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PubMed2006

Stimulation induced variability of pulse plethysmography does not discriminate responsiveness to intubation.

BACKGROUND: Hypnotic depth but not haemodynamic response to painful stimulation can be measured with various EEG-based anaesthesia monitors. We evaluated the variation of pulse plethysmography amplitude induced by an electrical tetanic stimulus (PPG variation) as a potential measure for analgesia and predictor of haemodynamic responsiveness during general anaesthesia. METHODS: Ninety-five patients, ASA I or II, were randomly assigned to five groups [Group 1: bispectral index (BIS) (range) 40-50, effect site remifentanil concentration 1 ng ml(-1);Group 2: BIS 40-50, remifentanil 2 ng ml(-1); Group 3: BIS 40-50, remifentanil 4 ng ml(-1); Group 4: BIS 25-35, remifentanil 2 ng ml(-1); Group 5: BIS 55-65, remifentanil 2 ng ml(-1)]. A 60 mA tetanic stimulus was applied for 5 s on the ulnar nerve. From the digitized pulse oximeter wave recorded on a laptop computer, linear and non-linear parameters of PPG variation during the 60 s period after stimulation were computed. The haemodynamic response to subsequent orotracheal intubation was recorded. The PPG variation was compared between groups and between responders and non-responders to intubation (anova). Variables independently predicting the response were determined by logistic regression. RESULTS: The probability of a response to tracheal intubation was 0.77, 0.47, 0.05, 0.18 and 0.52 in Groups 1-5, respectively (P<0.03). The PPG variability was significantly higher in responders than in non-responders but it did not improve the prediction of the response to tracheal intubation based on BIS level and effect site remifentanil concentration. CONCLUSION: Tetanic stimulation induced PPG variation does not reflect the analgesic state in a wide clinical range of surgical anaesthesia.

Adult↗

PubMed2000

Retrograde nasotracheal intubation with a new tracheal tube: a feasibility study.

We have assessed the feasibility of retrograde nasotracheal intubation using a flexometallic tracheal tube with a detachable pilot balloon and connector in a study of 20 consecutive adult patients undergoing oropharyngeal surgery. The technique consisted of: (1) laryngoscope-guided orotracheal intubation; (2) insertion of an 18-gauge Foley catheter through the nose and retraction into the mouth; (3) detachment of the anaesthesia circuit, pilot balloon and connector; (4) insertion of the Foley catheter tip into the proximal end of the tracheal tube and inflation of the Foley catheter cuff; (5) withdrawal of the Foley catheter and attached tracheal tube back through the nose; (6) deflation of the Foley catheter cuff; and (7) re-attachment of the pilot balloon, connector and anaesthesia circuit. The technique was successful at the first attempt in all patients. Mean time taken to insert the Foley catheter and retract it into the mouth was 19 (range 12-30) s. Mean time taken from disconnection to reconnection of the anaesthesia circuit was 8 (6-10) s. Heart rate increased after intubation, but there were no significant changes in arterial pressure. Nasal bleeding, airway problems and hypoxic events did not occur. No anatomical abnormalities or nasal trauma were detected at rhinoscopy. We conclude that retrograde nasotracheal intubation is feasible using a flexometallic tracheal tube with a detachable pilot balloon and connector.

Adult↗

PubMed1995

Predicting difficult endotracheal intubation in surgical patients scheduled for general anesthesia: a prospective blind study.

We conducted a prospective, blind study to determine whether a difficult endotracheal intubation could be predicted preoperatively by evaluation of one or more anatomic features of the head. In 471 adults presenting for elective surgery, the size of the tongue relative to the oral cavity was assessed according to the Mallampati classification (oropharyngeal class), and the distance between the chin and thyroid cartilage (thyromental distance) and the angle at full extension of the head (head extension) were measured. At laryngoscopy, the difficulty in visualizing the larynx was determined by a different observer. Assignment to oropharyngeal Class 3, a thyromental distance < or = 7 cm, and a head extension < or = 80 degrees, considered either alone or in various combinations, had low sensitivity and positive predictive values in identifying patients with airways that were difficult to intubate, but high specificity and negative predictive values. We conclude that these three tests are of little value in predicting difficult intubation in adults, although the likelihood of an easy endotracheal intubation is high when they yield negative results.

