Barostat or dynamic balloon distention test: which technique is best suited for esophageal sensory testing?

Esophageal sensation is commonly assessed by barostat-assisted balloon distension (BBD) or dynamic balloon distension (DBD) technique, but their relative merits are unknown. Our aim was to compare the usefulness and tolerability of both techniques. Sixteen healthy volunteers (male/female = 6/10) randomly underwent graded esophageal balloon distensions, using either BBD (n= 8) or DBD (n= 8). BBD was performed by placing a 5-cm long highly compliant balloon attached to a barostat, and DBD by placing a 5-cm long balloon attached to a leveling container. Intermittent phasic balloon distensions were performed in increments of 6 mm Hg. Sensory thresholds and biomechanical properties were assessed and compared. Sensory thresholds for first perception (mean ± standard deviation; 21 ± 6 vs. 21.2 ± 5, mm Hg, P= 0.9), discomfort (38 ± 8 vs. 35 ± 9, P= 0.5), and pain (44 ± 4 vs. 45 ± 3, P= 0.7) were similar with BBD and DBD techniques. However, more subjects tolerated DBD (7/8, 88%) when compared with BBD (4/8, 50%). Forceful expulsion of balloon into stomach (n= 4), pulling around the mouth (n= 4), chest discomfort (n= 2) and retching (n= 2) were overlapping reasons for intolerance with BBD. Esophageal wall distensibility was similar with both techniques. Both techniques provided comparable data on biomechanical properties. However, DBD was better tolerated than BBD for evaluation of esophageal sensation. Hence, we recommend DBD for performing esophageal balloon distension test.

Adenosine modulates oesophageal sensorimotor function in humans.

BACKGROUND AND AIMS: Adenosine mediates somatic and visceral pain, but its effects on gut visceral nociception are unknown. The aim of the present study was to test the hypothesis that adenosine alters oesophageal sensorimotor function. METHODS: In a double-blind, randomised, placebo-controlled study, 14 healthy volunteers (M/F = 4/10) received either intravenous adenosine 100 microg/kg/min or placebo infusion. Prior to and during infusion, all subjects underwent stepwise graded oesophageal balloon distensions using impedance planimetry. Sensory responses and biomechanical properties were assessed and compared. RESULTS: Adenosine significantly lowered thresholds for first perception (median (25th-75th), cm H(2)O; 10 (10-20) vs 30 (20-30), p = 0.007), discomfort (40 (30-40) vs 50 (50-60), p = 0.011) and pain (50 (40-60) vs 70 (60-70), p = 0.007) when compared with placebo. Also, the median threshold pressures required to induce first perception (p = 0.017), discomfort (p = 0.024) and pain (p = 0.026) were lower when compared with baseline. The cross-sectional area of the oesophagus increased (p = 0.032), and the circumferential wall tension/strain relationship shifted to the left (the wall became stiffer) (p = 0.043) after adenosine, when compared with baseline or placebo. CONCLUSIONS: Adenosine can induce visceral hyperalgesia and decrease oesophageal distensibility in humans. These evoked sensorimotor changes are similar to those described in patients with functional oesophageal (non-cardiac) chest pain. Thus, adenosine modulates oesophageal sensorimotor function and may play a role in the pathogenesis of functional chest pain.

Pancreatic stent prophylaxis of post endoscopic retrograde cholangiopancreatography pancreatitis: spontaneous migration rates and clinical outcomes.

