Prediction of hematocrit decline and the impact of peri-operative fluid use in lumbar spinal fusion surgery

PURPOSE

Peri-operative blood loss unaccounted for and post-operative hematocrit decline could have a significant impact on the outcome of elective spinal surgery patients. The study assesses the accuracy of predictive models of hematocrit decline and blood loss in spinal surgery and determines the impact of peri-operative fluid administration on hematocrit levels of patients undergoing first-time single level lumbar fusion surgery for degenerative spine disease and the trend thereof in the first 24 h post-operatively.

METHODS

Clinical and biochemical parameters were prospectively collected in patients undergoing single level lumbar spinal surgery. Predictive models were applied to assess their accuracy in intra-operative blood loss and post-operative hematocrit decline.

RESULTS

High correlation (0.98 Pearson correlation coefficient) occurred between calculated (predicted) and recorded hematocrit from hours 2 to 6 post-operatively. Predictive accuracy declined thereafter yet remained moderate. Patients received an average intra-operative fluid volume of 545.45 ml per hour (47% of estimated total blood volume). A significant hematocrit decline occurred post-induction (43.47-39.78%, p < 0.001) with total fluid volume received being the significant contributing variable (p < 0.001). Hypertensive patients were the only subgroup to drop below the safe hematocrit threshold of 30%.

CONCLUSION

Iatrogenic hemodilution can accurately be predicted for the first six hours post-operatively, with high risk patients identifiable. Fluid therapy should be goal directed rather than generic, and good communication between the surgeon and anesthesiologist remains the cornerstone to manage physiological changes secondary to blood loss. Although helpful, predictive formulas are not universally applicable to all phenotypes.

A novel amplitude binning strategy to handle irregular breathing during 4DMRI acquisition: improved imaging for radiotherapy purposes

Background

For radiotherapy of abdominal cancer, four-dimensional magnetic resonance imaging (4DMRI) is desirable for tumor definition and the assessment of tumor and organ motion. However, irregular breathing gives rise to image artifacts. We developed a outlier rejection strategy resulting in a 4DMRI with reduced image artifacts in the presence of irregular breathing.

Methods

We obtained 2D T2-weighted single-shot turbo spin echo images, with an interleaved 1D navigator acquisition to obtain the respiratory signal during free breathing imaging in 2 patients and 12 healthy volunteers. Prior to binning, upper and lower inclusion thresholds were chosen such that 95% of the acquired images were included, while minimizing the distance between the thresholds (inclusion range (IR)). We compared our strategy (Min95) with three commonly applied strategies: phase binning with all images included (Phase), amplitude binning with all images included (MaxIE), and amplitude binning with the thresholds set as the mean end-inhale and mean end-exhale diaphragm positions (MeanIE). We compared 4DMRI quality based on:

Data included (DI); percentage of images remaining after outlier rejection.

Reconstruction completeness (RC); percentage of bin-slice combinations containing at least one image after binning.

Intra-bin variation (IBV); interquartile range of the diaphragm position within the bin-slice combination, averaged over three central slices and ten respiratory bins.

IR.

Image smoothness (S); quantified by fitting a parabola to the diaphragm profile in a sagittal plane of the reconstructed 4DMRI.

A two-sided Wilcoxon’s signed-rank test was used to test for significance in differences between the Min95 strategy and the Phase, MaxIE, and MeanIE strategies.

Results

Based on the fourteen subjects, the Min95 binning strategy outperformed the other strategies with a mean RC of 95.5%, mean IBV of 1.6 mm, mean IR of 15.1 mm and a mean S of 0.90. The Phase strategy showed a poor mean IBV of 6.2 mm and the MaxIE strategy showed a poor mean RC of 85.6%, resulting in image artifacts (mean S of 0.76). The MeanIE strategy demonstrated a mean DI of 85.6%.

Conclusions

Our Min95 reconstruction strategy resulted in a 4DMRI with less artifacts and more precise diaphragm position reconstruction compared to the other strategies.

Trial registration

Volunteers: protocol W15_373#16.007; patients: protocol NL47713.018.14

Electronic supplementary material

The online version of this article (10.1186/s13014-019-1279-z) contains supplementary material, which is available to authorized users.

