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INTRODUCTION
In canines a series of setbacks have been described during the intubation procedure 1,2, within which we can mention , soft palate trauma , traumatic laryngitis, tracheitis and phenomena of cerebral hypoxia delay in the procedure , these difficulties are well described in humans by the American Society of Anesthesiologists (ASA ) 3-6 and are determining when performing tracheal intubation , so it is important to define via difficult area (DAV ) , which is defined as requiring more than three attempts to intubate the trachea 7. The cause of DAV is given by anatomical factors or pathological abnormalities in face, mouth and neck 8. Some of the predictive factors for intubation described by ASA (2008) are: Mallampati, Patil-Aldreti, Cormack-Lehane and sternum chin distance 3-5,9. However, the algorithms used in humans for VAD, not been described in the canine species, the anatomical or pathological abnormalities difficult intubation are well documented in humans 10. Working with the human model may have some validity as a predictor method in animals, as a good and proven algorithm working in anesthesiology 11. It is well known that tissue damage in repeated attempts, increase the difficulty of intubation 12,13.
Mallampati is defined as the size of the tongue relative to the oral cavity 6, also evaluates pharyngeal anatomical structures and its tongue hanging out 14,15. Cormack-Lehane is scale that determines the degree of visualization of the vocal cords, the bottom of the pharynx, glottis and other laryngeal structures with the naked eye 12,16. The Patil-Aldreti assesses distance thyromental, the patient is located lateral ulna, with the head extended and mouth closed, the distance between the thyroid cartilage (top notch) and the lower edge of the chin is valued 17.
The sternum chin distance, corrected for the canine species, because the skull morphology of a canine differs distance the same as for humans, so it is remembered that this distance will be designated as profile skull 18 , this profile is based on the way they present the different types of canine skull currently in centimeters and value changes regarding the type of head, it must be remembered that there are four anatomical profiles for canines that are: lupoid, bracoides, molossoids and gradioides. The values are modified from the original human scale 19,20.
The objective of this research is to provide a description of the behavior of predictors of intubation used in human anesthesia, in canines and determine its validity.
MATERIALS AND METHODS
Type of study. A descriptive, observational, cross-sectional study in the area of surgery was taken in two veterinary clinics in Medellín, Colombia, from August 2013 to March 2014. The 74 canines consisted of 74, randomly selected, who were admitted to the surgery.
Ethical consideration. All patients signed informed consent, and received ethical endorsement at Unisabaneta No 2, July 2013.
Methods. All dogs underwent measurement Mallampati, Patil-Aldreti, Cormack-Lehane and distance esternomentoniana. The values for each score Mallampati (Table 1). Cormack - Lehane and esternomentoniana distance are described in table 2. Also was determined the general level of difficulty of intubation in points according to table 3.
Tabla 1 Predictors of intubation Mallampati and Patil-Aldreti 15.
| Name | Technique | Classification |
|---|---|---|
| Mallampati scale converted for canine. | Sternal cube patient, with mouth open, exposing the tongue forward. | Class I: soft palate visibility, visible pharynx, palatine tonsil. Class II: visibility of soft palate, hard palate, palatal ridge. Class III: soft palate decreased visibility, you only look hard palate. Class IV: Unable to see only the soft palate is the hard palate. |
| ||
| Patil-Aldreti scale (tiromentonian distance) Converted for canine. | Patient lateral ulna, head extended and mouth shut. The distance is assessed between the thyroid cartilage (top notch) and bottom of the chin | Class I:> 8 cm (laryngoscopy and endotracheal intubation without difficulty) Class II: 6-8 cm (laryngoscopy and intubation with a degree of difficulty) Class III-IV: <6 cm (laryngoscopy and difficult intubation). |
|
||
Tabla 2 Predictors of intubation Cormack-Lehane and Sternun chin distance corrected for canines 4,16.
