Predictors for postoperative nausea and vomiting after xenon-based anaesthesia.

BACKGROUND: In contrast to volatile anaesthetics, xenon acts by antagonism at N-methyl-d-aspartate receptors and antagonizes 5-hydroxytryptamine type 3 receptors that mediate nausea and vomiting. Therefore, it is unknown whether the same risk factors for postoperative nausea and vomiting (PONV) after volatile anaesthetics apply to xenon-based anaesthesia. METHODS: With ethics committee approval and written informed consent, 502 consecutive patients undergoing xenon-based anaesthesia were included in a multicentre prospective observational study. Antiemetic prophylaxis was administered at the discretion of the attending anaesthetists. Postoperative nausea and vomiting and need for antiemetic rescue medication were assessed for 24 h after anaesthesia. Multivariate logistic regression analysis was performed to quantify risk factors for PONV and need for rescue medication. RESULTS: Four hundred and eighty-eight subjects were available for the final analysis. The incidence of PONV in subjects without prophylaxis was lower than expected according to the Apfel Score (28% observed; 42% expected, P<0.001). Independent predictors for PONV were (adjusted odds ratio; 95% confidence interval) female sex (1.76; 1.08-2.89), younger patient age (0.82 per 10 yr; 0.69-0.97), and longer duration of anaesthesia (1.36 per hour; 1.17-1.59). CONCLUSIONS: The incidence of PONV was significantly lower than predicted by the Apfel Score. Female sex, younger age, and longer duration of anaesthesia are risk factors for PONV after xenon-based anaesthesia. CLINICAL TRIAL REGISTRATION: German Federal Institute for Drugs and Medical Devices number AL-PMS-01/07GER.

M-Entropy guidance vs standard practice during propofol-remifentanil anaesthesia: a randomised controlled trial.

Seventy-two patients undergoing routine surgical procedures under propofol-remifentanil anaesthesia were randomly assigned to receive either standard clinical practice (n = 35) or standard practice plus monitoring of depth of anaesthesia with M-Entropy (n = 37). Patients in the standard practice group received more propofol than the entropy group (mean (SD) 95 (14) vs 81 (22) microg.kg(-1).min(-1), respectively; p < 0.01), and less remifentanil (0.39 (0.08) vs 0.46 (0.08) microg.kg(-1).min(-1), respectively; p < 0.001). Loss of consciousness was best predicted by BIS (prediction probability (P(K)) 0.96) and response entropy (P(K) 0.93), whereas emergence was best predicted by response entropy (P(K) 0.94). The frequency of unwanted patient responses was higher in the standard practice group than in the entropy group (47 vs 27 total events, respectively; p < 0.01). Both regimens resulted in fast recovery with no clinical advantage for either one. There were no significant differences in haemodynamic parameters, postoperative nausea and vomiting or satisfaction with the procedure.

Effects of the 5-HT2 receptor antagonist ritanserin on halothane-induced increase of inositol phosphates in porcine malignant hyperthermia.

Recent studies have shown a significant increase of inositol phosphates (IPs) in skeletal muscle during episodes of halothane-induced malignant hyperthermia (MH) in pigs. After treatment with dantrolene and disappearance of MH crisis the IP concentrations returned to basal levels. In order to examine if the increase of IPs during halothane-induced MH may be related to an enhanced IP synthesis in response to activation of 5-HT2 (5-hydroxytryptamine) receptors, the effects of ritanserin, a selective 5-HT2 receptor antagonist, on IP levels were investigated. Biopsies of skeletal muscle of the hindlimbs were obtained in random order and IPs were determined in homozygous MH-susceptible (MHS) and MH-non-susceptible (MHN) swine in the following order: (1) basal, (2) after treatment with ritanserin (2.0 mg/kg), (3) after halothane challenge (3 vol% for 20 min). Basal concentrations of all IPs were higher in MHS than in MHN swine. Ritanserin did not cause any significant changes of IP levels compared to the basal concentrations in MHS and MHN pigs. In MHS pigs, ritanserin did not prevent a halothane-induced MH-crisis. After halothane challenge, 1,3,4-IP3, 1,3,4,6-IP4 and 1,3,4,5-IP4 levels were increased in MHS (during MH crisis) vs. basal concentrations, whereas no changes were found in MHN pigs. Since the increases of IP levels in MHS pigs during MH crisis found in the present study were comparable to those without pretreatment with ritanserin, shown by recent studies, it may be concluded that ritanserin does not prevent the increase of IPs during a halothane-induced MH. Thus, the present data indicate that increases of IP levels during halothane-induced MH in swine are due to other mechanisms than 5-HT mediated enhancement of IP synthesis.

