What Is Density Of Blood
J Vet Med. 2015; 2015: 152730.
Blood Density Is Well-nigh Equal to Water Density: A Validation Written report of the Gravimetric Method of Measuring Intraoperative Blood Loss
Dominic J. Vitello
aneSection of Anesthesiology, Jesse Brown VA Medical Eye, University of Illinois at Chicago, 820 South. Damen Avenue, Chicago, IL 60612, USA
Richard M. Ripper
1Department of Anesthesiology, Jesse Brown VA Medical Center, University of Illinois at Chicago, 820 S. Damen Artery, Chicago, IL 60612, U.s.a.
Michael R. Fettiplace
iDepartment of Anesthesiology, Jesse Brown VA Medical Heart, University of Illinois at Chicago, 820 South. Damen Avenue, Chicago, IL 60612, United states of america
Guy L. Weinberg
oneDepartment of Anesthesiology, Jesse Brown VA Medical Center, University of Illinois at Chicago, 820 Southward. Damen Avenue, Chicago, IL 60612, United states of america
Joseph M. Vitello
2Section of General Surgery, Jesse Chocolate-brown VA Medical Heart, University of Illinois at Chicago, 820 S. Damen Avenue, Chicago, IL 60612, USA
Received 2014 Oct 15; Accepted 2014 December i.
Abstract
Purpose. The gravimetric method of weighing surgical sponges is used to quantify intraoperative blood loss. The dry out mass minus the wet mass of the gauze equals the book of claret lost. This method assumes that the density of blood is equivalent to water (1 gm/mL). This report'southward purpose was to validate the assumption that the density of blood is equivalent to water and to correlate density with hematocrit. Methods. 50µL of whole blood was weighed from 18 rats. A distilled water control was weighed for each blood sample. The averages of the blood and water were compared utilizing a Pupil'southward unpaired, one-tailed t-test. The masses of the blood samples and the hematocrits were compared using a linear regression. Results. The boilerplate mass of the eighteen claret samples was 0.0489 g and that of the distilled water controls was 0.0492 g. The t-test showed P = 0.2269 and R two = 0.03154. The hematocrit values ranged from 24% to 48%. The linear regression R two value was 0.1767. Conclusions. The R 2 value comparing the blood and distilled water masses suggests high correlation betwixt the 2 populations. Linear regression showed the hematocrit was not proportional to the mass of the blood. The report confirmed that the measured density of blood is similar to water.
1. Introduction
The quantity of intraoperative claret loss is often determined using subjective visual estimation past the operating surgeon or anesthesiologist. Several studies document that this visual estimation may underestimate actual blood loss by as much equally 89% [1–five]. Some studies likewise study that as actual blood loss increases, estimated claret loss is increasingly inaccurate [6]. Accurately measuring blood loss during an operation tin assist with fluid resuscitation and the demand for transfusion. Overestimation of blood loss can lead to unnecessary transfusion practices. For inquiry purposes, precise measurement of intraoperative claret loss is critical to compare different operative techniques or the effects of medications on blood loss.
During most operations, the direct measurement of the volume of blood collected in suction canisters is the most mutual clinical method used to determine intraoperative blood loss. When the volume of claret loss is pocket-size, the gravimetric method is a simple, accurate, and clinically relevant measurement technique [vii]. With this method, surgical gauze sponges and laparotomy pads are weighed before and afterward utilize. The difference in their weight is generally believed to be an accurate measurement of claret loss. To catechumen the mass of blood to a more familiar volume statistic, noesis of blood density is required. The density of claret is generally estimated to be 1 gram per milliliter [2, 7–9]. However, at that place is a paucity of documentation that the ane milliliter of blood weighs one gram relationship is authentic or if it holds true for varying hematocrits. Existing information are conflicting and demonstrate blood density ranges between 1043 and 1060 kg/giii (1.043–i.060 chiliad/mL) [10]. The current study aims to determine the density of blood in an animate being model and correlate information technology with the hematocrit. This volition test the assumption that the specific gravity of claret is equal to water. If the relationship is valid and does non vary with hematocrit, it confirms the accuracy of weighing surgical sponges to determine intraoperative blood loss.
