bluuebunny/crossref_metadata_2025 huggingface dataset:
Pharmacokinetics of scopolamine during caesarean section: relationship between serum concentration and effect
Authors: Kanto J. , Kentala E. , Kaila T. , Pihlajamaki K.
Published: January 2009

The pharmacokinetics (radioreceptor assay, RRA) and some of the clinical effects of the anticholinergic agent, scopolamine, were studied in 16 parturients during caesarean section. Following a single 0.005 mg/kg intramuscular injection (deltoid muscle), a very fast rate of absorption was found with mean peak serum concentrations occurring after only 10 min (n=6). Due to severe bradycardia, 0.5 mg of atropine i.v. had to be given in addition to the i.m. scopolamine treatment to one parturient. The RRA measured the total concentration produced by the two anticholinergic agents in both serum and urine. There was a fundamental difference in the diffusion of scopolamine through the placenta and the blood‐lumbar CSF‐barrier (n=15). There was significant drug penetration in the foeto‐placental unit, indicating an efficient drug transfer to the child, but there were measurable levels of the drug in the lumbar CSF in only three cases. The apparent elimination phase half‐life of scopolamine in serum was only around 1 h. The urinary excretion of scopolamine and/or its antimuscarinic metabolites lasted only for 6 h (2.63 ± 1.14% of the dose). The onset of the clinical effects of scopolamine appeared to be delayed, but long‐lasting in contrast to the rapid absorption and quick disappearance from the serum. Both the heart rate changes, sedative and antisialogogue effects and serum concentrations did not show any correlation. There appears to be a surprisingly great difference between the pharmacokinetic parameters and the clinical effects of scopolamine.
Effect of sternotomy and cardiopulmonary bypass on airway pressures and respiratory mechanics during high frequency ventilation
Authors: Harris C. E. , Cody M. , Chakrabarti M. K. , Whitwam J. G.
Published: January 2009

The airway pressures at ventilatory frequencies of 15, 60, 100, 120 and 150 breaths per minute were measured in eight adult patients undergoing coronary artery bypass grafting. Measurements were made perioperatively at four stages: precardiopulmonary bypass with the chest closed, precardiopulmonary bypass with the chest open, postcardiopulmonary bypass with the chest open and postcardiopulmonary bypass with the chest closed. In five patients thoracic compliance and airways resistance were also measured at these times. Neither sternotomy nor cardiopulmonary bypass made any significant difference to the airway pressures during normal and high frequency ventilation, nor were lung mechanics affected.
Estimating allowable blood loss with correction for variations in blood volume
Authors: Hahn R. G.
Published: January 2009

All the theoretical relationships between blood loss and change in haematocrit used for calculating the allowable pre‐transfusion blood loss assume a strictly normovolaemic situation. In this study a formula was derived in which account was taken of the variation in blood volume. The formula was based on clinical data. Measurements of the blood loss, the blood haemoglobin concentration and the haematocrit (HCT) were performed on 230 occasions in the course of 35 transurethral prostatic resections. The change in blood volume was estimated by the haemoglobin dilution method and the value so obtained was compared to both the measured haematocrit and the theoretical value that would presumably have been recorded if there had been no change in blood volume. The relationship established from these comparisons was: blood loss = preoperative blood volume × [In preop HCT – In postop HCT (1+ 0.15 × blood volume change)]
Rectal induction of anaesthesia in children
Authors: Holm‐Knudsen R. , Nygård E. , Laub M.
Published: January 2009

Thirty children were randomly allocated to one of three anaesthetic techniques. Rectal anaesthesia induction with a mixture of ketamine 10 mg · kg‐1 BW and midazolam 0.2 mg · kg‐1 BW and maintenance of anaesthesia with either intravenous ketamine or halothane were compared to induction and maintenance with halothane. Rectal induction was found reliable and useful. The frequency of side effects, the recovery time, and the time until the child could be discharged were similar in the groups maintained with halothane, whereas recovery was prolonged when intravenous ketamine was used for maintenance.
Lung function during anesthesia and respiratory insufficiency in the postoperative period: physiological and clinical implications
Authors: Schwieger I. , Gamulin Z. , Suter P. M.
Published: January 2009

This review covers the physiological and clinical implications of lung function during anesthesia and respiratory insufficiency in the postoperative period. We have divided it into 3 main sections: 1) lung function changes induced by anesthesia and surgery, in which the impact on pulmonary mechanics, ventilation/perfusion changes and gas exchange are examined; 2) physiological implications of postoperative respiratory function secondary to decreased alveolar ventilation, development of atelectasis, and interstitial lung edema; and 3) clinical implications of postoperative respiratory failure. In this last section we analyze the current therapeutic modalities available to reduce the incidence of postoperative respiratory failure, as well as related morbidity and mortality.
Comparison of the effects of continuous intrapleural vs epidural administration of 0.5 % bupivacaine on pain, metabolic response and pulmonary function following cholecystectomy
Authors: Scott N. B. , Mogensen T. , Bigler D. , Kehlet H.
Published: January 2009

Twenty patients undergoing elective cholecystectomy were prospectively randomised to receive either intrapleural (bolus 20 ml followed by 10 ml/h) or thoracic epidural (bolus 9 ml followed by 5 ml/h) bupivacaine 0.5% for 8 h postoperatively to assess the effect of these two techniques on pain, pulmonary function and the surgical stress response. As assessed by the visual analogue scale (VAS), both groups received good but not total pain relief. Both groups had a 50% reduction in forced expiratory volume (FEV1), forced vital capacity (FVC) and peak expiratory flow rate (PEFR) after operation, and there was no observed effect on the stress response as measured by plasma glucose and cortisol. It is concluded that while both techniques provide good analgesia, the degree and extent of nerve blockade are not sufficient to affect the afferent neurogenic stimuli responsible for the observed effects on pulmonary function and the stress response.
Comparison of thumb acceleration and thenar EMG in a pharmacodynamic study of alcuronium
Authors: Meretoja O. A. , Werner M. U. , Wirtavuori K. , Luosto T.
Published: January 2009

