Coagulation Disorders

The urologist may encounter disorders of hemostasis and coagulation either in the preoperative evaluation of the patients for elective surgery or in the perioperative care of patients with acute bleeding disorders. Diagnosis of the specific disorder involved requires an evaluation of the patient's history, physical examination, and appropriate laboratory tests.

An accurate history and physical examination of a patient scheduled to undergo elective operation offer the most valuable source of information regarding the risk of bleeding during surgery. A patient with a history of bleeding, easy bruisability (either spontaneous or traumatic), frequent or unusual mucosal bleeding, exceptionally high menstrual flow in females, prior history of significant or life-threatening hemorrhage associated with invasive procedures, or a family history of such problems may be at risk. A history of repeated severe epistaxis or abnormal laboratory tests may also be significant. The intake of medications should always be elicited. Especially important are drugs such as aspirin and nonsteroidal anti-inflammatory drugs, and because these preparations are widely available "over the counter," it is important to inquire specifically about them. Patients may not consider the intake of aspirin or nonsteroidal anti-inflammatory drugs as being important enough to mention when interviewed unless a specific question is asked. The most common cause of bleeding "disorders" is prescription drugs such as aspirin and warfarin. In addition, a history of liver dysfunction, renal dysfunction, or major metabolic or endocrine disorder is useful in directing preoperative screening. Hypercoagulability states and disorders include a history of deep venous thrombosis, pulmonary embolus, valvular disease, embolic or thrombotic cere-brovascular event, and atrial fibrillation.

Physical examination also provides valuable information. Evidence of excessive bruising, joint deformities, petechiae or ecchymosis, hepatosplenomegaly, excessive mobility of joints, or increased elasticity of the skin are symptoms of disorders associated with excessive perioperative bleeding. Evidence of amyloidosis (such as thickening of the skin or tongue), multiple myeloma, or other hematologic malignancies is also revealing.

It is beyond the scope of this chapter to detail all screening tests for bleeding and coagulation disorders. A hematologist should be involved in the perioperative management of these patients. The extent of laboratory testing needed for patients with a normal history and physical examination has been debated. Routine preoperative laboratory screening is useful for patients undergoing major procedures, especially involving body cavities or operations with significant dissection and the creation of raw surfaces, or patients with an abnormal history or physical examination. Routine preoperative testing is indicated for all patients undergoing urologic laparoscopy since it fulfills criteria of significant surgery. Patients with infection, sepsis syndrome (or the systemic inflammatory response syndrome), malnutrition, organ failure, and other major systemic disorders also warrant preoperative screening before surgical intervention.

In general, the commonly recommended tests include the prothrombin time, the partial thromboplastin time, a complete blood cell count with platelet count, and in some patients, a bleeding time.

The prothrombin time measures the function of factor VII as well as the common pathway factors (factor X, prothrombin/thrombin, fibrinogen, and fibrin). The partial thromboplastin time measures the intrinsic pathway and reflects the activity of all clotting factors except for platelet factor III , VII, and XII. For this reason, the test is complementary to the prothrombin time and may indicate deficiencies of other clotting factors or the presence of a circulating anticoagulant.

Venous thromboprophylaxis should be considered for every patient undergoing laparoscopic urological surgery, especially certain populations with high-risk factors.

All of the major coagulation factors are synthesized in the liver except for factor VIII, which is made in vascular endothelium and reticuloendothelial cells. The prothrombin time measures the activity of several of these factors, including factors I, II, V, VII, and X. Synthesis of prothrombin and factors VII, IX, and X depends on an adequate supply of vitamin K, which activates certain hepatic polypeptides by stimulating the synthesis of the calcium-binding residue, gamma-carboxyglutamic acid. An abnormal prothrombin time is commonly caused by vitamin K deficiency, liver disease, or both, and may rarely be seen with inherited abnormalities. Vitamin K, a fat-soluble vitamin that is found in many foods, is also produced by intestinal bacteria. Deficiency is most commonly seen in malnutrition and malabsorption syndromes, including failure to absorb dietary fat due to biliary obstruction or other causes of cholestasis. It may also be seen with antibiotic suppression of intestinal bacteria, especially when the patient is receiving inadequate oral or parenteral vitamin K replacement. Any acute or chronic liver disease may cause an abnormal prothrombin time by impairing the synthesis of essential clotting factors. Because the plasma half-life of these factors is typically less than one day, the prothrombin time responds rapidly to changes in hepatic synthetic function (7).

The platelet count identifies numbers of platelets, whereas the bleeding time estimates qualitative platelet function. None of the commonly recommended screening tests measures fibrinolytic function. Additional screening tests that may be used for specific patients include a fibrinogen level, the thrombin time, and screens for factor XIII levels. The thrombin time detects abnormalities of globulin, fibrinogen, excess fibrinolysis, and heparin-like substances. In patients suspected of having platelet dysfunction, additional assessments include platelet function tests (aggregation with epinephrine, adenosine diphosphate, collagen, and ristocetin). If a deficiency or specific factor is suspected, as in patients with a family history of hemophilia, then specific factor assays should be obtained (8).

Venous thromboprophylaxis should be considered for every patient undergoing laparoscopic urological surgery, especially certain populations with high-risk factors.

Patients who are elderly, obese, have a malignancy, or previous history of thrombosis are at increased risk of experiencing deep venous thrombosis and pulmonary embolus after surgery. Surgical factors are related to the extent of the operation and the type of anesthesia. Graduated compressive devices help to prevent thrombus formation and are suitable for low-risk patients. But those in the higher risk categories need to be anticoagulated as well. Subcutaneous unfractionated heparin and low molecular weight heparins have been found to be safe and effective in clinical practice.

Patients on aspirin or antiplatelet medication should stop these drugs 5-7 days preoperatively in order to normalize the bleeding time. In an emergency situation, desmopressin or platelet transfusion should be administered to avoid excessive risk of bleeding.

Patients on warfarin who are not at increased risk of thromboembolic events (such as previous history of venous thrombosis without recent recurrences) can stop the medication five days preoperatively, and resume the same dose on the first postoperative day if adequate hemostasis was obtained. Patients who are at moderate to high risk (atrial fibrillation), in whom warfarin cannot be stopped without replacement therapy, are started on subcutaneous low molecular weight heparin. These agents are stopped 12-24 hours before surgery and then resumed 12-24 hours postoperatively. If the prothrombin time did not normalize the day of surgery, vitamin K and/or fresh frozen plasma should be administered. Patients at very high risk should be converted on to intravenous heparin and monitored in hospital. Intravenous heparin is stopped six hours preoperatively to ensure normal partial thromboplastin time at the time of surgery, and heparin is resumed postoperatively as soon as the patient's condition permits. Warfarin is resumed when the patient is back on regular diet, and heparin is discontinued when coagulation tests have been within therapeutic levels for 48 hours. This period of overlap is called bridging and protects the patient from the initial transient prothrombotic effect of warfarin. There is always a fine balance between bleeding and hypercoagulability in these patients that needs to be judiciously determined in collaboration with the medical team.

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