Summary

A variety of laboratory and clinical studies clearly indicate that exposure to anaesthetic agents can lead to a pronounced protection of the myocardium against ischaemia–reperfusion injury. Several changes in the protein structure of the myocardium that may mediate this cardioprotection have been identified. Ischaemia–reperfusion of the heart occurs in a variety of clinical situations including transplantations, coronary artery bypass grafting or vascular surgery. Ischaemia may also occur during a stressful anaesthetic induction. Early restoration of arterial blood flow and measures to improve the ischaemic tolerance of the tissue are the main therapeutic options (i.e. cardioplegia and betablockers). There exists increasing evidence that anaesthetic agents interact with the mechanisms of ischaemia–reperfusion injury and protect the myocardium by a ‘preconditioning’ and a ‘postconditioning’ mechanism. Hence, the anaesthesiologist may substantially influence the critical situation of ischaemia–reperfusion during surgery by choosing the appropriate anaesthetic agent. This review summarizes the current understanding of the mechanisms of anaesthetic-induced myocardial protection. In this context, three time windows of anaesthetic-induced cardioprotection are discussed: administration (1) during ischaemia, (2) after ischaemia–during reperfusion (postconditioning) and (3) before ischaemia (preconditioning). Possible clinical implications of these interventions will be reviewed.

Summary

Background and objective: Accurate assessment of preload responsiveness is an important goal of the clinician to avoid deleterious volume replacement associated with increased morbidity and mortality in mechanically ventilated patients. This study was designed to evaluate the accuracy of simultaneously assessed stroke volume variation and pulse pressure variation using an improved algorithm for pulse contour analysis (PiCCO plus®, V 5.2.2), compared to the respiratory changes in transoesophageal echo-derived aortic blood velocity (ΔVpeak), intrathoracic blood volume index, central venous pressure and pulmonary capillary wedge pressure to predict the response of stroke volume index to volume replacement in normoventilated cardiac surgical patients. Methods: We studied 20 patients undergoing elective coronary artery bypass grafting. After induction of anaesthesia, haemodynamic measurements were performed before and after volume replacement by infusion of 6% hydroxyethyl starch 200/0.5 (7 mL kg−1) with a rate of 1 mL kg−1 min−1. Results: Baseline stroke volume variation correlated significantly with changes in stroke volume index (ΔSVI) (r2 = 0.66; P < 0.05) as did baseline pulse pressure variation (r2 = 0.65; P < 0.05), whereas baseline values of ΔVpeak, intrathoracic blood volume index, central venous pressure and pulmonary artery wedge pressure showed no correlation to ΔSVI. Pulse contour analysis underestimated the volume-induced increase in cardiac index measured by transpulmonary thermodilution (P < 0.05). Conclusions: The results of our study suggest that stroke volume variation and its surrogate pulse pressure variation derived from pulse contour analysis using an improved algorithm can serve as indicators of fluid responsiveness in normoventilated cardiac surgical patients. Whenever changes in systemic vascular resistance are expected, the PiCCO plus® system should be recalibrated.

Summary

Background and objective: The aim was to determine whether the administration of aprotinin can cause deleterious effects on renal function in cardiac surgery with cardiopulmonary bypass (CPB). Methods: Sixty consecutive patients with normal preoperative renal function undergoing elective coronary artery bypass surgery with CPB using the same anaesthetic; CPB and surgical protocols were randomized into three groups. Patients received placebo (Group 1), low-dose aprotinin (Group 2) or high-dose aprotinin (Group 3). Renal parameters measured were plasma creatinine, α1-microglobulin and β-glucosaminidase (β-NAG) excretion. Measurements were performed before surgery, during CPB and 24 and 72 h, and 7 and 40 days postoperatively. Results: In the three groups, α1-microglobulin and β-NAG excretions significantly increased during CPB, at 24 and 72 h, and 7 days postoperatively (P < 0.05) and had returned to preoperative levels at postoperative day 40. Plasma creatinine levels were within normal values at times recorded. In Groups 2 and 3, α1-microglobulin excretion during CPB was significantly higher than in Group 1 (P < 0.001), and 24 h after surgery it still remained significantly higher in Group 3 compared to Groups 1 and 2 (P < 0.05). Conclusions: Aprotinin caused a significant increase in α1-microglobulin excretion but not in β-NAG excretion during CPB, which may be interpreted as a greater renal tubular overload without tubular damage. This effect persisted for 24 h after surgery when high-dose aprotinin doses had been administered. Creatinine plasma levels were not sensitive to detect these prolonged renal effects in our study.

