventricular tachycardia while the PAC tip is in the RA to premature ventricular beats or even ventricular tachycardia while the PAC tip is in the RV Usually, the arrhythmias cease when the PAC tip reaches the pulmonary artery Lidocaine, amiodarone, and defibrillation may be needed on occasion for ventricular arrhythmias; thus, these drugs should be readily available Once the catheter is in place, pulmonary infarction or hemorrhage is a risk Rupture of the distal PA, endothelial damage, and valvular damage have been reported, as well as knotting of the catheter requiring fluoroscopic retrieval The PAC should be removed as soon as possible to minimize the risk of complications Summary Since the introduction of the PAC, controversy has surrounded the technology regarding the benefits and potential harms caused by this invasive form of hemodynamic monitoring In adult clinical trials, the usefulness of the PAC has been challenged because no benefit in patient outcome has been observed, and some retrospective studies have described worse outcomes Accurate acquisition and interpretation of PAC data are paramount for making appropriate therapeutic decisions Thoracentesis Thoracentesis is a procedure used to remove abnormal accumulations of nonphysiologic substances from within the potential space of the pleura, including fluid (hydrothorax), blood (hemothorax), air (pneumothorax), or pus (empyema) Pleural effusions in children are most commonly the result of an infectious process (50%–70% are parapneumonic effusions), with congestive heart failure and malignancy being less common causes.124–126 Volume resuscitation with third spacing after shock is also a cause of pleural effusions in the PICU There are many other pathologic causes of pleural effusions in children (eBox 14.2) Indications Thoracentesis may be used diagnostically for new fluid accumulations or therapeutically to relieve cardiopulmonary compromise resulting from large accumulations of fluids or air New and particularly persistent pleural fluid collections should be investigated with diagnostic thoracentesis If ongoing evacuation is required, tube thoracostomy should be considered (discussed later in this chapter) Ultrasound is useful to identify fluid accumulations when there is complete opacification of the hemithorax on chest radiograph and helps characterize fluid consistency to determine whether it is a complicated, loculated, or simple, free-flowing 107 effusion Ultrasound also helps identify optimal locations for successful aspiration and has decreased complication rates.127–131 Ultrasound is almost universally used by interventional radiologists for thoracentesis and tube thoracostomy and is increasingly used by pediatric intensivists Adult data have shown a decrease in complications with bedside ultrasound for thoracentesis, but similar data for children are lacking Contraindications Thoracentesis has few to no absolute contraindications Relative contraindications include insufficient amount of pleural fluid and severe bleeding diatheses Uncorrected coagulopathy and thrombocytopenia may predispose to bleeding complications; however, thoracentesis can generally be accomplished in this setting using a small needle and careful technique Skin infections or wounds at the insertion site can lead to introduction of new infection into the pleural space and thus should be avoided Presence of positivepressure ventilation may increase the risk of pneumothorax However, the risk is low and should not serve as a contraindication to a medically necessary procedure.127,129 An uncooperative patient can lead to damage of the underlying vascular structures and lung parenchyma This risk can be mitigated by appropriate sedation and analgesia Preparation Sedation and analgesia are frequently required to safely perform thoracentesis in pediatric patients Topical anesthetic agents reduce the discomfort associated with infiltration of local anesthetics and should be placed on the predetermined insertion site at least 30 minutes prior to the procedure (depending on the topical agent) Technique If thoracentesis is being performed for evacuation of a pneumothorax, the patient should be placed in the supine position and needle aspiration should be performed perpendicularly to the chest wall at the second intercostal space (along the superior border of the third rib) in the midclavicular line For removal of pleural fluid, the patient should be placed in the upright, seated position, while infants and young children may be held in burping position by an assistant Mechanically ventilated patients should be in partial decubitus position with the fluid-containing side down, in a dependent position The usual site for fluid aspiration is the seventh intercostal space in the posterior axillary line (near the tip of the scapula) However, realtime bedside ultrasonography should be used to identify pleural fluid, ideal puncture site, and planned trajectory for the needle path Once determined, the patient should be maintained in the same position, and the site should be marked with a skin indentation from a needle cap or sterile site marker Aseptic technique should be observed throughout the procedure The site is prepped with 2% chlorhexidine or 10% povidone-iodine and draped with sterile towels The skin entry site is then generously infiltrated with a local anesthetic using a 27- to 30-gauge needle to create a wheal of fluid just under the skin The needle is then advanced through this