Harald Johnsen

Perfusion abnormalities in pulmonary embolism studied with perfusion MRI and ventilation-perfusion scintigraphy: an intra-modality and inter-modality agreement study

To compare perfusion magnetic resonance imaging (MRI) and ventilation‐perfusion scintigraphy (V‐P scan) in the study of perfusion abnormalities in pulmonary embolism (PE) and to compare the PE results to the findings previously reported for pneumonia and chronic obstructive pulmonary disease (COPD), in terms of perfusion abnormalities.

Gut luminal microdialysis of glycerol as a marker of intestinal ischemic injury and recovery

Objective:To evaluate microdialysis as a method to assess different degrees of intestinal damage and recovery during ischemia and reperfusion; to evaluate information obtained from microdialysis catheters in the peritoneum, the gut wall, and the gut lumen. Design:Randomized, controlled animal experiment. Setting:University laboratory animal center. Subjects:Twenty-seven domestic pigs. Interventions:The superior mesenteric artery was cross-clamped for 60 mins (n = 14) or 120 mins (n = 10) followed by 2 or 4 hrs of reperfusion. Three pigs served as controls. Measurements and Main Results:Intestinal mucosal integrity was assessed by morphometry, adenosine triphosphate in the gut wall, and permeability of 14C-polyethylene glycol. Lactate, glycerol, pyruvate, and glucose were measured by microdialysis. Changes in adenosine triphosphate, permeability, or lactate did not correlate to different extents of intestinal damage caused by 60 or 120 mins of ischemia. During the reperfusion period, pigs with 60 mins of intestinal ischemia showed a faster recovery of these variables than pigs with 120 mins of intestinal ischemia. Glycerol increased with increasing duration of the ischemic insult. After 60 mins of intestinal ischemia, glycerol in the gut lumen decreased toward baseline but remained high after 120 mins of intestinal ischemia. There was a good correlation between gut luminal glycerol and recovery of mucosal damage throughout the reperfusion period. In the peritoneal cavity, both glycerol and lactate decreased to baseline relatively shortly after onset of reperfusion independent of the duration of intestinal ischemia. Conclusions:Microdialysis of glycerol provides information about the extent and severity of intestinal damage after ischemia and about the ensuing recovery. The gut lumen is to be preferred as a site for placement of microdialysis catheters.

Senile cataract and ascorbic acid loading

Abstract Serum, aqueous humour, and lens ascorbic acid levels were determined by high‐performance liquid chromatography in cataract‐, closed‐angle glaucoma‐, and aphakic patients. The total number of 108 patients were subdivided into different groups. In several groups the pre‐operative serum and aqueous amounts were tested, whereafter patients in some groups were loaded with ascorbic acid orally. Finally, a second test was performed on samples taken during operation. It turned out that the ascorbic acid concentration mechanism in cataractous eyes needed more than 12 h for maximum reaction on the loading stimulus. The slow reaction is surprising compared to other species, and it may reflect an affection of the secretory process itself in this disease.

Ascorbic acid determination in serum and aqueous humour by high‐performance liquid chromatography

Abstract. High‐performance liquid chromatography on a Supelcosil LC‐HN2 analytical column in weak anion exchange mode has allowed separation of ascorbic acid, in less than 5 min, from other interfering substances in serum and aqueous humour. UV monitoring at 254 nm enables ascorbic acid to be detected at 20 pmol level. A method for determination of ascorbic acid concentration in serum and aqueous humour is described, and values from 10 cataract patients are reported.

Diurnal Intraocular Pressure After Successful Primary Laser Trabeculoplasty

In 20 patients who were successfully treated with laser trabeculoplasty as the primary therapy for glaucoma, we measured the intraocular pressure every two hours between 8:00 A.M. and 8:00 P.M. Success was defined as intraocular pressure of 22 mm Hg or less without medication. Of 20 patients, three had open-angle glaucoma and 17 had exfoliative glaucoma. Intraocular pressure was stable with small fluctuations during the daytime.

The immediate pressure response to primary laser trabeculoplasty ‐ a comparison of one‐and two‐stage treatment

Abstract The immediate pressure response to primary LTP was studied prospectively in 40 eyes randomised to one‐ and two‐stage treatment in 360° of the trabecular meshwork. There were 26 eyes with glaucoma capsulare and 14 with glaucoma simplex. Mean prelaser IOP was 32.8 mmHg in the former, and 35.5 mmHg in the latter group. The frequency and magnitude of postlaser pressure increase were the same in both groups when taking into consideration the pressure spikes in both 180° sessions. The pressure increase was higher than in earlier reports on LTP in presurgical glaucoma patients on maximum medication. Almost all IOP elevations appeared during the first 2 h following laser treatment. The results were the same in both groups 6 months after LTP.

Using probit regression to disclose the analytical performance of qualitative and semi-quantitative tests

Abstract Background: The analytical performance of qualitative and semi-quantitative tests is usually studied by calculating the fraction of positive results after replicate testing of a few specimens with known concentrations of the analyte. We propose using probit regression to model the probability of positive results as a function of the analyte concentration, based on testing many specimens once with a qualitative and a quantitative test. Methods: We collected laboratory data where urine specimens had been analyzed by both a urine albumin (‘protein’) dipstick test (Combur-Test strips) and a quantitative test (BN ProSpec System). For each dipstick cut-off level probit regression was used to estimate the probability of positive results as a function of urine albumin concentration. We also used probit regression to estimate the standard deviation of the continuous measurement signal that lies behind the binary test response. Finally, we used probit regression to estimate the probability of reading a specific semi-quantitative dipstick result as a function of urine albumin concentration. Results: Based on analyses of 3259 specimens, the concentration of urine albumin with a 0.5 (50%) probability of positive result was 57 mg/L at the lowest possible cut-off limit, and 246 and 750 mg/L at the next (higher) levels. The corresponding standard deviations were 29, 83, and 217 mg/L, respectively. Semi-quantitatively, the maximum probability of these three readings occurred at a u-albumin of 117, 420, and 1200 mg/L, respectively. Conclusions: Probit regression is a useful tool to study the analytical performance of qualitative and semi-quantitative tests.

Pressure increase following primary laser trabeculoplasty. Effect on the visual field.

Abstract. Possible damaging effects on the visual field of postlaser pressure elevations the first 24 h following primary laser trabeculoplasty were investigated in 61 patients with exfoliative or open‐angle glaucoma. The intraocular pressure was monitored the first 24 h after treatment. Treatment with pressure reducing agents was started if the intraocular pressure was ≥ 50 mmHg. The visual field was plotted before and 1, 3, and 6 months after laser treatment with the C‐30–2 program on a Humphrey visual field analyzer. Peak pressures ≥ 50 mmHg occurred with 15 (25%) patients. There was no relationship between visual field changes at 1 month and pressure increase, peak pressure, prelaser pressure, prelaser visual field indices, the use of timolol postlaser, or the pressure decrease or pressure level 1 month after laser treatment. From 1 to 6 months after laser trabeculoplasty the visual field parameters remained stable. Postlaser pressure spikes do not seem to damage the visual field providing they are detected and treated.