Kinking of endotracheal tubes during maxima flexion of the atlanto-occipital joint in dogs

Endotracheal tubes manufactured from red rubber and polyvinyl chloride (PVC) were compared, using radiographic techniques, in dog cadavers, under in vitro conditions and in anaesthetised dogs (in vivo study). All endotracheal tubes were radiographed in 'neutral' and flexed positions and the percentage reduction in the ventrodorsal radiographical diameter of the tube was calculated. The red rubber tubes kinked completely in 40 per cent of the cadavers, 75 per cent of the in vitro study and 40 per cent of anaesthetised dogs. The PVC tubes kinked completely in only one case (in vivo study). However, these tubes had a mean reduction in diameter of 15 per cent in the dog cadaver study, 19 per cent in the in vitro study and 26 per cent in the in vivo study. During procedures in which the trachea is intubated and the atlanto-occipital joint of the patient must be flexed, PVC endotracheal tubes may be less prone to kinking than red rubber tubes.     

The effects of extubation with an inflated versus deflated endotracheal tube cuff on endotracheal fluid volume in the dog

Objective The purpose of this study was to investigate the effect of extubation with the endotracheal tube (ETT) cuff inflated versus deflated on endotracheal fluid volume in normal canine cadavers. Study Design Prospective randomized blinded controlled cadaver study. Animals Sixteen adult Beagle cadavers weighing 10.7 ± 1.7 kg (mean ± SD) and <2 years of age. Methods Cadavers were orotracheally intubated in lateral recumbency, and the ETT cuffs were inflated to a closing pressure of 20 cm H₂O before barium was introduced orad to the cuff. The dogs were randomly assigned to an ETT cuff extubation condition of deflated or unchanged from the original closing pressure. After extubation, lateral thoracic radiographs of the cadavers were obtained and scored by three independent blinded reviewers. Each reviewer ordered all 16 lateral radiographs from most to least intratracheal contrast and also estimated residual intratracheal contrast volume. Results Dogs extubated with a deflated ETT cuff had a median rank of 13 and dogs extubated with an inflated ETT cuff had a median rank of 4.5 (p < 0.0001). Dogs extubated with a deflated ETT cuff had an estimated intratracheal volume of fluid of 1.8 mL ± 0.7 mL (mean ± SD) and dogs extubated with an inflated ETT cuff had an estimated volume of 0.9 mL ± 0.5 mL (p < 0.0001). Fleiss Kappa for agreement among evaluators was 0.875. Conclusions and clinical relevance Extubation with the cuff inflated removed more liquid contents from the trachea than extubation with the cuff deflated and may assist in the prevention of pulmonary aspiration when fluid is present in the proximal trachea. The technique did not remove all fluid so the potential for pulmonary damage remains.     

Evaluation of two methods of endotracheal tube selection in dogs

This study evaluated two methods of endotracheal tube selection using 28 fresh canine carcasses of various ages, weights, and genders. The two selection methods were 1) nasal septal width pairing with outer diameter of an endotracheal tube, and 2) digital palpation of the tracheal outer diameter to determine the endotracheal tube size. All dogs were dolichocephalic breeds. Results of this study showed that the canine nasal septal width method of endotracheal tube selection was correlated with the size of the tracheal internal (r=0.72) and outer (r=0.73) diameters. However, evidence shows that the digital palpation method is slightly more effective than the nasal width method in selecting the best-fitting endotracheal tube. The percentage of the best-fit tube selection for the nasal septal width method was 21%, while the digital palpation method was 46%. With these two methods, selecting an endotracheal tube that is too small is possible, especially when the tube internal diameter is > or =7 mm.     

Fragments of nasogastric tubes as esophageal foreign bodies in two horses

Two horses were referred with fragments of nasogastric tubes as esophageal foreign bodies. Radiography and endoscopy were used to identify the location of the fragments. Portions of the tubes were retrieved by esophagotomy in 1 horse and by manual examination of the oral cavity in the other. Both tubes were friable in focal areas, but were quite pliable over most of the length of the tube.     

