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Biomedical subjects

H Van Aken

Publications and source records attributed to H Van Aken.

At least 19 recordsLinked to original sources
PubMed1992

[Changes in cerebral metabolism and cerebral blood flow caused by halothane and isoflurane in increasing concentrations].

The results of two studies on the effects of halothane and isoflurane in increasing end-tidal concentrations (0.25; 0.5; 1.0vol%) on the cerebral metabolic rate for oxygen and the cerebral blood flow are compared. Both studies were performed on baboons using the same experimental model. Cerebral blood flow was determined from a washout curve after the intracarotid injection of 133xenon. Halothane and isoflurane led to a dose-dependent decrease of the cerebral metabolic rate for oxygen. Increasing concentrations of halothane caused a decrease of cerebral oxygen consumption from 3.4 +/- 0.8 (baseline) to 2.9 +/- 0.8 (0.25vol%), 2.7 +/- 0.7 (0.5vol%) and 2.4 +/- 0.4 mlO2 100 g-1min-1 at 1.0vol%. The administration of isoflurane reduced the cerebral oxygen consumption significantly from baseline 3.7 +/- 1.0 to 2.9 +/- 0.9 at 0.25vol%, 2.6 +/- 0.6 at 0.5vol% and 1.8 +/- 0.8 mlO2 100 g-1min-1 with 1.0vol%. A significant, dose-independent reduction of the cerebral blood flow from 55.8 +/- 8.0 to 46.3 +/- 10.2 (0.25%) to 44.6 +/- 9.5 (0.5vol%) and 44.5 +/- 10.2 ml 100 g-1min-1 (1.0vol%) was observed with halothane. However, a dose-dependent decrease in calculated cerebrovascular resistance was seen at 1.0vol% of halothane. If mean arterial pressure was kept within the normal limits of cerebrovascular autoregulation by the administration of angiotensin-II-amid during 1.0vol% of halothane a marked increase in cerebral blood flow above the baseline value was observed. The lacking increase in cerebral blood flow observed at 1.0vol% of halothane without blood pressure support appeared to be caused by the low cerebral perfusion pressure rather than by vasoconstriction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Successful transplantation after long-term preservation of dog hearts.

Nucleoside transport inhibition is a new approach to long-term preservation of donor hearts. To evaluate its effectiveness, the following were tested: 1) the effect of nucleoside transport inhibition on high-energy phosphate content after cardioplegic arrest and during long-term cold storage (group I: cardioplegia, control ]n = 18]; group II: cardioplegia plus nucleoside transport inhibitor [n = 18]); 2) the effect of nucleoside transport inhibition on high-energy phosphates and hemodynamic recovery in a modified blood-perfused Langendorff system (group III: 24-h cold storage followed by reperfusion [n = 6]; group IV: addition of nucleoside transport inhibition to cardioplegia but not during reperfusion [n = 6]; group V: addition of nucleoside transport inhibition during reperfusion [n = 6]; group VI: addition of nucleoside transport inhibition to cardioplegia and during reperfusion [n = 6]); and 3) the effect of nucleoside transport inhibition added to cardioplegia and during reperfusion on high-energy phosphate content and outcome after heart transplantation (group VII: no nucleoside transport inhibitor in cardioplegia and during reperfusion [n = 8]; group VIII: addition of nucleoside transport inhibition to cardioplegia and during reperfusion [n = 8]). The following results were obtained: 1) addition of nucleoside transport inhibition prevented high-energy phosphate depletion during cold storage: after 24 h, adenosine triphosphate content in group I was 9.4 +/- 3.1 mumol/g versus 17.7 +/- 3.6 mumol/g dry weight in group II (P less than 0.05); 2) addition of nucleoside transport inhibition to cardioplegia and during reperfusion resulted in greater high-energy phosphate content (adenosine triphosphate in group III was 7.9 +/- 3.5 mumol/g vs. 17.8 +/- 2.8 mumol/g in group VI [P less than 0.05]) and improved hemodynamics upon reperfusion (hearts in group III did not recover, maximum isometric left ventricular pressure development was 1,635 +/- 577 mmHg/sec in group IV, 1,915 +/- 423 mmHg/sec in group V, and 2,437 +/- 201 mmHg/sec in group VI [P less than 0.05, group VI vs. groups IV and V]); and 3) hearts treated with nucleoside transport inhibition in cardioplegia and during reperfusion (group VIII) could be transplanted successfully in contrast to group VII hearts. These data indicate that nucleoside transport inhibition in dogs is highly effective in long-term preservation of donor hearts.