Summary

Background and objective: The ease of endotracheal intubation has been recently shown to affect the incidence of laryngeal injury. There remains controversy as to whether or not a muscle relaxant is routinely required for tracheal intubation. This study examined conditions of intubation in our routine practice, which employs a relaxant-sparing approach. Methods: All adult patients scheduled for surgery with general anaesthesia were prospectively included. A muscle relaxant was used to facilitate intubation when it was required for the surgical procedure and/or otherwise regarded as necessary by the anaesthesiologist. In the remaining patients, a relaxant-free intubation was performed. Intubating conditions were evaluated in all the patients as well as the post-intubation laryngeal symptoms. Results: Between March and July 2003, 612 patients were consecutively included. A muscle relaxant was used in 32% of patients and no relaxant in the remaining patients (68%). Clinically acceptable intubating scores were observed in 98.4% overall with no significant difference between the two groups. Excellent conditions occurred more frequently in the relaxant group as compared to the relaxant-free group, 87% vs. 72%, P = 0.005. Laryngeal symptoms occurred in 184 (33%) patients with no difference between the two groups. Conclusions: Our relaxant-sparing approach did not increase the incidence of poor conditions of intubation nor laryngeal symptoms. However, excellent conditions occurred more frequently in the relaxant group. A more flexible approach to the issue of the need for neuromuscular blockade prior to intubation is proposed.

Summary

Background and objective: Since the introduction of the laryngeal mask into clinical practice, various additional supraglottic ventilatory devices have been developed. Although it has been demonstrated that the laryngeal tube is an effective airway device during positive pressure ventilation no clinical study has been performed thus far regarding its use in patients with predicted ventilation and intubation difficulties. Methods: The aim of this study was to prospectively evaluate the use of the laryngeal tube for temporary oxygenation and ventilation in adult patients with supraglottic airway tumours scheduled to undergo a pharyngeal–laryngeal oesophagoscopy and bronchoscopy under general anaesthesia. In addition to our standard airway management with face mask ventilation and rigid bronchoscopy, all patients were temporarily ventilated with an laryngeal tube. Also, in patients requiring laryngeal biopsies, endotracheal intubation was performed with a 6.0 mm microlaryngeal tracheal tube. Minute ventilation volumes, tidal volumes, ventilation pressures, end-expiratory CO2 concentration, oxygen saturation and arterial blood gas samples were measured. Results: From 54 enrolled patients only patients with relevant tumour masses were evaluated (n = 23). Mask ventilation was performed without difficulty in 15 of 23 patients. Mechanical ventilation with the laryngeal tube was possible in 22 of 23 patients with an audible leak present in three. Conventional endotracheal intubation was successfully performed in 19 of 23 patients. During face mask ventilation, minute volume, tidal volume, ventilation pressure, end-tidal CO2, oxygen saturation and arterial PO2 were significantly lower and PCO2 significantly higher (P < 0.05, paired t-test). No statistically significant differences were noted between the laryngeal tube and the microlaryngeal tracheal tube. Conclusions: The possibility of difficult ventilation and intubation must always be considered in patients with supraglottic airway tumours. In these cases, the laryngeal tube can be considered for routine airway management and may be useful in the ‘cannot-intubate’ situation although difficulties should be anticipated in patients with previous irradiation, specifically of the throat area.

Summary

Background and objective: Percutaneous nephrolithotripsy (PCNL) is used for the fragmentation and removal of stones from the renal pelvis and renal calyceal systems. We compared the effects of propofol–alfentanil or propofol–remifentanil anaesthesia on haemodynamics, recovery characteristics and postoperative analgesic requirements during percutaneous nephrolithotripsy. Methods: Thirty non-premedicated patients were randomly allocated to receive either propofol–alfentanil (Group A) or propofol–remifentanil (Group R). The loading dose of the study drug was administered over 60 s (alfentanil 10 μg kg−1 or remifentanil 1 μg kg−1) followed by a continuous infusion (alfentanil 15 μg kg−1 h−1 or remifentanil 0.15 μg kg−1 min−1). Propofol was administered until loss of consciousness and maintained with a continuous infusion of 75 μg kg−1 min−1 in both groups. Atracurium was given for endotracheal intubation at a dose of 0.5 mg kg−1 and maintained with a continuous infusion of 0.4 mg kg−1 h−1. Mean arterial pressure heart rate, the total amount of propofol, time of recovery of spontaneous ventilation, extubation and eye opening in response to verbal stimulus and analgesic requirement were recorded. Results: In Group A, mean arterial pressure was higher at the first minute in the prone position, and during skin incision and lithotripsy, and heart rate was higher during skin incision and lithotripsy when compared with Group R (P < 0.05). The total amount of propofol did not differ between groups. Time of recovery of spontaneous ventilation, extubation and eye opening were significantly shorter in Group R than Group A (P < 0.05). Conclusions: Both propofol–remifentanil and propofol–alfentanil anaesthesia provided stable haemodynamics during percutaneous nephrolithotripsy, whereas propofol–remifentanil allowed earlier extubation.

