Haemodynamic effects of thoracic epidural anaesthesia during proximal aortic cross-clamping in pigs

Cross-clamping (XC) of the thoracic aorta induces a hyperdynamic circulation proximal to the aortic clamp. In this investigation, the effects of thoracic epidural anaesthesia (TEA) on the haemodynamic response to XC were studied in pigs. Seventeen pigs were anaesthetized with ketamine, and the thoracic aorta was cross-clamped for 30 minutes. In eight of the animals (TEA-group) a thoracic epidural block (3 ml 0.5% bupivacaine) was added to the general anaesthesia. Prior to XC there was a lower heart rate (HR), cardiac output (CO) and mixed venous oxygen saturation (Sv?O₂) in the TEA-group compared to the nine animals with general anasthesia only (control-group). During XC there was an increase in HR, CO, Sv?o₂ and proximal aortic blood pressure (PPROX) in both groups, without differences between groups. Following aortic declamping central venous pressure (CVP), pulmonary artery pressure (PAP) and pulmonary capillary wedge pressure (PCWP) increased in both groups. Fifteen minutes after declamping, one animal in each group died. It was concluded that in this experimental model, TEA combined with general anaesthesia did not modify the haemodynamic response to XC of the thoracic aorta.     

Haemodynamic and neurohumoral effects of xenon anaesthesia A comparison with nitrous oxide

Thirty-two patients were randomly allocated to be anaesthetised either with nitrous oxide or xenon. Those who received nitrous oxide required significantly more fentanyl peroperatively. Arterial blood pressure and heart rate were adequately controlled during surgery in both groups. Plasma noradrenaline and prolactin increased peroperatively in both groups, but plasma adrenaline and cortisol, which increased in the nitrous oxide group, did not change in the xenon group. Growth hormone was below control in those given xenon, but not in the nitrous oxide group, while dopamine remained unchanged in both groups. Postoperative plasma concentrations of noradrenaline, adrenaline, cortisol and prolactin (in both groups) and dopamine (in the nitrous oxide group) were elevated, and slowly returned to control. No differences were seen between the two gases in effects on plasma sodium and potassium. Xenon, because of its favourable haemodynamic, neurohumoral and antinociceptive properties, deserves a more prominent place in anaesthetic practice than it has so far occupied.     

Haemodynamic assessment of hypovolaemia under general anaesthesia in pigs submitted to graded haemorrhage and retransfusion

We have compared the value of different variables used in the assessment of blood loss during progressive hypovolaemia and resuscitation under general anaesthesia in anaesthetized pigs. We measured mean arterial pressure (MAP), pulmonary capillary wedge pressure (PCWP), the negative component of the systolic arterial pressure variation (delta Down) and left ventricular end-diastolic area (LVEDa) using echocardiography. Blood was progressively withdrawn (up to 35 ml kg-1 in seven steps) and then reinfused after the same pattern. Regression coefficient (r) and normalized slope (nS) of the regression relationship between each variable and amount of blood loss were determined. The difference between the withdrawal and reinfusion curves was assessed by the area between the curves. We also estimated the minimal loss of blood volume which induced significant changes in each variable compared with that under control conditions during withdrawal of blood (minWBV) and maximal loss in blood volume which induced no significant changes in a variable compared with control conditions during retransfusion (maxRBV). During haemorrhage, MAP decreased (from mean 74 (SD 9) to 31 (5) mm Hg; P < 0.001), delta Down increased (from 1.2 (1.4) to 11.4 (4.2) mm Hg; P < 0.001), PCWP decreased (from 6.2 (2.1) to 0.3 (1.0) mm Hg; P < 0.001) and LVEDa decreased (from 13.8 (2.0) to 5.1 (2.0) cm2; P < 0.01). The highest r values were obtained with MAP and LVEDa, and the highest nS value with delta Down. The least difference between withdrawal and reinfusion was with LVEDa, the lowest values of minWBV were with PCWP and LVEDa, and the highest value of maxRBV was obtained with PCWP. During progressive haemorrhage under general anaesthesia, LVEDa was an accurate variable for assessment of blood volume loss, delta Down contributed no further information compared with MAP, and PCWP was the most reliable variable for assessing return to baseline blood volume.      

