Perioperative and Anesthetic Management of Complete Tracheal Rupture in One Dog and One Cat
The authors describe two animals (one dog and one cat) that were presented with severe respiratory distress after trauma. Computerized tomographic imaging under general anesthesia revealed, in both cases, complete tracheal transection. Hypoxic episodes during anesthesia were relieved by keeping the endotracheal tube (ETT) positioned in the cranial part of the transected trachea and by allowing spontaneous breathing. Surgical preparation was performed quickly, and patients were kept in a sternal position to improve ventilation and oxygenation, and were only turned into dorsal recumbency shortly before surgical incision. A sterile ETT was guided into the distal part of the transected trachea by the surgeon, at which point mechanical ventilation was started. Both animals were successfully discharged from hospital a few days after surgery. Rapid and well-coordinated teamwork seemed to contribute to the good outcome. Precise planning and communication between anesthetists, surgeons, and technicians, as well as a quick course of action prior to correct ETT positioning helped to overcome critical phases.
Introduction
Complete tracheal rupture is a life-threatening situation requiring emergency surgical treatment. It occurs rarely in dogs and cats, usually secondary to traumatic events, and represents a challenge for the anesthetist due to difficulties in maintaining patient ventilation and oxygenation until surgical repair.1,2
Several reports describe the incidence and management of incomplete tracheal ruptures in cats, often occurring as a complication of endotracheal intubation.3,4,5 To the study authors' knowledge, the anesthetic management of complete tracheal transection surgical repair has not yet been described in small animals. This report describes two cases the perioperative and anesthetic management for diagnostic computed tomography (CT) and tracheal surgery in one cat and one dog with complete traumatic tracheal rupture.
Case Report
Case 1
A 2 yr old male papillon weighing 2.5 kg was presented to the emergency service of the Veterinary Teaching Hospital of Berne after being bitten by a larger dog in the neck and abdominal area that morning. The wounds had been cleaned and sutured by the primary veterinarian earlier that day.
Clinical examination on arrival revealed depressed mentation, respiratory distress with rapid, shallow breathing (60 breaths/min; reference range, 15–30 breaths/min) and bilateral subcutaneous emphysema extending from the neck to the abdominal region. Heart rate was 110 beats/min (reference range, 70–160 beats/min), and rectal temperature 38.4°C (reference range, 37.5–38.5°C). Serum biochemical profile and hematology (hematocrit, total protein, creatinine, glucose, electrolytes, and pH) were within physiological ranges. Auscultation revealed increased respiratory sounds in the cranial thoracic areas and decreased sounds in the caudal lung fields. The dog was placed in an O2 cage set to deliver an inspired O2 concentration of 50%. Crystalloidsa were administered at a rate of infusion of 4 mL/kg/hr over 14 hr until the next day. Three episodes of severe labored breathing occurred over night that, each time, could be improved through bilateral thoracocentesis, where approximately 10–60 mL of air was aspirated from each hemithorax.
The following day, the dog was anesthetized to perform CT and surgery. The dog was premedicated in the O2 cage with IV acepromazineb (10 µg/kg) and then, while receiving O2 supplementation by mask, was transported to the preparation room where it received a bolus of fentanylc(1 µg/kg IV) followed by a continuous rate infusion (5 µg/kg/hr). Propofold, titrated to effect, was administered IV (total dose was 3 mg/kg) until the trachea could be intubated. Tracheal intubation was performed under laryngoscopic guidance, which allowed direct visualization of the arytenoids. Induction and intubation were smooth and uneventful. The 4.5 mm diameter endotracheal tube (ETT) was connected to a circle breathing system and anesthesia was maintained with 1.2% of isofluranee delivered in 100% O2. IV crystalloids were administered at a rate of 10 mL/kg/hr. Monitoringf included lingual pulse oximetry (SpO2), sidestream capnography, electrocardiography, and noninvasive blood pressure measurementsg. Physiologic parameters were recorded q 5 minutes. Shortly after induction, the SpO2 dropped to 75% (reference range, 97–100%) and the dog showed respiratory difficulty. When attempting mechanical ventilation, adequate tidal volumes could not be provided despite the application of high inspiratory pressures. Therefore, in order to reconfirm the correct position of the ETT, laryngeal inspection was performed. Because pneumothorax was suspected, bilateral thoracocentesis was immediately performed and 40 mL of air and 10 mL of blood were drained from the right hemithorax. Improvement of the spontaneous breathing pattern followed (40 breaths/min); however, due to the tracheal