Summary

Background and objective: The effects of intra-aortic balloon pumping (IABP) on cerebral perfusion are still a matter of debate. End-diastolic reversal of blood flow in cerebral arteries has been observed in a small number of patients. We prospectively investigated the incidence and the amount of transient cerebral artery blood flow reversal during balloon pumping in patients recovering from cardiac surgery.

Methods: In 23 patients receiving IABP support, blood flow velocities in the right middle cerebral artery were assessed by transcranial Doppler-sonography. Additionally, systemic haemodynamics were monitored. In each patient, measurements were performed at three different pump settings: without support, assist ratio 1 : 1 and assist ratio 1 : 2.

Results: In 8 of 23 patients, balloon pumping caused a transient diastolic reversal of blood flow in the middle cerebral artery during balloon deflation. Antegrade mean flow velocity in the middle cerebral artery significantly increased from 57 ± 27 to 61 ± 26 (assist ratio 1 : 1) and 61 ± 29 cm s−1 (assist ratio 1 : 2) (P < 0.05). Taking transient blood flow reversal into account, net mean flow velocity did not increase with balloon pump support. Systemic haemodynamic parameters remained unchanged.

Conclusion: Left ventricular support with IABP significantly changed flow patterns in basal cerebral arteries of our patients. In 35% of patients, support resulted in a transient reversal of intracranial blood flow which counterbalanced a slight increase in mean antegrade flow.

Summary

Background and objective: The aim of this study was to assess time dependent cumulative effects of three different inhalation anaesthetics on QTc interval during the maintenance of anaesthesia.

Method: Seventy-five ASA I–II male patients undergoing inguinal herniorrhaphy were randomly allocated into three groups. No premedication was given. Anaesthesia was induced with thiopental and tracheal intubation was facilitated by vecuronium in all groups. Anaesthesia was maintained with 0.8% halothane (Group I) (n = 25), 1% isoflurane (Group II) (n = 25), or 2% sevoflurane (Group III) (n = 25) and 66% nitrous oxide in oxygen. Three lead electrocardiogram recordings were taken before induction, 2, 5, 10, 15, 30 and 45 min after induction and after extubation. Heart rate, systolic, diastolic, mean arterial pressure and SPO2 were recorded at the same time. Heart rate and corrected QT interval were evaluated by using Bazett's formula. Multivariate analysis of variance for repeated measures was used to determine intergroup and intragroup differences.

Results: There was no statistically significant difference in the baseline QTc values of the groups. There was no difference between QTc values with halothane and sevoflurane. There was a difference between QTc values with isoflurane and those with the other two inhalation anaesthetics (P < 0.05). Although QTc values in the isoflurane group were higher at all times, the critical value of 440 ms was not exceeded.

Conclusion: We conclude that halothane 0.8%, isoflurane 1% and sevoflurane 2% do not prolong QTc interval.

Summary

Background and objective: Although the pressure–volume (P–V) curve has been proposed in the management of mechanically ventilated patients, its interpretation remains unclear. Our aim has been to study the variations of the P–V curve after a recruitment manoeuvre (RM). Our hypothesis was that the lower inflection point (LIP) represents the presence of compressive atelectases, so it should not change after lung recruitment, while the upper inflection point (UIP) reflects reabsorptive atelectases, and an effective recruitment should result in changes at this level.

Methods: Two P–V curves (quasi-static method) separated by an RM (40 cmH2O, two consecutive manoeuvres) were plotted in 35 postoperative patients with criteria of acute lung injury/acute respiratory distress syndrome (ARDS). LIP, UIP and expiratory inflection point (EIP) were defined as the first point where the curve consistently starts to separate from the line.

Results: One to six measurements were obtained per patient (73 procedures). Neither the lower nor the EIPs varied significantly after the RM (P = 0.11 and 0.35, respectively). An UIP was observed in 18 curves (25%) before the RM and disappeared on nine occasions after the recruitment. Similar results were obtained when first measurements only were analysed, and when the cause (pulmonary vs. extrapulmonary), severity of lung injury or duration of mechanical ventilation at first measurement were studied.

Conclusions: An RM does not modify the LIP significantly, but induces the disappearance of the UIP in 50% of the cases in which this point is found.

Summary

Background and objective: Hydroxyethyl starch is frequently used for volume substitution during surgical procedures and for isovolaemic haemodilution. Haemodilution has also been shown to improve tissue oxygen tension in skeletal muscle. However, effects of this volume substitute on tissue oxygen tension of the liver during haemodilution remains unknown.