Cerebral and regional organ perfusion in pigs during xenon anaesthesia

Little is known about the haemodynamic effects of inhaled xenon on regional organ perfusion. The aim of this study was to investigate the effect of 79% xenon ventilation on organ perfusion in pigs. We investigated 10 pigs, which were randomly allocated to receive either xenon 79% or total intravenous anaesthesia (TIVA)/oxygen anaesthesia. Microspheres were used to determine organ perfusion. The following regions of interest were investigated: cerebral cortex, medulla oblongata, brainstem, cerebellum, liver, kidney, small intestine, colon, muscle, skin and heart. The results demonstrated a significant increase in regional perfusion in the brainstem (+63%), cerebral cortex (+38%), medulla oblongata (+35%) and cerebellum (+34%). All other organs showed no significant change in regional perfusion. We conclude that xenon should be used with caution in clinical situations associated with pathological increases in intracranial pressure, e.g. neurosurgical procedures, head injury, cerebral mass lesions or stroke.     

Haemodynamic effects of induction of general anaesthesia with propofol during epidural anaesthesia

PURPOSE: To clarify whether propofol administration during thoracic or lumbar epidural anaesthesia intensifies the haemodynamic depression associated with epidural anaesthesia. METHODS: Patients (n = 45) undergoing procedures of similar magnitude were randomly divided into three study groups: a control group (n = 15) receiving general anaesthesia alone and two study groups undergoing thoracic (n = 15) and lumbar epidural anaesthesia (n = 15) before induction of general anaesthesia. All patients received 2 mg.kg-1 propofol at a rate of 200 mg.min-1, followed by a continuous infusion of 4 mg.kg-1.hr-1. Mean arterial blood pressure (MAP) and heart rate (HR) were measured at baseline, three minutes after induction, and one minute after tracheal intubation in all three groups and at 20 min after epidural anaesthesia was established in the thoracic and lumbar groups. RESULTS: Following epidural anaesthesia, MAP decreased from 94 +/- 14 (SD) at baseline to 75 +/- 11 mmHg (P < 0.0001) in the thoracic group and from 92 +/- 12 to 83 +/- 15 mmHg in the lumbar group. After propofol administration, MAP decreased further in the thoracic group to 63 +/- 9 mmHg (P = 0.0077) and to 67 +/- 10 mmHg (P = 0.0076) in the lumbar group. The MAP following propofol induction in the thoracic group (P < 0.0001) and in the lumbar group (P = 0.0001) was lower than MAP in the control group (81 +/- 9 mmHg). HR decreased only in response to thoracic epidural anaesthesia (P = 0.0066). CONCLUSION: The hypotensive effects of propofol are additive to those of epidural anaesthesia, resulting in a profound decrease in mean arterial pressure.     

Haemodynamic effects of three doses of dihydroergotamine during spinal anaesthesia

We performed a randomized study comparing the haemodynamic effectsof three doses of the vasopressor dihydroergotamine (DHE) (5,10 and 15 µg kg^–1) in 30 ASA 1 and 2 patients,aged 53–87 yr, undergoing spinal anaesthesia. Non-invasivesystolic arterial pressure (SAP), heart rate and central venouspressure (CVP) were recorded continuously for 25 min. Intravenousfluids were withheld during this period. All three doses ofDHE reversed the lowering effects of spinal anaesthesia on SAPand CVP (P<0.0001), and these effects were smooth in onsetand sustained. Whereas the lowest (5 µg kg^–1)dose restored SAP and CVP to near prespinal values, the higher(10 and 15 µg kg^–1) doses resulted inabove-baseline increases in SAP of 7% and in CVP of 2.7 cm H₂O(P<0.05). The haemodynamic profile of DHE makes it a usefulagent for managing hypotension during spinal anaesthesia. Adose of 5–10 µg kg^–1 is recommended. Br J Anaesth 2001; 87: 499–501     

Haemodynamic effects of intravenous bupivacaine during high thoracic epidural anaesthesia

Administration of small doses of bupivacaine epidurally at the upper thoracic level will partially block the cardiac sympathetic nerves but not the sympathetic outflow via the adrenals. Local anaesthetics have direct systemic effects on the myocardium and the systemic circulation. The present study aimed to examine the effect of high thoracic epidural anaesthesia (TEA) in elderly patients, and to examine the effect of raising plasma bupivacaine concentrations in these patients, who had earlier had the sympathetic innervation of the heart blocked by thoracic epidural anaesthesia. Fifteen elderly patients scheduled for thoracotomy took part in the study. All received high thoracic epidural anaesthesia including the upper five thoracic dermatomes. When epidural block was established, ten patients received bupivacaine 3 mg/min intravenously for 20 min, while five patients received a corresponding volume of normal saline solution. After TEA was established, heart rate, mean arterial blood pressure and cardiac output decreased. When bupivacaine was given to these patients intravenously during the block, mean arterial blood pressure increased, while cardiac output decreased still more. The mechanisms behind these effects seem to be a direct constriction of the systemic blood vessels and a depressive effect on the myocardium, which was blocked from the influence of the cardiac sympathetic nerves by the high thoracic epidural block.     

