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H Van Aken

Publications and source records attributed to H Van Aken.

At least 19 recordsLinked to original sources
PubMed1999

A comparison of transoesophageal echocardiographic Doppler across the aortic valve and the thermodilution technique for estimating cardiac output.

This study was undertaken in order to elucidate the differences between various planes of measurement and Doppler techniques (pulsed- vs. continuous-wave Doppler) across the aortic valve to estimate cardiac output. In 45 coronary artery bypass patients, cardiac output was measured each time using four different Doppler techniques (transverse and longitudinal plane, pulsed- and continuous-wave Doppler) and compared with the thermodilution technique. Measurements were performed after induction of anaesthesia and shortly after arrival in the intensive care unit. Optimal imaging was obtained in 91% of the patients, in whom a total of 82 measurements of cardiac output were performed. The respective mean (SD) areas of the aortic valve were 3.77 (0.71) cm2 in the transverse plane and 3.86 (0.89) cm2 in the longitudinal plane. A correlation of 0.87 was found between pulsed-wave Doppler cardiac output and the thermodilution technique in either transverse or longitudinal plane. Correlation coefficients of 0.82 and 0.84 were found between thermodilution cardiac output and transverse and longitudinal continuous-wave Doppler cardiac output, respectively. Although thermodilution cardiac output is a widely accepted clinical standard, transoesophageal Doppler echocardiography across the aortic valve offers adequate estimations of cardiac output. In particular, pulsed-wave Doppler cardiac output in both the transverse and longitudinal plane provides useful data.

Aged↗
PubMed1999

Epidural analgesia with local anesthetics after abdominal surgery: earlier motor recovery with 0.2% ropivacaine than 0.175% bupivacaine.

UNLABELLED: The aim of this prospective, randomized, double-blinded study was to compare pain relief, side effects, and ability to ambulate during epidural anesthesia with ropivacaine 0.2% plus sufentanil versus bupivacaine 0.175% plus sufentanil after major gastrointestinal surgery. Epidural catheters were inserted at T8-11, and 30 microg of sufentanil with 15 mL of ropivacaine 0.75% (Group 1, n = 42) or bupivacaine 0.5% (Group 2, n = 44) was injected. General anesthesia was induced, a continuous epidural infusion (5 mL/h) was then begun with 1 microg/mL sufentanil plus ropivacaine 0.2% (Group 1) or bupivacaine 0.175% (Group 2). Postoperatively, the infusion rate was adjusted to individual requirements. Patients were also able to receive additional 2-mL bolus doses every 20 min. Demographic data (except for gender and height), analgesia, drug dosage, and side-effects, including motor blockade (Bromage score), were similar in both groups, but mobilization recovered more quickly in Group 1. Gender, age, ASA physical status, duration of surgery, and intraoperative blood loss had no effect on mobilization. We conclude that epidural analgesia is effective and safe with both regimens. There is not necessarily a correlation between the Bromage score and the desired outcome of mobilization. The ability to walk postoperatively is hastened if ropivacaine is used instead of bupivacaine. IMPLICATIONS: Regarding pain relief and side effects, epidural analgesia with ropivacaine 0.2% and sufentanil 1 microg/mL yields pain scores and pain intensity comparable to those for the well evaluated combination of bupivacaine 0.175% and sufentanil 1 microg/mL. However, earlier recovery of the ability to walk unassisted in patients receiving the combination of ropivacaine and sufentanil may result in their earlier rehabilitation.

Abdomen↗
PubMed1999

High thoracic epidural anesthesia, but not clonidine, attenuates the perioperative stress response via sympatholysis and reduces the release of troponin T in patients undergoing coronary artery bypass grafting.

