Guidelines and algorithms for managing the difficult airway. / Guías y algoritmos para el manejo de la vía aérea difícil.

The difficult airway constitutes a continuous challenge for anesthesiologists. Guidelines and algorithms are key to preserving patient safety, by recommending specific plans and strategies that address predicted or unexpected difficult airway. However, there are currently no "gold standard" algorithms or universally accepted standards. The aim of this article is to present a synthesis of the recommendations of the main guidelines and difficult airway algorithms.

Catastrophic complication of an interscalene catheter for continuous peripheral nerve block analgesia.

We report a catastrophic postoperative complication of a prolonged interscalene block performed under general anaesthesia. The course of the anaesthetic was uneventful and the patient remained stable during his stay in the recovery area with the operative extremity paralysed and insensate. No further local anaesthetic was administered until later that day when the patient received 10 ml bupivacaine 0.25% through the catheter. Upon completion of the top-up dose, no change in the patient's status was noticed. The patient was next assessed 6.5 h later when he was found dead in his bed. A postmortem CT scan revealed the catheter to be sited intrathecally, presumably the result of dural sleeve penetration.

Parameters affecting pharyngeal response to genioglossus stimulation in sleep apnoea.

Chronic stimulation of the hypoglossus nerve may provide a new treatment modality for obstructive sleep apnoea (OSA). In previous studies we observed large differences in response to stimulation of the genioglossus (GG). We hypothesised that both individual patient characteristics and the area of the GG stimulated are responsible for these differences. In the present study, we compared the response to GG electrical stimulation at the anterior area (GGa-ES), which activates the whole GG and the posterior area (GGp-ES), which activates preferentially the longitudinal fibres. Studies were performed in 14 propofol-sedated OSA patients. The parameters evaluated included cephalometry, pressure-flow relationship and pharyngeal shape and compliance assessed by pharyngoscopy. Compared with GGa-ES, GGp-ES resulted in significantly larger decreases in the critical value of end-expiratory pressure (P(crit)) (from 3.8 ± 2.2 to 2.9 ± 3.3 and -2.0 ± 3.9 cmH(2)O, respectively (p<0.001)). Both tongue size and velopharyngeal shape (anteroposterior to lateral ratio) correlated significantly with the decrease in P(crit) during GGp-ES (R = 0.53 and -0.66, respectively; p<0.05). In the patients with the larger tongue size (n = 7), the decrease in P(crit) reached 8.0 ± 2.2 cmH(2)O during GGp-ES. We conclude that directing stimulation to longitudinal fibres of the GG improves the flow-mechanical effect. In addition, patients with large tongues and narrow pharynx tend to respond better to GGp-ES.

Gastro-Laryngeal Tube for endoscopic retrograde cholangiopancreatography: a preliminary report.

The Gastro-Laryngeal Tube is a modification of the Laryngeal Tube that provides a dedicated channel for the insertion of a gastroscope. In this study of 30 patients undergoing general anaesthesia for endoscopic retrograde cholangiopancreatography, we evaluated both the effectiveness of airway management with a Gastro Laryngeal Tube and the feasibility of performing it using the endoscopic channel. The Gastro Laryngeal Tube was inserted successfully in all patients, in 27 patients at the first attempt. The mean (SD) time to achieve an effective airway was 26 (6) s. Mean (SD) inspiratory and expiratory tidal volumes were 336 (57) ml and 312 (72) ml, respectively, and oropharyngeal leak pressure was 33.7 (2) cmH(2)O. These data suggest that the Gastro Laryngeal Tube is an effective and secure device for airway management and for use during performance of endoscopic retrograde cholangiopancreatography.

Collapsibility of the relaxed pharynx and risk of sleep apnoea.

The present study measured hypotonic pharyngeal collapsibility in subjects not known to have obstructive sleep apnoea (OSA), and assessed the variables that affect collapsibility and the relationship with OSA. The critical value of positive end-expiratory pressure (P(crit)) was measured under the hypotonic condition of anaesthesia in 227 subjects who underwent elective surgery. The risk of OSA in this population was estimated using the Berlin questionnaire. The mean P(crit) for all subjects was positive (above atmospheric), ranging from 0.69 (95% confidence interval (CI) -7.39-8.77) to 4.0 (CI -4.82-12.82) cmH(2)O for subjects with low and high prevalence of OSA, respectively. P(crit) < or = -5 cmH(2)O was only found in 3.1% of the study subjects. In the general population, P(crit) was similar in males and females and correlated positively with increasing age, while a correlation with neck circumference was found only in males. P(crit )accounted for only 12.25% of the variability in OSA risk score. In conclusion, subjects with high critical value of positive end-expiratory pressure are at an increased risk for developing obstructive sleep apnoea. However, the human pharynx is prone to collapse and occludes in most people in the absence of neuromuscular support. Therefore, in most subjects, the level of neuromuscular activity may ultimately determine the occurrence of sleep apnoea.

[The laryngeal tube]. / El tubo laríngeo.

