Heated breathing tubes affect humidity output of circle absorber systems.

STUDY OBJECTIVE: To verify whether the airway climate in circle systems can be improved with heated breathing tubes. DESIGN: Randomized, controlled, prospective clinical study. SETTING: Operating theater of the Department of Maxillofacial Surgery. PATIENTS: 26 adult patients undergoing prolonged anesthesia. INTERVENTIONS: A total of 26 prolonged anesthetics were conducted in adult patients using a minimal fresh gas flow rate (0.6 L/min) and silicon breathing tubes (16 mm internal diameter) containing a heated coil. Group 1 (n = 10 patients) was the control group; breathing tubes were unheated. In Group 2 (n = 10 patients), breathing tubes were heated to 30 degrees C. In Group 3 (n = 6 patients), breathing tubes were heated to 36 degrees C. MEASUREMENTS AND MAIN RESULTS: Humidity and temperature were measured at the Y-piece. Inspiratory temperature on Group 2 was significantly higher than in Group 1. In Group 3, both inspiratory temperature and absolute humidity were significantly higher than in Group 1. After 5 minutes of ventilation, water content and temperature of inspiratory gases were significantly higher in Group 3 than in Group 1. CONCLUSION: Low-flow systems need at least 120 minutes to achieve a satisfactory airway climate. Heated breathing tubes effectively reduce this delay.

Development of a HPLC-system for quantitative measurement of lidocaine and bupivacaine in patients plasma during postoperative epidural pain therapy.

A HPLC method was developed for the simultaneous quantitative analysis of lidocaine and bupivacaine in plasma, with bupivacaine serving as the internal standard for the assessment of lidocaine and vice versa. The samples are prepared by diethyl ether-extraction of the alkalified plasma and re-extraction using diluted sulphuric acid. This allows the elimination of interfering medication and plasma proteins. The prepared samples are chromatographed with a Merck LiChroCART Superspher 60 RP-select B cartridge column, the local anesthetics are detected using UV-photometry and the concentration is calculated by comparing the peak areas of the analyzed substance and the internal standard. Using a sample volume of 1 ml plasma, concentrations of approximately 2.5 micrograms/ml and 1 microgram/ml can be analyzed with a 95%-confidence interval of 2.5% or 5%, respectively. At higher or lower concentrations, accurate results can be obtained using smaller or larger plasma samples. The evolved analytical method allows the rapid and simple determination of lidocaine and bupivacaine plasma levels at a wide range of concentrations. It is suitable for research purposes as well as for routine analyses.

The climatisation of anesthetic gases under conditions of high flow to low flow.

The aim of climatisation of anesthetic gases in prolonged anesthesia is to maintain tracheobronchial climate comparable to that of spontaneous nasal breathing. The humidity and temperature of inspired gases attained in the circle system at a fresh gas flow of 6.0, 3.0 and 1.5 l/min are inadequate for prolonged anesthesia. According to the results of our study with the scanning electron microscope, the minimal flow technique (0.5 l/min) leads to major improvement of heat (28 to 32 degrees C) and moisture (20 to 27 mg H2O/l) conditions of anesthetic gases in anesthesia systems.

Malignant hyperthermia susceptibility--successful management with a "stressfree" technique.

The pathogenesis of the malignant hyperthermia syndrome is not yet completely understood. There is evidence of involvement of the sympathoadrenergic system. We describe the anesthetic management of two patients considered to be MH-susceptible. Management in the theater included an infusion of dantrolene 2.5 mg/kg prior to induction of anesthesia. In addition, the first patient was given a peroral prophylaxis with dantrolene; in subsequent cases this route of administration was abandoned. Anesthesia was performed with a drug combination devoid of sympathomimetic effects (diazepam, flunitrazepam, midazolam,--methohexital,--fentanyl, alfentanil,--vecuronium). Monitoring should include ECG, blood pressure, body temperature and end-tidal CO2-concentration.