AIM: Pancreatic duct (PD) stents diminish the risk of post endoscopic retrograde cholangiopancreatography (ERCP) pancreatitis (PEP) in high-risk patients; 3 Fr stents are reported to spontaneously migrate at a significantly higher rate than 5 Fr stents in a cohort of mostly sphincter of Oddi (SOD) patients. We sought to assess spontaneous migration rates of 5 Fr and 7 Fr stents and effectiveness in preventing PEP in a diverse group of high risk patients. METHODS: A total of 4,332 ERCP exams performed between January 2002 and August 2005 were reviewed to identify patients undergoing PD stent placement. Follow-up was obtained from electronic medical records and contact with referring MDs. Plain abdominal radiographs were used to document stent passage. RESULTS: PD stents for PEP prophylaxis were placed in 246 exams (232 patients) undergoing: PD (major or minor) sphincterotomy (84), ampullectomy (50), SOD (46), bile duct precut (35), papillary stenosis balloon dilation (9) and difficult cannulation (8). Stents placed: 218 5-Fr (140 were 3 cm long and 78 =or> 5 cm long) and 28 7-Fr (12 were 3 cm long, 16=or> 5cm long). Follow-up was available in 197 (171 5-Fr, 26 7-Fr) of 246 placements (80%). Twenty of 171 5-Fr stents were electively removed via EGD within=or< 24 h per endoscopist preference and were not included in analysis; 128 of the remaining 151 5-Fr stents (85%) spontaneously migrated by (or within) median of 8 days and 23 failed to pass and required EGD removal. Of 26 7-Fr stents one was electively removed =or< 24 h later; of the remaining 25, 15 (60%) spontaneously migrated by median of 16 days, 10 required EGD removal. The spontaneous migration rate of 5 Fr stents was: 1) significantly higher than 7 Fr stents; 2) significantly higher than the previously reported 67% passage rate of 5 Fr stents; and 3) similar to the previously reported 86% passage rate of 3 Fr stents. PEP occurred in 15% (n=36: 24 mild, 11 moderate, 1 severe). CONCLUSION: The spontaneous dislodgement rate of 5 Fr stents in patients where the indication is primarily non-SOD is approximately 85% - significantly higher than previously reported and similar to the reported rate of spontaneous dislodgement of 3 Fr stents in SOD patients; 5 Fr stents migrate spontaneously earlier and more frequently than 7 Fr stents.

Endoscopic transmural entry into pancreatic fluid collections using a dedicated aspiration needle without endoscopic ultrasound guidance: success and complication rates.

BACKGROUND: Endoscopic drainage of pancreatic fluid collections (PFC) is performed with increasing frequency. A variety of techniques for performing transmural entry have been described. However, data are lacking on the technical success and safety of transmural entry using a single technique. The authors describe the largest experience in transmural entry of PFCs without endoscopic ultrasound (EUS) guidance using a dedicated aspiration needle. METHODS: All patients who underwent endoscopic transmural drainage of PFC from October 1998 to May 2006 were identified from the endoscopy database. Data were abstracted from the endoscopic procedure report and the patient records then placed in a JMP drive. All drainages were performed without EUS guidance after visualization of an obvious intraluminal bulge using a dedicated large-bore aspiration needle. The transmural tract into the PFC was dilated using a balloon with a diameter of 6 to 20 mm followed by subsequent placement of one or two 10-Fr double pigtail stents with or without nasocystic irrigation tubes. Successful entry was defined as entry allowing for the placement of stents. RESULTS: No significant difference in the complication rates was observed when they were analyzed for the following variables: age, gender, balloon diameter, presence of endoscopic impression, drainage approach, and size and type of fluid collection. CONCLUSION: Endoscopic transmural drainage of pancreatic fluid collections can be performed safely and effectively via the Seldinger technique without endoscopic ultrasound guidance. The study data will allow sample size calculations to be made if direct comparisons with this technique and others are undertaken.

Endoscopic retrograde cholangiopancreatography in post-Whipple patients.

BACKGROUND AND STUDY AIMS: Endoscopic retrograde cholangiopancreatography (ERCP) is an established modality for evaluation and treatment of pancreaticobiliary disorders. However, it is technically more challenging in patients with post-surgical anatomy. The success rate of ERCP in patients with prior pancreaticoduodenectomy (Whipple resection) is unknown. We assessed the technical success and safety of ERCP in this patient population. PATIENTS AND METHODS: Post pancreaticoduodenectomy patients who had undergone ERCP between January 2002 and May 2005 were identified through a computerized medical index system. ERCP was considered successful if the duct of clinical interest had been cannulated and endoscopic therapy had been performed when indicated. RESULTS: ERCP was attempted 88 times in 51 patients with prior pancreaticoduodenectomy, including 37 procedures for pancreatic indications, 44 for biliary obstruction, and 7 for both biliary and pancreatic indications. The overall technical success rate of ERCP based on the intention behind the procedure was 51 % (45 of the 88 procedures). Success was significantly more likely for biliary indications (37/44, 84 %) than for pancreatic indications (3/37, 8 %) ( P < or = .001). Complications occurred in 2 % of the procedures and included one self- contained perforation treated medically and one Mallory-Weiss tear. CONCLUSIONS: When performed by experienced endoscopists, ERCP in patients with prior pancreaticoduodenectomy is safe, with a high success rate for biliary indications and a low success rate for pancreatic duct indications. Better methods of achieving pancreatic duct cannulation after pancreaticoduodenectomy are needed.

