Summary

The centrally acting α2-adrenoceptor agonists clonidine and dexmedetomidine have been used with success to provide haemodynamic stability for patients undergoing surgery. Particularly in the case of patients with overt or underlying cardiac disease the actions of α2-adrenoceptor agonists, which include maintenance of stable systemic blood pressure and low heart rate and a reduction in overall oxygen consumption, can be expected to reduce the risk of procedure-related cardiac events. This expectation has been corroborated in clinical trials with clonidine, dexmedetomidine and mivazerol and meta-analyses; additional large controlled trials would be instructive in establishing a robust estimate of the scale of the benefit. In addition, α2-adrenoceptor agonists used as premedication have been shown to substantially reduce anaesthetic requirements among surgical patients, and the use of these agents has been associated with a reduced risk of postoperative delirium, which may be expected to improve considerably the postoperative course for at-risk patients. Dexmedetomidine is the only α2-adrenoceptor agonist currently approved for use in the intensive care unit. A distinctive feature of dexmedetomidine in that setting is that in addition to haemodynamic stability it confers a distinctive and advantageous quality of sedation: patients are tranquil but responsive to requests from attending staff. This review examines the pharmacological principles underlying the use of α2-adrenoceptor agonists as adjuncts to surgery and clinical experience in that indication.

Summary

Objective: The objective of this study was to describe the diastolic pressure–flow relationship and to assess critical occlusion pressure in arterial coronary bypass grafts in human beings. Methods and results: Fifteen patients were studied following elective surgical coronary artery bypass grafting. Flow in the left internal mammary artery bypass to the left anterior descending artery was measured and simultaneously, aortic pressure, coronary sinus pressure and left ventricular end-diastolic pressure were recorded. The zero-flow pressure intercept as a measure of critical occlusion pressure was extrapolated from the linear regression analysis of the instantaneous diastolic pressure–flow relationship. Mean diastolic flow was 46 ± 17 mL min−1, mean diastolic aortic pressure was 60.5 ± 10.0 mmHg. Diastolic blood flow was linearly related to the respective aortic pressure in all patients (R-values 0.7–0.99). The regression lines had a mean slope of 2.1 ± 1.2 mL min−1 mmHg−1. Mean critical occlusion pressure was 32.3 ± 9.9 mmHg and exceeded mean coronary sinus pressure and mean left ventricular end-diastolic pressure by factors of 3.1 and 2.6, respectively. Conclusions: Our data demonstrate the presence of a vascular waterfall phenomenon in the coronary circulation after internal mammary artery bypass grafting. Critical occlusion pressure in arterial grafts considerably exceeds coronary sinus pressure as well as left ventricular end-diastolic pressure and should thus be used as the effective downstream pressure when calculating coronary perfusion pressure. Our data further suggest that the slope of diastolic pressure–flow relationships provides a more rational approach to assess regional coronary vascular resistance than conventional calculations of coronary vascular resistance.

Summary

Background and objective: Cardiopulmonary bypass is known to induce postoperative coagulopathy including fibrinolysis. We have evaluated the effect of the topical use of tranexamic acid in the pericardial cavity on postoperative bleeding following open heart surgery. Methods: One hundred patients, scheduled for elective open heart surgery, were included in this double-blind, prospective, randomized, controlled study. They were allocated to a treatment group (Group I), or placebo group (Group II). Patients with coagulopathies, renal failure, re-do surgery, or recent anti-platelet treatment were excluded. In Group I, tranexamic acid (2 g in 100 mL of saline solution) was poured into the pericardial cavity before sternal closure. Placebo patients received 100 mL of saline. Postoperative blood loss, need for transfusion of blood products and the rate of re-sternotomy for bleeding were documented. Results: During the first postoperative 24 h, cumulative blood loss was significantly higher in Group II compared to Group I (1208 ± 121 mL vs. 733 ± 93 mL, respectively) (P < 0.001). More blood transfusions were administered to Group II patients (4.54 ± 1.4 units) as compared to Group I patients (2.64 ± 1.5 units) (P < 0.01). Conclusion: Topical application of tranexamic acid in patients undergoing primary open heart surgery led to a significant reduction of both postoperative mediastinal bleeding, and rate of re-exploration for haemostasis.

