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Oral intubation using a lighted stylet vs direct laryngoscopy in older children with cervical immobilization.

OBJECTIVE: To compare the tracheal intubation success rates of blind oral intubation using a lighted stylet vs standard of direct laryngoscopy in anesthetized pediatric patients wearing rigid cervical collars. METHODS: Seventy-eight children were randomly assigned to method of intubation (lighted stylet or direct laryngoscopy) and intubator; five patients were excluded after randomization. After sedation and paralysis, the patients were placed in rigid cervical spine collars to simulate intubating conditions for trauma patients. Three attempts at intubation were allowed. An observer recorded the following parameters during the procedure: 1) number of intubation attempts, 2) duration of each intubation attempt, and 3) complications. The intubators had limited prior experience with the lighted stylet technique. RESULTS: Thirty-three patients were in the lighted stylet group and 40 were in the laryngoscopy group. The patients in the lighted stylet group required more attempts prior to successful intubation (2.2 vs 1.5, p < 0.01), and the success rate was higher for the laryngoscopy group (26/33 vs 39/40, p < 0.05). CONCLUSIONS: Blind oral intubation using a lighted stylet under controlled conditions took longer than direct laryngoscopy. However, among those successful on the first intubation attempt, the times to intubation were not significantly different between groups (44.5 vs 52.9 sec). The lighted stylet technique is a viable alternative technique for intubating children who have concurrent cervical spine immobilization.

Adolescent↗

The predictive value of the height ratio and thyromental distance: four predictive tests for difficult laryngoscopy.

Preoperative evaluation of anatomical landmarks and clinical factors help identify potentially difficult laryngoscopies; however, predictive reliability is unclear. Because the ratio of height to thyromental distance (RHTMD) has a demonstrably better predictive value than the thyromental distance (TMD), we evaluated the predictive value and odds ratios of RHTMD versus mouth opening, TMD, neck movement, and oropharyngeal view (modified Mallampati). We collected data on 550 consecutive patients scheduled for elective-surgery general anesthesia requiring endotracheal intubation and then assessed all five factors before surgery. An experienced anesthesiologist, not apprised of the recorded preoperative airway assessment, performed the laryngoscopy and grading (as per Cormack and Lehane's classification). Difficult laryngoscopy (Grade 3 or 4) occurred in 69 patients (12.5%). RHTMD had a higher sensitivity, positive predictive value, and fewer false negatives than the other variables tested. In the multivariate analysis, three criteria were found independent for difficult laryngoscopy (neck movement < or =80 degrees; Mallampati Class 3 or 4, and RHTMD > or =23.5). The odds ratio (95% confidence interval) of the RHTMD, Mallampati class, and neck movement were 6.72 (3.29-13.72), 2.96 (1.63-5.35), and 2.73 (1.14-6.51), respectively. The odds ratio for RHTMD was the largest and thus may prove a useful screening test for difficult laryngoscopy.

Adult↗

Transnasal laryngoscopy for the diagnosis of laryngeal paralysis in dogs.

Four dogs with clinical signs of laryngeal paralysis and three normal dogs were evaluated with transnasal laryngoscopy. Six of these dogs subsequently underwent standard laryngoscopy. For transnasal laryngoscopy, a video endoscope was passed through the left nasal passage after intramuscular sedation and topical anesthesia. The laryngeal opening was observed during spontaneous ventilation. Laryngeal paralysis was diagnosed in four dogs and was confirmed with traditional laryngoscopy in three dogs. Normal motion of the arytenoid cartilages was present in the other three dogs; however, two required mechanical stimulation of the laryngeal mucosa for full evaluation. Transnasal laryngoscopy provided a means for diagnosing laryngeal paralysis in dogs without general anesthesia.

Anesthesia, General↗

The palm print as a sensitive predictor of difficult laryngoscopy in diabetics: a comparison with other airway evaluation indices.

AIMS: To evaluate the ink impression made by the palm of the dominant hand as a screening tool for difficult laryngoscopy in diabetic patients. SUBJECTS AND METHODS: In this prospective study, airway of 50 adult diabetic patients, undergoing elective surgery under general anaesthesia, was assessed preoperatively using the common clinical indices such as Modified Mallampati test, thyromental distance, degree of head extension and a specific index- the palm print test. Following induction of anaesthesia and neuromuscular relaxation, laryngoscopy was performed and the laryngoscopic view scored. The sensitivity, specificity and positive predictive value of each airway evaluation index were calculated. RESULTS: The incidence of difficult laryngoscopy was 16%. The palm print test had the highest sensitivity (75%) of all the indices. The thyromental distance less than six cm had the highest specificity (95.2%) but was least sensitive (25%). 87% of patients with difficult laryngoscopy had two or more indices abnormal. CONCLUSION: Though the palm print test was the most sensitive index of the four indices studied, a better prediction of difficult laryngoscopy can be achieved by evaluating all the four airway indices preoperatively.

