Midlatency auditory-evoked potentials, as measures of the anaesthetic state, were evaluated at similar levels of bispectral index in cardiac surgical patients maintained with either propofol or isoflurane anaesthesia.

Twenty-four patients were randomly allocated to anaesthesia with propofol (n = 12) or isoflurane (n = 12). Bispectral index was maintained below 60 during surgery. Auditory-evoked potentials were collected before induction of anaesthesia, 10 min after intubation, 30 min after sternotomy, during cardiopulmonary bypass at the time of cross-clamping of the aorta and during stable mild hypothermia, after de-clamping of the aorta, and after the operation.

At the pre-determined time points, bispectral index values showed comparable depth of hypnosis in both groups. The latency of the Nb component of midlatency auditory-evoked potentials was significantly increased in the isoflurane group after intubation (P < 0.001) and that of both the Nb and the Pa components after sternotomy (P < 0.001) compared with the propofol group. No differences between the groups were detected with respect to haemodynamic variables. No patient reported recall of intraoperative events.

After intubation and surgical stimulation, when bispectral index was at a constant level, there was a difference in the Nb and Pa components of the midlatency auditory-evoked potentials between the two anaesthetic regimens, indicating a distinction in the state of anaesthesia. Our results suggest that the parallel use of these two electrophysiological methods can show differences in the components of anaesthesia between various anaesthesia methods in cardiac surgical patients.

Although a considerable amount of promising experimental research has been performed on cardiopulmonary resuscitation, clinical data indicate an ongoing limited outcome in human beings. One reason for this discrepancy could be that experimental studies use healthy animals whereas most human beings undergoing cardiopulmonary resuscitation suffer from acute or chronic myocardial dysfunction. To overcome this problem, we sought to develop a new model of myocardial infarction, that is easy to perform in all kind of laboratories and compromises on the myocardial function significantly.

Following approval by the local authorities, 14 domestic pigs were instrumented for measurement of arterial, central venous, left atrial and left ventricular pressures. Myocardial infarction was induced in eight pigs by clipping the circumflex artery close to its origin from the left coronary artery (infarction group; n = 8). Six animals (no infarction group, n = 6) served as no-infarct controls. Following a 4-min period of cardiac arrest, internal cardiac massage was performed in these two groups, and haemodynamics were recorded during the first 30 min of reperfusion.

All animals were resuscitated successfully. Compared to the no-infarction group, the infarction group showed significantly decreased myocardial contractility, coronary perfusion pressure and cardiac index (30 min after restoration of spontaneous circulation: infarction group: 57 ± 7 and 89 ± 19 mL min−1 kg−1 in the no-infarction group; mean ± SD; P < 0.05) during reperfusion. Two animals from the infarction group (25%), but none of the animals in the no-infarction group, died during the reperfusion period.

These data demonstrate that clipping of the circumflex artery leads to a reduced myocardial performance after successful resuscitation, whereas the rate of restoration of spontaneous circulation is not reduced. Therefore, this set-up provides a reproducible model for future studies of post-resuscitation haemodynamics and treatment.

The postoperative monitoring and treatment of the patient undergoing aortic valve replacement is a complex challenge. Echocardiography is the only method which provides dynamic and real-time bedside imaging of the heart. Focused assessed transthoracic echocardiography has been shown to provide a usable window for cardiac imaging in a mixed ICU population. The aim of this study was to evaluate the feasibility of perioperative imaging of the heart and pleura according to the focused assessed transthoracic echocardiography protocol in patients scheduled for aortic valve replacement.

Thirty-five adult patients scheduled for aortic valve replacement were followed perioperatively with focused assessed transthoracic echocardiography examinations. A Vivid-7 echo-machine and a 2.5 MHz matrix transducer with second-harmonic imaging were used for data acquisition. The image quality for the cardiac window was graded 1–5 (1 = no image, 2 = poor and unusable image quality, 3 = usable image quality, 4 = good image quality and 5 = perfect image quality). A score ⩾3 equalled an image quality judged to be of sufficient quality to be interpreted and thereby to contribute to clinical decision-making.

All patients had at least one usable window preoperatively. At least one usable window was obtained in 88% of patients on the first postoperative day, and in 97% at discharge. The image quality changed over time, with the poorest quality being observed on the first postoperative day. The apical view with the patient in the left lateral position provided the best cardiac window on all occasions. The presence of drains did not significantly affect the achievability of a satisfactory examination. The number of patients with pleural effusion was relatively high. On the first postoperative day, 10 subjects had unilateral and one subject had bilateral pleural effusions. At discharge, 14 patients had unilateral and four patients had bilateral effusions.