Adenosine↗
PubMed1992

Pulmonary embolism confirmed by transoesophageal echocardiography.

A 60-year-old patient suffered a pulmonary embolism following the application of an Esmarch and pneumatic tourniquet before arthroscopy of the knee. The diagnosis was suspected because of sudden hypotension, ECG changes, a decrease in end-expiratory carbon dioxide concentration and oxygen desaturation as indicated by pulse oximetry. Before performing a sternotomy and cardiopulmonary bypass for removal of pulmonary artery clots, the diagnosis was confirmed by the demonstration of severe right ventricular strain using transoesophageal echocardiography.

Arthroscopy↗
PubMed1992

Light anaesthesia with propofol for paediatric MRI.

Anaesthetic techniques and monitoring equipment may interfere with the technical demands of magnetic resonance imaging. The purpose of this study was to evaluate the safety and efficacy of a light anaesthetic technique with intravenous propofol in nonintubated children. In 20 neuropaediatric patients sedation was induced with propofol 1 mg.kg-1, followed by a continuous infusion titrated to produce adequate immobilisation. Oxygen, 4 l.min-1, was administrated by paediatric face mask. Respiratory rate, end-tidal carbon dioxide tension and oxygen saturation were continuously monitored. In 10 patients capillary blood gas tensions were determined 3 and 20 min after the procedure. Data are reported as mean (SD) and the mean (SD) total propofol dose was 5 (2) mg.kg-1.h-1. Oxygen saturation remained constantly higher than 96% in all patients. End-tidal carbon dioxide tension varied between 35 (7) mmHg 3 min after induction, and 41 (6) mmHg 30 min after the start of the procedure. End-tidal to capillary PCO2 difference was 4 (3) mmHg. Within 20 min after the end of the procedure all patients were fit for dismissal to the ward. One imaging sequence out of 49 was repeated because of movement artefacts. In conclusion, intravenous propofol sedation appears to be a safe and reliable technique for paediatric sedation during magnetic resonance imaging.

Anesthesia, Intravenous↗
PubMed1992

Influence of hydroxyethyl starch on coagulation in patients during the perioperative period.

The perioperative use of hydroxyethyl starch (HES) has been implicated as a possible cause of intracranial bleeding. The purpose of this study was to compare the influence on blood coagulation of the isovolemic replacement of 1-L blood loss with either 6% HES (molecular weight [MW] average: 450,000) or 5% human albumin during neurosurgery or lower abdominal surgery. Twenty patients scheduled for brain tumor surgery and 20 patients undergoing transabdominal hysterectomy were studied. The activated partial thromboplastin time, prothrombin time, fibrinogen concentration, factor VIII coagulant, von Willebrand factor antigen, platelet count, and the activated clotting time were compared after induction of anesthesia, after administration of 500 and 1000 mL of colloid solution, and 24 and 48 h postoperatively. All measured coagulation variables remained within physiologic range. Changes in coagulation indices were identical in neurosurgical and hysterectomy patients, except for a larger increase in fibrinogen concentration 24 and 48 h after hysterectomy. The acute phase reaction of factor VIII coagulant and von Willebrand factor, which plays a role in postoperative hypercoagulability, was attenuated by the use of HES. We conclude that isovolemic replacement of 1-L blood loss with either 6% HES (MW average: 450,000) or 5% human albumin does not interfere with normal hemostasis during and after neurosurgery or lower abdominal surgery.

