Summary

Background and objectives: This study was designed to investigate the role of nitric oxide on catalepsy induced by fentanyl and haloperidol. Methods: Male albino mice were treated either with fentanyl (0.1–0.2 mg kg−1, s.c.) or haloperidol (0.5–2 mg kg−1, i.p.). The non-selective nitric oxide synthase inhibitor, NG-nitro-l-arginine (10 mg kg−1, i.p.), selective neuronal nitric oxide synthase inhibitor, 7-nitroindazole (3 mg kg−1, i.p.), and nitric oxide donors, l-arginine (30–300 mg kg−1, i.p.) and d-arginine (30 mg kg−1, i.p.), were applied 20 min prior to fentanyl or haloperidol injection. A μ-opioid receptor antagonist naloxone (1 mg kg−1, i.p.) was also given in some groups. The cataleptic status of mice was assessed by placing animals in a rearing position in the cage. If the mouse maintained cataleptic posture for more than 20 s, it was scored as cataleptic and duration of catalepsy was expressed in terms of minutes. Results: Both NG-nitro-l-arginine and 7-nitroindazole prolonged fentanyl-induced catalepsy (fentanyl: 3.6 ± 0.8 min; fentanyl + NG-nitro-l-arginine: 77.4 ± 14.6 min, fentanyl + 7-nitroindazole: 56.0 ± 10.4 min; n = 6; P < 0.01). This effect was reversed by l-arginine and naloxone, but not by d-arginine. Nitric oxide synthase inhibitors also prolonged the cataleptic action of haloperidol but to a lesser extent (haloperidol: 72.0 ± 6.3 min; haloperidol + NG-nitro-l-arginine: 98.5 ± 6.3 min, haloperidol + 7-nitroindazole: 89.6 ± 2.2 min; n = 6; P < 0.05). The prolongation of haloperidol-induced catalepsy with nitric oxide synthase inhibitors was not reversed by l-arginine. Conclusion: These results suggest a common mechanism between μ-opioid receptors and the nitric oxide system in the development of fentanyl-induced catalepsy in mice different from haloperidol-induced catalepsy.

Summary

Background and objective: To compare the inotropic and lusitropic effect of lidocaine and mepivacaine on rat papillary muscle. Methods: Effects of lidocaine and mepivacaine (10−8−10−3 M) were studied in rat left ventricular papillary muscles in vitro at a calcium concentration of 1 mmol, under low (isotony) and high (isometric) loads. Results: Lidocaine induced a significant negative inotropic effect in isotonic and isometric conditions whereas mepivacaine did not. Mepivacaine only induced a negative inotropic effect when added as a bolus for the highest concentration and this effect was significantly more pronounced with lidocaine than with mepivacaine (active force at 10−3 M: 63 ± 10 vs. 84 ± 10% of baseline, P < 0.05). Increasing calcium concentration resulted in a greater positive inotropic effect in the control (199 ± 11% of baseline) and mepivacaine groups (197 ± 22% of baseline) when compared to the lidocaine group (163 ± 19% of baseline, P < 0.05 vs. lidocaine and control groups), suggesting an impairment on intracellular Ca2+ handling by lidocaine. A negative lusitropic effect under low load was observed only for mepivacaine and suggested an impairment of sarcoplasmic reticulum function. Lidocaine and mepivacaine did not modify postrest potentiation but significantly depressed the force–frequency relationship. Conclusions: The negative inotropic and lusitropic effects induced by lidocaine were more important than that of mepivacaine and may involve an impairment of intracellular Ca2+ handling.