[Improved climatization of anesthetic gases by modifying the Sulla 808 V anesthesia equipment]. / Verbesserung der Klimatisierung anästhetischer Gase durch Umrüstung des Narkosegerätes Sulla 808 V.

Maintenance of a physiological airway climate is one of the goals of anaesthesia ventilation. This may be achieved by integration of heat and moisture exchangers (HME's) or--more economically--by reducing fresh gas flow rate down to the minimal-flow-range. Conventional bag-in-bottle ventilators with hanging bellows do not allow operation with minimal-flow-rates; flow reduction results sooner or later in a positive-negative-pressure ventilation pattern; especially so in patients suffering from COPD. This problem may be overcome by uncoupling fresh gas flow from tidal volume by means of integrating a reservoir bag and a special valve system to the circle system. This technique was hitherto restricted to high class anaesthetic workstations; since recently it became available as an update modification for the Sulla 808 VTM anaesthesia machine (Dräger, Lübeck). With a setting previously described the effect of this modification on airway climate was investigated in a prospective, randomized clinical study. Twenty-four consenting patients were randomly assigned to be ventilated with either high (6.0 L/min, n = 12) or minimal (0.6 L/min, n = 12) fresh gas flow rate. The time course of inspiratory temperature and humidity was measured over a period of 120 minutes; water content was calculated from relative humidity and temperature. In the minimal-flow-group, already after 60 minutes a temperature of 28.6 +/- 0.9 degrees C and a water content of 17.6 +/- 1.9 mg H2O/L were achieved (mean +/- SD).(ABSTRACT TRUNCATED AT 250 WORDS)

Humidity of anaesthetic gases with respect to low flow anaesthesia.

It has been demonstrated in an experimental study in swine using the scanning electron microscope that a rebreathing technique utilising minimal fresh gas flowrates significantly improves climatization of anaesthetic gases. Consequently, effects of various anaesthetic techniques on airway climate must be assessed, which covers the need for suitable measuring devices. Basic principles and methods of humidity measurement in flowing anaesthetic gases include gravimetric hygrometry, dew point hygrometry, wet-dry bulb psychrometry, mass spectrometry, spectroscopic hygrometry and electrical hygrometry. A custom-made apparatus for continuous measurement of humidity and temperature in the inspired and expired gas mixtures of a breathing circuit (separated by a valve system, integrated between the endotracheal tube and the Y-piece) is described. Comparative evaluation of this apparatus and the psychrometer was carried out. It could be demonstrated that the apparatus, measuring with capacitive humidity sensors, is more suitable for prolonged use under clinical conditions than the psychrometer. In the second part of the study, climatization of anaesthetic gases under clinical conditions was investigated using fresh gas flowrates of 0.6, 1.5, 3.0 and 6.0 l/min. In the inspiratory limb of the circuit an absolute humidity of 21.3 mg H2O/l and a temperature of 31.5 degrees C were obtained after 120 minutes of minimal flow. Humidity and temperature of inspired air obtained with fresh gas flowrates of 6.0 and 3.0 l/min were found to be inadequate for prolonged anaesthesia. Reducing the fresh gas flow to 1.5 l/min increases heat and moisture content in the respired gases, but conditions are still inadequate for prolonged anaesthesia. Sufficient moisture (> or 20 mg H2O/l) and temperature are obtained under minimal flow conditions after one hour.

[Free fatty acids as an indicator of preoperative stress and effects of premedication with flunitrazepam, morphine and promethazine on blood fatty acid level]. / Freie Fettsäuren als Indikator für präoperativen Stress sowie der Einfluss einer Prämedikation mit Flunitrazepam, Morphium und Promethazin auf den Fettsäurespiegel im Plasma.