UNLABELLED: In this prospective study, we evaluated whether high thoracic epidural anesthesia (TEA) or i.v. clonidine, in addition to general anesthesia, affects the cardiopulmonary bypass- and surgery-associated stress response and incidence of myocardial ischemia by their sympatholytic properties. Seventy patients scheduled for elective coronary artery bypass graft (CABG) received general anesthesia with sufentanil and propofol. TEA was randomly induced before general anesthesia and continued during the study period in 25 (anesthetized dermatomes C6-T10). Another 24 patients received i.v. clonidine as a bolus of 4 microg/kg before the induction of general anesthesia. Clonidine was then infused at a rate of 1 microg x kg(-1) x h(-1) during surgery and at 0.2-0.5 microg x kg(-1) x h(-1) postoperatively. The remaining 21 patients underwent general anesthesia as performed routinely (control). Hemodynamics, plasma epinephrine and norepinephrine, cortisol, the myocardial-specific contractile protein troponin T, and other cardiac enzymes were measured pre- and postoperatively. During the preoperative night and a follow-up of 48 h after surgery, five-lead electrocardiogram monitoring was used for ischemia detection. Both TEA and clonidine reduced the postoperative heart rate compared with the control group without jeopardizing cardiac output or perfusion pressure. Plasma epinephrine increased perioperatively in all groups but was significantly lower in the TEA group. Neither TEA nor clonidine affected the increase in plasma cortisol. The release of troponin T was attenuated by TEA. New ST elevations > or = 0.2 mV or new ST depression > or = 0.1 mV occurred in > 70% of the control patients but only in 40% of the clonidine group and in 50% of the TEA group. We conclude that TEA (but not i.v. clonidine) combined with general anesthesia for CABG demonstrates a beneficial effect on the perioperative stress response and postoperative myocardial ischemia. IMPLICATIONS: Thoracic epidural anesthesia combined with general anesthesia attenuates the myocardial sympathetic response to cardiopulmonary bypass and cardiac surgery. This is associated with decreased myocardial ischemia as determined by less release of troponin T. These findings may have an impact on the anesthetic management for coronary artery bypass grafting.

Adrenergic alpha-Agonists↗
PubMed1999

Milrinone modulates endotoxemia, systemic inflammation, and subsequent acute phase response after cardiopulmonary bypass (CPB).

BACKGROUND: Compromised splanchnic perfusion and the resulting intestinal mucosal injury leads to a decreased mucosal barrier function, which allows translocation of intestinal flora and endotoxemia. The authors evaluated the effects of milrinone on splanchnic oxygenation, systemic inflammation, and the subsequent acute-phase response in patients undergoing coronary artery bypass grafting. METHODS: This open, placebo-controlled randomized clinical study enrolled 22 adult patients in two groups. Before induction of anesthesia, baseline values were obtained and patients were randomized to receive milrinone (30 microg/kg bolus administered progressively in 10 min, followed by a continuous infusion of 0.5 microg x kg(-1) x min(-1)) or saline. The following parameters were determined: hemodynamics; systemic oxygen delivery and uptake; arterial, mixed venous and hepatic venous oxygen saturation; intramucosal pH (pHi); and mixed and hepatic venous plasma concentrations of endotoxin, interleukin 6, serum amyloid A, and C-reactive protein. RESULTS: Milrinone did not prevent gastrointestinal acidosis as measured by pHi, but its perioperative administration resulted in significantly higher pHi levels compared with control. Venous and hepatic venous endotoxin and the interleukin 6 concentration were reduced significantly in the milrinone group. Serum amyloid A values were attenuated in the milrinone group 24 h after surgery. No significant differences could be seen in routinely measured oxygen transport-derived variables. CONCLUSIONS: Perioperative administration of low-dose milrinone may have antiinflammatory properties and may improve splanchnic perfusion in otherwise healthy patients undergoing routine coronary artery bypass grafting.

Acute-Phase Reaction↗
PubMed1999

Inotropic effects of diadenosine tetraphosphate in isolated canine cardiac preparations.

We studied the effects of diadenosine tetraphosphate (AP4A) on the force of contraction in canine preparations. The force of contraction was measured in isolated electrically driven (1 Hz) atrial and ventricular cardiac trabeculae from adult dogs. AP4A (100 microM) alone and after prestimulation with 10 nM isoproterenol reduced force of contraction in atrial preparations by approximately 24%. Moreover, AP4A (100 microM) alone and after prestimulation with 10 nM isoproterenol reduced the force of contraction in ventricular preparations by 29 and 29%, respectively. The negative inotropic effects of AP4A were abolished by the A1-adenosine receptor antagonist 1,3-dipropyl-cyclopentyl-xanthine (DPCPX). In summary, in canine myocardium, AP4A alone and after prestimulation with a beta-adrenoceptor agonist exerts negative inotropic effects, which are probably mediated via A1-adenosine receptors.