Comprehensive approach to study complement C4 in systemic lupus erythematosus: Gene polymorphisms, protein levels and functional activity

Genetic variation of the genes encoding complement component C4 is strongly associated with systemic lupus erythematosus (SLE), a chronic multi-organ auto-immune disease. This study examined C4 and its isotypes on a genetic, protein, and functional level in 140 SLE patients and 104 healthy controls. Gene copy number (GCN) variation, silencing CT-insertion, and the retroviral HERV-K(C4) insertion) were analyzed with multiplex ligation-dependent probe amplification. Increased susceptibility to SLE was found for low GCN (≪2) of C4A. Serositis was the only clinical manifestation associated with low C4A GCN. One additional novel silencing mutation in the C4A gene was found by Sanger sequencing. This mutation causes a premature stop codon in exon 11. Protein concentrations of C4 isoforms C4A and C4B were determined with ELISA and were significantly lower in SLE patients compared to healthy controls. To study C4 isotypes on a functional level, a new C4 assay was developed, which distinguishes C4A from C4B by its binding capacity to amino or hydroxyl groups, respectively. This assay showed high correlation with ELISA and detected crossing over of Rodgers and Chido antigens in 3.2% (8/244) of individuals. The binding capacity of available C4 to its substrates was unaffected in SLE. Our study provides, for the first time, a complete overview of C4 in SLE from genetic variation to binding capacity using a novel test. As this test detects crossing over of Rodgers and Chido antigens, it will allow for more accurate measurement of C4 in future studies.

Determination of diuron and the antifouling paint biocide irgarol 1051 in Dutch marinas and coastal waters

A sensitive LC-electrospray MS-MS method using off-line solid-phase extraction for the determination of diuron and Irgarol 1051 has been developed, enabling determination of both compounds at sub-ppt levels. Diuron and Irgarol 1051 are used as alternatives for tributyltin in antifouling paints that prevent growth on boats, and an increase in their application is anticipated because of the upcoming ban on tributyltin in 2003. In 2000, a survey was carried out to assess contamination with diuron and Irgarol 1051 of a number of Dutch marinas and coastal waters. Depending on the time of year, both compounds were encountered at levels higher than the maximum permissible concentrations of 430 and 24 ng/l for diuron and Irgarol 1051, respectively. Outside marinas at reference locations, concentrations were much lower, depending on the geographical situation and the nature of the water exchange with the environment related to tidal cycles. A seasonal influence was observed with highest levels in summer, corresponding to the yachting season for both compounds. For diuron, use in agriculture could have contributed to the high concentration encountered in surface waters.

Planning, computer optimization, and dosimetric verification of a segmented irradiation technique for prostate cancer

PURPOSE

To develop and verify a multisegment technique for prostate irradiation that results in better sparing of the rectal wall compared to a conventional three-field technique, for patients with a concave-shaped planning target volume (PTV) overlapping the rectal wall.

METHODS AND MATERIALS

Five patients have been selected with various degrees of overlap between PTV and rectal wall. The planned dose to the ICRU reference point is 78 Gy. The new technique consists of five beams, each having an open segment covering the entire PTV and several smaller segments in which the rectum is shielded. Segment weights are computer-optimized using an algorithm based on simulated annealing. The score function to be minimized consists of dose-volume constraints for PTV, rectal wall, and femoral heads. The resulting dose distribution is verified for each patient by using point measurements and line scans made with an ionization chamber in a water tank and by using film in a cylindrical polystyrene phantom.

RESULTS

The final number of segments in the five-field technique ranges from 7 to 9 after optimization. Compared to the standard three-field technique, the maximum dose to the rectal wall decreases by approximately 3 Gy for patients with a large overlap and 1 Gy for patients with no overlap, resulting in a reduction of the normal tissue complication probability (NTCP) by a factor of 1.3 and 1.2, respectively. The mean dose to the PTV is the same for the two techniques, but the dose distribution is slightly less homogeneous with the five-field technique (Average standard deviation of five patients is 1.1 Gy and 1.7 Gy for the three-field and five-field technique, respectively). Ionization chamber measurements show that in the PTV, the calculated dose is in general within 1% of the measured dose. Outside the PTV, systematic dose deviations of up to 3% exist. Film measurements show that for the complete treatment, the position of the isodose lines in sagittal and coronal planes is calculated fairly accurately, the maximum distance between measured and calculated isodoses being 4 mm.

CONCLUSIONS

We developed a relatively simple multisegment "step-and-shoot" technique that can be delivered within an acceptable time frame at the treatment machine (Extra time needed is approximately 3 minutes). The technique results in better sparing of the rectal wall compared to the conventional three-field technique. The technique can be planned and optimized relatively easily using automated procedures and a predefined score function. Dose calculation is accurate and can be verified for each patient individually.

Cardiac and lung complication probabilities after breast cancer irradiation

PURPOSE

To assess for locoregional irradiation of breast cancer patients, the dependence of cardiac (cardiac mortality) and lung (radiation pneumonitis) complications on treatment technique and individual patient anatomy.

