Velislav Slavov

An Algorithm for Difficult Airway Management, Modified for Modern Optical Devices (Airtraq Laryngoscope; LMA CTrach ™)A 2-Year Prospective Validation in Patients for Elective Abdominal, Gynecologic, and Thyroid Surgery

Background: Because algorithms for difficult airway management, including the use of new optical tracheal intubation devices, require prospective evaluation in routine practice, we prospectively assessed an algorithm for difficult airway management that included two new airway devices. Methods: After 6 months of instruction, training, and clinical testing, 15 senior anesthesiologists were asked to use an established algorithm for difficult airway management in anesthetized and paralyzed patients. Abdominal, gynecologic, and thyroid surgery patients were enrolled. Emergency, obstetric, and patients considered at risk of aspiration were excluded. If tracheal intubation using a Macintosh laryngoscope was impossible, the Airtraq laryngoscope (VYGON, Ecouen, France) was recommended as a first step and the LMA CTrach™ (SEBAC, Pantin, France) as a second. A gum elastic bougie was advocated to facilitate tracheal access with the Macintosh and Airtraq laryngoscopes. If ventilation with a facemask was impossible, the LMA CTrach™ was to be used, followed, if necessary, by transtracheal oxygenation. Patient characteristics, adherence to the algorithm, efficacy, and early complications were recorded. Results: Overall, 12,225 patients were included during 2 yr. Intubation was achieved using the Macintosh laryngoscope in 98% cases. In the remainder of the cases (236), a gum elastic bougie was used with the Macintosh laryngoscope in 207 (84%). The Airtraq laryngoscope success rate was 97% (27 of 28). The LMA CTrach™ allowed rescue ventilation (n = 2) and visually directed tracheal intubation (n = 3). In one patient, ventilation by facemask was impossible, and the LMA CTrach™ was used successfully. Conclusions: Tracheal intubation can be achieved successfully in a large cohort of patients with a new management algorithm incorporating the use of gum elastic bougie, Airtraq, and LMA CTrach™ devices.

Effects of an intubating dose of succinylcholine and rocuronium on the larynx and diaphragm: an electromyographic study in humans.

BACKGROUND Paralysis of the vocal cords is one objective of using relaxants to facilitate tracheal intubation. This study compares the neuromuscular blocking effect of succinylcholine and rocuronium on the larynx, the diaphragm, and the adductor pollicis muscle. METHODS Electromyographic response was used to compare the neuromuscular blocking effect of succinylcholine and rocuronium on the laryngeal adductor muscles, the diaphragm, and the adductor pollicis muscle. Sixteen patients undergoing elective surgery were anesthetized with propofol and fentanyl, and their tracheas were intubated without neuromuscular blocking agents. The recurrent laryngeal and phrenic nerves were stimulated at the neck. The electromyographic response was recorded from electrodes placed on the endotracheal tube and intercostally before and after administration of 1 mg/kg succinylcholine or 0.6 mg/kg rocuronium. RESULTS The maximum effect was greater at the adductor pollicis (100 and 99%) than at the larynx (96 and 97%) and the diaphragm (94 and 96%) after administration of succinylcholine and rocuronium, respectively (P < or = 0.05). Onset time was not different between the larynx (58+/-10 s), the diaphragm (57+/-8 s), and the adductor pollicis (54+/-13 s), after succinylcholine (all mean +/- SD). After rocuronium, onset time was 124+/-39 s at the larynx, 130+/-44 s at the diaphragm, and 115+/-21 s at the adductor pollicis. After succinylcholine administration, time to 90% recovery was 8.3+/-3.2, 7.2+/-3.5, and 9.1+/-3.0 min at the larynx, the diaphragm, and the adductor pollicis, respectively. Time to 90% recovery after rocuronium administration was 34.9+/-7.6, 30.4+/-4.2, and 49.1+/-11.4 min at the larynx, the diaphragm, and the adductor pollicis, respectively. CONCLUSION Neuromuscular blocking effect of muscle relaxants on the larynx can be measured noninvasively by electromyography. Although the larynx appears to be resistant to muscle relaxants, we could not demonstrate that its onset time differed from that of peripheral muscles.

