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Biomedical subjects

H G Schaefer

Publications and source records attributed to H G Schaefer.

At least 37 records · Page 2Linked to original sources
PubMed1994

Spinal anaesthesia with 29 gauge Quincke point needles and post dural puncture headache in 2,378 patients.

Two thousand three hundred and seventy-eight spinal anaesthetics using a 29 G Quincke point needle were administered in a District Hospital between May 1983 and December 1991. The overall post dural puncture headache rate (PDPH) was 1.2% with a maximum of 2.5% in patients between age 30 and 39. PDPH was related to the experience of using 29 G needles (0.5% in consultants versus 2.0% in trainees, P < 0.05).

Adolescent↗
PubMed1994

Cerebral vasomotor responsiveness to carbon dioxide is preserved during propofol and midazolam anesthesia in humans.

Carbon dioxide reactivity, as measured by transcranial Doppler ultrasonography, was determined during total intravenous anesthesia with propofol or midazolam in comparison with an awake control group. Thirty ASA physical status I neurosurgical patients undergoing lumbar laminectomy participated in the study. In randomized order they were subjected to a CO2 reactivity challenge, either under an intravenous anesthesia technique or in the awake state. CO2 reactivity was calculated in each study group as a relative change in middle cerebral artery (MCA) flow velocity per mm Hg change in end-tidal CO2 (PETCO2) (%/mm Hg). The cerebrovascular response to changes in CO2 was preserved during intravenous anesthesia. There was a significant difference (P < 0.05) in the reactivity slopes between the awake and the anesthetized patients with a small but not significant difference between the propofol and the midazolam group. We conclude that hypocarbia is effective in reducing cerebral blood flow velocity (CBFV) during intravenous anesthesia, either with propofol or midazolam.

Adult↗
PubMed1994

Haemodynamic response to fibreoptic versus laryngoscopic nasotracheal intubation under total intravenous anaesthesia.

Thirty ASA physical status I and II patients scheduled for elective maxillofacial surgery received total intravenous anaesthesia with propofol, fentanyl and atracurium and were randomly allocated to undergo either fibreoptic or orthodox nasotracheal intubation. Haemodynamic responses to intubation were similar for both techniques. The peak values for heart rate and blood pressure after induction were not significantly different from the baseline values for each group. There was no significant difference in the time required to complete intubation. SpO2 and end-tidal CO2 were similar for both techniques.

Adult↗
PubMed1993

Determination of BAY y 3118, a novel 4-quinolone, in biological fluids using high-performance liquid chromatography and photothermal post-column derivatization.

A reversed-phase high-performance liquid chromatographic (HPLC) method that allows the sensitive and selective quantification of a novel 4-quinolone (BAY y 3118, I) in biological fluids is described. After sample dilution with 0.05 M phosphoric acid (plasma) or 0.1 M phosphate buffer pH 7.5 (urine), samples can be directly injected into the HPLC system. Prior to fluorescence detection, I is decomposed to fluorescence compound(s) by post-column derivatization utilizing either photolysis (Beam Boost reaction unit) or a combination of thermolysis and photolysis (laboratory-made post-column reactor). Compared with fluorescence detection alone, derivatization increases the signal intensity (about 80-fold) and the selectivity of the detection significantly. Concentrations down to 0.01 mg/l could be quantified in biological fluids. Only thermolysis was not able to decompose I to fluorescence products. Investigations on the stability of I in plasma and urine demonstrate good stability under the different conditions tested. The method was applied to human plasma and urine samples from a subject after a single oral dose of 100 mg of I.

Anti-Infective Agents↗
PubMed1993

Effect of food on the pharmacokinetics of the active metabolite of the prodrug repirinast.

The effect of food on the pharmacokinetics of the active metabolite of the new antiasthmatic drug repirinast was investigated in two different studies after oral administration of 300 mg of repirinast. In each study, 12 healthy volunteers received the repirinast dose under fasting or fed conditions in a crossover manner. In one study, a high-fat meal (American breakfast) was used and in another study, a low-fat, high-carbohydrate meal (continental breakfast) was used. Concentrations of the active metabolite in plasma and urine were determined by reversed-phase high-performance liquid chromatography with UV detection. After administration of repirinast with a low-fat and a high-fat meal, the relative bioavailability of the active metabolite increased by factors of 1.9 and 2.4, respectively, as expressed by area under the curve of concentration versus time from 0 to 12 h. The amount excreted into urine doubled after drug administration with both types of food and accounted for approximately 8% of the dose under fasting conditions and approximately 16% of the dose under fed conditions. Maximum concentrations in plasma were different between the two studies: mean maximum concentrations in plasma increased by factors of 1.7 and 3.2 after administration of drug with a low-fat (drug intake immediately after breakfast) and a high-fat breakfast (drug intake just before breakfast), respectively, compared with fasting conditions.