We conclude that the image quality of the heart and pleura, according to the focused assessed transthoracic echocardiography concept, is sufficient to undergo interpretation and thereby contribute to the perioperative clinical decision-making in patients with aortic stenosis.

The aim of this prospective, randomized, double-blind, placebo-controlled study was to evaluate the efficacy of phrenic nerve infiltration with ropivacaine 0.2% on the incidence and severity of ipsilateral shoulder pain after thoracotomy in patients receiving continuous thoracic epidural analgesia.

Fifty ASA physical status II–III patients, receiving thoracic epidural analgesia for post-thoracotomy pain, were randomly allocated to receive infiltration of the ipsilateral phrenic nerve with either ropivacaine 0.2% 10 mL (ropivacaine, n = 25), or saline 0.9% (control, n = 25) just before lung expansion and chest closure. A blinded observer recorded the incidence and severity of ipsilateral shoulder pain 6, 12, 24, 36 and 48 h after surgery. Postoperative respiratory function was also evaluated with blood gas analyses.

The cumulative incidences of ipsilateral shoulder pain during the first 24 h after surgery were 8/25 in the ropivacaine and 16/25 in the control groups (P = 0.047), with median (range) onset times for shoulder pain of 2 (2–24) h with ropivacaine and 0.5 (0.5–24) h in controls (P = 0.005). No differences were reported on the second postoperative day. The areas under the curves of the amount of pain over time were 0 (0–2760) mm h for the ropivacaine and 350 (0–1900) mm h for the control groups (P = 0.06). Postoperatively, similar reductions in indices of oxygenation were observed in both groups.

Phrenic nerve infiltration with ropivacaine 0.2% 10 mL reduced the incidence and delayed the onset of ipsilateral shoulder pain during the first 24 h after open lung resection, with no clinically relevant effects on respiratory function.

Significant start-up delays are inherent to syringe infusion pumps, particularly at low infusion rates, as routinely used in children’s anaesthesia and intensive care. Such delays are mainly the result of engagement of gears in the mechanical drive or compliance of the syringe assembly. The purpose of the present study was to determine the effect of flow rate, syringe size and syringe architecture on fluid delivery during infusion start-up.

Elapsed time from infusion start to achievement of steady-state flow was gravimetrically determined for various infusion rates (0.1, 0.5, 1 mL h−1), different syringe sizes (10-, 20-, 30-, 50-mL) and syringes of two different brands (BD and Codan). Four measurements for each condition were performed with two identical Alaris® Asena™ GH syringe infusion pumps (total of eight experiments). Statistical analysis was done by two-way ANOVA with Bonferroni’s post-test; P < 0.05 was considered significant.

Start-up time was from 3.6 ± 0.9 min (BD 10-mL syringe, 1.0 mL h−1) to 74.5 ± 26.6 min (BD 50-mL syringe, 0.1 mL h−1). Overall, the start-up time markedly increased with lower flow rate (0.1 mL h−1 vs. 1 mL h−1; P < 0.0001), larger syringe size (50 mL vs. 10 mL; P < 0.01), and the BD brand in comparison with the Codan syringes (P < 0.01).

Highest possible flow rate, smaller sized syringes and syringe plungers with reduced compressibility should be preferred in order to avoid significant start-up delays in fluid delivery.

Analgesics and anaesthetics have diverse synaptic actions that nonetheless have a common net inhibitory action on neuronal discharge. It is puzzling, therefore, that these two classes of compounds have fundamentally different affects, one blocking pain and the other consciousness. Indeed, beyond the isolated synapse, little is known of the larger scale mechanisms that mediate actual function, for example, transient neuronal assemblies. It was hypothesized that the two classes of drugs might have, respectively, differential effects on transient activation of these assemblies of neurons working together.

Hippocampal tissue from juvenile Wistar rats was used for in vitro optical imaging with voltage-sensitive dyes and simultaneous field potential recordings. The response to paired pulse stimulation of the hippocampus was recorded in the presence and absence of two types of analgesic (morphine and gabapentin) and two types of anaesthetic (thiopental and propofol).

Optical imaging and electrophysiology used in parallel yield quite different results. Most consistently, the imaging technique was able to detect an enhanced period of activation following anaesthetic, but not analgesic application. This effect was not readily seen from electrophysiology field potential recordings.

These findings suggest that, irrespective of the effects of the two drug classes at a synaptic level, the dynamics of transient neuronal assemblies are modified selectively by anaesthetics and not analgesics.

Postoperative nausea and vomiting after craniotomy may increase intracranial pressure and morbidity in children. This prospective, randomized, placebo-controlled and double-blinded study was designed to evaluate the antiemetic efficacy of prophylactic ondansetron after intracranial tumour resections in children.