Inhibition of nitric oxide metabolism enhances the hypnotic-anesthetic action of the alpha2-adrenoceptor agonist dexmedetomidine in vivo.

Nitric oxide (NO) synthase inhibitors have been demonstrated to increase the anesthetic action of volatile and intravenous anesthetics. This study was designed to test the hypothesis that, comparable to other general anesthetics, the hypnotic-anesthetic action of dexmedetomidine is increased after administration of the NO synthase inhibitor nitro-L-arginine methyl ester (L-NAME). With approval of the local animal care committee, the anesthetic potency of dexmedetomidine or a combination of dexmedetomidine plus 1 mM L-NAME was determined in Xenopus laevis larvae. Anesthesia was defined as loss of righting reflex. Concentration-response curves were calculated by a logistic approach. Additional experiments were performed that exposed the animals to dexmedetomidine in the presence of L-NAME plus L-arginine, as well as D-NAME. In the dexmedetomidine and the dexmedetomidine plus L-NAME groups, the fraction of anesthetized animals increased with increasing concentrations of dexmedetomidine. Calculation of the half-maximal effective concentration (EC50) resulted in a value of 7.8+/-0.6 microM for dexmedetomidine and 3.8+/-0.2 microM for dexmedetomidine plus L-NAME (p<0.05). Addition of L-arginine reversed the potentiating effect of L-NAME. Administration of D-NAME did not affect the EC50 of dexmedetomidine. In a manner comparable to that of other general anesthetics, the anesthetic effect of dexmedetomidine was increased by about 51% by an acute inhibition of the NO metabolism. Together with recent findings that alpha2-adrenoceptor agonists decrease the NO mediated synthesis of cGMP similar to volatile and intravenous anesthetics, the results suggest that the NO/cGMP pathway is an important mediator of the anesthetic action of these compounds.

Comparison of LMA Unique, Ambu laryngeal mask and Soft Seal laryngeal mask during routine surgical procedures.

BACKGROUND AND OBJECTIVE: This study was performed to compare three disposable airway devices, the LMA Unique (LMA-U), the Ambu laryngeal mask (Ambu LM) and the Soft Seal laryngeal mask (Soft Seal LM) for elective general anaesthesia during controlled ventilation in non-paralysed patients. METHODS: One hundred and twenty ASA I-III patients scheduled for routine minor obstetric surgery were randomly allocated to the LMA-U (n = 40), Ambu LM (n = 40) or Soft Seal LM (n = 40) groups, respectively. Patients were comparable with respect to weight and airway characteristics. A size 4 LMA was used in all patients and inserted by a single experienced anaesthesiologist. Oxygenation, overall success rate, insertion time, cuff pressure and resulting airway leak pressure were determined as well as a subjective assessment of handling and the incidence of sore throat, dysphagia and hoarseness. RESULTS: Time of insertion was shortest with the Ambu LM, while failure rates were comparable with the LMA-U, the Ambu LM and the Soft Seal LM (median 19 s; range 8-57 s; success rate 100% vs. 14; 8-35; 97% vs. 20; 12-46; 95%). Insertion was judged 'excellent' in 75% of patients in the LMA-U group, in 70% of patients in Ambu LM group and in 65% of patients in the Soft Seal LM group. There was no difference between devices with respect to postoperative airway morbidity at 6 h or 24 h following surgery. CONCLUSIONS: All three disposable devices were clinically suitable with respect to insertion times, success rates, oxygenation, airway and leak pressures, as well as to subjective handling and postoperative airway morbidity.

