dental tracheal tear malpractice anesthesia claim warning

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dental tracheal tear malpractice anesthesia claim warning

Postby guest » Mon Oct 20, 2003 3:35 pm


Tufts Animal Expo Conference Proceedings
September 1, 2001


Technician Small Animal Anesthesia /Surgery


Anesthesia/Surgery(Tech) Track

Keywords: trachea, cat, dog, endotracheal tube, emphysema, pneumothorax

Intubation-associated tracheal tear in cats is not a new disease but it has not been reported in the literature until the last 2 years. While doing my residency at Tufts University it was noted that cats were presenting for subcutaneous emphysema or respiratory problems with a presumptive diagnosis of tracheal rupture. The clinic admitted cases that were treated both medically and surgically for this disease. An AVMA Liability Trust newsletter reported on malpractice claims of subcutaneous emphysema and issued a warning regarding the proper technique for intubation and proper evaluation and monitoring for cats that develop subcutaneous emphysema. In reviewing the literature only one case report describing this condition was found.

Because of the number of cases seen at Tufts and at other institutions a retrospective study was conducted.

Cats were entered into the study if they had a history of previous inhalational anesthesia requiring endotracheal intubation and if they presented for respiratory distress and/or subcutaneous emphysema. A total of 20 records were reviewed from 1996-1998. Cats presented to Tufts University, Angell Memorial Animal Hospital, The Animal Emergency Center, and Coastal Carolina Veterinary Specialists. The records were evaluated for signalment, history, presenting complaint, physical exam findings, diagnostics and treatment. A standard questionnaire was also submitted to owners and the referring veterinarians.

The domestic shorthair cat was the predominant breed. The age range was 4 months to 17 years. There were 13 spayed females and 7 castrated males. Fourteen of the 20 cats presented for dental surgery prior to presentation. Cats presented for emergency evaluation anywhere from 5 hours to 12 days postoperatively. All twenty presented for signs of subcutaneous emphysema. Other common signs included dyspnea, anorexia and lethargy. On physical exam all cats had subcutaneous emphysema and some also showed signs of respiratory distress. Bloodwork was unremarkable in all cats except two. Radiography yielded the most information. In all cats radiographed (17) pneumomediastinum and subcutaneous emphysema were present. Tracheoscopy was performed on two cases but no tears were seen. Cats with mild to moderate signs of respiratory distress and subcutaneous emphysema were treated conservatively with medical management. Medical treatment included monitoring of respiratory rate and effort and cage rest. Some cats were also treated with supplemental oxygen and sedatives. Cats with severe signs of respiratory distress or worsening subcutaneous emphysema were taken to surgery. Surgery involved an exploratory of the neck +/- a median sternotomy. The tear was identified and sutured closed. Postoperatively these cats were managed like the medical group. The tears seen at surgery were longitudinal and were located at the level of the thoracic inlet. They were on the dorsolateral aspect of the trachea at the junction of the tracheal rings and the trachaelis muscles. Tears ranged from 2 to 5 cm in length and were closed in a simple interrupted pattern.

Follow-up questions were asked of the owners to see how their cats had fared. Seventeen owners responded and 13 of 17 had been rechecked by their veterinarian, nine for the same problem and 4 for other problems. None of these thirteen had respiratory signs at recheck. None of the 17 had respiratory signs present after the incident of tracheal tear. It took anywhere from 1 to 6 weeks for the subcutaneous emphysema to resolve with most cases resolving within 2 weeks. Five cats were successfully cage rested but owners said that those that were not cage rested stayed quiet at home. Most cats did not have radiographs taken postoperatively. Only two cats had had subsequent anesthesia. Both, however, were not intubated.

Referring veterinarians were also asked a series of questions (two would not discuss) to evaluate their practice of endotracheal tube type and usage . Both high and low pressure cuffed endotracheal tubes were used. Cuff inflation was performed by sound in 3 cases, by feel in 10 cases and by both sound and feel in 5 cases. A stylet was used in 15 cats and the anesthesia machine was disconnected from the endotracheal tube when the cat was turned in 15 cats.

History of inhalational anesthesia requiring endotracheal intubation with development of subcutaneous emphysema is consistent with a diagnosis of a tracheal tear. However, it is a presumptive diagnosis if not confirmed with tracheoscopy or surgery. In order to argue that these cases are indeed secondary to tracheal tear, I reviewed what literature was available in the human medical field and reviewed some discussion of tracheal related disease in the cat. Only 2 mentions of it in the cat were found in the veterinary literature and a number of cases in the human literature. Tracheal ruptures were found in humans after problems when intubating or problems encountered with the endotracheal tube cuff.

