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Biomedical subjects

S Armbruster

Publications and source records attributed to S Armbruster.

16 recordsLinked to original sources
PubMed2005

Effect of Xenon on elevated intracranial pressure as compared with nitrous oxide and total intravenous anesthesia in pigs.

BACKGROUND: Xenon in low concentrations has been investigated in neuroradiology to measure cerebral blood flow (CBF). Several reports have suggested that inhalation of Xenon might increase intracranial pressure (ICP) by increasing the cerebral blood flow and blood volume, raising concerns about using Xenon as an anesthetic in higher concentrations for head-injured patients. A porcine study is presented in which the effects of inhaled 75% Xenon on elevated ICP, cerebral perfusion pressure and the efficacy of hyperventilation for ICP treatment were compared with nitrous oxide anesthesia and total intravenous anesthesia (TIVA). METHODS: Twenty-one pentobarbital-anesthetized pigs (age: 12-16 weeks) were randomly assigned to three groups to receive either 4 h of Xenon-oxygen ventilation, nitrous oxide-oxygen ventilation or air-oxygen (75%/25%) ventilation, respectively. After instrumentation for parenchymal ICP measurement and ICP manipulation, an epidurally placed 6-F balloon catheter was inflated until a target ICP of 20 mmHg was achieved. After 4 h of anesthesia hyper- and hypoventilation maneuvers were performed and consecutive ICP and CBF changes were investigated. RESULTS: Intracranial pressure and CBF increased significantly in the nitrous oxide group as compared with the controls. There was no increase of ICP or CBF in the Xenon or control group. Intracranial pressure changed in all three groups corresponding to hyper- and hypoventilation. CONCLUSIONS: During Xenon anesthesia, elevated ICP is not increased further and is partially reversible by hyperventilation. Our study suggests that inhalation of 75% Xenon seems not to be contraindicated in patients with elevated ICP.

Anesthesia, Intravenous↗
PubMed2002

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.

Adjuvants, Anesthesia↗
PubMed2001

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.

Anesthetics, Combined↗
PubMed2001

Analgesic effect of butorphanol and levomethadone in detomidine sedated horses.

The analgesic potency of butorphanol 25 microg/kg bodyweight (BW) and levomethadone 100 microg/kg BW, administered together with detomidine 10 microg/kg BW, was measured in twelve Warmblood horses in a randomized, blinded cross-over study. Detomidine with saline 10 ml 0.9% was used as placebo. The nociceptive threshold was determined using a constant current and a pneumatic pressure model for somatic pair Detomidine alone and in combination with butorphanol or levomethadone caused a significant temporary increase (P < 0.05) of the nociceptive threshold with a maximum effect within 15 min and a return to baseline levels within 90 min. Butorphanol and levomethadone increased the nociceptive threshold and prolonged the duration of anti-nociception significantly from 15 to 75 min (P < 0.05) after drug administration compared with detomidine alone to both test methods. No significant difference between butorphanol and levomethadone was registered. It is concluded that the addition of butorphanol or levomethadone to detomidine increases the nociceptive threshold to somatic pain and prolongs the analgesic effect of detomidine in the horse.

Analgesics, Opioid↗
PubMed1992

Comparison of ketorolac and morphine for postoperative pain after major surgery.

This study was designed to determine the relative analgesic efficacy and safety of single intramuscular injections of ketorolac (10 mg or 30 mg) and morphine (10 mg) in patients of either sex with moderate to severe pain after major surgery. In a single-dose, randomised, double-blind study of parallel design, pain was assessed immediately before injection of test medication and at regular intervals for 8 h thereafter. One hundred and seventeen patients (109 undergoing cardiac surgery; 8 lung surgery) were randomized to one of the three treatment groups. Pain intensity was assessed using a 5-point verbal scale before administration of study drugs. Postadministration, at 30 min and hourly for 8 h, pain intensity and pain relief were assessed, again using the 5-point verbal scale. Additionally, as a measure of analgesia, forced expiratory volume (FEV1) was obtained in all patients. Vital signs including blood pressure, pulse, temperature, respiratory rate and blood gases (PaCO2) were recorded prior to and after study medication. Based on hourly pain intensity differences and hourly pain relief observations, ketorolac 10 mg was generally more effective than morphine 10 mg, and ketorolac 30 mg was generally more effective than ketorolac 10 mg. The results of this study show that ketorolac is an effective and safe (with regard to arterial pressure, blood gases and lung function) analgesic for relief of postoperative pain after major surgery in stable patients. No clinically significant adverse effects occurred during the study. One cannot exclude an influence on patients with organ system dysfunction or on parameters not measured in this study.

Adult↗
PubMed1990

Safety and efficacy of xenon in routine use as an inhalational anaesthetic.

40 patients (24 male, 16 female, aged 21-59 years) of American Society of Anesthesiologists class I or II who were undergoing routine surgery took part in a randomised, double-blind comparison of the anaesthetic efficacy and potency of xenon and nitrous oxide and their effects on the circulatory and respiratory systems. During anaesthesia, for each rise in blood pressure of more than 20% of the preanaesthetic (baseline) value, the patient received 0.1 mg fentanyl. The total amount of fentanyl required per patient was used as an index of the anaesthetic potency of the study gases. Patients in the xenon group required on average only 0.05 mg fentanyl, whereas those in the nitrous oxide group required 0.24 mg fentanyl; the duration of anaesthesia was similar in the two groups. Changes in blood pressure were significantly greater throughout the study in the nitrous oxide than in the xenon group. Thorax-lung compliance fell during the study period in the nitrous oxide group but not in the xenon group. Thus, xenon is a potent and effective anaesthetic which can be safely used under routine conditions.

Adult↗
PubMed1990

Online measurements of SaO2, Ht and Hb using a micro transmission cell.

Recently a Micro Transmission Cell has been developed based on spectrophotometry for in vivo monitoring of SaO2 together with Hb. A study in pigs was performed to compare the cell with standard methods for measuring SaO2, Hb and Ht. The results show that the cell is capable of following the trends of SaO2, Hb and Ht at different Hb concentrations and/or O2 saturations.

Animals↗
PubMed1989

Volume-controlled ventilation with superimposed high frequency ventilation during expiration in healthy and surfactant-depleted pig lungs.

In the healthy and surfactant-depleted lungs of five pigs the influence of different forms of high frequency ventilation superimposed on conventional mechanical ventilation during the expiratory phase of the ventilatory cycle (SHFVE) on gas exchange and cardiocirculatory parameters was investigated. Subsequently the effects of end-expiratory flushing (EF), i.e. cleaning the large airways and connecting tubes from the ventilator free from end-expiratory CO2, with a volume greater than the dead space of the large airways and connecting tubes was investigated. SHFVE and EF resulted in a significant improvement in CO2 elimination in both healthy and surfactant-depleted lungs. Furthermore, in stiff lungs, at a certain level of oxygenation and CO2 elimination, SHFVE produced the lowest peak and mean airway pressure without any additional depression of cardiocirculatory parameters.

Animals↗