PubMed Health⌕ Search

Biomedical subjects

W Reeker

Publications and source records attributed to W Reeker.

15 recordsLinked to original sources
PubMed2004

Effect of remifentanil on intracranial pressure and cerebral blood flow velocity in patients with head trauma.

BACKGROUND: Remifentanil, an ultra-short-acting opioid, is used as an on-top analgesic in head trauma patients during transient painful procedures, e.g. endotracheal suctioning, physiotherapy, on the intensive care unit. However, previous studies have shown that opioids may increase intracranial pressure and decrease cerebral blood flow. METHODS: The present study investigates the effect of remifentanil on mean arterial blood pressure, intracranial pressure measured with intraparenchymal or epidural probes, and on cerebral blood flow velocity assessed by transcranial Doppler flowmetry in 20 head trauma patients sedated with propofol and sufentanil. Ventilation was adjusted for a target PaCO2 of 4.7-5.1 kPa. After baseline measurements a bolus of remifentanil (0.5 microg x kg(-1) i.v.) was administrated followed by a continuous infusion of remifentanil (0.25 microg x kg(-1) x min(-1) i.v.) for 20 min. RESULTS: There was no change in mean arterial blood pressure, intracranial pressure, and cerebral blood flow velocity in response to remifentanil infusion over time. Statistical analysis was performed using the Wilcoxon Signed Rank test. CONCLUSIONS: These data suggest that remifentanil can be used for on-top analgesia in head trauma patients without adverse effects on cerebrovascular haemodynamics, cerebral perfusion pressure or intracranial pressure.

Analgesics, Opioid↗
PubMed2000

[Metformin-induced lactic acidosis].

HISTORY AND ADMISSION FINDINGS: A 62-year-old woman had been found unconscious on her bed. She had to be resuscitated several times in the ambulance on the way to hospital. On admission her pupils were dilated and fixed, the cardiovascular system was unstable. Her rectal temperature was 28 degrees C. She was a diabetic being treated with metformin and glimepiride and was in incipient renal failure (serum creatinine 1.5 mg/dl). She was also in heart failure due to coronary heart disease and was in a debilitated state. INVESTIGATIONS: She had marked lactic acidosis (lactate 45.3 mmol/l; pH 6.6). Toxicological screening tests were negative. TREATMENT AND COURSE: In the absence of a history she was at first treated symptomatically. Conventional management of the lactic acidosis neither corrected the acidosis nor stabilized the circulatory system. Continuous veno-venous haemodialysis with bicarbonate-buffered solutions succeeded in reducing the need for catecholamines. Neurological examination was supplemented by recording acoustic and sensory evoked potentials. Suspected metformin-induced lactic acidosis was confirmed by appropriate tests. Three weeks after admission she was well enough to be transferred to a normal medical ward and ultimately discharged without further complications. CONCLUSION: Metformin should only be prescribed if the contraindications, in particular renal failure are carefully monitored. Severe lactic acidosis should be treated early with continuous veno-venous haemodialysis with bicarbonate-buffered substituting fluids. The good neurological results in this case are probably largely due to the marked hypothermia.

Acidosis, Lactic↗
PubMed2000

High-dose S(+)-ketamine improves neurological outcome following incomplete cerebral ischemia in rats.

