RESUMEN
UNLABELLED: The National Institute for Occupational Safety and Health-recommended exposure levels for nitrous oxide exposure are 25 ppm as a time-weighted average over the time of exposure. The exposure limit for halogenated anesthetics (without concomitant nitrous oxide exposure) is 2 ppm. Inhaled sevoflurane provides an alternative to i.v. induction of anesthesia. However, the inadvertent release of anesthetic gases into the room is likely to be greater than that with induction involving i.v. anesthetics. We therefore evaluated anesthesiologist exposure during four different induction techniques. Eighty patients were assigned to one of the induction groups to receive: 1) sevoflurane and nitrous oxide from a rebreathing bag, 2) sevoflurane and nitrous oxide from a circle circuit, 3) propofol 3 mg/kg, and 4) thiopental sodium 5 mg/kg. Anesthesia was maintained with sevoflurane and nitrous oxide via a laryngeal mask. Trace concentrations were measured directly from the breathing zone of the anesthesiologist. During induction, peak concentrations of sevoflurane and nitrous oxide with the two i.v. methods rarely exceeded 2 ppm sevoflurane and 50 ppm nitrous oxide. Concentrations during the two inhalation methods were generally <20 ppm sevoflurane and 100 ppm nitrous oxide. During maintenance, median values were near 2 ppm sevoflurane and 50 ppm nitrous oxide in all groups. Sevoflurane concentrations during inhaled induction frequently exceeded the National Institute for Occupational Safety and Health-recommended exposure ceiling of 2 ppm but mostly remained <20 ppm. Exposure during the maintenance phase of anesthesia also frequently exceeded the 2-ppm ceiling. We conclude that operating room anesthetic vapor concentrations are increased during inhaled inductions and remain increased with laryngeal mask ventilation. IMPLICATIONS: We compared waste gas concentrations to sevoflurane and nitrous oxide during four different induction methods. During inhaled induction with a rebreathing bag or a circle circuit system, waste gas concentrations frequently exceed National Institute for Occupational Safety and Health limits of 2 ppm sevoflurane and 50 ppm nitrous oxide. Therefore, we recommend that people at risk (e.g., women of child-bearing age) should pay great attention when using this technique.
Asunto(s)
Contaminación del Aire Interior/análisis , Anestesia Obstétrica/métodos , Anestésicos por Inhalación/análisis , Éteres Metílicos/análisis , Óxido Nitroso/análisis , Exposición Profesional/análisis , Anestesiología/métodos , Femenino , Humanos , SevofluranoRESUMEN
Clonidine in spinal and epidural blocks prolongs anesthesia, but can cause hypotension and bradycardia. The aim of our study was to compare hemodynamic and analgesic effects of spinal versus epidural clonidine alone and after repetitive dosing. In a prospective, randomized, double-blind study, we evaluated 40 patients scheduled for lower extremity orthopedic surgery under continuous spinal or epidural anesthesia with bupivacaine 0.5% (initial dose 5 mg and 50 mg, respectively). In either spinal or epidural technique one-half of patients received clonidine (150 micrograms) in addition to bupivacaine. Repeat doses of the same anesthetic mixture were allowed in cases of subsequent pain. Mean arterial pressure (MAP) and heart rate were recorded for 6 h after each injection. Duration of clinically useful anesthesia was defined as the time from drug administration to first sensation of pain. Intrathecal, but not epidural, clonidine decreased MAP significantly compared with bupivacaine alone. MAP after intrathecal clonidine with bupivacaine was lower than epidural clonidine with bupivacaine 5 and 6 h after injection. Repetitive administration caused no further decrease in MAP. Onset time required to surgical anesthesia (sensory block of T11) did not differ among the four groups. Duration of spinal and epidural anesthesia was increased more than two fold by clonidine. In summary, the addition of clonidine prolongs analgesia by either route. These results may be explained by clonidine's sites of action in hemodynamic control and the density of bupivacaine-induced block.
