Synchronizing thermodilution cardiac output measurements with spontaneous breathing does not improve precision.

INTRODUCTION: Measuring cardiac output (CO) with the pulmonary artery catheter intermittent bolus thermodilution technique (PAC-IBTD) is less precise with spontaneous breathing compared to controlled ventilation. We aimed to test if precision could be improved in spontaneous breathing by synchronizing the measurement with respiration or using instructed respiration in 18 post-operative cardiac surgery patients. METHODS: We performed eight CO measurements with PAC-IBTD using cold saline in three different situations; in random order: 1) random compared to respiration, 2) timed to the start of expiration, and 3) synchronized with a slow exhalation through a PEP-flute. We calculated the standard deviation (SD), coefficient of variation (CV), and precision in the total material and in the three situations using a linear mixed effects model. RESULTS: A total of 408 CO measurements were performed in 17 included patients. There were no differences between the three study situations regarding mean or precision. The overall CO was 6.0 ± 1.4 l/min (mean ± SD), CV 6.2% and precision 12.2% for single measurements. Averaging three measurements increased the precision to 7.0%. CONCLUSION: We could not improve the precision of PAC-IBTD in spontaneously breathing patients by synchronizing the measurements with respiration.

Distribution of PFGE types of invasive Norwegian group B streptococci in relation to serotypes.

BACKGROUND & OBJECTIVES: Pulsed-field gel electrophoresis (PFGE) has been used for characterisation of group B streptococci, non-typeable by serotyping. We wanted to compare PFGE with serotyping in order to see the how well the method discriminates between epidemiological unrelated strains. METHODS: A total of 78 epidemiological unrelated invasive GBS strains were examined by PFGE using SmaI digested chromosomal DNA. Of these, 11 were nontypeable (NT) with regard to capsular polysaccharide (CPS) serotype. PFGE patterns were analyzed and classified in a dendrogram. RESULTS: 75 strains were typeable by PFGE, and a total of 62 restriction profiles were identified. At an 85 per cent similarity level, 53 different PFGE patterns were identified. Within each serotype, PFGE patterns differed considerably, the largest degree of heterogeneity observed among type IV, Ia, and II strains. Serotype Ib, III, and V strains were more homogeneous. Strains with identical macrorestriction profiles belonged to the same CPS type, but varied with regard to serosubtypes. Any strain among the ones investigated showing a greater than 88 per cent similarity to a restriction profile in the database, could correctly be ascribed to a particular CPS type. Of the 11 NT strains 10 restriction profiles were found, two of which were identical to the PFGE profile for a cluster of type V strains, and one profile were identical to the profile showed by a cluster of 5 type Ib strains. INTERPRETATION & CONCLUSION: PFGE is a useful technique for classifying strains that are non-typeable by conventional serotyping.