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Biomedical subjects

M Ibsen

Publications and source records attributed to M Ibsen.

17 recordsLinked to original sources
PubMed2006

High-power continuous-wave cladding-pumped Raman fiber laser.

We demonstrate a high-power single-mode cladding-pumped Raman fiber laser. The Raman fiber laser consists of a 1.2 km long germanium-doped double-clad fiber in a linear cavity, which is spliced to a single-mode fiber. The laser is end pumped by a multimode erbium-ytterbium-doped fiber, which is coupled to the inner cladding of the Raman fiber. The embedded core was designed to be single mode at the Raman Stokes wavelength, and up to 10 W of power was obtained at 1660 nm from the single-mode fiber end. The laser has a slope efficiency of 67% and a threshold of 6.5 W.

Journal Article↗
PubMed2002

Plasma cholinesterase activity and duration of action of mivacurium in phenotypically normal patients.

BACKGROUND: The short duration of action of mivacurium is due to its rapid hydrolysis by plasma cholinesterase (pChe). In patients with normal phenotype, low pChe activity because of, for instance, disease or intake of drugs may prolong the duration of action of mivacurium. The purpose of this study was to evaluate the relationship between pChe activity and the duration of action of mivacurium 0.2 mg/kg in phenotypically normal patients. MATERIAL: Forty-three adult patients with normal pChe phenotype and low or normal pChe activity, undergoing a variety of surgical procedures were included in the study with their informed consent and Ethics Committee approval. The neuromuscular block was monitored using TOF stimulation every 12 s and mechanomyography. The time to reappearance of the first response to TOF stimulation was measured. RESULTS: The patients pChe activities ranged from 45 to 1272 U/l (normal range 660-1620 U/l) and the time to first response to TOF from 8.1 to 62.7 min. An inverse relationship between enzyme activity and duration of action of mivacurium was found. The relationship was described by the equation: log10 (time) =alpha- beta log10 (pChe), where alpha (SD) is 2.547 (0.186) and beta (SD) 0.454 (0.069). CONCLUSION: In patients with phenotypically normal pChe, prediction of the duration of action of mivacurium is possible from the patients actual pChe activity. In patients with pChe activities below the normal range, the time to reappearance of the first response to TOF stimulation may vary from 10 to 180 min Only patients with pChe activities <220 U/l had a significantly prolonged duration of action of mivacurium.

Adult↗
PubMed2001

Distributed-feedback fiber laser sensor for simultaneous strain and temperature measurements operating in the radio-frequency domain.

Radio-frequency (rf) beat frequencies between two longitudinal modes and two polarization modes of a birefringent dual-longitudinal-mode moiré distributed-feedback fiber laser are employed to measure strain and temperature simultaneously. Operating entirely in the rf domain, this approach potentially allows one to employ low-cost and precise rf measuring techniques. A strain-temperature cross sensitivity of the strain- and the thermo-optic coefficients, which can be neglected in wavelength-based grating sensors, has been observed. The achieved sensor accuracy was +/-15 microepsilon and +/-0.2 degrees C.

Journal Article↗
PubMed2001

Onset and duration of action of rocuronium--from tracheal intubation, through intense block to complete recovery.

