Predicting blood loss in surgery for idiopathic scoliosis

The authors attempted to determine the relative importance of factors that influence bleeding during and after spinal fusion. Data from 30 ASA I patients with idiopathic scoliosis were prospectively collected and analyzed. Intraoperative bleeding was 1971 ± 831 ml (mean ± SD) (61.5 ± 27% of estimated blood volume (EBV) and correlated with the number of fused vertebrae (r = 0.66, P < 0.0001) and the duration of surgery (r = 0.46, P = 0.0105). There was no correlation between intraoperative bleeding and the Cobb curve angle (43 to 86°), the mean arterial blood pressure (MAP) (63 to 86 mmHg), the central venous pressure (CVP), the quantity of epinephrine infiltrated, muscle relaxants or opioids used, nor in the type of opioids used, the minimal body temperature or whether stored or autologous blood was used. Postoperative bleeding was 1383 ± 369 ml (43.1 ± 11.7% of EBV) and correlated with the length of time the Hemovac drain was in place (r = 0.40, P = 0.0285) and MAP (r = 0.40, P = 0.0285). There was no correlation between postoperative and intraoperative bleeding nor in the number of fused vertebrae. Six patients had greater postoperative than intraoperative bleeding. The total bleeding (intra-plus postoperative) was 3347 ± 920 ml (104.2 ± 30.6 of EBV) and correlated with the number of fused vertebrae (r = 0.63, P = 0.0001) and with the duration of surgery (r = 0.42, P = 0.0208). We conclude that the number of fused vertebrae is the key factor in predicting intraoperative and total bleeding. Postoperative bleeding is considerable (up to 76.9% of EBV). No other factors allow for adequate prediction of postoperative bleeding and these patients must be kept under strict surveillance after surgery. Cette étude avait pour but de déterminer l’importance relative des facteurs qui influencent les pertes sanguines per et postopératoires au cours des arthrodèses vertébrales postérieures. Les données de 30 patients porteurs de scoliose idiopathique ont été recueillies prospectivement puis analysées. Le saignement intraopératoire était de 1971 ± 831 ml (moyenne ± DS) (61.5 ± 27% du volume sanguin estimé (VSE)) et était relié au nombre de vertèbres fusionnées (r = 0.66, P < 0.0001) et à la durée de la chirurgie (r = 0.46, P = 0.0105). Le saignement intraopératoire n’était pas relié au degré de courbure (43 à 86°), ni à la pression artérielle moyenne (PAM) (63 à 86 mmHg), à la pression veineuse centrale (PVC), à la quantité d’épinéphrine, de relaxants neuro- musculaires ou de morphiniques utilisés, ni à la sorte de morphinique utilisé, à la temperature corporelle minimale ou au type de sang administré. Le saignement post-opératoire était de 1383 ± 369 ml (43.1 ± 11.7% du VSE) et était relié à la durée du maintien d’un drain (r = 0.40, P = 0.0285) et à la PAM (r = 0.40, P = 0.0285). Le saignement post-opératoire n’était pas relié au saignement intra-opératoire ni au nombre de vertèbres fusionnées. Six patients ont eu un saignement post-opératoire supérieur au saignement intra-opératoire. Le saignement total (intra et postopératoire) était de 3347 ± 920 ml (104.2 ± 30.6% du VSE) et était relié au nombre de vertèbres fusionnées (r = 0.63, P = 0.0001) ainsi qu’à la durée de la chirurgie (r = 0.42, P = 0.0208). Nous concluons que le nombre de vertèbres fusionnées est le meilleur facteur pour prédire le saignement intraopératoire et le saignement total. Le saignement post-opératoire est élevé (jusqu’à 76.9% du VSE). Il n’y a pas d’autre facteur utile pouvant prédire le saignement post-opératoire et tous les patients doivent être surveillés étroitement en post-opératoire.

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Presented at the 50th Annual Meeting of the Canadian Anaesthetists’ Society, Halifax, June 4–8, 1993.     

