Bias due to incomplete follow up in a cohort study

AIM: To investigate the bias introduced by incomplete follow up in a cohort study of ocular outcome after premature birth. METHODS: A geographically defined cohort of children born before 32 weeks' gestation was prospectively recruited at birth to study the ocular outcome at 2 years. On the basis of attendance at 2 years, the children's families were allocated to one of three groups: group 1 attended for follow up, group 2 were difficult to trace, and group 3 were very reluctant for assessment. All children were examined by a single ophthalmologist, masked to these groupings. RESULTS: 558 children (98.8% of study group) were examined, of whom 505 were in group 1, 20 in group 2, and 33 in group 3. The groups which were more difficult to study (groups 2 and 3) showed a significantly higher prevalence of ocular abnormalities, including strabismus (p=0. 02) and cicatricial retinopathy of prematurity (p=0.002) compared with those attending for follow up. Further, not all of these cases could have been identified by review of the children's previous records. Ocular abnormalities would be underestimated by 16% (11.3% in group 1 compared with 13.4% in the total cohort, p=0.77). CONCLUSIONS: This study suggests that the prevalence of abnormalities would be underestimated by incomplete follow up, as those subjects who were most difficult to obtain for study had a significantly higher prevalence of abnormalities.     

Vitrectomy for macular pucker and vitreomacular traction syndrome

During the course of a so-called posterior vitreous detachment, a thin layer of the posterior vitreous cortex often remains adherent to the underlying retina. Tangential stretch of this vitreous pseudomembrane may cause vitreomacular traction syndrome, edema, and macular hole formation. The same process appears to underlie the development of true epimacular membranes (idiopathic macular pucker). Vitrectomy is generally agreed to be the most appropriate treatment for these clinical situations. We evaluated the incidence of vitreomacular adhesion and of visual improvement after vitrectomy of eyes with macular pucker (group 1; n=60) and vitreomacular traction syndrome (group 2; n=50). Vitreomacular attachment was assessed during vitrectomy under the condition of continuous air infusion. In the two groups, complete or partial vitreous attachment to the macula was observed in 57.4% and 74%, respectively. We conclude that vitreomacular adhesion is a common feature of the two clinical situations. Visual improvement was achieved in 73% of both groups. High rates of postoperative visual acuities of 20/50 or better (60.6% in group-1; 65.7% in group-2 cases) occurred only in eyes with preoperative values of 20/100 or better. It is reported that the visual outcome of vitreoretinal surgery for the two clinical conditions deteriorates with increasing duration after initial manifestation. Vitrectomy should not be postponed in patients who complain of disturbing visual symptoms such as reduced visual acuity, metamorphopsia and disturbance of binocular reading. This revised version was published online in July 2006 with corrections to the Cover Date.     

Intensity dependence of auditory evoked potentials (AEPs) as biological marker for cerebral serotonin levels: effects of tryptophan depletion in healthy subjects

Rationale: The intensity dependence of the auditory evoked potentials (AEP) has been suggested to be a specific biological marker of central serotonergic activity. Objective: While previous studies used circumstantial evidence to support this hypothesis, we manipulated (decreased) cerebral levels of serotonin directly by using tryptophan depletion. Methods: Twelve healthy young subjects were investigated using placebo and two different amino acid mixtures in a double blind cross over design on three different occasions. AEPs recorded during tryptophan depletion were analyzed by dipole analysis and regional sources using methods published in the literature. Results: For none of the mixtures a significant effect of tryptophan depletion was found. There was a trend towards reduced intensity dependency after tryptophan depletion, especially in the right hemisphere. This reduction correlated with the amount of reduced tryptophan in plasma. Conclusions: The results indicate, in contrast to earlier indirect studies, that the intensity dependence of AEPs is not a specific marker of central serotonergic activity. Received: 8 March 1999 / Final version: 25 May 1999     

Human plasma kallikrein and tissue kallikrein binding to a substrate based on the reactive site of a factor Xa inhibitor isolated from Bauhinia ungulata seeds

