Fu S. Xue

Spray-as-you-go airway topical anesthesia in patients with a difficult airway: a randomized, double-blind comparison of 2% and 4% lidocaine.

BACKGROUND: We designed this randomized, double-blind clinical study to compare the safety and efficacy of 2% and 4% lidocaine during airway topical anesthesia with a spray-as-you-go technique via the fiberoptic bronchoscope. METHODS: Fifty-two adult patients with a difficult airway were randomly assigned to 1 of 2 study groups to receive 2% (Group 1) or 4% lidocaine (Group 2) by a spray-as-you-go technique with the fiberoptic bronchoscope, in a double-blind manner. After airway topical anesthesia, awake fiberoptic orotracheal intubation (FOI) was performed. Level of sedation, time for each lidocaine spray in different targeted areas, total times for airway sprays, total dosages of lidocaine used for airway sprays, intubation times, and number of intubation attempts were noted. An independent investigator scored patients’ comfort during airway topical anesthesia, patients’ reaction, coughing severity, and intubating condition during awake FOI, and observed changes of arterial blood pressure and heart rate during each stage in the airway manipulation process. Serial blood samples were obtained for analysis of plasma lidocaine concentrations. RESULTS: Except for the total dosages and plasma concentrations of lidocaine, there were no significant differences in any of the observed variables between groups. All patients exhibited excellent or acceptable intubating conditions. The total dosages of lidocaine were significantly smaller in Group 1 (3.4 ± 0.6 mg/kg) than in Group 2 (7.1 ± 2.1 mg/kg). The plasma lidocaine concentrations in all observed points after the supraglottic sprays were larger in Group 2 than in Group 1. CONCLUSIONS: Both 2% and 4% lidocaine administered topically by a spray-as-you-go technique can provide clinically acceptable intubating conditions for awake FOI in sedated patients with a difficult airway. As compared with 4% lidocaine, however, 2% lidocaine requires a smaller dosage and results in lower plasma concentrations.

Dose-response and time course of effect of rocuronium in male and female anesthetized patients

To determine differences from dose-response and time-course of rocuronium between male and female patients, 60 adult patients (30 male and 30 female), ASA grade I, aged 17-52 yr, undergoing elective plastic surgery were studied. Anesthesia was maintained with 60% nitrous oxide in oxygen, thiopental, and incremental doses of fentanyl as required. Neuromuscular function was assessed mechanomyographically with train-of-four (TOF) stimulation at the wrist every 12 s, and the percentage depression of the T1 response was used as the study variable. The dose-response relationship of rocuronium was determined by a cumulative dose-response technique. The results showed that the dose-response curve of rocuronium in the men was shifted to the right, indicating a decrease in the sensitivity to rocuronium-induced neuromuscular block versus the women. The 50%, 90%, and 95% effective doses of rocuronium were 178.4 +/- 53.7, 358.7 +/- 101.3, and 386.2 +/- 113.4 micro g/kg, respectively, in male patients, and 128.8 +/- 42.5, 252.8 +/- 51.7, and 274.4 +/- 59.4 micro g/kg in female patients. After an intravenous administration of total dose of 400 micro g/kg rocuronium, neuromuscular block was significantly longer in the men than in the women. The duration of peak effect, clinical duration, and total duration were 6.5 +/- 3.0,12.5 +/- 4.9, and 33.6 +/- 8.7 min, respectively, in male patients, and 11.8 +/- 2.7, 18.5 +/- 5.3, and 46.8 +/- 9.6 min in female patients. We conclude that women were approximately 30% more sensitive to rocuronium compared with men. Implications: The authors found that women were 30% more sensitive to rocuronium than men. This suggests that the routine dose of rocuronium should be reduced in women compared with men. (Anesth Analg 1997;85:667-71)

The influence of surgical sites on early postoperative hypoxemia in adults undergoing elective surgery.