We investigated the influence of different oral premedication given to 50 male and 50 female patients on the plasmaconcentration of free fatty acids (FFA) as an indicator of preoperative stress and compared them with patients given no premedication at all. FFA are measured with a gaschromatographic method. FFA were measured four times: Time 1 (t1): the first day in hospital, t2: After the anesthesiologist's visit, t3: In the morning of the operation, t4: Before starting anesthesia. The groups are: I. 20 male and 20 female patients without any premedication; II. every 10 patients of both sexes given 2 mg Flunitrazepam (p.o.) on the preoperative night; III. every 10 patients given Morphium (0.15 mg i.m.) and Promethazin (50 mg i.m.) and, last, IV. every 10 patients getting the same premedication as group II and IV. 98 patients had a significant decrease of FFA from t1 to t2. The FFA of all increased from t2 to t3. Moreover, there was an increase from t3 to t4. We conclude from this that no premedication we had investigated is able to lower the physiological and biochemical stress-response as far as shown by FFA. Apart from myristic-acid, there was no difference in the groups. However, with no statistic significance, both 'Flunitrazepam-groups' showed the lowest increase. Further, in 28 from 32 cases, females had a higher FFA-level than males (in 16 cases with statistical significance).

[Optimized analgesic sedation. Improved possibilities in high-risk patients through the use of pulse oximetry]. / Optimierte Analgosedierung. Verbesserte Möglichkeiten bei Risikopatienten durch Anwendung der Pulsoximetrie.

The pulse oximeter allows quick assessment of a patient's respiratory function and the early detection of imminent hypoxia (Singer and Thomas, 1988). It is a useful means in non-continuous circulatory monitoring and is not stressful to the patient. In analgosedation it enables the operator to monitor the respiratory effect of the drugs used with almost no delay, to take the counter-measures required and to adapt the dosage to the individual requirements of each patient.

[Effect of muscle relaxants on intraocular pressure]. / Zur Wirkung von Muskelrelaxantien auf den intraokularen Druck.

Since general anesthesia is being used increasingly in ophthalmic surgery, the effects of anesthetic drugs on intraocular pressure (IOP) have to be considered. Competitive neuromuscular blocking drugs either do not affect IOP or produce a slight decrease. Depolarizing muscle relaxants increase IOP. This effect, which is pronounced with succinylcholine, cannot be reliably prevented by any concomitant medication. The new competitive relaxants atracurium and vecuronium provide stable conditions with respect to IOP and systemic circulation, combined with fast onset and intermediate duration of action.

Intraoral conduction anesthesia with epinephrine-containing local anesthetics and arterial epinephrine plasma concentration.

Following conduction anesthesia using either lidocaine 2% with epinephrine 1:80,000, articaine 4% with epinephrine 1:100,000, or articaine 4% with epinephrine 1:200,000, the arterial plasma epinephrine concentration was measured. Eighteen healthy young patients scheduled for osteotomy of a mandibular third molar were studied. Each local anesthetic-epinephrine combination was tested in six patients. There was no significant difference in the arterial plasma epinephrine concentration after injection of 2 mL of the studied anesthetic-epinephrine combinations. The result was explained by the concentration difference in the local anesthetics. Although the vasodilating action of lidocaine and articaine is almost identical, there will be enhanced vasodilation by the doubled concentration in the case of articaine (4%) and the local resorption of epinephrine may be facilitated. There were no significant changes in the measured cardiovascular parameters.

[Intubation with the new ultra thin flexible fiberoptic scope in small children with congenital ankylosis of the temporomandibular joints]. / Intubation mit der neuen ultradünnen flexiblen Fiberoptik bei Kleinkindern mit kongenitaler Ankylose der Kiefergelenke.

Management of anaesthesia and intubation using a flexible endoscope of the ultra-thin generation (external diameter on the distal end 2.7 mm) of brother and sister with congenital ankylosis of the temporomandibular joint is described. Sedation was provided with ketamine while maintaining spontaneous breathing. Alternative methods to overcome difficult intubation in infants and small children with consideration of their specific anatomical conditions are discussed. Insertion of a fiberoptic endoscope through the endotracheal tube in the age group reported here was not possible hitherto. The new ultra-thin generation of flexible fiberscopes now makes it possible to perform direct fiberoptic intubation of infants and small children.