Kunitz type Bauhinia ungulata factor Xa inhibitor (BuXI) was purified from B. ungulata seeds. BuXI inactivates factor Xa and human plasma kallikrein (HuPK) with Ki values of 18.4 and 6.9 nM, respectively. However, Bauhinia variegata trypsin inhibitor (BvTI) which is 70% homologous to BuXI does not inhibit factor Xa and is less efficient on HuPK (Ki = 80 nM). The comparison between BuXI and BvTI reactive site structure indicates differences at Met59, Thr66 and Met67 residues. The hydrolysis rate of quenched fluorescence peptide substrates based on BuXI reactive site sequence, Abz-VMIAALPRTMFIQ-EDDnp (leading peptide), by HuPK and porcine pancreatic kallikrein (PoPK) is low, but hydrolysis is enhanced with Abz-VMIAALPRTMQ-EDDnp, derived from the leading peptide shortened by removing the dipeptide Phe-Ileu from the C-terminal portion, for HuPK (Km = 0.68 microM, k(cat)/Km = 1.3 x 10(6) M(-1) s(-1)), and the shorter substrate Abz-LPRTMQ-EDDnp is better for PoPK (Km = 0.66 microM, k(cat)/Km = 2.2 x 10(3) M(-1) s(-1)). The contribution of substrate methionine residues to HuPK and PoPK hydrolysis differs from that observed with factor Xa. The determined Km and k(cat) values suggest that the substrates interact with kallikreins the same as an enzyme and inhibitor interacts to form complexes.     

Exceptional performance in heart preservation with an amino acid—Containing perfusion fluid

This is a report of a study aimed at putting into practice a new theory for hypothermic preservation of viable organs. A perfusion fluid elaborated according to this theory was applied in preservation of the heart, and resulted in storage of the heart for up to 72 hours with preservation of its functions (rhythm, presystolic ventricular pressure, systolic ventricular pressure, cardiac work, coronary blood pressure, sensitivity to drugs) and its morphology. An important finding was that repeated heart storage for 24 hours alternating with functional testing for 5–7 hours could be performed without irreversible alterations of cardiac function and fine structure. Furthermore, during functional testing following storage the hearts consistently demonstrated improvement of function in time, suggesting that the preserved myocardial tissues were able to rapidly achieve metabolic reequilibration. The results of this study provide the possibility of developing a system for efficient ex vivo heart conditioning before transplantation.

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Résumé Nous avons testé la valeur d'une nouvelle théorie sur la préservation d'organes en hypothermie. Un liquide de perfusion conforme à cette théorie a été utilisé pour la préservation cardiaque. Il permet de conserver le coeur pendant 72 heures, sans altérations de ses fonctions (rythme, pression ventriculaire pré-systolique et systolique, travail cardiaque, pression coronaire, sensibilité aux médicaments) ni de sa morphologie. De plus, le coeur peut-être, à plusieurs reprises, conservé pendant 24 heures, avec des intervalles de reprise fonctionnelle de 5–7 heures, sans que sa fonction ni sa structure fine ne soient altérées de façon irréversible. Enfin, l'étude fonctionnelle montre qu'après conservation la fonction cardiaque s'améliore avec le temps, suggérant donc une rééquilibration métabolique rapide du tissu myocardique. Les résultats de cette étude permettront la mise au point d'un système efficace de conservation cardiaque ex-vivo en vue de la transplantation.

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Supported by the German Heart Center, Munich, and the German Academy Department for Foreign Scientific Relationships, Bonn.     

Antimicrobial sensitivities in urinary tract infections in men

Six-thousand-seven-hunderd and forty-nine positive urine cultures from a large metropolitan Veterans Administration hospital were analyzed with respect to the organisms isolated and their antimicrobial sensitivies. A predicted therapeutic efficacy index was calculated for each antimicrobial agent tested. Gram-negative pathogens accounted for 84% of the infections. Proteus infections outnumbered those due to strains ofEscherichia coli. Gentamycin was found to be the most effective antimicrobial agent.     