Arterial and mixed venous xenon blood concentrations in pigs during wash-in of inhalational anaesthesia

There are no data available on the kinetics of blood concentrationsof xenon during the wash-in phase of an inhalation anaesthesiaaiming at 1 MAC end-expiratory concentration. Therefore, weanaesthetized eight pigs with continuous propofol and fentanyland measured arterial, mixed venous and end-expiratory xenonconcentrations by gas chromatography–mass spectrometry1, 2, 3, 4, 5, 7, 10, 15, 20, 30, 60 and 120 min afterstarting the anaesthetic gas mixture [67% xenon/33% oxygen;3 litre min^–1 during the first 10 min,thereafter minimal flow with 0.48 (SD 0.03) litre min^–1].End-expiratory xenon concentrations plateaued (defined as <5%change from the preceding value) at 64 (6) vol% after 7 min,and arterial and mixed venous xenon concentrations after 5 and15 min respectively. The highest arterio-venous concentrationdifference occurred after 3 min. Using the Fick principle,we calculated a mean xenon uptake of 3708 (829) and 9977 (3607)ml after 30 and 120 min respectively. Br J Anaesth 2001; 87: 497–8     

Haemodynamic effects of rocuronium during fentanyl anaesthesia: comparison with vecuronium

Haemodynamic variables were measured following administration of rocuronium 0.6 mg· kg^?1 or vecuronium 0.08 mg · kg^?1 (approximately equivalent to 2 × ED₉₅ doses) in patients anaesthetized with fentanyl 50 μg· kg^?1 and scheduled to undergo elective coronary artery bypass grafting. There were increases in stroke volume index (+15%) and cardiac index (+11%), and a decrease in pulmonary capillary wedge pressure (?25%) following administration of rocuronium (P < 0.05). The changes in heart rate (+7%), mean arterial pressure (?5%), systemic vascular resistance (?12%) and other measured or derived indices were insignificant. In comparison the administration of vecuronium was associated with decreases in heart rate (?7%), mean pulmonary artery pressure (?17%), central venous pressure (?15%) and the rate-pressure product (?9%) (P < 0.05). The changes in mean arterial pressure (?7%), cardiac index (?6%) and systemic vascular resistance (?8%) following vecuronium were insignificant. There were no differences in any of the variables between rocuronium and vecuronium. The absolute values of all variables were, however, within acceptable clinical limits. There was no evidence of histamine release in any patient. The present study shows that rocuronium 0.6 mg · kg^?1 is associated with changes of only small magnitude in haemodynamic variables.     

Cardiovascular effects of xenon and nitrous oxide in patients during fentanyl-midazolam anaesthesia

Xenon anaesthesia appears to have minimal haemodynamic effects. The purpose of this randomised prospective study was to compare the cardiovascular effects of xenon and nitrous oxide in patients with known ischaemic heart disease. In 20 patients who were due to undergo coronary artery bypass graft surgery, 30 min following induction of anaesthesia with fentanyl 30 microg x kg(-1) and midazolam 0.1 mg x kg(-1) but prior to the start of surgery, xenon or nitrous oxide 60% was administered for 15 min. The results showed that xenon caused a minimal decrease in the mean arterial pressure (from 81 (7) to 75 (8) mmHg, mean (SD)), but did not affect the systolic function of the left ventricle, as demonstrated by unchanged left ventricular stroke work index (LVSWI) and the fractional area change of the left ventricle (FAC) derived from transoesophageal echocardiography (TOE). However, in contrast, nitrous oxide was found to decrease the mean arterial pressure (from 81 (8) to 69 (7) mmHg), the LVSWI, and the FAC. The cardiac index, central venous and pulmonary artery occlusion pressures, systemic and pulmonary vascular resistances, and the TOE-derived E/A ratio through the mitral valve were unchanged by xenon or nitrous oxide. We conclude that xenon provides improved haemodynamic stability compared with nitrous oxide, conserving the left ventricular systolic function.     