PURPOSE: To determine the effects of the non-competitive NMDA-receptor antagonist S(+)-ketamine on neurological outcome in a rat model of incomplete cerebral ischemia. METHODS: Thirty rats were anesthetized, intubated and mechanically ventilated with isoflurane, O2 30% and nitrous oxide 70%. Following surgery animals were randomly assigned to one of the following treatment groups: Rats in group 1 (n = 10,OFF control) received fentanyl (bolus: 10 microg x kg(-1) i.v.; infusion 25 microg x kg(-1) x h(-1)) and N2O 70% / O2. Rats in group 2 (n = 10) received O2 30% in air and low-dose S(+)-ketamine (infusion: 0.25 mg x kg(-1) x min(-1)). Rats in group 3 (n = 10) received O2 30% in air and high-dose S(+)-ketamine (infusion: 1.0 mg x kg(-1) min(-1)). Following 30 min equilibration period ischemia was induced by combined unilateral common carotid artery ligation and hemorrhagic hypotension to 35 mm Hg for 30 min. Plasma catecholamines were assayed before and at the end of ischemia. Neurological deficit was evaluated for three postischemic days. RESULTS: Neurological outcome was improved with high-dose S(+)-ketamine when compared to fentanyl / N2O -anesthetized controls (9 vs. 1 stroke related deaths, P<0.05). Increases in plasma catecholamine concentrations were higher in fentanyl / N2O -anesthetized (adrenaline baseline 105.5+/-92.1 pg x ml(-1), during ischemia 948+/-602.8 pg x ml(-1), P<0.05; noradrenaline baseline 407+/-120.2 pg x ml(-1), ischemia 1267+/-422.2 pg x ml(-1), P <0.05) than in high-dose S(+)-ketamine-treated animals (adrenaline baseline 71+/-79.5 pg x ml(-1), ischemia 237 +/-131.9; noradrenaline baseline 317.9+/-310.5 pg x ml(-1), ischemia 310.5+/-85.7 pg x ml(-1)). CONCLUSION: Neurological outcome is improved following incomplete cerebral ischemia with S(+)-ketamine. Decreases in neuronal injury may be related to suppression of sympathetic discharge.

Animals↗
PubMed1999

[Translaryngeal tracheostomy in Bechterew's disease and Guillain-Barre syndrome].

Recently, the Translaryngeal Tracheostomy (TLT) has been developed by Fantoni [1,2]. This new technique has been suggested for long-term ventilated intensive care patients as an alternative to other minimal invasive tracheostomy techniques like the Percutaneous Dilatational Tracheostomy described by Ciaglia [3] or Griggs [4]. In comparison to these techniques, the main advantage of the TLT seems to be the access to the airway from inside the trachea to outside. This procedure minimizes the risk of luxations of parts of the tracheal wall into the tracheal lumen resulting in obstructive ventilatory problems. The often discussed risk of stomal infections associated with this technique due to a possible bacterial contamination of the mouth seems not to be clinically relevant. In the past minimal invasive tracheostomy techniques have only been recommended for patients with normal anatomical conditions and without any special risk factors. The present case report describes the successful performance of a TLT in a patient with a severe M. Bechterew and respiratory failure due to a Guillain-Barré-syndrome. This patient was at high risk for operative complications during a conventional surgical tracheostomy due to his underlying diseases.

Aged↗
PubMed1999

Desflurane and isoflurane improve neurological outcome after incomplete cerebral ischaemia in rats.

We have investigated the effects of isoflurane and desflurane on neurological outcome in a rat model of incomplete cerebral ischaemia. We studied 40 non-fasted male Sprague-Dawley rats, anaesthetized, intubated and ventilated mechanically with isoflurane and nitrous oxide in oxygen (FlO2 0.3). Arterial and venous catheters were inserted for measurement of arterial pressure, drug administration and blood sampling. A biparietal electroencephalogram (EEG) was recorded continuously using subdermal platinum electrodes. At completion of surgery, administration of isoflurane was discontinued (with the exception of those animals receiving isoflurane as treatment) and rats were allowed an equilibration period of 30 min according to the following procedure: group 1 (n = 10), 66% nitrous oxide in oxygen and fentanyl (bolus 10 micrograms kg-1 i.v. followed by infusion at a rate of 25 micrograms kg-1 h-1); group 2 (n = 10), 1.0 MAC of isoflurane in oxygen (FlO2 0.3) and air; groups 3 and 4 (n = 10 per group), 1.0 MAC or 1.5 MAC of desflurane in oxygen (FlO2 0.3) and air, respectively. Ischaemia was produced by combined unilateral common carotid artery ligation and haemorrhagic hypotension to 35 mm Hg for 30 min. Functional neurological deficit was evaluated for 3 days after cerebral ischaemia. At baseline, brain electrical activity was higher with fentanyl-nitrous oxide, 1.0 MAC of isoflurane and 1.0 MAC of desflurane (groups 1-3) compared with 1.5 MAC of desflurane (group 4). Neurological outcome was improved in isoflurane and desflurane anaesthetized animals (groups 2-4), regardless of the concentration used compared with fentanyl-nitrous oxide anaesthesia (group 1). The increase in plasma epinephrine and norepinephrine concentrations during ischaemia was significantly higher in fentanyl-nitrous oxide anaesthetized animals (group 1) compared with animals who received volatile anaesthetics (groups 2-4). These data suggest that cerebral protection produced by isoflurane and desflurane appears to be related to reduction in sympathetic activity rather than suppression of cerebral metabolic rate.