Classic electroencephalographic parameters: median frequency, spectral edge frequency etc.

Even today many anaesthesiologists rely on parameters of the autonomic nervous system, such as blood pressure and heart rate to decide if a patient is adequately anaesthetized. It is thought that the electroencephalogram (EEG) may provide more information on the state of anaesthesia. Because full EEG analysis is not possible in the operating room, processed EEG parameters have been developed comprising complex information into a single value. Time and frequency domain parameters are calculated. The power spectrum results from a Fourier analysis and can be described by parameters such as median frequency, spectral edge frequency and others. It was noted, however, that anaesthetics at low doses increase frequency of the EEG, whereas at high doses the EEG is depressed. This biphasic response makes it difficult to clearly distinguish the exact anaesthetic state of a patient. Median frequency and spectral edge frequency have been studied in numerous studies. However, no sole indicator has been derived from the EEG that could serve as a descriptor of anaesthetic depth.

Propofol/remifentanil vs sevoflurane/remifentanil for long lasting surgical procedures: a randomised controlled trial.

We compared the haemodynamics, emergence and recovery characteristics of total intravenous anaesthesia using propofol/remifentanil with sevoflurane/remifentanil anaesthesia, under bispectral index guidance, in 103 patients undergoing surgical procedures lasting > 3.5 h. Time to tracheal extubation was significantly shorter in the propofol group than in the sevoflurane group (mean (SD) 8.3 (3.5) min vs 10.8 (4.6) min, respectively; p = 0.0024), but further recovery was comparable in both groups. There were no significant differences in haemodynamic parameters, intensity of pain or postoperative nausea and vomiting. During and after anaesthesia of comparable depth for long lasting surgical procedures, both propofol/remifentanil and sevoflurane/remifentanil enable haemodynamic stability and fast emergence. The shorter time to extubation in the propofol group does not offer a relevant clinical advantage.

Monitoring of cerebral oxygenation with near infrared spectroscopy and tissue oxygen partial pressure during cardiopulmonary resuscitation in pigs.

BACKGROUND AND OBJECTIVE: The present study was designed to compare cerebral oxygenation measured with near infrared spectroscopy and local brain tissue oxygen partial pressure, respectively, in pigs during cardiopulmonary resuscitation. Since tissue overlying the brain may have an impact on near infrared spectroscopy readings, we tested whether optode placement on intact skin or on the skull yielded comparable results. METHODS: Twelve healthy pigs were anaesthetized and subjected to continuous haemodynamic, near infrared spectroscopy and brain tissue oxygen partial pressure monitoring. After 4 min of untreated ventricular fibrillation, cardiopulmonary resuscitation was started and arginine vasopressin was administered repeatedly three times. Near infrared spectroscopy values recorded were both the tissue oxygenation index and the tissue haemoglobin index as well as relative changes of chromophores (haemoglobin and cytochrome oxidase). Four animals served as control and were measured with both near infrared spectroscopy optodes mounted on the intact skin of the forehead, while in the remaining eight animals, one near infrared spectroscopy optode was implanted directly on the skull. RESULTS: Near infrared spectroscopy readings at the skin or at the skull differed consistently throughout the study period. After arginine vasopressin administration, near infrared spectroscopy values at the different locations showed a transient dissociation. In contrast to near infrared spectroscopy measured on intact skin, near infrared spectroscopy readings obtained from skull showed a significant correlation to brain tissue oxygen partial pressure values (r = 0.67, P < 0.001). CONCLUSION: Near infrared spectroscopy readings obtained from skin and skull differed largely after vasopressor administration. Near infrared spectroscopy optode placement therefore may have an important influence on the tissue region investigated.

The influence of xenon on regulation of the autonomic nervous system in patients at high risk of perioperative cardiac complications.