Effect of the factor VII R353Q missense mutation on plasma apolipoprotein B levels: impact of visceral obesity

An atherogenic dyslipidemia, characterized by increased plasma triglyceride and apolipoprotein (apo) B levels, low HDL-cholesterol concentrations and the development of small, dense LDL particles has been associated with the presence of abdominal-visceral obesity. Visceral obesity is also associated with a hypercoagulate state and elevated concentrations of procoagulant factors such as factor VII. Moreover, it is known that some genetic variants in the gene encoding factor VII alter its activity and concentration, and consequently these variants may have an impact on atherosclerosis development. The objective of this study was to verify whether the factor VII R353Q polymorphism contributes to predict the risk of an atherogenic dyslipidemia in absence and in the presence of visceral obesity. A sample of 299 French-Canadian men, selected in order to cover a wide range of body fatness values, participated in this study. We observed that the R353 allele was more commonly observed among men characterized by apo B levels below 1.09 g/l than among men with apo B levels greater or above this threshold value (allele frequency of 92.1 vs 85.4%, ²=6.18, P=0.01). Multivariate analyses further showed that the genotype R353/R353 was associated with a lower risk to exhibit atherogenic concentrations of total-apo B (1.09 g/l) and LDL apo B (0.95 g/l) before (odds ratio:0.47, 95%CI=0.27–0.90, P=0.02; odds ratio:0.46, 95%CI=0.25–0.85, P=0.01, respectively) and after adjustments for age and visceral AT (odds ratio:0.49, 95%CI=0.24–0.91, P=0.02; odds ratio:0.44, 95%CI=0.23-0.85, P=0.01, respectively). When the two genotype groups were further divided on the basis of visceral adipose tissue (AT) accumulation using a cutoff point of 130 cm², we observed that R353/R353 homozygotes with low visceral AT were characterized by a more favorable lipoprotein-lipid profile, mainly lower total-cholesterol, total-apo B, and LDL-apo B levels compared with R353/R353 homozygotes with high levels of visceral AT. In contrast, irrespective of obesity, plasma lipid levels among carriers of the Q353 allele were similar to those of viscerally obese men homozygous for the R353 allele. In conclusion, results of the present study suggest that the factor VII R353 allele is associated with lower concentrations of plasma apo B levels. However, the presence of visceral obesity abolishes this effect. Further studies will be necessary to confirm this association and the mechanism involved.     

EMG activation patterns during force production in precision grip

Electromyographic (EMG) activity was analyzed for the occurrence of synergistic patterns during the steady hold periods of force in the precision grip. To establish the presence of muscle synergies in the amplitude (spatial) domain, the EMG activation levels of pairs of simultaneously active muscles were linearly correlated. Cross-correlations of EMG activity were computed to quantify muscle synergies in the spatiotemporal domain (synchronization). A muscle pair was defined to be synergistically coupled or synchronously activated when the correlation (amplitude domain) or cross-correlation (time domain) was significant for at least two of the three steady state force levels. Muscle synergies in the amplitude domain were found in one-third of the 213 muscle pairs tested, distributed among 47 of the 82 tested muscle combinations. Coactivation was the predominant synergistic pattern, whereas trade-off comprised not more than 23% of the synergies. Cross-correlation peak size varied between 5 and 39% of the autocorrelation size, with delays in the range of ±8 ms and base width between 12 and 20 ms. Synchronization was found in one-fourth of the 213 muscle pairs tested and among 35 of the 82 muscle combinations, i.e., less frequently than covariation of EMG activity levels. However, the interindividual prevalence was higher for synchronization than for synergies in the amplitude domain, since, for the synergistic muscle combinations, almost twice as many muscle pairs were found to be synchronized than coupled in the amplitude domain. Synergies in the two domains occurred independently in some pairs and concurrently in other cases, and were observed between muscles moving the thumb, the index finger, or both digits. Synchronization was more frequent in pairs of muscles supplied by branches of the same peripheral nerve (46%) than in those innervated by different nerves (18%). Synergies in the amplitude domain were distributed in similar proportions across intrinsic, extrinsic, and combinations of both types of muscles, whereas synchronization mainly occurred in pairs of intrinsic muscles. When the task was repeated with slightly lower target forces, there were fewer synergies in the amplitude domain (in 52 of the 213 pairs, distributed among 35 of 82 muscle combinations) and their distribution changed, indicating a flexible, force-dependent mechanism. In conclusion, no strictly coherent interindividual pattern of synergies in the spatial domain could be established.     

Parental origin and mechanisms of formation of three eases of 12p tetrasomy

Pallister-Killian syndrome is a clinically recognizable syndrome characterized by tissue-limited mosaicism for an extra 12p isochromosome. Very little is known about the underlying mechanism of this rare rearrangement. Microsatellite markers were studied from three fetuses with Pallister-Killian syndrome and their parents to determine the parent of origin and the cell division yielding the additional isochromosome. In two cases the isochromosome contained the same allele(s) as a normal transmitted chromosome 12, one paternal and one maternal in origin. A third case showed inheritance of two different maternal alleles, indicating that at least one meiotic error was involved in the ultimate formation of the extra isochromosome.     