Haemodynamic effects of intravenous methadone anaesthesia in dogs

The cardiovascular effects of intravenous anaesthetic doses of methadone were evaluated in 30 mongrel dogs breathing oxygen. One half of the dogs were unpremedicated (group B) and the other half (group A) received atropine 1.5 mg intramuscularly 20 minutes before infusion of methadone. After collection of control cardiovascular data dogs in both groups were given 0.3 mg · kg_-1 of methadone intravenously over a ten-minute period and cardiovascular dynamics were again recorded immediately following infusion and 20 minutes later. Following this 0.5 mg · kg^-1 of methadone was infused over ten minutes and measurements were obtained as with the 0.3 mg · kg^-1 dose. Data were recorded in a similar fashion before and following intravenous infusion of methadone 1.0, 1.5 and 2.0 mg · kg^-1 in the same animals, so that after the final infusion each animal had received a total accumulated dose of methadone 5.3 mg · kg^-1. Group A dogs had significantly higher heart rates, mean aortic pressures and cardiac output than group B dogs during control conditions and throughout the study. Group A dogs showed no change in any cardiovascular variable measured during or after infusion of methadone 0.3 or 0.5 mg · kg^-1. Methadone 1.0, 1.5 and 2.0 mg · kg^-1 produced slight (but similar) decreases in mean aortic blood pressure but did not change heart rate, cardiac output, pulmonary capillary wedge pressure, right atrial pressure or pulmonary systemic vascular resistance. In group B dogs methadone 0.5 mg · kg^-1 produced modest decreases in heart rate, cardiac output and aortic blood pressure. Infusion of methadone 1.0,1.5 and 2.0 mg · kg^-1 (total doses of 1.8, 3.3 and 5.3 mg · kg^-1) produced changes similar to those with 0.5 mg · kg^-1 of the compound in group B animals with the exception of heart rate, which was further decreased, and pulmonary vascular resistance, which was increased with 1.5 and 2.0 mg · kg^-1 infusions. These data demonstrate that intravenous anaesthetic doses of methadone produce only minimal changes in cardiovascular dynamics, most of which can be avoided by prior administration of atropine.     

Effects of xenon anaesthesia on intestinal oxygenation in acutely instrumented pigs

Background. Xenon is a narcotic gas that might be able to replacevolatile anaesthetics or nitrous oxide due to its favourablepharmacological properties, such as providing haemodynamic stability.Intestinal oxygenation is affected by most volatile anaestheticsas a result of cardiodepressive effects. Reducing oxygenationof the gut might be a factor leading to perioperative organdysfunction. This animal study was designed to assess the effectsof xenon on intestinal oxygenation. Methods. After ethical approval, 24 anaesthetized, acutely instrumentedpigs were randomly assigned to three groups: nine animals receivedxenon anaesthesia with inspiratory concentrations of 0, 20,50 and 65% in addition to their basic i.v. anaesthesia, nineanimals served as a study control group, and five animals wereused to assess model stability. Measurement of systemic andregional haemodynamic and oxygenation parameters was made 30min after changing the xenon concentration. Results. Xenon elicited dose-dependent systemic haemodynamicchanges: heart rate and cardiac output decreased by 30%, whilemean arterial pressure was stable. Superior mesenteric arteryblood flow was lower in the xenon group. Vascular resistanceof the superior mesenteric artery increased. The small intestinaloxygen supply decreased with increasing xenon concentration;the mucosal tissue oxygen partial pressure decreased but didnot reach hypoxic (<5 mm Hg) values. Serosal tissue oxygenpartial pressure was maintained. Conclusions. Xenon, in addition to basic i.v. anaesthesia, eliciteda decrease in cardiac output and maintained mean arterial pressure.Intestinal oxygenation was maintained, although regional macrohaemodynamicperfusion decreased. Xenon does not impair intestinal oxygenationunder physiological conditions.      

Haemodynamic changes during anaesthesia in knee-elbow position.