Soleus neurotomy for treatment of the spastic equinus foot

OBJECTIVEThis prospective, nonrandomized, noncontrolled study was performed to evaluate the results of a new type of neurotomy, namely the soleus neurotomy, for treatment of the spastic equinus foot. METHODSBetween May 1996 and March 1998, 46 patients were treated for a spastic equinus foot. Clinical status, spasticity (Ashworth Scale score), and kinematic parameters of the gait were determined before and after surgery. The neurotomy was performed on the upper nerve of the soleus in all cases and was associated with other neurotomies (lower nerve of the soleus, 21 patients; gastrocnemius, 9 patients, tibialis posterior, 18 patients; flexor hallucis longus, 16 patients; and flexor digitorum longus, 17 patients). RESULTSThe mean follow-up period was 15 months (range, 8–28 mo). The equinus deformity disappeared clinically in all patients. Before the operation, all patients had an Ashworth Scale score of 2, with an inexhaustible clonus present on knee extension and persisting with knee flexion (Tardieu Scale score, 4), which was abolished in 95% of the patients after surgery. Two patients still had some clonus on knee extension; this did not interfere with their clinical improvement. Knee recurvatum disappeared in eight patients. Analysis of kinematic parameters demonstrated a statistically significant increase in joint motion of the second rocker (P = 0.0026) of the ankle during stance. The duration of the stance or swing phase, length of the walking cycle, and velocity or rate of spontaneous walking were not significantly modified. CONCLUSIONThe study demonstrated that soleus neurotomy is effective for the treatment of spastic equinus foot, leading to abolition of spasticity and improvement in the range of ankle motion during the stance phase of gait.

Systolic blood pressure, not BIS, is associated with movement during laryngoscopy and intubation.

ObjectiveTb compare bispectral index (BIS) values to hemodynamic variations, in order to evaluate adequacy of anesthesia during orotracheal intubation with muscle relaxants.MethodsForty-one patients ASA I–II, scheduled for elective peripheral surgery under general anesthesia with tracheal intubation were enrolled in the study. Fentanyl/thiopental followed by vecuronium were used for induction. Onset of relaxation was monitored at the orbicularis occuli (OO) muscle using train-of-four stimulation. Intubation was performed when no response at the OO was detected visually. Intubating conditions were noted. The “isolated forearm” technique was used to detect movement during laryngoscopy/intubation. BIS values, pulse rate (PR), and systolic pressure were recorded before induction, during laryngoscopy/intubation and 60 sec after intubation.ResultsAlthough intubating conditions were clinically adequate for all patients, ten out of 41 had movement of the isolated arm during laryngoscopy/intubation. BIS values were not significantly different for these patients: 67 (55–83) compared to those who had no movement: 60 (35–80), P = 0.6. During laryngoscopy, PR increased for all patients while systolic pressure increased significantly only in patients who moved: 125 (100–136) mmHg vs those who did not: 108 (67–140), P < 0.05.ConclusionSystolic pressure elevations were associated with inadequate anesthesia as evaluated by the “isolated forearm” technique, during laryngoscopy/intubation. BIS values were not different between groups, suggesting that systolic blood pressure may be a better predictor of inadequate anesthesia under the circumstances described.RésuméObjectifÉvaluer l’analyse blspectrale (BIS) en la comparant avec les variations hémodynamiques lors de l’intubation orotrachéale avec curarisation.MéthodeQuarante et un patients de classe ASA I–II admis pour une intervention chirurgicale périphérique programmée sous anesthésie générale avec intubation et curarisation ont été inclus dans l’étude. Linduction a été effectuée avec du fentanyl/thiopental suivi de vécuronium pour faciliter l’intubation. L’installation du bloc neuromusculaire a été contrôlée à l’orbiculaire de l’œil avec des stimulations en trainde-quatre. L’intubation a été réalisée à la disparition de la réponse observée de l’orbiculaire de l’œil et les conditions d’intubation ont été notées. La technique de l’avant-bras isolé avec un garrot a été utilisée pour détecter les mouvements lors des stimuli nociceptifs alors que les patients étaient curarisés. Les valeurs du BIS, la fréquence cardiaque, et la pression artérielle systolique ont été enregistrées: avant l’induction, lors de la laryngoscopie/intubation et 60 sec après l’intubation.RésultatsLes conditions d’intubation étaient cliniquement satisfaisantes pour tous les patients. Dix patients sur 41 ont eu des mouvements de l’avant-bras durant la laryngoscope et/ou l’intubation. Les valeurs du BIS chez ces patients: 67 (55–83) n’étaient pas significativement différentes de celles des patients n’ayant pas bougé: 61 (39–80) P = 0,6. La fréquence cardiaque a augmenté chez tous les patients tandis que la pression artérielle systolique était significativement plus basse chez les patients qui n’ont pas bougé: 108 (67–140) mmHg contre: 125 (100–136), (P < 0,05).ConclusionDans les conditions de cette étude, les variations de la pression artérielle systolique ont été plus significatives que les variations du BIS pour prédire les mouvements du bras isolé lors de l’intubation chez les patients curarisés.