BACKGROUND: As xenon anaesthesia (XE) does not produce haemodynamic depression its use may be of benefit in patients at high risk of intraoperative haemodynamic instability and perioperative cardiac complications. XE (n=22) was compared with total i.v. anaesthesia (TIVA, n=22) for differences in autonomic regulation, peri- and postoperative performance. METHODS: Patients undergoing abdominal aortic surgery were studied at five events: T1: baseline awake; T2: anaesthesia induction; T3: before aortic cross-clamping; T4: after aortic cross-clamping; T5: after aortic declamping. T3-T5: end-tidal xenon concentration 60 (5)%. Intraoperative analysis: heart rate, heart rate variability, blood pressure and cardiac output. Postoperative analysis: 24 h Holter ECG, intensive care unit and hospital stay, and patient's outcome after 6 months. RESULTS: XE in contrast to TIVA increased parasympathetic and decreased sympathetic activity. Median low to high frequency decreased significantly in the XE group after start of XE (P<0.05) and remained significantly lower during all events after start of XE as compared with TIVA (P=0.0001). After start of XE heart rate of these patients was significantly lower as compared with TIVA (P=0.04). Cardiac output increased significantly in TIVA after aortic declamping (P<0.05). Outcome parameters did not differ significantly between groups. CONCLUSIONS: XE patients demonstrated lower sympathetic and higher parasympathetic activity as compared with TIVA patients. This was reflected by significant differences in haemodynamics but did not correlate with a better postoperative outcome. Thus, it remains controversial whether XE provides benefits in high risk patients.

Balanced anaesthesia today.

An 'ideal' anaesthetic can be approached by using a combination of different compounds. A variety of anaesthetic techniques has been described to ensure safe administration and an early recovery with high patient satisfaction. In particular, the inhalational anaesthetics desflurane and sevoflurane, with their rapid pharmacokinetics, re-established the notion of balanced anaesthesia as an equivalent, well-controllable technique. With the choice of anaesthetics and anaesthetic adjuvants clinically available today, especially the combination of a volatile anaesthetic with a short-acting opioid, balanced anaesthesia represents a big step towards an ideal anaesthetic.

Comparison of xenon-based anaesthesia compared with total intravenous anaesthesia in high risk surgical patients.

Xenon, a noble gas with anaesthetic and analgesic properties, has gained renewed interest due to its favourable physical properties which allow a rapid emergence from anaesthesia. However, high costs limit its use to a subset of patients who may benefit from xenon, thereby offsetting its costs. To date, there are only limited data available on the performance of xenon in high risk patients. We studied 39 patients with ASA physical status III undergoing aortic surgery. The patients were randomly assigned to either a xenon (Xe, n = 20) or a TIVA (T, n = 19) group. Global cardiac performance and myocardial contractility were assessed using transoesophageal echocardiography, and myocardial cell damage with troponin T and CK-MB. Echocardiographic measurements were made prior to xenon administration, following xenon administration, and after clamping of the abdominal aorta, after declamping and at corresponding time points in the TIVA group. Laboratory values were determined repeatedly for up to 72 h. Data were analysed using two-way anova factoring for time and anaesthetic agent or with ancova comparing linear regression lines. No significant differences were found in global myocardial performance, myocardial contractility or laboratory values at any time during the study period. Mean (SEM) duration of stay on the ICU (xenon: 38 +/- 46 vs. TIVA 25 +/- 15 h) or in hospital (xenon: 14 +/- 12 vs. TIVA 10 +/- 6 days) did not differ significantly between the groups. Although xenon has previously been shown to exert superior haemodynamic stability, we were unable to demonstrate an advantage of xenon-based anaesthesia compared to TIVA in high risk surgical patients.

Pseudocholinesterase activity increases and heart rate variability decreases with preoperative anxiety.