Role of spinal NMDA and non-NMDA receptors in the pressor reflex response to abdominal ischemia.

Abdominal ischemia induces a pressor reflex caused mainly by C-fiber afferent stimulation. Because excitatory amino acids, such as glutamate, bind to N-methyl-D-aspartate (NMDA) and non-NMDA [dl-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)] receptors and serve as important spinal neurotransmitters, we hypothesized that both receptors play a role in the abdominal ischemia pressor reflex. In chloralose-anesthetized cats, NMDA receptor blockade with 25.0 mM dl-2-amino-5-phosphonopentanoate did not alter the pressor reflex (33 +/- 9 to 33 +/- 7 mmHg, P > 0.05, n = 4), whereas AMPA receptor blockade with 4.0 mM 6-nitro-7-sulfamylbenzo(f)quinoxaline-2,3-dione significantly attenuated the reflex (29 +/- 5 to 16 +/- 4 mmHg, P < 0.05, n = 6). Because several studies suggest that anesthesia masks the effects of glutamatergic receptors, this experiment was repeated on decerebrate cats, and in this group, NMDA receptor blockade with 25.0 mM dl-2-amino-5-phosphonopentanoate significantly altered the pressor reflex (36 +/- 3 to 25 +/- 4 mmHg, P < 0.05, n = 5). Our combined data suggest that spinal NMDA and AMPA receptors play a role in the abdominal ischemia pressor reflex.

Validation of a high-performance liquid chromatographic assay for the quantification of adenovirus type 5 particles.

An anion-exchange-high-performance liquid chromatography (AE-HPLC) method for the quantification of adenovirus type 5 (Ad5) total particles was validated according to performance criteria of precision, specificity, linearity of calibration and range, limit of detection, limit of quantification, accuracy and recovery. The viral particles were detected by absorbance at 260 nm using photodiode array detector (PDA). Cesium chloride (CsCl) purified Ad5 and lysate samples were used for the validation of the method. Relative standard deviations (RSDs) for the inter-day, intra-day precision and reproducibility for both the lysate and the Ad5 standard were less than 10 and 2% for the peak area and retention time, respectively. The method was specific for Ad5 which was eluted at 8.0 min. The presence of DNA does not affect the recovery of Ad5 particles for accurate quantification. Based on the error in prediction to be less than 10%, the working range was established between 2 x 10(10) and 7 x 10(10) VP/ml with correlation coefficient of 0.99975, standard deviation of 6.14 x 10(9) VP/ml and a slope of 3.04 x 10(5) VP/ml. The recovery of the method varied between 88 and 106% in all of the lysate samples investigated which is statistically similar to 100% recovery at 95% confidence interval.

Reflex cardiovascular response to brief abdominal visceral ischemia is mediated in part by prostaglandins.