The laryngeal tube (VBM Medizintechnic GmbH, Sulz, Germany) is a supraglottic device designed for airway management in spontaneous or positive-pressure ventilation during anesthesia or in cardiopulmonary resuscitation. Currently, the tube is available in 4 versions: the standard laryngeal tube, the disposable tube (LT-D), the dual-lumen tube (with a tube for suction) (LTS II), and the disposable LTS (LTS-D). The design of the tube has been modified several times. It is easy to insert and the airway seal is more effective than that of the laryngeal mask. The incidence of complications is similar for both devices, though use of the laryngeal tube requires more adjustments. The standard tube is somewhat less effective than the ProSeal laryngeal mask, though the new LTS II has been improved considerably. The laryngeal tube is effective as an aid to management of the difficult airway. We reviewed the literature indexed on MEDLINE through December 2006 using the search terms laryngeal tube, anesthesia, equipment, and airway.

Does adding intravenous fentanyl to caudal block in children enhance the efficacy of multimodal analgesia as reflected in the plasma level of catecholamines?

BACKGROUND AND OBJECTIVE: Several studies showed that single analgesic modality management can attenuate perioperative stress, but little is known about the effect of multimodal analgesia on catecholamine responses to surgical trauma in children. METHODS: Fifty children (American Society of Anesthesiologists Grade I or II) were randomly allocated to one of two groups: one received general anaesthesia and a caudal block (control group), and one group was given general anaesthesia, caudal block and intravenous (i.v.) fentanyl 2 microg kg(-1) (fentanyl group). Plasma epinephrine and norepinephrine concentrations were measured three times during the perioperative period: at induction time (T(0)), at the end of surgery (T(1)) and when the children were fully awake in the postanaesthesia care unit (T(2)). RESULTS: There was a significant reduction in the catecholamine levels in the two groups when (T(1)) and (T(2)) were compared with T(0). When plasma epinephrine levels (at T(0), T(1) and T(2)) between the two groups were compared, a statistically significant reduction at T(2) was obtained in the fentanyl group, when compared with the control group. However, plasma norepinephrine levels showed no statistically significant difference between the two groups (at T(0), T(1) and T(2)). CONCLUSION: These findings suggest that the multimodal analgesic approach of adding i.v. low-dose fentanyl to a caudal block may decrease the plasma epinephrine release in children undergoing inguinal herniotomy.

Vancomycin sequestration during cardiopulmonary bypass surgery.

OBJECTIVE: The present study was designed to analyze vancomycin disposition in adult patients undergoing coronary bypass grafting during and following cardiopulmonary bypass (CPB). METHODS: Coronary bypass surgery was performed on 11 adults with a mean age (SD) of 62.9 (9.0) years old, who received a mean (SD) vancomycin prophylactic dose of 12.7 (1.0) mg/kg in a mean period of 41 (0.7) min. Using a two-compartment open model for pharmacokinetic analysis, the following parameters were obtained: alpha half-life, minutes (t(1/2alpha)); beta half-life, hours (t(1/2beta)); apparent volume of distribution, (V(d) l/kg); volume of the central compartment, (V(c) l/kg), constant between the "central to the peripheral" compartment, (k(12)); constant between the "peripheral to the central" compartment, (k(21)); total area under the concentration-time curve, (AUC mg/lxh) and a vancomycin clearance, (Cl(van) ml/min), respectively. RESULTS: The mean (SD) calculated pharmacokinetic parameters were: t(1/2alpha)17.6 (6) min, t(1/2beta) 8.4 (3.8) h, V(d) 0.803 (0.259) l/kg, V(c) 0.270 (0.162) l/kg, k(12) 0.03 (0.015), k(21) 0.012 (0.012), total AUC 10377.2 (3687.6) mg/lxh. The mean (SD) vancomycin clearance by the CPB machine was 9.51 (2.66) l/h, and the mean (SD) total vancomycin sequestrated by CPB was 331.7 (84) mg. A significant difference (6.3%; p = 0.001) was measured between the mean measured AUC during CPB (1088.1 +/- 253.9) and the same calculated parameter (1160.2 +/- 282). Five minutes after starting CPB, a decrease in vancomycin level was detected; this difference was found to be nearly 11% in absolute values. CONCLUSIONS: This confirmatory study demonstrated that the vancomycin blood concentrations obtained during the study allow recommending a safety prophylactic dose of 12mg/kg in adults who undergo open-heart surgery under CPB conditions. Sequestration of vancomycin by the oxygenator or/and tubing system of the CPB machine had occurred and had been measured in this study.

The use of technologies to decrease peri-operative allogenic blood transfusion: results of practice variation in Israel.

