Send the link below via email or IMCopy
Present to your audienceStart remote presentation
- Invited audience members will follow you as you navigate and present
- People invited to a presentation do not need a Prezi account
- This link expires 10 minutes after you close the presentation
- A maximum of 30 users can follow your presentation
- Learn more about this feature in our knowledge base article
Do you really want to delete this prezi?
Neither you, nor the coeditors you shared it with will be able to recover it again.
Make your likes visible on Facebook?
Connect your Facebook account to Prezi and let your likes appear on your timeline.
You can change this under Settings & Account at any time.
Transcript of Bleeding Disorders
If still bleeding after surgery, carefully examine the site
Inspect for bleeding arteries
Ligation of artery
Pack hemostatic agent (Gelfoam, Surgicel) at the bottom of socket and sew with sutures
Place extra sutures - if applicable to reduce bleeding
Refer Alex to oral and maxillofacial surgeon (20)
Avoid strenuous activity for a week
Drink lots of water; avoid carbonated drinks and alcohol
Don't drink from straw; sucking action dislodges blood clot from socket
Pain management medications
Avoid excessive spitting
Replace gauze over extracted site
Do not brush 24 hrs post surgery
Rinse with warm water and salt
Smoking will increase risk of complications (21)
If you had to do dental surgery again for Alex, how would this be managed?
Managing Extraction to Prevent Hemorrhage
Risk for hemorrhage is .2-1.4%
Preoperative assessment of intrinsic coagulation disorders and the use of anticoagulant (Warfarin) and antiplatelet medications (ASA, Coumadin, Plavix) are essential
Desmopressin acetate, a nasal spray, is the treatment of choice for mild von Willebrand disease
Most important predisposing risk factor reported is the level of the impaction and its proximity to the neurovascular bundle (19, 21, 22)
Family bleeding abnormalities
General Classifications of Bleeding Disorders
Vessel Wall Disorders
Patient is on antiplatelet therapy.
Medical history significant for coronary artery disease, hypertension and had a stent placed.
extraction of #31
Given the prevalence of bleeding disorders in society, what is your top differential diagnosis?
Why would the ER physician order a blood transfusion for Alex? What are the risks of blood transfusion?
Case 1: Bleeding Disorders
Obtain a comprehensive patient assessment, including personal, medical, dental and pharmacological history.
Include questions about unusual bleeding and any supplements/herbs, previous dental procedures. Does the patient live alone? What are their preferences for treatment?
Conduct thorough radiographic, extraoral and intraoral examinations.
can identify irregularities that may result from bleeding disorders.
spontaneous gingival bleeding
hemorrhages into soft tissues (3).
: Juan is a 56 year old Hispanic male who presents with slight pain and swelling in the lower right molar area. He states the problem began several months ago, and has been symptomatic off and on since that time.
: His medical history is significant for hypertension, coronary artery disease with a stent placed in March 2011. Current medications include clopidogrel 75mg/day and aspirin. When asked about his aspirin therapy, Juan states that he has taken a “baby” aspirin once/day for the last 20 years but recently “doubled it” after seeing a recent Dr. Oz feature on television.
: His clinical and radiographic exam reveals multiple carious teeth, generalized recession and inflammation of the gingiva, horizontal bone loss consistent with generalized moderate periodontitis, and non restorable #31 due to caries that is in need of extraction.
This disorder can lead to hemorrhaging
Individuals with Scurvy suffer from this disorder- Vitamin C deficiency
Lack of Vitamin C reduces production of Hydroxyproline
Leads to abnormalities in collagen synthesis
In individuals with Scurvy, hemorrhages are often found in the muscles, joints, nail beds, and gingival tissues
Petechial hemorrhages are often found at the hair follicles
Petechial hemorrhages are a broad category of purpuric skin conditions. It refers to the smallest of the vessel eruptions (<3mm) 
Individuals with Cushing's syndrome are affected due to high levels of corticosteroids 
The high levels result in the wasting away of proteins as well as the atrophy of connective tissue around blood vessels
Irregularly shaped purpuric areas 
Ehler's Danlos Syndrome is another type of vessel wall disorder 
Syndrome results from defective connective tissue matrix. Syndrome is characterized by fragile blood vessels and individuals tend to bruise easily. Skin is hyperelastic with hypermobile joints.
Multiple types 
What type of physician treats patients with bleeding problems?