Adolescent↗

PubMed1997

Efficacy of the self-inflating bulb in differentiating esophageal from tracheal intubation in the parturient undergoing cesarean section.

We studied the efficacy of the self-inflating bulb (SIB) in differentiating tracheal from esophageal intubation in 40 parturients undergoing elective cesarean section under general anesthesia. After induction and muscle relaxation, the trachea was intubated under direct vision with cuffed tube. In 20 parturients, the esophagus was also intubated with an identical tube. Before ventilation was initiated, an independent anesthesiologist checked tube positions with the SIB using two techniques. In one technique (T1), the SIB was compressed before connection to the tube; in the other technique (T2), the SIB was first connected to the tube and then compressed. The speed of reinflation was graded as rapid, delayed, and none. Tracheal tube position was reassessed immediately before and after delivery. Before initiation of controlled ventilation, the incidence of false negative results was 47.5% with T1 and 27.5% with T2 but significantly decreased to 17.5% with T1 and 7.5% with T2 when retested before delivery. After delivery, no false negative results occurred. The incidence of false positive results immediately after induction was 30% with T1 and 35% with T2. The mechanism of false negative responses may be attributed to decreased functional residual capacity leading to reduced caliber of intrathoracic airways and terminal airway closure; whereas false positive responses may be related to an incompetent gastroesophageal junction. We conclude that the SIB is unreliable for differentiating tracheal from esophageal intubation in the parturient undergoing cesarean section.

Adult↗

PubMed1999

Does the Murphy eye reduce the reliability of chest auscultation in detecting endobronchial intubation?

UNLABELLED: Bilateral breath sounds are routinely auscultated after endotracheal intubation to verify that the endotracheal tube (ETT) tip is properly positioned. We conducted the present study to ascertain whether the eye of the Murphy tube has an influence on the reliability of auscultation of breath sounds in detecting endobronchial intubation. Twenty patients undergoing scheduled oral and maxillofacial surgery participated in this study. After the induction of general anesthesia, either the Magill tube or the Murphy tube was inserted through the nose into the trachea. The fiberoptic bronchoscope was inserted through the ETT, and the distance from the nares to the carina of the trachea was measured. When breath sounds from the left side of the chest changed and disappeared while the ETT was being advanced, the distance from the nares to the ETT tip was measured. Unilateral auscultatory change was not observed until the ETT tip was advanced beyond the carina and inserted 1.5+/-0.4 cm into the right mainstem bronchus when the Magill tube was used and 2.0+/-0.4 cm when the Murphy tube was used (P < 0.01). Breath sounds disappeared when the ETT tip was further advanced up to 3.2+/-0.3 cm from the carina. We demonstrated that the eye of the Murphy tube reduces the reliability of chest auscultation in detecting endobronchial intubation. IMPLICATIONS: The Murphy eye was designed to allow ventilation of the lung when the bevel of the endotracheal tube is occluded. We demonstrated that the eye of the Murphy tube reduces the reliability of chest auscultation in detecting endobronchial intubation.

Adult↗

PubMed2000

The efficacy and safety of EMLA cream for awake fiberoptic endotracheal intubation.

EMLA Cream (EC; Astra, Westborough, MA) has been widely used as a local anesthetic. Limited safety information is available with respect to the application of EC to the oral mucous membranes. The purpose of this pilot study was to evaluate the efficacy and safety of EC when applied to oral mucosa for fiberoptic intubation. Twenty ASA physical status I-IV patients (11 women and 9 men), 28-57 yr old, who were scheduled for awake, fiberoptic, intubation participated in this open-label study. A total of 4 g of EC was used for 5 min until the patient showed no evidence of a gag reflex (this was evaluated clinically by the patient's acceptance of the William's airway and considered the endpoint for assessing adequate topicalization of the oropharynx). The measured peak plasma concentration of lidocaine or prilocaine did not reach toxic levels in any patient. Methemoglobin levels did not exceed normal values (1.5%) in any patient, and there was no relationship between methemoglobin levels and patient weight, amount of EC used, measured peak plasma concentration, or times to measured peak concentrations of prilocaine or lidocaine. We conclude that EC provided satisfactory topical anesthesia allowing for successful oral fiberoptic intubation in all patients and should be considered a safe alternative for anesthetizing the airway of patients requiring awake oral fiberoptic intubation.