BACKGROUND AND OBJECTIVE: The objective of this study was to determine the influence of preoperative anxiety on the activity of plasma cholinesterase and heart rate (HR) variability. METHODS: A total of 50 subjects were studied, 25 male patients one day preoperatively and 25 male volunteers without surgical intervention as a control group. Blood samples were taken to determine plasma cholinesterase activity. HR variability was recorded for a period of 256 beat-to-beat intervals and analysed by frequency domain analysis into very low frequency (VLF: 0.02-0.04 Hz), low frequency (LF: 0.04-0.15 Hz) and high frequency (HF: 0.15-0.4 Hz). LF/HF ratio and total power over the 0.02-0.4 Hz range were calculated. Anxiety levels were assessed using the hospital anxiety and depression scale, the self-rating anxiety scale and a visual analogue scale. RESULTS: The patient group had significantly higher anxiety scores. Plasma cholinesterase activity was significantly higher in patients vs. controls (6646 vs. 5324 units L(-1)). Total power, LF and HF were significantly lower in the patients (1489 vs. 2581 ms2; 656 vs. 1186 ms2; 491 vs. 964 ms2, respectively). CONCLUSIONS: Preoperative anxiety increases plasma cholinesterase activity and decreases HR variability.

Arginine vasopressin reduces cerebral oxygenation and cerebral blood volume during intact circulation in swine---a near infrared spectroscopy study.

BACKGROUND AND OBJECTIVE: The aim of the present study was to investigate the impact of arginine vasopressin (AVP), a drug currently under investigation for use during cardiopulmonary resuscitation, on cerebral oxygenation and cerebral blood volume (CBV) in pigs with intact systemic circulation using near infrared spectroscopy. METHODS: Nine healthy pigs were anaesthetized and subjected to invasive haemodynamic monitoring as well as to non-invasive determination (with near infrared spectroscopy) of changes in the Tissue Oxygenation Index (TOI is the ratio of oxygenated to total tissue haemoglobin), Tissue Haemoglobin Index (THI, representing CBV) and cytochrome oxidase (deltaCytOx, representing the balance of intracellular oxygen supply). RESULTS: At both 3 and 5 min after AVP administration, TOI, THI and deltaCytOx were significantly (P < 0.001) reduced compared to baseline, while cerebral perfusion pressure increased significantly (P < 0.001). The effects of AVP on TOI and THI lasted longer than on deltaCytOx. There were no significant changes with respect to the intracranial pressure throughout the study period. CONCLUSIONS: No improvement of cerebral oxygenation was detected after AVP administration in swine with an intact systemic circulation. In contrast to recently published investigations, AVP provoked a sustained drop in indices of cerebral oxygenation and CBV.

A comparison of the proseal laryngeal mask airway, the laryngeal tube S and the oesophageal-tracheal combitube during routine surgical procedures.

BACKGROUND AND OBJECTIVE: This study was performed to compare three supraglottic airway devices: the ProSeal laryngeal mask airway (PLMA), the laryngeal tube S (LTS) and the oesophageal-tracheal combitube (OTC) during routine surgical procedures. METHODS: Ninety American Society of Anesthesiologists (ASA) I-III patients scheduled for routine minor obstetric surgery were randomly allocated to the PLMA (n = 30), the LTS (n = 30) or the OTC (n = 30) group, respectively. The overall success rate, insertion time, cuff pressures and resulting airway leak pressures were determined as well as a subjective assessment of handling and the incidence of sore throat, dysphagia and hoarseness were performed. RESULTS: Insertion time until the first adequate ventilation was significantly (P < 0.0001) shorter in the PLMA (median 29 s; 25-75th percentile 25-48 s; range 10-161 s; success rate 100%) and in the LTS group (38 s; 30-44 s; 13-180 s; 100%) compared to the OTC group (75 s; 48-98 s; 35-180 s; 90%). In vivo cuff pressures and airway leak pressures increased with the inflating cuff volume in all devices and were highest in the OTC group. Postoperatively, patients in the PLMA and the LTS group complained significantly less about sore throat (P < 0.001 and 0.05) and dysphagia (P < 0.001 and 0.02) compared to the OTC group, while there was no difference regarding the incidence of hoarseness. Subjective assessment of handling was comparable with the PLMA and the LTS, but inferior with the OTC. CONCLUSIONS: In conclusion, both PLMA and LTS proved to be suitable for routine surgical procedures and proved to be superior to the OTC which cannot be recommended for routine use.