wheal, perpendicular to the skin to infiltrate the underlying subcutaneous tissues, superior portion of the rib, and periosteum, always aspirating prior to instilling the anesthetic Care must be taken not to exceed maximal drug dosages for weight to 107.e1 The hemodynamic data obtained or calculated with the PAC should be interpreted to make therapeutic decisions There are not isolated “good” or “bad” cardiac output values, but appropriate cardiac output is that which permits an adequate Do2 As a global index of adequacy between consumption and Do2, Svo2 is the target of choice for therapeutic decisions Svo2 should be kept above a threshold value between 65% and 70%, and all other PAC parameters should be used to choose how to maintain Svo2 above this value This Svo2 goal can be achieved by fluid administration, blood transfusion, increasing or decreasing inotropic support, or vasopressors.118,123 • eBOX 14.2 Causes of Pleural Effusion in Children Infectious (Exudates) Collagen Vascular Disease • • • • • • • • • • Bacterial Viral Fungal Mycobacterial (tuberculous and nontuberculous) Parasitic Rheumatoid pleurisy Lupus pleuritis Churg-Strauss syndrome Sjögren syndrome Granulomatosis with polyangiitis (formerly Wegener granulomatosis) Cardiovascular (Transudates) Neoplastic • • • • • • • • • Congestive heart failure Constrictive pericarditis Postcardiac surgery Superior vena cava obstruction (SVC syndrome) Pulmonary • • • • • • Pulmonary infarction Atelectasis Pulmonary embolism Pulmonary sequestration Asbestosis Trapped lung Intraabdominal Disease • • • • • • • • • Post–abdominal surgery Pancreatitis Hepatitis Peritonitis Subdiaphragmatic abscess Hepatic abscess Splenic abscess Meigs syndrome Cirrhosis with ascites Iatrogenic • Drug-induced pleuritis • Enteral feeding tube misplacement • Extravascular central venous catheter placement Lymphoma/leukemia Mesothelioma Chest wall tumors Carcinomas Neuroblastoma Renal • • • • Uremia Urinary tract obstruction Nephrotic syndrome Peritoneal dialysis Miscellaneous • • • • • • • • • • • • Esophageal rupture Traumatic hemothorax Chylothorax (post–thoracic surgery or congenital) Hydrops fetalis Lymphedema Lymphangiectasia Hypoalbuminemia Hypothyroidism with myxedema Sarcoidosis Post–radiation therapy Immunoblastic lymphadenopathy Familial Mediterranean fever 108 S E C T I O N I I Pediatric Critical Care: Tools and Procedures avoid iatrogenic complications depending on the local anesthetic used (e.g., maximum of mg/kg of 1% lidocaine without epinephrine or mg/kg lidocaine with epinephrine) The needle is then advanced over the superior border of the rib while gently aspirating until the pleural space is reached An over-the-needle catheter of sufficient length can be used for aspiration of fluid with a syringe If infection or viscous exudate is suspected, a larger catheter (16- to 18-gauge) may be required Aspiration is continued until a sufficient quantity of fluid for planned diagnostic studies is obtained A three-way stopcock with attached tubing may be placed on the catheter to facilitate this process If fluid or air is being removed for relief of cardiopulmonary compromise, aspiration is continued until symptoms improve The catheter is subsequently removed and a sterile dressing is applied over the entry site Complications Risk of complications from thoracentesis is low.128 The most common complication of thoracentesis is pneumothorax (6% in meta-analyses).127–129,131 Use of ultrasound decreases risk of this complication and thus should be used whenever possible.130 A platelet count of greater than 50,000/mL and near-normal coagulation studies (international normalized ratio ,2) are ideal, but the procedure can be safely performed with careful technique and avoidance of the neurovascular bundle located on the inferior border of the rib Additionally, recent literature calls into question the need for correcting coagulopathy and thrombocytopenia prior to the procedure given the low risk of hemorrhagic complications.128,130,132,133 Still, many providers will attempt to correct the hematologic abnormalities before or during the procedure Soft-tissue infections can be avoided with use of proper sterile technique Insertion of the needle through existing skin infections or wounds should be absolutely avoided Reexpansion pulmonary edema (REPE) has long been reported in adult patients with removal of large volumes (.1500 mL) of fluid or air and usually is apparent in the first hours following thoracentesis but can occur up to 48 hours later.134,135 More recent literature reports the occurrence of REPE in children.134–138 Risk factors may include chronic lung collapse (.72 hours), evacuation of a large amount of pleural fluid or air (usually 1500 mL in adults, 20 mL/kg in children), brisk lung reexpansion, and excessively negative pleural pressures (less than 220 mm Hg) While rare, this complication is associated with high risk for morbidity and mortality (reported up to 20%); thus strategies to prevent REPE should be used Interpretation Analysis of pleural fluid is separated into two basic diagnostic categories: exudates and transudates Transudates arise from imbalances of hydrostatic or oncotic pressures, such as seen in congestive heart failure or nephrotic syndrome Exudates can be caused by a variety of mechanisms, most commonly from pleural and lung inflammation or impaired lymphatic drainage The criteria used to distinguish between the two have evolved but are rooted in Light’s Criteria