Calculation of the Residual Blood Volume after Acute, Non-Ongoing Hemorrhage Using Serial Hematocrit Measurements and the Volume of Isotonic Fluid Infused: Theoretical Hypothesis Generating Study

Fluid resuscitation, hemostasis, and transfusion is essential in care of hemorrhagic shock. Although estimation of the residual blood volume is crucial, the standard measuring methods are impractical or unsafe. Vital signs, central venous or pulmonary artery pressures are inaccurate. We hypothesized that the residual blood volume for acute, non-ongoing hemorrhage was calculable using serial hematocrit measurements and the volume of isotonic solution infused. Blood volume is the sum of volumes of red blood cells and plasma. For acute, non-ongoing hemorrhage, red blood cell volume would not change. A certain portion of the isotonic fluid would increase plasma volume. Mathematically, we suggest that the residual blood volume after acute, non-ongoing hemorrhage might be calculated as 0·25N/[(Hct1/Hct2)-1], where Hct1 and Hct2 are the initial and subsequent hematocrits, respectively, and N is the volume of isotonic solution infused. In vivo validation and modification is needed before clinical application of this model.

Dry weight evaluation in hemodialysis patients / 中华肾脏病杂志

Objective To estimate dry weight (DW) and prevent dialysis-related hypotension and hypertension with the on-line monitoring of relative blood volume (RBV) and other judgments.Methods One hundred and eight maintenance hemodialysis patients were assigned to three groups according to their blood pressure:normal blood pressure group (A group,n=43),hypotension group (B group,n=35) and hypertension group (C group,n=35).The level of hemoglobin,serum albumin,dialysis adequacy were determined.Systolic blood pressure,diastolic blood pressure,mean arterial pressure,heart rate,ultrafiltration volume,relative blood volume changes and the corresponding clinical symptoms were monitored during hemodialysis in all patients.Each of the patients was continuously monitored of the indicators above for 10-12 times.At the observing period,the inferior vena cava diameter (IVCD),brain natriuretic peptide (BNP) and cardiothoracic ratio(CTR) were measured.Then according to the monitoring results,appropriate clinical interventions were given under on-line blood volume monitoring guidance.Results (1)The shape of RBV curve in group A showed doubleexponential curve early,then down to the final linear decling ended during hemodialysis.(2)The RBV curve in group B was stable in the former two hours,then rapidly linear declined.RBV changes were significantly higher in group B than group A (P ＜ 0.05),but when changes in RBV were plotted against ultrafiltration volume,there was no significant difference in the two groups.The level of RBV reduction at which symptomatic hypotension occurred showed considerable inter-individual variability (P ＜ 0.05,coefficient of variation=0.28).(3)The RBV curve in group C slowly linear declined.At the end of dialysis,RBV changes were significantly lower in group C than group A (P ＜ 0.05).(4)The IVCD values in three groups of patients before dialysis were greater than normal,significantly decreased after the dialysis (P ＜ 0.05),but that in group B and group C were still greater than that in group A (P ＜ 0.05).The BNP values were significantly greater in three groups before and after dialysis (P ＜ 0.05),but after dialysis,the values decreased significantly than that before dialysis (P ＜ 0.05).(5)After appropriate clinical intervention were given under on-line blood volume monitoring in hemodialysis,the patients of group B controlled weight gain,and even cut dry weight,the RBV change significantly decreased at the end of dialysis and significantly reduced the incidence of hypotension events (P ＜ 0.05); When the patients of group C cut dry weight,increased ultrafiltration,the RBV change increased,the mean arterial pressure decreased significantly than before (P＜ 0.05).Conclusions (1)Hemodialysis patients with symptomatic hypotension show larger RBV decline rate in the forth hour and lager total RBV changes,which provides important information for forecasting the symptomatic hypotension in hemodialysis.(2)IVCD and CTR have certain significance to the adjustment of dry weight,but the BNP has guiding significance to volume change.(3)On-line monitoring of RBV can effectively guide the adjustment of dry weight,reduction of symptomatic hypotension occruence,and controlling of refractory hypertension in hemodialysis.