We compared thumb acceleration (Acc) and thenar electromyography (EMG) techniques by evaluating the neuromuscular blocking properties of alcuronium in 14 ASA physical status I patients. The dose‐response curves determined by the two techniques were parallel but the EMG‐curve was shifted 25% to the right (P<0.001). Acc reflected 8–11% greater neuromuscular block than simultaneous EMG in every patient (P<0.05). Concurrently, the duration of >90% neuromuscular block maintained by alcuronium 280 μg/kg was significantly longer when measured by the Acc transducer (30 vs. 19 min, P<0.001). Although the TOF ratios were in good correlation (r2=0.82), clinically significant differences existed between the two simultaneous techniques. The results underline the importance of the method of assessment of neuromuscular transmission when evaluating the action of neuromuscular blocking drugs.
Thiopentone pharmacokinetics during cardiopulmonary bypass with a nonpulsatile or pulsatile flow
Authors: Hynynen M. , Olkkola K. T. , Näveri E. , Palojoki R. , Neuvonen P. J. , Heinonen J.
Published: January 2009

To evaluate possible factors affecting the pharmacokinetics of thiopentone during cardiopulmonary bypass (CPB), the present study was undertaken in patients scheduled for coronary artery bypass grafting and with in vitro experiments. The effects of nonpulsatile and pulsatile flow during CPB on the distribution and elimination of thiopentone were compared in 30 patients anaesthetized with fentanyl. The initial rapid phases of distribution of thiopentone were studied in 17 patients undergoing a nonpulsatile or pulsatile perfusion, to whom thiopentone 6 mg/kg was given as a rapid intravenous bolus during CPB. In order to study later distribution and early elimination of thiopentone, 13 patients perfused with a nonpulsatile or pulsatile flow received 6 mg/kg of the drug as a 15‐min intravenous infusion before CPB. No differences in the pharmacokinetic parameters characterizing distribution and elimination of thiopentone were found between the patients undergoing nonpulsatile or pulsatile perfusion. As measured in 10 of the patients receiving the drug before the institution of CPB, no difference in plasma thiopentone level was observed in blood samples drawn simultaneously from a radial arterial cannula and a pulmonary artery catheter before, during and after CPB. This suggests that thiopentone is not sequestered in lungs during CPB. In vitro binding of thiopentone to the CPB equipment was studied in 6 experiments using a closed circuit. After a 60‐min circulation time, only 50% of the predicted thiopentone level was recovered from the perfusate. It is concluded that replacing a nonpulsatile perfusion with a pulsatile one has no effect on the distribution and elimination of thiopentone in patients undergoing CPB. During CPB, thiopentone is sequestered in the extracorporeal circuit but not in the lungs.
Displacement of warfarin from human serum proteins by halothane anaesthesia
Authors: Calvo R. , Aguilera L. , Suárez E. , Rodriguez‐Sasiaín J. M.
Published: January 2009

The in vitro effects of the halothane metabolite, trifluoroacetic acid, on the binding of warfarin to human serum proteins have been investigated. An increase in the percentage of free warfarin following incubation with different concentrations of trifluoroacetic acid (1 and 4 mmol/l) was observed. In addition, protein binding of warfarin was studied in serum from patients undergoing halothane anaesthesia (1–2.5%; 2.5 h). After 24 h from the end of the halothane anaesthesia, an increase in the percentage of free warfarin was also detected (0.92 ± 0.06% at 24 h vs 0.60 ± 0.02% before halothane administration; P < 0.005). We conclude that halothane anaesthesia may temporarily potentiate the pharmacological effect of warfarin in the post‐operative period following anaesthetic procedures.
Coagulation and fibrinolytic parameters in patients undergoing total hip replacement: influence of the anaesthesia technique
Authors: Donadoni R. , Baele G. , Devulder J. , Rolly G.
Published: January 2009

Eighty patients undergoing total hip replacement (THR) were randomly allocated to three groups. Group I (n=29) received general anaesthesia, Group II (n=29) epidural anaesthesia and Group III (n=22) the same epidural as Group II and the same general anaesthesia as Group I but with a lower isoflurane concentration. Prothrombin time (PT), activated thromboplastin time (APTT), fibrinogen (FG), plasminogen (PG), antithrombin III (AT III), protein C (Proc C), α‐2‐antiplasmin (α2 AP), Factor VIII coagulating activity (F VIII: C), von Willebrand factor antigen (vWF:Ag), von Willebrand ristocetin cofactor (vWF: Rcof), tissue plasminogen activator (tPA) as antigen and activity were measured before induction (A), at the end of surgery (B), on the first postoperative morning (C) and 7 days postoperatively (D). The most relevant finding was that AT III was equally depressed immediately after surgery in all groups, but returned to normal significantly faster in the epidural group (mean values at C: 96.2% in Group I, 104.1% in Group II, 92.7% in Group III). The faster return to normal of AT III after epidural anaesthesia could be one of the mechanisms responsible for the beneficial effect of this technique on the prevention of thromboembolic complications.
Single dose oral H2‐antagonists do not affect plasma lidocaine levels in the parturient
Authors: Flynn R. J. , Moore J. , Collier P. S. , Howard P. J.
Published: January 2009