Adult↗
PubMed1993

Is normal saline an acceptable alternative to silicone for lubricating fibrescopes?

This article describes a model designed to measure the forces acting on a fibrescope when it is pushed through an endotracheal tube. Lubrication with either silicone or normal saline leads to a reduction in friction forces. Fibrescopes lubricated with normal saline require a larger force to be advanced through endotracheal tubes when compared to silicone; however, the difference is clinically unimportant and is outweighed by the advantageous properties of normal saline. A theoretical model is presented which is in close agreement with experimentally derived data.

Butanes↗
PubMed1992

Pharmacokinetics of the active metabolite of the prodrug repirinast in healthy Caucasian volunteers after a single oral dose.

The pharmacokinetics of BAY w 8199, the active metabolite of the prodrug repirinast (BAY u 2372), has been investigated after oral administration of 150, 300 and 450 mg repirinast to twelve healthy male Caucasians. Plasma BAY w 8199 concentrations were very variable between subjects. The mean peak level (geom.mean; 1s-range) was 0.14 (0.08-0.25), 0.19 (0.13-0.29) and 0.24 (0.14-0.42) mg/l after the 150, 300 and 450 mg doses, respectively. Peak levels were reached 0.5-2.5 h after drug intake. Terminal half-lives were calculated as 5.9 h (150 mg), 8.0 h (300 mg) and 9.8 h (450 mg). The dose proportionality of the plasma profiles of BAY w 8199 and of its excretion in urine was demonstrated by testing several parameters. About 7.4% of each dose (calculated as BAY w 8199) was excreted in urine over 36 h. The renal clearance of about 27 l/h suggests that BAY w8199 is excreted by tubular secretion in addition to glomerular filtration.

Administration, Oral↗
PubMed1992

Perioperative myocardial ischemia in patients undergoing elective hip arthroplasty during lumbar regional anesthesia.

Perioperative myocardial ischemia predicts unfavorable outcomes and occurs in as many as 41% of patients with coronary artery disease or cardiac risk factors undergoing noncardiac surgery. To determine the prevalence of myocardial ischemia, we studied 52 consecutive unselected patients undergoing elective hip arthroplasty during lumbar regional anesthesia. Patients were continuously monitored for 6 days using a three-channel Holter monitor. Ninety-nine episodes of myocardial ischemia occurred in 16 patients (31%), six of whom were considered preoperatively to be at low risk for coronary artery disease. Forty-four percent of the ischemic episodes were preceded or accompanied by a heart rate greater than or equal to 100/min and 56% by a heart rate greater than or equal to 90 beats/min. Ninety-six percent of the ischemic episodes were clinically silent, and 82% were not related to patient care events. Thirteen episodes of myocardial ischemia occurred preoperatively, 1 intraoperatively, and 85 postoperatively. The incidence of postoperative ischemic episodes showed a circadian variation: 44% occurred between 6 AM and noon, 33% between noon and 6 PM, 17% between 6 PM and midnight, and 6% between midnight and 6 AM. Six adverse cardiac events occurred during hospitalization (three of the six among patients with perioperative ischemia) and an additional four events during a follow-up period of 12 months (all four events occurred among patients with perioperative ischemia). Patients with perioperative myocardial ischemia had a relative risk of 2.6 (95% confidence interval 1.3-5.2) to develop an adverse cardiac event postoperatively.

Aged↗
PubMed1992

Failure of continuous three-channel Holter monitoring to detect acute peri-operative myocardial infarction.

Continuous peri-operative three-channel Holter monitoring in a 70-year-old patient undergoing elective hip arthroplasty failed to show onset and progression of a lethal postoperative myocardial infarction, which was clearly visible in a 12-lead electrocardiogram. The modified bipolar leads used for Holter monitoring differed from the corresponding leads of the 12-lead electrocardiogram. The limitations of Holter monitoring applied to clinical management and research are highlighted.

Aged↗
PubMed1992

Cardiovascular effects of fibreoptic oral intubation. A comparison of a total intravenous and a balanced volatile technique.