Summary

Background and objective: Bispectral Index® correlates with depth of hypnosis in adult patients. Bispectral index monitoring has been separately examined and validated during both mild and moderate hypothermic cardiopulmonary bypass. However, the effect on bispectral index of these two differing cardiopulmonary bypass temperature regimes has not previously been compared, particularly with the use of volatile anaesthetic agents. Methods: Following Institutional Ethics Committee approval and informed consent, 30 patients undergoing coronary artery bypass grafting had additional bispectral index monitoring. Sixteen patients had mild hypothermic bypass (32–34°C), and 14 had moderate hypothermic bypass (28–30°C). Anaesthesia was standardized, and was maintained with enflurane throughout surgery. Scores were recorded at 14 specific event-related time points during surgery. Results: This study has demonstrated that in this adult population, a relationship exists between bispectral index score and temperature throughout the duration of cardiac surgery, which included mild or moderate hypothermic cardiopulmonary bypass. It also demonstrated that patients which were categorized as having received moderately hypothermic cardiopulmonary bypass had lower bispectral index scores than those patients who received mild hypothermic cardiopulmonary bypass, at time points corresponding approximately with median steady-state bypass temperature, pre-re-warming and early re-warming periods. Conclusions: Moderate hypothermic cardiopulmonary bypass has lower bispectral index scores when compared to mild hypothermic cardiopulmonary bypass, at a steady state of inspired enflurane. This may reflect an actual increase in the depth of hypnosis. However, as this study did not address the physico-chemical changes of the volatile agent or the accuracy of the bispectral index algorithm at lower temperatures, we would not advocate a change in practice based solely on this report.

Summary

Background and objective: Anaesthesiologists need parameters that measure the depth of anaesthesia. In the context of this need, the present study investigated in rats how two variables from the electroencephalogram, the burst suppression ratio and effective correlation dimension correlated with a measure of anaesthetic depth as measured in the strength of a noxious withdrawal reflex. Methods: Eight rats were exposed to different inspiratory concentrations of sevoflurane, each rat in two separate experiments. In the first experiment, spontaneously breathing animals could move freely and no painful stimuli were applied. In the second experiment, in mechanically ventilated restrained anaesthetized rats, the withdrawal reflex was measured every 80 s. In both experiments the electroencephalogram was continuously recorded. The concentration in the effector compartment was estimated using a first order two compartment model. Correlation dimension was computed following the Grassberger/Procaccia/Takens approach with optimized parameter settings to achieve maximum sensitivity to anaesthetic drug effects and enable real-time computation. The Hill, equation was fitted to the data, describing the effect as a function of sevoflurane concentration. Results: Good correlations of Depth of Anaesthesia with correlation dimension as well as burst suppression ratio were established in both types of experiments. Arousal by noxious stimuli decreased burst suppression ratio and increased correlation dimension. The effective sevoflurane concentration associated with 50% of the maximum effect (C50) was higher in experiment II (stimulation) than in experiment I (no stimulation): i.e. for correlation dimension 2.18% vs. 0.60% and for burst suppression ratio 3.07% vs. 1.73%. The slope factors were: γCD = 4.15 vs. γCD = 1.73 and γBSR = 5.2 vs. γBSR = 5.4. Correlation dimension and burst suppression ratio both correlated with the strength of the withdrawal reflex with correlation coefficients of 0.46 and 0.66 respectively (P < 0.001). Conclusions: Both correlation dimension and burst suppression ratio are related to anaesthetic depth and are affected by noxious stimuli. The relationship between anaesthetic depth and burst suppression ratio is confirmed and the potential of correlation dimension is demonstrated.