We studied whether a single oral dose of either cimetidine or ranitidine affects the disposition of epidurally administered lidocaine in the parturient. Patients given epidural analgesia for elective caesarean section were randomly pretreated with either cimetidine 400 mg (n=5), ranitidine 150 mg (n=7) or no H2 receptor antagonist (n=5). Following the administration of 400 mg of lidocaine 2% with adrenaline 1:200 000 no difference was found in peak plasma lidocaine levels or area under the plasma concentration/time curve (AUC) between the three groups. A single oral dose of cimetidine or ranitidine does not affect lidocaine disposition in the obstetric patient.
Increased microvascular permeability caused by toxic oxygen metabolites is partly reversed by exchanging the perfusate in isolated rat lungs
Authors: Kjæve J. , Vaage J. , Bjertnæs L.
Published: January 2009

Toxic oxygen metabolites (TOM) released from stimulated phagocytes and lung tissue have been shown to injure the pulmonary microcirculation. In the present study we evaluated microvascular injury caused by TOM in rat lungs perfused with plasma. The injury, as indicated by an increase in vascular permeability, was assessed by determining the fluid filtration rate (FFR) after paralysing the pulmonary vascular bed with papaverine (0.1 mg/ml). TOM were generated by adding xanthine oxidase (XO) (0.05–0.125 U/ml) and hypoxanthine (HX) (1 mmol/l) to the perfusate. FFR was measured before, 30 and 60 min after addition of XO and HX. The following interventions were done: 1. the H2O2‐scavenger catalase, 2. substitution of the perfusate after 30 min, 3. BW 755 C, a combined lipoxygenase and cyclooxygenase inhibitor, and 4. indomethacin, a cyclooxygenase inhibitor. Addition of XO and HX caused FFR to increase from 14 ± 4 mg/min (mean ± s.e. mean) at the onset to 56 ± 7 mg/min and 86 ± 10 mg/min after 30 and 60 min, respectively. Replacing the perfusate with fresh plasma after 30 min caused a significant reduction in FFR at 60 min, from 86 ± 11 mg/min to 58 ± 10 mg/min. Catalase prevented the increase in FFR. Indomethacin and BW 755 C had no effect on the increase in FFR. We conclude that TOM induced a partly reversible increase in microvascular permeability of isolated rat lungs. From previous studies, the activity of XO was expected to cease after 30 min. Therefore it is suggested that secondary products of TOM propagate the lung injury. The increase in permeability was not mediated by arachidonic acid metabolites.
Continuous conjunctival oxygen tension (Pcjo2) monitoring for assessment of cerebral oxygenation and metabolism during carotid artery surgery
Authors: Haljamae H. , Frid I. , Holm J. , Holm S.
Published: January 2009

The clinical value of noninvasive continuous monitoring of conjunctival oxygen tension for assessment of cerebral perfusion during carotid endarterectomy performed under general anaesthesia has been evaluated. The patients (n= 17; mean age 62.5 ± 1.7 years) were monitored as follows: conjunctival oxygen tension (Pcjo2); internal jugular venous oxygen tension at the skull base level (Pcijvo2); arterial blood pressure; arterial and internal jugular venous blood gases; acid‐base data and lactate, pyruvate levels; end‐tidal CO2 concentration. The mean preanaesthetic Pcjo2 level of 4.86 ± 0.40 kPa was significantly lower than Pao2(Pcjo2)/Pao2 ratio of 0.48). Following anaesthesia, a larger Pcjo2–Pao2 gradient (ratio 0.32) was seen in spite of the hyperoxic situation (Fio2 = 0.40) due to vasoconstriction induced by slight hypocapnia (reduction of Paco2 from 5.13 ± 0.08 to 4.64 ± 0.10 kPa). The carotid artery crossclamping resulted in a rapid and pronounced decrease of Pcjo2 while Pcijvo2 remained unchanged. No relationship between Pcjo2 and stump pressure was found, while a significant correlation (P<0.02) between Pcjo2 and lactate in effluent venous blood from the brain was demonstrable. It is concluded that Pcjo2 monitoring seems a clinically useful trend indicator of cerebral perfusion in the individual patient. Due to large interindividual variations in basal Pcjo2 readings and in Pcjo2 changes during carotid artery clamping, however, transconjunctival oxygen tension monitoring does not seem to allow early and accurate recognition of impending cerebral ischaemia during carotid endarterectomy, and its routine use therefore seems of limited value.
True shunt in relation to venous admixture in an experimental porcine model of early ARDS
Authors: Forsgren P. , Jakobson S. , Modig J.
Published: January 2009

Using the multiple inert gas elimination technique, ventilation/perfusion (V/Q) relationships were studied in an experimental porcine model of the early Adult Respiratory Distress Syndrome (ARDS) to establish the nature of the increased venous admixture. Six animals served as controls and revealed no major changes apart from a 10% decrease in cardiac output during the 4‐h observation period. All control animals showed a shift to a higher mean V/Q of perfusion (Qmean) and a maintained log standard deviation (Qsd) throughout the experiment. The distribution was unimodal and centered around a V/Q ratio of 1.0. The share of perfusion to V/Q ratio < 0.005 (i.e. true shunt, Q) remained unchanged at 6–7% of cardiac output. Nine animals, given a continuous infusion of E. coil endotoxin, showed a significant decrease of 53% in cardiac output (Q) at 4 h. Mean pulmonary artery pressure (MPAP) showed a 2‐phase reaction with a peak level at 0.5 h, and a second gradual increase from 2 h onwards. Venous admixture doubled at 0.5 h, after which it declined but remained elevated throughout the observation period. All endotoxin animals showed a shift in perfusion to a higher Qmean with a significantly wider Qsd at 0.5, 2 and 4 h. The distribution was unimodal and centered around a V/Q ratio of 1.0. True shunt was unchanged at 6–7% of cardiac output throughout the study. The increase in venous admixture in this experimental ARDS model is consequently explained by the widening of the V/Q scatter and is due to a perfusion shift to lower ventilation/perfusion ratios rather than to an increase in true shunt.
Influence of the fluid balance on the cortisol and glucose responses to transurethral prostatic surgery
Authors: Hahn R. G.
Published: January 2009