Hematologist- a physician that specializes in the diagnosis, treatment, prevention, and/or investigation of disorders of the interaction between blood and blood vessel wall.
A hematologist uses the following in order to investigate, diagnose and manage disorders:
Specialized clinical laboratory tests
Evaluation of tissue or cytological specimens
Clinical entities, which are specific to the specialty of hematology, include disorders of the structure, function, and physiology of red and white blood cells and platelets, disorders of hemostatic system regulation or function, and benign and malignant disorders of the bone marrow and lymphoreticular system. (12)
-von Willebrand disease (VWD)
-problem with von Willebrand factor (protein that helps blood clot)
-normally binds factor VIII
-protein is either not present or not functional (1)
-3 major types of VWD (1)
Discuss the different inheritance patterns of von Willebrand disease and explain spontaneous mutations
What is the best way to identify bleeding diatheses?
Least invasive way to identify bleeding diathesis: Medical history
A dialogue between the doctor and the patient is very important for the consideration of bleeding diatheses. It is vital to carefully assess the presenting complaint in order to determine whether the defect is inherited or acquired, in order to proceed to a rational laboratory investigation (14).
How Does Hemostasis Occur in a Normal, Healthy Patient?
People who have type 1 VWD have low levels of von Willebrand factor and may have low levels of factor VIII. Type 1 is the mildest and most common form of VWD. About 3 out of 4 people who have VWD have type 1.
3 Mechanisms involved in normal hemostasis include vasoconstriction, platelet plug formation and clotting of the blood. (9)
In type 2 VWD, the von Willebrand factor doesn't work well. Type 2 is divided into subtypes: 2A, 2B, 2M, and 2N. Different gene mutations (changes) cause each type, and each is treated differently. Thus, it's important to know the exact type of VWD that you have. Present in about 25% of those with VWD.
von Willebrand disease is a genetic disorder that is passed from parent to child
People who have type 3 VWD usually have no von Willebrand factor and low levels of factor VIII. Type 3 is the most serious form of VWD, but it's very rare. Only present in about every 1 in 1,000,000 cases
Type 1 and most cases of Type 2 von Willebrand disease are inherited in an autosomal dominant pattern
Type 3 and rare cases of Type 2 von Willebrand disease are inherited in an autosomal recessive pattern (7,8)
: Alex is a 19 yr old Asian male who attends a west coast university studying engineering. He lives in a fraternity house about 25 miles from his home.
He has had several months of pain and swelling associated with his lower wisdom teeth.
: Alex states that he is otherwise healthy,
takes no medications and has never been seriously ill, nor has he had any past surgery.
He does not really know his family history well as his grandparents and other relatives reside in China. Both his parents and sisters are healthy as far as he knows.
You examine Alex and find that he indeed has lower wisdom teeth that are infected
. By radiographs, he also has
2 upper wisdom teeth that are impacted.
You plan on removing his 4 wisdom teeth with local anesthesia in your office.
The oral surgery goes well. You notice that his sockets are bleeding a little even 30 minutes after tooth removal.
However, with time, the bleeding seems to be stopped and you discharge Alex.
Alex does not show up for his post-op visit at 4 days after surgery and the office made several attempts over the next few days to reach him. Ten days later, your office gets a call from Alex's sister who states
Alex has been bleeding since he had his surgery
. The sister brings Alex from his fraternity to your office and you notice
he looks pale, is lethargic and has clotted blood in his mouth.
You send Alex to the local hospital given his condition. The Emergency Physician orders a
for Alex. The ER physician also orders a consult with another physician. After 2 days in the hospital Alex returns home to his parent's house.
This slows the flow of blood to damaged blood vessels to minimize blood loss in the area.
- Thromboxane, and other vasoconstrictors, released at site causes vasoconstriction in the immediate area.
- Epinephrine released by adrenal glands as a result of the injury stimulates general vasoconstriction throughout the body to minimize blood loss and protect vital organs. (9)
1: Main, Editor M. "What Is Von Willebrand Disease?" - NHLBI, NIH. National Heart, Lung, and Blood Institute, 1 June 2011. Web. 13 Nov. 2013.
3: Sandra D' Amato,
Dental Management of patients with Bleeding Disorders
, Crest® Oral-B® at dentalcare.com Continuing Education Course, Revised January 17, 2012, http://www.dentalcare.com/media/en-us/education/ce319/ce319.pdf
4: Brewer, Andrew,
Guidelines for Dental treatment of patients with Inherited Bleeding Disorders.