[Unincorporated Channel Meeting (UCM)--basic research on mechanisms of anesthesia]. / Unincorporated Channel Meeting (UCM)--Grundlagenforschung über Mechanismen der Anästhesie.

Basic research on mechanisms of anesthesia in Germany has proved to be successful during the last years as demonstrated by a number of national and international publications and presentation. However, most of the groups working in this field lack a "crucial mass". In order to improve this situation the Unincorporated Channel Meeting (UCM) was introduced by Kochs and Urban in 1995. The meeting was established to provide a basis for the exchange of ideas and methods for all scientists interested in mechanisms of anaesthesia and not only anesthesiologists. Currently about ten groups are actively participating at the semi-annual meetings and the discussion group in the World Wide Web. The mini-symposium was selected from papers presented at the March 1999 meeting in Hamburg/Germany and demonstrates the wide range of topics that were discussed including patch-clamp studies and whole animal research. The publication of this mini-symposium intends to provoke thoughts about the mechanisms of anaesthesia and to create interest in the scientific approach to these problems.

Alpha2-adrenoceptor agonists in anaesthesia: a new paradigm.

Since the first report of alpha2-adrenoceptor agonists, the list of clinical indications for this class of drugs continues to expand. Alpha2-adrenoceptor agonists have several beneficial actions during the perioperative period. They exert a central sympatholytic action, thus improving haemodynamic stability in response to endotracheal intubation and surgical stress, reducing anaesthetic and opioid requirements, and causing sedation, anxiolysis and analgesia. Furthermore, alpha2-adrenoceptor agonists may offer benefits in the prophylaxis and treatment of perioperative myocardial ischaemia and their role in pain management and regional anaesthesia is increasing. The development of new, highly selective compounds which not only reduce anaesthetic requirements but induce anaesthesia by themselves may provide a new concept for the administration of anaesthesia.

Total intravenous or balanced anaesthesia in ambulatory surgery?

General anaesthesia is still the most common anaesthetic technique in the ambulatory surgery setting. With the introduction of propofol, total intravenous anaesthesia gained widespread acceptance. Recently, the combination with remifentanil, an ultra-short acting opioid analgesic, allowed even more control over the duration of the anaesthetic. In comparison to propofol, however, the new inhalational anaesthetics desflurane and sevoflurane possess a pharmacokinetic profile that is preferable to that of propofol. Initial studies show that these pharmacokinetic advantages lead to a faster short-term recovery, although both substances have been associated with a higher incidence of postoperative nausea and vomiting. No differences have so far been demonstrated in respect to long-term recovery, discharge from the post-anaesthesia care unit and discharge from the ambulatory care centre. Currently the anaesthesiologist has the possibility to choose his preferred anaesthetic technique based on individual patient needs, the surgery performed and the side-effects each technique may have. However, in contrast to the situation at the beginning of the 1990s total intravenous anaesthesia is not the technique that fits all needs but balanced anaesthesia presents an alternative.

[Possible lung embolism following embolization of a hemangioma with fibrin glue]. / Mögliche Lungenembolie nach Embolisation eines Hämangioms mit Fibrinkleber.

More than 50% of all congenital haemangiomas are located on the head and neck. Because most orofacial haemangiomas exhibit the tendency to grow rapidly, they are often treated by embolisation and excision. CASE REPORT. The case of a 5-year-old patient is presented, who was admitted to the hospital for embolisation and immediate surgery of a haemangioma of the right side of the face and upper lip. After the injection of 2 ml fibrin glue she suddenly developed hypotension, tachycardia, a low oxygen saturation, and a low end-tidal carbon dioxide partial pressure. There was no failure of the breathing circuit and no airway obstruction could be found. Most likely these symptoms were due to transport of the fibrin glue from the haemangioma into pulmonary vessels. The therapy included the administration of heparin and antihypotensive drugs. After stabilisation, the patient was transferred to the intensive care unit for 1 day without further complications. CONCLUSION. Pulmonary embolism after injection of fibrin glue into an orofacial haemangioma has not previously been reported, but it should be considered that systemic complications can occur after injecting substances for embolisation into vessel-rich tissues.