A Practical Concept for Preoperative Identification of Patients with Impaired Primary Hemostasis

[Preoperative evaluation of the bleeding history. Recommendations of the working group on perioperative coagulation of the Austrian Society for Anaesthesia, Resuscitation and Intensive Care]

Unexpected bleeding in the perioperative period is largely caused by impaired inherited or drug-induced primary haemostasis. Standard tests for plasma coagulation are predominantly employed to gauge the risk of bleeding. In accordance with several reports the subcommittee for perioperative coagulation (AGPG) of the Austrian Society of Anaesthesia, Resuscitation and Intensive Care (OGARI) recommends the use of a standardised questionnaire to detect an increased risk of bleeding. Accordingly, healthy patients of the American Society of Anesthesiologists (ASA) grades I and II without any suspicion of impaired haemostasis who are scheduled for procedures without expected transfusion requirements, need no standard tests for coagulation. In all other patients (including patients taking medication affecting coagulation, or patients who are unable to provide adequate information) platelet count, platelet function, aPTT, PT, and fibrinogen levels should be assessed.

Periduralanästhesie

In epidural anaesthesia, the anaesthetist injects one or more drugs into the epidural space bordering on the spinal dura mater to achieve a "central" and/or "neuraxial" block. It is one of the earliest techniques in anaesthesia, originally performed exclusively with local anaesthetic agents. Adding other drugs and combining epidural with general anaesthesia or adapting the technique to the needs of children has extended the list of indications. Continuous epidural analgesia is an important tool in postoperative pain management. More and more often, the increasing proportion of patients who have comorbidities or are permanently taking medication that modulates the clotting system demands that the anaesthesiologist balance the individual risks and benefits before inducing epidural anaesthesia.

Hemostatic Function in Healthy Pregnant and Preeclamptic Women: An Assessment Using the Platelet Function Analyzer (PFA-100??) and Thromboelastograph??

BACKGROUND

The PFA-100 is a point-of-care platelet function analyzer which measures the speed of formation of a platelet plug in vitro, expressed as closure time (CT) in seconds. This device could potentially be used to assess primary hemostasis prior to regional anesthesia. In this prospective, observational study we sought to establish 95% reference intervals for PFA-100 and Thromboelastograph (TEG) values for our normal pregnant population, before comparing the PFA and TEG in measuring platelet function in preeclamptic and healthy pregnant women at term, using confidence interval analysis and analysis of variance.

METHODS

Routine hematologic and coagulation tests were performed along with von Willebrand Factor, CT, and TEG measurements. Results are expressed as mean (sd).

RESULTS

Increased severity of preeclampsia was associated with increasing prolongation of CT, even in the presence of normal platelet counts. In severe preeclampsia, the PFA-100 CT (mean (sd): 155 (65) s) exceeded the 95% reference interval of the control group (70-139 s). In contrast, TEG maximum amplitude (MA) in severe preeclampsia (mean (sd): 71 (8) mm) remained within the 95% reference interval for MA in normal pregnancy (64-82 mm).

CONCLUSION

We conclude that impairment of primary hemostatic function with increasing severity of preeclampsia was recorded by the PFA-100 but not the TEG.

[Spinal anaesthesia]

In spinal anaesthesia, surgical analgesia and in most cases motor block is achieved by injecting one or more drugs into the cerebrospinal fluid. As one of the earliest methods of anaesthesia it was introduced into clinical practice in the late nineteenth century. Although later on it was more or less replaced by "modern" general anaesthesia, it has regained popularity due to its benefits for certain patient populations. In spite of being a technically simple procedure, performing spinal anaesthesia requires a sound knowledge of applied physiology and pharmacology, especially in high-risk groups such as pregnant women or former preterm babies. For some patients even under anticoagulant therapy, spinal anaesthesia might be the best option, considering the individual risk of alternative methods.

Platelet function analyzer (PFA)-100 closure time in the evaluation of platelet disorders and platelet function

BACKGROUND

Closure time (CT), measured by platelet function analyzer (PFA-100) device, is now available to the clinical laboratory as a possible alternative or supplement to the bleeding time test.