Avaliação da responsividade a volume em pacientes sob ventilação espontânea: [revisão] / Assessment of fluid responsiveness in patients under spontaneous breathing activity~: [review]

A avaliação da responsividade a volume no paciente em ventilação espontânea representa um desafio para o intensivista. A maior parte dos conhecimentos adquiridos sobre interação coração-pulmão e o cálculo de índices dinâmicos de responsividade a fluidos podem não ser adequados para essa avaliação. Historicamente, as variáveis mais frequentemente utilizadas para guiar a responsividade a volume têm sido as medidas estáticas de pré-carga. Mais recentemente, índices dinâmicos obtidos por dispositivos menos invasivos têm sido mais usados, apesar de sua eficácia para esse fim em pacientes em ventilação espontânea ainda não ter sido adequadamente estabelecida. O objetivo deste estudo foi revisar as principais evidências sobre a avaliação da responsividade a volume nos pacientes em ventilação espontânea. A pesquisa na literatura demonstrou escassez nas evidências para utilização de medidas estáticas da volemia como as pressões de enchimento e o volume diastólico final dos ventrículos. Medidas dinâmicas como variação da pressão de pulso e outros índices também não foram adequadamente testados durante a ventilação espontânea. Resultados favoráveis foram obtidos com a variação dinâmica da pressão venosa central e com parâmetros dinâmicos que utilizam o ecocardiograma transtorácico ou doppler esofágico associado à elevação passiva dos membros inferiores. Conclui-se que embora a variação da pressão venosa central e variáveis obtidas com o ecocardiograma transtorácico ou doppler esofágico possam ser úteis na avaliação da responsividade a volume em pacientes sob ventilação espontânea, definitivamente são necessários mais estudos neste grupo de pacientes.

To assess fluid responsiveness in patients under spontaneous breathing activity ventilation remains a challenge for intensive care physicians. Much of the knowledge on heart-lung interactions and dynamic indexes of fluid responsiveness may not be useful for these patients. Historically, the most frequently used variables to guide fluid responsiveness on this population have been the static preload indexes. However, more recently, dynamic indexes from less invasive devices are being often used, even though their usefulness on spontaneously-breathing subjects remains controversial. The purpose of this article was to review evidences on the assessment of fluid responsiveness in patients under spontaneous ventilation. A search in literature showed poor evidence for use of static variables, such as filling pressures and ventricular end-diastolic volumes. Dynamic indexes, such as pulse pressure variation and other indexes had not been appropriately tested during spontaneous ventilation. Favorable results were found with central venous pressure variation and with transthoracic echocardiography or transesophageal Doppler dynamic indexes, especially when associated to passive lower limb elevation. We conclude that although central venous pressure variation and echocardiography variables could aid bedside clinicians in assessing fluid responsiveness during spontaneous ventilation, more studies on this subject are definitely required.

Assessment of Fluid Shifts of Body Compartments using Both Bioimpedance Analysis and Blood Volume Monitoring

Fluid shifts are commonplace in chronic hemodialysis patients during the intra- and interdialytic periods. In this study, we evaluated fluid shifts of body compartments using both bioimpedance spectroscopy and blood volume monitoring from the start to the end of hemodialysis. 24 stable hemodialysis patients were included on the study. Relative change of blood volume was progressively reduced from the start to the end of hemodialysis (1 hr, -7.22+/-3.23%; 2 hr, -9.78+/-4.69%; 3 hr, -12.88+/-5.65%; 4 hr, -15.41+/-6.54%, respectively). Mean % reduction of intracellular fluid was not significantly different to that of extracellular fluid at the end of hemodialysis (delta ICF, -6.58+/-5.34% vs. delta ECF, -7.07+/-5.12%). Mean % fluid reduction of arms, legs and trunk was -11.98+/-6.76%, -6.43+/-4.37% and -7.47+/-4.56%, respectively at the end of hemodialysis. There were 3 characteristic patterns in blood-volume change. Similar amounts of fluid were removed from the extracellular and intracellular compartments during hemodialysis, with the arms showing the greatest loss in terms of body segments. The pattern of blood volume change measured by blood volume monitoring may be useful for more accurate determination of dry-weight and for correcting volume status in hemodialysis patients.

Effects of point contact-dynamic compression plate on cortical bone blood flow in adult goats / 中华创伤杂志

Objective To compare the effects of point contact-dynamic compression plates (PC-DCP) and dynamic compression plates (DCP) on cortical bone blood flow in an intact sheep tibia model. Methods Fifteen mature goats were used in this experiment. After the bilateral tibia of goats were fixed with DCP and PC-DCP respectively, the regional cortical bone blood flow was measured at four time intervals (1 day, 2, 6 and 12 weeks after operation) using radiolabelled microsphere technique. Results After operation, the cortical bone blood flow was acutely decreased at the first day, kept lower than normal level until six weeks and recovered at the 12th week. The blood supply under PC-DCP recovered to normal, even over normal level two weeks after operation and remained at a high level until 12 weeks. Conclusions PC-DCP can markedly protect cortical bone blood flow.