Summary

Background and objective: In order to identify parameters predicting intensive care unit mortality in patients transferred to a specialized tertiary centre because of progressive acute respiratory distress syndrome, an observational pilot study was carried out involving 94 patients. Methods and Results: Forty-one patients (43.6%) died. Survival was defined as intensive care unit discharge. Survivors were younger (32.0 ± 11.8 vs. 39.1 ± 12.4 yr, P = 0.008), at admission they had a lower acute physiology and chronic health evaluation (APACHE) II score (21.7 ± 5.4 vs. 25.4 ± 5.2, P = 0.0009), higher PaO2/FiO2 (122 ± 79 vs. 79 ± 42 mmHg, P = 0.002), lower positive end-expiratory pressure (10.6 ± 3.1 vs. 12.5 ± 3.7 cmH2O, P = 0.02) and a lower Murray score (2.8 ± 0.63 vs. 3.0 ± 0.62, P = 0.04). No differences were observed for tidal volumes and peak inspiratory pressures. Days of hospitalization and mechanical ventilation prior to transferral were not related to survival. Multivariate analysis of variables assessed on admission detected only differences for age (P = 0.014) and APACHE II (P = 0.005). Odds ratio was 1.06 (95% confidence interval (CI): 1.013–1.119) for age and 1.21 (CI: 1.059–1.381) for APACHE II. Multivariate analysis of changes in respiratory parameters, APACHE II and Murray score during the first 3 days after transferral revealed a significant difference only for positive end-expiratory pressure (P < 0.008). Corresponding odds ratio was 2.40 (CI: 1.25–4.58) for an increase of 1 cmH2O/24 h. Conclusion: Age-related mortality in this small, but highly selected group of patients with established ARDS increased early in life even in a population with an overall mean age of 35.1 yr. APACHE II was the only clinical predictor for mortality on admission. The need for a substantial increase in positive end-expiratory pressure after transferral markedly reduced the chance to survive.

Summary

Background and objective: We have evaluated the effects of propofol and its relationship with K+ channels on human isolated umbilical vessels. Methods: Umbilical vessel rings were suspended in isolated organ baths containing Krebs–Ringer solution. In the first series of experiments the effect of propofol (10−9–10−4M) was examined in a concentration-dependent manner on umbilical vessels precontracted with KCl (60 mmol). In the second series, these effects were studied in the presence of tetraethylammonium. Results: A mild contraction was produced by low dose propofol in both precontracted umbilical artery and umbilical vein segments. 10−4M propofol caused significant relaxation in both umbilical artery and umbilical vein. The relaxation response was significantly reduced by the addition of 10−1 M tetraethylammonium. Conclusion: These results suggested that the responses of propofol on KCl-induced contractions of both umbilical artery and vein were dose dependent, and this effect involved Ca2+ activated K+ channels.

Summary

Background and objective: We examined the efficacy of intraoperative propofol administration to prevent pruritus induced by epidural morphine. Methods: Seventy patients ASA I–II undergoing combined epidural and general anaesthesia for hysterectomy were randomly assigned to two groups, Group P where anaesthesia was induced with propofol and fentanyl and maintained with propofol-nitrous oxide and Group S in which anaesthesia was induced with thiopental and fentanyl and maintained with sevoflurane-nitrous oxide. All patients received a ropivacaine epidural bolus with 3 mg morphine 1 h before the end of surgery. The incidence and severity of pruritus were evaluated every 4 h for the first 12 h postoperatively by blinded observers. Results: The total incidence of pruritus was significantly higher (P = 0.024) in Group S (65.6%) compared to Group P (29%) between 4 and 8 h postoperatively. There were also significantly more patients (P = 0.03) reporting severe pruritus in Group S (22%) compared to Group P (0). Conclusion: Propofol-based general anaesthesia compared to thiopental–sevoflurane-based anaesthesia reduces the incidence and severity of pruritus induced by a single injection of 3 mg epidural morphine with ropivacaine.