AIM

On behalf of the Platelet Physiology Subcommittee of the Scientific and Standardization Committee of the International Society on Thrombosis and Haemostasis (ISTH-SSC), a working Group was formed to review and make recommendations on the use of the PFA-100 CT in the evaluation of platelet function within the clinical laboratory.

METHODS

The Medline database was searched to review the published information on the PFA-100 CT in the evaluation of platelet disorders and platelet function. This information, and expert opinion, was used to prepare a report and generate consensus recommendations.

RESULTS

Although the PFA-100 CT is abnormal in some forms of platelet disorders, the test does not have sufficient sensitivity or specificity to be used as a screening tool for platelet disorders. A role of the PFA-100 CT in therapeutic monitoring of platelet function remains to be established.

CONCLUSIONS

The PFA-100 closure time should be considered optional in the evaluation of platelet disorders and function, and its use in therapeutic monitoring of platelet function is currently best restricted to research studies and prospective clinical trials.

The role of PFA-100R testing in the investigation and management of haemostatic defects in children and adults

The PFA-100 provides a simple global measure of high shear-dependent platelet function, and as such is not diagnostic or specific to any disorder. Prolonged closure times must be interpreted in conjunction with a full blood count, von Willebrand factor (VWF) screen and other platelet tests. The PFA-100 may also give false negative results with relatively common platelet defects. If clinical suspicion is high, further detailed platelet function testing and VWF screening are required to exclude abnormal platelet function, even if the PFA-100 is normal. In more recent studies the PFA-100 has been used for preoperative identification and management of surgical patients with haemostatic defects and for assessing the clinical effectiveness of platelet transfusion therapy. This review highlights the up to date, evidence-based, advantages and disadvantages of the PFA-100 test in the investigation and management of haemostatic disorders in both children and adults.

Lokoregionalanästhesien unter gerinnungshemmender Medikation

More efficacious anticoagulant and antiplatelet agents have been introduced in vascular medicine and in the prevention of perioperative venous thromboembolisms. Patient management should be guided by familiarity with the pharmacology of coagulation-altering drugs and by consensus statements. The present paper reviews recommendations from the Austrian Task Force for Perioperative Coagulation which are based on thorough evaluation of the available pharmacological information and case reports. The consensus statement focuses on neuraxial and peripheral techniques and is designed to encourage safe and quality patient care.

Perioperative Gerinnungsdiagnostik

The main diagnostic tool for the preoperative identification of patients with an increased risk of bleeding or thrombosis is the patient history. Laboratory diagnostics should only be performed if a bleeding diathesis is suspected from patient history or clinical symptoms of bleeding, or if an adequate patient history cannot be performed. Measurement of prothrombin time, aPTT, or bleeding time as a general preoperative screening procedure is neither cost-effective nor efficient for the identification of patients with increased bleeding risk. Normal values of prothrombin time and aPTT do not exclude the most prevalent bleeding disorder, von Willebrand's disease. A normal platelet count does not exclude a severe platelet function defect. Selection of specific laboratory assays is performed on the basis of the individual patient history and clinical picture; laboratory 'profiles' can be defined for some specific clinical conditions. In some cases, patients should be referred to a specialized coagulation clinic for further diagnostics and treatment planning. Preoperative laboratory diagnostics for thrombophilia are not necessary in most cases. The decision for intensified antithrombotic measures is made according to patient history and the postoperative clinical course.

Diagnosis and Management of Mild Bleeding Disorders

Mild bleeding disorders are a common reason for a referral to a hematologist and these conditions can be challenging to evaluate. Recent research has highlighted that some bleeding symptoms are quite common in the general population and that there is clinical variability in symptom expression among individuals with defined bleeding problems. Moreover, bleeding risks for many bleeding disorders are unknown. This article reviews symptoms and problems that can be considered suspicious of a mild form of bleeding disorder and the diagnostic investigations useful to evaluate these problems. A stepwise approach is presented for the diagnostic evaluation, to allow detection of common and rare coagulation and fibrinolytic defects, and adequate assessments of potential von Willebrand factor and platelet problems. Some common problems in the diagnosis and management of mild bleeding problems are reviewed, including the common failure to establish a diagnosis with testing. An approach is proposed for translation of knowledge to patients who are challenged by mild bleeding problems.