- Email: [email protected]
Management of the Coagulopathic Patient
8. Stone H, Hooper C, Kolb L, et at. Antibiotic prophylaxis in gastric, biliary, and colonic surgery. Ann Surg 1976;189:691-699. 9. Stone H, Haney B, Kolb L, et al. Prophylactic and preventive antibiotic therapy, timing, duration, and economics. Ann Surg 1979;189:691-699. 10. Pentecost M. Transcatheter treatment of hepatic metastases. Am J Roentgenol 1993;160: 1171. 11. Sternlicht M, Sales S, Daniels J, Daniels A. Effect of antimicrobial protection in tolerance to hepatic chemoembolization with a fibrous collagen carrier. Radiology 1989;170: 1067. 12. Charnsangavej C. Chemoembolization of liver tumors. Semin Int Radiol 1993;10:150. 13. Mauro M, Jaques P. Radiologic placement of longterm central venous catheters: A review. J Vasc Interv Radiol 1993;5:127-137. 14. Oppenshaw K, Picus D, Kicks M, Darcy M, Vesely T, Picus]. Interventional radiologic placement of tongterm central venous catheters: Results and complications in 100 consecutive patients. J Vasc Interv Radiol 1994;5: 111-115. 15. Lewis R, Goodall G, Marien B, Park M, Floyd-Smith W, Weigand F. Biliary bacteria, antibiotic use, and wound infection in surgery of the gallbladder and common bile duct. Arch Surg 1987;122:44-47. 16. Larsen E, Gasser T, Madsen P. Antibiotic prophylaxis in urologic surgery. Urol Clin North Am 1986;13: 591-604. 17. The Medical Letter. The choice of antimicrobial drugs. The Med Lett Drugs Ther 1998;40:33-41. 18. Dajani A, Taubert K, Wilson W, Bolger A, Bayer A, Ferrieri P, et al. Prevention of bacterial endocarditis: Recommendations by the American Heart Association. Circulation 1997;96:358-366. 4:55 pm Management of the Coagulopathic Patient Marcelle}. Shapiro, MD Children's Hospital of Philadelphia Philadelphia, Pennsylvania
326
Reprinted, with modifications, from ShapirO M]. Approach to the patient with a coagulopathy. J Vasc Interv Radiol 1998;9(Suppl):273-276. Learning objectives: As a result of attending this session, the attendee will be able to: 1) Understand the imporlance of preprocedure patient assessment combined with selective use ofcoagulation studies to identify patients with a potentially Significant coagulopathy; 2) Have gUidelines for the use offresh frozen plasma, vitamin K, andplatelets to prepare the patient with a coagulopathy for an interventional procedure; and 3) Understand the major risks of transfusion of such blood products.
Hemorrhage is a complication potentially associated with both vascular and nonvascular interventional radiologic procedures. Concern about morbidity and mortality due to excessive bleeding in a patient with an inadequately functioning hemostatic system historically led to the routine use of coagulation testing before surgery. Similar use of preprocedure testing has been applied in the practice of interventional radiology. In a survey of SCVIR members, Murphy et al 0) discovered that aside from ordering medically indicated studies, routine screening with laboratory tests before vascular and interventional procedures is common practice. The reported goals of such preprocedure testing are: the identification of abnormal values, which subject patients to an increased risk of complications; the ability to treat prophylactically and thereby reduce the abnormality and the risk; and the adjustment of timing of the procedure to reduce risk. All of this sounds reasonable. Yet, both retrospective and prospective studies for the past 15 years, which were prompted by simultaneous needs to reduce costs and maintain patient safety, have shown a low prevalence of abnormal coagulation tests and little predictive value for postoperative bleeding (2-12). Results of these studies also concluded that routine screening with prothrombin time/partial thromboplastin time (PT/PTD add nothing to the preoperative history and physical examination and that the value of these laboratory studies in an otherwise healthy patient undergoing an elective surgical procedure does not appear to warrant the cost. Several recent series that examined the efficacy of screening coagulation studies before routine diagnostic cardiac catheterization and angiography provided similar findings. Vincent and Brown (3) found a 4.9% prevalence of abnormal coagulation values in 1,462 patients undergoing cardiac catheterization; 87.5% of these abnormal values were predjctable by the history and physical examination, giving a sensitivity of 87.5%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 99.3%. Only 9 of 1,462 patients had unpredicted, marginally abnormal values, which proved to have no clinical sequelae. Wilson et al (4) conducted both a retrospective review and a prospective study of patients undergoing transfemoral angiography. In the retrospective study, abnormal clotting studies were found in 4 (3.7%) of 108 patients, all of whom had liver disease. None of these patients experienced a complication. In the prospective limb of the study,S of 200 patients had abnormal prothrombin ratios, 4 were therapeutically anticoagulated, and 1 had known hepatiC cirrhosis. None of these five patients had a complication. Interestingly, minor hemorrhagic complications not requiring transfusion occurred in 21 patients 00.5%), all with normal preprocedure coagulation studies. More recently, Darcy et al OS) prospectively studied 1,000 consecutive patients who underwent femoral arte-