The cardiovascular response to fiberoptic oral intubation under total intravenous anaesthesia with propofol or a balanced volatile technique with thiopentone/enflurane was compared in 50 patients of physical status ASA 1 and 2 who were scheduled for elective ear, nose and throat surgery. Patients were randomly assigned to receive propofol or enflurane. There was no significant difference between the two anaesthetic techniques in haemodynamic profile either before, during or after fibreoptic intubation (the study design was adequate to detect a 20% difference with > 90% statistical power), in incidence of postoperative sore throat or in time taken for intubation. In no patient did the oxygen saturation decrease to below 95% or the CO2 tension exceed 5.8 kPa.

Adult↗
PubMed1992

Art and anaesthesia.

Explore the source record for details and available documents.

Anesthesia, Intravenous↗
PubMed1992

Dreaming and anaesthesia: total i.v. anaesthesia with propofol versus balanced volatile anaesthesia with enflurane.

Sixty consecutive ASA Grades I and II patients scheduled for elective ear, nose and throat surgery were randomly assigned to receive either total i.v. anaesthesia with propofol ('propofol group') or 'balanced technique' with thiopentone induction followed by N2O and enflurane. Patients were asked whether they had experienced dreams immediately after extubation when verbal communication was established, in the recovery room and in the ward on the evening of the day of surgery. Thirteen patients in the propofol group (43%) and three patients in the enflurane group (10%) reported dreaming (P less than 0.05) when asked as soon as verbal communication was established. In the recovery room and in the ward only three patients of the propofol group (10%) and one patient in the enflurane group (3%) remembered that they had been dreaming (NS). To avoid underestimating the frequency of peri-operative dreaming, post-operative interviews should take place as soon as possible after conversing is possible.

Adult↗
PubMed1991

Comparison of orthodox with fibreoptic orotracheal intubation under total i.v. anaesthesia.

Fibreoptic orotracheal intubation was compared with orthodox laryngoscopy and tracheal intubation using a total i.v. technique with propofol in 60 ASA I and II patients. There was no significant difference between the two techniques in haemodynamic profile (before, during and following the intubation procedure) and incidence of postoperative sore throat. Minimal oxygen saturation was 96% during the study; maximal end-tidal PCO2 after intubation was 5.4 kPa. Intubation time was faster (P less than 0.01) in the orthodox group (30.7 (SEM 2.3) s) than in the fibreoptic group (52.7 (4.8) s).

Anesthesia, Intravenous↗
PubMed1990

Simultaneous determination of propranolol and 4-hydroxypropranolol enantiomers after chiral derivatization using reversed-phase high-performance liquid chromatography.

A reversed-phase high-performance liquid chromatographic method is described, which allows the simultaneous quantification of propranolol and 4-hydroxypropranolol enantiomers in human plasma. After extraction from plasma (pH 10.5) using ethyl acetate, the enantiomers are derivatized with R-(+)-phenylethylisocyanate as chiral derivatization reagent and triethylamine as basic catalyst in chloroform. Ascorbic acid is used to prevent 4-hydroxypropranolol from oxidation during the extraction. Chromatographic separation on ODS columns and fluorescence detection (228 nm/greater than 340 nm) allows sensitive quantitation of all derivatives. Incubation of the plasma samples with beta-glucuronidase/arylsulfatase and the use of the specific beta-glucuronidase inhibitor saccharo-1,4-lactone allows the quantitation of both the sulfate and glucuronide conjugates of the enantiomers. The method was applied to human plasma samples from a subject after administration of 60 mg racemic propranolol three times daily.

Animals↗
PubMed1990

Effects of truncal vagotomy and partial gastrectomy on the pharmacokinetics of propranolol enantiomers in dogs.

The effect of partial gastrectomy on the pharmacokinetic parameters of (+)- and (-)-propranolol were investigated in six dogs. (+/-)-Propranolol (3 mg/kg body weight) was administered orally before and after surgery and the plasma concentrations of (+)- and (-)-propranolol were determined using an indirect enantioseparation technique. There were significant differences (p less than or equal to 0.05, paired t-test) in the area under the concentration-time curves (AUCs) and the maximum plasma concentration (Cmax) between (+)- and (-)-propranolol. The ratio AUC(+):AUC(-) was 1.73 +/- 0.28. These differences between the enantiomers remained unchanged after surgery. Other pharmacokinetic parameters showed no stereoselectivity. After partial gastrectomy, there was a slight, but nonsignificant decrease in time to reach maximum plasma concentration (tmax) and in the absorption half-life for both enantiomers. The maximum plasma concentration increased slightly. The elimination half-life and the mean residence time remained unchanged before and after surgery. Therefore, it is unlikely that there are any clinically relevant changes in the pharmacokinetics of (+)- and (-)-propranolol after partial gastrectomy.

Animals↗