BACKGROUND: Concern about the side effects of allogeneic blood transfusion has led to increased interest in methods of minimizing peri-operative transfusion. Technologies to minimize allogeneic transfusion include drugs such as aprotinin, desmopressin, tranexamic acid and erythropoietin, and techniques such as acute normovolemic hemodilution, cell salvage and autologous pre-donation. OBJECTIVE: To survey the current use in Israel of these seven technologies to minimize allogeneic blood transfusion. METHODS: Our survey was conducted in 1996-97 in all hospitals in Israel with more than 50 beds and at least one of the following departments: cardiac or vascular surgery, orthopedics, or urology. All departments surveyed were asked: a) whether the technologies were currently being used or not, b) the degree of use, and c) the factors influencing their use and non-use. The survey was targeted at the heads of these departments. RESULTS: Pharmaceuticals to reduce allogeneic blood transfusion were used in a much higher proportion in cardiac surgery departments than in the other three departments. Pre-operative blood donation was used in few of the cardiac, urologic and vascular surgery departments compared to its moderate use in orthopedic departments. The use of acute normovolemic hemodilution was reported in a majority of the cardiac departments only. Moderate use of cell salvage was reported in all departments except urology where it was not used at all. CONCLUSION: There is considerable practice variation in the use of technologies to minimize exposure to peri-operative allogeneic blood transfusion in Israel.

Hemodynamic instability in chronic fatigue syndrome: indices and diagnostic significance.

OBJECTIVES: To evaluate the cardiovascular response to postural challenge in patients with chronic fatigue syndrome (CFS) and to determine whether the degree of instability of the cardiovascular response may aid in diagnosing CFS. METHODS: Patients with CFS (n = 25) and their age- and gender-matched healthy controls (n = 37), patients with fibromyalgia (n = 30), generalized anxiety disorder (n = 15), and essential hypertension (n = 20) were evaluated with the aid of a standardized tilt test. The blood pressure (BP) and heart rate (HR) were recorded during 10 minutes of recumbence and 30 minutes of head-up tilt. We designated BP changes as the differences between successive BP values and the last recumbent BP. The average and standard deviation (SD) were calculated. Time curves of BP differences were loaded into a computerized image analyzer, and their outline ratios and fractal dimensions were measured. HR changes were determined similarly. The average and SD of the parameters were calculated, and intergroup comparisons were performed. RESULTS: On multivariate analysis, the independent predictors of CFS patients versus healthy controls were the fractal dimension of absolute values of the systolic BP changes (SYST-FD.abs), the standard deviation of the current values of the systolic BP changes (SYST-SD.cur), and the standard deviation of the current values of the heart rate changes (HR-SD.cur). The following equation was deduced to calculate the hemodynamic instability score (HIS) in the individual patient: HIS = 64.3303 + (SYST-FD.abs x -68.0135) + (SYST-SD.cur x 111.3726) + (HR-SD.cur x 60.4164). The best cutoff differentiating CFS from the healthy controls was -0.98. HIS values >-0.98 were associated with CFS (sensitivity 97%, specificity 97%). The HIS differed significantly between CFS and other groups (P <.0001) except for generalized anxiety disorder. Group averages (SD) of HIS were CFS = +3.72 (5.02), healthy = -4.62 (2.26), fibromyalgia = -3.27 (2.63), hypertension = -5.53 (2.24), and generalized anxiety disorder = +1.08 (5.2). CONCLUSION: The HIS adds objective criteria confirming the diagnosis of CFS.

Acupuncture versus ondansetron in the prevention of postoperative vomiting. A study of children undergoing dental surgery.

This study compares the anti-emetic effect of acupuncture with that of ondansetron and a placebo. Ninety children undergoing dental treatment under general anaesthesia were randomly allocated to one of the three equal groups, to receive acupuncture needle insertion, intravenous ondansetron 0.15 mg x kg(-1) or a placebo. Parental satisfaction scores and the incidence of emetic episodes were recorded. A significant difference was found in the number of patients who vomited and the total number of the emetic episodes when comparing the two treatment groups with the placebo group (p < 0.0001). A significant difference was also found between the treatment groups and the placebo group with respect to parental satisfaction score (p < 0.03). We conclude that traditional Chinese acupuncture is a valid non-pharmacological alternative anti-emetic treatment that can be recommended as a prophylactic technique in children undergoing dental surgery under general anaesthesia.

Cardiovascular response to upright tilt in fibromyalgia differs from that in chronic fatigue syndrome.

OBJECTIVE: To compare the cardiovascular response during postural challenge of patients with fibromyalgia (FM) to those with chronic fatigue syndrome (CFS). METHODS: Age and sex matched patients were studied, 38 with FM, 30 with CFS, and 37 healthy subjects. Blood pressure (BP) and heart rate (HR) were recorded during 10 min of recumbence and 30 min of head-up tilt. Differences between successive BP values and the last recumbent BP, their average, and standard deviation (SD) were calculated. Time curves of BP differences were analyzed by computer and their outline ratios (OR) and fractal dimensions (FD) were measured. HR differences were determined similarly. Based on the latter measurements, each subject's discriminant score (DS) was computed. RESULTS: For patients and controls average DS values were: FM: -3.68 (SD 2.7), CFS: 3.72 (SD 5.02), and healthy controls: -4.62 (SD 2.24). DS values differed significantly between FM and CFS (p < 0.0001). Subgroups of FM patients with and without fatigue had comparable DS values. CONCLUSION: The DS confers numerical expression to the cardiovascular response during postural challenge. DS values in FM were significantly different from DS in CFS, suggesting that homeostatic responses in FM and CFS are dissimilar. This observation challenges the hypothesis that FM and CFS share a common derangement of the stress-response system.