Methods: Fourteen foxhounds were anaesthetized with fentanyl/midazolam and mechanically ventilated with 30% oxygen. Following splenectomy animals were randomly assigned to a control group without haemodilution but fluid substitution with Ringer's lactate (Group C) or underwent isovolaemic haemodilution to a haematocrit of 25% with hydroxyethyl starch 70/0.5 (Group H). Haemodynamic parameters and oxygen transport during 100 min following isovolaemic haemodilution were measured. Liver oxygen tension was recorded using a flexible polarographic electrode tonometer, whereas in the muscle a polarographic needle probe was used.

Results: Animal characteristics and baseline haematocrit were similar in both groups. At baseline the tissue oxygen tension of liver and skeletal muscle were not different between groups. Haemodilution with hydroxyethyl starch 70/0.5 provided augmentation of mean liver tissue oxygen tension (baseline: 46 ± 13 mmHg; 20 min: 60.3 ± 12 mmHg*; 60 min: 60 ± 16 mmHg*; 100 min: 63 ± 16 mmHg*; *P < 0.05 vs. baseline), while oxygen tensions in Group C remained unchanged (baseline: 48 ± 16 mmHg; 20 min: 52 ± 19 mmHg; 60 min: 49 ± 12 mmHg; 100 min: 52 ± 16 mmHg) and no differences could be detected between groups. Oxygen tension in skeletal muscle changed as follows: Group H – baseline: 24 ± 32 mmHg; 20 min: 32 ± 3 mmHg*[dagger]; 60 min: 33 ± 7 mmHg*[dagger]; 100 min: 33 ± 11 mmHg[dagger]. Group C – baseline: 22 ± 6 mmHg; 20 min: 21 ± 3 mmHg; 60 min: 24 ± 4 mmHg; 100 min: 18 ± 4 mmHg (*P < 0.05 vs. baseline, [dagger]P < 0.05 vs. Group C).

Conclusion: In this animal model, isovolaemic haemodilution with hydroxyethyl starch 70/0.5 increased tissue oxygen tension in liver and skeletal muscle in comparison with baseline values. However, when compared between groups haemodilution only resulted in an increase of tissue oxygen tension in the muscle but not in the liver.

Summary

Background and objective: Unlike midazolam, melatonin premedication is not associated with cognitive impairment in adults despite its anxiolytic properties. The use of melatonin as a premedicant in children has not been reported. This randomized, double-blind, placebo-controlled study compared the perioperative effects of different doses of melatonin and midazolam in children.

Methods: Seven groups of children (n = 15 in each) were randomly assigned to receive one of the following premedicants. Midazolam 0.1, 0.25 or 0.5 mg kg−1 orally, melatonin 0.1, 0.25 or 0.5 mg kg−1 orally each mixed in 15 mg kg−1 acetaminophen, or placebo only (15 mg kg−1 acetaminophen). Anxiety and temperament were evaluated before and after administration of the study drug, on separation from parents and on the introduction of the anaesthesia mask. At week 2 postoperatively, the behaviour of the children was measured by the Post Hospitalization Behaviour Questionnaire.

Results: Melatonin or midazolam each in doses of 0.25 or 0.5 mg kg−1 were equally effective as premedicants in alleviating separation anxiety and anxiety associated with the introduction of the anaesthesia mask. A trend was noted for midazolam to prolong recovery times as the dosage increased. The use of melatonin was associated with a lower incidence (P = 0.049) of excitement at 10 min postoperatively, and a lower incidence (P = 0.046) of sleep disturbance at week 2 postoperatively than that observed with midazolam and control groups. No postoperative excitement was noted in the melatonin groups at 20, 30 and 45 min.

Discussion: Melatonin was not only as effective as midazolam in alleviating preoperative anxiety in children, but it was also associated with a tendency towards faster recovery, lower incidence of excitement postoperatively and a lower incidence of sleep disturbance at week 2 postoperatively.

Summary

Background and objective: Metoclopramide is an antiemetic drug which inhibits plasma cholinesterase activity. We have compared the mivacurium infusion requirements and neuromuscular recovery after administration of metoclopramide to a group of adults compared to a control group.