transection, the lack of continuity between the distal end of the ETT and the lower airways made the sampling of pure alveolar gas difficult. As a result, the end tidal CO2 (ETCO2) measurement was still not reliable. The dog's SpO2 increased to 97% and the dog underwent CTh. Images were acquired with the patient in sternal recumbency using 3 mm thick slices with a pitch of 0.938. A complete tracheal rupture from the level of the fourth cervical vertebra to the sixth cervical vertebra was identified (Figure 1). Severe pneumomediastinum and subcutaneous emphysema were found bilaterally, the latter extending from the head down to the pelvic region. Pulmonary fields were diffusely hyperdense and had a ground-glass appearance in the dorsal half, while in the ventral portions, consolidation could be seen symmetrically on both sides (Figure 2). Likely differential diagnoses for those changes included atelectasis, hemorrhage, and contusion. Mild pneumothorax could be observed in the caudodorsal regions, more pronounced on the right side. The position of the ETT position was extratracheal, lateral, and ventral to the left first rib. After pulling back the ETT slightly, ETCO2 was 88 mm Hg (reference range, 35–45 mm Hg). Tachypnea (70–80 breaths/min) was still observed. The dog was moved to the preparation room and prepared for surgical repair of the trachea. As soon as the dog was positioned in dorsal recumbency, the SpO2 dropped dramatically (60%) and no ETCO2 could be measured. Therefore, preparation of the surgical field was completed while holding the dog in sternal position. The ETT was marked for determination of inserted length then replaced by a sterile tube that was advanced endotracheally to the previously measured depth. Only one attempt was made to perform arterial catheterization prior to surgery, which could not be done successfully in a reasonably short time; therefore, the decision was made to postpone the arterial line placement until the patient was clinically more stable.
Citation: Journal of the American Animal Hospital Association 51, 1; 10.5326/JAAHA-MS-6022
Citation: Journal of the American Animal Hospital Association 51, 1; 10.5326/JAAHA-MS-6022
The dog was transported to the operation theatre and turned into dorsal recumbency just prior to the skin incision. Immediately after the position change, the SpO2 dropped from 97 to 79%. Following a ventral approach to the cervical trachea the two segments, which were connected with remnant tissue forming an incomplete cylindrical membrane, were localized. The distal segment was then pulled cranially using traction sutures, and the tip of the ETT was guided into the distal fragment of the trachea. The cuff was then inflated by the anesthetist, and the SpO2 subsequently increased to 97%. A tracheal anastomosis was performed. The segments were apposed to each other using stay sutures. Several simple interrupted sutures of 3-0 polydioxanone were placed around the edge of the tracheal cartilages. Four tension-relieving sutures (2-0 polydioxanone) were placed around the cartilages adjacent to the anastomosis. The subcutaneous tissues and skin were closed routinely. During surgical repair, the suture needle punctured the ETT cuff, which immediately deflated, leading to a decrease in SpO2 (78%). The dog was extubated and the ETT was replaced. As soon as the cuff was inflated, mechanical ventilation could be initiated. Pressure control was selected as ventilation mode, set to deliver a peak pressure of 10 cm H2O, which resulted in a tidal volume of 10 mL/kg. The respiratory rate was set to 25 breaths/min. The saturation progressively increased over 20 min then remained >95%. At the end of the surgery, another 30 mL of air was withdrawn from the right hemithorax. The patient was weaned from the ventilator and allowed to breathe spontaneously. The SpO2 values remained >95%. The ETCO2 was low (27–23 mm Hg) because the dog was still tachypneic (50 breaths/min). An arterial catheter was placed in the femoral artery (blood gas values have been summarized in Table 1), and the dog was allowed to recover from anesthesia.
After extubation, recurrence of pneumothorax required thoracocentesis. As the study authors could not rule out bilateral air production in the thorax, and considering that surgical manipulation of the cranial mediastinum could have contributed to the development of bilateral pneumothorax, the decision was made to insert bilateral thorax drainage tubes. Anesthesia was induced with propofol (4 mg/kg IV). After tracheal intubation, the ETT was connected to the circle breathing system and isoflurane in 100% O2 was delivered to the patient. The dog required pressure-supported ventilation, which resulted in a tidal volume ranging between 8 and 12 mL/kg. Arterial O2 saturation stayed >95% throughout the procedure. At recovery, the dog had severe hypothermia (34°C), and extubation could only be performed 1 hr after the end of inhalation anesthesia. During that time period, the dog‘s body temperature was restored through active warming.