Dermatoglyphics↗

Second dose thiopentone attenuates the haemodynamic response to laryngoscopy and intubation.

The study was undertaken to evaluate the effectiveness of large (divided) thiopentone dosage on the peripheral haemodynamic response to laryngoscopy and intubation. Seventy-six (76) patient aged 18 to 67 years were sequentially assigned to either the second dose thiopentone group (n = 36) or the control group (n = 40). The first group had 4 mg.kg-1 thiopentone for induction of anaesthesia, then 1.5 mg.kg-1 suxamethonium chloride for muscle relaxation and a second dose of thiropentone (4 mg.kg-1) just before laryngoscopy and intubation. The control group had thiopentone 4 mg.kg-1 for induction of anaesthesia, suxamethonium 1.5 mg.kg-1 for muscle relaxation and then laryngoscopy and intubation. The heart rate (HR), systolic arterial pressure (SAP), diastolic arterial pressure (DAP), mean arterial pressure (MAP), and rate pressure product (RPP) were measured before induction of anaesthesia and after laryngoscopy and intubation. The difference in the values represented the haemodynamic response to laryngoscopy and intubation. The second dose thiopentone technique compared with the control group, significantly attenuated the post-intubation rise in HR (19.7 vs. 30.9), SAP (18.0 vs. 37.5) and RPP (4795.4 vs. 8440.0). The post intubation rise in DAP (33.9 vs. 42.5) and MAP (31.9 vs. 42.0) didn't show significant difference between the two groups.

Adolescent↗

Laryngeal and hypopharyngeal carcinoma: comparison of helical CT multiplanar reformation, three-dimensional reconstruction and virtual laryngoscopy.

OBJECTIVE: To evaluate the clinical application of helical CT multiplanar reformation (MPR) three-dimensional reconstruction (3D) and virtual laryngoscopy (CTVL) in laryngeal and hypopharyngeal carcinoma. METHODS: Axial helical CT scans were performed in 22 patients with laryngeal or hypopharyngeal carcinoma, along with MPR, 3D and CTVL. These results were compared with the findings of fiber optic laryngoscopy and surgery. RESULTS: Combining axial and MPR images, both the accuracy in preoperative tumor staging and the diagnosis of metastatic lymph nodes were 95%. MPR demonstrated more information about the extent of tumor than axial images in 23% cases; 3D image displayed clearly the extension of tumor, the vessels and airway from multiple views. The location, size and extent of tumors found in cranio-caudal CTVL corresponded well with that of laryngoscopy, and CTVL demonstrated the relationship between the tumor and vocal cords and anterior commissure by caudo-cranial approach, which was inaccessible to fiber optic laryngoscopy in 3 cases. CONCLUSIONS: Axial images of helical CT clearly demonstrate the location, size and extent of laryngeal and hypopharyngeal carcinoma, while MPR and 3D images are useful in displaying the three-dimensional images and anatomical relation of the tumor. CTVL can clearly display the mucosal surface structures of the larynx and hypopharynx and is a good complementary method of laryngoscopy.

Adult↗

Effect of controlled hyperventilation on the pressor response to laryngoscopy and tracheal intubation.

Pressor response to laryngoscopy and tracheal intubation includes rises in blood pressure and heart rate. This response may be harmful in the presence of cerebral or myocardial diseases. Although different preventive measures have been developed the choice of the agent or method has not been defined clearly. Hypocapnia is commonly used in anesthesia practice for different indications. It depresses the cardiovascular system and lowers the cardiac output. This study investigated the effect of controlled hyperventilation on the pressor response to laryngoscopy and tracheal intubation in three groups of healthy adult patients with different levels of end tidal CO2. The blood pressure and heart rate were recorded during induction of general anesthesia before and after laryngoscopy and tracheal intubation. The pressor responses to laryngoscopy and tracheal intubation in hypocapnic and normocapnic groups were comparable. Moderate degrees of controlled hyperventilation caused relatively more fluctuation in blood pressure during induction of anesthesia. It can be concluded that controlled hyperventilation has no beneficial effect upon the pressor response to laryngoscopy and tracheal intubation.

Adult↗

[Effects of clonidine premedication upon hemodynamic changes associated with laryngoscopy and tracheal intubation].