Anesthetics, Inhalation↗
PubMed1998

[Sevoflurane in elderly patients].

An ideal anaesthetic should allow rapid, pleasant, and predictable induction, maintenance and emergence from anaesthesia. Little information is available about sevoflurane use in elderly patients. The pharmacological profile of sevoflurane may be advantageous in geriatric patients because low solubility in the blood is a prerequisite for rapid changes in anaesthetic depth. In addition, the pharmacological profile of sevoflurane may help to reduce the total amount of drug required. Using volatile anaesthetics with low blood solubility and rapid clearance may help in an early postoperative assessment of the neurological status. Because geriatric patients show a higher intraoperative variability of haemodynamic parameters when compared to younger patients a drug such as sevoflurane with rapid uptake and elimination may be advantageous for treatment of hyper- and hypotensive states. As a consequence, the need for vasoactive drugs may be reduced. Recovery from sevoflurane anaesthesia is faster when compared with isoflurane. However, there is still controversy if the occurrence of postoperative cognitive and mental impairment is reduced in elderly patients if drugs with fast elimination characteristics are use. Few data are available on the use of sevoflurane in geriatric patients with renal impairment. Further studies are needed to clarify if the administration of sevoflurane is safe in this population of patients.

Aged↗
PubMed1998

[Tooth injury during intubation--diagnostic and therapeutic aspects].

This study analysis 16 cases of dental injuries occurring during endotracheal intubation. The overall rate was 1 out of 6000 cases of intubation. As expected, the upper jaw teeth are most often involved. Partial dislocations were the most common lesion, together with dental fractures. A well-documented dental evaluation before delivery of anesthetics and appropriate precautions and protective devices during intubation will prevent most dental trauma related to endotracheal intubation. Also, early use of dental and risk management services often will ensure timely resolution of such problems.

Humans↗
PubMed1997

Changes in tumor oxygenation during a combined treatment with fractionated irradiation and hyperthermia: an experimental study.

PURPOSE: To determine the influence of adjuvant hyperthermia on the oxygenation status of fractionated irradiated tumors. METHODS AND MATERIALS: Oxygen partial pressure (pO2) in rat rhabdomyosarcomas (R1H) was measured sequentially at weekly intervals during a fractionated irradiation with 60Co-gamma-rays (60 Gy/20f/4 weeks) in combination with local hyperthermia (8 f(HT) at 43 degrees C, 1 h/4 weeks). Tumors were heated twice weekly with a 2450 MHz microwave device at 43 degrees C, 1 h starting 10 min after irradiation. The pO2 measurements (pO2-histograph, Eppendorf, Germany) were performed in anesthetized animals during mechanical ventilation and in hemodynamic steady state. All tumor pO2 measurements were correlated to measurements of the arterial oxygen partial pressure (paO2) determined by a blood gas analyzer. RESULTS: The oxygenation status of R1H tumors decreased continuously from the start of the combined treatment, with increasing radiation dose and number of heat fractions. In untreated controls a median tumor pO2 of 23 +/- 2 mmHg (mean +/- SEM) was measured. Tumor pO2 decreased to 11 +/- 2 mmHg after 30 Gy + 4 HT (2 weeks), and to 6 +/- 2 mmHg after 60 Gy + 8HT (4 weeks). The increase in the frequency of pO2-values below 5 mmHg and the decrease in the range of the pO2 histograms [delta p(10/90)] further indicated that tumor hypoxia increased relatively rapidly from the start of combined treatment. After 60 Gy + 8HT 48 +/- 5% (mean +/- SEM) of the pO2-values recorded were below 5 mmHg. CONCLUSIONS: These findings suggest that adjuvant hyperthermia to radiotherapy induces greater changes in tumor oxygenation than radiation alone [cf. (39)]. This might be of importance for the temporary application of hyperthermia in the course of a conventional radiation treatment.