Prostaglandin concentrations are elevated in intestinal lymph during brief abdominal visceral ischemia, and exogenously applied prostaglandins can directly stimulate or sensitize ischemically sensitive visceral sympathetic nerve fibers. However, it is not known if prostaglandin production during abdominal ischemia is sufficient to contribute to the reflex cardiovascular response (e.g., hypertension). Accordingly, in anesthetized cats, the femoral artery was cannulated for measurement of arterial blood pressure, and the superior mesenteric and celiac arteries were isolated and fitted with snare occluders. After dual occlusion of these arteries ( 0.05). In group 2, acetylsalicylic acid significantly (P < 0.05) reduced the reflex rise in blood pressure by 46% (28 +/- 3 to 15 +/- 4 mmHg). A second, more invasive preparation (group 3) was utilized to 1) minimize the confounding, transient, nonreflex rise in blood pressure associated with arterial ligation, and 2) further assess the inhibitory effect of indomethacin. In group 3, the ischemia-induced blood pressure rise of 28 +/- 6 mmHg was reduced by 43% to 16 +/- 4 mmHg after indomethacin (n = 4, P < 0.05). Thus blockade of the cyclooxygenase pathway by two structurally dissimilar inhibitors attenuated the visceral-cardiovascular reflex response to brief ischemia, suggesting that prostaglandins released during visceral ischemia contribute significantly to the activation of the reflex cardiovascular response.

Bradykinin BK2 receptors contribute to reflex cardiovascular responses during brief abdominal ischemia.

Ischemically sensitive visceral sympathetic nerve fibers, which are thought to represent the afferent limb of a strong cardiovascular pressor reflex, can be stimulated by exogenously applied bradykinin (BK). During ischemia, BK also is known to be produced locally and to serve as an endogenous stimulus for activation of ischemically sensitive nerve endings. It is unclear, however, whether ischemically induced BK production is sufficient to elicit a reflex cardiovascular response. Accordingly, femoral arterial and venous catheters were positioned in anesthetized cats, and the superior mesenteric and celiac arteries were isolated for placement of snare occluders. After dual occlusion of these arteries (20 min), one of two chemically dissimilar specific kinin B2 (BK2) receptor antagonists, HOE-140 (30-40 micrograms/kg iv, n = 8) or NPC-17731 (30-40 micrograms/kg iv, n = 11), was administered and dual occlusion was repeated. The reflex rise of mean arterial blood pressure (BP) of 16 +/- 3.7% was significantly (P < 0.05) reduced by HOE-140 to 8.4 +/- 2.0%. NPC-17731 similarly attenuated the reflex BP increment from 13 +/- 1.2 to 6.2 +/- 1.6% (P < 0.05). In a separate set of control animals the first and second periods of ischemia induced reflex BP increments that did not differ significantly (16 +/- 2.7 and 16 +/- 5.7%, respectively). Qualitatively similar decrements of the BP response were produced by the BK2 receptor antagonists in two additional groups in which blood flow to the superior mesenteric and celiac arteries was diverted to a venous reservoir to eliminate the initial transient (mechanically induced) rise in BP associated with artery ligation that is known not to be associated with the reflex response. These results indicate that the stimulation of BK2 receptors on visceral afferent nerves by BK is responsible, at least in part, for the reflex cardiovascular response during visceral ischemia.

Cardiovascular reflex responses to ischemia during occlusion of celiac and/or superior mesenteric arteries.

Global abdominal visceral ischemia leads to profound cardiovascular reflex adjustments. However, the separate contributions of the celiac artery and superior mesenteric artery (SMA) vascular beds to this reflex are unknown. Accordingly, we compared the effects of single and combined occlusions of these vessels on blood pressure (BP) in anesthetized cats. Tissue mass and pH of selected organs, regional blood gases, pH, and lactate also were measured as potential contributing factors. Occlusion of the SMA or celiac artery produced significantly (P < 0.05) different increments in BP (30 +/- 4 vs. 18 +/- 4 mmHg, respectively). Combined occlusion of the two vessels augmented BP by 53 +/- 12 mmHg, a significantly greater increase than during celiac ligation. Venous lactate levels increased significantly during SMA, but not celiac, occlusion, and the decline in venous pH was significantly greater in the SMA than in the celiac vascular bed (-0.20 +/- 0.03 vs. -0.08 +/- 0.02 pH units, P < 0.05, respectively). The decline in tissue pH of SMA-perfused organs during SMA occlusion was significantly greater than in celiac-perfused organs during celiac occlusion. Conversely, tissue mass subserved by the celiac artery was significantly greater than that subserved by the SMA (182 +/- 27 vs. 131 +/- 17 g, respectively). These data suggest that the larger cardiovascular reflex produced by SMA occlusion compared with celiac occlusion may be related to a greater increase of lactic acid concentration in tissue supplied by the SMA. In addition, the large reflex increase in BP produced by combined occlusion of these vessels is an additive effect, presumably related to larger organ mass and recruitment of more sensory nerve fibers.