Neostigmine reversal of vecuronium neuromuscular block and the influence of renal failure.

The duration of clinical relaxation induced by vecuronium and reversal by neostigmine was studied in 40 patients with renal failure (RF) and 40 patients with normal renal function (NL) under general anesthesia.Patients were premedicated with flunitrazepam, and anesthesia commenced with fentanyl 1-2 micro gram/kg, thiopental 5-8 mg/kg, and vecuronium 0.1 mg/kg. Anesthesia was maintained with 60% nitrous oxide in oxygen, isoflurane 0.3%-1.0% end-tidal concentration, and 1 micro gram/kg fentanyl every 20-30 min. Neuromuscular block was reversed by the administration of intravenous neostigmine 40 mg/kg at the time of reappearance of either two or four responses to the train-of-four (TOF) stimulation. Monitoring of neuromuscular function consisted of supramaximal TOF stimulation of the ulnar nerve and the evoked thumb response was registered using a force transducer. Spontaneous recovery time, reversal time, and the time to recovery of TOF ratio to 0.7 were recorded. RF did not prolong the vecuronium neuromuscular blocking effect, reversal was achieved at the same rate in NL as in RF, and the duration of reversal of neuromuscular blocking effect of vecuronium was not influenced by the time of administration of neostigmine. Therefore, the neuromuscular blocking effect of a tracheal intubating dose of vecuronium can be reversed at the same rate in patients with end-stage RF as in patients with normal kidney function. (Anesth Analg 1996;82:134-8)