In the intensive care unit, the patient was placed in an O2 cage (50% O2) for 3 more days to provide O2 supplementation. Respiration, blood pressure, and SpO2 were regularly monitored. Postoperative medication included amoxicillin tridhydrate/clavulanate potassiumi (20 mg/kg q 12 hr PO for 16 days), metronidazolej (16 mg/kg q 12 hr IV for 5 days), carprofenk (4 mg/kg IV q 24 hr), fentanyl (3 µg/kg/hr IV, replaced after 12 hr with buprenorphinel [20 µg/kg IV q 6 hr]), ropivacaine 0.5%m (1 mg/kg intrapleural q 4 hr), ranitidinen (1 mg/kg IV q 12 hr), dolasetrono (0.6 mg/kg IV q 24 hr), and crystalloid fluid therapy (2 mL/kg/hr for 7 days). Criteria for thorax drain removal were no air production over 24 hr and <2 mL/kg/24 hr fluid production. In the left hemithorax, that was the case after 24 hr, whereas the right drain had to be left in place until the third day after surgery. Subcutaneous emphysema progressively decreased, and a tracheoscopy performed 3 days after surgery indicated satisfactory healing because the wound edges were well adapted with no signs of dehiscence. Neither swelling nor other signs of inflammation were present.
Eight days after surgery, the dog was discharged from the hospital. Nine months after the surgery, the owner reported the dog to be energetic and playful, although possibly less resistant to heat.
Case 2
An 18 mo old castrated male domestic shorthair was presented to the emergency service for dysorexia, weight loss, and labored breathing of 4 days duration. Physical examination revealed mild dehydration (5%) and the presence of diffuse subcutaneous emphysema at the level of the neck and the chest, caudally to the left shoulder. Loud inspiratory stridor was heard bilateral over the thorax and at the level of the cervical trachea. Heart rate was 180 beats/min (reference range, 120–160 beats/min) and respiratory rate was 28 breaths/min (reference range, 15–30 breaths/min). Rectal temperature was 38°C. Hematology and serum biochemical analysis (renal profile, liver enzymes, electrolytes, and total protein) were unremarkable. As the cat was uncooperative and difficult to handle, it was sedated with IV medetomidinep (0.01 mg/kg) to allow further diagnostics. O2 supplementation was provided by mask, and crystalloids were administered IV at a rate of infusion of 10 mL/kg/hr. O2 saturation was continuously monitored by SpO2. CT (multi slice CT) of the cervical thoracic region, performed with the cat still under sedation only, revealed the presence of a 6 cm long tracheal rupture in the oblique plane, between the fifth cervical and second thoracic vertebrae (Figure 3).
Citation: Journal of the American Animal Hospital Association 51, 1; 10.5326/JAAHA-MS-6022
The cat was anesthetized to allow emergency thoracotomy and surgical repair of the tracheal rupture. Anesthesia was induced with fentanyl (5 µg/kg IV) and propofol titrated to effect (total dose was 1.8 mg/kg). The trachea was intubated with a 3 mm diameter ETT, inserted so that its distal tip ended just proximal to the laceration. Then 100% O2 was administered via a circle rebreathing system. Monitoring included lingual SpO2, sidestream capnography, electrocardiography and noninvasive blood pressure measurements. Parameters were recorded q 5 minutes. General anesthesia was maintained with a constant rate infusion of propofol (0.4 mg/kg/min) and fentanyl (10 µg/kg/h) administered via syringe pump. Desaturation (SpO2 was 78%) occurred during preparation of the surgical field despite 100% O2 delivery and decreased to 45% as soon as the cat was positioned in dorsal recumbency on the operating table. Therefore, the cat was temporarily placed in lateral recumbency until the start of the procedure. This resulted in improvement of O2 saturation (SpO2 was 80%). Cranial median sternotomy and a ventral approach to the caudal cervical trachea were performed. The two tracheal segments were localized, united by a bridging connective tissue similar to the one described for the previous case. Traction sutures were placed on the distal segment to pull it cranially. The cat was extubated, and a new sterile ETT measuring 12 cm in length and 3mm diameter was inserted orotracheally by the anesthetist. As soon as the caudal end of the ETT reached the rupture, the surgeon guided it into the distal fragment of the trachea over the laceration and the ETT cuff was inflated. At that point, ventilatory support was provided with pressure-controlled mode. The ventilator was set to deliver a peak airway pressure of 10 cm H2O, which resulted in a tidal volume of approximatively 10 mL/kg. The respiratory rate was set at 15 breaths/min. Saturation increased to >90%. A tracheal anastomosis over the ETT was performed, and thereafter, the ETT was pulled cranially so that its distal end was again proximal to the rupture and the suture checked for leakage. The