Adult↗
PubMed1992

Free polymerized hemoglobin versus hydroxyethyl starch in resuscitation of hypovolemic dogs.

Polymerized bovine hemoglobin (PBH) was compared with hydroxyethyl starch (HES) in a hypovolemic shock model. Eighteen dogs were subjected to hemorrhage; systolic arterial blood pressure was maintained at 40 mm Hg for 30 min (mean blood pressure 37.8 +/- 4.7 [SD] mm Hg). Resuscitation was conducted by infusing their own shed blood (control group) or 6% HES (mol wt 200,000) in 0.9% NaCl (HES group) or PBH (PBH group), both in an equal amount to the shed blood. Directly after infusion, oxygen delivery and consumption returned to prehemorrhage levels in all three groups. In the HES group, the lowered arterial oxygen content was compensated by a 158% increase in cardiac output, in contrast to an increase of 31% and 9%, respectively, in the control and PBH groups. Early recovery from hypovolemic shock with regard to oxygen transport and delivery in the PBH group seemed to be comparable to the control group, without the increase in cardiac output seen with HES infusion.

Animals↗
PubMed1992

[Monitoring patients in the anesthesia recovery room. Continuous transcutaneous O2 and CO2 measurements].

To establish whether continuous transcutaneous O2 and CO2 measurement in the recovery room is suitable for non-invasive monitoring of spontaneous respiration in patients newly operated upon, comparative transcutaneous and arterial pO2 and pCO2 investigations were carried out on 35 adults. There was a correlation coefficient of 0.66 between paO2 and tcpO2. The transcutaneous pO2 values measured were 45.3 mm Hg under the arterial values. When the transcutaneous CO2 values were compared with the arterial values, the correlation coefficient was 0.906. The mean transcutaneous pCO2 values measured lay around 0.7 mm Hg above the arterial values. On the basis of this slight deviation in CO2 values, the method appears to be suitable for continuous non-invasive determination of pCO2. The very large deviations in the O2 values indicate that transcutaneous measurement of oxygen partial pressure in this specific examination situation is not sufficiently reliable, which makes questionable the practice of using one piece of equipment for both measurements. In the clinical setting presented, transcutaneous O2 monitoring does not represent an alternative to close clinical observation and pulse oximetry.

Adult↗
PubMed1991

The effects of the addition of sufentanil to 0.125% bupivacaine on the quality of analgesia during labor and on the incidence of instrumental deliveries.

In a double-blinded, randomized, prospective multi-center study of 695 women, we investigated whether epidural injection of sufentanil added to 0.125% bupivacaine with epinephrine (1:800,000) reduces the total amount of local anesthetic required, resulting in less motor blockade and reduced incidence of instrumental deliveries, and improves the quality of analgesia provided by this low concentration of local anesthetic without jeopardizing the safety of the baby. In addition, other potential benefits of sufentanil (such as decrease in the incidence of shivering) and side effects were examined. It was found that adding incremental doses of 10 micrograms sufentanil up to a maximum of 30 micrograms reduced the incidence of instrumental deliveries from 36 to 24% (P less than 0.01) and significantly improved quality and duration of analgesia without depressing the neurobehavioral status of the baby. No other benefits from adding sufentanil were found. The only side effect that occurred more frequently after sufentanil was pruritus. We conclude that epidural injection of 10-30 micrograms sufentanil added to 0.125% bupivacaine with epinephrine (1:800,000) improved the quality of analgesia during labor and reduced the incidence of instrumental deliveries without jeopardizing the safety of the baby.

Adult↗
PubMed1991

Cardiodynamic effects of propofol in comparison with thiopental: assessment with a transesophageal echocardiographic approach.

