Respiratory emergencies: postoperative management of respiratory distress (Proceedings)
Patients that have undergone emergency surgery to address respiratory distress are routinely supplemented with oxygen in the early recovery period and are monitored for oxygenation status using physical parameters (respiratory rate, respiratory character, and mucous membrane color), pulse oximetry (SpO2), and, when practical, arterial blood gases (PaO2). Clinical signs of hypoxia (increased respiratory rate, abnormal respiratory character, and pale, cyanotic, or "muddy" mucous membranes), low SpO2 (less than 96%), and low PaO2 (less than 80 mmHg) indicate continued use of supplemental oxygen. Oxygen therapy is continued if normoxia cannot be achieved when the animal is breathing room air, and positive-pressure ventilation with positive end-expiratory pressure may be necessary if normoxia cannot be achieved with administration of 100% inspired oxygen. Monitoring is not limited to the above mentioned parameters. All critically ill respiratory patients are evaluated at periodic intervals by assessing attitude, pulse rate and quality, and capillary refill time, and by performing thoracic auscultation. Invasive and/or noninvasive arterial blood pressure is monitored in patients with potential (or existent) hemodynamic instability. Intakes (parenteral fluid therapy and oral intake) and outputs (urine, emesis, and defecation) are monitored. Because of potential pulmonary compromise in certain respiratory distress patients intravenous fluid therapy must be performed judiciously to prevent volume overload; therefore, central venous pressure monitoring is employed.
Management Of Tracheostomy Tubes
Supplemental oxygen during recovery can be achieved through a small tube (8 french) placed into the lumen of the tracheostomy tube. The oxygen flow rate should be nearly half of what is required with intranasal oxygen administration because oxygen is delivered directly into the trachea, making the trachea an oxygen-rich reservoir. Upon recovery from anesthesia the need for supplemental oxygen is based on the oxygenation parameters listed above.Tracheostomy tube hygiene is extremely important because of the risk of iatrogenic respiratory infection and the possibility of acute fatal obstruction due to accumulated respiratory tract secretions. Immediately after surgical placement and for the first several hours tracheostomy tubes require constant vigilance and hourly removal of intraluminal secretions. Around-the-clock observation and care are mandatory. Preferably, the tube in place is one with an inner cannula that can be temporarily removed for cleaning and sanitizing and then replaced. Small tracheostomy tubes (such as in toy dogs and cats) do not have inner cannulae; therefore, clean (ideally, sterile) soft suction catheters are inserted down these small tracheostomy tubes to clear the tubular lumens of secretions.
Strict adherence to asepsis cannot be overemphasized in tracheostomy tube maintenance. Unfortunately, it is rarely practical to use sterilized equipment at each tube cleaning session, but sanitization is possible. Use a 0.05% chlorhexidine solution to soak (and clean) tracheostomy tube components and suctioning accessories, but be sure to rinse with sterile saline any component that may come in contact with, or drip onto, respiratory tract tissues. Wear examination gloves when providing tracheostomy tube care, and remember to periodically cleanse the peristomal skin with warm 0.05% chlorhexidine solution. Scrub solutions are avoided to prevent contact of soap with respiratory epithelium.
Humidification of the airway is important to decrease the viscosity of respiratory secretions and facilitate their removal. Humidification is achieved by instillation of 2 to 3 ml of sterile isotonic saline solution into the trachea at the end of each tube cleaning session. If humidification is not sufficient to prevent respiratory tract dessication and development of viscous secretions, aerosol therapy can be performed.
When it is determined that the tracheostomy tube is no longer needed anchoring sutures and umbilical tapes are cut, the tube is extracted, and the resultant open wound is allowed to heal by second intention. The patient may continue to breathe through the stoma for several days until sufficient wound contraction occurs.
Postoperative Care After Tracheal Resection/Anastomosis
Intranasal oxygen administration is recommended in the early recovery period and is continued based on individual patient needs which are determined as described above. Likewise, postoperative monitoring is performed as described above.
Monitoring for dehiscence of the anastomotic suture line is by physical examination. The obvious clinical sign of a leaky tracheal anastomosis is subcutaneous emphysema, particularly with cervical tracheal disruption. Pneumomediastinum, detected by thoracic radiography, may be present when the intrathoracic trachea is the source of leakage; however, pneumothorax, a more life-threatening condition, could develop with intrathoracic tracheal anastomosis discontinuity because the mediastinum is perforated during surgical dissection. Pneumothorax can be diagnosed radiographically, but observing altered respiratory character and detecting hyper-resonance on thoracic percussion should prompt thoracocentesis to confirm the suspicion in dyspneic animals. Patients with intrathoracic tracheal anastomosis should have an intra-operatively placed thoracic tube present during the early recovery period. This tube is in place to monitor for pneumothorax during recovery, but is usually removed within a few hours after thoracotomy; therefore, subsequent suspicions of pneumothorax due to tracheal anastomotic dehiscence will require confirmation by thoracocentesis followed by thoracic radiography.