Adult↗

PubMed2002

Difficult retrograde endotracheal intubation: the utility of a pharyngeal loop.

UNLABELLED: Direct laryngoscopy and tracheal intubation remains the technique of choice to achieve control of the airway. Alternative or additional techniques of airway control are required whenever an airway is deemed difficult because of anatomical and/or technical reasons. The retrograde intubation technique is an important option for gaining airway access from below the vocal cords in such situations (1). We report successful management and the problems encountered while gaining the upper airway by the retrograde catheter method in a patient having bilateral fibrous ankylosis of the temporomandibular joint (TMJ). IMPLICATIONS: A 30-yr-old woman presented for redo-release of bilateral temporomandibular joint ankylosis under general anesthesia. During the previous anesthetic for primary release of ankylosis, tracheostomy was done, as conventional blind nasotracheal and retrograde intubation attempts failed several times. This case report describes the method for overcoming the difficulties of a retrograde intubation procedure in removing the guiding catheter nasally by using a pharyngeal loop assembly.

Adult↗

PubMed1985

Laryngeal injury in a dog model of prolonged endotracheal intubation.

Using a dog model of prolonged translaryngeal intubation, the authors studied laryngeal injury. Segments of 10.7 mm diameter endotracheal tube were sutured in place in the larynges of anesthetized animals, and the animals were allowed to awaken and the tubes left in place for periods of 24 h to 84 days in a total of 13 dogs. Each animal's larynx was studied endoscopically at weekly intervals and at the time of death. Both endoscopic and postmortem examination revealed erythematous laryngeal mucosa at 24 h and severe mucosal ulceration by 1 week. Microscopic examination revealed mucosal inflammation at 24 h with loss of mucosal architecture by 1 week. In several animals intubated 1 week or longer, inflammatory infiltrates were present in the arytenoid cartilage. While damage was generally severe by 1 week, it did not tend to become more severe after that time. Between week 1 and week 12, there was no significant correlation of the severity of laryngeal injury with the duration of endotracheal intubation. The results suggest that duration alone may not be a factor in laryngeal injury after the first week of intubation.

Animals↗

PubMed1994

End-tidal sevoflurane concentration for tracheal intubation and minimum alveolar concentration in pediatric patients.

BACKGROUND: Sevoflurane is a new inhalational anesthetic agent having low solubility in blood and a relatively nonpungent odor. As such it should be useful as an inhalation induction in pediatric patients. The objectives of the study were to determine both the minimum alveolar concentration (MAC) and the concentration required for tracheal intubation (MACEI) of sevoflurane in pediatric patients. METHODS: The study group consisted of 36 ASA physical status 1 elective surgical patients, aged 1-9 yr. MACEI determination: After establishing and maintaining the end-tidal concentration for 15 min, tracheal intubation was attempted with an uncuffed tracheal tube without neuromuscular relaxants or other adjuvants. Each concentration at which tracheal intubation was attempted was predetermined according to the up-and-down method (with 0.5% as a step size). MAC determination: The patients examined were the same as those for MACEI determination except that for the exclusion of those to whom neuromuscular relaxants or other adjuvants drugs were administered. End-tidal sevoflurane concentration was determined according to the up-and-down method (with 0.5% as a step size) and held constant for at least 15 min before a skin incision. RESULT: MACEI of sevoflurane was 2.69% (95% fiducial limits: 2.23% and 3.37%); MAC of sevoflurane was 2.03% (95% fiducial limits: 1.51% and 2.53%); and the MACEI/MAC ratio was 1.33. CONCLUSION: Sevoflurane appears to be suitable for use in pediatric patients as an induction agent, permitting tracheal intubation without neuromuscular relaxants.

Anesthetics↗

PubMed1994

End-tidal sevoflurane concentrations for laryngeal mask airway insertion and for tracheal intubation in children.