MATERIALS AND METHODS

Three-dimensional treatment planning was performed for 30 patients with left-sided breast cancer and various breast sizes. Two locoregional techniques (Techniques A and B) and a tangential field technique, including only the breast in the target volume, were planned and evaluated for each patient. In both locoregional techniques tangential photon fields were used to irradiate the breast. The internal mammary (IM)-medial supraclavicular (MS) lymph nodes were treated with an anterior mixed electron/photon field (Technique A) or with an obliquely incident mixed electron/photon IM field and an anterior electron/photon MS field (Technique B). The optimal IM and MS electron field dimensions and energies were chosen on the basis of the IM-MS lymph node target volume as delineated on CT-slices. The position of the tangential fields was adapted to match the IM-MS fields. Dose-volume histograms (DVHs) and normal tissue complication probabilities (NTCPs) for the heart and lung were compared for the three techniques. In the beam's eye view of the medial tangential fields the maximum distance of the heart contour to the posterior field border was measured; this value was scored as the Maximum Heart Distance.

RESULTS

The lymph node target volume receiving more than 85% of the prescribed dose was on average 99% for both locoregional irradiation techniques. The breast PTV receiving more than 95% of the prescribed dose was generally smaller using Technique A (mean: 90%, range: 69-99%) than using Technique B (mean: 98%, range: 82-100%) or for the tangential field technique (mean: 98%, range: 91-100%). NTCP values for excess cardiac mortality due to acute myocardial ischemia varied considerably between patients, with minimum and maximum values of 0.1 and 7.5% (Technique A), 0.1 and 5.8% (Technique B) and 0.0 and 6.1% (tangential tech.). The NTCP values were on average significantly higher (P<0.001) by 1.7% (Technique A) and 1.0% (Technique B) when locoregional breast irradiation was given, compared with irradiation of the left breast only. The NTCP values for the tangential field technique could be estimated using the Maximum Heart Distance. NTCP values for radiation pneumonitis were very low for all techniques; between 0.0 and 1.0%.

CONCLUSIONS

Technique B results in a good coverage of the breast and locoregional lymph nodes, while Technique A sometimes results in an underdosage of part of the target volume. Both techniques result in a higher probability of heart complications compared with tangential irradiation of the breast only. Irradiation toxicity for the lung is low in all techniques. The Maximum Heart Distance is a simple and useful parameter to estimate the NTCP values for cardiac mortality for tangential breast irradiation.

Beam intensity modulation to reduce the field sizes for conformal irradiation of lung tumors: a dosimetric study

PURPOSE

In conformal radiotherapy of lung tumors, penumbra broadening in lung tissue necessitates the use of larger field sizes to achieve the same target coverage as in a homogeneous environment. In an idealized model configuration, some fundamental aspects of field size reduction were investigated, both for the static situation and for a moving tumor, while maintaining the dose homogeneity in the target volume by employing a simple beam-intensity modulation technique.

METHODS AND MATERIALS

An inhomogeneous phantom, consisting of polystyrene, cork, and polystyrene layers, with a 6 x 6 x 6 cm3 polystyrene cube inside the cork representing the tumor, was used to simulate a lung cancer treatment. Film dosimetry experiments were performed for an AP-PA irradiation technique with 8-MV or 18-MV beams. Dose distributions were compared for large square fields, small square fields, and intensity-modulated fields in which additional segments increase the dose at the edge of the field. The effect of target motion was studied by measuring the dose distribution for the solid cube, displaced with respect to the beams.

RESULTS

For the 18-MV beam, the field sizes required to establish a sufficient target coverage are larger than for the 8-MV beam. For each beam energy, the mean dose in cork can significantly be reduced (at least a factor of 1.6) by decreasing the field size with 2 cm, while keeping the mean target dose constant. Target dose inhomogeneity for these smaller fields is limited if the additional edge segments are applied for 8% of the number of monitor units given with the open fields. The target dose distribution averaged over a motion cycle is hardly affected if the target edge does not approach the field edge to within 3 mm.

CONCLUSIONS

For lung cancer treatment, a beam energy of 8 MV is more suitable than 18 MV. The mean lung dose can be significantly reduced by decreasing the field sizes of conformal fields. The smaller fields result in the same biological effect to the tumor if the mean target dose is kept constant. Intensity modulation can be employed to maintain the same target dose homogeneity for these smaller fields. As long as the target (with a 3 mm margin) stays within the field portal, application of a margin for target motion is not necessary.