The authors studied 30 patients undergoing general anesthesia in order to evaluate whether oral clonidine premedication could attenuate the hemodynamic changes associated with laryngoscopy and tracheal intubation. Patients were randomly assigned to one of two groups; clonidine group (n = 15) who received oral clonidine of approximately 5 micrograms.kg-1, or control group (n = 15) who received no clonidine. The magnitude of increases in mean blood pressure from baseline values following laryngoscopy and tracheal intubation in the clonidine group was significantly smaller as compared with that in the control group (20 +/- 12 vs. 31 +/- 14 mmHg, mean +/- SD, P less than 0.05). There was also a significant difference between the two groups in the incidence of systolic blood pressure increases above 180 mmHg following laryngoscopy and tracheal intubation (0% vs. 26%, P less than 0.05). However, no significant difference was noted between the two groups in the heart rate responses to laryngoscopy and tracheal intubation. It is concluded that oral clonidine of 5 micrograms.kg-1 as a preanesthetic medication could attenuate the pressor responses associated with laryngoscopy and tracheal intubation.

Administration, Oral↗

Difficult laryngoscopy and diabetes mellitus.

The incidence of difficult laryngoscopy was determined retrospectively in 40 diabetic patients having pancreas transplantations and in 75 diabetic and 112 nondiabetic patients having kidney transplantations. Diabetes was associated with a significant increase in the proportion of patients having difficult laryngoscopies in patients having renal transplants: 0.027 in patients without diabetes; 0.320 in patients with diabetes. The incidence of difficult laryngoscopy in diabetic recipients of cadaveric kidneys (0.419) was not significantly different from that in diabetic recipients of pancreas transplants (0.40), but significantly higher than that in diabetics given kidneys from living donors (0.187). Although cadaveric recipients were older than recipients of kidneys from living donors (40.8 v. 31.6 years), age at the time of transplantation was not a significant predictor of difficulty in laryngoscopy. Groups were otherwise matched for clinical, morphologic, hematologic, and biochemical indices. Diabetic stiff joint syndrome (SJS), which predisposes a subset of Type I diabetic patients to rapidly progressive microvascular disease and subsequent need for renal and/or pancreas transplantation, may lead to difficult laryngoscopy because of involvement of the atlanto-occipital joint.

Diabetes Mellitus↗

Arterial oxygenation during laryngoscopy and intubation.

Arterial oxygenation during laryngoscopy and tracheal intubation was studied in 37 patients, 22 taking four maximally deep breaths of O2 within 30 seconds, and 15 breathing air immediately before anesthetic induction. In both groups of patients induction was followed by ventilation with 100% O2 by face mask before laryngoscopy, which was followed by intubation. Both mean arterial O2 tension (PaO2) and mean arterial O2 content (CaO2) increased significantly after four breaths of O2 in 30 seconds (339 +/- 34 (SD) vs 77 +/- 5, p less than 0.05, and 19.6 +/- 2.1 vs 18.8 +/0 2.1, respectively, p less than 0.05). At the end of laryngoscopy, mean PaO2 remained significantly greater in preoxygenated patients than in air-breathing patients (353 +/- 33 torr vs 319 +/- 26 torr, respectively, p less than 0.05). After intubation, mean PaO2 in preoxygenated patients remained higher than in air-breathing patients (332 +/- 34 vs 289 +/- 23 torr, p less than 0.05). Calculated mean CaO2 was not significantly different for the two groups during either maneuver. We conclude that four breaths of O2 in 30 seconds before anesthetic induction elevates PaO2 but provides insignificant improvement in CaO2 during laryngoscopy and intubation when the anesthetic routine includes ventilation of the patient with O2 by face mask after induction and before laryngoscopy.

Adult↗

[Relationship between laryngoscopy degree and intubation difficulty].

