Gilles Turcotte

Stability of norepinephrine infusions prepared in dextrose and normal saline solutions

Purpose: Norepinephrine (NE) infusions are commonly used in the intensive care unit and in the operating room. Data on long term stability of NE solutions are lacking. This prospective study was designed to evaluate the stability of NE, in dextrose (5%) in water (D5W) and in normal saline (NS) solutions, for a period up to seven days.Methods: We prepared norepinephrine solutions in quadruplicate, by aseptically diluting 1 mg NE in 250 mL of D5W or NS and 4 mg NE in 250 mL of D5W or NS (final concentrations, 4µg·mL−1 and 16µg·mL−1, respectively) and stored the solutions at room temperature under ambient light. We sampled the solutions, in duplicate, at times 0, 24, 48, 72, 120, and 168 hr and stored them at −80°C for later assay. Norepinephrine concentrations were measured by high-performance liquid chromatography with electrochemical detection (coefficient of variation 4.6%). Statistical analysis was done by nonparametric, repeated measures ANOVA (Friedman test).Results: There was no significant decrease in NE concentration for either, NE 4µg·mL−1 in D5W or NS (P=0.09 and 0.11, respectively) or for NE 16µg·mL−1 in D5W or NS (P=0.18 and 0.40, respectively). The ratios of NE concentration at 168 hr, compared to baseline, were 95.7% and 96.4%, for NE 4µg·mL−1 in D5W and NS, respectively, and 104.5% and 96.4%, for NE 16µg·mL−1 in D5W and NS, respectively.Conclusion: Norepinephrine solutions, in concentrations commonly used in the clinical setting, are chemically stable for seven days, at room temperature and under ambient light, when diluted either in D5W or NS.RésuméObjectif: Les perfusions de norépinéphrine (NE) sont fréquemment utilisées aux soins intensifs et en salle d’opération. Toutefois, les données concernant la stabilité à long terme des solutions de NE font défaut. Cette étude prospective a été conçue dans le but d’évaluer la stabilité de la NE préparée dans des solutions de dextrose (5 %) dans l’eau (D5W) et de chlorure de sodium 0,9 % (NS), pendant une durée maximale de sept jours.Méthode: Nous avons préparé des solutions de norépinéphrine en quatre exemplaires en diluant en milieu stérile 1 mg de NE dans 250 mL de D5W ou de NS et 4 mg de NE dans 250 mL de D5W ou de NS (concentrations finales de NE de 4 µg·mL−1 et de 16 µg·mL−1, respectivement). Nous avons stocké ces solutions à température et lumière ambiantes. Nous avons échantillonné les solutions en deux exemplaires à 0, 24, 48, 72, 120 et 168 h et les avons stockées à une température de −80°C pour fin d’analyses ultérieures. Les concentrations de norépinéphrine ont été mesurées par chromatographie liquide à haute performance avec une détection électrochimique (coefficient de variation 4,6 %). L’analyse statistique a été effectuée en utilisant une ANOVA (test de Friedman) pour mesures non paramétriques répétées.Résultats: Il n’y a eu de réduction significative dans la concentration de NE dans aucune des solutions, que ce soit NE 4 µg·mL−1 dans une solution de D5W ou de NS (P=0,09 et 0,11, respectivement) ou pour la solution de NE à 16 µg·mL−1 dans du D5W ou du NS (P=0,18 et 0,40, respectivement). Les ratios de concentration de norépinéphrine à 168 h, comparées aux données initiales, étaient de 95,7 % et 96,4 % pour la NE 4 µg·mL−1 dans les solutions de D5W et de NS, respectivement, et de 104,5 % et 96,4 % pour la NE 16 µg·mL−1 dans les solutions de D5W et de NS, respectivement.Conclusion: Les solutions de norépinéphrine, aux concentrations fréquemment utilisées dans un contexte clinique, sont chimiquement stables pour sept jours si elles sont conservées à température et lumière ambiantes, qu’elles soient diluées dans des solutions de D5W ou de NS.

A new rapid immunoinhibition pancreatic amylase assay: Diagnostic value for pancreatitis

A new rapid immunoinhibition pancreatic amylase assay was compared to total amylase and lipase in an unbiased sample of 1005 emergency department patients with suspicion of pancreatitis, of which 55 had a final diagnosis of pancreatitis. Imprecision of the assays for both amylases (less than 2.5%) were better than for lipase (less than 6.1%). Correlation (R2) of pancreatic amylase with total amylase was 0.991 but only 0.789 with lipase. Using Receiver Operator Characteristics analysis, the best diagnostic cutoff point for all three enzymes was near the upper limit of the reference interval. With pancreatic amylase, sensitivity, specificity, and predictive values for positive and negative results are, respectively, 85.5, 92.5, 39.8, and 99.1%; we found similar values for lipase but poorer values (78.2, 92.0, 36.1, and 98.7%) for total amylase. Tests combination did not improve the diagnostic performance significantly. In the diagnosis of pancreatitis, pancreatic amylase (p = 0.037) and lipase (p = 0.049) had better diagnostic performance than total amylase. The correct diagnosis of pancreatitis could be achieved in 47 instead of 43 patients with either pancreatic amylase or lipase as opposed to total amylase among 1005 patients in this study. We conclude that pancreatic amylase and lipase are incrementally better diagnostic tools than total amylase for the diagnosis of pancreatitis.

Influence of continuous and discontinuous supplemental lighting on the daily variation in gaseous exchange in greenhouse cucumber

Abstract Stomatal conductance, transpiration, net photosynthesis and internal CO 2 concentration were measured on the fifth leaf of 36- to 43-day-old cucumber ( Cucumis sativus L.) plants. Three series of measurements followed the variations during a diurnal period in gaseous exchange of plants under three light regimes. One group of plants received supplemental lighting split into two periods (04:00–08:00 and 16:00–22:00) for a continuous 18-h photoperiod. A second group was illuminated between 19:00 and 05:00 for a discontinuous 18-h photoperiod. The last group received only natural light (control). Supplemental lighting increased the stomatal conductance and transpiration. Extending the photoperiod with supplemental lighting increased the net photosynthesis rate and extended the period of CO 2 assimilation. The internal CO 2 concentration varied inversely with the CO 2 assimilation rate. The continuity or discontinuity of the photoperiod did not affect gaseous exchange.