rial puncture for a diagnostic or therapeutic vascular procedure to determine whether coagulation studies and/or platelet counts are useful predictors of postprocedure hematomas. This experience corroborated the previous authors' in that an abnormal PT/PIT did not correlate with an increased risk of postangiographic hematoma. These authors found, however, that patients with a platelet count less than 100,000 X 106/L were more than nine times as likely to develop a medium or large hematoma as those with a count greater than 100,000 X 106/L. Darcy et al (15) therefore advocated a baseline complete blood count including a platelet count in all patients undergoing an intra-arterial procedure. All of these authors maintain that preprocedure coagulation testing before an elective study should be reserved for patients with clinically apparent or documented bleeding disorders, significant liver disease, malabsorption, and those who are anticoagulated. In a recent publication in Radiology, Ray, Jr. and Shenoy (16) examined the effect of thrombocytopenia alone on the outcome of radiologic placement of central venous access devices. One hundred five patients had 87 tunneled catheters, 10 arm ports, and 8 chest POits placed by two interventional radiologists under fluoroscopic guidance. Coagulation parameters were within normal limits in all, and patients were subgrouped by platelet count as follows: Group A: platelets <50,000 X 106/L; Group B: platelets 50,000-100,000 X 106/L; and Group C: >100,000 X 106 /L. Only those patients in Group A (with severe thrombocytopenia) received one unit of Single donor platelets (1 apheresis unit) during placement of the venous access device. With a mean follow-up time of 41.2 days, there was no statistically Significant difference in immediate or delayed complications, leading the authors to conclude that radiologic placement of tunneled central venous access devices is safe in patients with thrombocytopenia. Of note, however, the average increase in platelet count after intraprocedural platelet transfusion was a modest 11,500 X
106 /L (range, 5,000-35,000 X 106 /L), which raises the question of the efficacy of prophylactic platelet transfusion. Additional prospective studies will be necessary to fully address this issue. Returning to preprocedure coagulation testing, it appears that the most important "test" to identify a patient with a potentiaJly Significant coagulopathy is a careful history and physical examination. According to Fellin et al (17), "Several areas should be stressed during the history in all patients, including unusual bleeding or thrombosis, family history of bleeding or thrombosis, nutritional habits, drug ingestion, and other medical problems, particularly hepatiC or renal disease." Findings during the physical examination that may raise concern for a potential bleeding problem include jaundice, petechia, ecchymosis, adenopathy, hepatomegaly, and splenomegaly. With a positive response or physical finding, coagulation studies then may define the specific
bleeding problem and permit preprocedure intervention. More globally speaking, Narr et al (18) from the Mayo Clinic recently examined the outcomes of patients with no laboratory assessment before anesthesia and surgery. One thousand forty-four patients ranging in age from 0 to 95 years (median age, 21 years), most of whom were relatively healthy, with no recent laboratory testing underwent anesthesia and surgery. They found no instance in which any patient harm resulted from a lack of preoperative assessment and laboratory testing. Narr et al (18) acknowledged, however, that patient histories and rapid intraoperative "stat labs" were consistently available when needed. These authors therefore concluded that "the role of the laboratory evaluation in the detection and treatment of subclinical problems in healthy surgical patients is minimal, and all preoperative laboratory assessment could be based on patient histolY and examination," again supporting the previous authors' conclusions. Further, the "elimination of routine preoperative laboratory tests helps to minimize the time, discomfort, and expense for the patient as well as the potential adverse effects of further assessment of clinically unimportant laboratory abnormalities (18)." Another safe, cost-effective alternative to routine preoperative laboratory screening that would complement a thorough history and physical examination is the use of previous test results. Macpherson et al (19) did a retrospective review of data on patients who had elective surgelY and determined the frequency of tests done during the year before surgelY and the frequency of clinically significant changes in these values. The median interval between the prior test and elective surgery was 2 months, with 70% of the tests done within 4 months of admission. Seventeen percent of patients with previously abnormal tests had abnormal admission test values that were likely to affect management, whereas only 0.4% of patients with previously normal tests had abnormal admission results that would have affected perioperative management. Based on this, patients who have prior abnormal laboratory results should be retested, whereas those with previously normal values within 4 months of the procedure need not undergo repeated studies unless a clinically significant change in the history or physical examination suggests a potential coagulopathy. By adopting a strategy of using the history and physical examination as a basis for ordering selective preprocedure studies or substituting previous tests (when available within a 4-month period) for routine preprocedure screening, the potential savings should be substantial without compromising patient care.