Animals↗
PubMed1997

[Ketamine racemate and S-(+)-ketamine. Cerebrovascular effects and neuroprotection following focal ischemia].

The phencyclidine derivative ketamine is a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist with the thalamo-neocortical projection system as the primary site of action. Racemic ketamine consists of the enantiomers S(+)-ketamine and R(-)-ketamine. Racemic ketamine has never been considered an adequate anaesthetic agent in neurosurgical patients since it produces regionally specific stimulation of cerebral metabolism (CMRO2) and increases cerebral blood flow (CBF) and intracranial pressure (ICP). However, recent experiments suggest that both tracemic ketamine and S(+)-ketamine may reduce infarct size in animal models of incomplete cerebral ischaemia and brain injury. This experimental protective effect appears to be related to decreases in Ca++ influx and maintenance of brain tissue magnesium levels due to NMDA and quisqualate receptor blockade by ketamine. Studies in dogs have shown that racemic ketamine (2.0 mg/kg) increases CBF in the presence of the cerebral vasodilator N2O. In contrast, studies in rats without background anaesthesia showed increases in CBF after racemic ketamine (100 mg/kg i.p.). This suggests that the cerebrovascular effects of racemic ketamine are related to the pre-existing cerebrovascular tone induced by background anaesthetics. Cerebrovascular CO2 reactivity was maintained regardless of the baseline cerebrovascular resistance. There are several mechanisms by which racemic ketamine may increase CBF. It induces dose-dependent respiratory depression with consequent mild hypercapnia in spontaneously ventilating subjects. This produces vasodilation due to the intact cerebrovascular CO2 reactivity. Racemic ketamine also induces regional neuroexcitation, which leads to stimulation of cerebral glucose consumption in the limbic, extrapyramidal, auditory, and sensory-motor systems. This regional neuroexcitation with increased CMRO2 produces increases in CBF that can be blocked by infusion of barbiturates or benzodiazepines. However, increases in CBF with racemic ketamine (1 mg/kg) may also occur during normocapnia and without changes in CMRO2. This effect is related to some additional direct cerebral vasodilating potency of racemic ketamine based on a mechanism involving blockade of Ca++ channels. The effects of racemic ketamine on CBF autoregulation have not been investigated systematically. However, studies in rats have shown that CBF autoregulation was maintained with low- and high-dose S(+)-ketamine. Infusion of racemic ketamine alters intracranial volume and ICP. Studies in spontaneously ventilating pigs with and without intracranial hypertension have shown that racemic ketamine (0.5-5.0 mg/kg) produces increases in PaCO2 and ICP. In contrast, identical experiments with mechanical ventilation and controlled PaCO2 showed no changes in ICP following racemic ketamine infusion. This implies that increases in ICP are related to inadequate ventilation with consecutive hypercapnia and increases in intracranial blood volume. However, mechanical ventilation may not be sufficient to control ICP following racemic ketamine. Experiments in mechanically ventilated dogs indicate that racemic ketamine (2 mg/kg) increases cerebral blood volume and ICP even in the presence of normoventilation, a response that is reversible by hyperventilation or the administration of diazepam. Studies in patients have shown that racemic ketamine (2.0 mg/kg) reduces CBF in the presence of cerebral vasodilators like halothane or N2O. In contrast, studies in unanaesthetised humans showed increases in CBF after racemic ketamine (2-3 mg/kg). This observation is consistent with animal studies and suggests that the cerebrovascular effects of racemic ketamine are related to the pre-existing cerebrovascular tone induced by background anaesthetics. Studies in humans with and without intracranial pathology confirm the data from animal experiments. (ABSTRACT TRUNCATED)

Animals↗
PubMed1997

Haemodynamic changes and skeletal muscle oxygen tension during complete blood exchange with ultrapurified polymerized bovine haemoglobin.

