All clinical treatments and procedures are, somehow, associated with side effects of lesser or higher significance. The certain value of blood testing for both monitoring and diagnosis of disease is tempered by recognizing that constant blood testing causes blood loss of a specific level and can increase anemia levels which force patients to undergo red blood cell transfusion.
Fig: Unnecessary Blood Tests May Increase Anemia Levels
We also know this as either nosocomial anemia or iatrogenic anemia, we are going to discuss this side effect of lab testing in this post. Because of blood testing among the patients in hospitals, considerations are given to some of the pathological factors to determine if there is a clinical effect of that blood loss. We will discuss the strategies to reduce blood loss because of lab testing.
There is an incident of a 68-year-old woman who was hospitalized because she was diagnosed with community-acquired pneumonia. After receiving antibiotics, her condition started to improve within 2 days. During her admission, her blood was drawn every day.
She complained fatigue on day 3 in the hospital. Her hematocrit and hemoglobin levels fell down on lab results on day 4. To ensure the validity of this result, her blood is drawn once again to conduct the test again. Her hemoglobin level dropped to the whopping level of 7.0 g/dL, i.e. 2g/dL lower than the day she got admitted and she ended up getting a transfusion.
She finally got her hemoglobin level stable on day 7, i.e. 8.5g/dL and she got discharged. On the morning when she was about to discharge, a nurse came to collect her blood samples. In the end, she asked, “Are all such blood tests important?”
This is a very common case. Especially in providing critical care, a huge amount of blood is drawn. Due to this clinical uncertainty, physicians order more lab tests than actually, they need. However, these tests require more testing and checkups without having any major benefit to the patient. When blood test requires more testing, the hematocrit and hemoglobin levels fall in the patient. Ultimately, it causes the increment in anemia levels.
The physicians draw higher volumes of blood than the actual requirement by most testing guidelines. For each set of test, around 50 to 60 ml of blood is drawn. It is depending on the size of tubes, a possibility that test may need to conduct again. Hence, the multiple reagents may require for each test. Actually, around 3ml of blood is enough to perform most lab tests, even though tests have to be conducted again.
Physicians working in CCU of a hospital based in New York were perplexed in the early 1970s by the frequency of mild anemia symptoms in patients when they got admitted in the hospital. According to them, this unexplained anemic reaction might be the cause of blood testing and test for the hypothesis. The study included the first attempt to assess blood loss because of blood testing. It is revealing the average loss of blood of 54 ± 17 mL on daily basis among their population of 93 patients in CCU.
According to Kruksall and Smoller, there was significant blood loss because of lab testing. In the mid of 1980s among the patients who were critically ill were compared to other admitted patients. They quantified blood collected from 100 patients retrospectively. While being admitted to a Boston-based hospital and discovered blood was sampled around 1.1 times per day. It is an average from ward patients but 3.4 times per day from patients admitted in intensive care units. The average blood loss was reported 12.4 mL on a day-to-day basis for the ward patients in comparison to 41.5 mL for patients in intensive care.
Ward patients are losing around 175 mL during their hospital stay due to blood testing. The average loss is 762 mL in total for intensive care patients. Total loss of blood exceeded 1000 mL for 10 of 50 patients (i.e. around 20%). A potential blood sampling study of 1136 patients in 145 ICU units found that mean SD total volume of samples taken each day was 4.6 (3.2) and mean SD number of blood sampled was 41.1 mL per day.
The rest of all intensive care patients of 5% are losing of over 200mL and 0.7% suffering losses of around 600 mL during their intensive care stay. Blood gas analysis is the most widely demanded blood test among intensive care patients. Also, it's counting is around 40% of blood loss because of lab testing. According to a UK study, intensive care patients are going through blood gas testing 8 times per day. The test accounting is an average loss of 45 mL of blood. So, it is clear that unnecessary blood tests may cause higher anemia levels.
To discuss the blood losses in context, we need to consider the total blood volume, i.e. 70 mL/kg of body weight. Hence, an adult (weighing around 70 kg) has lost around 5 liters of blood in total. Blood cells also have a small lifespan, i.e. red blood cells last 120 days. Hence, there is the constant production of bone marrow with up to 1% of blood volume to be replaced every day.
For the huge population of patients in hospitals, blood loss is relevant to lab testing. It can represent only 0.1% to 0.2% of total volume and it is not sufficient for clinical impact. For patients who are critically ill, it is generally not the case, as they need a more detailed checkup. We can do the blood testing around 24 times per day for those patients. According to the above study, blood loss may go up to 100 mL/day, which is similar to a 2% loss of blood volume.
The type and severity of illness and length of stay in ICU, have an impact on blood loss because of lab testing for specific patients. For all, there is a risk of iron deficiency and constant low supply of oxygen to tissues.
Every 1 mL of blood consists of 0.5 mg iron. Hence, a collection of 50 mL blood causes loss of around 25mg of iron. Even a normal diet has 10 to 15 mg of iron per day. Hence, 10% to 30% of it is absorbed, even when 4.5 mg/day recover from a diet with maximum absorption. The overall phlebotomy of only 15 mL of blood causes a negative balance of iron within a few days. The body has significant iron reserves stored and anemia won’t develop until such losses are exhausted.
However, it is seen that iron stores can deplete severely by phlebotomy on daily basis for a long period. People with lower iron may store on admission to ICU are at a higher level than normal risk of signs of anemia related to phlebotomy.
Anemia is diagnosed when the amount of hemoglobin falls under 135 g/L in males and below 115 g/L in females.