In 40 patients, the cardiovascular effects of low- and high-dose propofol anesthesia (single bolus of 1.5 mg/kg in group A, 2.5 mg/kg in group C) were examined and compared with those of low- and high-dose thiopental (4 mg/kg in group B, 6.5 mg/kg in group D) (n = 10 patients per group). After induction of anesthesia with etomidate, all patients were ventilated with 70% nitrous oxide in oxygen. Peripheral arterial systolic blood pressure (SAP) and transesophageal echocardiographic short-axis measurements were used to calculate the end-systolic pressure-volume relationship (E) as an index of global myocardial contractility. In all groups SAP decreased significantly below baseline levels for the duration of the measurements (15 min after drug administration), except for the lower dose of thiopental, where SAP returned to baseline values within 10 min. Propofol at a dose of 1.5 mg/kg significantly decreased cardiac output (CO) (from 5.1 +/- 0.25 [mean +/- SEM] to 4.2 +/- 0.23 L/min), stroke volume (SV) (from 64 +/- 3 to 56 +/- 3.6 mL), and the slope of E (from 71 +/- 3.5 to 65 +/- 4.2 mm Hg/mL) until 4 min after drug administration. The higher dose of propofol significantly decreased CO (from 5.1 +/- 0.29 to 4.1 +/- 0.26 L/min), SV (from 64 +/- 3 to 52 +/- 4.6 mL), and the slope of E (from 71 +/- 3.6 to 62 +/- 3.7 mm Hg/mL) until 10 min after drug administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[CSE--the combination of spinal and epidural anesthesia].

The availability of very fine-bore, long spinal needles (28/10 Ga) has stimulated a new wave of interest in the technique of combined spinal-epidural anesthesia. The original double-puncture technique has progressed due to special combination needles to the current spinal-needle-through-epidural-needle technique. The availability of adapted Tuohy needles, special combination sets, and long spinal needles indicates a lack of standardization. An appropriate introduction technique via Tuohy needle allows identification of the anatomic landmarks and contributes to successful anesthesia. The spinal component allows a rapid onset and intense analgesia with appropriate muscle relaxation. The epidural catheter allows the administration of agents into the epidural space as well as optimization and prolongation of analgesia in the postoperative phase. Confirming the position of the epidural catheter introduced after spinal anesthesia has been established remains a matter of concern.

Anesthesia, Epidural↗
PubMed1991

Influence of anesthesia on cerebral blood flow and cerebral metabolism: an overview.

Knowledge of the influence of anesthetics on cerebral blood flow and metabolism is the key to both safe neuroanesthesia practice and understanding the possible neuroprotection offered by these agents. In this paper the authors summarize recent data from the literature. All volatile anesthetics (except for nitrous oxide) produce a dose dependent decrease in cerebral metabolism. The changes in cerebral blood flow depend on the changes in cerebral metabolism and on direct vasodilatory effects; frequently volatile anesthetics increase cerebral blood flow. Cerebral autoregulation is dose-dependently altered. While CO2-response is preserved in the normal brain, this is not necessarily the case in injured brain or in presence of brain edema or tumor. Therefore, the volatile anesthetics are probably not the best choice when brain perfusion is impaired. Intravenous anesthetics (except ketamine) cause a dose-dependent decrease in cerebral metabolism and blood flow. Propofol has identical effects as the other intravenous agents. Autoregulation is preserved during the administration of propofol. The effects of narcotic agents depend largely on the background anesthetic. Pathological conditions induced physiologic changes, and coadministration of other drugs can greatly alter the effects of anesthetics on the brain.

Anesthetics↗
PubMed1991

Tranexamic acid in the treatment of anaphylactic shock.

We report the case of a patient with multiple trauma who developed pronounced anaphylactic shock, and was successfully treated with 1000 mg tranexamic acid intravenously (Exacyl). This antifibrinolytic agent is also a potent inhibitor of the complement system and its use for the prevention and treatment of anaphylactic or anaphylactoid shock is discussed.