UNLABELLED To determine the influence of the surgical sites on early postoperative hypoxemia, we studied postoperative hypoxemia in 994 patients, ASA physical status I or II, aged 18-68 yr, scheduled for various types of elective surgery. Patients were divided into three groups on the basis of the surgical sites: Group 1 = elective superficial plastic surgery (n = 288); Group 2 = upper abdominal surgery (n = 452); and Group 3 = thoracoabdominal surgery (n = 254). Anesthesia was maintained with 1%-2% enflurane and 67% nitrous oxide in oxygen; thiopental or fentanyl was given IV as required. SpO2 levels were recorded while patients breathed room air shortly after arrival in the recovery room (0 min) and 5, 10, 15, 20, 30, 40, 50, 60, 120, and 180 min thereafter. The results showed that during the early postoperative period, the degree of arterial desaturation and the incidences of hypoxemia (SpO2 86%-90%) and severe hypoxemia (SpO2 85%) were closely related to the operative sites and were greatest for thoracoabdominal operations, less for the upper abdominal operation, and least for the peripheral surgery. The incidence of hypoxemia and severe hypoxemia in the recovery room was 7% and 0.7%, respectively, in Group 1, 38% and 3% in Group 2, and 52% and 20% in Group 3. Mild airway obstruction and hypothermia in the postanesthesia recovery unit (PAR) were the predictive factors of early postoperative hypoxemia. We conclude that during the early postoperative period, there were significant differences in SpO2 levels and incidences of hypoxemia and severe hypoxemia among the three groups. IMPLICATIONS We found that the severity of arterial desaturation and the incidence of hypoxemia during the early postoperative period are closely related to the surgical sites and are strongest for thoracoabdominal surgery, less for upper abdominal surgery, and least for peripheral surgery.

The pharmacokinetics of vecuronium in male and female patients

To evaluate the effect of gender on the pharmacokinetics of vecuronium, we studied 30 patients (15 male and 15 female) undergoing elective plastic surgery with anticipated surgical blood loss of <300 mL under general anesthesia.General anesthesia was induced with thiopental 4-6 mg/kg and fentanyl 2-4 [micro sign]g/kg and was maintained with 60% nitrous oxide in oxygen and an end-tidal concentration of 1.5%-2% enflurane. After a 2-min infusion of vecuronium 100 [micro sign]g/kg, a modified fluorometric assay was used to determine the plasma concentrations of vecuronium for 5 h. The results showed that, compared with women, the plasma concentrations of vecuronium in men were significantly lower during the first 20 min and that the disposition kinetics of vecuronium can be best described mathematically by a three-compartment open model in the two groups. The volume of the central compartment and the volume of distribution at steady state were 39.6 +/- 8.6 and 164.8 +/- 29.3 mL/kg, respectively, in women. These values increased significantly to 54.4 +/- 14.4 and 201.4 +/- 75.8 mL/kg in men (P < 0.05). When the data were calculated on the basis of ideal body weight, the volume of distribution of vecuronium was also different between men and women (P < 0.05. The half-lives of fast distribution and distribution, the elimination half-life, mean residual time, area under the plasma-concentration curve, and plasma clearance were not different between the two groups. We conclude that the pharmacokinetics of vecuronium are significantly different between genders and that and men have the greater volume of distribution of vecuronium. Implications: The authors found that, compared with women, men had lower plasma concentrations of vecuronium after the IV administration of vecuronium and a larger volume of distribution of vecuronium. The pharmacokinetic differences may be related to the differences in the sensitivity to vecuronium between genders. (Anesth Analg 1998;86:1322-7)

Study of the safe threshold of apneic period in children during anesthesia induction