The specific vulnerability of patients in intensive care for severe anemia levels is due not only to the loss of blood. It is from phlebotomy and also due to the common critical condition which forced admission of patients, apart from the complication associated with critical illness.
With all these, it is clear that anemia is the main aspect of critical illness. It can develop in 90% of patients by the third day after the admission to intensive care. For over a half of those patients, anemia is causing due to ample severity to warrant transfusion of red cells.
According to Von Ahsen et al, blood sampling counted for around 17% of blood loss among 96 patients who are in intensive care. On the other side, Corwin et suggested over 50% of changes in red cells transfusion to intensive care patients which may be accounted for due to blood sampling.
Among several changes which take place during the first few weeks of birth, as babies transform from uterine growth to physiological independence, there is a gradual decline in the amount of hemoglobin from 17 g/dL at birth to 11g/dL by 8 weeks of birth.
The significantly normal reduction of hemoglobin is very severe and constant in premature children. Also, it causes anemia in prematurity, in which hemoglobin declines to around 7mg/dL. Among premature babies. This predisposition to anemia can exacerbate by the loss of blood.
The effect of loss of blood because of lab test is higher for most infants, with the most premature neonates with around 1500g of birth weight who all need several weeks of intensive care and monitoring.
There is a significant need for blood testing among the patients, but there is a small circulation of blood volume. There is a higher volume of blood per kg of body weight for neonates than for adults. But assuming 80-90 mL/kg of blood volume too small and frail infants have blood volume which may be lower as 50 mL. Hence, sampling only 1 mL of blood lowers blood volume by 2 percent.
The daily loss of 4% to 5% of blood volume in phlebotomy during the weeks is observing just after delivery, which is not uncommon in the group. According to formal studies, there is a weekly loss because of phlebotomy of 10 to 25 mL/kg among neonates with weight below 1500g. It shows loss of the total volume of blood of 10 to 30 percent, which may play a vital role in the severity of anemia.
Iatrogenic anemia is considered as a changeable risk factor for red cell transfusion. Reducing exposure to the transfusion risk in the patient is clinically important and it needs strategies to reduce the blood loss in critical care. A lot of approaches are useful and demonstrate that phlebotomists, nurses, lab staff, clinicians, and manufacturers of lab equipment play a vital role.
There is evidence which shows that lab testing is excessive in intensive care unit. Tests may be asked as part of routine instead of a requirement. The way written guidelines are adopting for lab testing, they can play a vital role in lowering a number of tests and ensuring those tests are appropriate. Just providing the cost of testing to the physicians can help lower requirements of unnecessary testing. The proper monitoring of the volume of a blood sample from each patient can modify the requirement of the test.
Obviously, it is vital to ensure that no more blood is drawn than it is actually needed for the analytical process. Marquis et al have highlighted the extent of oversampling who studied the practice of blood sampling in intensive care over the period of 10 weeks. They found that the volume of sampled blood was around 4 to 20 times higher than the original volume of blood used for analysis.
At the same time, an audit of blood sampling revealed that labs collect 2.76 mL at 140 hospitals in the US. It is 8.5 times more than the actual requirement for a full blood count. This is an average of 1.75 for electrolyte profile, which is 12 times more than the actual requirement. Hence, a lot of labs can reduce collection volumes without losing the ability to report a timely and reliable result.
To deal with this issue of oversampling in the intensive care unit for adults, a simple partial solution is used i.e. pediatric tubes of blood collection. According to Smoller et al, 47% reduction of blood loss in an iatrogenic test was reported from regular tubes of blood collection to pediatric tubes.
The blood sample is collected frequently via an indwelling catheter in critical care. Most of these are often used in radial artery of adults as well as an umbilical artery of infants. A saline flush or heparin solution can maintain the patency of such catheters. For accurate results, it is important that blood is not contaminated with flush liquid and a volume of blood should be discarded to this end, i.e. to a clear line of all flush traces, before sampling of blood.
A minimum volume of 2 mL is the recommendation but actual volume may rely on local practice. A lot of devices are available to return it safely to the patient and conserve the discarded blood after collecting the uncontaminated sample.
Even with growing significance, the point of care testing is having a significant potential of all types of strategies which are described to lower iatrogenic anemia among the patients who are critically ill. Around all of the blood tests are taken to monitor patients who are critically ill.
Blood gas analysis has been taken for around two decades in the intensive care settings at the point of care. These days, blood gas analyzers are able to measure blood gas parameters and even have a large number of hematological and chemical parameters which have hitherto as only preserve in the lab setting.
In addition, all of those measurements are making with a small blood sample of 100 to 150 µL. In a critical setting, the main advantage of POCT is, it can reduce the turnaround time. However, the secondary benefit is lower blood loss to conduct diagnostic testing. The helpful effect of point of care testing is shown in a recent study.
To prevent the symptoms of anemia in adults because of unnecessary laboratory testing, Lab Me is the best solution. It works on machine intelligence which can detect all your blood ranges and can interpret accurately. It can also prevent the need for frequent blood testing. The software can give accurate and precise results in the first attempt, without having to go for lab tests too frequently.
To avoid exposure of sick patients to further risks related to blood transfusion, clinical certainty is very important and this tool does just that. It can interpret lab reports in a very clear way and its interface is very easy to use. It is helping both patients and physicians to figure out the right solutions.
Ref
https://acutecaretesting.org/en/articles/iatrogenic-anemia--a-downside-of-blood-testing
https://www.sciencedaily.com/releases/2011/08/110808161141.htm