Asunto(s)
Anestesia Epidural , Anestesia Raquidea , Presión Sanguínea/efectos de los fármacos , Clonidina/farmacología , Frecuencia Cardíaca/efectos de los fármacos , Anciano , Bupivacaína/farmacología , Clonidina/administración & dosificación , Depresión Química , Femenino , Prótesis de Cadera , Humanos , MasculinoRESUMEN
BACKGROUND: Stenotic processes of the tracheobronchial system may lead to dyspnoea that can become lift-threatening. To restore sufficient function of the blocked airway, a silicone stent can be inserted. The anaesthesia techniques used for this intervention so far have been complicated. The object of this study was to determine whether the super-imposed high-frequency jet ventilation (SHFJV) via the jet laryngoscope originally designed for microlaryngeal surgery can be utilized for endoluminal stent insertion. METHODS: In 12 patients with acute respiratory insufficiency (ASA 3-5) due to stenosis of the tracheobronchial system, an endoluminal silicone stent was inserted through the jet laryngoscope while the patient was ventilated using SHFJV: RESULTS: A significant rise in paO2 readings prior to the jet ventilation and subsequent measurements was observed. The CO2 elimination was good (average paCO2 31.5 +/- 7.5-53.1 +/- 14 mmHg). Variably high paCO2 readings during stent insertion were related to the respective surgical phases. At the end of the surgical manipulation, all patients had sufficient spontaneous ventilation. CONCLUSIONS: First clinical applications of the jet laryngoscope combined with superimposed jet ventilation for stent insertion demonstrated satisfactory results. Not only were the patients ventilated throughout the procedure, but CO2 elimination was also satisfactory. Superimposed jet ventilation provides a sufficient tidal volume with low ventilation pressures, and therefore oxygenation and CO2 elimination are unproblematic. SHFJV enables the anaesthetist to ventilate the patient nearly continuously with minimal phases of apnoea. The only apnoea phases, as with any other method, occur during surgical manipulation while inserting the stent and thus blocking the airway. We believe that the jet laryngoscope with SHFJV presents a distinct advantage for both anaesthetist and surgeon when inserting stents in the tracheobronchial system.
Asunto(s)
Bronquios , Ventilación con Chorro de Alta Frecuencia , Laringoscopios , Insuficiencia Respiratoria/terapia , Stents , Tráquea , Enfermedad Aguda , HumanosRESUMEN
Continuous epidural anesthesia (CEA) is generally accepted as a routine method of regional anesthesia while there has been only limited application of continuous spinal anesthesia (CSA), due mainly to a lack of adequate spinal catheters. With the introduction of a new, ultra-thin spinal catheter (32 G) inserted via a thin puncture needle, some of the complications reported after CSA can be eliminated. We studied CSA versus CEA in lower-extremity operations. METHODS. We evaluated 33 patients in a prospective, randomized study. All were comparable with respect to age, anesthetic risk (ASA II-III), and pre-existing diseases. The only exclusion criterium was the presence of a coagulation disturbance. The CSA group consisted of 17 patients (mean age 75.5 +/- 0.1 year); 26 G puncture needle and 32 G catheter were used. The CEA group consisted of 16 patients (mean age 73.8 +/- 11.0 years); an 18 G puncture needle and 22 G epidural catheter with a stylet were inserted with the loss-of-resistance technique. Both catheters were placed with the patient in a sitting position and left in place for 24 h in order to administer local anesthetics (LA) for postoperative analgesia as required. Hemodynamic parameters-mean arterial pressure (MAP) and heart rate (HR)-were compared in each group at 5-min intervals for 30 min after administration of local anesthetic and at 10-min intervals during the operation. Additionally, the ECG, pulse oximetry, respiratory rate, diuresis, and blood gases were monitored. After placement of the catheter, patients in the CSA group received 1.9 ml (+/- 0.2) bupivacaine HCl 0.5%. Patients in the CEA group received 12.6 ml (+/- 2.5) bupivacaine HCl 0.5%. For statistical evaluation of the data we used mean values, standard deviation (+/-), the Kruscal-Wallis procedure, and Student's t-test for unpaired data. P less than 0.05 was considered significant. RESULTS. The mAPs in the CSA group generally remained lower than those of the CEA group. However, over the course of the operation as well as after repeated injections, the difference between the two groups decreased. Only at 5 min after administration of the initial dose was a statistically significant difference in blood pressures between the two groups observed. A clinically relevant, rapid decrease in blood pressure due to relatively high doses of LA was seen in 1 case in each group. The first reinjection of LA after the initial dose was after 1.9 h in the CSA group (bupivacaine HCl 0.5% 1 +/- 0.3 ml) and after 1.8 h in the CEA group (bupivacaine HCl 0.5% 4.5 +/- 1 ml). The total dose of bupivacaine in the CSA group was 0.18 ml/kg per hour versus 0.8 ml/kg in the CEA group. No post-dural puncture headache was observed in the CSA group. DISCUSSION. The catheter designed for CSA is easy to use, although because of its small diameter a certain manual dexterity is required. In addition, CSA resulted in a more rapid onset of action and more pronounced sensorimotor blockade than did CEA. Hemodynamic alterations and side effects were comparably low in both groups.