Humoral immunity reflects altered T helper cell bias in Borrelia burgdorferi-infected gamma delta T-cell-deficient mice

In murine Lyme borreliosis, the absence of gamma delta T lymphocytes augments the T helper cell 2 type humoral response but does not alter disease susceptibility. Arthropod transmission of Borrelia burgdorferi spirochetes results in similar antibody isotypes when gamma delta T cells are present, suggesting that vector effects can negate gamma delta T-cell functions in vivo.     

Conventional liquid-based techniques versus Cytyc Thinprep<Superscript>®</Superscript> processing of urinary samples: a qualitative approach

Background

The aim of our study was to objectively compare Cytyc Thinprep^® and other methods of obtaining thin layer cytologic preparations (cytocentrifugation, direct smearing and Millipore^® filtration) in urine cytopathology.

Methods

Thinprep slides were compared to direct smears in 79 cases. Cytocentrifugation carried out with the Thermo Shandon Cytospin^® 4 was compared to Thinprep in 106 cases, and comparison with Millipore filtration followed by blotting was obtained in 22 cases. Quality was assessed by scoring cellularity, fixation, red blood cells, leukocytes and nuclear abnormalities.

Results

The data show that 1) smearing allows good overall results to be obtained, 2) Cytocentrifugation with reusable TPX^® chambers should be avoided, 3) Cytocentrifugation using disposable chambers (Cytofunnels^® or Megafunnel^® chambers) gives excellent results equalling or surpassing Thinprep and 4) Millipore filtration should be avoided, owing to its poor global quality. Despite differences in quality, the techniques studied have no impact on the diagnostic accuracy as evaluated by the rate of abnormalities.

Conclusion

We conclude that conventional methods such as cytocentrifugation remain the most appropriate ones for current treatment of urinary samples. Cytyc Thinprep processing, owing to its cost, could be used essentially for cytology-based molecular studies.

     

Synchrotron stereotactic radiotherapy: dosimetry by Fricke gel and Monte Carlo simulations

Synchrotron stereotactic radiotherapy (SSR) consists in loading the tumour with a high atomic number element (Z), and exposing it to monochromatic x-rays from a synchrotron source (50-100 keV), in stereotactic conditions. The dose distribution results from both the stereotactic monochromatic x-ray irradiation and the presence of the high Z element. The purpose of this preliminary study was to evaluate the two-dimensional dose distribution resulting solely from the irradiation geometry, using Monte Carlo simulations and a Fricke gel dosimeter. The verification of a Monte Carlo-based dosimetry was first assessed by depth dose measurements in a water tank. We thereafter used a Fricke dosimeter to compare Monte Carlo simulations with dose measurements. The Fricke dosimeter is a solution containing ferrous ions which are oxidized to ferric ions under ionizing radiation, proportionally to the absorbed dose. A cylindrical phantom filled with Fricke gel was irradiated in stereotactic conditions over several slices with a continuous beam (beam section = 0.1 x 1 cm2). The phantom and calibration vessels were then imaged by nuclear magnetic resonance. The measured doses were fairly consistent with those predicted by Monte Carlo simulations. However, the measured maximum absolute dose was 10% underestimated regarding calculation. The loss of information in the higher region of dose is explained by the diffusion of ferric ions. Monte Carlo simulation is the most accurate tool for dosimetry including complex geometries made of heterogeneous materials. Although the technique requires improvements, gel dosimetry remains an essential tool for the experimental verification of dose distribution in SSR with millimetre precision.     

An objective method to measure cell survival by computer-assisted image processing of numeric images of Petri dishes

This work establishes an objective method to measure cell clonogenic survival by computer-assisted image processing using images of cell cultures fixed and stained in Petri dishes. The procedure, developed by Samba Technologies, consists of acquiring Petri dish pictures with a desktop scanner and analysing them by computer, using algorithms based on the 'top hat' filter. The results from the automated count for the cell line SQ20B are compared with those found by two observers, before and after normalization of the counting. After normalization, the shape of the survival curves of the 'manual' counting of the Petri dishes shows a good correlation between both observers. The software enables the small visible differences in count between observers to be eliminated. The comparison between the absolute number of colonies shows an increased difference between the two manual scorings that can be as great as 67 colonies, whereas the difference between the two automated counts is never greater than 8 colonies. These results demonstrate that the 'manual' count is inter- and intraobserver variable, whereas the automatic count performs reproducible cell colony counts, thereby minimizing user-generated bias. The large amount of data produced also gives information about cell and colony characteristics. Thus, this computer-assisted method has considerably improved the reliability of our statistical results.