[The use of the laryngeal mask--a practical method?]. / Einsatz der Larynxmaske--eine praktikable Methode?

In 1985 Brain et al. published their first experience with the laryngeal mask, developed by themselves. With this mask it is possible to seal the larynx and ventilate a patient during anesthesia without endotracheal intubation. Meanwhile, further reports of successful use have been published, especially in Great Britain. We decided to investigate this new anesthetic device. In 15 patients (ASA groups I and II) undergoing elective operations in the supine position the laryngeal mask was inserted after induction of anesthesia with propofol and alfentanil (Fig. 1). Positioning of the laryngeal mask was carried out as described by Brain. In all patients the laryngeal masks could be inserted without any problems, manual ventilation of the patient was performed immediately, and ventilating pressures never exceeded 15 cm H2O. We observed neither complications related to airway control nor technical problems. Cardiovascular parameters and arterial oxygen saturations were always in the normal range (Fig. 2). In 3 patients quick movements of the head were carried out during repositioning of a fractured zygomatic arch, but no complications due to a possible changed position of the laryngeal mask occurred. Postoperatively two patients reported airway complaints such as sore throat. Our investigation confirmed the previously described advantages of the laryngeal mask. We consider its use to be especially indicated in general anesthesia for short surgical or diagnostic procedures or if specific complications of endotracheal intubation should be avoided. A critical aspect in the use of the laryngeal mask is the fact that there is no complete isolation of the trachea and, therefore, an insufflation of the stomach or aspiration could occur, especially during critical situations (e.g. bronchospasms).(ABSTRACT TRUNCATED AT 250 WORDS)

[Fiber optic orotracheal intubation]. / Fiberoptische orotracheale Intubation.

Fiberoptic intubation is widely accepted in the management of a "difficult airway". In the majority of these cases the underlying anatomical findings require a nasal approach. We report a case of fiberoptic intubation where nasal passage was not possible. Orotracheal fiberoptic intubation was easily performed using a Williams oral airway and a Patil-Syracuse face mask. We recommend this technique for those cases where fiberoptic intubation is indicated but contraindications to the transnasal route apply and an "asleep-intubation" is desired.

[Undesirable effects following the local injection of ornipressin during general anesthesia: can the risk be lessened? A prospective study]. / Unerwünschte Wirkungen nach Lokalinjektion von Ornipressin während der Allgemeinanaesthesie: Lässt sich das Risiko vermindern? Eine prospektive Studie.

Complications associated with local infiltration of ornithine-8-vasopressin (O-8-V) during general anesthesia (GA) are documented. Severe and extremely severe complications range around 20%; fatalities have been reported. The incidence of complications is associated with age, pre-existing cardiovascular or pulmorespiratory disease, and dosage administered. In a prospective study, we investigated 169 patients following a standardized protocol. Maximum dosage was 2 IU, diluted to 0.25 IU/ml in 0.9% saline. Patients with cardiovascular or respiratory disease and those below 1 or above 50 years of age were excluded. GA consisted of tracheal intubation and controlled ventilation with enflurane in N2O/O2 and intravenous fentanyl. Cardiovascular monitoring was by ECG with arrhythmia detection, plethysmography, and oscillometric - in some patients intraarterial - blood pressure measurement. Ventilatory monitoring included respiratory rate, tidal volume, inspiratory and expiratory O2 concentrations, capnometry, and end-tidal enflurane concentration. Local infiltration of the oral soft tissues with O-8-V was performed after a steady-state of anesthesia was achieved and 20 min before commencement of surgery. No severe or extremely severe complications or arrhythmias were observed. A moderate increase in blood pressure was seen in 43% of patients; in 10% this increase was 30-70 mmHg (systolic and/or diastolic). For data analysis, patients were allocated to 4 groups according to the dosage of O-8-V administered. Systolic and diastolic pressures increased to above control in all groups; however, no inter-group differences were found for blood pressure or heart rate. It is concluded that the risks associated with local infiltration of soft tissues with O-8-V during GA can be attenuated by a protocol such as the one established for this prospective study.(ABSTRACT TRUNCATED AT 250 WORDS)

[An activated charcoal filter for eliminating volatile anesthetics. A contribution to the management of malignant hyperthermia]. / Aktivkohlefilter zur Eliminierung volatiler Anaesthetika. Ein Beitrag zum Management der malignen Hyperthermie.