thorax was closed after unilateral thoracic drain tube placement. At the end of the surgical procedure, the cat was positioned in sternal recumbency and allowed to breathe spontaneously. Propofol administration was discontinued, and the fentanyl rate of infusion was decreased to 4 µg/kg/hr. The cat was allowed to recover in the intensive care unit in an O2 cage set to provide an inspired O2 concentration of 50% where it remained for the following 3 days. Meloxicamq (0.1 mg/kg IV) was administered postoperatively followed by oral tablets for 10 more days q 24 hr at the same dose. Fentanyl administration was discontinued 18 hr after recovery then was replaced by buprenorphine (0.01 mg/kg subcutaneously q 6 hr for 8 days). IV crystalloids were administered at a rate of 2 mL/kg/hr for 10 days. The thoracic drain was removed after 3 days. One week after surgery, the cat still showed a fast and shallow breathing pattern, worsening during manipulation or stress. Radiographs, CT, and tracheoscopy were performed under general anesthesia and a tracheal stenosis was observed over a distance of 3.8 cm, with a luminal diameter of 2 mm, which was significantly smaller than the tracheal diameter of 8 mm measured at the level of the fifth cervical vertebra (Figure 4). The right middle lung lobe was reduced in volume, homogenously hyperdense, and had an increased width of the lobar bronchus. A very focal but pronounced narrowing of this bronchus was noticed close to the bifurcation. Those changes were felt to reflect lobar atelectasis, and the bronchial luminal obstruction, being absent from the original scan, was interpreted as compatible with a mucous plug, or less likely, a ring-like accumulation of foreign material or a focal concentric wall thickening.
Citation: Journal of the American Animal Hospital Association 51, 1; 10.5326/JAAHA-MS-6022
The patient was treated with metronidazole (20 mg/kg IV q 12 hr), amoxicillin trihydrate/clavulanate potassium (20 mg/kg q 8 hr), enrofloxacinr (5 mg/kg IV q 24 hr) for 10 days each. The cat's clinical condition progressively improved and was released from the hospital 14 days after admission. A CT scan performed 3 mo after surgery showed a very focal tracheal stenosis of 3 mm in diameter. Pronounced disseminated parenchymal changes were also observed, but the nature of those findings remained unknown. The focal narrowing of the right middle lung lobe bronchus noticed in the previous scan was no longer seen.
Discussion
There is a lack of information concerning the management of patients undergoing tracheal rupture repair. Until now, only one report of a cat with a complete intrathoracic tracheal transection has been published, which describes both the surgical treatment and the anesthesia technique.6 The animal reported therein was euthanized during surgery due to anesthesia-related complications. Although ventilation management was challenging during anesthesia, both cases presented herein were successfully treated and could be discharged from the hospital some days later. Effective and rapid teamwork between anesthetists and surgeons contributed to the good outcome.
Positioning of the patients during diagnostics and preparation of the surgical field were critical phases and required good planning and excellent communication between anesthetists, radiologists, and technicians. In both animals, SpO2 decreased when supine: therefore, preparation of the surgical field was performed as quickly as possible and by holding the patients in a sternal position. Both patients were turned into dorsal recumbency only on the operation table, when the surgeons were ready.
Another critical moment was the puncture of the ETT cuff when suturing the canine trachea. That unexpected complication required prompt removal and replacement of the ETT; however, a quick and coordinated course of action prevented further damage. Kästner et al. (2004) performed endobronchial intubation in a cat undergoing surgery for tracheal laceration.5 Fiberendoscopic guidance of the ETT was used to place the tip of the tube caudal to the lesion. Endoscopy may be a useful tool to localize the laceration and guide correct ETT positioning, but should be performed only in stable patients.7 In the cases presented herein, tracheoscopy was not considered because both patients had severely compromised respiratory function. Furthermore, the usefulness of endoscopic guidance after complete rupture of the trachea is questionable because there is no connection between the fragments that one could follow. Orientation in traumatic tissue could be challenging and time consuming and might lead to increased morbidity or mortality. On the contrary, the promptness in making decisions during critical events, as well as well-coordinated teamwork, seemed to be the main determinants of the positive outcome of the two cases presented herein.