Heparin--examination of its antibacterial adsorption properties

One of the primary antibacterial defense mechanisms of the bladder is the action of the luminal mucopolysaccharide layer against adsorption of inoculated bacteria. Previous studies have shown that local instillation of the mucopolysaccharide heparin can prevent bacterial adsorption on the bladder mucosa denuded of this "antiadherence factor." To determine whether this action was due to the mucopolysaccharide composition of heparin, or rather to its anticoagulant property, protamine sulfate (a basic protein with anticoagulant properties) was tested for antiadsorptive efficacy. Protamine offered no protection against bacterial adherence in the rabbit model. It appears that heparin's protective effect is unrelated to its action as an anticoagulant.     

Management of complications after operations for acute pancreatitis

After early operation in 49 patients and delayed operation in 114 patients, all with acute hemorrhagic-necrotizing pancreatitis, 65% of patients developed local or general complications. Local complications were abscesses, peritonitis, bleeding, gastrointestinal fistulae or stenoses, and external pancreatic fistulae. Their cause can be traced to the large wound cavity with the tryptic wound surface as well as residual necrosis. The general postoperative complications were shock, acute renal failure, cardiorespiratory insufficiency, gastrointestinal bleeding, ileus, coagulopathy, and sepsis. These may have resulted from the local complications, or may even have been present before operation. If local septic complications do not respond to conservative treatment, they require reoperation. For gastrointestinal fistulae or stenoses, or for pancreatic fistulae, a wait and see attitude is recommended. Generalized complications call for aggressive intensive medical care.Despite the frequency of postoperative complications, the total mortality rate in our series was 30% in patients with partial pancreatic necrosis operated on early, and in patients who received delayed operations for acute hemorrhagic-necrotizing pancreatitis. The 74% mortality rate in early operations of subtotal and total pancreatic necroses was admittedly high. Operative results in those patients who were under our care from the beginning, however, were more encouraging (mortality rate of 50%) and demonstrate that the correct treatment for severe acute hemorrhagic-necrotizing pancreatitis is surgery.

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Résumé Cent soixante trois malades atteints de pancréatite aigüe nécrotico-hémorragique ont subi une opération précoce (49 cas) ou retardée (114 cas): 65% d'entre eux ont développé des complications locales ou générales. Les complications locales ont été des abcès, des péritonites, des hémorragies, des fistules ou sténoses digestives, des fistules pancréatiques externes. La cause en est la large cavité résiduelle postopératoire avec ses surfaces pancréatiques cruentées et ses nécroses résiduelles. Les complications générales ont été des états de choc, des insuffisances rénales aigües, des défaillances cardio-respiratoires, des hémorragies digestives, des iléus, des troubles de la coagulation et des infections. Elles peuvent être la conséquence des complications locales ou peuvent être apparues avant l'opération. Lorsque les complications infectieuses locales ne répondent pas au traitement conservateur, elles doivent être opérées. Pour les fistules et sténoses digestives, pour les fistules pancréatiques, nous recommandons l'expectative. Les complications générales exigent un traitement médical aggressif.Malgré la fréquence des complications postopératoires, la mortalité globale, dans notre série de patients, a été de 30% pour les pancréatites nécrosantes opérées précocement et pour les pancréatites nécrotico-hémorragiques ayant subi une opération retardée. La mortalité de 74% pour les opérations précoces dans les nécroses pancréatiques subtotales ou totales est trop lourde. Mais les résultats obtenus chez les patients qui ont été traités dans notre service dès le début de la maladie ont été plus encourageants (mortalité 50%): ils montrent que la chirurgie est le traitement adéquat de la pancréatite aigüe nécrotico-hémorragique grave.

     

Nd-YAG laser ablation of arteriosclerotic obstructions: Clinical long-term results in femoropopliteal artery occlusions

Laser recanalization of peripheral artery occlusions was performed in 338 patients. A continuous wave Nd-YAG laser was used in combination with sapphire-probe laser catheters. The initial recanalization rate was 85%. Complications such as dissections, perforations, emboli and spasm were observed in 14%. The cumulative patency rate after 3 years was 48%.