Rule139 (Box 14.3) The updated combination of two or more of these criteria increase the diagnostic sensitivity for the rule More recent diagnostic rules, including the two-test rule and three-test rule, include pleural fluid cholesterol level greater than 45 mg/dL and not require concomitant serum levels to be obtained.140 • BOX 14.3 Light’s Criteria Rule for Diagnosing Exudative Effusions If at least one of the following criteria is present, effusion is defined as exudate: • Pleural to serum protein ratio 0.5 • Pleural to serum LDH ratio 0.6 • Pleural fluid LDH more than twice the upper limit of normal serum LDH value LDH, Lactate dehydrogenase Additional pleural fluid studies should be sent to aid in diagnosis, especially fluid for culture, cell count with differential, and cytology Low pleural glucose (,60 mg/dL) and pleural pH (,7.3) with very elevated nucleated cell counts (.50,000/mL) are highly suggestive of empyema Elevated pleural triglyceride levels (.110 mg/dL) and lymphocyte predominance suggest chylothorax, while triglycerides ,50 mg/dL effectively rule it out Elevated amylase suggests pancreatitis or esophageal rupture Advances in polymerase chain reaction (PCR) technology allow for rapid and accurate diagnosis of viruses and bacteria in pleural fluid.141 Summary Thoracentesis, when performed by skilled providers, can be a safe and useful diagnostic procedure for pediatric pleural effusions It can also be a useful technique to aid in resolving cardiopulmonary compromise resulting from significant thoracic air or fluid accumulation Tube Thoracostomy Tube thoracostomy (commonly known as chest tube) placement is a common procedure and may be required for a variety of reasons in critically ill pediatric patients Pneumothoraces can develop spontaneously, as a result of acute lung injury, or as a sequela of procedures or surgery Large parapneumonic effusions and empyemas resulting from infectious pulmonary processes are increasing in frequency and often require chest tube placement Hemothoraces or hemopneumothoraces from trauma frequently require evacuation and continuous drainage Chylothoraces in postoperative cardiac patients may require tube placement and drainage There are no absolute guidelines defining the size or type of effusion necessitating continuous drainage; rather, close assessment of patients’ symptoms and clinical status are paramount in decision-making.142 The technique used for placement depends on the nature of the material to be removed (e.g., viscous, thin, transudative, or exudative) Contraindications As with thoracentesis, tube thoracostomy has few to no absolute contraindications The relative risks are similar to those discussed earlier regarding thoracentesis, which must be weighed against the potential benefits of the procedure When emergent or urgent intervention is required, tube thoracostomy should not be delayed Supplies and Equipment Supplies required vary depending on the type of thoracostomy tube to be placed Tube type should be selected based on the predicted CHAPTER 14 Pediatric Vascular Access and Centeses etiology of the pathologic condition Traditional or larger-bore “surgical” thoracostomy tubes may be required for more viscous fluids found in hemothoraces or complicated loculated empyemas.19 Small-bore (,14 Fr) catheters, placed using modified Seldinger technique, are ideal for simple effusions and pneumothoraces However, recent evidence and guidelines suggest superiority of these smaller catheters even for loculated empyemas with the concomitant use of chemical debridement with fibrinolytics.143 Many institutions have specially designed chest tube trays with sterile instruments; commercially assembled kits are also available Typical requirements include sterile gauze, sterile towels for draping, syringes and needles for local anesthesia and aspiration, scalpel, curved hemostat or Kelly clamps of various sizes, needle driver, suture, and scissors Other materials required are an appropriately sized chest tube, chlorhexidine or povidone-iodine solution, sterile gloves, a drainage apparatus (e.g., Pleur-Evac, Teleflex), local anesthetic, and occlusive sterile dressing Technique As mentioned earlier, the technique for placement depends on the nature of material expected to be removed from the pleural space and the type of tube chosen The majority of effusions and pneumothoraces requiring continuous drainage in the pediatric critical care setting can be evacuated with the placement of a small-caliber tube (5 Fr to Fr) via a modified Seldinger technique.144 Placement of small-bore pigtail catheters are less painful than traditional tube thoracostomy; successful treatment of empyema with chemical debridement using fibrinolytic agents (e.g., alteplase or streptokinase) is well described and recommended as first-line therapy.142–146 Bedside ultrasound will facilitate fluid location and enhances the chance of procedural success Tube thoracostomy is quite painful Generous infiltration of the skin, subcutaneous tissue, intercostal muscles, underlying rib, and periosteum with local anesthetics can decrease sedation and analgesia requirements Care should be taken to avoid exceeding maximal local anesthetic dosages for weight Following administration of sedation and analgesia, the patient is placed in the supine position Throughout the procedure, aseptic technique should be observed The overlying skin is prepped with chlorhexidine or povidone-iodine and draped in sterile fashion