Dosimetric verification of the 95% isodose surface for a conformal irradiation technique

In the treatment planning of conformal radiotherapy, field shapes are often designed in such a way that a high-value isodose surface fully encompasses the target volume. Therefore, knowledge about the accuracy with which the treatment planning system calculates the position of that isodose surface is essential to prevent field shapes which are either too large or too small. To determine this accuracy for a conformal multi-field technique, the dose in the high-dose region must be measured with a high spatial resolution. A method is presented to reconstruct and evaluate the experimental high-dose region from a set of water phantom scans. This method, which assesses combined dose profiles for multi-field irradiation techniques, can be used for the commissioning and/or quality assurance of a 3-D treatment planning system. For a specific conformal technique, the measured and calculated 95% isodose positions along lines in several directions have been compared. It is shown that different dose values of single beam profiles determine the resulting 95% isodose position, which is important to recognize for quality assurance of treatment planning calculations. It is further found that the uncertainty in the calculated 95% isodose surface can be described by a standard deviation in dose value, which relates to a positional uncertainty through the local dose gradient. Thus the confidence region of the calculated 95% isodose can be indicated in the treatment plan by plotting isodoses at the 95% level plus and minus its standard deviation. Such a procedure is recommended instead of plotting the 95% isodose with a constant width. In addition, restrictions for the cumulative dose-volume histogram of acceptable treatment plans can be formulated, based on the sensitivity of the actual target coverage on the uncertainty with which the prescribed isodose surface is calculated.

Energy cost of physical activities in healthy elderly women

In recent studies, daily physical activity ratios (PARs) greater than the Food and Agriculture Organization/World Health Organization/United Nations University (FAO/WHO/UNU) reference value of 1.5 have been reported for elderly men and women. The purpose of this study was to investigate whether a high PAR in elderly subjects can be explained by a higher energy cost of physical activities (EEact). To this end, 12 elderly women aged 69 to 82 years, completed physical activity diaries during a 2-day stay in a respiration chamber. From these diaries, total daily energy expenditure (TEE) in the calorimeter was estimated (TEEfac) using FAO/WHO/UNU PARs for physical activities and measured resting metabolic rate (RMR). TEEfac was 7.0 +/- 0.9 MJ/d (PAR, 1.35 +/- 0.06). TEE was also measured in the chamber (TEEcal) and was 8.3 +/- 1.3 MJ/d (PAR, 1.60 +/- 0.16). TEEfac was 14.8% +/- 8.1% lower than TEEcal. To investigate whether the underestimation of TEEcal was due to a higher EEact in the elderly women as compared with the FAO/WHO/UNU references, EEact of six specific activities ranging from sitting at rest to walking on a treadmill at self-chosen speed was measured with a ventilated-hood system. Individually measured PARs of the six activities were similar to FAO/WHO/UNU reference PARs. This study suggests that in elderly women a high TEEcal is not explained by EEact during nonstandardized physical activities performed at self-chosen speeds. Whether these results can be extrapolated to the free-living environment needs to be investigated further.

Determination of 4-aminopyridine in serum by solid-phase extraction and high-performance liquid chromatography

An assay for the determination of 4-aminopyridine in serum has been developed using 3,4-diaminopyridine as internal standard and reversed-phase high-performance liquid chromatography with detection at 244 nm. A mobile phase of acetonitrile-methanol-ethanol-1% ammonium carbonate (75:10:10:5) provided excellent separation of both compounds. Samples were extracted on solid-phase columns. The linearity, precision, recovery and the limit of detection were all sufficient for the routine use of this assay in clinical studies of patients treated with 4-aminopyridine.

Analysis of water-soluble vitamins in total parenteral nutrition solution by high pressure liquid chromatography

A stability-indicating high pressure liquid chromatographic method was developed to determine the stability of water-soluble vitamins in total parenteral nutrition mixtures. Folic acid and thiamine were determined by direct injection and precolumn enrichment, followed by UV detection. Nicotinamide and pyridoxine were determined simultaneously without sample pretreatment by UV detection of nicotinamide and fluorescence detection of pyridoxine. Riboflavin 5'-phosphate was also determined without elaborate sample handling and by fluorescence detection. Ascorbic acid was determined as the sum of ascorbic acid and dehydroascorbic acid. After derivatization to a quinoxaline the latter substance was determined by direct injection and fluorescence detection.

Quality improvement of patient care: some preliminary results of a hospital-wide quality-assurance project at the University Hospital of Maastricht

Dutch hospitals have to design their quality-assessment programmes within the boundaries set by "indirect government legislation". At the University hospital of Maastricht a five-stage project was started in 1985 to construct a hospital-wide quality-assurance organisation that includes regular review of the quality of professional performance. This paper will describe intermediate results of the first stage and will discuss the results of different subsurveys undertaken to assess the current level of quality of care and several key-issues conditional to the implementation of such a hospital-wide structure in the existing organisation of a University hospital. Finally the results of the first stage will be contrasted with external legislative standards and internal needs of the University hospital recognised during assessment of the current situation.