| Name | Technique | Classification |
|---|---|---|
| Skull types (Sternum Chin Distance) | Patient laying ulna side, the jaws and jaws feature is observed, determining symmetry, sorting head according to FCI | Class I: Lupoid, easy patient intubation head similar to that of the wolves. Class II: Bracoid patient of moderate difficulty, similar to two square head. Class III: Graiodes, more complex higher intubation jaw larger than the bottom. Class IV: Molosoid, difficult intubation are brachiocephalic, lower jaw greater than the upper |
| ||
| Cormack-Lehane, classification converted for canine and feline. | Perform laryngoscopy Direct. The degree Of difficulty is assessed to achieve endotracheal intubation, depending on Anatomical structures displayed. | Grade I: glottic ring is observed in full (easy intubation) Grade II: only the corner is observed upper half of the glottic or ring (Difficult) Grade III: only epiglottis seen without displaying glottic opening (very difficult) Grade IV: inability to visualize even the epiglottis(intubation only possible with special techniques |
|
||
Table 3 Score factors intubation in canine.
| Score factors | |||
|---|---|---|---|
| Mallampati Scale-Aldreti Patil (thyromental distance) converted for canine Skull Types (Sternum chin distance) Rating Cormack-Lehane, Converted for canine. | |||
| Parameter | Value | Prediction intubation | |
| Class 1 | 2 | Easy | |
| Class 2 | 4 | Slight | |
| Class 3 | 6 | Moderate | |
| Class 4 | 8 | Difficult | |
| Total score for canines | Forecast intubation | ||
| 8 | Easily intubated | ||
| 9-16 | Slightly difficult intubations | ||
| 17-24 | Moderately difficult intubations | ||
| 25-32 | Fully difficult intubations | ||
Patients were classified into three groups according to the morphology of the skull in brachycephalic, dolichocephalic and mesocephalic. It was not taken into account variables such as age or sex. Besides all canine underwent measurement Mallampati, Patil-Aldreti, Cormack-Lehane and sternum chin distance. The values of each Mallampati score, Patil-Aldreti (Table 1), Cormack-Lehane and sternum chin distance are described in table 2.
Mallampati measurement was made with recommendations for intubation in canine, with a patient in sternal lateral ulna, open mouth, exposure of the tongue forward. The Mallampati scale allows to visualize the entire structure of the pharynx (Table 1), patients were classified as Mallampati as follows: Class I, II, III and IV 3-5,15.
The Patil-Aldreti scale was performed with a patient lateral ulna, head extended and mouth shut, was assessed the distance between the thyroid cartilage and the rostral portion of the mandibular symphysis (Table 1). Patients were classified according Patil-Aldreti like this: class I, II, III and IV see table 1 3,4,21.
It was also on the scale of Cormack-Lehane, modified for canine, where direct laryngoscopy with the patient located sternal ulna was held on difficulty achieving endotracheal intubation (Table 1) grade was assessed according to the anatomical structures that are seen. It was: grade I, II, III and IV (Table 2)16.
It was also performed the measurement of the sternum chin distance 22, edited by types of skull, patients were placed in lateral ulna, showing maxillary features and mandibular determining symmetry and were classified the types of head according to Cinologic federation international (CFI), as follows: Class I: Lupoid, easy intubation patient, similar to the head wolves, Class II bracoid patient with moderate difficulty, similar to two squares head, class III: graiodes more complex intubation, maxilla larger than the bottom and class IV, Molosoides (Table 2), very difficult intubation are brachiocephalic, higher than the top (Figure 1) lower jaw. They were measured for each type of skull, the number of intubation attempts and the time in seconds it took the right process intubation.
The degree of difficulty in intubation was measured according to the standards described by ASA, for human patients described numerical value in Table 3 and thus determining not only the degree of difficulty but which predictor is more specific for each type of canine skull.
Stactics. All data were processed according to the scales in tables in Excel© by Microsoft®; using an aleatory design completely random and a significance level of 5%. They were analyzed in the R® program, conducted an analysis of variance (ANOVA) that evaluated under the three skull morphologies considered: brachycephalic, dolichocephalic and mesocephalic and response variables: Mallampati, Patil-Aldreti, Cormack-Lehane and sternum chin distance (skull type) and their respective values. In the case of significant differences found for the values found considering the three skull morphologies proceeded to evaluate the divergence by Tukey post test. Similarly, for the different breeds of dogs assessed a principal component analysis to identify trends clustering around predictors considered intubation was developed; used for this purpose the R® version 3.1.0 software.