STUDY OBJECTIVES (1) To investigate changes in arterial oxygen saturation via pulse oximeter (SpO2) during apnea and after reinstitution of manual ventilation at SpO2 of 95% or 90% following rapid sequence induction of anesthesia in children after 2-minute preoxygenation; (2) to determine whether the setting of a safe threshold of apneic period to an SpO2 of 95% is appropriate in children during anesthetic induction; and (3) to evaluate the influences of age, body weight, and height on the time from the start of apnea to SpO2 of 95%. DESIGN A clinical study of random design and comparison among groups. SETTING Operating room of a plastic surgery hospital of the Chinese Academy of Medical Sciences and Peking Union Medical College. PATIENTS 152 infants and children, ASA physical status 1, aged 3 months to 12 years, scheduled for elective plastic surgery. INTERVENTIONS Patients were divided into three age groups: Group 1-infants 3 months to 1 year (n = 39); Group 2 children 1 to 3 years (n = 41); and Group 3-children 3 to 12 years (n = 72). Patients in each age group were randomly allocated again to Subgroups A and B. After a 2-minute preoxygenation, anesthesia was induced with thiopental 5 mg/kg, fentanyl 5 micrograms/kg and suxamethonium 1.5 mg/kg. Patients were manually ventilated when SpO2 decreased to 90% in Subgroups A and 95% in Subgroups B, respectively, during apnea. MEASUREMENTS AND MAIN RESULTS SpO2 was measured continuously with a Datex pulse oximeter applied to the right index finger. During apnea, the times for SpO2 to decrease to 09% (T99) and 95% (T99) in all children, and 90% (T90) in Subgroups A were recorded. The time for SpO2 to decrease from 95% to 90% (T95-90) in Subgroups A was also measured. After reinstitution of manual ventilation, the time when SpO2 continued to decrease (T1) and the time from the end of apnea to recovery of SpO2 baseline (T2) were determined. In addition, the lowest value of SpO2 after apnea was also recorded. The results showed that younger children were more susceptible than older children to the risk of hypoxemia during apnea. There were significant differences in T99, T95, T90, and T95-90 between the three age groups T1 and T2 were significantly longer in Group 3 than in Groups 1 and 2. There were significant differences in the lowest values of SpO2 following apnea among the three Subgroups A and between Subgroups A and B of each age group. During apnea, heart rate decreased gradually as SpO2 decreased, showing a significant decrease at SpO2 of 95%. Bradycardia was found in three children in Subgroups A. The apnea time to SpO2 of 95% correlated well with age, weight, and height by linear regression analysis. CONCLUSIONS The safe threshold of an apneic period setting to an SpO2 of 95% was appropriate in children during anesthesia induction. Despite the same duration of preoxygenation, younger children were more susceptible than elder ones to the risk of hypoxemia during apnea. The apnea time to SpO2 of 95% correlated with age, body weight, and height using linear regression analysis.

More maneuvers to facilitate endotracheal intubation using the Airtraq® laryngoscope in children with difficult airways

Surgical repair of the atresia auris congenita was performed successfully, and the tracheal tube was removed without adverse sequelae. The AOL provides a high-grade, indirect, close proximity view of the glottis without the need for alignment of the oral, pharyngeal, and laryngeal axes. The oropharyngeal airwayshaped blade allows laryngeal exposure with ease even in patients with difficult airways (1–5). In addition, the AOL has a guiding channel that directs the tracheal tube through the glottis; and hence, it facilitates tracheal tube insertion once the glottis is aligned with the center of the laryngeal inlet on the view field. The infant AOL accepts tracheal tube with an internal diameter between 2.5 and 3.5 mm; while the pediatric one accepts tube with an internal diameter between 3.5 and 5.5 mm. The pediatric AOL easily provided a full view of the glottic opening in our patient with Treacher Collins syndrome, in whom the Macintosh laryngoscopy failed to expose the glottis. Anesthesia resident completed tracheal intubation without difficulty within 40 s. The small-size AOL seems suitable for difficult airways in small children.

Cricoid Pressure Impedes Insertion of, and Ventilation Through, the ProSeal Laryngeal Mask Airway in Anesthetized, Paralyzed Patients