Methods: Forty-five patients were randomized into three groups. Two groups received either 10 or 20 mg of intravenous (i.v.) metoclopramide and the third group received i.v. saline. Metoclopramide and saline were given 5 min before i.v. induction of anaesthesia. Plasma cholinesterase activity was measured before induction and 30 min after metoclopramide or saline injection. Neuromuscular block was monitored by accelerography using single and train-of-four (TOF) stimulation. The mivacurium intubation dose was followed by an infusion titrated every 5 min to maintain 95% block until the end of surgery when the infusion was stopped. Recovery from mivacurium was then monitored until complete.

Results: Mivacurium infusion rates were significantly lower in the metoclopramide groups. After 45 min of infusion, the infusion rates were 1.82 ± 0.8 and 2.1 ± 1 μg kg−1 min−1 in the 20 and 10 mg metoclopramide groups, respectively, and 6.8 ± 2.7 in the saline group. Time to recovery of TOF to greater than 90% was significantly prolonged in both metoclopramide groups compared to the saline group: 33.2 ± 7.2 and 29.5 ± 10.3 min in the metoclopramide 20 and 10 mg groups, respectively, compared to 22 ± 3.9 in the saline group (P < 0.001 for the 20 mg group compared to control).

Conclusion: Metoclopramide enhances the effect of a mivacurium infusion.

Summary

Background and objective: Initial distribution volume of glucose (IDVG) reliably measures the central extracellular fluid volume in the presence of fluid gain or loss. We hypothesized that IDVG has a close relationship with intrathoracic blood volume (ITBV), which has recently been used as an indicator of cardiac preload. We therefore examined whether IDVG can correlate with ITBV in various fluid volume states.

Methods: Fourteen anaesthetized mongrel dogs were mechanically ventilated. ITBV and cardiac output were measured by single transpulmonary thermodilution technique. IDVG and indocyanine green derived plasma volume (PV-ICG) were determined by the administration of 100 mg kg−1 glucose and 0.5 mg kg−1 indocyanine green solutions, respectively, and calculated by applying a one-compartment model. Three sets of measurements were performed before and after haemorrhage (30 mL kg−1) and subsequent fluid volume loading (90 mL kg−1 of lactated Ringer's solution).

Results: A linear correlation was observed between IDVG and ITBV (r2 = 0.52, n = 42, P < 0.001) and between PV-ICG and ITBV (r2 = 0.44, n = 42, P < 0.001) throughout the procedures. A linear correlation was also observed between changes in IDVG and those in ITBV (r2 = 0.76, n = 28, P < 0.001). The ITBV/IDVG ratio during normovolaemia was 0.26 ± 0.04, which remained unchanged during the procedure.

Conclusion: Results showed that that IDVG has a linear correlation with ITBV, and support the concept that IDVG measurement has potential as a surrogate measure of ITBV in various fluid volume states.

Summary

Background and objective: Inhalational anaesthetics have been associated with hepatotoxicity. Even desflurane, with its low solubility in blood and tissues, and its minimal hepatic biotransformation, is known to affect hepatic integrity. The effects of propofol on hepatic function are, however, a matter of controversy. Alpha-glutathione S-transferase (α-GST), a sensitive and specific biomarker for hepatic integrity, was measured to assess the influence of total intravenous anaesthesia (TIVA) with propofol vs. anaesthesia with desflurane.

Methods: Forty-two patients scheduled for elective prostatectomy were randomly allocated to receive either desflurane, fentanyl and thiopental (desflurane group) or propofol and remifentanil (TIVA group). Depth of anaesthesia was guided by bispectral index. Plasma concentrations of α-GST and aminotransferases were measured before induction of anaesthesia (T0), at the end of surgery (T1), as well as 2 h (T2) and 24 h (T3) postoperatively. Haemodynamic parameters and bispectral index values were documented.

Results: α-GST increased significantly in the desflurane group from T0 (3.0 ± 2.2 μg L−1) to T1 and T2 (5.5 ± 4.3 and 5.6 ± 3.7 μg L−1, respectively), whereas no changes were seen in the TIVA group. α-GST values above the normal upper limit (>7.5 μg L−1) were seen in 24% of the patients receiving desflurane. Aminotransferases remained unchanged in both groups throughout the study period.

Conclusions: The use of propofol as part of a TIVA regimen seems to have no influence on hepatocellular function during and after surgery. In contrast, patients receiving desflurane showed a transient slight, but significant, increase of α-GST to above the normal upper limit after anaesthesia, although this was without further clinical relevance.