The effect of acute hyperglycemia on flow velocity in the macular capillaries.

The effect of acute hyperglycemia on retinal blood flow was measured in 12 diabetic patients (mean blood glucose, 276 mg%) on continuous subcutaneous insulin infusion and six nondiabetic controls (mean blood glucose, 198 mg%). Flow velocity measurements in macular capillaries were made using the blue field entoptic method. Retinal artery and vein diameters were measured using red-free fundus photographs. No significant change in flow velocity or retinal vessel diameter was noted in either group.

Role of fluorescein glucuronide and its metabolism in vitreous fluorophotometry.

Rabbits were given fluorescein or fluorescein glucuronide intravenously. Fluorescein and fluorescein glucuronide concentrations in plasma and vitreous samples were measured by high-performance liquid chromatography. Vitreous fluorophotometry was performed using the Fluorotron Master to compare scans after administration of fluorescein and fluorescein glucuronide, and for comparison of in vivo fluorescence with in vitro high-performance liquid chromatography analysis. Fluorescein glucuronide was shown to enter the vitreous as early as 1 hr after injection. Fluorescein glucuronide was the dominant molecule in both vitreous and plasma of all rabbits at 6 hr. Because fluorescein glucuronide has a lower fluorescence than fluorescein, the fluorophotometer overestimates the vitreous concentration of fluorescein after its administration. Since fluorescein is metabolized rapidly to fluorescein glucuronide in man, entry of fluorescein glucuronide into the eye should be considered in measurements of blood-ocular barrier permeability by vitreous fluorophotometry.

Measurement of blood-retinal barrier function in central retinal vein occlusion.

Vitreous fluorophotometry was used to measure blood-retinal barrier permeability to fluorescein in eight patients (mean age, 42.9 years; range, 30 to 55 years) with central retinal vein occlusion (CRVO). Permeability coefficient was derived by fitting a mathematical model to the posterior vitreous fluorescence scan and plasma-free fluorescein concentration curve at 60 minutes after intravenous fluorescein sodium (14 mg X kg-1). A permeability index (PI) was estimated by dividing the area under the vitreous fluorescence scan by the area under the plasma-free fluorescein curve. The permeability coefficient and PI were comparable and highly correlated. Initial mean permeability coefficient was 28.78 X 10(-7) cm X s-1 (range, 14.42 X 10(-7) to 41.10 X 10(-7) and 1.89 X 10(-7) cm X s-2 (range, 0.96 X 10(-7) to 2.76 X 10(-7) in eight affected and seven unaffected eyes, respectively. The permeability coefficient and PI in unaffected eyes did not differ significantly from 18 eyes of ten normal subjects. After three to 12 months, permeability coefficient and PI in affected eyes approached the values in the contralateral eyes of four patients with mild and one patient with moderate CRVO but remained elevated in the remaining patients. The permeability coefficient and PI correlated well with changes in severity of retinal appearances on color photographs and fluorescein angiograms. Vitreous fluorophotometry quantitated changes in blood-retinal barrier permeability in CRVO.

Somatostatin inhibits the ventilatory response to hypoxia in humans.