Adult↗
PubMed1991

Effects of halothane in low concentrations on cerebral blood flow, cerebral metabolism, and cerebrovascular autoregulation in the baboon.

Halothane in anesthetic concentrations causes cerebral vasodilatation and decreases cerebral oxygen consumption (CMRO2). The purpose of this study was to evaluate cerebral blood flow (CBF) and CMRO2 changes associated with low concentrations of halothane. In eight normoventilated baboons with background anesthesia maintained with phencyclidine and nitrous oxide, CBF and CMRO2 were studied during the administration of end-tidal concentrations of halothane (0.125, 0.25, 0.375, 0.5, 0.75, and 1.0 vol%). Arterial blood pressure was supported by an infusion of angiotension II amide at 0.75 and 1.0 vol% of halothane to maintain an adequate cerebral perfusion pressure. In addition, cerebrovascular autoregulation was tested before and during the administration of 0.375, 0.75, and 1.0 vol% of halothane. Cerebrovascular autoregulation was assessed by observing the response of CBF to an acute increase in mean arterial pressure produced by angiotensin. CMRO2 decreased as the concentration of halothane was increased. At low halothane concentrations (0.125-0.375 vol%), CBF decreased; however, at concentrations above 0.375 vol%, CBF increased with a decrease in cerebrovascular resistance. Autoregulation was intact during 0.375 vol% of halothane, but with 0.75 and 1.0 vol% of halothane, CBF was passively dependent on cerebral perfusion pressure, suggesting impaired autoregulation.

Animals↗
PubMed1990

The use of midazolam versus propofol for short-term sedation following coronary artery bypass grafting.

Midazolam and propofol were compared in an open randomized study for postoperative sedation during 12 h of mechanical ventilation in 40 patients following coronary artery bypass grafting. After an intravenous loading dose of midazolam (50 micrograms.kg-1) or propofol (500 micrograms.kg-1), a titrated continuous infusion was administered of midazolam (mean dose 38.1 micrograms.kg-1.h-1 (SEM 2.6)) or propofol (mean dose 909 micrograms.kg-1.h-1 (SEM 100)) together with a narcotic analgesic infusion. During mechanical ventilation midazolam and propofol produced a similar quality of sedation, but recovery (midazolam 66 min (SEM 16); propofol 24 min (SEM 7)) and weaning from the ventilator (midazolam 243 min (SEM 44); propofol 154 min (SEM 33)) where faster with propofol. In the 2 groups administration of an intravenous loading dose caused a significant decrease in mean arterial pressure but hemodynamic tolerance during maintenance infusion was good.

Aged↗
PubMed1990

Reperfusion injury after 24 hours cold storage of donor hearts. Possible role of leukocyte activation.

The role of neutrophils on the development of reperfusion injury was evaluated in canine hearts. Reperfusion was performed with a closed reperfusion system. 18 dog hearts were arrested by a single dose of National Institute of Health cardioplegia and stored cold (0.5 degrees C) for 24 hours. Thereafter they were randomly attached to one of the following groups. Group I: reperfusion with whole blood (n = 6), group II: reperfusion with low-leukocyte blood (n = 6), group III: reperfusion with low-leukocyte blood plus phenyl-isopropyl adenosine (PIA) (n = 6). Hearts in group I showed an increase of high energy phosphates (HEP) within the first 30 minutes, and a significant decrease during the subsequent 30 minutes. Concomitantly the initially soft hearts turned into stone hearts. In group II and III a significant increase of HEP was seen during the entire reperfusion. After 60 minutes of reperfusion myocardial ATP levels in group III were significantly higher than in group I. All hearts in group III were soft after reperfusion. It is concluded that reperfusion injury appears to be dependent upon the presence and activation of neutrophils, which can be partially prevented by reperfusion with low-leukocyte blood and more so by the simultaneous administration of PIA.

Animals↗