Traumatic tracheal injuries are often associated with skin and muscle lacerations. In emergency settings, the distal fragment of the lacerated trachea could be intubated through the neck wound to ensure ventilation. That technique has been described for an Arabian mare with open tracheal rupture and for small animal airway management in the emergency setting.8,9 The cat presented in this report had no such external lesions, and the tracheal transection was intrathoracic, which made tracheostomy distal to the laceration impossible. In the dog's case, the primary veterinarian had sutured the wound over the ruptured trachea the day before, and in the following hours, contamination and infection had already taken place. Therefore intubation was performed as usual in both animals, letting them breathe spontaneously during diagnostics and facilitating respiration through maintenance of sternal or lateral recumbency as long as the lacerated trachea was not surgically repaired. Those supporting measures, as well as limiting the diagnostics to essential (which implied excellent communication between all the clinicians involved), helped prevent total collapse of the lacerated tracheal parts. Further problems that may occur if intubation is performed directly through the wound rather than orotracheally are a higher risk of contamination of the lower airways and decreased visibility of the surgical field due to the bulky connection of the ETT to the breathing system.10
Total IV anesthesia (TIVA) is recommended for maintenance during major airway and pulmonary surgeries. In those cases, one obvious advantage of TIVA over inhalation anesthesia is the prevention of environmental contamination due to leakage of anesthetic gases when a tight seal between the airways and the breathing system cannot be established. Additionally, the magnitude of pulmonary hypoxic vasoconstriction, a protective physiological mechanism diverting blood flow from hypoxic to better-ventilated areas of the lungs, is directly inhibited in a dose-dependent manner by volatile anesthetic agents. That undesired effect may worsen the ventilation perfusion mismatch by further increasing the shunting fraction.11 It should be considered that whenever pulmonary or airway abnormalities compromise the effectiveness of ventilation, the delivery and uptake of inhalation anesthetics, and therefore the maintenance of an adequate plane of anesthesia, might be challenging.12 For all of those reasons, TIVA was chosen to maintain anesthesia in the second case presented herein.
During inhalation anesthesia, when respiratory depression is induced by the volatile anesthetics, the anesthetic agents' uptake decreases, making deepening of the narcotic plane a self-limiting process. Inversely, during TIVA, that negative feedback mechanism is not preserved, making the respiratory depression more difficult to manage. That is especially true if positioning of the ETT is unsuccessful. As the dog showed an appropriate anesthetic depth by breathing spontaneously throughout the whole procedure, the study authors made the decision to maintain general anesthesia with inhalation anesthetic agents rather than with TIVA.
In the two cases presented herein, CT was the first choice for diagnostics. Evaluation of airway, as well as other organ integrity, is more straightforward with CT in polytrauma patients. Such patients are often subject to more stress and pain when manipulated for standard radiographic projections than with CT, which often yields diagnostic studies in a minimal amount of time.13 Additionally, radiography may be of limited use in confirming the exact location and length of a tracheal laceration.14
Because of the potential for life-threatening respiratory complications, the postoperative phase of tracheal rupture repair may be critical. O2 supplementation is mandatory for patients unable to maintain a SpO2 within physiologic ranges during the postoperative period. However, due to the potential for O2 toxicity, O2 therapy should be carefully titrated to effect and limited, in terms of both duration and delivered inspired fraction, to the least necessary to achieve acceptable saturation values.
Conclusion
Fast and well-coordinated teamwork was an important factor to the good outcome in the two cases presented herein. Quick diagnostic tests allowing for minimal patient restraint and stress, such as multi slice CT, should be considered. Precise planning and communication between anesthetists, surgeons and technicians help prevail over critical stages.
Transverse computed tomographic (CT) view of the dog in case 1 at the level of the fifth cervical vertebra. Marked subcutaneous emphysema is present (asterisk). The cuff of the endotracheal tube (white arrowhead) is seen exiting the trachea ventrally through the rupture. A large amount of gas surrounds the trachea and structures of the neck (black arrow), communicating caudally with a pneumomediastinum. A microchip is seen in the subcutaneous tissues of the left side.
Sagittal reconstruction of the dog in case 1. Subcutaneous emphysema (asterisk) and pneumothorax (asterisk asterisk) are visible. The tip of the endotracheal tube (white arrow) extends through the defect in the trachea (T) and points ventrally to the sternum. Increased lung attenuation can be observed in the cranial pulmonary fields (black arrow).
Sagittal reconstruction of the feline cervicothoracic region (case 2). The trachea is interrupted at the level of the fifth cervical vertebra (thick arrow), caudal to which a collection of gas is seen between the fascial planes. The thin arrow points to the caudal portion of the ruptured trachea.
Transverse lung window CT at the level of the seventh cervical vertebra performed 7 days postoperatively in the cat (case 2). The trachea (arrow) has an effective diameter of 2 mm.
Contributor Notes