The effects of two endotracheal tube cuff inflation pressures on liquid aspiration and tracheal wall damage in horses

OBJECTIVE: To investigate the effect of endotracheal tube cuff inflation pressure on the occurrence of liquid aspiration and tracheal wall damage. STUDY DESIGN: Prospective, randomized experimental study. ANIMALS: Ten healthy horses, weighing 535 +/- 55 kg. METHODS: Horses were anesthetized, orotracheally intubated, placed in dorsal recumbency, and maintained on isoflurane in oxygen with controlled ventilation for 175 +/- 15 minutes. The horses were randomly assigned to an endotracheal cuff pressure of 80-100 or 120 cm H2O. The cuff pressure was continuously monitored and maintained at a constant pressure. Methylene blue in saline was instilled proximal to the cuff. After euthanasia, the trachea was opened distal to the endotracheal tube tip to check for evidence of dye leaking past the cuff. The cervical trachea was then resected and opened longitudinally for gross and histologic examinations. RESULTS: No blue staining was found distal to the cuff in any horse. Visual examination of the tracheal mucosa revealed hyperemic and hemorrhagic lesions at the site of the cuff contact. Histologic changes included epithelium attenuation or erosion, submucosal neutrophilic infiltration, and submucosal hemorrhages. Lesions were absent or less extensive in the lower cuff pressure group as compared to the high cuff pressure group. CONCLUSIONS: The endotracheal tube cuff produced a seal sufficient to prevent leakage in both groups. Tracheal wall damage was more severe and occurred more frequently in the higher cuff pressure group. CLINICAL RELEVANCE: Tracheal mucosal damage induced by cuff inflation is pressure-dependent. Cuff pressure monitoring is recommended.     

Near-fatal misuse of medical tape around an endotracheal tube connector during inhalation anesthesia in a horse

A 7-year-old gelded Irish sports horse weighing 650 kg was anesthetized on 2 consecutive days for lavage of a septic right radio-carpal joint. On both occasions the endotracheal tube connector, which had been bound in medical tape to produce an airtight seal, functioned as a unidirectional valve during mechanical ventilation, retarding expiration, imposing positive end expiratory pressure (PEEP), and probably continuous positive airway pressure (CPAP). The equipment dysfunction was not identified on either occasion despite close inspection prompted by progressive increases in airway pressure and thoracic distension. Whilst the PEEP and CPAP exerted unexpectedly modest cardiovascular effects and the horse recovered uneventfully on both occasions, the improvisation may have proven fatal in a higher-risk subject.     

Comparison between intravenous lidocaine and fentanyl on cough reflex and sympathetic response during endotracheal intubation in dogs

ObjectiveTo compare the effects of intravenous (IV) lidocaine and fentanyl on the cough reflex and autonomic response during endotracheal intubation in dogs.Study designRandomized, blinded, superiority clinical trial.AnimalsA total of 46 client-owned dogs undergoing magnetic resonance imaging.MethodsAfter intramuscular methadone (0.2 mg kg^–1), dogs were randomized to be administered either IV lidocaine (2 mg kg^–1; group L) or fentanyl (7 μg kg^–1; group F). After 5 minutes, alfaxalone was administered until endotracheal intubation was possible (1 mg kg^–1 IV over 40 seconds followed by 0.4 mg kg^–1 increments to effect). Total dose of alfaxalone was recorded and cough reflex at endotracheal intubation was scored. Heart rate (HR) was continuously recorded, Doppler systolic arterial blood pressure (SAP) was measured every 20 seconds. Vasovagal tonus index (VVTI) and changes (Δ) in HR, SAP and VVTI between pre-intubation and intubation were calculated. Groups were compared using univariate and multivariate analysis. Statistical significance was set as p < 0.05.ResultsGroup F included 22 dogs and group L 24 dogs. The mean (± standard deviation) alfaxalone dose was 1.1 (± 0.2) and 1.35 (± 0.3) mg kg^–1 in groups F and L, respectively (p = 0.0008). At intubation, cough was more likely in group L (odds ratio = 11.3; 95% confidence intervals, 2.1 – 94.2; p = 0.01) and HR increased in 87.5% and 54.5% of groups L and F, respectively (p = 0.02). The median (range) ΔHR between pre-intubation and intubation was higher (13.1%; – 4.3 to + 55.1) in group L (p = 0.0021). Between groups, SAP and VVTI were similar.Conclusion and clinical relevanceAt the stated doses, whilst reducing the alfaxalone dose, fentanyl is superior to lidocaine in suppressing the cough reflex and blunting the increase in HR at endotracheal intubation in dogs premedicated with methadone.     

Cardiac arrest during anaesthesia in two horses

Unexpected cardiac arrest occurred in two horses during routine surgical anaesthesia. Both were successfully resuscitated. The aetiology of these occurrences and their possible relationship to second degree heart block is discussed.     

Blood of two siluroid fishes during different respiratory conditions

In the present study an attempt has been made to investigate the changes in different blood parameters in two siluroid fishes, Heteropneustes (H.) fossilis. Bloch and Clarias (C.) batrachus. Linn, both air breathing fishes, during different respiratory conditions, Viz, 1. normal, 2. submerged water condition and 3. exclusive air breathing condition. An increase in different blood parameters [Viz, red blood corpuscles (RBC) counts, haemoglobin (Hb) content and packed cell volume (PCV) etc.] was observed under submerged water and exclusive air breathing conditions. Possible reasons and the mechanism of such changes in different blood parameters have been discussed.     

