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.

[The interaction between rocuronium and smoking. The effect of smoking on neuromuscular transmission after rocuronium]. / Die Wechselwirkung von Rocuronium und Rauchen. Der Einfluss des Rauchens auf die neuromuskuläre Ubertragung nach Rocuronium.

UNLABELLED: Recent studies have shown different results concerning the effects of smoking on neuromuscular blocking agents. Some reports indicate that smokers need higher doses of vecuronium, but are more sensitive to atracurium. The aim of this study was to evaluate the effects of smoking on onset and recovery time after a single 0.6 mg/kg intubating dose of rocuronium an analog of vecuronium. METHODS: Following institutional approval and informed consent, 20 smokers (> 10 cigarettes/day) and 20 nonsmokers were included in the study. Following oxazepam premedication and induction with fentanyl and thiopental, single-twitch stimulation of the ulnar nerve was performed every 10 s. Following stabilisation of control responses, patients received rocuronium 0.6 mg/kg for intubation. Anaesthesia was maintained with enflurane < or = 0.8 vol.% (end-tidal) and 65% nitrous oxide in oxygen. Onset time and recovery to 25% and 75% of the twitch control values were recorded. RESULTS: Onset and recovery times were not different between smokers and nonsmokers. CONCLUSIONS: The results of the present study suggest that chronic nicotine exposure does not change onset time or duration of rocuronium neuromuscular blockade. A previous study found a greater need for vecuronium in smokers and discussed stimulation of the neuromuscular junction and enhanced biotransformation due to the enzyme-inducing properties of nicotine. The differences in our results could be partly due to a longer period of refraining from smoking in our patients, leading to very low nicotine blood concentrations without the proposed receptor-stimulating effect. Another cause for different behaviour of the two analogs could be different elimination pathways. Recent investigations suggest that rocuronium may not be eliminated principally by the liver. Therefore, enhanced nicotine-induced biotransformation, as suggested for vecuronium, would not occur with rocuronium.

Cocaine or phenylephrine/lignocaine for nasal fibreoptic intubation?

In order to assess if a mixture of phenylephrine/lignocaine is as effective as cocaine for local analgesia and vasoconstriction during nasal fibreoptic intubation, 99 patients receiving topical nasal analgesia either with cocaine 10% or a mixture of phenylephrine 1% and lignocaine 4% were studied in a randomized double-blind investigation. After topical analgesia a flexible fibreoptic endoscope was advanced through a nostril. Larynx, glottis and trachea were endoscopically sprayed with lignocaine. Following induction of anaesthesia a nasotracheal tube was inserted fibreoptically. Pain intensity and amount of epistaxis during endoscopy were assessed. Blood pressure, heart rate and ECG-ST segment were determined before and after topical nasal analgesia, after induction of anaesthesia and after nasotracheal intubation. There were no significant differences in pain intensity of epistaxis between groups during endoscopy, nor significant alterations in haemodynamic parameters or ST-segment. It is concluded that the mixture of phenylephrine and lignocaine is a useful alternative to cocaine for local analgesia and vasoconstriction during nasal fibreoptic intubation.

[The effects of cimetidine on the pharmacodynamics of rocuronium]. / Beeinflussung der Pharmakodynamik von Rocuronium durch Cimetidin.