Summary

Background and objectives: Failed endotracheal intubation is a principal cause of morbidity and mortality in anesthetized patients. The aim of this study was to investigate the efficiency of lateral neck radiography in predicting difficult intubation. Methods: In a prospective triple-blind study, 100 patients (aged 18–89 yr), scheduled for elective surgery were randomly selected. Lateral neck X-ray was obtained from each of the patients before operation. Several angles and parameters on the X-ray were proposed to illustrate a relationship with easy or difficult intubation. A radiologist recorded these angles before the operation. An anaesthesiologist also determined the Mallampati score preoperation. At the time of intubation, two other anesthesiologists performed a laryngoscopy and, according to established criteria, identified the patients as easy or difficult intubation. The results were then compared with each other. Results: Fifteen patients were identified as having difficult intubation (laryngoscopy Grades III and IV). Sensitivity and specificity of the Mallampati Class test were 26% and 100%, respectively. The sensitivity and specificity of the lateral neck X-ray for three measured angles were 100%. The positive and negative predictive values (NPVs) for those angles were 100% and for Mallampati classification were 100% and 80%, respectively. Conclusions: Compared to the Mallampati Class test, our method of analyzing the lateral X-ray, although not as easy and universally applicable as Mallampati Class test, proved to be a suitable method for predicting difficult intubation.

Summary

Background and objective: Volatile anaesthetics depress excitatory signal transmission by potentiating the inhibitory action of GABAA receptors and there is strong evidence that this is related with anaesthesia. Using primary hippocampal cultures we analyzed the possibility that the volatile anaesthetics enflurane and sevoflurane depress excitatory signal transmission by activation of adenosine A1 receptors. Methods: Primary rat hippocampal cultures on 4 cm poly-l-lysine coated glass coverslips were loaded with the Ca2+-indicator fluo-3 and incorporated in a gastight, temperature-controlled perfusion chamber. The intracellular Ca2+-concentration was monitored with a confocal laser-scanning microscope (BioRad) using the 488 nm laser line of a krypton–argon laser for excitation and the Lasersharp Acquisition software for analysis. Results: Continuous perfusion in Mg2+-free medium generated spontaneous synchronized calcium oscillations, which were dose dependently depressed by the volatile anaesthetics enflurane and sevoflurane (0.25–1 minimum alveolar concentration). Addition of 100 nmol of 2-chloro-N6-cyclopentyladenosine, a specific adenosine A1 receptor antagonist, partly reversed the anaesthetic-induced inhibition of the oscillation amplitude of the oscillating cells. The effect of the anaesthetics was mimicked by the addition of S-(p-nitrobenzyl)-6-thioguanosine, an adenosine transport inhibitor and by the addition of 5-amino-5-deoxyadenosine, an inhibitor of adenosine kinase. Conclusions: The volatile anaesthetics sevoflurane and enflurane activate adenosine A1 receptors in primary rat hippocampal cultures. This effect is mediated by liberation of adenosine most likely by an interaction of the volatile anaesthetics with adenosine transport or key enzymes in adenosine metabolism.