Periprocedure Treatment Guidelines Four years ago, the College of American Pathologists published guidelines to help the physician in selecting the proper blood component for obtaining and maintaining hemostasis once a patient with a coagulopathy is
327
identified (20). These gUidelines were developed for adults, and only those applicable to the interventional radiology patient are included here. Obviously, with complex situations or unusual coagulopathies, consultation with a hematologist is warranted. Fresh Frozen Plasma This contains all of the blood coagulation factors and naturally occurring inhibitors. One bag contains 200-250 mi. Fresh frozen plasma (FFP) prepared by plasmapheresis from a single donor contains a larger volume (400-600 m]) but may be preferable to 2 U of FFP. The use of FFP is indicated when the history reveals a congenital coagulation factor deficiency or the clinical course suggests that a coagulopathy is present, with active bleeding, and/or prophylactically before an interventional procedure. This should be documented by at least one of the following: PT >1.5 times the normal range (ie, PT usually> 18 sec; international normalized ratio [INR] >1.6); activated PTT >1.5 times top normal (ie, PTT usually >55-60 sec) in a specimen free of heparin; or coagulation factor assay <25% activity. Fresh frozen plasma is also indicated to reverse any warfarin effect. This would be necessary if immediate hemostasis is required to control active bleeding or before an invasive procedure (PT >18 sec, INR >1.6). Before an elective procedure, warfarin may be discontinued for 3-5 days with subsequent normalization of the prothrombin time. If ongoing anticoagulation is required, the patient may receive heparin administered intravenously before and after the procedure, with resumption of warfarin thereafter. The usual starting dose is two bags of FFP or 1 plasmapheresis unit (400-600 mI). Doses as high as 10-15 mIIkg may be required in some patients, although smaller doses, even one bag, may be sufficient in most patients with milder elevations. If platelets are also being transfused, however, for every 5-6 U of platelets, the patient is receiving a volume equivalent of one bag of FFP, including hemostatic levels of the coagulation factors. Prothrombin time or activated PTT should be rechecked after infusion to determine the need for additional transfusion. Of note, Factor VII has a much shorter half-life than the other factors. Therefore, the prothrombin time may become prolonged sooner than the activated PTT, which is a better indicator of the efficacy of treatment. The activated clotting time (AC1) as determined by a Hemachron is a quick alternative to laboratory assessment of the PTT and is extremely useful for patients requiring repeated transfusions.
328
Platelets The usual unit obtained from whole blood donation (within 8 hours of collection) contains 5.5-10 X 10 10 platelets, whereas a plateletpheresis unit contains approximately 4 X 1011 platelets. Six random donor units or 1 plateletpheresis unit contains a volume of 250-350 mi. The expected posttransfusion increment is 5,000-
8,000 mm 3 per unit of platelet concentrate within 1 hour of transfusion in the absence of alloinununization (21). Platelets are clinically indicated when decreased platelet production with or without increased platelet destruction is determined. At counts less than 5,0001 nun 3 , hemorrhage is extremely likely, either spontaneously or with trauma or an invasive procedure. With platelet counts between lO,OOO-50,000/mm 3 , the risk of bleeding with trauma or an invasive procedure increases. At >50,000/nun3 , bleeding caused by platelet deficiency is unlikely. Also, the efficacy of platelet transfusion is less well established in drug-related or other acquired platelet functional defects. Other methods of enhancing platelet function (ie, desmopressin) may be considered, and a Hematologist should be consulted. The dosage reqUired is that sufficient to increase the platelet count to more than 50,000/mm 3 , at least initially. As previously noted, an individual unit increases the count by 5,000-8,000/nun 3 . Based on body weight, a dosage of 1 U/I0 kg for random platelets or 1 apheresis unit for up to 90 kg may be used. When response to transfusion is poor, a count should be measured 10-60 minutes after the transfusion. If the increment is <7,5001 nun 3 , refractoriness to transfusion may be present. Such alloimmunized patients require apheresis platelets from HLA-matched donors. Vitamin K Any patient with a prolonged PT deserves a trial dose of vitamin K 10 mg parenterally (17). Only patients with biliary obstruction, malnutrition, or those receiving warfarin, however, are likely to respond. If warfarin needs to be continued after the procedure, vitamin K should not be used because this will prolong the time needed for therapeutic reanticoagulation. In patients with hepatocellular disease, the preferred therapy is FFP in doses of 10-20 mIIkg to bring the PT to within 2-3 seconds of the control value (17). Hazards of Transfusion The general hazards of transfusion of blood products are well known (22); a comprehensive review is well beyond the scope of this presentation. Risks must always be balanced against the need for transfusion. Nevertheless, the judicious use of optimum blood components only when indicated, in appropriate doses, with proper follow-up evaluation should decrease morbidity and provide optimal patient care. Major risks are as follows: 1. Viral diseases. The risk of hepatitis B or C is variable (1-5%) and usually presents as transaminasemia. Only occasionally will clinical hepatitis result. The risk of transmitting the HN virus is believed to be <1:40,000 because of vigorous screening (17).