BACKGROUND: Sevoflurane, a new inhalational anesthetic agent characterized by a low blood-gas partition coefficient and nonpungent odor, appears suitable as an induction agent for children. The laryngeal mask airway is a new device for maintaining airway patency during anesthesia. This study was conducted to determine the sevoflurane concentrations required for insertion of a laryngeal mask (MACLMI) and for tracheal intubation (MACTI) in children. METHODS: Forty-two patients, aged 1-9 yr, scheduled for surgery during general anesthesia were randomly assigned into two groups: MACLMI (n = 21) and MACTI (n = 21). After the predetermined end-tidal concentration had been established and maintained for 20 min, laryngeal mask insertion or tracheal intubation was attempted without neuromuscular relaxants or other adjuvants. Each concentration at which laryngeal mask insertion or tracheal intubation was attempted was predetermined by the up-and-down method (with 0.5% as a step size). RESULTS: Sevoflurane MACLMI was 2.00 +/- 0.28%. Sevoflurane MACTI was 2.83 +/- 0.34%, significantly greater than MACLMI. CONCLUSIONS: Laryngeal mask insertion can be performed at a lesser sevoflurane concentration than that required for tracheal intubation.

Anesthesia↗

PubMed1997

Predicting difficult intubation with indirect laryngoscopy.

BACKGROUND: It is not always possible to predict when tracheal intubation will be difficult or impossible. The authors wanted to determine whether indirect laryngoscopy could identify patients in whom intubation was difficult. METHODS: Indirect laryngoscopy was done in 2,504 patients. The Wilson risk sum score and the modified Mallampati score were also studied in a different series of 3,680 patients for comparison. These predictive methods were compared according to three parameters: positive predictive value, sensitivity, and specificity. RESULTS: Of 6,184 patients studied, the trachea proved difficult to intubate in 82 (1.3%). Positive predictive value (31%) and specificity (98.4%) with indirect laryngoscopy were greater than the other two predictive methods (P < 0.01), whereas sensitivity with indirect laryngoscopy (69.2%) was greater than that of the Wilson risk sum score (55.4%) (P < 0.01). CONCLUSIONS: Although in 15% of patients indirect laryngoscopy could not be performed because of excessive gag reflex, indirect laryngoscopy can serve as an effective method to predict difficult intubation.

Adult↗

PubMed1998

Skin vasomotor reflex predicts circulatory responses to laryngoscopy and intubation.

BACKGROUND: An evaluation of autonomic reactivity may help to predict circulatory responses to intubation. The relation between the magnitude of the skin vasomotor reflex (SVmR) immediately before laryngoscopy and the circulatory responses to intubation was examined. METHODS: Forty-four adult patients (classified as American Society of Anesthesiologists physical status I or II) were studied. General anesthesia was induced with fentanyl and thiamylal and maintained with nitrous oxide and sevoflurane. The SVmR was evoked by an electrostimulus to the ulnar nerve, and decreases in skin blood flow were detected using a laser-Doppler flowmeter. In study 1, two groups of patients were studied. In the monitored group (n = 14), laryngoscopy was performed when the SVmR amplitude had decreased to less than 0.1. In the control group (n = 15), intubation was performed regardless of changes in the SVmR amplitude. In study 2, after induction, the end-tidal concentration of sevoflurane was maintained at 1 MAC (n = 9) or 1.3 MAC (n = 6) for 5 min. The SVmR was tested by changing the electric intensity. RESULTS: In study 1, the blood pressure and heart rate of the control group increased significantly (P < 0.01) after laryngoscopy. The blood pressure of the monitored group did not increase. The SVmR amplitude and the systolic blood pressure changes showed a significant linear correlation (P < 0.001). In study 2, the relation between the electric intensity and the SVmR amplitude showed a weak but significant correlation (P < 0.01) in the 1 MAC group. CONCLUSION: The evaluation of the SVmR provides useful information for determining the optimal anesthetic depth for laryngoscopy and intubation in individual patients.

Adult↗

PubMed1999

Intramuscular rapacuronium in infants and children: dose-ranging and tracheal intubating conditions.