Summary

Background and objective: It has been shown that racemic ketamine increases coronary blood flow and that this effect is at least in part due to a direct vasorelaxing effect of this substance. This study was designed to determine whether ketamine might stereoselectively relax isolated porcine coronary arteries.

Methods: Using the model of isolated vessels we studied the effects of S(+) ketamine, R(−) ketamine, and racemic ketamine (5–500 μg mL−1) on artery strips pre-contracted by either potassium chloride (KCl) or prostaglandin F2α (PGF2α). To elucidate possible mechanisms of action these experiments were repeated in the presence of one of the following compounds: Nω-nitro-l-arginine (l-NNA), indomethacin, glibenclamide, and tetraethylammonium (TEA) chloride, an inhibitor of the BKCa K+ channel.

Results: Both isoforms and racemic ketamine relaxed isolated coronary arteries in a concentration-dependent manner in concentrations beyond those used in clinical practice. S(+) ketamine exerted the strongest vasorelaxing effect, followed by racemic ketamine and R(−) ketamine. Pretreatment with l-NNA, indomethacin, or glibenclamide did not alter the vasodilating properties of ketamine, whereas TEA chloride significantly attenuated the vasorelaxing effects of all the three forms of ketamine.

Conclusions: Ketamine dilates coronary arteries in vitro when administered in high concentrations. There is a stereoselective difference with a stronger vasorelaxing effect of S(+) ketamine compared to racemic and R(−) ketamine. The impact of TEA chloride suggests that the activation of the BKCa channel may contribute to the vasodilating effect of ketamine.

Summary

Background and objective: This study was conducted to determine the effect of ketamine on metabolic homoeostasis and particularly in lipoprotein lipase (LPL) activity in adipose tissue.

Methods: Sixty male Wistar rats were divided into six groups of 10 each. Group A served as controls, while Groups B–F received, respectively, ketamine 60, 80, 100, 120 and 140 mg kg−1 intraperitoneally. The animals were sacrificed 20 min after the administration of ketamine. Insulin concentrations in plasma and total cholesterol, triglyceride, high-density lipoprotein (HDL) and free fatty acid (FFA) concentrations in serum were measured. LPL activity in adipose tissue and medium-chain acyl-CoA dehydrogenase (MCAD) content in muscle were determined.

Results: FFA concentrations in serum significantly increased from the second lowest dose of ketamine. Insulin concentrations in plasma did not exhibit any significant difference between groups. MCAD levels were 0.5-fold more in Group F than in Group A, while there were no significant differences between control group and Groups B–E. Furthermore, high concentrations (120 and 140 mg kg−1) of ketamine interfered with in metabolic homoeostasis by significantly reducing LPL activity, thus elevating triglyceride concentrations in serum without affecting cholesterol and HDL metabolism.

Conclusions: Ketamine induces various metabolic effects due to changes in adipose LPL activity and MCAD levels in muscles. These findings seem to be significant only at high doses.

Summary

Background and objective: Anaesthetic drugs and procedures interfere with secondary brain injury following severe head trauma, yet studies regarding the anaesthetic management of these patients are lacking. We investigated the behaviour of Italian anaesthetists regarding this topic.

Methods: A questionnaire investigating the approach to a patient with severe head trauma requiring an urgent splenectomy for ruptured spleen was sent to 250 Italian anaesthetists. Questions regarded the pre-, intra- and postoperative phases, and concerned the rationale use and availability of specific monitoring systems, and indications for invasive procedures and use of drugs, fluids and blood products.

Results: There were 162 (64.8%) responders. Seventy-five percent believed that early tracheal intubation within the emergency room was necessary, while 25% postponed it to the operating room. Basic monitoring was defined as essential by all responders, 147 (90.7%) considered invasive arterial pressure monitoring to be essential. Fifty-seven (84%) anaesthetists working in hospitals without neurosurgical facilities would have transferred the patient after splenectomy. Prophylactic hyperventilation was frequently used (36%). Sixty-eight percent of responders would have preferred in intracranial pressure monitoring inserted before laparotomy, but only 35% actually had this possibility. In case of acute intraoperative arterial hypotension after splenectomy, 54% of the responders advocated the use of blood or blood products to optimize peripheral oxygen transport.

Conclusions: More widespread knowledge of certain areas of severe head trauma management such as early tracheal intubation, avoidance of prophylactic hyperventilation, adequate invasive monitoring, appropriate use of blood products, and timing of transfer to hospitals with neurosurgical facilities is needed.