2. Hemolysis caused by incompatible plasma. 3. Acute lung injury due to volume expansion or immunologic reaction.
4. Transmission of bacteria or endotoxins enhanced by room-temperature storage of platelets.
appraisal of coagulation studies prior to transfemoral angiography. Br] Radiol 1990;63:147-148.
5. Leukocyte-mediated processes. Graft-versus-host disease, cytomegalovirus, human T-cell lymphotrophic virus, and alloimmunization are caused by leukocyte contamination of platelet units.
15. Darcy MD, Kanterman RY, KJeinhoffer MA, et al. Evaluation of coagulation tests as predictors of angiographic bleeding complications. Radiology 1996; 198:741-744.
6. Alloimmunization to plasma, erythrocyte, platelet,
16. RaY,]r CE, Shenoy SS. Patients with thrombocytopenia: Outcome of radiologic placement of central venous access devices. Radiology 1997;204:97-99.
and leukocyte antigens. This may lead to allergic reactions, anaphylaxis, or sensitization.
References 1. Murphy TP, Dorfman GS, Becker J. Use of preprocedural tests by interventional radiologists. Radiology 1993; 186:213-220. 2. Robbins ]A, Rose SO. Partial thromboplastin time as a screening test. Ann Intern Med 1979;90:796-797. 3. Eika C, Havig 0, Godal He. Value of preoperative hemostatic screening. Scand] Haematol 1979;8:7994. 4. Rader ES. Hematologic screening tests in patients with operative prostatic disease. Urology 1978;11: 243-246. 5. Eisenberg ]M, Clarke ]R, Sussman SA. Prothrombin and partial thromboplastin times as preoperative screening tests. Arch Surg 1982;117:48-51.
17. Fellin FM, Murphy S. Perioperative evaluation of patients with hematologic disorders. In: Merli G], Weitz HH, eds. Medical Management of the Surgical Patient. Philadelphia, PAc W.B. Saunders, 1992:84-115. 18. Narr B], Warner ME, Schroeder DR, et al. Outcomes of patients with no laboratory assessment before anesthesia and a surgical procedure. Mayo Clin Proc 1997;72:505--509. 19. Macpherson OS, Snow R, Lofgren RP. Preoperative screening: Value of previous tests. Ann Intern Med 1990;113:969-973. 20. Development Task Force of the College of American Pathologists. Practice parameters for the use of fresh frozen plasma, cryoprecipitate, and platelets. ]AMA 1994;271 :777-781.
6. Kaplan EB, Sheiner LB, Boeckmann A], et al. The
21. Jensen R, Ens GE. Platelet component therapy. Clin Hemost Rev 1994;8:1-9.
usefulness of preoperative laboratory screening. ]AMA 1985;253:3576-3581.
22. Walker RH. Special report: Transfusion risks. Am] Clin Pathol 1987;88:374-378.
7. Suchman AI, Mushlin AI. How well does the activated partial thromboplastin time predict postoperative hemorrhage? ]AMA 1986;256:750-753.
Sunday, March 21, 1999 3:30 pm-5:30 pm
8. Turnbull ]M, Buck e. Value of preoperative screening investigations in otherwise healthy individuals. Arch Intern Med 1987;147:1101-1105.
Categorical Course: Vascular Imaging Part (1) (C102) Moderator: Martin R. Prince, MD, PhD
9. Rohrer M], Michelotti MC, Nahrwold 01. Prospective evaluation of the efficacy of preoperative coagula-
3:30 pill
tion testing. Ann Surg 1988;208:554-557.