We determined (a) the haemodynamic responses to intubating laryngeal mask (ILM) airway insertion/intubation and removal in anaesthetized patients, and (b) whether the timing of ILM removal influences these responses. One-hundred and twenty patients without cardiovascular disease were studied. ILM airway insertion/intubation was 5 min after induction with propofol 2mg kg−1 and maintenance of anaesthesia with sevoflurane 2% in oxygen 33% and nitrous oxide. Patients were randomly assigned for removal of the intubating laryngeal mask airway at 1, 3 and 5 min after successful intubation. Systolic and diastolic arterial pressures and heart rate were recorded preinduction (baseline), before ILM airway insertion/intubation, at 1-min intervals after insertion/intubation, and at 1-min intervals for 5 min after ILM removal. ILM insertion was successful at the Arst attempt in all patients, but 46 patients required more than one intubation attempt. Compared with baseline values, there were no increases in systolic or diastolic arterial pressure, but there was an increase in heart rate 1 min after ILM insertion/intubation (9%, P < 0.001) and 1 min after ILM removal (8%, P < 0.01). There was a significant increase in systolic and diastolic pressures and heart rate 1 min after ILM insertion/intubation (30%, 31% and 15%; all: P < 0.002) compared with before ILM insertion/intubation values and 1 min after ILM removal (9%, 8% and 7%; all P < 0.05) compared with 1 min after ILM insertion/intubation values. Removal of the ILM 1 min after successful intubation resulted in higher arterial pressure compared with removal at 3 min (systolic arterial pressure 10% higher for 1 min, P=0.01) and 5 min (systolic arterial pressure 10–23% higher for 3 min, P < 0.01; diastolic arterial pressure 10–20% higher for 4 min, P > 0.02), but there were no differences in heart rate between groups. Systolic and diastolic arterial pressures were greater if more than one intubation attempt was required. Early removal or multiple intubation attempts did not exceed baseline haemodynamic values. We conclude that ILM insertion/intubation and removal in anaesthetized patients produces little or no haemodynamic response, even if multiple intubation attempts are required. The timing of removal exerts a small, but clinically unimportant influence on these responses.

Summary

Background and objectives: Patients undergoing eye surgery under regional anaesthesia often require concomitant medication for analgesia and comfort. Remifentanil, with its ultra-short acting-profile, may be useful to reduce pain during retrobulbar nerve block for cataract surgery.

Methods: We performed a prospective, randomized, double-blind study to compare the efficacy of remifentanil for analgesia during retrobulbar nerve block placement. Ninety patients undergoing cataract surgery were randomly divided to receive either remifentanil 0.3 μg kg−1 (n = 45) or an equivalent volume of saline (n = 45). The injection was administered within 30 s in both groups. Patients rated their amount of pain on a 10 cm visual analogue scale. Respiratory frequency, oxygen saturation, cardiac rhythm and postoperative nausea and vomiting (PONV) were recorded.

Results: The mean visual analogue score in the Remifentanil group was 2.56; it was 5.51 in the Saline group (P = 0.001, U-test). Three patients developed bradycardia and three had PONV in the Remifentanil group. Two patients developed tachycardia and one had PONV in the Saline group. No patient developed respiratory depression.

Conclusion: In patients undergoing retrobulbar block placement for eye surgery, 0.3 μg kg−1 remifentanil over 30 s significantly reduced their reported pain. In addition, remifentanil did not increase the risk of untoward side-effects.

Summary

Background and objective: Tissue Doppler echocardiography is proposed to be a relatively preload independent tool for assessment of diastolic function. No data exist on anaesthetized patients in whom myocardial contractility, vascular tone and baroreceptor reflexes are depressed. The aim of this study was to evaluate the effects of preload alterations on tissue velocities in patients during general anaesthesia for coronary arterial bypass surgery. Methods: Fifteen patients referred for elective aorto-coronary bypass surgery were examined by tissue Doppler echocardiography. Early diastolic velocities in the septal and lateral portion of the mitral annulus were measured during preload interventions induced by tilting of the operating table in patients during general anaesthesia both before surgery and after chest closure. To verify changes in preload we used right atrial pressure and pulmonary artery occlusion pressure. Results: Tissue velocities in both the septal and lateral portion of the mitral annulus were significantly higher when preload was increased, compared to when it was decreased. Alterations in diastolic velocities in the septal portion of the mitral annulus prior to surgery: 0.8 ± 0.2 cm s−1, P < 0.001, after surgery: 1.1 ± 0.2 cm s−1, P < 0.001. Alterations in diastolic velocities in the lateral portion of the mitral annulus prior to surgery: 1.4 ± 0.2 cm s−1, P < 0.001, after surgery: 1.1 ± 0.3 cm s−1, P < 0.01. Concomitant changes in right atrial pressure and pulmonary artery occlusion pressure were 11 ± 1 and 12 ± 1 mmHg before surgery and 13 ± 1 and 12 ± 1 mmHg after surgery (P < 0.001 for all), respectively. Conclusion: These results show that tissue velocities of the mitral annulus are preload dependent in patients during general anaesthesia both before and after coronary surgery.