The effects of a 90-min infusion of somatostatin (1 mg/h) on ventilation and the ventilatory responses to hypoxia and hypercapnia were studied in six normal adult males. Minute ventilation (VE) was measured with inductance plethysmography, arterial 02 saturation (SaO2) was measured with ear oximetry, and arterial PCO2 (Paco2) was estimated with a transcutaneous CO2 electrode. The steady-state ventilatory response to hypoxia (delta VE/delta SaO2) was measured in subjects breathing 10.5% O2 in an open circuit while isocapnia was maintained by the addition of CO2. The hypercapnic response (delta VE/delta PaCO2) was measured in subjects breathing first 5% and then 7.5% CO2 (in 52-55% O2). Somatostatin greatly attenuated the hypoxic response (control mean -790 ml x min-1.%SaO2 -1, somatostatin mean -120 ml x min-1.%SaO2 -1; P less than 0.01), caused a small fall in resting ventilation (mean % fall - 11%), but did not affect the hypercapnic response. In three of the subjects progressive ventilatory responses (using rebreathing techniques, dry gas meter, and end-tidal Pco2 analysis) and overall metabolism were measured. Somatostatin caused similar changes (mean fall in hypoxic response -73%; no change in hypercapnic response) and did not alter overall O2 consumption nor CO2 production. These results show an hitherto-unsuspected inhibitory potential of this neuropeptide on the control of breathing; the sparing of the hypercapnic response is suggestive of an action on the carotid body but does not exclude a central effect.

Vitreous fluorophotometry in patients with no or minimal diabetic retinopathy.

Vitreous fluorophotometry was used to estimate fluorescein leakage into the posterior vitreous of 20 insulin-dependent diabetic patients with no or minimal diabetic retinopathy 60 min after intravenous administration of 14 mg X kg-1 fluorescein. The permeability coefficient (p), a measure of fluorescein penetration through the blood-retinal barrier (BRB) into the vitreous, and the diffusion coefficient (D), a measure of fluorescein dispersion within the vitreous, were obtained by fitting a mathematical model to the vitreous fluorescence scan and plasma free fluorescence curve. A permeability index (PI) was also derived by dividing the area under the fluorescence scan by the area under the plasma free fluorescence time curve. The fluorescence concentrations at discrete distances from the retina were also noted. The mean +/- SD for p, D, and PI were 1.95 +/- 1.03 cm X s-1 X 10(-7), 1.74 +/- 1.53 cm2 X s-1 X 10(-5), and 2.14 +/- 1.21 cm X s-1 X 10(-7), respectively, and were not significantly different from values determined in normal subjects. Diabetic patients and normal subjects also had similar fluorescence measurements at corresponding distances from the retina. Quantitative indices of fluorescein leakage did not correlate with either the microaneurysm counts on fluorescein angiograms or the duration of diabetes. Vitreous fluorophotometry did not detect any abnormality of the BRB in diabetic patients with no or minimal retinopathy on fluorescein angiography.

Familial hypopituitarism associated with an enlarged pituitary fossa and an empty sella.

We report an 8-year follow-up of three sisters born of a consanguineous marriage and who originally presented with short stature and enlarged pituitary fossa. All have shown progressive failure of anterior pituitary hormone function. In addition, the two eldest sisters were eventually found to have an empty sella while the youngest, who initially showed an enhancing intrasellar mass consistent with a tumour, later showed an empty sella. A familial pituitary tumour developing early in childhood but subsequently undergoing involution could account for these findings.

Blood pressure and the progression of mild background diabetic retinopathy.

A retrospective 5-year study examined the relationship between blood pressure and the severity and progression of mild background retinopathy in 48 patients with non-insulin-dependent diabetes and 38 with insulin-dependent diabetes who did not receive treatment in either eye for at least 3 years from their initial visit. All patients had annual medical and ophthalmic examinations including fundus photography. Retinopathy was assessed from fundus photographs using the Hammersmith grading system. Initial mean systolic and diastolic blood pressures (mm Hg) were significantly higher in those with non-insulin-dependent diabetes (149/88) than in patients with insulin-dependent diabetes (129/81). The former had significantly worse retinopathy than the latter initially and at 5 years. When non-insulin-dependent patients were grouped according to systolic blood pressure, those with readings above 160 mm Hg had significantly more severe retinopathy than those with readings below 140 mm Hg. Blood pressures initially and at 3 years were not significantly different between patients who received photocoagulation (five with insulin-dependent and six with non-insulin-dependent diabetes and those who did not in either group. There was significant correlation between systolic blood pressure and severity of retinopathy in patients with non-insulin-dependent disease, but the change in severity of retinopathy at 5 years did not correlate with blood pressure in either group.