Pulmonary CIA and MRA Warren B. Gefter, MD University of Pennsylvania Philadelphia, Pennsylvania
10. Suchman Ai, Griner PF. Diagnostic uses of the activated partial thromboplastin time and prothrombin time. Ann Intern Med 1986;104:810-816. 11. Ritter OM, Rettke SR, Lunn R], et al. Preoperative coagulation screen does not predict intraoperative blood product requirements in orthotopic liver transplantation. Transplant Proc 1989;21:3533-3534. 12. Wagner ]0, Moore 01. Preoperative laboratory testing for the oral and maxillofacial surgery patient. ] Oral Maxillofac Surg 1991;49:177-182. 13. Vincent GM, Brown W. Prothrombin time and partial thromboplastin time tests are unnecessary before routine cardiac catheterization. ] Intervent Cardiol 1990;3: 1-4. 14. WiJson NV, Corne ]M, Given-Wilson RM. Critical
Learning objectives: (1) Recommend appropriate imaging strategies for patients with suspected pulmonary embolism; (2) List the advantages and limitations of helical CTscanning and MR imaging in the diagnosis of pulmonary embolism; (3) Understand new investigational approaches to imaging ofpulmonary ventilation and perfusion. Recent advances in computed tomography and magnetic resonance imaging have enabled these techniques to be applied to the diagnosis of pulmonary embolism. This presentation will provide a review and update on pulmonary CTA and MRA, and will discuss potential new diagnostic imaging algorithms using CT and MR for the diagnosis of suspected PE.
329
326
Reprinted, with modifications, from ShapirO M]. Approach to the patient with a coagulopathy. J Vasc Interv Radiol 1998;9(Suppl):273-276. Learning objectives: As a result of attending this session, the attendee will be able to: 1) Understand the imporlance of preprocedure patient assessment combined with selective use ofcoagulation studies to identify patients with a potentially Significant coagulopathy; 2) Have gUidelines for the use offresh frozen plasma, vitamin K, andplatelets to prepare the patient with a coagulopathy for an interventional procedure; and 3) Understand the major risks of transfusion of such blood products.
Hemorrhage is a complication potentially associated with both vascular and nonvascular interventional radiologic procedures. Concern about morbidity and mortality due to excessive bleeding in a patient with an inadequately functioning hemostatic system historically led to the routine use of coagulation testing before surgery. Similar use of preprocedure testing has been applied in the practice of interventional radiology. In a survey of SCVIR members, Murphy et al 0) discovered that aside from ordering medically indicated studies, routine screening with laboratory tests before vascular and interventional procedures is common practice. The reported goals of such preprocedure testing are: the identification of abnormal values, which subject patients to an increased risk of complications; the ability to treat prophylactically and thereby reduce the abnormality and the risk; and the adjustment of timing of the procedure to reduce risk. All of this sounds reasonable. Yet, both retrospective and prospective studies for the past 15 years, which were prompted by simultaneous needs to reduce costs and maintain patient safety, have shown a low prevalence of abnormal coagulation tests and little predictive value for postoperative bleeding (2-12). Results of these studies also concluded that routine screening with prothrombin time/partial thromboplastin time (PT/PTD add nothing to the preoperative history and physical examination and that the value of these laboratory studies in an otherwise healthy patient undergoing an elective surgical procedure does not appear to warrant the cost. Several recent series that examined the efficacy of screening coagulation studies before routine diagnostic cardiac catheterization and angiography provided similar findings. Vincent and Brown (3) found a 4.9% prevalence of abnormal coagulation values in 1,462 patients undergoing cardiac catheterization; 87.5% of these abnormal values were predjctable by the history and physical examination, giving a sensitivity of 87.5%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 99.3%. Only 9 of 1,462 patients had unpredicted, marginally abnormal values, which proved to have no clinical sequelae. Wilson et al (4) conducted both a retrospective review and a prospective study of patients undergoing transfemoral angiography. In the retrospective study, abnormal clotting studies were found in 4 (3.7%) of 108 patients, all of whom had liver disease. None of these patients experienced a complication. In the prospective limb of the study,S of 200 patients had abnormal prothrombin ratios, 4 were therapeutically anticoagulated, and 1 had known hepatiC cirrhosis. None of these five patients had a complication. Interestingly, minor hemorrhagic complications not requiring transfusion occurred in 21 patients 00.5%), all with normal preprocedure coagulation studies. More recently, Darcy et al OS) prospectively studied 1,000 consecutive patients who underwent femoral arte-