Gastro-oesophageal reflux during anaesthesia in the kitten: comparison between use of a laryngeal mask airway or an endotracheal tube

Objective  To compare the incidence of gastro-oesophageal reflux (GOR) during anaesthesia in the kitten when using a laryngeal mask airway (LMA) or an endotracheal tube (ET).
Study design  Prospective randomized cross-over experimental study.
Animals  Forty Domestic Short Hair laboratory cats, 19 females and 21 males, aged 12–15 weeks and weighing 0.57–1.73 kg (mean 1.13 ± SD 0.26).
Methods  Kittens were anaesthetized twice, once using the LMA and once the ET. Following induction of anaesthesia with isoflurane in an anaesthetic chamber and intubation of the trachea with the ET or placement of the LMA, a pH-electrode was introduced into the lower oesophagus. Monitoring of the oesophageal pH was performed for 45 minutes while anaesthesia was maintained with isoflurane. At the end of the experiment, gastric pH was measured. Kittens that had GOR during the experiment were treated with sucralfate, cisapride and ranitidine for 15 days.
Results  Oesophageal pH was 6.51 ± 0.76 and gastric pH was 1.54 ± 0.59. GOR was observed in nine kittens when the ET was used, and in 20 kittens when the LMA was used, the difference being significant ( p  =   0.013). The refluxate nearly always was acidic, being alkaline in only one kitten. Most of the GOR episodes occurred shortly after induction of anaesthesia and the oesophageal pH remained below 4.0 until the end of the experiment. No regurgitation was observed.
Conclusions and clinical relevance  The use of the LMA is associated with an increased incidence of GOR during anaesthesia in the kitten, which is not detected by observation. That this may have occurred should be considered if the kitten demonstrates signs of oesophagitis in the postoperative period.     

Comparison of endotracheal intubation techniques in llamas

This study evaluated a retrograde orotracheal intubation technique and compared it to the traditional normograde intubation technique used in llamas. Oral anatomical features, which can impair visualization of the epiglottis and laryngeal structures, and the production of excessive salivary secretions make it difficult to establish an airway under emergency conditions. Normograde intubation involves placing a stylet through the mouth into the trachea and advancing the endotracheal tube over the stylet into the trachea. For retrograde intubation, a nested trochar with cannula is placed into the cervical trachea and a stylet is advanced through the cannula and out the mouth. The endotracheal tube is advanced over the stylet back into the trachea. Our evaluation of both techniques found no statistical difference in time to place the stylet or endotracheal tube; however, fewer attempts were needed to place the tube using the retrograde technique. We found the retrograde technique to be a viable option for intubating llamas.     

Tracheal necrosis as a fatal complication of endotracheal intubation

This case report describes the death of a yearling Thoroughbred colt due to segmental severe necrotising tracheitis with stenosis of the tracheal lumen, 19 days after endotracheal intubation for elective endoscopic surgery. The stenosis of the trachea leading to asphyxiation was caused by an inflammatory process accompanied by massive accumulation of necrotic material, fibrinous inflammatory exudate, oedema and granulation tissue. The cause of this inflammation was likely to be a bacterial infection secondary to traumatic damage of the tracheal mucosa. Given the clinical history and location of the lesion, the endotracheal tube used for general anaesthesia was hypothesised to be responsible for this damage. Delayed tracheal necrosis as a fatal complication of endotracheal intubation has not previously been described in the horse and should be considered as a potential catastrophic consequence following relatively innocuous clinical signs.     

Breakage and deformation characteristics of hypodermic devices under static and dynamic loading

OBJECTIVE: To characterize the strength and limitations of hypodermic needles to reduce the risk of leaving broken needles in the flesh of animals. SAMPLE POPULATION: Skin of porcine cadavers. Procedure-Stainless steel needles of various gauges combined with aluminum and plastic hubs were subjected to standard test-stand conditions to compare strength under various loading regimens. A device that simulated animal motion was constructed to test breakage characteristics during animal movement. RESULTS: Needles and needle/hub assemblies were resilient to needle breakage, except when bent needles were straightened and a load reapplied. Needle gauge and length drastically affected strength. For 16-and 20-gauge needles, a 1.0-in needle was 1.6 times stronger than a 1.5-in needle. Adding animal movement for 20-gauge, 1.5-in needles resulted in a 40% increase in hub failures for plastic, compared to aluminum hub needles. CONCLUSIONS AND CLINICAL RELEVANCE: Findings of this study are important considerations for meat packers to address in their Hazard Analysis and Critical Control Points plans.