RESULTS
The 69.44% of patients were mesocephalic, 22.22% and 11.11% brachycephalic dolichocephalic. The most common breeds were Labrador, poodle and pinscher seven respectively. No age or gender was evaluated. A assessment Mallampati found that brachycephalic had a scale III, indicating difficulty moderate intubation, the dolichocephalic and mesocephalic segment I, easy intubation (Table 3), statistical difference was found between the brachycephalic group and dolichocephalic and mesocephalic groups (p=0.00) respectively. The mesocephalic and dolichocephalic group showed no statistically significant difference (p=0.812). In assessing the value Mallampati, brachycephalic is indicative of difficult intubation, the dolichocephalic and mesocephalic have a value of easy intubation (Table 3). Statistically significant difference between brachycephalic and dolichocephalic Mallampati value and mesocephalic brachycephalic (p=0.00) was found, but not between dolichocephalic and respetivamente mesocephalic (Table 4).
Table 4 Mean ± SD of the variables Mallampatti, Mallampatti value, Patil-Aldreti, Patil-Aldreti value, Cormack-Lehane, Cormack-Lehane value and Sternum chin distance for brachycephalic, dolichocephalic and mesocephalic skulls.
| Skull morphology | Mallampatti | Mallampatti value | Patil-Aldreti | Patil-Aldreti value | Cormack-Lehane | Cormack-Lehane value | Sternum Chin Distance |
|---|---|---|---|---|---|---|---|
| Brachicephalic | 3.37 ±0.61a | 8.00 ±0.00a | 2.93 ±0.25a | 5.87 ±0.5a | 4.00 ±0.00a | 8.00 ±0.00a | 2.12±0.80a |
| Dolichocephalic | 1.62 ±0.74b | 5.00 ±1.06b | 1.37 ±0.74b | 2.75 ±1.48b | 2.50 ±0.53b | 5.00 ±1.06b | 2.37±1.06a |
| Mesocephalic | 1.82 ±0.89b | 4.16 ±1.60b | 1.84 ±0.79b | 3.68 ±1.58b | 2.08 ±0.80b | 4.16 ±1.60b | 2.32±0.99a |
| Average values with different letters (a and b) correspond to values with statistically significant difference (p≤0.05). |
Patients evaluating Cormack-Lehane had a class IV for brachycephalic, indicative of difficult intubation, dolichocephalic and mesocephalic class II, mild difficulty of intubation (Table 3); significant statistical difference when comparing, brachycephalic and each group was found (p=0.00), but no difference was found dolichocephalic and mesocephalic. In measuring value Cormack-Lehane found that brachycephalic present difficult intubation (Table 4), dolichocephalic and mesocephalics submit predictor with slight difficulty intubation statistically significant difference was found between the Cormack-Lehane value between brachycephalic and dolichocephalic and mesocephalic respectively (p=0.00). There is no difference in value Cormack-Lehane between dolichocephalic and mesocephalic.
In assessing Patil-Aldreti, brachycephalic showed a class III, indicating difficult moderate intubation while dolichocephalic and mesocephalic exhibit class II slight difficulty of intubation, statistically significant difference (p=0.005) was presented, among dolichocephalic brachycephalic and mesocephalic, no difference was found between mesocephalic and dolichocephalic. For Aldreti Patil-value statistically significant difference between brachycephalic and brachycephalic mesocephalic and dolichocephalic (p=0.00) was also found, brachycephalic continued with moderate difficulty and dolichocephalic and mesocephalic, with slight difficulty (Table 4).
To evaluate the sternum chin distance (type of skull), it could not be determined statistically significant difference (Table 4), for none of the three groups in evaluation. We found that according to this predictor all patients have an easy intubation.
The evaluation of each of the predictors through the matrix of principal components, it was stablished that the breeds dogs English Bull dog, French Bulldog, Boston Terrier and Pug, are predicted in the difficult intubation by Mallampati and Patil-Aldreti, this coincides with the brachycephalic cranial morphology, whereas patients, Labrador, Golden Retriever, Dalmatian, Fox terrier Breeds, are correctly predicted with Cormack-Lehane, for the type of dolichocephalic and mesocephalic head. Dogs of mixed races, Pinscher and Pitbull, are not predicted by any of the factors, it means their intubation is easy and is not determined by any of the aforementioned predictors (Figure 2).