Treatment of Hemophilia. May 2006. No 40. http://www1.wfh.org/publication/files/pdf-1190.pdf
5: William L. McBee,
Review of Hemostatic Agents Used in Dentistry.
http://www.dentistrytoday.com/oral-medicine/oral-surgery/1538. Monday, 28 February 2005
6: Dhara Pandya,
"Liver clot"-A rare periodontal postsurgical complication.
2012 | Volume : 23 | Issue : 3 | Page : 419-422. http://www.ijdr.in/article.asp?issn=0970-9290;year=2012;volume=23;issue=3;spage=419;epage=422;aulast=Pandya
7. "Von Willebrand disease." Genetic Home Reference. U.S. National Library of Medicine, Feb 2008. Web. 24 Oct. 2012. <http://ghr.nlm.nih.gov/ condition/von-willebrand-disease>.
8. "Van Willebrand Disease." TeensHealth. The Nemours Foundation, May 2010. Web. 24 Oct. 2012. <http://kidshealth.org/teen/diseases_conditions/blood/ vwd.html#>.
9. Doohan, J. (1999, October 11). Hemostasis. Hemostasis. Retrieved November 10, 2013, from http://www.biosbcc.net/doohan/sample/htm/Hemostasis.htm
10. Shafer, D., Rush, S., Cleary, P., Coulter, V., Collins, F., White, R., et al. (n.d.). Hemostasis Basics - Programmed Learner. Hemostasis Basics - Programmed Learner. Retrieved November 10, 2013, from http://www.dadebehring.com/education/hemostasis/tutorial.htm
11. D'Amato-Palumbo, S. (2012, January 17). Dental Management of Patients with Bleeding Disorders. Dentalcare.com. Retrieved November 13, 2013, from http://www.dentalcare.com/media/en-us/education/ce319/ce319.pdf
1.American Society of Hematology (n.d.). Defining the American hematologist. Retrieved November 13, 2013, from http://www.hematology.org/About-ASH/1778.aspx
13National Heart, Lung and Blood Institute (n.d.). Diagnosis and evaluation, von Willebrand Disease (VWD) guidelines, NHLBI. Retrieved November 13, 2013, from http://www.nhlbi.nih.gov/guidelines/vwd/3_diagnosisandevaluation.htm#diagrec
14UpToDate (2013). Approach to the adult patient with a bleeding diathesis. Retrieved November 13, 2013, from http://www.uptodate.com/contents/approach-to-the-adult-patient-with-a-bleeding-diathesis
15. Glick, Michael, et al. Burket's Oral Medicine. 11th ed. Hamiliton, Ont: BC Decker, Inc, 2008. STAT!REF electronic medical library. Web. 13 Nov. 2013.
16. Harris, MD, Niel. "The International Normalized Ratio: How well do we understand this measurement?." <i>American Association for Clinical Chemistry</i>. N.p., n.d. Web. 13 Nov. 2013. <http://www.aacc.org/members/nacb/NACBBlog/lists/posts/post.aspx?ID=98#Find a website by URL or keyword...>.
17. "Blood Laboratory: Hemostasis: PT and PTT tests." <i>Blood Laboratory: Hemostasis: PT and PTT tests</i>. N.p., n.d. Web. 13 Nov. 2013. <http://www.medicine.mcgill.ca/physio/vlab/bloodlab/pt_ptt.htm>.
18. "Coagulation Disorders." Medical Information & Trusted Health Advice: Healthline. N.p., n.d. Web. 13 Nov. 2013. <http://www.healthline.com/galecontent/coagulation-disorders-1>.
19.H. Moghadam, M. Caminiti. Life-Threatening Hemorrgae after Extraction of Third Molars: Case Report Management Protocol. J. Canadian Dental Association 2002; 68 (11): 670-4http://cda-adc.ca/jcda/vol-68/issue-11/670.pdf
20.B. Le, I. Woo. Management of Complications of Dental Extractions. Continuing Education Course. http://www.ineedce.com/courses/1457/PDF/Managmnt_Comp_Xtraction.pdf
21.Mayo Clinic staff. Wisdom tooth extraction. http://www.mayoclinic.com/health/wisdom-tooth-extraction/MY01212/DSECTION=what-you-can-expect
22.S. Susrla, B. Blaeser. D. Maganick.Third molar surgery and associated complications. Oral Maxilofacial Surg Clin N Am 15 (2003) 177-186.