BACKGROUND: The primary objective of this study was to establish the relation between the post tetanic count (PTC) and the time to reappearance of the first response (T1) in train-of-four (TOF) nerve stimulation following rocuronium 0.6 mg/kg, 0.9 mg/kg, and 1.2 mg/kg. The secondary objective was to evaluate the intubation conditions after 1 min. METHODS: One hundred and eight patients were randomised to one of three doses of rocuronium: 0.6, 0.9 or 1.2 mg/kg. Tracheal intubation was performed at 60 s by a blinded investigator. During propofol, fentanyl, midazolam anaesthesia the neuromuscular block was monitored by mechanography using TOF stimulation every 12 s. At 6 min intervals, a tetanic stimulation (50 Hz) was applied for 5 s preceded and followed by a 30 s period of 1 Hz stimulation until the reappearance of T1. RESULTS: There was a significant difference in recovery following the high dose and the two lower doses. The relation between time (min) to reappearance of T1 (t) and PTC can be expressed as follows: t(0.6 and 0.9 mg/kg)(min)=18.8-6.46 PTC and t(1.2 mg/kg)(min)=26.1-9.12 PCT. T1 was seen at a mean PTC level of 8 or 9 in all three groups. The intubation conditions were graded as excellent or good in all patients except in two patients following the 0.6 mg/kg dose of rocuronium. CONCLUSION: The PTC method can be used to predict the time to first response to TOF nerve stimulation during intense rocuronium induced neuromuscular blockade. The relation between PTC and the time to T1 was prolonged after 1.2 mg/kg compared with 0.6 mg/kg and 0.9 mg/kg. No further improvement in intubation conditions at 60 s was evident by increasing the rocuronium dose from 0.9 mg/kg to 1.2 mg/kg.

Adolescent↗
PubMed1996

[Large epiglottic lipoma. Intubation method for large tumors in the pharynx and larynx].

Large benign tumours in the aperture of the larynx are uncommon, and they are especially rare on the epiglottis. They are, however, important as they may cause fatal airway obstruction particularly at induction of general anaesthesia. We present a patient with a large lipoma originating in the vallecula epiglottica and the lingual surface of the epiglottis. The difficulties involved in tracheal intubation and possible solutions are discussed. In this case intubation was performed under local anaesthesia with the patient fully awake. A commissure laryngoscope was used for visualisation of the laryngeal inlet and a flexible bougie was inserted into the trachea. After removal of the laryngoscope a 7 mm ID endotracheal tube was advanced over the bougie into the trachea. After securing the airway in this way general anaesthesia was induced and the table tennis ball sized lipoma was uneventfully removed.

Epiglottis↗
PubMed1994

Preoperative infiltration of the surgical area enhances postoperative analgesia of a combined low-dose epidural bupivacaine and morphine regimen after upper abdominal surgery.

In a randomized, blinded trial we assessed the value of adding preoperative infiltration of the surgical area with bupivacaine to a low dose epidural regimen for postoperative pain treatment. Forty-nine patients scheduled for major upper abdominal surgery during combined thoracic epidural (bupivacaine + morphine) and general anaesthesia were studied. Postoperative analgesia was epidural bupivacaine 10 mg/hr-1 + morphine 0.2 mg/hr-1 for 72 h. The patients randomly received preoperative infiltration of the surgical area with bupivacaine 0.25%, 40 ml (group I); or no infiltration (group II). Pain was evaluated at rest, during cough and during mobilization six and eight h after start of surgery, and at 8 a.m. and 4 p.m. on the following days until 72 h after start of surgery. The sensory level of analgesia was evaluated by pin prick. We found no difference between the two groups during rest and cough. However, during mobilization group I had lower pain scores compared to group II (P < 0.05). There was a significant reduction in the need for supplemental intramuscular morphine in the treatment group compared to the control group (P < 0.05). Thus an enhanced analgesic effect was demonstrated by adding preoperative infiltration of the surgical area with local anaesthetic to a low dose epidural bupivacaine/morphine regimen after upper abdominal surgery.

Abdomen↗
PubMed1993

Accuracy of 94 anaesthetic agent vaporizers in clinical use.