Anesthesia machines may not be contaminated with anesthetic vapors when a patient susceptible to malignant hyperthermia (MHS) is to be anesthetized. A clean machine may not always be available, and recommended protocols for preparing a contaminated machine are cumbersome and time-consuming. We suggest the use of an activated charcoal filter that is easily assembled from spare parts available in many anesthesiology departments (Fig. 2). It consists of an HME container (Servo-Humidifier 150, Siemens-Elema), a sieve set from an anesthesia circuit (7a/8-ISO, Dräger, Lübeck), and grained activated charcoal (2.5 mm, Merck, Darmstadt). All parts are autoclavable. The filter adsorbs anesthetic vapors quantitatively (Fig. 3) without affecting humidity, nitrous oxide concentration, or circuit resistance. Storage of such a filter may obviate the need to keep a clean anesthesia machine available for MHS patients.

[Fiberoptic intubation and stress]. / Fiberoptische Intubation und Stress.

Nasotracheal intubation of the trachea by means of fiberoptic endoscopy is an accepted approach to difficult airways. The associated avoidance of direct laryngoscopy may affect the stress response to nasotracheal intubation. We tested this hypothesis by means of a prospective, randomized, controlled clinical study. METHODS. Informed consent was obtained from 30 patients presenting for maxillofacial surgery for participation in this study. Patients were allocated to three groups: nasotracheal intubation to be performed either fiberendoscopically (group 1) or laryngoscopically, with (group 2) or without (group 3) topical anaesthesia of the larynx. Haemodynamic variables (arterial blood pressure and heart rate) and concentrations of catecholamines* in plasma (adrenaline, noradrenaline; HPLC) were documented at four (two*) time points, respectively: prior to induction of anaesthesia*, after induction, 1 min after tracheal intubation*, 5 min after tracheal intubation. Differences between time points and between groups were analysed with the chi-square test; a probability of P < 0.05 was considered statistically significant. RESULTS. With respect to age, body-weight and gender, the groups were comparable. No major hemodynamic or endocrine stress responses were observed in any group. Diastolic blood pressures were significantly lower in groups one and two, one minute after tracheal intubation. DISCUSSION. Nasotracheal intubation does not provoke a major stress response, when performed in accordance with the protocol of this study. However, topical anaesthesia of the larynx, as well as the fiberendoscopic approach proved superior to control with respect to diastolic arterial pressure. We conclude that fiberoptic nasotracheal intubation, or laryngoscopy preceded by topical anaesthesia of the larynx may be useful in patients for whom an increase in rate pressure product would be undesirable.

[Preoperative increase in the plasma concentration of free fatty acids during minor elective interventions using a conventional anesthesia technic with enflurane]. / Präoperativer Anstieg der Plasmakonzentration freier Fettsäuren bei kleineren Wahleingriffen und konventioneller Narkosetechnik mit Enfluran.