rial puncture for a diagnostic or therapeutic vascular procedure to determine whether coagulation studies and/or platelet counts are useful predictors of postprocedure hematomas. This experience corroborated the previous authors' in that an abnormal PT/PIT did not correlate with an increased risk of postangiographic hematoma. These authors found, however, that patients with a platelet count less than 100,000 X 106/L were more than nine times as likely to develop a medium or large hematoma as those with a count greater than 100,000 X 106/L. Darcy et al (15) therefore advocated a baseline complete blood count including a platelet count in all patients undergoing an intra-arterial procedure. All of these authors maintain that preprocedure coagulation testing before an elective study should be reserved for patients with clinically apparent or documented bleeding disorders, significant liver disease, malabsorption, and those who are anticoagulated. In a recent publication in Radiology, Ray, Jr. and Shenoy (16) examined the effect of thrombocytopenia alone on the outcome of radiologic placement of central venous access devices. One hundred five patients had 87 tunneled catheters, 10 arm ports, and 8 chest POits placed by two interventional radiologists under fluoroscopic guidance. Coagulation parameters were within normal limits in all, and patients were subgrouped by platelet count as follows: Group A: platelets <50,000 X 106/L; Group B: platelets 50,000-100,000 X 106/L; and Group C: >100,000 X 106 /L. Only those patients in Group A (with severe thrombocytopenia) received one unit of Single donor platelets (1 apheresis unit) during placement of the venous access device. With a mean follow-up time of 41.2 days, there was no statistically Significant difference in immediate or delayed complications, leading the authors to conclude that radiologic placement of tunneled central venous access devices is safe in patients with thrombocytopenia. Of note, however, the average increase in platelet count after intraprocedural platelet transfusion was a modest 11,500 X
106 /L (range, 5,000-35,000 X 106 /L), which raises the question of the efficacy of prophylactic platelet transfusion. Additional prospective studies will be necessary to fully address this issue. Returning to preprocedure coagulation testing, it appears that the most important "test" to identify a patient with a potentiaJly Significant coagulopathy is a careful history and physical examination. According to Fellin et al (17), "Several areas should be stressed during the history in all patients, including unusual bleeding or thrombosis, family history of bleeding or thrombosis, nutritional habits, drug ingestion, and other medical problems, particularly hepatiC or renal disease." Findings during the physical examination that may raise concern for a potential bleeding problem include jaundice, petechia, ecchymosis, adenopathy, hepatomegaly, and splenomegaly. With a positive response or physical finding, coagulation studies then may define the specific
bleeding problem and permit preprocedure intervention. More globally speaking, Narr et al (18) from the Mayo Clinic recently examined the outcomes of patients with no laboratory assessment before anesthesia and surgery. One thousand forty-four patients ranging in age from 0 to 95 years (median age, 21 years), most of whom were relatively healthy, with no recent laboratory testing underwent anesthesia and surgery. They found no instance in which any patient harm resulted from a lack of preoperative assessment and laboratory testing. Narr et al (18) acknowledged, however, that patient histories and rapid intraoperative "stat labs" were consistently available when needed. These authors therefore concluded that "the role of the laboratory evaluation in the detection and treatment of subclinical problems in healthy surgical patients is minimal, and all preoperative laboratory assessment could be based on patient histolY and examination," again supporting the previous authors' conclusions. Further, the "elimination of routine preoperative laboratory tests helps to minimize the time, discomfort, and expense for the patient as well as the potential adverse effects of further assessment of clinically unimportant laboratory abnormalities (18)." Another safe, cost-effective alternative to routine preoperative laboratory screening that would complement a thorough history and physical examination is the use of previous test results. Macpherson et al (19) did a retrospective review of data on patients who had elective surgelY and determined the frequency of tests done during the year before surgelY and the frequency of clinically significant changes in these values. The median interval between the prior test and elective surgery was 2 months, with 70% of the tests done within 4 months of admission. Seventeen percent of patients with previously abnormal tests had abnormal admission test values that were likely to affect management, whereas only 0.4% of patients with previously normal tests had abnormal admission results that would have affected perioperative management. Based on this, patients who have prior abnormal laboratory results should be retested, whereas those with previously normal values within 4 months of the procedure need not undergo repeated studies unless a clinically significant change in the history or physical examination suggests a potential coagulopathy. By adopting a strategy of using the history and physical examination as a basis for ordering selective preprocedure studies or substituting previous tests (when available within a 4-month period) for routine preprocedure screening, the potential savings should be substantial without compromising patient care.