BACKGROUND: To evaluate hemodynamic alterations during surgical procedures performed in the knee-elbow position. METHODS: Design of the study: prospective evaluation of the aortic blood flow (ABF) and other cardiovascular variables measured with a transesophageal Doppler (TED) in 2 groups of patients free of previous cardiovascular diseases undergoing lumbar discectomy. ENVIRONMENT: Operating theatre of a neurosurgical department. Beside TED, the standard monitoring included continuous ECG surveillance, capnometry, noninvasive measurement of blood pressure and pulsoxymetry. PATIENTS: Overall, 24 ASA 1 patients have been enrolled. In 12 patients (Group A) the intervention was performed without dobutamine. In the other 12 patients (Group B) dobutamine (2.5-3 micrograms/kg/min) was started from the beginning of the intervention; the two groups did not differ in terms of age, body size, duration of surgery or anesthetic technique used; hemodynamic measurements were obtained at the beginning of the intervention (T1), with the patients still supine, during the intervention in the knee-elbow position (T2) and finally at the end of the procedure (T3) being the patients still anesthetized but lying supine again. RESULTS: In both groups the ABF; the systolic volume and the ETCO2 significantly decreased in the knee-elbow position; concomitantly, peripheral vascular resistances increased. In Group B, the hemodynamic variables were significantly better than in the other group. CONCLUSIONS: In the patients enrolled, the perioperative administration of low-dose dobutamine was associated with better cardiovascular performance.     

Increased airway resistance during xenon anaesthesia in pigs is attributed to physical properties of the gas

Background. In this study we investigated the effects of thephysical properties of xenon on respiratory mechanisms in pigs. Methods. With institutional approval, 10 female pigs (mean 25.2(SD 2.5) kg) were anaesthetized with thiopental, remifentanil,and pancuronium. Gas flow and pressure were recorded continuouslyat the proximal end of the tracheal tube during constant flowventilation for control, with 100% oxygen (control), followedby 1.5% isoflurane in 70/30% nitrogen/oxygen, 1.0% isofluranein 70/30% nitrous oxide/oxygen, and 70/30% xenon/oxygen in randomorder. Compliance (C) and resistance (R) were calculated usinga single compartment model. Resistance was corrected for gasviscosities     

Hepatic function during xenon anesthesia in pigs

BACKGROUND: Inhalation anesthetics decrease liver perfusion and oxygen consumption by changing the distribution pattern of perfusion between the hepatic artery and the portal vein and by direct effects on liver cells. The effects of xenon on liver perfusion and function have been not investigated until now. METHODS: Fourteen pigs were randomly assigned to two groups to receive either 73-78% xenon or 75% nitrogen in oxygen with additional supplementation of pentobarbital and buprenorphine. Microspheres were used to determine the arterial perfusion of the liver and splanchnic organs. Oxygen contents were measured by catheterization of the portal and a liver vein. Lactate and glucose plasma concentrations were measured in hepatic, mixed venous and arterial blood. Alanine aminotransferase (ALT) and lactate dehydrogenase (LOH) plasma concentrations were measured in arterial blood. Urea production rates were calculated to assess hepatic metabolic function. RESULTS: Significant higher oxygen contents were found in the liver venous blood during xenon anesthesia. No differences were found in any other investigated parameters. CONCLUSION: Higher oxygen content in liver venous blood observed during xenon anesthesia was not induced by changes in hepatic perfusion distribution or by an impairment of liver metabolic capacity. However, it can be explained by similar results known from inhalation anesthesia. Additionally, the effect can be caused by the reduction of plasma catecholamine concentrations during xenon anesthesia.     

Haemodynamic effects of atropine during halothane or isoflurane anaesthesia in infants and small children