A needle attached to a syringe (5 or 10 mL) is inserted in the fourth or fifth intercostal space in the midaxillary line Continuous aspiration is applied while the needle is advanced until fluid or air is obtained A guidewire is then placed into the pleural space through the finder needle A small skin incision with scalpel blade is made and the overlying skin and subcutaneous tissues are dilated with a skin dilator A small-bore pigtail catheter with multiple side holes is then placed over the wire and advanced into the pleural space The guidewire is removed and the catheter is attached to a standard chest tube drainage system The tube is anchored to the skin with suture or a commercially available suture-less skinanchoring device A variation of this technique allows for placement of largercaliber tubes via commercially available tube-over-obturator systems (e.g., Thal-Quick, Cook Medical) After placement of the guidewire as described earlier, progressively larger skin dilators are used to facilitate placement of a larger-bore chest tube Caution should be used with placement of these devices in diseases of poor lung compliance or pulmonary hyperinflation, as these conditions may predispose to intraparenchymal tube placement and the development of bronchopleural fistulas.147 109 Traditional techniques for larger-caliber tube thoracostomy may be required for drainage of highly viscous fluids, including cases of hemothorax or empyemas that fail small-caliber chest tube and chemical debridement with fibrinolytics.143 While observing aseptic technique, the skin is prepped with chlorhexidine or povidone-iodine and draped in sterile fashion, as described earlier A skin incision large enough to allow placement of the chosen tube is made with the scalpel parallel to the axis of the ribs in the fourth or fifth intercostal space in the midaxillary line A curved hemostat or Kelly clamp is used to bluntly dissect the underlying subcutaneous tissue until the superior border of the rib is reached The clamp is then used to push through and dilate the intercostal muscle and pleura above the superior border of the rib In a larger child, the index finger can be used to further dilate the subcutaneous tissues and intercostal muscles Any intrapleural adhesions can also be manually broken up The end of the chest tube is then attached to a clamp and inserted into the pleural space The clamp is opened and the tube advanced to the proper depth, ensuring that all side holes are within the chest cavity The tube should be advanced anteriorly for pneumothoraces and posteriorly for effusions The tube is then attached to a pleural drainage system Many techniques for securing chest tubes have been described, but the most important aspect of the choice of method is that the operator removing the tube knows how the tube was anchored Some operators prefer a horizontal mattress suture on both sides of the tube, while others prefer a purse-string suture that can be pulled together after the tube is removed If the latter technique is used, no knot is placed at the skin level, but extra suture is wrapped around the body of the tube and then tied to the tube itself Upon chest tube removal, the extra suture serves as skin suture for wound closure Maintenance Following successful chest tube placement, a chest radiograph is obtained to verify proper position and to evaluate for resolution of pleural fluid or pneumothorax Tubes should be evaluated for continued air leak by checking for air bubbles in the leak chamber of the drainage apparatus Persistent air leak with no evidence of pneumothorax on chest radiograph suggests the development of a bronchopleural fistula or airway injury Alternately, it could indicate potential air entrainment at a loose tubing connector site Some authorities suggest intermittent external negative pressure to “strip” the tube to maintain patency, although little evidence supports this practice.25 Instillation of fibrinolytics such as alteplase restores patency of tubes clogged by proteinaceous material.146 Timing of chest tube removal depends on the indication for placement Tubes placed for pneumothoraces may be removed following resolution of the air leak Our practice is to place the tube to water seal, without suction, for at least several hours and obtain a chest radiograph prior to removal Literature supports this practice.146,148–150 Tubes placed for drainage of pleural fluid may be safely removed once drainage has decreased to to mL/ kg per day Removal of large tubes may be painful and requires analgesia or sedation, especially in small children Tubes can be safely removed during the inspiratory or expiratory phase.151 Complications Thoracostomy tube placement has numerous potential complications, and rates of complication have been estimated as high as 30% The list of published complications is too extensive for this ... and 70%, and all other PAC parameters should be used to choose how to maintain Svo2 above this value This Svo2 goal can be achieved by fluid administration, blood transfusion, increasing or decreasing... Thoracentesis is a procedure used to remove abnormal accumulations of nonphysiologic substances from within the potential space of the pleura, including fluid (hydrothorax), blood (hemothorax), air (pneumothorax),... congestive heart failure and malignancy being less common causes.124–126 Volume resuscitation with third spacing after shock is also a cause of pleural effusions in the PICU There are many other