The serum cortisol and blood glucose concentrations were followed for up to 2 h after 35 transurethral prostatic resections performed under epidural anaesthesia. No significant variation in either of these levels was recorded in connection with the seven operations during which there was no disturbance of the fluid balance, or the seven where there was elevation in the central venous pressure indicative of intravenous fluid overload. In contrast, both the serum cortisol and the blood glucose level showed a significant increase in the nine patients with a blood loss of more than 800 ml, and in the nine recording absorption of irrigant in excess of 300 ml and immediate development of hyponatraemia. On the other hand, this response did not occur in the three patients with irrigant absorption where hyponatraemia developed with a delay of at least 20 min. These results suggest that the effect of surgery on the serum cortisol and blood glucose levels may be modified by disturbances of the fluid balance developing in the course of the operation.
The cerebral arterio‐venous oxygen content differences (AVDo2) during halothane and neurolept anaesthesia in patients subjected to craniotomy
Authors: Engberg M. , ØBerg B. , Christensen K. S. , Pedersen M. Bach , Cold G. E.
Published: January 2009

In 20 patients subjected to craniotomy for supratentorial cerebral tumours, the haemodynamic changes during halothane and neurolept anaesthesia were evaluated by measuring mean arterial blood pressure (MABP) and cerebral arterio‐venous oxygen content differences (AVDo2) repeatedly during the operation. Ten patients were given 0.5% halothane anaesthesia and ten patients neurolept anaesthesia. MABP, AVDo2 and Paco2 were measured after induction of anaesthesia, before and after incision, after opening and closure of the dura, at the time of extubation and 1 h later. Concerning MABP and Paco2, no significant difference between the two groups was found. In both groups an increase in MABP was observed after incision (P<0.01 in the neurolept group and P<0.05 in the halothane group) and in the neurolept group after extubation (P<0.01). In both groups a decrease in AVDo2 was observed after incision (P<0.01) and after extubation (P<0.01 in the neurolept group and P<0.05 in the halothane group). During the operation AVDo2 values were significantly higher in the neurolept group (P<0.05). The results indicate that even a moderate increase in MABP after incision during neuroanaesthesia affects AVDo2 values, suggesting an increase in cerebral blood flow. The study suggests that autoregulation of cerebral blood flow might be better preserved during neurolept anaesthesia. A state of hyperperfusion of the brain after extubation was unveiled in both groups.
Changes in the arterial to end‐tidal Pco2 differences during coronary artery bypass grafting
Authors: Fletcher R. , Veintemilla F.
Published: January 2009

The arterial to end‐tidal Pco2 difference, Paco2‐Pe,co2, was measured at four different stages during coronary artery bypass grafting in 43 patients: 1) before sternotomy; 2) after sternotomy, sternum retracted; 3) after bypass, sternum still retracted; 4) sternum closed. Mean Paco2‐Pe,co2 initially was 0.6 kPa and changed scarcely at all during the procedure. There were, however, some moderate individual changes in Paco2 — Pe,co2 during surgery, the range of changes compared to the initial value being from — 1.4 to + 1.3 kPa. The standard deviations for the changes from stage to stage were 0.3–0.4 kPa. Paco2 — Pe,co2 changed by more than 0.5 kPa on only 12 occasions in ten patients. The limitations of Paco2 — Pe,co2 as an index of the alveolar deadspace fraction and the efficiency of ventilation are discussed.
Relationship between changes in power spectra of electroencephalograms and arterial halothane concentration in infants
Authors: Sugiyama K. , Joh S. , Hirota Y. , Kiyomitsu Y. , Shibutani T. , Niwa H. , Matsuura H.
Published: January 2009

A power spectral analysis of electroencephalograms (EEGs) was performed in 30 infants who underwent plastic surgery for cleft lip or cleft palate. The study was conducted to investigate whether there was a significant correlation between EEG changes and arterial halothane concentration in infants. The power spectral analysis of EEGs was performed by the fast Fourier transform (FFT). Arterial halothane concentration was measured with gas chromatography. The relationship between the changes in the power spectra of EEGs and the arterial halothane concentration was examined by means of a multivariate analysis. Prior to administration of halothane, two kinds of EEG patterns were discernible. In one pattern the peak of the EEG power spectra was seen in the slow wave band (slow wave group); in the other the peak of the power spectra was present in the fast wave band (fast wave group). In the occipital lead the multiple correlation coefficient and the index of determination of the slow wave group were 0.71 and 0.50, respectively, and those of the fast wave group were 0.78 and 0.61, respectively. A significant correlation was proved to be present between the normalized values of the EEG power spectra and arterial halothane concentration in the occipital lead. Therefore, the results of the present study suggest that the relationship between changes in the power spectra of EEGs in the occipital lead and arterial halothane concentration in infants can be expressed by means of multiple regression formulas.
Induction and recovery characteristics of propofol, thiopental and etomidate
Authors: Boysen K. , Sanchez R. , Krintel J. J. , Hansen M. , Haar P. M. , Dyrberg V.
Published: January 2009