In this study, two-dimensional and pulsed Doppler echocardiography were used to measure cardiovascular changes before and after IV atropine in 31 infants and small children during halothane (n = 15) or isoflurane (n = 16) anaesthesia. Prior to induction of anaesthesia heart rate (HR), mean blood pressure (MBP), and two0dimensional echocardiographic dimensions of the left ventricle and pulmonary artery bloodflow velocity were measured by pulsed Doppler echocardiography. Cardiovascular measurements were repeated while anaesthesia was maintained at 1.5 MAC halothane (n = 15) or isoflurane (n = 16). Atropine 0.02 mg·kg⁻¹ IV was then administered and two minutes later, a third set of cardiovascular data was obtained. Heart rate decreased during halothane anaesthesia but did not change significantly during isoflurane anaesthesia. Mean blood pressure, cardiac output (CO) and stroke volume (SV) decreased similarly during 1.5 MAC halothane or isoflurane anaesthesia. Ejection fraction (EF) decreased and left ventricular end-diastolic volume (LVEDV) increased significantly in bothgroups, but decreases in EF (32 ± 5 percentvs18 ± 5 per cent) and increases in LVEDV (18 ± 7 per cent vs7 ± 5 per cent) were significantly greater during halothane than during isoflurane anaesthesia. Following atropine, HR increased more in the patients maintained with halothane (31 ± 6 per cent), than during isoflurane anaesthesia (18 ± 5 per cent). Atropine increased CO in both groups of patients, but SV and EF remained unchanged. When compared with awake values, HR increased similarly and significantly (18 ± 4 per cent) following atropine in both groups, and CO returned to control levels. Halothane decreased EF and increased LVEDV more than isoflurane at 1.5 MAC end— expired anaesthetic levels. Atropine did not diminish the myocardial depression produced by halothane or isoflurane. The increase in CO following atropine during halothane and isoflurane anaesthesia in infants and small children is the result of increases in HR alone. Nous avons utilisé un appareil à échocardiographie bi-dimensionnelle couplé à un Doppler pulsé chez des bébés et de jeunes enfants pour évaluer l’impact hémodynamique de l’halothane (n = 15) et de l’isoflurane (n = 16) et la modification possible de ces effets par l’atropine. Nous avons mesure la frequence cardiaque (FC), la pression artérielle moyenne (PAM), la dimension de la cavité ventriculaire gauche (par écho bi-dimensionnelle) et la vélocité du flot sanguin pulmonaire (par Doppler) et ce, en trois occasions soit avant l’induction, après l’instauration de 1.5 MAC d’halothane ou d’isoflurane et finalement, deux minutes après l’injection IV de 0.02 mg·kg⁻¹ d’atropine. On ne nota une baisse de la frequence cardiaque qu’avec l’halothane tandis que la PAM, le débit cardiaque (DC) et le volume d’éjection (VE) diminuaient autant avec l’un ou l’autre anesthésique. La diminution de la fraction d’éjection (FE) et l’augmentation du volume télédiastolique du ventricule gauche (VTDVG) significatives pour les deux groupes, étaienl plus marqué avec l’halothane qu’avec l’isoflurane: FE 32 ± 5 pour cent vs18 ±5 pour cent; VTDVG 18 ± 7 pour cent vs 7 ± 5 pour cent. Avec l’atropine, la FC monta plus dans le groupe halothane (31 ± 6 pour cent) que dans le groupe isoflurane (18 ± 5 pour cent), le DC augmentant dans les deux groupes, alors que le VE et la FE demeuraient inchangés. Comparée aux mesures pré-induction, l’atropine amenait une hausse significative de la FC, semblable dans les deux groupes (18 ± 4 pour cent) et restaurait le DC. Donc, chez les bebes et les jeunes enfants, a 1.5 MAC, l’halothane diminue la FE et augmente le VTDVG plus que ne le fait l’isoflurane. L’atropine ne modifie pas la depression myocardique et elle ne restaure le DC que par une hausse de la FC.

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Supported by PHS Grant No. 8507300 from the College of Medicine, University of Iowa Hospital, Iowa City, IA.     

Haemodynamic effects of thoracic epidural anaesthesia during induction of anaesthesia: an investigation into the effects of tracheal intubation during target-controlled infusion of propofol

We compared haemodynamic changes following induction of anaesthesia with propofol during tracheal intubation with and without epidural anaesthesia. Nineteen patients were divided into two groups to receive epidurally administered saline (Group C) or lidocaine 1.5% (Group E). The propofol infusion was started to produce blood concentrations of 3 microg.ml(-1), and following fentanyl and vecuronium administration, tracheal intubation was performed. Mean arterial blood pressure (MBP), heart rate (HR), Bispectral index and effect-site propofol concentration were recorded. Time to loss of consciousness was significantly shorter in Group E than in Group C. The effect-site propofol concentration at loss of consciousness was significantly lower in Group E than in Group C. MBP and HR were significantly lower following propofol induction in both groups, and were significantly increased following intubation in Group C but not in Group E. In conclusion, epidural anaesthesia did not produce profound hypotension following induction of anaesthesia and produced a reduction in the haemodynamic response to tracheal intubation during a target controlled infusion of propofol.     