According to the scale score of intubation which are described in Table 3, patients with easy intubation have 8 points 9-16 slight difficulty 17-4 25-32 moderate difficulty and high difficulty, found that 10 patients (13.51%) have all difficult intubation with over 25 points score, of which 7 (70%) are brachycephalic, 28 patients (37.83%) were found in score between 17-24 points indicated moderately difficult intubation, 5 (17.85%) are dolichocephalic, 9 (32.14%) and 14 brachycelphalic (50%) mesocephalic. Patients that had slight difficulty in intubation were 35 (47.29%), of which 6 (17.14%) are dolichocephalic and 29 (82.85%) are mesocephalic, finally just a brachycephalic patient (1.35%) had easy intubation.
It was found that the average number of intubations was 1.83 1-2 attempts, It distributed in brachycephalic 3 2-4 attempts mesocephalic 1.56 1-2 and 1.25 1-2 attempts to dolichocephalic, statistical difference (p<0.05) for brachycephalic dogs and the other two groups, mesocephalic between dolichocephalic and no statistical difference. Regarding the average time taken to intubation, an average of 126.43 seconds in brachycephalic represented 222.25 sec, sec mesocephalic 104.22 and 73.62 seconds respectively dolichocephalic was found.
DISCUSSION
Related to the results it was found that the most common breeds in surgery were the Labrador Pinscher and Poodle, being the most abundant races in the study area, although the presence of significant breed dogs like English and French bull dog, that are habitually subjected to surgery, where the imminent intubation is required.
We found that brachycephalic dogs are those with more difficult intubation, which corresponds with the findings of doctors for this type of skull, but the findings were only anecdotal and had no scientific basis, differs with the descriptions, which describe this unusual complication in a Dog Kerry Blue Terrier, considered within the dolichocephalic race 2.
Compared to descriptions in humans, where patients with Mallampati III, with moderate difficulty of intubation 10,23-25, have brachycephalic difficult intubation. Regarding this finding the explanation is based on brachycephalic patients have a soft palate so elongated, which was frequently introduced to the entrance of the glottis 26, which precludes observation satellite breathing. In assessing the Mallampati scale confirmed that the type of mouth is brachycephalic class III, preventing the display of respiratory structures, with a language which makes the observation from the bottom of the larynx. Brachycephalic patients shown to be sensitive predictor Mallampati factor, and to assess the main components found that the sampled individuals from breeds such as Bull Dog English Bull dog French, Pug, Shi Tzu and Boston terrier, are represented by that test. That is to say, there is a probable relationship between dogs and brachycephalic head Mallampati. A finding not described in the literature. The evaluation could also be seen as a trend that breeds mesocephalic and dolichocephalic type are not predicted by Mallampati, so using this predictor is little useful in this type of skull.
The predictor Patil-Aldreti is also indicator in brachycephalic breeds, index of difficult intubation, while other breeds dolichocephalic and mesocephalic type are of easy intubation, this because thyromental distance measurement, which certainly is modified in brachycehalic patients, which have a distance from the lower superior to those described for the other skull types . Therefore not only the Patil-Aldreti but his value scale are predictors in breeds brachycephalic head, indicating that they have difficult intubation, in human patients it has been reported that people with prognathism present greater difficulty of intubation 8,27,28.
Measurement of the Cormack-Lehane scale, although is indicative of difficult intubation for brachycephalic patients for the same anatomical structure of the soft palate 26, proved to be presumably a factor more predictor in dolichocephalic and mesocephalic patients, which means that using Cormack-Lehane, is important in this kind of races.
As the number of intubation attempts could corroborate that brachycephalic dogs require more intubation attempts with an average of 3 trials is consistent with the findings to be patients with difficult intubation, both dolichocephalic and mesocephalic require values between 1 and 2 attempts, which makes them easy intubation dogs. brachycephalic dogs take longer to be intubated, with an average value of 222.25 sec, which corroborates the hypothesis that canines are difficult intubation, shown in patients who require 3-4 minutes to be intubated, leading to greater risk of cerebral hypoxia, similar to what is described in humans.
Finally it was found that breeds like Poodles, Doberman, Schnauzer and corssbreed are not represented by any of the considered predictor, probably reflecting how easy it was the intubation of such individuals.
In conclusion his type of models and predictory descriptions are underdeveloped in veterinary medicine; this work in the context of generating conceptual intubation in dogs elements what looks for is to create its own veterinary system according to anatomical and morphological factors of canine spice, thus predicting the easiness of intubation, based on parameters established for the human species.
