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

Platelets: still a therapeutical target for haemostatic disorders

Platelets are cytoplasmatic fragments from bone marrow megakaryocytes present in blood. In this work, we review the basis of platelet mechanisms, their participation in syndromes and in arterial thrombosis, and their potential as a target for designing new antithrombotic agents. The option of new biotechnological sources is also explored.

Perioperative coagulopathy monitoring

Coagulopathy is common in orthopedic surgery patients either due to acquired factors, such as surgery, trauma, medications, or hemorrhage. Perioperative monitoring of blood coagulation is critical to diagnose the causes of hemorrhage, guide hemostatic therapies, predict the risk of bleeding during surgical procedures, and reduce risk of postoperative cardiac and thromboembolic events. In contrast to previous interventions that measure specific portions of the clotting cascade (such as intrinsic or extrinsic pathways or platelet aggregation), "Point-of-care" coagulation monitoring devices assess the viscoelastic properties of whole blood. These techniques have the potential to measure the entire clotting process, starting with fibrin formation, clot retraction, and fibrinolysis. Furthermore, the coagulation status of patients is assessed in whole blood, allowing the plasmatic coagulation system to interact with platelets and red cells, and thereby providing useful additional information on platelet function. Improved monitoring of coagulopathy is particularly important as new anticoagulant drugs emerge that affect the clotting cascade in novel ways, including the inhibition of intrinsic and extrinsic pathways and platelet function. It is important for orthopedic surgeons to understand the pharmacology and reversal of these drugs in the perioperative setting. The purpose of this review is to review the current techniques to monitoring perioperative coagulopathy and to identify the manner in which novel anticoagulant medications affect the clotting cascade with particular interest in trauma and spine surgery.

Fibrinogen but not factor XIII deficiency is associated with bleeding after craniotomy

BACKGROUND

Postoperative haemorrhage in neurosurgery is associated with significant morbidity and mortality. There is controversy whether or not factor XIII (FXIII) deficiency leads to bleeding complications after craniotomy. Decreased fibrinogen levels have been associated with an increased incidence of bleeding complications in cardiac and orthopaedic surgery. The aim of this study was to assess perioperative fibrinogen and FXIII levels in patients undergoing elective intracranial surgery with and without severe bleeding events.

METHODS

Perioperative FXIII and fibrinogen levels were prospectively assessed in 290 patients undergoing elective craniotomy. Patients were divided into two groups according to the presence or absence of severe bleeding requiring surgical revision. Coagulation test results of these groups were compared using Student's t-test.

RESULTS

The incidence of postoperative severe bleeding was 2.4%. No differences in FXIII levels were observed, but postoperative fibrinogen levels were significantly lower in patients suffering from postoperative haematoma compared with those without postoperative intracranial bleeding complications [237 mg dl(-1) (standard deviation, SD 86) vs 170 mg dl(-1) (SD 35), P=0.03]. The odds ratio for postoperative haematoma in patients with a postoperative fibrinogen level below 200 mg dl(-1) was 10.02 (confidence interval: 1.19-84.40, P=0.03).

CONCLUSIONS

This study emphasizes the role of fibrinogen as potentially modifiable risk factor for perioperative bleeding in intracranial surgery. Future randomized controlled trials will be essential to identify patients who might benefit from fibrinogen substitution during neurosurgical procedures.

Emerging new trends in neurosurgical technologies

There has been tremendous progress in the modern day technologies causing a rapid evolution in the field of neurosurgery. The neurosurgeons have been equipped with the latest advancements such as the use of robotics in surgery, the image-guided neurosurgical procedures, and the stereotactic neurosurgery. In addition, the preoperative screening techniques have drastically improved the success of the surgical procedure. Neuronavigation has allowed the precise localization of the deep-seated brain structures thereby helping in the accurate operation of the affected regions without stirring the normal brain tissues. Such preciseness has helped in the improvement of the patient outcome. All these aspects have been discussed in detail in this review with a focus on their developmental background.