OBJECTIVES: To determine the relation between difficult intubation and grade of direct laryngoscopy, as well as the factors that influence them, and prognosis. PATIENTS AND METHOD: In 1,336 patients receiving general anesthesia, seven airway measurements were made to reflect degree of difficulty and predictive value of presurgical tests on direct laryngoscopy and intubation. RESULTS: The incidences of difficult laryngoscopic and intubation procedures were 1.4 and 3.0%, respectively. Difficult intubation was more frequent in women and in patients between 40 and 65 years of age (p < 0.05). In 105 intubations (64.8%) performed with moderate difficulty (use of a stylette, external laryngeal pressure or two tries) and 17 (41.5%) performed with difficulty (three or more tries), the laryngoscopic procedure was graded as easy (Cormack-Lehane grade I-II). In these cases (easy laryngoscopy with moderate/difficult intubation), the causes recorded were size of endotracheal tube in comparison with the laryngeal opening (n = 11); anterior glotis (n = 36); insufficient relaxation (n = 31); disease in or beyond the vocal cords (n = 29); or undetermined (n = 15). In the easy intubation cases, the laryngoscopic procedures were grade III in 2.9%. Intubation was difficult in 16.3% (n = 39) of patients presenting some type of abnormality upon examination of the airway (p < 0.05). The airway characteristic that best predicted laryngoscopic difficulty was extension of the lower neck to 90 degrees (relative risk of 4.46), mouth opening less than 3.5 cm (3.92), presence of two airway abnormalities (4.25) and presence of three or more abnormalities (5.39) (p < 0.01). CONCLUSION: The fact that cases of easy laryngoscopy coincide with difficult intubation suggests that, to the degree of intubation difficulty must be added extrinsic factors (individual skill, maneuvers performed, instrumentation, relaxation of the laryngeal musculature and others) that are hard to standardize and reflect when predicting an intubation by the grade of difficulty in laryngoscopy.

Adolescent↗

[Which laryngoscope is the most stressful in laryngoscopy; Macintosh, Miller, or McCoy?].

Stress responses during laryngoscopy were compared among the situations using three different laryngoscopes, Macintosh (curved standard blade), Miller (straight blade), or McCoy (levering). Blood pressure, heart rate (in 58 patients) and plasma concentration of catecholamines (in 29 patients) were measured before, during and after laryngoscopy without tracheal intubation. Systolic blood pressure after laryngoscopy was significantly higher in the Miller group than in other two groups. Plasma epinephrine concentrations after laryngoscopy in the McCoy group were lower than other two groups. Heart rate and plasma norepinephrine concentration were not different among the three groups. These results suggest that the stress response during laryngoscopy without intubation is the biggest in using the Miller laryngoscope and the smallest in using the McCoy laryngoscope.

Adolescent↗

Skin vasomotor reflex induced by laryngoscopy: comparison of the McCoy and Macintosh blades.

We studied 22 female patients (ASA I or II) to investigate if laryngoscopy and intubation induced the skin vasomotor reflex (SVmR), and to compare the effects of the McCoy and Macintosh blades on the SVmR. Anaesthesia was induced with fentanyl, midazolam, vecuronium and nitrous oxide. In 11 patients, the vocal cords were seen for 3 s with the McCoy blade. Two minutes later, laryngoscopy was performed with the Macintosh blade and the trachea was intubated. In the other 11 patients, the first and second laryngoscopies, respectively, were performed with the Macintosh and McCoy blades. Laryngoscopy alone and intubation with laryngoscopy significantly reduced skin blood flow in the ring finger of all patients (P < 0.01), indicating that both procedures provoked the SVmR. The magnitude of the SVmR and haemodynamic changes did not differ significantly between the two groups.

Adult↗

Predictive models for difficult laryngoscopy and intubation. A clinical, radiologic and three-dimensional computer imaging study.

PURPOSE: To identify the variables most useful in predicting difficult laryngoscopy and intubation from various clinical, skeletal (lateral x-rays) and soft tissue (three-dimensional computed tomography imaging) measurements. METHODS: Twenty-four adult patients in whom an unanticipated difficult tracheal intubation was identified according to established criteria were evaluated. Further, a control group of 32 patients in whom tracheal intubation was easily accomplished was studied. We applied multivariate discriminant analysis to clinical and radiological data of all patients to select those variables most useful in predicting difficult laryngoscopy and intubation. The receiver operating characteristic (ROC) curve was used to describe the discrimination abilities and to explore the trade-offs between sensitivity and specificity of the model. RESULTS: With the clinical data alone, discriminant analysis identified four risk factors that correlated with the prediction of difficult laryngoscopy and intubation: thyrosternal distance, thyromental distance, neck circumference and Mallampati classification. With both clinical and radiological data, discriminant analysis identified five risk factors: thyrosternal distance, thyromental distance, Mallampati classification, depth of spine C2 and angle A (the most antero-inferior point of the upper central incisor tooth). The positive predictive value of this combined (clinical and radiological) model was greater than that of the clinical model alone (95.8% vs 87.5%, respectively). The areas under the ROC curves, that measure the probability of the correct prediction of the clinical and the combined models, were found to be 0.933 and 0.973, respectively. CONCLUSIONS: These models can be used for predicting difficult laryngoscopy and intubation in clinical practice.

Adult↗

Increased body mass index per se is not a predictor of difficult laryngoscopy.