Propofol, thiopental and etomidate, with 20 patients in each group, were compared for anesthesia of short duration in women undergoing termination of pregnancy, with respect to: 1: pain on injection (equally often after propofol and etomidate, but more rarely after thiopental); 2: apnea following induction (no difference); 3: involuntary muscular movements (more frequent after etomidate); 4: blood pressure (larger drop after propofol); 5: heart rate (greater increase after thiopental); 6: time to eye opening on command (longer after propofol); 7: Steward score on eye opening (no difference); 8: coin counting after 15, 30 and 60 min (performance better after propofol at 15 and 30 min, producing even shorter times than preoperatively at 60 min); 9: reaction time after 15, 30 and 60 min (performance better after propofol, producing even shorter times than preoperatively at 60 min). It is concluded that the faster recovery gives propofol an advantage over thiopental and etomidate in outpatient anesthesia.
Pulmonary gas exchange in panting dogs: a model for high frequency ventilation
Authors: MEYER MICHAEL , HAHN GÜNTER , PIIPER JOHANNES
Published: January 2009

Panting in animals can be expected to represent a naturally occurring physiological counterpart to today's techniques of mechanical high‐frequency ventilation. To analyze the mechanisms underlying the gas exchange inefficiency during ventilation with high frequencies, steady‐state pulmonary gas exchange was studied in seven conscious dogs (32 kg mean body weight) during panting elicited by mild thermal stress. The animals had a chronic tracheostomy and an exteriorized carotid artery loop and were exposed to 27.5°C ambient temperature for 2 h (65% relative humidity). Open‐circuit techniques were used and Po2 and Pco2 from the tracheostomy tube were continuously monitored by mass spectrometry using a special sample‐hold phase‐locked gas sampling technique. Po2 and Pco2 were determined in arterial blood collected from the carotid artery. During the exposure, the following variables of steady‐state gas exchange were determined (means ±SD): breathing frequency 313 ±19 min‐1; tidal volume, 167 ± 21 ml; total ventilation, 52 ± 9 1‐min‐1′ effective alveolar ventilation, 5.5± 1.3 1‐min‐1; partial pressures (torr; a, arterial; E', end‐tidal): Pao2, 106.2 ± 5.9; Paco2, 27.2 ± 3.9; (PE'‐Pa)o2, 26.0 ± 5.3; (Pa‐PE')co2, 14.9 ± 2.5. According to the conventional lung model, parallel‐dead space ventilation (ventilation of unperfused lung regions) would account for about 55% of the alveolar ventilation and for 2/3 of the (PE'‐Pa)o2 difference. However, the lack of an ‘alveolar plateau’ in the CO2 and O2 expirograms suggests that incomplete serial mixing in peripheral airways contributes to the enhanced gas exchange inefficiency during panting as reflected in the increased blood/gas differences for O2 and CO2.
Biodynamic behavior of the trunk and the abdomen during whole‐body vibration
Authors: DUPUIS HEINRICH
Published: January 2009

Vibration strain may be defined as the sum of all reactions of the human being to vibration exposure. This also includes the biomechanical behavior of particular parts of the body. Knowledge about these reactions is necessary in the field of occupational health and ergonomics. Biomechanical models, experimental methods, and results are presented. It can be shown that under vibration exposure with different conditions (body posture, vibration direction), the body parts are in resonance at varying frequencies, mainly in a low frequency range.
Mechanics of the respiratory system during high frequency ventilation
Authors: FREDBERG J. J. , ALLEN J. , TSUDA A. , BOYNTON B. , BANZETT R. , BUTLER J. , LEHR J. , FRANTZ I. D.
Published: January 2009

No rational approach has evolved for selecting operating conditions for clinical application of high‐frequency ventilation (HFV). To this end, we divide our discussion of HFV into considerations of mechanics versus transport, and treat the latter as a constraint. After describing some of the phenomena that influence distending pressure (and its distribution) expressed across pulmonary tissues, we address the pressure costs per unit ventilation and the factors that influence them. This narrowly defined approach leads to some fundamental strategies, compromises, and dilemmas. In particular, consideration of the mechanical interaction of the lung and chest wall leads to a paradox, and points out that the influence of the chest wall upon phasic regional lung distension is not well understood.
Gas flow distribution and tidal volume during distal high frequency jet ventilation in dogs
Authors: TAMSMA T. J. A. , SPOELSTRA A. J. G.
Published: January 2009

During distal high frequency jet ventilation (HFJV) in anaesthetized healthy dogs gas flows were recorded at the proximal end of the open tracheal jet tube. Spirometer measurements of minute volumes with and without entrainment were made. During the inspiratory or insufflation period, leakage of jet gas (bypass) could occur depending on the ventilator setting. From the gas flow recordings and the spirometer measurements, jet‐, entrainment‐ and bypass minute volumes were determined. From these the effective minute volume, that is the minute volume of fresh gas entering the lungs, was calculated, as well as tidal volume. The results show that entrainment volumes are relatively small in an open system of distal HFJV and that at the same time bypass can (nearly) completely eliminate the effect of entrainment on tidal volume.
The ventilatory effect of external oscillation
Authors: ISABEY DANIEL , PIQUET JACQUES
Published: January 2009