2. Materials and Methods
Rat blood used for this written report was sampled from claret drawn every bit function of a protocol approved past the Brute Care Commission and Biologic Resource Laboratory at the University of Illinois at Chicago and the Institutional Animal Intendance and Utilization Committee of the Jesse Brown VA Medical Center (Chicago, Illinois). Male Sprague-Dawley rats, existence utilized for another experiment and weighing between 385 and 435 grams, were sedated using atmospheric room air and two% isoflurane. The rats were then placed on a heated surgical stage under a lightless estrus lamp. The trachea was intubated and the rat ventilated with 1.7% isoflurane in oxygen. Cannulas were placed in both common carotid arteries and the left internal jugular vein. Heparinized microhematocrit tubes were filled with arterial whole blood from the cannulated left common carotid artery. The tubes were sealed at 1 end using two layers of white dirt and centrifuged (International Equipment Visitor, Chattanooga, TN, Micro-Capillary Centrifuge, Model MB) at 10,000 revolutions per infinitesimal for 5 minutes. The hematocrit was read from the packed prison cell volume using a microcapillary reader (Damon/IEC Partition Micro-Capillary Reader).
A few drops (<0.2 mL) of arterial whole blood obtained from the carotid artery were placed on a plastic weigh dish. A 50µL aliquot of this sample was collected using a disposable plastic micropipette (Fisher Scientific Fisherbrand, Loughborough, Leicestershire, U.k., Finnpipette). This sample was placed on an electronic balance (Ohaus Corporation, Parsippany, NJ, Voyager) which had been previously zeroed, and the mass determined. Eighteen samples were collected and documented in this mode. Eighteen control trials using deionized water were too performed on the same electronic calibration utilizing the identical technique equally the claret samples. All measurements were determined at room temperature.
Statistical methods included a linear regression to provide a model for testing the correlation betwixt blood density and hematocrit. Additionally, a Student'due south unpaired, i-tailed t-test with a Welch'south correction was used to compare the means of the blood and distilled water masses. Information are reported as the mean ± SD.
three. Results and Discussion
The masses of the 18 blood aliquots are recorded in Table 1. The average mass of the 50-microliter blood samples was 0.0489 ± 0.032 g with a range of 0.0445 thousand to 0.0512 g. Tabular array 2 lists the masses of the xviii distilled water controls. The boilerplate mass of the 50-microliter water samples was 0.0492 m with a range from 0.0487 one thousand to 0.0496 g. The average density of the blood samples was normalized to the average mass of the distilled water controls by dividing the two means to yield specific gravity and an adapted mean blood density of 0.994 ± 0.032 g/mL. The average hematocrit of the blood samples was 40.3% (range 24%–48%). Effigy 1 shows the mass of the fiftyµL samples of blood as a part of hematocrit. The R 2 value was 0.1767. Therefore, in that location was poor correlation between the hematocrits and the density of the blood samples. Populations were deemed fit for parametric testing but their variances were unequal by ANOVA (P < 0.00001). To business relationship for this a Student's t-test with a Welch'due south correction was utilized to compare the blood and distilled water samples. The results yielded a P = 0.2269 and R 2 = 0.03154. This assay verifies the fact that the mass of the blood and water samples was not significantly different.
Graph correlating rat blood mass to blood hematocrit.
Table ane
Masses of the 18 rat blood samples.
| 50μL samples of claret | ||
|---|---|---|
| Number | Hematocrit | Mass (k) |
| one | 45.0 | 0.0496 |
| 2 | 31.0 | 0.0479 |
| 3 | 44.5 | 0.0512 |
| 4 | 37.0 | 0.0506 |
| 5 | 48.0 | 0.0502 |
| half-dozen | 38.5 | 0.0499 |
| 7 | 46.5 | 0.0509 |
| 8 | 39.0 | 0.0497 |
| 9 | 47.0 | 0.0492 |
| x | 45.0 | 0.0478 |
| xi | 42.5 | 0.0493 |
| 12 | 32.0 | 0.0474 |
| 13 | 46.0 | 0.0475 |
| xiv | 39.0 | 0.0445 |
| xv | 45.0 | 0.0495 |
| xvi | 31.0 | 0.0480 |
| 17 | 24.0 | 0.0475 |
| 18 | 44.0 | 0.0495 |
| | ||
| Average | twoscore.3 | 0.0489 |
| Max | 48.0 | 0.0512 |
| Min | 24.0 | 0.0445 |
| Range | 24.0 | 0.0067 |
| SD | 6.nine | 0.0016 |
Table two
Masses of the eighteen deionized water controls.