BACKGROUND: Intravenous rapacuronium's rapid onset and short duration suggest that intramuscular rapacuronium might facilitate tracheal intubation without prolonged paralysis. Accordingly, the authors injected rapacuronium into the deltoid muscle to determine the optimal dose and time for intubation in pediatric patients. METHODS: Unpremedicated patients (aged, 2 months to 3 yr) were studied. Part I: Spontaneous minute ventilation (V(E)) and twitch tension were measured during N2O/halothane anesthesia. Rapacuronium (2.2-5.5 mg/kg, given intramuscularly, n = 23), succinylcholine (4 mg/kg, given intramuscularly, n = 12), or vecuronium (0.1 mg/kg, given intravenously, n = 15) was given. Time to 50% depression of V(E) and 10% recovery of twitch were measured. Dose for each patient was changed 10-20% according to the previous patient's response. Part II: In 22 patients anesthetized with 0.82-1.0% halothane, the optimal rapacuronium dose determined in part I (infants, 2.8 mg/kg; children, 4.8 mg/kg) was given intramuscularly. Laryngoscopy was scored. Time to laryngoscopy was increased or decreased 0.5 min according to the previous patient's response. RESULTS: Part I: Rapacuronium typically depressed ventilation in < or = 2 min with 10% twitch recovery in 20-60 min. With succinylcholine, median time to ventilatory depression was 1.3 and 1.1 min for infants and children, respectively; for vecuronium, 0.7 and 0.6 min. Part I: Intubating conditions were good-excellent at 3.0 and 2.5 min in infants and children, respectively; time to 10% twitch recovery (mean +/- SD) was 31 +/- 14 and 36 +/- 14 min in the two groups. CONCLUSIONS: This pilot study indicates that deltoid injection of rapacuronium, 2.8 mg/kg in infants and 4.8 mg/kg in children, permits tracheal intubation within 2.5-3.0 min, despite a light plane of anesthesia. Duration of action is intermediate.

Child, Preschool↗

PubMed2000

Female gender associates with increased duration of intubation and length of stay after coronary artery surgery. CABG Clinical Benchmarking Database Participants.

BACKGROUND: Females have worse outcome than do males after coronary artery bypass grafting; however, gender effects on length of stay (LOS) outcomes, such as duration of intubation or intensive care unit (ICU) LOS, have not been evaluated previously. The authors hypothesized that adjustment for pertinent preoperative covariates would eliminate any significant effect of gender on duration of intubation, LOS in the ICU after extubation, total ICU LOS, postoperative (exclusive of ICU) LOS, or total postoperative LOS. METHODS: Patients undergoing elective or urgent primary coronary artery bypass grafting surgery at 51 academic health centers in 1995 and 1997 were studied. Unique multivariable statistical models were developed for duration of intubation, ICU LOS after extubation, total ICU LOS, and postoperative (exclusive of ICU and total) LOS to test for independent associations with gender. Preoperative but not intraoperative or postoperative variables were included in the model. P> or =0.01 was considered significant. RESULTS: All LOSs were of significantly longer duration in females than in males in both the 1995 (n = 1,064) and 1997 (n = 910) data collections. After covariate adjustment, female sex remained associated with significantly longer duration ICU LOS and total postoperative LOS in both the 1995 (female:male ratios 1.30:1 and 1.13:1, respectively) and the 1997 (female:male ratios 1.19:1 and 1.12:1, respectively) data sets. After covariate adjustment, duration of intubation and ICU LOS after extubation were of significantly longer duration in women than men in 1995 (female:male ratios 1.22:1 and 1.39:1, respectively), but the differences were not significant in 1997. CONCLUSIONS: Even in the context of accelerated recovery programs, these analyses show that female sex has powerful associations with increased LOS intervals for coronary artery bypass grafting surgery, even after adjustment for preoperative covariates. These effects could result from differences in the ways in which men and women respond to coronary artery disease, anesthesia, and coronary artery bypass grafting surgery, or to bias on the part of healthcare workers.

Aged↗

PubMed2001

A comparison of tracheal tube tip designs on the passage of an endotracheal tube during oral fiberoptic intubation.