-Follow-up symptoms show Alex is probably anemic
-Bleeding for the past 10 days since surgery
-Clotted blood in his mouth
Platelet Plug Formation
When a blood vessel is damaged, the blood leaking from the vessel is exposed to collagen fibers in the basement membrane of the vessel. Platelets in the blood stick to collagen and are activated. Once activated, they secrete ADP and thromboxane causing aggregation of more platelets to the site. This accumulation leads to a plug which inhibits further leakage. (9)
Clotting of Blood
-Allergic reactions (antibodies that react with proteins in transfused blood)
-Febrile reaction (sudden fever from reaction with white blood cells)
-Viruses or infectious diseases
-In the past, non-compatible blood types (2)
Blood clotting is activated through a clotting cascade when tissue or vessels have been damaged. This can be accomplished through two pathways:
- Damage to tissue outside the blood vessel -->activates tissue thromboplastin -->catalyzes activation of factor X -->converts prothrombin to thrombin -->converts fibrinogen to fibrin monomers --> polymerized into fibers which form a loose meshwork which is stabilized by crosslinks created by factor XIII which traps RBC's and platelets leading to clot.
- Damage to the blood vessel wall leads to the activation of multiple clotting factors which lead to activation of factor X. The pathway proceeds in the same manner from this point.
Consultation and INR laboratory screening evaluation done within 24 hrs of surgical appointment,.
Patient should be in optimal oral health
Prior dental cleaning
Regular usage of chlorohexidine mounthrinse(4).
antifibrolytic agent (Tranexamic acid and epsilon aminocaproic acid) take day before surgery and continue usage for 7 days (3).
For mild to moderate bleeding disorders one or two extractions can be done in one appointment(4).
Have the patient rinse with chlorohexidine mouthwash for 2 minutes prior to local anesthetic.
Perform extraction as atraumatically as possible(3).
If experience heavy bleeding
Suture the socket if gingival margins do not oppose well
Usage of appropriate hemostatic measures(4.)
Contact supervising physician
Determine if procedure should be done in dental office or a dental hospital setting (3).
Have patient sit upright and bite on damp gauze swab for 10 min(3).
Monitor the patient's blood pressure
Give patient post operative instructions
For the next 24 hrs
No mouth rinsing, smoking, hard foods, strenuous activities
Continue prescribed medications
salt water rinse 4x/day for 7 days
Give patient your emergency contact info
Ensure patient is not bleeding before the patient leaves the office.
Keep a close eye on the patient; a couple hours for mild bleeding disorders and up to 48 hrs for more severe bleeding disorders(4).
Case 12: Bleeding Disorders
How does clopidogrel and aspirin affect Juan's hemostasis, and how is this measured?
Clopidogrel and aspirin are both blood thinners which are considered antiplatelet agents. Clopidogrel (Plavix) works by inhibiting an ADP chemoreceptor (P2Y12) on platelet cell membranes which prevents them from receiving the aggregation signal from other platelets at site of injury. Aspirin irreversibly inactivates cyclooxygenase (COX-1) which is used to create thromboxanes. Without these, platelets are unable to aggregate and form clots. (10)
There are several methods for measuring a person's ability and efficiency in forming a blood clot. The most common tests currently performed are the Prothrombin Time test, the INR and the Platelet Function Analyzer, which is new but is gaining popularity. The PT test uses monitoring of the extrinsic and common pathways to quantify a person's ability to form a clot. Lab tests for normal clotting time are between 11 - 15 seconds. The International Normalized Ratio test is used to monitor patients taking anti-coagulants. A normal profile is 1.0, with "low intensity" measured at 2.0 to 3.0 and the "high intensity" range from 2.5 to 3.5. These intensity levels are determined by the patients likelihood of abnormal clotting. The higher risk patients require anti-coagulation at a higher intensity. The PFA is a device that can evaluate platelets both quantitatively and qualitatively. During formation of a platelet plug, it will measure the platelet attachment, activation and aggregation. This method has not been fully utilized yet in lab studies, and they hope to find other useful ways to derive information from its reports. (11)
Platelet Count test
Ivy Bleeding time test
Activated Partial Thromboplastin Time
Like Congenital platelet disorders, it is categorized as either thrombocytopenic or thrombocytopathic 
More common type of platelet disorders
In the more common types of acquired platelet disorders petechia and purpura are often found in the neck, chest, and limbs
mucosal bleeding can be found in the mouth and genitourinary tract
ITP- Idiopathic or immune thrombocytopenia purpura 
More than 300 mutations in the VWF gene have been found to cause von Willebrand disease (7,8)
Prevalence is 1% of population, but presence of clinically significant cases is around 1 in 10,000
Type 1 - mutations that reduce the amount of VWF -->
Type 2 - mutations that disrupt the function of the VWF cause the 4 sub-types -->
These mutations usually change one of the amino acids used to make VWF, which can disrupt the factor's ability to bind to various cells and proteins needed to form a blood clot
Type 3 - mutations that result in abnormally short, non-functional VWF -->
Thrombocytopenic- number of platelets are reduced
decreased production in bone marrow
larger amount being sequestered in the spleen
accelerated rate of destruction 
Thrombocytopathic- occur as a result of decreased critical platelet function
Problem occurs in adhesion, aggregation, or granule release
Glanzmann’s thrombasthenia- Thrombocytopathic disorder in which the platelet is deficient in membrane glycoproteins. 