Another condition that can also result in subcutaneous emphysema is marginal alveolar rupture. It is the most common cause of subcutaneous emphysema and pneumomediastinum during assisted ventilation in humans. Marginal alveolar rupture has also been reported in 1 cat, and can cause clinical signs similar to a tracheal rupture. Positive pressure ventilation appears to be a requirement for this syndrome and clinical signs appear immediately. It is due to the response of the marginal alveoli to barotrauma where the basement membrane of the alveoli that are on the outer section of the lung become ruptured after positive pressure ventilation. The air that is released then travels up through the interstices of the alveoli and enters the mediastinum eventually resulting in pneumomediastinum as well as subcutaneous emphysema and pneumothorax. In the cats evaluated in the study reported here, only 4 were referred the same day as intubation and none had received positive pressure ventilation. Two of these 4 cats had a tracheal rupture induced by a stylet. Though the condition is similar marginal alveolar rupture is unlikely the cause of subcutaneous emphysema and pneumomediastinum in these cats as they were not positive pressure ventilated and did not present with immediate signs.

Tracheoscopy has been reported to provide an effective means of diagnosing tracheal defects. In our study tracheoscopy was not effective in diagnosing this condition. It is difficult to explain but may have been due to operator error, the precision of the scope or due to a partial seal of the tracheal disruption. Another diagnostic that could have been used would have been a tracheogram but may not be warranted if a cat is responding to medical management.

Subcutaneous emphysema is a consistent clinical sign in cats with tracheal rupture because air dissects along connective tissue planes in the cervical area surrounding the trachea and air travels into the mediastinum, which causes pneumomediastinum. Pneumothorax may develop if pressure is high enough to rupture the mediastinum. Tension pneumothorax may develop if the tracheal defect acts as a 1-way valve. Resolution of subcutaneous emphysema is slow because absorption of air is dependent on the diffusion gradient of nitrogen, and this gradient is quite small. In order to speed absorption, human patients with subcutaneous emphysema are treated with 95% oxygen for 4 hours. This treatment decreases the partial pressure of nitrogen in the blood and promotes diffusion of nitrogen from the interstitium into the blood.

In 2 cats, both referred by the same clinic, tracheal rupture was thought to be trauma-induced by a stylet. A technician at this practice used a coat hanger stylet that extended beyond the distal end of the endotracheal tube. Both of these cats subsequently died. One cat died before any treatment could be attempted; the other cat died after surgery. Although thought to be caused by the stylet, the tracheal rupture seen at surgery was identical in appearance to ruptures in other cats that were not intubated with the assistance of a stylet. It is possible that the stylet initiated the rupture, and the rupture was further propagated by the endotracheal tube cuff, or more likely, the stylet was not the cause of the tracheal rupture.

The cause of tracheal rupture in the cats of this study is unknown. Possible explanations include overinflation of the endotracheal tube cuff, change of the cat’s recumbent position without proper disconnection of the endotracheal tube from the anesthetic machine, traumatic intubation with a stylet, type of endotracheal tube used, and removal of the endotracheal tube without deflation of the cuff.

In 2 of the cats reported in this study, the veterinarians knew that the endotracheal tube cuff had been overinflated. In 1 cat, after inflation of the endotracheal tube cuff, the cuff was palpated outside the tracheal lumen. The endotracheal tube cuff was subsequently deflated and the surgical procedure was continued. This cat was admitted to an emergency clinic 5 days later. In the second cat, the veterinarian continued to hear an air leak around the endotracheal tube cuff, despite positive pressure ventilation, and therefore continued to inflate the cuff. The leak was later found to be in another part of the endotracheal tube and the tube was replaced. This cat was admitted to an emergency clinic 2 days later. Both of these cats underwent surgical repair of tracheal rupture because of worsening respiratory status and subcutaneous emphysema. All 4 cats in this study that had surgery had a tracheal rupture at a location consistent with that of the endotracheal tube cuff. On the basis of a recent study in which cadavers were used, overinflation of the endotracheal tube cuff is the most likely cause of tracheal rupture. As I previously mentioned, ruptures in humans secondary to overinflation of the endotracheal tube cuff have also been reported.

Disconnecting the endotracheal tube from the anesthetic circuit is recommended when changing an animal’s recumbent position during surgery, because rotation of the endotracheal tube and cuff could result in tracheal disruption. In this study, all except 3 referral practices reported they disconnected the anesthetic circuit when turning the cat during a procedure. This potential cause of tracheal rupture in cats, however, was not supported in a recent study.