BACKGROUND: We designed this prospective self-controlled study to assess whether cricoid pressure hampers placement of and ventilation through the ProSeal laryngeal mask airway (ProSeal LMA) in anesthetized, paralyzed adult patients. METHODS: After induction of anesthesia, the ProSeal LMA was inserted using the introducer tool with cricoid pressure advanced as far as possible, and the cuff pressure was set at 60 cm H2O. Ventilation adequacy and anatomic position were scored using measures previously described for ProSeal LMA assessment. Airway seal pressure was recorded. Cricoid pressure was then released, the ProSeal LMA further advanced and reseated, and the assessment repeated. RESULTS: Lung ventilation scores, anatomic position scores, and airway seal pressure were significantly better after release of cricoid pressure and reseating of the ProSeal LMA than in the first position, where the ProSeal LMA was seated with cricoid pressure (P < 0.05). Expiratory tidal volume during intermittent positive pressure ventilation was similar with and without cricoid pressure, but peak inspiratory pressure decreased from 28 cm H2O with cricoid pressure to 14 cm H2O without cricoid pressure (P < 0.05). CONCLUSIONS: Cricoid pressure applied before insertion hampered proper placement of the ProSeal LMA. Temporary cricoid pressure release during insertion allowed the device to be advanced to the proper position. After correct placement of the ProSeal LMA, application of cricoid pressure did not change tidal volume, but produced a significant increase in peak inspiratory pressure.

Intravenous remifentanil and propofol for gastroscopy

STUDY OBJECTIVES To evaluate the efficiency and safety of intravenous (i.v.) remifentanil and propofol for gastroscopy in healthy adults. DESIGN Randomized, double-blinded study. SETTING Endoscopy Center, West China Hospital, Sichuan University (Chengdu, Peoples Republic of China). PATIENTS 199 adult ASA physical status I and II patients. INTERVENTIONS Patients were randomly allocated to either the fentanyl group (n = 99) or the remifentanil group (n = 100). Patients received either fentanyl 0.5 microg/kg or remifentanil 0.5 microg/kg, followed by a bolus injection of one mg/kg of propofol. The subsequent doses of propofol were 0.5 mg/kg when the patient was conscious or body movement appeared. MEASUREMENTS Noninvasive blood pressure, heart rate, arterial pulse oxygen saturation, and respiratory rate were recorded before gastroscopy and at two-minute intervals until the end of the gastroscopy procedure. Patients were asked to evaluate their level of cognition using the Digit-Symbol Substitution Test score before gastroscopy and at 10 minutes after discontinuation of the drug injection. MAIN RESULTS Recovery time was significantly shorter in the remifentanil group than in the fentanyl group (P < 0.05). Postoperative Digit-Symbol Substitution Test scores were significantly higher in the remifentanil group than in the fentanyl group (P < 0.01). Total dosage of propofol given in the remifentanil group was significantly less than it was in the fentanyl group (P < 0.01). Frequency of apnea was significantly higher in the remifentanil group (P < 0.05). There were no significant differences in frequency of hypoxemia, bag ventilation, or body movement between the two groups (P > 0.05). CONCLUSIONS Intravenous remifentanil and propofol were more efficient for gastroscopy than i.v. fentanyl and propofol.

Influences of age and gender on dose response and time course of effect of atracurium in anesthetized adult patients.

STUDY OBJECTIVE To determine the influences of age and gender on the dose response and the time course of effect of atracurium. DESIGN Prospective, nonrandomized, clinical comparison. SETTING Operating room, Plastic Surgery Hospital of the Chinese Academy of Medical Sciences and Peking Union Medical College. PATIENTS 72 adult ASA physical status I patients (38 male and 34 female), aged 15 to 59 years, scheduled for elective plastic surgery. INTERVENTIONS Patients were divided into the three groups on the basis of age: Group 1, patients aged 15-29 years (n = 32); Group 2, patients aged 30-40 years (n = 21); and Group 3, patients aged 41-59 years (n = 19). Anesthesia was maintained with 60% nitrous oxide in oxygen, thiopental, and incremental doses of fentanyl as required. The dose-response relationship of atracurium was determined by a cumulative dose-response technique. MEASUREMENTS AND MAIN RESULTS Neuromuscular function was assessed mechanomyographically with train-of-four stimulation at the wrist every 12 seconds and the percentage depression of first twitch (T1) response was used as the study variable. Age and gender significantly affected the dose-response relationship and time course of recovery of atracurium. Advancing age was associated with a reduced effective doses (ED50, ED90, and ED95) of atracurium and a longer duration of action. The effective doses of atracurium were greater, and its duration of action was shorter in men than in women. There were significant differences in the 50%, 90%, and 95% effective dose (ED50, ED90, and ED95) of atracurium, and clinical duration and total duration following administration of atracurium 400 micrograms/kg among the three age groups, and between men and women. CONCLUSIONS Age and gender have significant effects on the dose response and time course of effect of atracurium. Older patients and women are more sensitive to atracurium-induced neuromuscular block than are young patients and men.