International Normalized Ratio (INR)
Laboratory testing method to monitor patients on anticoagulation drugs (warfarin therapy)
Normal coagulation profile
INR value 1.0
Low intensity INR Profile
2.0 - 3.0
Consult with the physician
Can proceed with simple surgical procedures
Consult with patient physician to lower to 2.2-2.5 for complex surgical procedures
possibility of transiently interrupting anticoagulation therapy(3).
High Intensity INR
2.5 - 3.5
Consult with physician
Maintain INR in 2.5 - 3.5 for simple surgical procedures
Control bleeding via hemostatic measures
Lower to 2.5-3.0 for complex surgical procedures
Possibility for transiently interrupting anticoagulation therapy
Consider Heparin as substitute anticoagulant(3).
Patient's predisposition to abnormal clotting determines the intensity of the anticoagulation therapy(3).
Summary of Case 2
Patients with bleeding disorders need to seek care from a hematologist who will help them manage their situation
A thorough medical history will help identify any predisposition to bleeding
Three types of von Willebrand disease with Type 1 being the most prevalent
As the doctor, we need to be aware of the symptoms of anemia (heavy bleeding, pale, lethargic) and the potential risks for a patient who receives a blood transfusion
Proper pre-op assessment, administration of desmopressin acetate and hemostatic agent, and post-op at home care can reduce the potential of hemorrhage for Alex in the future
von Willebrand disease is a genetic disorder that can be either autosomal dominant or autosomal recessive
Evaluation of Patient Presenting Concerns About Bleeding/ Evaluation Prior to Procedures That May Increase the Risk of Bleeding
We should focus on a
of excessive bleeding throughout the person’s life and any family history of a bleeding disorder. (13)
The history of bleeding should identify:
Spontaneity and severity of bleeding
Sites of bleeding
Duration of bleeding
Type of injury associated with bleeding
Ease with which bleeding can be stopped
Any medications taken at the onset of bleeding (13)
Furthermore, when an invasive procedure is anticipated, the doctor should ask the patient whether he is taking any current medications, such as aspirin, or has history of liver or kidney disease, blood or bone marrow disease, and or high or low platelet count. (13)
If the patient says yes to the previous questions, proceed to ask:
1. Do you have a blood relative who has a bleeding disorder, such as von Willebrand disease or hemophilia?
2. Have you ever had prolonged bleeding from trivial wounds, lasting more than 15 minutes or recurring spontaneously during the 7 days after the wound?
3. Have you ever had heavy, prolonged, or recurrent bleeding after surgical procedures?
4. Have you ever had bruising, with minimal or no apparent trauma, especially if you could feel a lump under the bruise?
5. Have you ever had a spontaneous nosebleed that required more than 10 minutes to stop or needed medical attention?
6. Have you ever had heavy, prolonged, or recurrent bleeding after dental extractions that required medical attention?
7. Have you ever had blood in your stool, unexplained by a specific anatomic lesion (such as an ulcer in the stomach, or a polyp in the colon), that required medical attention?
8. Have you ever had anemia requiring treatment or received blood transfusion?
For women, have you ever had heavy menses, characterized by the presence of clots greater than an inch in diameter and/or changing a pad or tampon more than hourly, or resulting in anemia or low iron level? (13)
Responses to these questions can determine the need of specialized laboratory tests.
Coagulation disorders involved the body's inability to control blood clotting
Clotting is a very complex process involving different components of the blood.