Haemodynamic effects of pneumoperitoneum and the influence of posture during anaesthesia for laparoscopic surgery

The laparoscopic operating technique is being applied increasingly to a variety of intra-abdominal operations. Intra–abdominal gas insufflation, i.e. pneumoperitoneum (PP), is then used to allow surgical access. The haemodynamic effects of PP in combination with different body positions have not been fully examined. Eleven patients without signs of cardiopulmonary disease were studied before and during laparoscopic cholecystectomy under propofol–fentanyl anaesthesia with controlled ventilation. Swan-Ganz and radial arterial catheterization were used to determine haemodynamic data in the horizontal position, with a 15–20° head–down tilt and a 15–20° head–up tilt. The measurements were repeated after insufflation of carbon dioxide to an intraabdominal pressure of 11–13 mmHg, as well as during surgery. The ventricular filling pressures of the heart were strictly dependent on body position. PP in the horizontal position increased pulmonary capillary wedge pressure by 32% ( P < 0.01), central venous pressure by 58% ( P < 0.01), and mean arterial pressure by 39% ( P < 0.01). When PP was combined with a head–down tilt, there was a further increase in filling pressures by approximately 40% ( P < 0.01), while the reduction in filling pressures during the head–up tilt was counteracted by PP. During PP with a head–up tilt, the filling pressures did not differ from those in the horizontal position without PP. CI showed a certain dependency on filling pressures. It is concluded that PP causes signs of elevated preload and afterload. The combination of PP and a head–up tilt is associated only with signs of an elevated afterload. It is suggested that the haemodynamic response to PP, especially in combination with a head–down tilt, may be hazardous to patients with compromised heart function.     

Haemodynamic effects of glycopyrrolate pre-treatment before phenylephrine infusion during spinal anaesthesia for caesarean delivery

BackgroundPhenylephrine given during spinal anaesthesia for caesarean delivery often induces a decrease in heart rate which may decrease cardiac output. Anticholinergic drugs may be given to attenuate this effect but may also cause more labile blood pressure. This study evaluated the effects of glycopyrrolate pre-treatment on non-invasively measured cardiac output and accuracy of blood pressure control.MethodsAt induction of spinal anaesthesia for caesarean delivery, 104 patients randomly received intravenous glycopyrrolate 4 μg/kg or saline placebo. Systolic blood pressure, measured at 1-min intervals, was maintained near baseline using closed-loop feedback computer-controlled phenylephrine infusion with crystalloid cohydration. Cardiac output and stroke volume were measured using suprasternal Doppler ultrasonography at baseline and 5-min intervals for 20 min. Blood pressure control was assessed using performance error calculations.ResultsEleven patients were excluded. Patients who received glycopyrrolate (n = 45) had greater cardiac output over time (P < 0.001), greater heart rate over time (P < 0.001), similar stroke volume over time (P = 0.95), and lower median phenylephrine infusion rate (P = 0.006) compared with control (n = 48). There was no difference in the incidence of hypotension between groups. Analysis of blood pressure control showed greater positive bias, greater inaccuracy and greater wobble in the glycopyrrolate group (all P < 0.05). Neonatal outcome was similar between groups.ConclusionsGlycopyrrolate 4 μg/kg given at the start of a phenylephrine infusion increased heart rate and cardiac output but also decreased accuracy of blood pressure control, increased the incidence of hypertension and caused an increased incidence of dry mouth postoperatively compared with control.     

Haemodynamic and EEG changes during rapid-sequence induction of anaesthesia

The relationship between the changes in haemodynamic function and the electroencephalogram (EEG) during rapidsequence induction of anaesthesia was studied in 15 ASA I patients. Anaesthesia was induced with a bolus thiamylal (5 mg · kg^?1 iv) followed by succinylcholine (1 mg · kg^?1). Tracheal intubation was attempted one minute after the injection of succinylcholine. The EEG was monitored by a computerized aperiodic analysis device, the Lifescan? (Neurometrics?, San Diego, CA) using the activity edge (AE) to detect brain electrical activity. After induction of anaesthesia, systolic blood pressure (sBP) decreased by 11% from the baseline value, and the AE decreased from 13.0 Hz to 3.4 Hz. Following tracheal intubation, the sBP increased from the post-induction values by 44% (P < 0.05), and the AE increased to 13.1 Hz (P < 0.05) simultaneously. In conclusion, rapid-sequence induction using thiamylal (5 mg · kg^?1) caused depression in brain activity as assessed by AE, while laryngoscopy and tracheal intubation caused an increase in activity. This indicates that this dose of thiamylal for rapid-sequence induction may not be sufficient to sustain an adequate anaesthetic level and blunt the haemodynamic responses to intubation.