UNLABELLED: Cimetidine is a commonly used H2-receptor antagonist that has been recommended for the prevention of acid aspiration syndrome and has been shown to potentiate vecuronium-induced neuromuscular block. The present study was designed to investigate the influence of a single IV dose of cimetidine on the neuromuscular effects of rocuronium, an analogue of vecuronium with a short onset time. METHODS: Twenty adults aged 18-65 years were included in the study with their informed consent and approval of the Ethics Committee. Following oxazepam premedication, 10 patients were randomly allocated to receive cimetidine 400 mg IV 30 min before anaesthesia. After fentanyl and thiopentone induction, single-twitch stimulation of the ulnar nerve was performed every 10 s. Following stabilisation of control responses, patients received rocuronium 0.6 mg/kg for intubation. Anaesthesia was maintained with enflurane < or = 0.8 vol.% (end-tidal) and 65% nitrous oxide. Onset time and recovery times to 25% and 75% of the twitch control values were recorded. RESULTS: Onset and recovery times did not differ between groups. CONCLUSIONS: The results of the present study demonstrate that cimetidine does not increase the duration of rocuronium neuromuscular blockade. Inhibition of the cytochrome P450 system or a direct effect at the neuromuscular junction have been suggested as the mechanisms of drug interaction associated with cimetidine. Impairment of hepatic microsomal drug metabolism results in a prolonged duration of action of vecuronium, which appears to be eliminated primarily via the liver. Data on the elimination pathway of rocuronium in humans are not available. The fact that cimetidine does not alter the recovery from rocuronium-induced neuromuscular block confirms a previous suggestion that rocuronium may not be eliminated principally by the liver. A direct effect of cimetidine on the neuromuscular junction could not be confirmed by this study. Therefore, cimetidine can be given as premedication without a risk of prolonged rocuronium block.

[Intubation requirements after rocuronium and succinylcholine]. / Intubationsbedingungen nach Rocuronium und Succinylcholin.

OBJECTIVE: Rocuronium is a new non-depolarising steroidal muscle relaxant with a short onset time. The present study was undertaken to compare intubating conditions as well as onset and clinical duration of a single dose of 0.6 mg/kg (2 x ED95) with a single dose of 1 mg/kg suxamethonium (3 x ED95). METHODS: After obtaining informed consent and approval of the Ethics Committee, 40 adult patients (ASA I-III) participated in this study. After premedication with oxazepam, anaesthesia was induced with fentanyl and propofol and maintained with propofol, N2O and supplements of fentanyl as needed. Muscular relaxation was assessed by EMG recording of adductor pollicis muscle after supramaximal single twitch stimulation of the ulnar nerve every 10 s. Patients were allocated randomly to receive either rocuronium 0.6 mg/kg or suxamethonium 1 mg/kg. The following parameters were measured: intubating conditions 60 s after injection, onset time and clinical duration of neuromuscular block, % block at intubation, heart rate, blood pressure and arterial oxygen saturation. RESULTS: (mean +/- SD). Intubating conditions after rocuronium and suxamethonium were found to be clinically acceptable (excellent or good) in 90% of patients, though there was only a partial blockade of the adductor pollicis muscle with rocuronium (71 +/- 23%) compared to suxamethonium (95 +/- 14%) (p < 0.05). The onset time and clinical duration of relaxation was shorter after suxamethonium (p < 0.05) and occurred at 0.8 +/- 0.2, 7 +/- 2.1 and 3.2 +/- 1.3, 29 +/- 11 min after suxamethonium and rocuronium respectively. CONCLUSION: At a dosage of 0.6 mg/kg, rocuronium has an onset time of about 3 min and a clinical duration of relaxation of nearly half an hour. These data are supported by various studies, while others show shorter times, probably due to different monitoring techniques. In spite of the pharmacodynamic differences between suxamethonium and rocuronium, the intubating conditions after administration of both compounds are comparable and develop at the same rate.

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.

[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.

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.

[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.

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.

[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).

[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)

[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.

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.

[A universally applicable mask attachment for fiberoptic intubation. The Mainz Universal Adapter]. / Universell verwendbares Maskenansatzstück für die fiberoptische Intubation. "Mainzer-Universaladapter".

The problems associated with "difficult airways" have almost subsided since the introduction of flexible fiberoptic bronchoscopes for tracheal intubation. Limitations of this technique persist with uncooperative patients, children and infants. We describe an universally applicable connector for fiberoptic intubation during mask ventilation, which fits all masks with a 22-mm connector, including the Rendell-Baker-Soucek type. This technique is of utmost value when a "difficult airway" is encountered only subsequent to induction of anesthesia, especially if nondepolarizing muscle relaxants have been administered. The device makes intubation possible with all sizes of fiberoptic bronchoscopes. The prerequisites for application of this technique include an airway that will be maintained by mask ventilation.