Both high pressure, low volume (HPLV) and low pressure, high volume (LPHV) endotracheal tubes were used in the cats of this study. In general, these tubes can be identified by the appearance of the cuff as it is attached on the endotracheal tube. HPLV tubes have a cuff that lies flat on the endotracheal tube surface, whereas the cuffs on LPHV tubes are raised away from the tube. It has been reported that either tube, if overinflated, can cause tracheal rupture. Endotracheal tube usage, rather than tube type, may be more important in causing tracheal rupture. Also if the extent of cuff inflation is evaluated only by palpation of the pilot balloon, cuff overinflation is a definite possibility.

Deflation of the cuff at extubation was not assessed in this study. Extubation of the endotracheal tube with the cuff inflated is thought to help avoid aspiration of fluid and debris. A preferred technique may be to pack the oropharynx with gauze.

Most of the cats in this study were intubated for dental prophylaxis. Another article that preceded mine also evaluated tracheal rupture in cats. In this study a total of 16 cases were evaluated; nine went to surgery and 7 were treated medically. Twelve of these 16 cats with tracheal rupture that were evaluated for signs of subcutaneous emphysema had also received dental prophylaxis. Though it is possible that changes in head position during a dental procedure may cause excessive manipulation of the endotracheal tube, resulting in trauma to the trachea, in this study it was shown that this is not the case. A cadaver study also conducted by the investigators determined convincingly that the location was at the level of the cuff and due to overinflation of the cuff. They were able to rule out tracheal tears being caused by a stylet and tears being caused by twisting of the trachea as would occur with manipulation of the cat still hooked up to the anesthetic machine. Overinflation of the endotracheal tube cuff to ensure that fluid and debris is not aspirated during a dental procedure may explain why more dentals are seen with tracheal tear. Because of these findings the authors recommend careful attention being paid to endotracheal intubation and to use the method of listening for a leak as opposed to doing it by feel or appearance of the pilot balloon. In my study, it was also noted that cats receiving dental prophylaxis were older than the other cats with tracheal rupture; therefore, age may or may not be a contributing factor in the cause of this disorder.

Determination of the most appropriate treatment for cats with tracheal rupture requires serial evaluation of respiratory status and subcutaneous emphysema. Medical treatment was successful for all 15 cats with moderate signs of dyspnea and static subcutaneous emphysema. Cats with severe dyspnea, as evidenced by open-mouth breathing despite treatment with oxygen, or worsening subcutaneous emphysema, required surgery. A ventral cervical midline approach with a partial median sternotomy provided adequate exposure to the tracheal ruptures. A moderate amount of manipulation of the trachea is required to access the defect on the dorsolateral surface of the trachea. The defect can be repaired with absorbable or nonabsorbable suture in a simple continuous or simple interrupted pattern. None of the surviving cats have had respiratory problems since medical or surgical treatment of the tracheal rupture.

It is imperative that doctors and technicians be properly trained in intubation techniques, including cuff inflation and pilot balloon assessment, to ensure that cats do not sustain tracheal tears. Recommendations include the following:

1) select the largest endotracheal tube that will easily fit through the larynx and into the trachea

2) inflate the cuff in 0.5ml increments (use a 3ml syringe to prevent overzealous filling) use gentle pressure on the reservoir bag to determine if air is escaping past the endotracheal tube stop filling the cuff when there is no audible leak.


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Tracheal avulsion/rupture injuries

Postby malernee » Wed Jul 19, 2006 7:16 am

There's limited information on the incidence of trauma to the trachea caused by intubation in small animals but 100% of horses have lesions following tracheal intubation.
After tracheal avulsion cats have been reported to present in two ways (White & Milner 1995, JSAP 36, 343-347). The first is acute onset dyspnoea the second is a much more gradual onset that progresses to dyspnoea over days to weeks after the initial injury. Tattersall & Pratschke (2002) discuss the two presentations and aetiology clearly in a "What is your diagnosis?" article in JSAP p333 and 370-371. Their case presented with respiratory distress following a RTA, improved with conservative treatment, other injuries were repaired, cat only had mild repiratory signs for 2-3 weeks than became acutely dyspnoeic.

following tracheal avulsion in 9 cats reported by White and Burton (2000) in Veterinary Surgery only one was presented immediately following the injury - the others were presented up to three weeks after.

Tracheal avulsion/rupture injuries can be very difficult to diagnose initially and the tracheal lumen can be maintained by mediastinal tissue/ intact tracheal adventitia (Ryan & Smith 1972. JAVMA 1151-1152, Kennedy 1976, Veterinary Medicine, Small Animal Clinician)/
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