Using the Brüel & Kjaer Anaesthetic Gas Monitor type 1304, we have monitored the output of 94 anaesthetic agent vaporizers (Fluotec 3:58, Enfluratec 3:24, Isotec 3:12), in seven departments of anaesthesia, at different dial settings and flow rates. The range of output, for one type of vaporizer and dial setting (flow: 6 litre min-1) was largest with the Fluotec 3 (0.85-1.55% when dial set to 1%) and smallest with the Isotec 3 (0.85-1.15% when dial set to 1%). In determining the number of vaporizers with unacceptable inaccuracy, we applied acceptance limits of +/- 15% relative on each vaporizer and each dial setting. Using a flow of oxygen 6 litre min-1 17% of Fluotec 3.8% of Isotec 3 and 71% of Enfluratec 3 vaporizers had outputs outside those limits. Even when some specific conditions (vaporizers giving output beyond the limits at any two or more dial settings; output beyond the limits in the clinically relevant range (0.5-2%)) were added, a substantial number of vaporizers did not perform within the limits. We found a significantly greater accuracy of the vaporizers after 3-monthly calibration checks (P < 0.05) compared with vaporizers undergoing service and calibration only annually. Using a questionnaire, we found that fewer than 30% of the anaesthetists using the vaporizers would accept aberrance beyond +/- 10% relative of the dial setting.

Anesthesia, Inhalation↗
PubMed1993

Psychomimetic reactions after neurolept and propofol anaesthesia.

The purpose of this study was to compare the frequency of psychomimetic reactions after 24 h and 3 months following total intravenous anaesthesia with propofol and neurolept anaesthesia. Forty otherwise healthy female patients were randomly divided into two groups. All were undergoing elective gynaecological laparotomy for non-malignant disease. Nineteen patients were anaesthetized with droperidol, fentanyl, pancuronium, N2O/O2. Twenty patients received total intravenous anaesthesia with propofol, fentanyl and pancuronium. Twenty-four hours after the anaesthesia the patients were interviewed about their subjective experiences of anaesthesia and recovery. Three months after the operation the patients were sent a questionnaire concerning ability to work, sleep and memory disorders. After 24 h the anaesthesia was judged as good by 18 patients receiving propofol and 13 patients receiving NLA (n.s.). The recovery was judged as good by 16 patients in the propofol group and six patients in the NLA group (P < 0.05). Locked-in feelings were reported by one patient in the propofol group and ten patients in the NLA group (P < 0.01). Impairment of memory was reported by one patient in the propofol group and seven patients in the NLA group (P < 0.01). A questionnaire used after 3 months was answered by 18 patients in the propofol group and 17 patients in the NLA group. There were few complaints, and no differences were found between the two groups. In conclusion, total intravenous anaesthesia with propofol seems more acceptable than anaesthesia with neurolept as judged by the patients 24 h after anaesthesia. There were no differences between the two groups concerning psychomimetic reactions 3 months after anaesthesia.

Adult↗
PubMed1993

Low-flow isoflurane-nitrous oxide anaesthesia offers substantial economic advantages over high- and medium-flow isoflurane-nitrous oxide anaesthesia.

Isoflurane consumption was studied for three different fresh gas flows in patients scheduled for major elective abdominal, urological or gynaecological surgery under general anaesthesia with an expected duration of 2 h or more. Thirty patients were randomly assigned to either high-flow anaesthesia using a partial rebreathing system without carbon dioxide absorption (Mapleson D) or medium- or low-flow anaesthesia using a circle system with carbon dioxide absorption. Patients were anaesthetised with isoflurane in 40% oxygen and 60% nitrous oxide. The amount of isoflurane consumed was measured with a precision scale. The total consumption of liquid isoflurane (mean +/- s.d.) during the first 2 h was 40.8 +/- 12.2 ml in the high-flow group, 18.5 +/- 5.4 ml in the medium-flow group and 7.9 +/- 2.2 ml in the low-flow group. The corresponding cost of isoflurane for the three groups was 214 Danish kroner (DKK) (19.5 pounds), 97 DKK (8.8 pounds) and 42 DKK (3.8 pounds), respectively. The calculated total cost of anaesthetics was 286 DKK (26 pounds), 155 DKK (14.1 pounds) and 91 DKK (8.3 pounds), respectively. In conclusion, low-flow isoflurane-nitrous oxide anaesthesia offers substantial economic advantages over high- and medium-flow isoflurane-nitrous oxide anaesthesia.

Adult↗
PubMed1987

Effect of chlorpromazine on drug absorption and gastric emptying in man.