In a randomized double-blind study 60 children, undergoing the extraction of carious deciduous teeth under day-case general anaesthesia, were assigned to receive either intravenous nalbuphine hydrochloride 0.3 mg kg−1 (n = 21), one or more diclofenac suppositories 12.5 mg to a dose of 1–2 mg kg−1 (n = 19), or no analgesia (n = 20). The duration of anaesthesia was longer in the diclofenac group (9.6 min, SD 3.5) compared with control (7.2 min, SD 2.6) and nalbuphine (6.9 min, SD 3.0) groups respectively (P < 0.05). There were no statistically significant differences in post-operative pain scores during the 45 min post-operative period studied between the three groups using an objective pain score. We conclude that using this methodology we were unable to demonstrate any statistically significant differences between the analgesic effects of either intravenous (i.v.) nalbuphine or diclofenac suppositories compared with control.

Summary

Background and objective: To evaluate the temporal changes in respiratory physiological dead space and dynamic compliance of the respiratory system during non-abdominal, upper abdominal and lower abdominal surgery under general anaesthesia with intermittent positive pressure ventilation.

Methods: Thirty-four adult patients were studied (non-abdominal surgery, n = 8; upper abdominal surgery, n = 13 and lower abdominal surgery in lithotomy position, n = 13). Physiological dead space was measured using the single breath carbon dioxide test. The physiological dead space to tidal volume ratio (VD/VT), dynamic compliance of respiratory system, expiratory tidal volume and respiratory rate were measured 10 min after tracheal intubation, and 30, 60 and 120 min later.

Results: In lower abdominal surgery group, VD/VT was significantly increased at 120 min compared with 0 min (P = 0.005) and 30 min (P = 0.009). There were no significant differences in VD/VT between the three groups at any time point. Compliance decreased significantly in patients with upper abdominal (120 min) and lower abdominal surgery (60 and 120 min), but there were no significant changes during non-abdominal surgery.

Conclusions: We found that the VD/VT increased in patients undergoing lower abdominal surgery in lithotomy and head down tilt, and compliance decreased in those undergoing upper abdominal and lower abdominal surgery over time.

Unilateral malignant hyperinflation of the lungs during positive pressure mechanical ventilation was described during aggressive respiratory therapy of unilateral lung disease or in situations of significant difference in compliance between the two lungs. We report a case of malignant hyperinflation of the nondependent lung during chest surgery. The differential diagnosis and treatment with differential lung ventilation are described.

A patient undergoing emergency laparotomy for an acute abdomen developed fatal air embolism as a result of surgical manipulation of a cavitating metastatic lesion of the liver. The diagnosis was made at postmortem examination. This cause of air embolism has apparently not been reported before. The causes and management of air embolism are briefly reviewed. It is concluded that in exceptional circumstances when intubated patients are sent to a recovery area, the continuation of CO2 monitoring into the post-operative period should be considered.

Summary

Background and objective: To compare the accuracy of prognoses made by intensive care physicians with the performance of two indicators, the original Simplified Acute Physiology Score (SAPS) II and a modified version optimized to the patient sample.

Methods: Data from 412 patients consecutively admitted to intensive care units of Göttingen University Hospital, Germany, were collected according to the original score criteria. Information necessary for the computation of SAPS II and the vital status on hospital discharge was recorded. To customize the original SAPS II in our cohort, the database was randomly divided into two subgroups. Logistic regression analysis with physiological values as explanatory variables was used. A bootstrap procedure completed the process. Furthermore, physicians were asked to indicate their prognostic judgement concerning the patients’ hospital mortality.

Results: Discrimination analysis showed the following areas under receiver operating characteristic curves: physicians’ prognoses 0.84 (confidence interval (CI): 0.79–89), SAPS II 0.75 (CI: 0.69–0.80) and customized SAPS 0.72 (CI: 0.66–0.78). The physician's forecast was significantly better, while the customized and the original SAPS were not substantially different as regards their accuracy.

Conclusions: Prognoses made by physicians are superior to objective models. This may result from more extensive knowledge and other kinds of information available to clinicians. A clinician's action also depends on his/her prognosis at the beginning of the treatment, giving raise to a possible correlation between medical outcome and the clinician's prognosis. Our findings indicate that physicians do not limit their prognosis to the objective factors at their disposal, but indicate that they base their decisions on experience and individual observations.