Periprocedure Treatment Guidelines Four years ago, the College of American Pathologists published guidelines to help the physician in selecting the proper blood component for obtaining and maintaining hemostasis once a patient with a coagulopathy is
327
identified (20). These gUidelines were developed for adults, and only those applicable to the interventional radiology patient are included here. Obviously, with complex situations or unusual coagulopathies, consultation with a hematologist is warranted. Fresh Frozen Plasma This contains all of the blood coagulation factors and naturally occurring inhibitors. One bag contains 200-250 mi. Fresh frozen plasma (FFP) prepared by plasmapheresis from a single donor contains a larger volume (400-600 m]) but may be preferable to 2 U of FFP. The use of FFP is indicated when the history reveals a congenital coagulation factor deficiency or the clinical course suggests that a coagulopathy is present, with active bleeding, and/or prophylactically before an interventional procedure. This should be documented by at least one of the following: PT >1.5 times the normal range (ie, PT usually> 18 sec; international normalized ratio [INR] >1.6); activated PTT >1.5 times top normal (ie, PTT usually >55-60 sec) in a specimen free of heparin; or coagulation factor assay <25% activity. Fresh frozen plasma is also indicated to reverse any warfarin effect. This would be necessary if immediate hemostasis is required to control active bleeding or before an invasive procedure (PT >18 sec, INR >1.6). Before an elective procedure, warfarin may be discontinued for 3-5 days with subsequent normalization of the prothrombin time. If ongoing anticoagulation is required, the patient may receive heparin administered intravenously before and after the procedure, with resumption of warfarin thereafter. The usual starting dose is two bags of FFP or 1 plasmapheresis unit (400-600 mI). Doses as high as 10-15 mIIkg may be required in some patients, although smaller doses, even one bag, may be sufficient in most patients with milder elevations. If platelets are also being transfused, however, for every 5-6 U of platelets, the patient is receiving a volume equivalent of one bag of FFP, including hemostatic levels of the coagulation factors. Prothrombin time or activated PTT should be rechecked after infusion to determine the need for additional transfusion. Of note, Factor VII has a much shorter half-life than the other factors. Therefore, the prothrombin time may become prolonged sooner than the activated PTT, which is a better indicator of the efficacy of treatment. The activated clotting time (AC1) as determined by a Hemachron is a quick alternative to laboratory assessment of the PTT and is extremely useful for patients requiring repeated transfusions.
328
Platelets The usual unit obtained from whole blood donation (within 8 hours of collection) contains 5.5-10 X 10 10 platelets, whereas a plateletpheresis unit contains approximately 4 X 1011 platelets. Six random donor units or 1 plateletpheresis unit contains a volume of 250-350 mi. The expected posttransfusion increment is 5,000-
8,000 mm 3 per unit of platelet concentrate within 1 hour of transfusion in the absence of alloinununization (21). Platelets are clinically indicated when decreased platelet production with or without increased platelet destruction is determined. At counts less than 5,0001 nun 3 , hemorrhage is extremely likely, either spontaneously or with trauma or an invasive procedure. With platelet counts between lO,OOO-50,000/mm 3 , the risk of bleeding with trauma or an invasive procedure increases. At >50,000/nun3 , bleeding caused by platelet deficiency is unlikely. Also, the efficacy of platelet transfusion is less well established in drug-related or other acquired platelet functional defects. Other methods of enhancing platelet function (ie, desmopressin) may be considered, and a Hematologist should be consulted. The dosage reqUired is that sufficient to increase the platelet count to more than 50,000/mm 3 , at least initially. As previously noted, an individual unit increases the count by 5,000-8,000/nun 3 . Based on body weight, a dosage of 1 U/I0 kg for random platelets or 1 apheresis unit for up to 90 kg may be used. When response to transfusion is poor, a count should be measured 10-60 minutes after the transfusion. If the increment is <7,5001 nun 3 , refractoriness to transfusion may be present. Such alloimmunized patients require apheresis platelets from HLA-matched donors. Vitamin K Any patient with a prolonged PT deserves a trial dose of vitamin K 10 mg parenterally (17). Only patients with biliary obstruction, malnutrition, or those receiving warfarin, however, are likely to respond. If warfarin needs to be continued after the procedure, vitamin K should not be used because this will prolong the time needed for therapeutic reanticoagulation. In patients with hepatocellular disease, the preferred therapy is FFP in doses of 10-20 mIIkg to bring the PT to within 2-3 seconds of the control value (17). Hazards of Transfusion The general hazards of transfusion of blood products are well known (22); a comprehensive review is well beyond the scope of this presentation. Risks must always be balanced against the need for transfusion. Nevertheless, the judicious use of optimum blood components only when indicated, in appropriate doses, with proper follow-up evaluation should decrease morbidity and provide optimal patient care. Major risks are as follows: 1. Viral diseases. The risk of hepatitis B or C is variable (1-5%) and usually presents as transaminasemia. Only occasionally will clinical hepatitis result. The risk of transmitting the HN virus is believed to be <1:40,000 because of vigorous screening (17).