The fluid component of the blood, plasma, contains coagulation factors and proteins that regulate bleeding. 
The blood contains colorless fragments known as platelets. Platelets will initiate contraction of the damaged blood vessels to reduce the amount of blood loss.
Platelets plug the damaged blood vessels. In combination with plasma, platelets accelerate blood clotting. 
Von Willebrand's disease- heritable disorder characterized by a defect in the factor VIII protein complex. 
Hemophilia- most often an inherited disease
Hemophilia A- missing or low levels of clotting factor VIII
Hemophilia B- missing or low levels of clotting factor IX
Hemophilia A in approximately 80% of individuals with Hemophilia 
The 3 mechanisms by which Hemostasis occurs
narrowing of vessels, this slows the speed of blood flow and releases local and systemic controls to areas of the body , promoting vasoconstriction.
2. Platelet Plug Formation:
Platelets adhere to collagen fibers in the damaged vessel leading to activation, secretion of ADP and thromboxane to form a plug which stops blood leakage.
Clotting cascade activates blood clotting through extrinsic and intrinsic pathways.
Juan is currently taking Clopidogel and Asprin which may alter Hemostasis
nhibits platelet binding preventing clot formation via an ADP chemoreceptor
inhibits platelet aggregation via inactivation of COX-1, used to make thromboxanes.
Both are considered antiplatelet agents and are blood thinners
Hemostasis can be measured via several methods:
Prothrombin time test, INR platelet function analyzer, platelet count test, Ivy bleeding test time, activated partial thromboplastin time , thrombin time and the PFA, a device which has not been fully utilized.
Vessel wall disorders
can lead to hemorrhaging
Individuals with Scurvy, Cushings disease, or Ehlers Danlos syndrome may be affected.
Thrombocytopenia, Thrombocytopathic and Glanzmanns Thrombasthenia
More common type of platelet disorder, ITP
the body’s inability to control blood clotting
Von Willebrand’s disease, Hemophilia (A and B)
disorder resulting from the breakdown of fibrinolytic system
Primary fibrinolysis typically results in bleeding and may be caused by a deficiency in plasmin inhibitor or plasminogen activator inhibitor"
Common signs and symptoms include prolonged bleeding or recurrent bleeding
Patients with bleeding disorders require thorough pre-operative, intra-operative and post-operative assessment prior to dental treatments.
A detailed dental, medical and pharmacological history is required. An oral exam may reveal signs of bleeding disorders. Utilize the INR test and consult with the physician when in doubt, to determine the best treatment option for the patient. Make sure bleeding has stopped before releasing the patient, and continue to monitor the patient for up to 48 hrs after the procedure.
Disorder resulting from a breakdown in the fibrinolytic system 
Hemorrhaging may occur when clot degradation is enhanced
Thrombosis may occur when clot breakdown mechanisms are impaired
Plasmin is the enzyme that cuts the fibrin mesh
"Primary fibrinolysis typically results in bleeding and may be caused by a deficiency in plasmin inhibitor or plasminogen activator inhibitor" 
Common Signs and Symptoms of Bleeding Disorder
Spontaneous or recurrent bleeding 
Bleeding disorders commonly exhibit large bruises on the trunks of the individual's body
nosebleeds lasting longer than 10 min
gingival bleeding w/o disease
Family history of blood disorders
Pallor- unhealthy pale appearance
Sepsis- inflammatory response to infection
Bruising of skin, palate, and gums
Hemarthrosis in joints 
Testing in Bleeding Disorders
Prothrombin Time Test (PT test)- helps in the diagnosis of clotting disorders and monitoring of medicated patients 
Blood sample taken and decalcified to prevent early clotting
Centrifugation to separate plasma
Add plasma to tissue factors (proteins or thromboplastin) which convert prothrombin to thrombin
Addition of calcium chloride to initiate clotting
11-15 seconds is normal clotting time range
prolonged PT indicates deficiency in factors VII, X, or V
prothrombin or fibrinogen may also be deficient 
International Normalized Ratio
Standardized Prothrombin Time that accounts for differences in thromboplastin
INR = [PTpatient ÷ MNPT]ISI
MNPT= mean normal prothrombin time; ISI= international sensitivity index
The INR does not predict the tendency of bleeding for patients with liver failure or systemic diseases
INR ranges from 0.9-1.1
Patients on Warafin, a vitamin k antagonist, have an INR value between 2 and 3.5