Lakeshore Veterinary Specialists, Emergency and Critical Care, Glendale, WI, USA
Thoracostomy and Tracheostomy Tube Placement
Identifying the need for a thoracostomy tube requires identification of respiratory distress related to pleural space fluid/air. When mild to moderate pleural expansion is occurring, the patient is usually tachypneic with an asynchronous breathing pattern. If severe, the patient may appear anxious, "short of breath" (rapid, choppy breathing), and orthopneic. Emergent situations with large volume rapid expansion will require thoracostomy tube placement. Additional qualifiers for identifying the need for a thoracostomy tube include >/=3 treatments with thoracentesis in a 24-hour period, signs of cardiovascular instability, the need for a prolonged anesthetic procedure, and/or requiring positive pressure ventilation.
Supplemental oxygen is provided in any form tolerated by the patient in respiratory distress. A peripheral IV catheter is placed. In most cases, the patient with severe respiratory distress requires minimal restraint, but may benefit from administration of an anxiolytic or sedative such as butorphanol (0.4 mg/kg IV/IM) or midazolam (0.25–0.5 mg/kg IV/IM). The cat may require staged interventions, starting with the administration of an anxiolytic or sedative first (IM), then placement of an IV catheter with periods of rest in an oxygen-enriched environment.
Analgesia is administered by injection IV or locally prior to making a skin incision. It is ideal to perform the tube placement procedures under controlled conditions, with the patient orotracheally intubated with careful controlled assisted ventilation with oxygen. Injectable anesthesia is used in the form of etomidate, alfaxalone, propofol, alprazolam or ketamine, with a benzodiazepine. When laryngeal function is in question, propofol is the anesthetic of choice to permit laryngeal function examination. A laryngoscope should be used to reduce the risk of improperly intubating the esophagus. A variety of orotracheal tube sizes should be readily available. In situations where the larynx cannot be visualized, but palpated, then the tube may be guided in digitally, or by inserting a polypropylene catheter into the trachea over which an orotracheal tube is fed and the catheter removed. Proper placement of the orotracheal tube is ensured by 1) visual inspection, 2) ausculting lung sounds bilaterally with a stethoscope during the administration of positive pressure ventilation, 3) evaluating the end-tidal CO2 (ETCO2) - if the patient is tracheally intubated and spontaneously or assist ventilating, then the ETCO2 should be >25 mm Hg, and if the ETCO2 is <5 mm Hg, the tracheal tube may be misplaced in the esophagus or pharynx. Once airway patency has been established, then dedicated cardiorespiratory monitoring is initiated with pulse oximetry, ETCO2, ECG and indirect arterial blood pressure.
Once the decision has been made to place a tube, there must be a commitment to 24-hour direct monitoring or transfer to a 24-hour facility.
Thoracostomy Tube Placement
Thoracostomy tube placement is necessary when large volumes of fluid or air need to be removed from the pleural space, either in an intermittent or continuous manner. Conditions that warrant thoracostomy tube placement include hemothorax, pyothorax, chylothorax, postoperative thoracotomy, foreign body penetration, and pneumothorax. Pneumothorax can result from airway or lung rupture, thoracic wall trauma, esophageal trauma, and bulla tear.
Thoracostomy tube placement is performed through a mini-thoracotomy along the lateral thoracic wall using sterile technique. Large-bore tubes are used primarily with traumatic situations, when blood and/or air accumulations can be rapid and continuous aspiration is necessary to keep the lungs inflated. Choice of tube should be based on the size of the patient and the material being evacuated. Tension pneumothorax should be managed with a large-bore thoracostomy tube (approximately 1/2–2/3 the width of the intercostal space), and in rare cases require multiple tubes in a single hemithorax or bilaterally to overcome the volume leak from large airway tears. Patients with voluminous viscous effusions may also need large-bore tubes placed to improve flow and reduce occlusion. Red rubber tubes tend to kink, cause more tissue irritation, and occlude more frequently than purpose-made polyvinyl chloride (PVC) or silicone thoracostomy tubes. Thoracostomy tubes should be placed and handled under strict asepsis. Fur should be clipped from the caudal border of the scapula to the last rib, and from dorsal to ventral midline. Skin should be surgically scrubbed, and the patient should be fully draped to prevent contamination of the tube and insertion site.
Tubes should be pre-measured such that they should enter the pleural space at the 7–9th intercostal space and terminate near the second rib.
A skin incision is made over the 11th intercostal space and the mid to dorsal third of the thorax, through the skin approximately the diameter of the tube being used. The skin is either retracted cranially by an assistant, or large curved forceps are used to make a tunnel under the subcutaneous tissue or latissimus dorsi muscle to the level of the 8–9th intercostal space. The forceps are pushed through the intercostal tissue and opened to establish a pathway that the thoracostomy tube with trocar can be fed through into the pleural space. Using a trocar during placement keeps the tube stiff and facilitates placement into the cranial thorax. The tip of the trocar should never extend beyond the tip of the tube. The tube should be grasped with one hand at the distal end to prevent the tube from advancing too far to prevent accidental puncture of intrathoracic organs.
Once the thoracostomy tube is in the pleural space, it is directed into a cranial-ventral position, with the tip ending at the 2nd rib space. All side holes must be inside the pleural space. The trocar is removed and the tube is secured by suturing to the periosteum of the rib, around the rib, or to the skin at the exit site. A second stabilizing suture is placed several inches from the insertion site in the skin and around the tube. The pleural space is evacuated either manually with a syringe or by connection to a continuous drainage system. Postplacement radiographs are obtained. Having the distal tip all the way into the thoracic inlet can result in significant patient discomfort and it may be more comfortable if the tip of the tube is at the level of the second rib. A local bandage is placed with sterile gauze and transparent wound dressing or a more substantial bandage around the chest if additional wounds need to be covered. The insertion site is inspected only if there is failure to establish negative pressure, or there is excessive discharge. An Elizabethan collar is used to prevent premature removal. Potential complications include iatrogenic pneumothorax, intrathoracic organ puncture, and infection.
Pleural Catheter Placement
Pleural catheter (small-bore, wire-guided chest drain) placement can be used for intermittent drainage with moderate to large volume, slow pleural expansion. A flexible pleural 10–14g catheter is placed unilaterally or bilaterally using a modified Seldinger technique. Having a larger diameter than a needle, this type of catheter permits more rapid removal of pleural contents with less restraint. This type of catheter is secured to the skin and allows repeated centesis over a short term (24–48 hours) without additional restraint. The Seldinger technique involves the placement of a catheter into the pleural space through which a j-wire is passed. The catheter is removed while the j-wire is held in place. A dilator is placed over the j-wire and used to stretch the skin and body wall around the j-wire. The dilator is removed and the catheter placed over the j-wire into the pleural space. All the side holes should be within the pleural space. The j-wire is then removed and the catheter is sutured in place. A local dressing is applied, and an Elizabethan collar used on the patient to prevent premature removal. Potential complication includes lung laceration and bleeding.
The pleural drainage tube is removed when the air leak appears sealed, and/or the fluid volumes have markedly decreased. Although a general rule is to keep the tube in place until only 1–2 mL/kg/d of fluid/air is removed, but the entire clinical picture is included in the assessment.
References are available on request.