Animals↗
PubMed1999

Role of nitric oxide in sepsis-associated pulmonary edema.

Transient pulmonary hypertension after inhibition of nitric oxide synthase (NOS) does not alter pulmonary reflection coefficients or lymph flows in endotoxemic sheep. To test the effects of persistent pulmonary hypertension induced by N omega-nitro-L-arginine methylester (L-NAME) and of inhaled NO on pulmonary edema, 18 sheep (three groups) were chronically instrumented with pulmonary artery catheters, femoral arterial fiberoptic thermistor catheters, and tracheostomy. The awake, spontaneously breathing animals received Salmonella typhi endotoxin (lipopolysaccharide; LPS) (10 ng/kg/ min) for 28 h. After 24 h, an airflow of 6 L/min was delivered through the tracheostomy. One group of animals (L-NAME/air) received L-NAME intravenously (25 mg/kg + 5 mg/kg/h) and breathed air. The second group (L-NAME/NO) was given L-NAME and NO (40 ppm) was added to the airflow. The third group was given NaCl 0.9% and breathed air (NaCl/air). Extravascular lung water was measured through the double-indicator dilution technique. Endotoxemia caused pulmonary edema, which was aggravated by L-NAME. Breathing of NO normalized pulmonary artery pressure (Ppa) and ameliorated pulmonary edema. Inhalation of NO may therefore be a therapeutic option for pulmonary edema associated with pulmonary hypertension.

Administration, Inhalation↗
PubMed1998

Arterio-venous carboxyhemoglobin difference suggests carbon monoxide production by human lungs.

Carbon monoxide is hypothesized to be produced by the enzyme heme oxygenase predominantly in liver and spleen, bound to hemoglobin, and excreted by the lungs. Thus, venous carboxyhemoglobin is expected to be higher or equal to arterial carboxyhemoglobin. Unspecific inflammatory stimuli have been shown to induce heme oxygenase in lung tissue possibly leading to pulmonary carbon monoxide production. Arterial and central venous carboxyhemoglobin levels were measured in critically ill patients on the third day of ICU stay (n = 59) as well as in otherwise healthy humans prior to orthopedic surgery (n = 29). Arterial and central venous carboxyhemoglobin were higher in ICU patients than in healthy humans, respectively. In both groups, arterial carboxyhemoglobin was significantly higher than central venous carboxyhemoglobin. The arteriovenous carboxyhemoglobin differences were similar in both groups. The data suggest (a) increased CO-generation in critical illness and (b) pulmonary CO-production in healthy and critically ill humans.

Arteries↗
PubMed1998

[Cardiovascular effects of sevoflurane].

The cardiovascular effects of sevoflurane are similar to those of isoflurane with some minor exceptions. In contrast to isoflurane and particularly to desflurane, sevoflurane has not been associated with increases in heart rate in healthy volunteers and in patients. The coronary vasodilatory potency of sevoflurane appears to be lower than that of isoflurane and it has not been associated with a reduction of blood flow to collateral myocardium in dogs with steal-prone anatomy. In several multi-center studies of patients with coronary artery disease or at high risk for coronary artery disease receiving either sevoflurane or isoflurane for either cardiac or non-cardiac surgery, the incidence of myocardial ischemia and infarction did not differ between treatment groups. In both human and animal models, sevoflurane preserves cerebral blood flow and reduces cerebral metabolic rate, much like isoflurane.

Anesthetics, Inhalation↗
PubMed1998

Comparison of the haemodynamic effects of nitric oxide synthase inhibition and nitric oxide scavenging in endotoxaemic sheep.