BACKGROUND: The design of an endotracheal tube has been shown to influence the passage of the tube through the glottis during fiberoptic intubation. Difficulty in passing the endotracheal tube can occur if the aryepiglottic folds obstruct the passage of the bevel. The relevant aspects of endotracheal tube design include the shape of the bevel, the material used by the manufacturer, and the ability of the tube to conform to the shape of the fiberscope. The aim of the current study was to compare the ease of passage through the glottis of two different tubes. One tube was a wire reinforced polyvinyl chloride tube with a standard bevel and the other was a newly designed tube with a bevel of different shape and made of silicone rubber. The new design is for use with the a commerical intubating laryngeal mask. METHODS: The authors studied a population of 30 patients who received a standard anesthetic. In all cases, oral fiberoptic intubation was attempted. Anesthetic was administered to each patient using both tubes, and before the study the order of the tubes was randomized. The difficulty in passing the tube was assessed by a blinded observer and graded using a three-point scale (grade 1: no difficulty passing the tube; grade 2: obstruction to passing the tube relieved by withdrawal and a 90 degrees anticlockwise rotation; grade 3: obstruction necessitating more than one manipulation or external laryngeal manipulation). RESULTS: In 27 patients, no difficulty was shown by use of the silicone-tipped tube. In only three patients was there difficulty that necessitated a 90 degrees anticlockwise twist. With the wire-reinforced tube, no difficulty was experienced on 14 occasions. Grade 1 difficulty was experienced eight times and difficulty necessitating more than one maneuver, head movement, or external laryngeal manipulation was seen on eight occasions. Statistical significance was achieved at P = 0.0002 (Wilcoxon signed rank test). CONCLUSIONS: The authors conclude that the use of the silicone-tipped tube with the new bevel design may provide an advantage in the clinical situation of fiberoptic intubation.

Adult↗

PubMed2003

Laryngoscopic intubation: learning and performance.

BACKGROUND: Many healthcare professionals are trained in direct laryngoscopic tracheal intubation (LEI), which is a potentially lifesaving procedure. This study attempts to determine the number of successful LEI exposures required during training to assure competent performance, with special emphasis on defining competence itself. METHODS: Analyses were based on a longitudinal study of novices under training conditions in the operating room. The progress of 438 LEIs performed by the 20 nonanesthesia trainees was monitored by observation and videotape analysis. Eighteen additional LEIs were performed by experienced anesthesiologists to define the standard. A generalized linear, mixed-modelling approach was used to identify key aspects of effective training and performance. The number of tracheal intubations that the trainees were required to perform before acquiring expertise in LEI was estimated. RESULTS: Subjects performed between 18 and 35 laryngoscopic intubations. However, statistical modeling indicates that a 90% probability of a "good intubation" required 47 attempts. Proper insertion and lifting of the laryngoscope were crucial to "good" or "competent" performance of LEI. Traditional features, such as proper head and neck positions, were found to be less important under the study conditions. CONCLUSIONS: This study determined that traditional LEI teaching for nonanesthesia personnel using manikin alone is inadequate. A reevaluation of current standards in LEI teaching for nonanesthesia is required.

Adult↗

PubMed2005

Predicting difficult intubation in apparently normal patients: a meta-analysis of bedside screening test performance.

The objective of this study was to systematically determine the diagnostic accuracy of bedside tests for predicting difficult intubation in patients with no airway pathology. Thirty-five studies (50,760 patients) were selected from electronic databases. The overall incidence of difficult intubation was 5.8% (95% confidence interval, 4.5-7.5%). Screening tests included the Mallampati oropharyngeal classification, thyromental distance, sternomental distance, mouth opening, and Wilson risk score. Each test yielded poor to moderate sensitivity (20-62%) and moderate to fair specificity (82-97%). The most useful bedside test for prediction was found to be a combination of the Mallampati classification and thyromental distance (positive likelihood ratio, 9.9; 95% confidence interval, 3.1-31.9). Currently available screening tests for difficult intubation have only poor to moderate discriminative power when used alone. Combinations of tests add some incremental diagnostic value in comparison to the value of each test alone. The clinical value of bedside screening tests for predicting difficult intubation remains limited.

Humans↗

PubMed1983

Bronchoscopic intubation of patients with trismus.

Endotracheal intubation of patients with limited bite opening is a serious task for the caring physician. Blind intubation can be frustrating and, very often, unsuccessful. Tracheostomy, even under ideal conditions, can create serious complications. Fiberoptic bronchoscopy has opened up a new era in intubation of patients with trismus. In this article, we discuss an organized illustrated procedure for intubation of such patients. We have used this procedure successfully in 16 patients over the last sixteen months in our craniofacial unit, with no complications and no failures.

Bronchoscopy↗