High frequency ventilation (HFV) may be achieved by external oscillation (external HFV) applied around the chest wall (HFCWO) in large animals and humans, or over the entire body (HFBSO) in small animals, instead of being applied via the trachea (internal HFV). We present a synthesis of the results obtained with external HFV in both normal and bronchoconstricted subjects. Whereas external and internal HFV were found to be equivalent in terms of gas exchange in normal rats, external HFV was found to have a beneficial effect in bronchoconstricted rabbits, but internal HFV did not. From the frequency‐oscillatory tidal volume relationship determined in normocapnic rabbits, HFBSO at 5 Hz was found to be the optimal frequency at which to ventilate with tidal volumes close to the dead space volume, and which was also shown to be the optimal volume to obtain normocapnia. Moreover, 5 Hz oscillations (HFCWO) at 20 ml and 40 ml superimposed on tidal breathing accelerated nitrogen washout, i.e., gas exchange in normal humans. Unfortunately, only oscillations with much smaller volumes (5–10 ml) were obtainable in COPD patients. Nevertheless, they produced a clear change in breathing pattern associated with a slight improvement in gas exchange and a potentially positive effect on inspiratory muscle fatigue. These results support the concept that non‐invasive external HFV technique may be of use in assisting ventilation in bronchoconstricted subjects and may possibly replace conventional controlled ventilation, at least in subjects with high lung compliance, such as babies, neonates and normal adults.
A comparison of ventilation strategies for the use of high‐frequency oscillatory ventilation in the treatment of hyaline membrane disease
Authors: DELEMOS R. A. , COALSON J. J. , MEREDITH K. S. , GERSTMANN D. R. , NULL D. M.
Published: January 2009

To assess the efficacy of high frequency oscillatory ventilation (HFOV) in the management of infants with hyaline membrane disease (HMD), we compared two HFOV strategies with conventional positive pressure ventilation with positive end expiratory pressure (PPV) for 24 h in premature baboons (140 d gestation). Three out of 14 PPV, five out of five HFOV‐E (begun at birth; 15 Hz; I:E 1:2), and none of 10 HFOV‐L (begun after 3 h PPV; 10 Hz; I:E 1:2) were killed at 24 h for morphologic examination. Physiologic (Paw, Pa/AO2, IO2, B. P., pulse, blood gases) data on all animals in each group were assessed at each 3 h interval and over time. Intergroup differences in radiographs at 0 and 24 h and in morphology were quantitatively assessed by comparison with a panel of standards. All animals had radiographic HMD. Initial Paw was set higher with HFOV‐E (16.8) than PPV or HFOV‐L (14.1, 14.1). PPV baboons required increasing Paw to maintain constant Pa/AO2. Six out of 14 PPV animals developed airleak and three out of three had morphologic HMD. In contrast Pa/AO2 was higher in both HFOV groups at lower Paw by 24 h. None of 15 HFOV animals developed airleak. HFOV‐E lungs had dramatic differences in morphology with uniform saccular opening and decreased edema and hyaline membranes compared to PPV. HFOV‐L had less dramatic effects because of lower Paw and delayed application. Early use of HFOV at a high Paw favorably alters the course of HMD. Unless closely monitored, this strategy results in lung overinflation which may adversely affect venous return and cardiac output.
Indications for combined high frequency ventilation in clinical use
Authors: ZERAVIK J. , ECKART J. , ZIMMERMANN G. , BLÜMEL G. , PFEIFFER U. J. , WELLHÖFER H.
Published: January 2009

A retrospective study of 20 surgical intensive care unit patients is reported. They were ventilated with continuous positive pressure ventilation (CPPV) and then switched to combined high frequency ventilation (CHFV). To find why there were variable responses to CHFV, the data of 20 patients were retrospectively evaluated with respect to respiratory index (RI), compliance (C) and extravascular lung water (EVIAV). The results suggest that the indication line for CHFV was a C value > 45 ml/cmH2O and an EVLW value > 15 ml/kg BW.
Effects of thoracic epidural anaesthesia on central haemodynamics compared to cardiac beta adrenoceptor blockade in conscious rats with acute myocardial infarction
Authors: Blomberg S. , Ricksten S‐E.
Published: January 2009

The study aimed to compare the effects of thoracic epidural anaesthesia (TEA) with those of the beta‐adrenoceptor blocker, metoprolol, on central haemodynamics in conscious rats with acute myocardial infarction. During methohexital anaesthesia, appropriate vascular catheters were inserted, a thoracic epidural catheter was implanted and the left coronary artery was ligated. A recovery period of 1–2 h elapsed after termination of surgery and anaesthesia. Experiments were performed on four separate groups of animals (A‐D). In Group A (n= 10) mean arterial pressure (MAP), heart rate (HR), and cardiac output (CO) were measured, and stroke volume (SV) and systemic vascular resistance (SVR) were calculated before and 10–15 min after the induction of TEA (bupivacaine 5 mg · ml‐1). In Group B (n=6) left ventricular end‐diastolic pressure (LVEDP) and maximal dP/dt were recorded as in Group A. In Group C (n = 10) central haemodynamics were measured 10 min after i.v. metoprolol (0.5 mg · kg‐1) and again 10–15 min after the addition of TEA. In Group D (n=6) LVEDP and max dP/dt were measured as in Group C. The reduction in CO, SV, HR and max dP/dt was of the same magnitude with TEA and metoprolol. TEA lowered MAP by 17%, while metoprolol did not change MAP. Metoprolol caused an increase in LVEDP from 20.8 ± 1.8 to 27.5 ± 2.7 mmHg (2.8 ± 0.2 to 3.7 ± 0.4 kPa) (P < 0.01), while TEA induced a decrease in LVEDP from 24.2 ± 1.4 to 17.8 ± 1.6 mmHg (3.2 ± 0.2 to 2.4 ± 0.2 kPa) (P < 0.05). SVR increased 27% with metoprolol but was not affected by TEA. Induction of TEA during maximal beta blockade did not cause any further changes in CO, HR, max dP/dt or SV. In this situation, however, MAP and SVR decreased significantly by 23% and 19%, respectively, and LVEDP decreased from 27.5 ± 2.7 to 20.2 ± 2.3 mmHg (3.7 ± 0.4 to 2.7 ± 0.3 kPa) (P < 0.01). Compared to metoprolol, TEA may have more favourable effects on central haemodynamics during acute myocardial infarction, as, in striking contrast to metoprolol, TEA decreased indices of wall tension and outflow impedance of the left ventricle.
Does ephedrine influence newborn neurobehavioural responses and spectral EEG when used to prevent maternal hypotension during caesarean section?
Authors: Kangas‐Saarela T. , Hollmén A. I. , Tolonen U. , Eskelinen P. , Alahuhta S. , Jouppila R. , Kivelä A. , Huttunen P.
Published: January 2009