Plasma concentrations of free fatty acids (FFApl) can be used as a parameter to measure stress. The present study aimed to evaluate the changes in the concentration of FFA during perioperative stress caused by minor elective surgery under a standard anaesthetic technique using enflurane. The premedication administered included heptabarbital on the preoperative night and morphine with promethazine prior to the transfer of the patient to the theatre. Blood samples for the analysis of FFA were obtained from 12 patients at the following times: 1 day preoperatively (control, c), prior to induction of anaesthesia (s1), following the administration of thiopentone (s2), following tracheal intubation (s3), 10 min after the commencement of enflurane administration (s4), following surgical incision (s5), intraoperatively (s6), following extubation (s7), 1 h after extubation (s8), and on the 1st postoperative day (s9). FFA were extracted from plasma with hexane and analysed in duplicate by a specific and sensitive gas-chromatographic assay with flame ionisation detection using pentadecanoic acid as the internal standard. All FFApl from the preoperative day (c) were within normal range. FFA concentrations at s1, s2, s3 and (to a lesser extent) at s4 were statistically significantly increased compared to control values. The maximum concentration of FFA in plasma occurred at s2. A decrease from this maximum was found in samples s4, s5 and s6 (the latter was the minimum intraoperative FFApl). The FFApl levels at s7, s8 and s9 were similar to control. A different response was found for each individual free fatty acid. The maximum increase ranged from 40% (stearic acid) to 300% (oleic acid).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of normobaric oxygen on ciliary beat frequency of human respiratory epithelium.

Respiratory infection is a major cause of morbidity after general anaesthesia. Impairment of respiratory ciliary beat frequency (CBF) by different stress factors causes a decrease in mucus transport rate (MTR). We have tested the effect of different concentrations of oxygen on CBF of human respiratory epithelium in a prospective, randomized, in vitro study. Samples of superficial mucosa of the inferior nasal turbinates of 20 non-smoking healthy volunteers were harvested and exposed to three different oxygen environments (group I = 21% oxygen, group II = 60% oxygen and group III = 95% oxygen) for 2 h. In 50% of the samples, exposure time was prolonged. At 30, 60, 90, 120 and 240 min, light microscopic images of cilia activity were videotaped and CBF was later assessed in slow motion. Compared with baseline, group I showed no difference in CBF throughout the study. CBF was increased in group II from mean 9.7 (SD 0.4) to 11.2 (0.4) Hz (16%, P < 0.001) and in group III from 9.5 (0.6) to 12.1 (0.5) Hz (28%, P < 0.001) at 120 min. After 240 min of exposure to 95% oxygen, the CBF trend in group III was reduced to 11.8 (0.6) Hz but still remained above baseline. We conclude that oxygen appeared to have a dose- and time-dependent accelerating effect on CBF. Prolonged exposure to high oxygen concentrations reversed this trend. Direct oxygen toxicity ("oxygen stress") is a possible explanation for this effect. These changes may result in impaired MTR.

[Plasma concentrations of bupivacaine for continuous peridural anesthesia in children]. / Plasmakonzentrationen von Bupivacain bei kontinuierlicher Periduralanästhesie im Kindesalter.

Epidural anaesthesia is extremely useful in providing postoperative analgesia for children after surgery of the lower body. Although results on early pharmacokinetics in children have previously been reported, no data are available on the long-term effects of epidural anaesthesia. The aim of this investigation was the assessment of plasma bupivacaine levels in children with continuous epidural anaesthesia in the postoperative period. A catheter with an outer diameter of 0.63 mm was inserted through a 19G Tuohy cannula into the epidural space. A maximum dose of 0.4 mg/kg/h bupivacaine was administered for continuous epidural infusion. Careful monitoring was performed to detect early signs of local anaesthetic intoxication. Two milliliters of blood were obtained in each patient per day and nepholometric serum measurement were performed to determine alpha 1-acid glycoprotein and albumin levels. Bupivacaine plasma concentrations were assessed according to the method described by Sattler et al. [25]. Ten children were included in the investigation. The measured albumin and alpha 1-acid glycoprotein concentrations were within the range described by other investigators. At the onset of pain therapy maximum levels of 0.5 microgram/ml were recorded after a loading dose of bupivacaine and levels of up to 2.2 micrograms/ml were achieved following continuous infusion. There were no neurologic complications or signs of local anesthetic intoxication. In conclusion our results show that a dose of up to 0.4 mg/kg/h bupivacaine during continuous epidural infusion is not associated with toxic complications. Careful monitoring of the children by experienced staff is mandatory.