Summary

Background and objective: Computerized dynamic posturography using an intentional postural-sway task can be used to assess body-leaning ability and postural-control ability to prevent falls. Falls are the leading cause of morbidity and mortality for the elderly. The purpose of the present study was to evaluate the recovery of intentional dynamic balance function after intravenous sedation with midazolam in elderly subjects in comparison with that in young subjects. Methods: Midazolam was administered in small, divided doses over 4–5 min until the Wilson sedation score reached three in 20 young and 18 elderly male volunteers. The dynamic limits of the stability test, in which subjects leaned their body intentionally as indicated by a cursor moving on a computer screen, was determined before (baseline) and 50, 70, 90, 110, and 130 min after administration of midazolam. Results: The changes from baseline values of path sway and movement time 50 min after the administration of midazolam in elderly subjects (106.8 ± 101.0%, 4.6 ± 3.0 s; mean ± SD) were significantly greater than those (32.9 ± 87.2%, 1.9 ± 2.8 s) in young subjects (P = 0.024, P = 0.008), respectively. Conclusions: The elderly show slower recovery of the intentional dynamic balance function than do young adults after intravenous sedation with midazolam.

Summary

Background and objective: End-stage liver disease is associated with an imbalance in the autonomic nervous system. The purpose of this study was to estimate the effect of liver transplantation on this imbalance. Method: The study involved 10 patients undergoing liver transplantation and 9 patients without liver impairment undergoing liver surgery. The spontaneous baroreflex sensitivity was measured before and 1 month after surgery for the liver surgery group; before and 1, 3, 6, 12 and 18 months after orthotopic liver transplantation. Results: The spontaneous baroreflex slope of patients with end-stage liver disease was decreased before liver transplantation compared to the liver surgery group (3.9 ± 2.5 ms mmHg−1 vs. 9.9 ± 5.0 ms mmHg−1, P = 0.002). The mean slope was significantly increased at 12 and 18 months compared to the pre-transplantation value (3.9 ± 2.5 ms mmHg−1 vs. 8.1 ± 6.6 ms mmHg−1 and 7.4 ± 4.8 ms mmHg−1, respectively; P = 0.042). Nevertheless, further analysis of individual data showed that only four patients exhibited a marked increase in their baroreflex slope 12 months after the liver transplantation whereas it remained decreased in the six others. Conclusions: These results confirm that the baroreflex sensitivity is depressed in end-stage liver disease in line with an autonomic nervous system imbalance. The liver transplantation reverses this disturbance only in some patients.

Summary

Background and objective: Anaesthesiology is considered a stressful occupation. Our purpose was to assess stress and burnout among Portuguese anaesthesiologists. Methods: A cross-sectional survey based on an anonymous questionnaire was sent to all Portuguese anaesthesiologists registered by the Portuguese Medical Association. Data on patient characteristics and professional variables, perceived stress (Perceived Stress Scale), the subscale of work satisfaction of the Pressure Management Indicator scale, burnout (Maslach Burnout Inventory) and main stress factors were collected. The proportion of participation was 31.8%. Results: The average value of perceived stress scale was 24.0 (range: 0–56). Among the 263 anaesthesiologists, 57.9% experienced emotional exhaustion, 44.8% lack of personal accomplishment and 90.9% depersonalisation. Lack of personal accomplishment increased with number of children among women but not among men; depersonalisation was more frequent among anaesthesiologists working in community hospitals and anaesthesiologists with leadership functions experienced less professional stress. Conclusion: There are stress conditions and burnout amongst Portuguese anaesthesiologists. The prevalence of depersonalisation was extremely high in the studied sample. Emotional exhaustion is partially explained by high perceived-stress and low satisfaction with organisation in the job according to Pressure Management Indicator scale.