The recovery of 16 infants born by elective caesarean section with spinal anaesthesia, in which either ephedrine or fluid load was used to prevent maternal hypotension, were studied using Scanlon's neurobehavioural tests and a computerized EEG. Neurobehavioural testing showed no differences between the ephedrine and the non‐ephedrine groups of infants at ages of 3 h, 1 day, 2 days and 4–5 days, whereas the spectral EEG showed significant differences between the two groups during the first 2 h after delivery, which had disappeared 24 h later. It is suggested that small doses of ephedrine given to the mother i.v. to prevent hypotension during spinal anaesthesia have short‐lived effects on the neonate's central nervous system, which will be detected in the spectral EEG, but not in neurobehavioural tests.
Anticholinergic premedication in Finland 1988
Authors: Kentala E. , Salonen M. , Kanto J.
Published: January 2009

In order to investigate the present use of anticholinergic drugs in premedication, a questionnaire was sent to Finnish anaesthesiologists. The results indicate that there is significant variation between different parts of the country regarding the usage of these drugs. A decrease in routine use has taken place over the past 5 years. Half of the anaesthesiologists now routinely use anticholinergic drugs in premedication, while 69% were using them 5 years ago. Glycopyrrolate has gained popularity and was the most used drug. Most anaesthesiologists gave the anticholinergic premedication intravenously, briefly before induction.
Analgesia for appendectomy: comparison of fentanyl and alfentanil in children
Authors: Sfez M. , Mapihan Y. Le , Gaillard J. L. , Rosemblatt J. M.
Published: January 2009

During etomidate‐N2O vecuronium anaesthesia for appendectomy, three groups of 13 children received fentanyl as a 10 μg · kg‐1 loading dose and 2 μg · kg‐1 increments in Group F, alfentanil as a 100 μg · kg‐1 initial loading dose and either 20 μg · kg‐1 increments in Group AB or 1 μg · kg‐1 · min‐1 continuous infusion in Group AI. On the basis of intraoperative heart rate changes, the opioid regimen was less efficient in Group AB (P < 0.05). Based upon equianalgesic cumulative dosage, the alfentanil/fentanyl potency ratio was in the range of 1/10 to 1/13. The awakening time was similar in all groups, as were the duration of postoperative analgesia, the incidence of postoperative pain and the incidence of nausea and vomiting. We conclude that high‐dose alfentanil is as efficient as fentanyl for intra and postoperative analgesia in children undergoing appendectomy.
Circulatory monitoring of children during anaesthesia in low field magnetic resonance imaging
Authors: Selldén H. , de Chateau P. , Ekman G. , Linder B. , Sääf J. , Wahlund L‐O.
Published: January 2009

Anaesthesia for patients in a Magnetic Resonance Imaging (MRI) scanner provides some problems for the design of both the anaesthetic and the monitoring equipment. This report presents a technique for continuously displaying the heart rate during anaesthesia for children in an MRI scanner. The monitoring system used light to detect differences in skin capillary circulation, and the light was transferred to and from the patient via fiberoptic cables. After amplification, the signal was displayed “on line” on a cardioscope, thus continuously presenting heart rate and, in part, a qualitative view of the skin vascular resistance.
Muscle relaxants change myocardial metabolism in patients with ischemic heart disease during high‐dose fentanyl anesthesia
Authors: Gilbert M. , Anderson E. A. , Bróndbo A. , Bjertnæs L. J.
Published: January 2009

Although not unanimously accepted, high‐dose fentanyl anesthesia has been associated with hemodynamic stability and little derangement of myocardial oxygen balance. This apparent inconsistency inspired us to investigate the effects on cardiac function and myocardial metabolism of stepwise increasing doses of fentanyl, accumulating to 15, 30, and 50 μg · kg‐1, with the least possible interference from other drugs. Subjects were unpremedicated patients with ischemic cardiac disease scheduled for coronary artery bypass grafting or major vascular surgery. In an initial study employing succinylcholine for muscle relaxation, we found that heart rate (HR), coronary sinus blood flow (CSF) and coronary vascular resistance (CVR) remained unchanged, while systemic arterial pressure (SBP), rate‐pressure product (RPP), coronary perfusion pressure (CPP) and left ventricular work (LVW) decreased. Myocardial uptake of oxygen (MVo2) and free fatty acids (FFA) both decreased in a dose‐dependent manner. Arterial lactate concentration and myocardial lactate uptake both increased. These findings opposed the postinduction myocardial ischemia noted by some other investigators. In most of these studies pancuronium bromide had been used for muscle relaxation. Since the latter agent has been claimed to increase cardiac work, a second group of correspondingly diseased patients was studied in which succinylcholine was replaced by pancuronium bromide. In this group HR, RPP, CSF and MVo2all increased at the lowest dose of fentanyl and HR additionally also at 30 μg · kg‐1. The cardiac index was higher in the pancuronium group at the lowest and middle dose steps of fentanyl. Lactate uptake decreased with higher doses of fentanyl and relative myocardial lactate extraction declined. These studies suggest that: 1) the conflicting reports on hemodynamic stability of high‐dose fentanyl may be due to the use of different relaxants; 2) fentanyl and succinylcholine may improve myocardial oxygen balance while fentanyl and pancuronium bromide may hamper this balance.
Epidural anesthesia for cesarean section in a patient with severe pulmonary hypertension
Authors: Atanassoff P. , Alon E. , Schmid E. R. , Pasch Th.
Published: January 2009