OBJECTIVE: The study investigates the effect of continuous blood exchange with ultrapurified, polymerized bovine haemoglobin (UPBH) in comparison to hetastarch on haemodynamics, oxygen transport and skeletal muscle oxygen tension in a canine model. DESIGN: Sixteen anaesthetized beagle dogs underwent haemodilution with lactated Ringer's to a starting haematocrit of 20% followed by progressive blood exchange with 6% hetastarch 200,000/0.5 (HES, group 1) or UPBH (haemoglobin 13 +/- 1 g.dl-1, molecular weight (MW) 32-500,000, group 2) to haematocrit target levels of 15%, 10% and 5% or less. MEASUREMENTS AND RESULTS: Besides haemodynamics, skeletal muscle tissue oxygen tension (tPO2) was measured using a polarographic needle probe. In HES-treated animals, heart rate, cardiac output and blood flow were higher while systemic vascular resistance, systemic and regional arterio-venous oxygen difference (avDO2) and oxygen extraction ratios were lower when compared to the UPBH group. In spite of a higher final haematocrit of 5% in group 1, in comparison to group 2 with 2%, final muscular oxygen uptake (4.7 +/- 4 vs 10.1 +/- 2 ml.min-1) and mean tPO2 (11.8 +/- 2.3 vs 51.1 +/- 2.9 mm Hg) were lower in group 1 than in group 2. While tPO2 histograms were continuously shifted to lower oxygen tensions during progressive haemodilution with HES, UPBH-exchanged animals showed tPO2 histograms shifted to higher values than baseline. CONCLUSION: In spite of vasoconstriction, UPBH provided more haemodynamic stability and enhanced skeletal muscle tPO2 during progressive blood exchange when compared to HES.

Analysis of Variance↗
PubMed1996

The opiate-sparing effect of dipyrone in post-operative pain therapy with morphine using a patient-controlled analgesic system.

OBJECTIVE: To determine whether dipyrone has an opiate-sparing effect in post-operative pain therapy compared with placebo during patient-controlled morphine therapy (PCA) and to compare the effects on analgesia and respiratory and coagulation parameters. DESIGN: Randomized, observer-blind, parallel-group, placebo-controlled study. SETTING: Surgical intensive care unit of a university hospital. PATIENTS: 106 adult patients who were to undergo abdominal or urological surgery under 90-min standardized inhalational anaesthesia were entered and 103 were included in the efficacy analysis (53 on dipyrone, 50 on placebo). INTERVENTIONS: Preprogrammed PCA (0.03 mg morphine/kg per bolus) with either dipyrone (initially 2.0 g i.v. and 1.0 g/2 ml i.v. at 4, 8 and 16 h) or placebo (saline). MEASUREMENTS AND RESULTS: Cumulative morphine consumption was calculated automatically during PCA. Pain intensity and pain relief and the investigator's global assessments of efficacy and tolerability were recorded on five-point verbal rating scales. Vital signs, standard laboratory parameters, respiratory rate, partial pressure of carbon dioxide (PCO2) and of oxygen, partial thromboplastin time (PTT) and Quick values were recorded. Total consumption of opiates in the dipyrone group (median 31.6 mg) was significantly less (p = 0.00015) than in the placebo group (median 50.3 mg), while pain relief (area under the curve) AUC was the same for both PCA+dipyrone (median 4.1) and PCA+placebo (median 3.9). Global assessment of efficacy was good to excellent in more than 90% of cases in both groups. Vital signs, respiratory rate, PCO2, PTT and Quick did not differ between groups. Adverse events were mainly nausea and/or vomiting (dipyrone, n = 4; placebo, n = 1); 1 patient in the placebo group had bradycardia. Three serious adverse events were unrelated to study medication. In 1 patient, the PCA programme malfunctioned and had to be changed. CONCLUSIONS: Concomitant administration of dipyrone with on-demand morphine (PCA) reduces opiate consumption while maintaining post-operative pain relief with a low incidence of side-effects.