Summary

Background and objectives: Sodium bicarbonate is the most physiological alkalinizing agent. The effect of a new bicarbonated Ringer's solution (BRS) containing Mg2+, on metabolic acidosis and serum magnesium abnormality were evaluated and compared with those of acetated Ringer's (ARS), lactated Ringer's (LRS) and Ringer's (RS) solutions in an experimental haemorrhagic shock model with dogs. Methods: Animals were randomly divided into six groups (n = 6 in each group), a sham-operated group, an operated group without infusion, and 4 operated groups with infusion (BRS, ARS, LRS and RS groups). Each RS was intravenously administered at 60 mL kg−1 h−1 for 1.5 h. Arterial blood gases, plasma electrolytes and cardiovascular parameters were analysed. Results: BRS significantly improved blood base excess values, which were decreased by blood-letting, faster and more markedly than did LRS and RS (BRS −6.3 ± 0.5 mEq L−1; LRS −9.2 ± 1.1 mEq L−1; RS −12.4 ± 1.0 mEq L−1 at the end of infusion). The alkalinizing effect of BRS tended to be better than that of ARS but not significantly so. The serum Mg2+ concentration was well-maintained by BRS as compared to other RS (BRS 1.5 ± 0.0 mg dL−1; ARS 1.2 ± 0.0 mg dL−1; LRS 1.1 ± 0.0 mg dL−1; RS 1.3 ± 0.1 mg dL−1, at the end of infusion). Conclusions: These results suggest that BRS is a suitable perioperative solution for metabolic acidosis and serum electrolyte balance among RS tested.

Summary

Background and objective: The aim of this study was to investigate any possible protective effect of ketamine in acute muscular ischaemia and reperfusion injury by measuring malondialdehyde using thiobarbituric acid assay in rats. Methods: Twelve female Wistar albino rats were anaesthetized with chloral hydrate and randomly assigned into two groups to receive ketamine 1 mg kg−1 min−1 or saline infusion. Blood and gastrocnemius muscle samples were obtained 10 min after onset of infusion, before ischaemia. Then, femoral arteries were clamped for 30 min. Blood and muscle samples were obtained at the 30th minute of ischaemia and 10 min after reperfusion. Results: Muscle malondialdehyde concentrations were 27.88 ± 2.45, 27.62 ± 3.98 before ischaemia, 32.10 ± 4.19, 30.77 ± 2.73 in the 30th minute of ischaemia and 44.34 ± 2.45, 34.83 ± 2.78 after reperfusion in saline and ketamine-treated rats, respectively (nmol g−1, mean ± SD). The muscle malondialdehyde level after reperfusion was lower in ketamine-treated rats compared to saline group (P < 0.002). Plasma malondialdehyde levels were 3.77 ± 0.16, 3.78 ± 0.18 before ischaemia, 3.81 ± 0.25, 4.00 ± 0.86 at the 30th minute of ischaemia and 4.00 ± 0.53, 3.94 ± 0.95 after reperfusion, respectively, in saline and ketamine-treated rats (μmol L−1, mean ± SD). The effect of ketamine on muscular malondialdehyde was not observed in concurrent plasma malondialdehyde levels. Conclusion: Ketamine was found to attenuate acute ischaemia–reperfusion injury in muscle tissue in rats (muscular protective). Ketamine may attenuate lipid peroxidation in muscle tissue in tourniquet-requiring manoeuvres.

Summary

Background and objective: Hypotension, the commonest side-effect of spinal anaesthesia, results from sympathetic denervation. This study compared patient positioning (supine vs. decubitus) on haemodynamic variables during spinal anaesthesia. Methods: After intravenous crystalloid preloading with 5 mL kg−1, hyperbaric bupivacaine 0.5% 2.5 mL was injected intrathecally at the L2–3 or L3–4 interspace. Patients were then randomly assigned to be positioned immediately supine and horizontal for 30 min (Group SUP, n = 12), or remained in the lateral decubitus position (fractured hip dependent) for 30 min (Group LAT, n = 14). Systolic blood pressure, mean arterial pressure, and loss of sensation of pinprick sensation were recorded prior to induction of spinal anaesthesia (baseline) and at 1, 2, 3, 5, 10, 15, 30, 45, 60, 90 and 120 min after intrathecal injection. Results: In Group SUP, the percent maximum systolic blood pressure (36 ± 13%) and percent maximum mean arterial pressure decreases (27 ± 13%) were significantly greater (P < 0.05) than in Group LAT (30 ± 8% and 23 ± 11%, respectively). Additionally, there was a borderline significant delay in the time to maximum systolic blood pressure decrease in Group LAT (38 ± 30 min) when compared with Group SUP (20 ± 17 min, P = 0.06), while the total dose of ephedrine required in the SUP group (30 mg) was greater than that required in the LAT group (15 mg, P = 0.05). In Group LAT patients, the mean level of denervation on the operative side extended 2 dermatomes more cephalad than in Group SUP. Conclusions: Lateral positioning for spinal anaesthesia delays the onset of hypotension, while requiring smaller total doses of vasoconstrictors for blood pressure maintenance.