The case of a parturient previously operated on for transposition of the great arteries is reported. On account of Eisenmenger's syndrome with high pulmonary vascular pressures, she was admitted to hospital with hemoptysis in the 27th week of gestation. At the end of the 34th week the child was delivered by elective cesarean section under epidural block. Bupivacaine 0.75% was administered as local anesthetic, and small incremental doses of local anesthetic proved capable of maintaining hemodynamic stability for the duration of the operative procedure.
The effect on uteroplacental blood flow of epidural anaesthesia containing adrenaline for caesarean section
Authors: Skjöldebrand A. , Eklund J. , Lunell N‐O. , Nylund L. , Sarby B. , Thornström S.
Published: January 2009

The effect on uteroplacental blood flow of an epidural anaesthesia containing adrenaline for caesarean section was investigated in ten healthy women using dynamic placental scintigraphy with indium‐113m and a computer‐linked gamma camera. The epidural anaesthesia was performed with 18–22 ml bupivacaine 5mg/ml with adrenaline 2.5 μg/ml followed by an i.v. balanced electrolyte infusion of 10 ml/kg b.w. A significant median decrease in the total maternal placental blood flow of 34% was found (P<0.01). There was also a significant decrease in maternal mean blood pressure of 3 mmHg (0.4 kPa) (P<0.05) and a significant negative correlation between the change in maternal blood pressure and the change in uteroplacental blood flow (r= –0.69, P<0.05).
Ventilatory effects of almitrine bismesilate in dogs breathing normoxic, hyperoxic and hypoxic mixtures
Authors: Gaudy J. H. , Sicard J. F. , Gateau O.
Published: January 2009

The ventilatory effects of 1 mg · kg‐1 i.v almitrine were studied in five dogs anaesthetized with halothane 2% under conditions of normoxia, hyperoxia and hypoxia Ventilation (minute ventilation, respiratory frequency, tidal volume, duration of inspiration and expiration, ratio TI/Ttot and VT/TI), Pao2, Paco2, pHa, systemic arterial pressure and heart rate were measured in air before and following almitrine; in air, after inhalation of pure oxygen and after almitrine in hyperoxia; in air, during hypoxia with Fio2 progressively decreased from 0.21 to 0.12 and after almitrine in hypoxia (Fro2=0.12). Halothane decreased ventilatory response to hypoxia. Almitrine stimulated ventilation irrespective of the level of oxygenation and restored the ventilatory response to hypoxia. Hyperoxia did not suppress ventilatory action of almitrine whose action is probably partly central. Hypoxia and almitrine did not induce major systemic haemodynamic modification.
A comparison of glucose‐free 2% lidocaine and hyperbaric 5% lidocaine for spinal anaesthesia
Authors: Toft P. , Bruun‐Mogensen Chr. , Kristensen J. , Hole P.
Published: January 2009

Fifty patients scheduled to undergo transurethral surgery of the bladder were allocated to receive spinal anaesthesia with either glucose‐free 2% lidocaine (80 mg) or hyperbaric 5% lidocaine (80 mg). Onset time, cephalad spread of analgesia, duration of analgesia, duration and intensity of motor block, quality of analgesia, and the patients' ability to walk 5 m and to micturate postoperatively were assessed. Onset and spread of analgesia were fast and comparable in the two groups. At 60 min, the median segmental level of analgesia was T9 and T10 for the 2% and the 5% group, respectively, allowing transurethral surgery to be performed for at least 1 h. In the 2% group the motor block was more pronounced and longer lasting than in the 5% group. Two patients in the 5% group needed general anaesthesia because of pain. The time from injection of the spinal anaesthetic until the patients were able to walk 5 m and to micturate was equal in the two groups, and 89% of all the patients were able to walk and micturate within 4 h. It is concluded that spinal anaesthesia with 80 mg and 2% or 5% lidocaine provides analgesia for transurethral surgery and is characterized by fast recovery of motor and detrusor function.
Calcium accumulation by sarcoplasmic reticulum in whole muscle homogenate preparations of malignant hyperthermia diagnostic patients and pigs
Authors: Cheah K. S. , Cheah A. M. , Fletcher J. E. , Rosenberg H.
Published: January 2009

Calcium accumulation by the sarcoplasmic reticulum in whole muscle homogenate preparations of malignant hyperthermia‐susceptible (MH+) and non‐susceptible (MH‐) humans and pigs was investigated using a calcium electrode at 35°C. Sarcoplasmic reticulum of MH+humans and pigs showed normal Ca2+accumulation, with no difference being observed in the rate and the time taken to achieve maximal accumulation. However, the capacity for Ca2+accumulation by the sarcoplasmic reticulum in MH+humans and pigs is considerably less stable than normal after prolonged ageing of the whole muscle homogenate preparations in ice. In MH+patients, the capacity for Ca2+accumulation by the sarcoplasmic reticulum showed a decline of 62% at 22 h ageing and 70% at 48 h ageing, as compared with a reduction of only 23% in MH‐patients. In MH+pigs, the sarcoplasmic reticulum showed a 96% deterioration in the capacity for Ca2+accumulation as compared with a loss of only 40% in MH‐pigs at 7 h ageing in ice. In both humans and pigs, the decline in Ca2+accumulation was prevented by incubating the whole muscle homogenate preparations for 2 h at 35°C prior to ageing the preparations. The diminished Ca2+accumulating capacity of the sarcoplasmic reticulum in whole muscle homogenate preparations of MH‐susceptible individuals in our experimental protocol provides a potential diagnostic test for malignant hyperthermia susceptibility.