PLATELETS REVISISTED

 

1. The normal platelet count in adults ranges from 150,000 to 450,000/microL.
2. The mean value in males is 237,000/microL.
3. The mean value in females is 266,000/microL.
4. Thrombocytopenia or low platelet count is defined as a platelet count less than 150,000/microL.
5. About 2.5 percent of the normal population has platelet count lower than 150,000 /microl (as a normal variant).
6. A recent fall in the platelet count by one–half is abnormal even though it may still be in the normal range.
7. Thrombocytopenia is not usually detected clinically until the platelet count has fallen to levels below 100,000/microL.
8. Variation of the platelet count in a given individual is limited. Differences in the absolute platelet count greater than 70 to 90,000/microL will occur by chance less than one percent of the time.
9. Surgical bleeding due solely to a reduction in the number of platelets does not generally occur until the platelet count is less than 50,000/microL, and clinical or spontaneous bleeding does not occur until the platelet count is less than 10,000 to 20,000/microL.
10. Platelets survive in the circulation for 8 to 10 days, after which they are removed from the circulation by cells of the monocyte–macrophage system, as a result of programmed apoptosis.
11. The youngest platelets in the circulation are larger and more hemostatically active. Thrombocytopenic patients, who do not have serious bleeding, suggest that the small numbers of young platelets in these patients are more hemostatically active than mixed age platelets in normal subjects.
12. In dengue no transfusion is needed unless the count is lower than 2% of the baseline levels.
13. Platelet count can be falsely low in a number of clinical situations:
    • If anticoagulation of the blood sample is inadequate, the resulting thrombin–induced platelet clumps can be counted as white cells by automated cell counters. The WBC count is rarely increased by more than 10 percent.
    • Approximately 0.1 percent of normal subjects have EDTA–dependent agglutinins which can lead to platelet clumping and spurious thrombocytopenia and spurious leukocytosis.
    • Pseudothrombocytopenia can also occur after the administration of the abciximab.
    • EDTA–induced platelet clumping can be diagnosed by examination of the peripheral smear. One should do a repeat count in a non–EDTA anticoagulant.
    • If platelet clumping is observed, the platelet count is repeated using heparin or sodium citrate as an anticoagulant. If citrate is used, one should remember to correct the platelet count for dilution caused by the amount of citrate solution used; no such correction is needed for heparin. Alternatively, one can use freshly–shed non–anticoagulated blood pipetted directly into platelet counting diluent fluid.
    • Patients with cirrhosis, portal hypertension, and spleen enlargement may have significant degrees of "apparent" thrombocytopenia (with or without low white cells and anemia), but rarely have clinical bleeding, since their total available platelet mass is usually normal.

BOMB BLAST INJURIES

Blast injuries can be of four types.
 

1.Primary blast injuries are the injuries to the hollow gas-filled organs like the lungs, ear drum or intestines leading to their rupture. These occur as a direct result of the impact of the over pressurized blast wave on the body. 

2. Secondary blast injuries occur due to flying debris and bomb fragments leading to penetration or penetrating injuries such as to the eyes.

3. Tertiary blast injuries occur when individuals are thrown by the blast wind leading to fractures as a result of the fall.

4. Quaternary blast injuries are due to direct effect of burn or crush injuries. 

The most important triage to manage blast injuries is not to waste energies and resources on patients with non-serious injuries.  The first thing is to check for eardrum rupture and signs of respiratory imbalance. Their absence indicates a non-serious injury. 

All patients exposed to a blast must have eardrum examination as the first step. If the ear drums are intact, the patient can be discharged with first-aid treatment. If ear drum is ruptured, an X-ray chest should be done immediately. All such patients should be observed for eight hours as primary blast injuries are notorious for delayed presentation. 

Doctors should therefore focus only on two exams: otoscopic ear exam and pulse oximetry. Blast lung injury is unlikely without tympanic or ear membrane rupture. This is used as a screening procedure for admitting a patient. Decreased oxygen saturation on pulse oximetry signals early blast lung injury, even before symptoms become apparent. 

Half of all initial casualties seek medical care over first hour. Double this number after one hour and you will know the total casualties. This formula is often used by the media to predict the tolls. It is also useful to predict demand for care and resource needs. 

Always expect upside down triage as the most severely injured arrive after the less injured who self-transport to the closest hospitals. 

With the increasing use of explosives in terrorist events in our country in recent times, doctors, especially Emergency Doctors, should undergo orientation training every six months so that they are prepared and better equipped to manage several casualties all at one time.