Adult↗
PubMed1996

[Acute effects of complete blood exchange with ultra-purified hemoglobin solution or hydroxyethyl starch on liver and kidney in the animal model].

OBJECTIVE: The present animal study investigates the influence of an acute and almost complete isovolaemic haemodilution with a new ultrapurified polymerized bovine haemoglobin (UPBH) on hepatic and renal function and histology in comparison to hydroxyethylstarch (HES). METHODS: Eighteen anaesthetized dogs underwent progressive isovolaemic haemodilution with either HES (group 1) or UPBH (group 2) to haematocrit target levels of 15, 10 and < 5%. Haemodynamics, arterial and mixed-venous blood gases and blood chemistry were determined at each measurepoint. With a haematocrit value < 5%, biopsies were taken from the liver and kidneys and prepared for light and electron microscopic analysis. One dog without haemodilution figured as control animal. Statistical analysis was performed using ANOVA, with p < 0.05 considered significant. RESULTS: In group 1, the cardiac output was increased in parallel to a decreasing vascular resistance, while in group 2 haemodynamic parameters remained unchanged. In group 1, avDO2 and final DO2 and VO2 were decreased. In contrast, avDO2 and oxygen extraction ratio were increased, while VO2 remained stable under decreasing DO2 in group 2. In both groups, coagulation values and blood chemistry showed dilution dependent changes. Colloid osmotic pressure and plasma viscosity were increased in both groups but COP was higher in group 1 compared to group 2. A lower urine output in comparison to group 1 and a maximal concentration of 0.27 g/dl of free haemoglobin in urine were seen in group 2. Liver biopsies showed no severe histological changes in both groups. Renal histology revealed severe alterations of proximal tubules after haemodilution with HES. In contrast, no histological indications for acute toxic or ischaemic lesions in the kidneys were seen after UPBH treatment. CONCLUSION: The high degree of purification and polymerization of bovine haemoglobin associated with adequate tissue oxygenation by increased oxygen extraction resulted in normal histological and functional findings after acute and almost complete blood exchange with UPBH. In contrast, HES-treated animals showed severe histological changes of renal tubuli caused by isovolaemic anaemia.

Animals↗
PubMed1995

Tumor oxygenation in a transplanted rat rhabdomyosarcoma during fractionated irradiation.

PURPOSE: To quantify the changes in tumor oxygenation in the course of a fractionated radiation treatment extending over 4 weeks. METHODS AND MATERIALS: Rhabdomyosarcomas R1H of the rat were irradiated with 60Co-gamma-rays with a total dose of 60 Gy, given in 20 fractions over 4 weeks. Oxygen partial pressure (pO2) in tumors was measured at weekly intervals using polarographic needle probes in combination with a microprocessor-controlled device (pO2-Histograph/KIMOC). The pO2 measurements were carried out in anesthetized animals under mechanical ventilation and in respiratory and hemodynamic steady state. Tumor pO2 values were correlated to the arterial oxygen pressure paO2, arterial pCO2, and pH determined with a blood gas analyzer. RESULTS: Tumor oxygenation did not change significantly during the 3 weeks of irradiation (up to 45 Gy), from a median pO2 of 23 +/- 2 mmHg in untreated controls to 19 +/- 4 mmHg after the third week. The decrease of the number of pO2 values between 0 and 5 mmHg indicated that an improved oxygenation in the tumors occurred. However, with increasing radiation dose (fourth week, 60 Gy) a significant decrease in tumor oxygenation to a median pO2 of 8 +/- 2 mmHg and a rapid increase in the frequency of pO2 values (35 +/- 4%) between 0 and 5 mmHg was found. CONCLUSION: Improved oxygenation in rhabdomyosarcomas R1H was only present in the early phase of the fractionated irradiation. Radiation does above 45 Gy led to a considerable decrease of tumor oxygenation in the later phase of irradiation.

Animals↗