In a double-blind study the effect of a single IV dose (25 mg) of chlorpromazine on gastric emptying, as determined by the rate of paracetamol absorption, was measured in seven healthy volunteers. Each volunteer acted as his/her own control. There was no significant difference between the maximum paracetamol concentration, the time to reach the plasma maximum concentration, and the area under the plasma concentration time curve from 0-120 minutes on the two occasions, indicating unchanged gastric emptying after administration of chlorpromazine.

Acetaminophen↗
PubMed1987

The effect of spinal analgesia and surgery on peroperative drug absorption and gastric emptying in man.

Paracetamol 20 mg kg-1 dissolved in 200 ml of water was given by mouth to seven patients undergoing minor orthopaedic surgery in spinal analgesia, and again 2 weeks later. The rate of paracetamol absorption was significantly delayed by spinal analgesia and surgery, indicating an inhibition of peroperative drug absorption and gastric emptying. The effect of spinal analgesia on gastric emptying was not able to normalize the delayed peroperative gastric emptying produced by surgery, and suggests that surgery is an important factor in peroperatively delayed gastric emptying.

Acetaminophen↗
PubMed1986

The relationship between gastric emptying of semisolids and paracetamol absorption.

The relationship between gastric emptying rate of semisolid Tc-99m labelled Chelex-100 resin/oatmeal and paracetamol absorption was determined simultaneously in seven healthy volunteers. There was no significant correlation between the half-time of gastric emptying and the time of the peak serum paracetamol concentration. There was no significant correlation between the area under the serum paracetamol concentrations at 60 and 90 min and the % meal emptied in 60 and 90 min respectively. Three subjects showed a lag phase in gastric emptying pattern, while the other four showed the emptying curves without evidence of a delayed phase of emptying. Individual values of gastric emptying determined by the methods varied widely.

Acetaminophen↗
PubMed1985

Abstaining from cigarette smoking has no major effect on gastric emptying in habitual smokers.

The rate of liquid-phase gastric emptying was determined in seven smokers from the rate of paracetamol absorption after abstaining overnight from cigarettes, and again after smoking two cigarettes within 30 min. There were no significant differences between the maximum paracetamol concentration, the time to reach maximum paracetamol concentration, and the area under the plasma concentration-time curve from 0 to 120 min on the two occasions, indicating that abstaining from cigarette smoking had no major effect on gastric emptying in habitual smokers.

Acetaminophen↗
PubMed1985

Effect of diazepam on drug absorption and gastric emptying in man.

Paracetamol 20 mg kg-1 dissolved in 200 ml of water was given by mouth to seven healthy volunteers, together with a single i.v. dose of diazepam 0.2 mg kg-1 or saline 0.04 ml kg-1. This study demonstrated that the rate of paracetamol absorption was not significantly changed by diazepam, indicating that there was no delay in gastric emptying attributable to diazepam per se.

Acetaminophen↗
PubMed1985

Buprenorphine delays drug absorption and gastric emptying in man.

The aim of the present study was to investigate the effects of buprenorphine on drug absorption and gastric emptying in man, using paracetamol absorption as an index of gastric emptying rate. Paracetamol was given to eight healthy volunteers p.o. together with or without a single i.v. dose of buprenorphine 4 micrograms kg-1 body weight. Nausea occurred in five of the subjects, four subjects vomited and one was excluded due to vomiting during the study period. The mean peak serum paracetamol concentration (Cmax) was significantly (P less than 0.0002) lowered by a factor 3 by buprenorphine, the mean time from administration of paracetamol to its peak concentration (Tmax) was significantly (P less than 0.03) prolonged by a factor 6, and the area under the plasma concentration-time curve from 0 to 120 min was significantly (P less than 0.00006) reduced by a factor 3. This demonstrates a marked inhibition of the rate of paracetamol absorption, indicating a clinically important reduction of gastric emptying following administration of buprenorphine.

Acetaminophen↗