Measurement of blood-retinal barrier permeability: a reproducibility study in normal eyes.

Fluorescein penetration into the posterior vitreous depends on plasma-free fluorescein concentration and blood-retinal barrier (BRB) permeability. The reproducibility of two methods of deriving BRB permeability was studied in 19 normal eyes of 14 subjects using vitreous fluorophotometry on two separate occasions. Plasma-free fluorescence was measured at intervals over 1 hr and posterior vitreous fluorescence was measured before (background scan), within 6 min (bolus) and at 60 min (measurement) after intravenous fluorescein (14 mg X kg-1). A computer algorithm subtracted background fluorescence from the measurement scan which was then corrected for signal spread by using a "spread" function derived from the bolus scan. BRB permeability coefficient and vitreous diffusion coefficients were derived by fitting a mathematical model to the plasma and corrected vitreous fluorescence data. A permeability index was also calculated by dividing the area under the vitreous fluorescence by the area under the plasma fluorescence curve. There were no significant differences in the results between right and left eyes. Mean +/- SD values on first and second occasions for all eyes were permeability coefficient: (1.91 +/- 0.94) and (2.08 +/- 0.95) X 10(-7) cm X s-1; diffusion coefficient: (1.33 +/- 0.68) and (1.19 +/- 0.54) X 10(-5) cm2 X s-1; and permeability index: (2.05 +/- 1.03) and (2.11 +/- 1.02) X 10(-7) cm X s-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolism of fluorescein after intravenous administration.

The measurement of plasma unbound (free) fluorescein is important in the study of blood-ocular barrier kinetics. The authors became concerned about the quantitative significance of the presumed glucuronide metabolite of fluorescein to the measurement of plasma fluorescence in diabetic and normal subjects. Fluorescein was given intravenously (14 mg/kg) to seven normal subjects and eight diabetic subjects. Plasma samples taken during 60 min were subjected to microfiltration, from which aliquots of ultrafiltrate were incubated with beta-glucuronidase. Samples were subjected to high-performance liquid chromatography, and fluorescence activity was measured in the eluent. All subjects showed an additional fluorescence peak to that of fluorescein in plasma and ultrafiltrate 5 min after fluorescein administration and increased thereafter. This additional peak was abolished by incubation of ultrafiltrate with beta-glucuronidase and resulted in a marked increase in fluorescence due to the liberation of fluorescein from its presumed glucuronide. There were no pharmacokinetic differences between normal and diabetic subjects in plasma-free fluorescein and fluorescein glucuronide pharmacokinetics or in their respective binding to plasma proteins. The glucuronide had only 4.5% of the fluorescence of fluorescein, but because more of the glucuronide was unbound (32%) compared with fluorescein (10%) and its concentration increased while that of fluorescein decreased, it constituted an increasing proportion of the fluorescence in the ultrafiltrate. At 60 min, 80% of the fluorescein was present as glucuronide and contributed 20% of the total fluorescence in the ultrafiltrate. Fluorescein-glucuronide is a potential source of variability in studies on blood-ocular barrier kinetics.

Quantitative changes in blood-retinal barrier function in central retinal vein occlusion.

Posterior vitreous fluorescence was measured with a fluorophotometer 60 minutes after intravenous sodium fluorescein (14 mg/kg) in 6 patients (age range 30 to 54 years) with central retinal vein occlusion (CRVO). Plasma free fluorescein was measured at frequent intervals for 60 minutes. A permeability index (PI) was estimated by dividing the area under the vitreous fluorescence scan by the area under the plasma free fluorescein curve. Initially mean PI was 24.3 (range 12.6-31.6) and 2.1 (range 1.3-31.) cm s-1 X 10(-7) in affected and unaffected eyes respectively. After 6 to 12 months, PI in affected eyes approached the values in the unaffected eyes of 5 patients with mild CRVO but remained elevated in one patient who presented with severe (ischaemic) CRVO. In each patient qualitative changes in retinal appearances paralleled quantitative changes in PI. The effect of venous outflow obstruction on the blood-retinal barrier can be quantitated by fluorophotometry.