Pharmacokinetics and Pharmacodynamics of Rapacuronium in Patients with Cirrhosis

BACKGROUND Delayed elimination kinetics of steroidal neuromuscular blocking agents have been observed in patients with cirrhosis. Like other steroidal muscle relaxants, rapacuronium may, in part, be eliminated by the liver. To determine the influence of liver disease on its neuromuscular blocking effect, we studied the pharmacokinetics and pharmacodynamics of rapacuronium in patients with cirrhosis. METHODS Sixteen patients undergoing elective surgery or endoscopy with general anesthesia, eight with cirrhosis and eight with normal liver function, were studied. Anesthesia was induced with fentanyl 2 microg/kg and thiopental 5-7 mg/kg and maintained with 60% nitrous oxide and 0.6-0.8% isoflurane in oxygen and repeated doses of fentanyl 1 microg/kg. Rapacuronium 1.5 mg/kg was administered intravenously before tracheal intubation. Thumb adduction force evoked by supramaximal ulnar nerve stimulation was recorded in 16 patients. Venous blood was sampled at frequent intervals for 8 h. Rapacuronium and its breakdown product Org 9488 were measured in plasma by high-pressure liquid chromatography. Values are reported as median (range). RESULTS The central volume of distribution was increased to 131 (104-141) ml/kg in patients with cirrhosis (P < 0.01), compared with 75 (47-146) ml/kg in controls. The total apparent volume of distribution was also increased (P < 0.05) to 331 (284-488) ml/kg in patients with cirrhosis, compared with 221 (124-285) ml/kg in controls. The elimination half-life was 88 (77-102) min in controls and 90 (76-117) min in patients with cirrhosis. Plasma clearance was increased (P < 0.05) to 6.9 (6.1-8.9) ml x min(-1) x kg(-1) in patients with cirrhosis, compared with 5.3 (4.2-8.4) ml x min(-1) x kg(-1) in controls. Rapacuronium neuromuscular blocking effect was similar between the two groups. Onset time was 65 (40-110) s in controls and of 60 (52-240) s in patients with cirrhosis. Time to return to 90% of thumb adduction force control value was of 49 (28-80) min in controls and 47 (28-71) min in patients with cirrhosis. CONCLUSION The neuromuscular blocking effect of a single bolus dose of rapacuronium in patients with cirrhosis is not different from that of patients with normal hepatic function. No decrease in plasma clearance of rapacuronium was observed in patients with cirrhosis.

Comparison of the Neuromuscular Blocking Effect of Atracurium and Vecuronium on the Adductor Pollicis and the Geniohyoid Muscle in Humans

Background Residual paralysis of suprahyoid muscles may occur when the adductor pollicis response has completely recovered after the administration of a neuromuscular blocking agent. The response of the geniohyoid muscle to intubating doses of muscle relaxants is evaluated and compared to that of adductor pollicis. Methods Sixteen patients undergoing elective surgery under general anesthesia were given 5–7 mg *symbol* kg sup ‐1 thiopental and 2 micro gram *symbol* kg sup ‐1 fentanyl intravenously for induction of anesthesia. Eight (half) patients then received 0.5 mg *symbol* kg sup ‐1 atracurium, and the other eight received 0.1 mg *symbol* kg sup ‐1 vecuronium. The evoked response (twitch height, TH) of the adductor pollicis was monitored by measuring the integrated electromyographic response (AP EMG) on one limb and the mechanical response, using a force transducer (AP force), on the other. The activity of geniohyoid muscle (GH EMG) was measured using submental percutaneous electrodes. The following variables were measured: maximal TH depression; onset time for neuromuscular blockade to 50%, 90%, and maximal TH depression (OT50, OT90, and OTmax); times between administration of neuromuscular blocking agent and TH recovery to 10%, 25%, 50%, 75%, and 90% of control; and time for return of train‐of‐four ratio to return to 0.7. Results The principal findings were (1) OTmax was significantly (P < 0.01) shorter for geniohyoid than for adductor pollicis after either atracurium or vecuronium (OTmax was 216, 256, and 175 s for AP force, AP EMG, and GH EMG, with atracurium and 181, 199, and 144 s with vecuronium, respectively), and (2) the evoked EMG of geniohyoid recovered at the same speed as the EMG of adductor pollicis after an intubating dose of atracurium or vecuronium (recovery of TH to 75% of control at 50, 48, 42 min with AP force, AP EMG, and GH EMG with atracurium and 46, 45, and 42 min with vecuronium, respectively). Conclusions Once the adductor pollicis response has returned to normal values after a single intubating dose of atracurium or vecuronium, the risk of residual depression of the TH of the geniohyoid muscle, one of the principal muscles contributing to airway patency, appears unlikely.