Ninety children were divided into three groups and received saline (Group 1), ondansetron 150 μg kg−1 intravenously at dural closure (Group 2) or two doses of ondansetron 150 μg kg−1 intravenously, the second dose repeated after 6 h (Group 3). Episodes of nausea, emesis and side-effects were noted for 24 h postoperatively.

Overall 24 h incidence of postoperative nausea and vomiting was not significantly different among the three groups (9 (37.5%) in Group 1 vs. 7 (27%) in Group 2 and 8 (32%) in Group 3, P = 0.73). No difference in rescue antiemetic treatment or postoperative nausea and vomiting at specific time intervals (0–6 and 6–24 h postoperative period) was seen among the three groups. No significant side-effects were noted in any of the three groups.

Ondansetron, in this study of 90 children, was not very effective in preventing nausea and vomiting after neurosurgical operations.

The laryngeal mask has become a widely accepted alternative to endotracheal intubation and mask ventilation. The laryngeal tube is a relatively new supraglottic airway device for airway management. We compared the new version of the laryngeal tube with the laryngeal mask.

In a randomized design, either a laryngeal tube (n = 66) or a laryngeal mask (n = 66) were inserted. Ease of insertion, oxygenation and ventilation, spirometry data and postoperative airway morbidity were determined.

After successful insertion, it was possible to maintain oxygenation and ventilation in all the patients. Insertion success rates after the first, second and third attempts were 84.8% (n = 56), 12.1% (n = 8) and 3% (n = 2) for the laryngeal tube compared with 56.1% (n = 37), 25.8% (n = 17) and 18.2% (n = 12) for the laryngeal mask (P = 0.001). There was no significant difference in peak airway pressure, and dynamic compliance between the groups (P > 0.05). Blood on the cuff after removal of the device was noted in one patient with the laryngeal tube and in 10 patients with the laryngeal mask. Six patients in the laryngeal mask group complained of hoarseness (P = 0.012).

With respect to clinical function, the new version of the laryngeal tube and the laryngeal mask are similar and either device can be used to establish a safe and effective airway in paralysed patients.

We compared heart rate dynamics during surgical levels of propofol and sevoflurane anaesthesia in a highly standardized setting.

We recorded electrocardiography from 24 anaesthetized healthy male subjects. In the first parallel part of the study, the subjects were anaesthetized either with sevoflurane (n = 8) or propofol (n = 8) targeted to match 1.0, 1.5 and 2.0 minimal alveolar concentration/effective concentration 50. In the second part, a separate group (n = 8) underwent four different anaesthetic regimens targeted to bispectral index 40: sevoflurane alone, sevoflurane + 70% nitrous oxide, propofol alone and propofol + 70% nitrous oxide. The electrocardiography data were analysed using conventional time and frequency domain methods, and the approximate entropy method, which estimates the complexity of the data.

The induction of anaesthesia was followed by an overall reduction of heart rate variability, evident in all frequency bands in the spectral analysis, and also in the time domain measures. Approximate entropy decreased at 1 effective concentration 50 with propofol and at 2 minimal alveolar concentration with sevoflurane. In the second part of the study, the time domain variables and high-frequency spectral power were all similarly reduced by sevoflurane and propofol anaesthesia, with and without nitrous oxide. Approximate entropy tended to decrease during propofol anaesthesia.

Hypnotic levels of sevoflurane and propofol anaesthesia suppressed the heart rate variability measured using conventional analysis methods. Deeper surgical levels of anaesthesia also reduce the complexity of heart rate variability.

Levobupivacaine in combination with sufentanil may be used for labour or postoperative regional analgesia. The risk of bacterial growth within these contained solutions for several hours at room temperature is unknown. We investigated the in vitro antimicrobial effect of levobupivacaine and sufentanil against common micro-organisms encountered during regional anaesthesia.

Standardized suspensions of Staphylococcus aureus, Staphylococcus epidermidis and Escherichia coli were incubated for 1, 3, 6 and 24 h at 25°C, with saline (as control), sufentanil 0.5 or 0.75 μg mL−1, levobupivacaine hydrochloride 5.6 mg mL−1 and concentrations of 1.4, 2.8 and 5 mg mL−1 of levobupivacaine hydrochloride with sufentanil 0.5 μg mL−1. Colony counts were compared after 24 h incubation at 37°C.

No bacterial growth was observed on any bacterial strain for any solution tested throughout the experiment.

Our results suggest that solutions of levobupivacaine combined with sufentanil may be used for 24 h at room temperature during regional anaesthesia with no risk of bacterial growth.