| 50μL deionized water controls | |
|---|---|
| Control number | Mass (1000) |
| 1 | 0.0495 |
| 2 | 0.0495 |
| 3 | 0.0494 |
| 4 | 0.0496 |
| 5 | 0.0496 |
| 6 | 0.0487 |
| 7 | 0.0494 |
| 8 | 0.0495 |
| 9 | 0.0490 |
| ten | 0.0489 |
| 11 | 0.0491 |
| 12 | 0.0492 |
| 13 | 0.0489 |
| 14 | 0.0490 |
| 15 | 0.0492 |
| 16 | 0.0491 |
| 17 | 0.0493 |
| 18 | 0.0487 |
| | |
| Average | 0.0492 |
| Max | 0.0496 |
| Min | 0.0487 |
| Range | 0.0009 |
| SD | 0.0003 |
The surgeon or anesthesiologist routinely estimates the volume of blood lost during each operation. This estimate can guide transfusion requirements or assist in the amount of intravenous resuscitation required to maintain euvolemia. Authentic measurement of intraoperative claret loss also allows the comparing of dissimilar surgical techniques and methods to minimize blood loss during surgery. Inaccurate determination of intraoperative blood loss tin atomic number 82 to unnecessary transfusions. There is ample evidence to suggest that blood is immunosuppressive [11, 12] and has been associated with worse outcomes in colorectal cancer [13]. Blood transfusion likewise increases the risk of surgical site infections [xiv] and is expensive.
There are many methods to make up one's mind the volume of intraoperative blood loss. The virtually precise method utilizes spectrophotometry [15–17]. This method prepares a referenced standard of the patient's own blood. Blood lost into drapes, gowns, and sponges is extracted and filtered. The resulting sample is so read in a spectrophotometer along with the patient'due south reference standard. This method is considered highly reliable; however, it is expensive, labor intensive, and clinically impractical.
During a typical operation, shed claret is aspirated via a suction organisation directly into canisters where the claret book can be accurately measured. Blood lost into sponges and laparotomy pads is also visually estimated by the attending surgeon or anesthesiologist—a routine but subjective and highly inaccurate method [1–5]. The gravimetric method of determining blood loss requires weighing surgical sponges before and after use. The difference in weight is assumed to be the volume of blood lost as measured in milliliters. This assessment is based upon density which is defined as mass per unit book. Water density is dependent upon temperature. At room temperature of 23°Centigrade, water has a density of 0.997538 chiliad/mL [12]. This translates into the common metric equivalent that ane gram of water is equal to 1 milliliter. The P value of 0.2269 for this study demonstrates that the two populations are non statistically significantly different. The R 2 for the two populations was 0.03154. This low value demonstrates that the means of the water and the blood samples are statistically similar. The human relationship of the mass of blood and the hematocrit has not been clearly established [13, fourteen]. Our study confirmed that at that place was poor correlation between the mass of blood and hematocrits varying between 24 and 48 percent (Figure i).
The purpose of this study was to validate the commonly held supposition that the density of claret is one gram per milliliter. We found the average density of blood was 0.994 thou/mL ± 0.032 g. Notably, changes in the hematocrit did not bear on the density of the claret samples and assay revealed no human relationship between the two parameters. These data support the belief that the density of blood and water is very close and therefore the human activity of weighing gauze sponges before and afterward utilise in the operating room is a reliable guide to make up one's mind the volume of blood lost into the gauze.
There were some limitations to this study. A fiftyµL sample of water should have a mass of 0.05 grams although none of the samples were recorded with this value and probably reflects the fault of pipetting and weighing. Aliquots were recorded immediately after dispensing. This minimized whatever errors due to evaporation. It was also noted that the blood samples adhered to the inside of the micropipette tip, possibly causing the dispensed volume to be less than actually measured. The quantity of blood or water retained on the within of pipettes after dispensing the fluid was unknown and non measured, only presumably constant. Additional considerations included the fact that the density of water is a function of temperature, nearing a peak value of 999.9720 kg/m3 at 4°C [18]. At a temperature of 23°C, h2o has a density of 0.997538 m/mL [14] which offers a potential caption for the control grouping's difference from an expected density of 1 gm/mL. More sophisticated methods to determine mass could be used to reproduce and validate the results. A greater sample size may assistance to confirm the accuracy of the findings and repeating the written report beyond a greater range of hematocrits would provide additional useful information. Finally, a direct comparing of rat and homo blood densities is lacking in the literature. Based upon comparisons of other mammalian species, [19, 20] however, it is suggested that the comparative densities between homo and rat blood are probably valid.
4. Conclusion
The measured mass of blood is nearly equal to distilled water. This confirms the assumption that the densities of blood and of distilled water are about equivalent. This helps verify the employ of the gravimetric method of weighing sponges in the operating room to accurately make up one's mind blood loss and a one-gram increase in the weight of a blood soaked surgical gauze is equal to 1 milliliter of claret lost.
Conflict of Interests
The authors declare that there is no conflict of interests regarding the publication of this paper.
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