The purpose of this study was to analyse the clinical agreement between cardiac output measurements, obtained using a newly available continuous thermodilution technique, and the conventional intermittent bolus technique. Twenty-four cardiac surgical patients were intra-operatively monitored using both techniques. Additionally, two different averaging modes for the continuous thermodilution technique, either the previous 6 min (group 1) or 3 min (group 2) were compared. The mean difference between the continuous thermodilution technique and the intermittent bolus technique (bias), were calculated at eight selected time points. These ranged from −0.09 to 0.42 litres min−1 in group 1 and from −0.02 to 0.18 litres min−1 in group 2. There were significant differences at any time point between the groups. The relative error between continuous thermodilution and intermittent bolus techniques was <15% for the majority of measurements and was significantly higher in group 1 compared with group 2 just prior to cardiopulmonary bypass. Thus, the continuous thermo-dilution technique produced a clinically acceptable level of accuracy compared with the intermittent bolus technique measurements, especially when using an averaging mode for the previous 3 min.

Summary

Background and objectives: This study compares three modes of patient-controlled epidural analgesia in parturients during labour.

Methods: Eighty-four women were randomized to one of three groups. The epidural solution used in all the three groups was 0.1% bupivacaine with fentanyl 2 μg mL−1. Patients were able to self administer a demand dose of 3 mL with a lockout interval of 6 min in Group A, 6 mL with a lockout interval of 12 min in Group B and 9 mL with lockout interval of 18 min in Group C. All patients received a background infusion at a rate of 6 mL h−1. Visual analogue pain scores, pinprick analgesia and motor block were assessed hourly by a blinded observer. The physician-administered supplementation and the cumulative dose of bupivacaine were also compared between the three groups.

Results: Pain scores, sensory level and motor block were not different among the study groups. Patients' satisfaction was rated good to excellent with no difference among groups. The cumulative dose of bupivacaine was not significantly different. However, there was a trend towards a decreased need for rescue analgesia in Group C. Within each group, the physician-administered supplementations were significantly higher during the second stage of labour than during the first stage (P < 0.05).

Conclusion: The three modes of patient-controlled epidural analgesia supplemented by a background infusion of 6 mL h−1 were equally effective for labour analgesia with a trend for decreased rescue analgesia in the group with a larger bolus dose and a longer lockout interval.

Background and objective Laboratory stress studies found that acute psychological stresses may elicit changes in leukocyte numbers similar to those occurring in physical stresses. Both types of stress evoke – mainly by release of catecholamines – leukocytosis resulting from a release of natural killer cells (NK-cells), of CD8+ T-cells, of monocytes and of neutrophils. However, there is little proof that laboratory stress models can be applied to daily clinical routines. As a likely inductor of an immunological stress response the setting of retrobulbar anaesthesia prior to intraocular surgery permits the study of a short-term painful anaesthetic procedure under highly standardized conditions. This was examined in 16 female patients.

Methods Counts of leukocyte subsets, serum cortisol and cardiovascular variables were measured 30 min and 1 min prior to retrobulbar anaesthesia as well as 2, 15 and 45 min afterwards.

Results The setting of retrobulbar anaesthesia induced an increase in total leukocytes [+380 cells μL−1; P < 0.01 (means; significance level)] mainly due to rising counts of neutrophils (+241 cells μL−1, P < 0.01). Of all lymphocyte subpopulations, natural killer cells increased most markedly (+64 cells μL−1; P < 0.01). Furthermore, the retrobulbar block induced an increase in systolic arterial pressure (+15.2 mmHg; P < 0.01).

Conclusion These changes in immunological and cardiovascular variables are considered to be elements of a sympatho-adrenal stress reaction; catecholamines are considered to induce a demargination of leukocytes by binding to β2-adrenoceptors and by modifying the avidity state of adhesion molecules.

Background and objective: The safety of hypotension induced by sevoflurane and splanchnic organ blood flow remains to be clarified. The aim was to investigate the effects of sevoflurane-induced hypotension on systemic haemodynamics and splanchnic organ blood flows in dogs.

Methods: Mean arterial pressure was maintained at 60 mmHg by increasing sevoflurane concentrations. The renal, hepatic and pancreatic blood flows were measured by using the hydrogen clearance method.

Results: Hypotension induced by sevoflurane resulted in a 50% decrease of mean arterial pressure due to a 30% reduction in systemic vascular resistance associated with a 30% decrease in cardiac index. The mechanisms causing the lower cardiac index were produced by the decreases in heart rate and left ventricular dP/dtmax. Renal, hepatic and pancreatic blood flow were reduced, but the whole-body oxygen consumption did not change during the hypotensive period.

Conclusions: The haemodynamic changes induced by sevoflurane were caused by the suppression of arterial baroreflexes and myocardial depression, but splanchnic organ blood flows, though reduced, could provide adequate peripheral perfusion to meet the decrease in oxygen supply.