OBJECTIVE: The present study compared the effects of nitric oxide (NO) synthase inhibition and NO scavenging with haemoglobin in endotoxaemic sheep. DESIGN: 12 sheep were instrumented for chronic study. Six sheep received LG-nitro-arginine-methylester (L-NAME, 2.5 mg/kg bolus followed by a continuous infusion of 0.5 mg/kg per h), the other 6 sheep received pyridoxalated haemoglobin polyoxyethylene conjugate (PHP, 100 mg/kg bolus followed by a continuous infusion of 20 mg/kg per h). MEASUREMENTS AND RESULTS: Haemodynamic and oxygenation parameters were measured in healthy sheep, after infusion of Salmonella typhosa endotoxin (10 ng/kg per min) for 24 h and after infusion of L-NAME or PHP. The infusion of endotoxin resulted in a hypotensive, hyperdynamic circulation. Infusion of L-NAME increased mean arterial pressure (MAP) from 76.1 +/- 4.2 mmHg to normal values of 95.8 +/- 5.7 mmHg (p < 0.05). PHP increased MAP from 73.0 +/- 3.0 to 88.6 +/- 4.7 mmHg (p < 0.05). This increase in MAP was associated in the L-NAME group with a more prominent drop in cardiac index (from 10.2 +/- 0.4 to 7.0 +/- 0.51.min-1.m-2; p < 0.05) than in the PHP group (from 10.7 +/- 0.2 to 9.3 +/- 0.61.min-1.m-2). During the first 90 min of infusion, cardiac index remained lower in the L-NAME group than in the PHP group. The increase in pulmonary vascular resistance was also higher in the L-NAME group. CONCLUSION: These results suggest, that at the doses used in the experiment, NO scavenging with PHP has smaller effects on cardiac index and pulmonary vascular resistance than NO synthase inhibition with L-NAME. Therefore, the concept of NO scavenging in hyperdynamic sepsis should be further evaluated.

Animals↗
PubMed1998

Thoracic epidural anesthesia does not affect functional recovery from myocardial stunning in sevoflurane-anesthetized dogs.

OBJECTIVE: A beneficial effect of thoracic epidural anesthesia (TEA) on recovery from myocardial stunning was previously shown in awake dogs. The aim of this study was to investigate the effects of TEA on recovery from myocardial stunning in sevoflurane-anesthetized dogs. DESIGN: Randomized animal study. SETTING: Animal laboratory of a university hospital. PARTICIPANTS: Chronically instrumented mongrel dogs. INTERVENTIONS: Six dogs were chronically instrumented for measurement of hemodynamics and myocardial wall thickening fraction (WTF). The following experiments were performed on separate days in a crossover fashion: (1) 10 minutes of ischemia of the left anterior descending (LAD) coronary artery during sevoflurane anesthesia without TEA and (2) 10 minutes of ischemia during sevoflurane anesthesia with TEA. MEASUREMENTS AND MAIN RESULTS: WTF was measured awake (baseline) and at predetermined time points until complete recovery of myocardial function occurred. Induction of anesthesia led to a decrease of WTF compared with baseline. Induction of ischemia led to a further decrease of WTF to negative values, which returned to positive values within the first minute of reperfusion. There were no differences between the two experimental conditions at any of the time points measured. In awake dogs, TEA improved the recovery from myocardial stunning compared with the control experiment. There was no difference between conscious dogs with TEA or sevoflurane-anesthetized dogs with or without TEA. CONCLUSION: TEA has no additional protective effect on the recovery of WTF during sevoflurane anesthesia.

Anesthesia, Epidural↗
PubMed1998

Haemodynamic effects of repeated epidural test-doses of adrenaline in the chronic maternal-fetal sheep preparation.

A randomized crossover study was designed using the chronically instrumented pregnant sheep preparation to study the possible effects of epidural injection of adrenaline as a single compound on the circulation of mother and fetus. Three consecutive identical doses of adrenaline were administered epidurally with a 30 min interval between treatments. In a randomized crossover fashion two dosages (10 and 15 micrograms) were tested on different days. The day after the last epidural experiment the same doses of adrenaline were given intravenously (i.v.). Between the two i.v. doses a 30 min interval was allowed for values to return to baseline. Twenty-seven experiments were performed in eight ewes. Epidural administration of adrenaline did not affect maternal mean arterial pressure, maternal heart rate, uterine blood flow, fetal mean arterial pressure, fetal heat rate, or maternal and fetal blood gases and acid-base status. After i.v. administration of adrenaline the uterine blood flow decreased in a dose-dependent fashion, but the other haemodynamic variables were not affected. In conclusion, this study indicates that consecutive epidural injections of adrenaline have no significant effect on maternal and fetal haemodynamic responses, uterine blood flow, blood gases and acid-base status in the gravid ewe. However, an i.v. injection of 10 or 15 micrograms adrenaline decreases the uterine blood flow and could compromise the fetus.

Acid-Base Equilibrium↗