PURPOSE: We investigated the association between morbid obesity and difficult laryngoscopy (DL). METHODS: In a prospective, controlled study we evaluated the impact of different variables on the prediction of DL in 200 morbidly obese (study group-SG), and 1272 non-obese (control group-CG) patients undergoing elective surgery. Variables assessed included age, sex, body mass index (BMI), protruding, loose, and missing upper teeth, thyro-mental distance, temporo-mandibular joint (TMJ) function, neck extension, and Mallampati class. A Cormack grade III or IV was considered DL. RESULTS: The SG patients were younger (P < 0.000), there were more females in the SG (P < 0.000) and more in the SG had teeth problems (P = 0.026). More patients in the SG (10% vs 1%), had obstructive sleep apnea (P < 0.001) with 90% of them in the SG having a grade III laryngoscopy. High BMI did not affect the laryngoscopy difficulty (P = 0.56). Multivariable regression analysis revealed that morbid obesity, increased age, male sex, pathology of TMJ, and higher Mallampati class, were independent predictors of DL. When interaction between the predictors and the group was added to the multivariable model, the SG was no longer a predictor by itself, rather its association with abnormal upper teeth turned to be significant for prediction of DL. CONCLUSIONS: Increased age, male sex, TMJ pathology, Mallampati 3 and 4, a history of obstructive sleep apnea and abnormal upper teeth were associated with a higher incidence of DL. The magnitude of BMI had no influence on difficulty with laryngoscopy.

Adult↗

Difficult laryngoscopy made easy with a "BURP".

Displacement of the larynx by backward, upward and rightward pressure on the thyroid cartilage or "BURP" may improve visualization of the glottis in some cases of difficult direct laryngoscopy. In a patient with the Treacher-Collins syndrome in whom conventional laryngoscopy had proved impossible and tracheal intubation extremely difficult, this manoeuvre exposed the entire glottis and made tracheal intubation under direct vision easy. In a patient with protruding upper incisors and a prominent premaxilla which precluded a view of the glottis by conventional laryngoscopy, "BURP" again revealed the glottic opening and simplified the placement of an endotracheal tube. This experience suggests that "BURP" be considered as a potential aid in the management of difficult direct laryngoscopy.

Adult↗

[Videolaryngoscopy versus direct laryngoscopy for elective endotracheal intubation].

BACKGROUND: We compared the ease of viewing the glottis under direct vision during conventional laryngoscopy with the quality of indirectly viewing on a monitor during laryngoscopy with a Macintosh videolaryngoscope in a multicenter study. PATIENTS AND METHODS: After ethical approval and written informed consent of 300 patients with no anticipated difficult airway, conventional laryngoscopy with a Macintosh videolaryngoscopy blade was performed and the quality of the view of the glottis was assessed and documented according to the Cormack and Lehane scoring system as modified by Yentis and Lee. Subsequently, the indirect viewing conditions on the monitor were documented without changing the position of the blade. Differences between both distributions were analyzed using the Bland-Altman Test. RESULTS: Videolaryngoscopy improved the laryngoscopy score by 1 grade in 72 cases, by 2 grades in 17 cases and by 3 grades in 2 cases. A relevant improvement (from grades III/IV to II) was found in 28 patients. Viewing conditions worsened in 3 cases by 1 grade, in 4 cases by 2 grades and in 3 cases by 3 grades. A statistical analysis of the data gave a bias of 0.31 and an SD bias of 0.77.The 95% confidence interval of the distribution ranged from -1.12 to 1.81. CONCLUSION: Videolaryngoscopy can lead to better viewing conditions but in rare cases it may result in worse viewing conditions.

Adult↗

Flexible laryngoscopy in neonates and infants: insertion through a median opening in the face mask.

The most common reasons for laryngoscopy in newborns and infants are inspiratory stridor and/or dyspnea. With the help of flexible endoscopes, especially with instruments of diminished diameter, laryngoscopy can be carried out even in premature newborns. We report on a technique of flexible laryngoscopy without the need for restraint and with improved safety. A modified face mask is used for endoscopy. An additional hole is made into the mask with a 4.5 mm drill. It is located in the midline just above the nostrils, about 2.5 cm above the ventilation opening. The flexible endoscope is passed into the nose and pharynx with ease. It does not interfere with the anesthetist's ventilation by the mask. In inhalation anesthesia with halothane, 100% oxygen is supplied. The larynx remains in its physiological position. The head is not retroflexed, and the tongue is not supported by an endoscope as in direct laryngoscopy. No muscle relaxation is used, and muscular activity of the larynx can be observed during spontaneous and assisted ventilation.

Anesthesia, Inhalation↗