Hematocrit

Blood is composed of a cellular portion, the formed elements, suspended in plasma. The formed elements constitute approximately 40—45% of the blood volume, ie, the hematocrit. When a test tube with blood is centrifuged, the formed elements are packed onto the bottom of the tube, leaving plasma on top... 

Periodic platelet counts, hematocrit, and tests for occult blood in die stool should be performed throughout die entire course of heparin therapy. 

When monitoring the patient taking epoetin, the nurse reportsany increase in the hematocrit of 4 points within any 2-week period because an exacerbation of hypertension is associated with an excessive rise of hematocrit. Hematocrit is decreased by decreasing or withholding the epoetin alfa dose. 

A. Any increase in hematocrit of 4 points within a 2-week period... 

Figure 15. Appearance of a suspension of human red cells when frozen to -4 °C. The initial hematocrit was 20% in (A) and 2% in (B). Note that as in Figure 8, the cells lie in unfrozen channels between the ice crystals. (From Nei, 1981.)...

Hematological Effects. No information was found regarding hematological effects in humans following exposure to methyl parathion. Repeated oral exposure to methyl parathion resulted in decreased mean corpuseular volume in one study and decreased hematocrit and erythrocyte count in another study in rats. Chronic ingestion of methyl parathion induced reduction of mean hemoglobin, hematocrit, and erythrocyte eounts in rats. 

ATSDR has derived a chronic-duration oral MRL of. 0003 mg/kg/day for methyl parathion based on a NOAEL of 0.025 mg/kg/day for reduced hematocrit and erythrocyte counts in rats (Suba 1984). 

EPA has derived an RfD of. 00025 mg/kg/day, based on a NOAEL of 0.025 for reduced hematocrit, erythrocyte counts, and hemoglobin (cholinesterase inhibition was also listed as a critical effect but the reason for this was not explained). This NOAEL appears to be from the same study as for the ATSDR chronic-duration oral MRL, although the study is referenced differently (IRIS 2001). 

Effects noted in study and corresponding concentrations No adverse effects were observed in the low-dose male and female rats. Mean hemoglobin, hematocrit, and erythrocyte counts were significantly reduced in the high-dose females at 6-24 months of treatment mean hematocrit and erythrocyte counts were significantly reduced in the mid- and high-dose males at 24 months of treatment. 

Concentration and end point used for MRL derivation 0.025 mg/kg/day decreased mean hematocrit and erythrocyte counts... 

Other additional studies or pertinent information that lend support to this MRL An intermediate-duration gavage study in rats found decreased hematocrit and erythrocyte counts relative to before-treatment values (Galal et al. 1977), but this study had some limitations, including lack of a control group and disparities between text and tables. Another intermediate duration gavage study in male rats demonstrated dose-related significant decreases in mean corpuscular volume (Undeger et al. 2000). An effect on the erythrocyte is plausible because erythrocyte cholinesterase has a function in the control of erythrocyte permeability (Wills 1972). 

Hematological Effects. Normal hemoglobin, hematocrit, white blood cell count, and differential... 

From the fingertip, earlobe or heel prick, one would like to stay within the limits of 100 - 200p 1 as a maximum. If one then draws 100 1 of blood, then one cannot hope to have more than approximately 40pi of plasma, since the hematocrit of newborn infants is relatively high. This volume would be substantially lowered, in the dehydrated infant, with which one is working, normally. 

Sakai F, Nakazawa K, Tazaki Y, Ishii K, Hino H, Igarashi H, Kanda T. Regional cerebral blood volume and hematocrit measured in normal human volunteers hy single-photon emission computed tomography. J Cereb Blood Flow Metab 1985 5 207-213. 

Ion-selective electrodes allow the measurement of ionic activity in diluted or undiluted whole blood, plasma or rum. The direct (undiluted) measurement may be preferred, since no sample pretreatment is necessary and the assay values are independent of hematocrit and amount of solids present. However, direct potentiometry by its very nature does not provide total concentration values similar to those obtained by flame photometry and indirect (diluted) potentiometry... 

If goal not achieved with fluid resuscitation and the hematocrit is >30%, then administer dobutamine continuous IV infusion (maximum dose of 20 mcg/kg/min)... 

Higher hematocrit may improve platelet-vessel wall interaction... 

Cocaine and intravenous drug use Low socioeconomic status Increased hematocrit Sickle cell disease... 

ASA, aspirin BP, blood pressure Hb, hemoglobin Hct, hematocrit ICP, intracranial pressure ICU, intensive care unit INR, International Normalized Ratio SAH, subarachnoid hemorrhage t-PA, tissue plasminogen activator. 

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