Topical anesthesia of the airway using fibreoptic bronchoscope and the MADgic atomizer in patients with predicted difficult intubation.

To the Editor: Whenever difficulty in ventilation and laryngoscopic intubation is anticipated, awake fibreoptic intubation is often the safest option.1 However, effective local anesthesia of the airway is mandatory for patient comfort and subsequent successful instrumentation.2 The “spray as you go” technique using fibreoptic bronchoscope (FOB) provides flexibility in selectively anesthetizing respiratory passages, but cannot provide topical anesthesia as effectively as transtracheal injection of lidocaine.3 This may be related to the fact that local anesthetic injected by the working channel of FOB or epidural catheter cannot be reduced to extremely fine cloud-like particles. The MADgic® atomizer (Wolfe Tory Medical Inc., Salt Lake City, UT, USA) is a new device that has the ability to provide atomized topical solution directly to the airway mucosa.4 One of its disadvantages is the requirement for direct laryngoscopy to provide access to the pharynx, larynx and trachea, which may cause airway stimulation that the awake patient cannot well tolerate. In contrast, exposure of the airway structures using a FOB can attenuate or even avoid direct airway stimuli. We have successfully combined a FOB (Olympus LF-DP or LF-TP, Tokyo, Japan) and a MADgic® atomizer to provide topical anesthesia of the hypopharynx, larynx and trachea before tracheal intubation. This combined technique requires an elastic 5 mm lactoprene tube 3 cm in length. The lumen of the lactoprene tube is well lubricated using a watersoluble lubricant. Both the distal bending section of the FOB and the applicator portion of the MADgic® atomizer are inserted into the lactoprene tube until their tips protrude just beyond the distal end of lactoprene tube (Figure). With local Ethics Committee approval, 15 patients scheduled for elective surgery who had a predicted difficult intubation gave written informed consent to participate in a clinical evaluation of this combined technique. Of the 15 patients, three had limited mouth opening (inter-incisor distance of 18–22 mm), 11 had limited extension of the head, and one patient had micrognathia (thyromental distance of 4.2 cm). Following topical anesthesia of the oropharynx with traditional spray techniques, fentanyl 1.5 μg·kg–1 was administered intravenously and midazolam (dose range 1–8 mg iv) was titrated to the desired level of sedation, with the patient calm, falling asleep if undisturbed, but still able to respond to verbal commands or gentle stimulation. An airway intubator was inserted into the oropharynx, and a jaw thrust or gentle forward pull of the tongue was performed by an assistant. The operator introduced the FOBMADgic® unit through the airway intubator into the hypopharynx. By gentle rotation of the body of the FOB and manipulations of the tip control lever, the tip of the FOB-MADgic® unit was positioned near the bilateral piriform recess and epiglottic vallecula. Then the assistant used the MADgic® atomizer to spray 3 mL of 2% lidocaine in three aliquots onto these targeted areas. After three minutes, the FOBMADgic® unit was again inserted and positioned above the vocal cords. Two percent lidocaine (1 mL) was sprayed onto the vocal cords. This procedure was repeated two to three times until adequate anesthesia of the vocal cords was observed, as evidenced by cessation of the laryngeal response to further lidocaine administration. The FOB-MADgic® unit was then advanced into the trachea and its tip was positioned 2 cm below the vocal cords. Two percent lidocaine 2 mL was sprayed into trachea during inspiration. In five patients requiring nasotracheal intubation, the nasal mucosa of both nostrils was also prepared with lidocaine gel and vasoconstrictor before intubation. The fibreoptic intubation was started five minutes after the tracheal spray of lidocaine. In all patients the FOB-MADgic® unit was successfully directed to the different targeted areas using one CORRESPONDENCE 951