2. Hemolysis caused by incompatible plasma. 3. Acute lung injury due to volume expansion or immunologic reaction.
4. Transmission of bacteria or endotoxins enhanced by room-temperature storage of platelets.
appraisal of coagulation studies prior to transfemoral angiography. Br] Radiol 1990;63:147-148.
5. Leukocyte-mediated processes. Graft-versus-host disease, cytomegalovirus, human T-cell lymphotrophic virus, and alloimmunization are caused by leukocyte contamination of platelet units.
15. Darcy MD, Kanterman RY, KJeinhoffer MA, et al. Evaluation of coagulation tests as predictors of angiographic bleeding complications. Radiology 1996; 198:741-744.
6. Alloimmunization to plasma, erythrocyte, platelet,
16. RaY,]r CE, Shenoy SS. Patients with thrombocytopenia: Outcome of radiologic placement of central venous access devices. Radiology 1997;204:97-99.
and leukocyte antigens. This may lead to allergic reactions, anaphylaxis, or sensitization.
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17. Fellin FM, Murphy S. Perioperative evaluation of patients with hematologic disorders. In: Merli G], Weitz HH, eds. Medical Management of the Surgical Patient. Philadelphia, PAc W.B. Saunders, 1992:84-115. 18. Narr B], Warner ME, Schroeder DR, et al. Outcomes of patients with no laboratory assessment before anesthesia and a surgical procedure. Mayo Clin Proc 1997;72:505--509. 19. Macpherson OS, Snow R, Lofgren RP. Preoperative screening: Value of previous tests. Ann Intern Med 1990;113:969-973. 20. Development Task Force of the College of American Pathologists. Practice parameters for the use of fresh frozen plasma, cryoprecipitate, and platelets. ]AMA 1994;271 :777-781.
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Sunday, March 21, 1999 3:30 pm-5:30 pm
8. Turnbull ]M, Buck e. Value of preoperative screening investigations in otherwise healthy individuals. Arch Intern Med 1987;147:1101-1105.
Categorical Course: Vascular Imaging Part (1) (C102) Moderator: Martin R. Prince, MD, PhD
9. Rohrer M], Michelotti MC, Nahrwold 01. Prospective evaluation of the efficacy of preoperative coagula-
3:30 pill
tion testing. Ann Surg 1988;208:554-557.
Pulmonary CIA and MRA Warren B. Gefter, MD University of Pennsylvania Philadelphia, Pennsylvania
10. Suchman Ai, Griner PF. Diagnostic uses of the activated partial thromboplastin time and prothrombin time. Ann Intern Med 1986;104:810-816. 11. Ritter OM, Rettke SR, Lunn R], et al. Preoperative coagulation screen does not predict intraoperative blood product requirements in orthotopic liver transplantation. Transplant Proc 1989;21:3533-3534. 12. Wagner ]0, Moore 01. Preoperative laboratory testing for the oral and maxillofacial surgery patient. ] Oral Maxillofac Surg 1991;49:177-182. 13. Vincent GM, Brown W. Prothrombin time and partial thromboplastin time tests are unnecessary before routine cardiac catheterization. ] Intervent Cardiol 1990;3: 1-4. 14. WiJson NV, Corne ]M, Given-Wilson RM. Critical
Learning objectives: (1) Recommend appropriate imaging strategies for patients with suspected pulmonary embolism; (2) List the advantages and limitations of helical CTscanning and MR imaging in the diagnosis of pulmonary embolism; (3) Understand new investigational approaches to imaging ofpulmonary ventilation and perfusion. Recent advances in computed tomography and magnetic resonance imaging have enabled these techniques to be applied to the diagnosis of pulmonary embolism. This presentation will provide a review and update on pulmonary CTA and MRA, and will discuss potential new diagnostic imaging algorithms using CT and MR for the diagnosis of suspected PE.
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