Platelet function testing: state of the art

Platelet function testing has evolved from crude tests, such as the bleeding time, to tests that permit a relatively sophisticated evaluation of platelet activity. Nonetheless, these tests are hampered by lack of specificity and sensitivity, and poor standardization of methods and techniques. The bleeding time, which has long been a staple of hemostasis testing, has been dropped from the test menu at many laboratories. In its place, tests such as the Platelet Function Analyzer-100 are increasingly used to screen patients with possible bleeding disorders. Older tests, such as platelet aggregometry and lumiaggregometry, are still used frequently because they provide insight into receptor, signaling pathway and granule release mechanisms. Flow cytometry is available in some specialized laboratories and allows for quantitative and qualitative assessment of some platelet functions, although the expense of testing is often prohibitive. Finally, the wider availability of platelet function testing has stimulated interest and demand for monitoring the effect of platelet inhibitory drugs, such as aspirin and clopidogrel. As platelet function pathways become better understood, the demand for these type of monitoring tests is likely to increase.

Patients with disorders of thrombosis and hemostasis

Surgery, by definition, is a challenge to the hemostatic system. In addition, a surgical procedure may provoke inappropriate venous or arterial thrombosis, such as is suggested historically by Virchow's Triad. For these reasons, proper functioning of the hematologic system is integral in a successful and safe perioperative period. Patients with a disorder of either coagulation or hemostasis, therefore, present an exciting challenge to the preoperative physician. Diagnosis of a hematologic disorder may be more or less occult. A proper bleeding and clotting history can serve to elucidate such a disorder and is therefore paramount to the preoperative workup. For those patients with a previously diagnosed disorder of the hematologic system, appropriate laboratory investigation and a concise therapeutic plan for the day of surgery can help to minimize risks in the perioperative period.

Coagulation pattern in critical liver dysfunction

PURPOSE OF REVIEW

This article reviews the current literature dealing with pathophysiology, diagnostics, bleeding management, and thromboprophylaxis in patients with acute and chronic liver dysfunction.

RECENT FINDINGS

Routine coagulation tests such as prothrombin time and International Normalized Ratio (INR) are not able to define whether a patient with critical liver dysfunction is hypocoagulable or hypercoagulable and are not able to predict the risk of bleeding in patients with liver dysfunction. Therefore, prophylactic transfusion of fresh frozen plasma and platelets in order to correct laboratory values is not appropriate. Notably, patients with liver dysfunction and increased INR are not 'autoanticoagulated'. In contrast, thrombin generation assays in the presence and absence of thrombomodulin or Protac, a snake venom that activates protein C in a manner similar to thrombomodulin, as well as viscoelastic tests (thrombelastography/thromboelastometry) indicate that patients with liver dysfunction are rather hypercoagulable with the inherent risk of thrombosis.

SUMMARY

Coagulopathy in patients with critical liver dysfunction is complex and can quickly decompensate to bleeding as well as to thrombosis. Both are associated with worse outcome. Hemostatic interventions should only be performed in case of clinically relevant bleeding and thromboprophylaxis should strongly be considered.

Pre-interventional haemostatic assessment: Guidelines from the French Society of Anaesthesia and Intensive Care

Recently the French Society of Anaesthesia and Intensive Care (Société Française d'Anesthésie et de Réanimation [SFAR]) issued recommendations for the prescription of routine preoperative testing before a surgical or non-surgical procedure, requiring any type of anaesthesia. Thirty clinical specialists performed a systematic analysis of the literature, and recommendations were then developed using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) system. One part of these guidelines is dedicated to haemostatic assessment. The goal of pre-anaesthetic screening for congenital or acquired haemostatic disorders is to prevent perioperative haemorrhagic complications through appropriate medical and surgical management. Preoperative assessment of bleeding risk requires a detailed patient interview to determine any personal or family history of haemorrhagic diathesis, and a physical examination is necessary in order to detect signs of coagulopathy. Laboratory investigation of haemostasis should be prescribed, not systematically, but depending on clinical evaluation and patient history. Standard tests (prothrombin time, activated partial thromboplastin time, platelet count) have a low positive predictive value for bleeding risk in the general population. Patients with no history of haemorrhagic diathesis and no conditions liable to interfere with haemostasis should not undergo pre-interventional haemostasis testing. Conversely, the existence of a positive history or a disease that could interfere with haemostasis should be an indication for clinically appropriate testing.

A brief review of 50 years of perioperative thrombosis and hemostasis management

Perioperative thrombosis and hemostasis management has changed dramatically over the past 50 years. From two anticoagulants and one anti-aggregant, the number of currently available drugs has recently increased several-fold, leaving clinicians with the problem of choosing the optimal agent. Individualized preoperative assessment of bleeding risk based on bleeding history and testing limited to high-risk patients is an emerging concept. Based on the identification of risk factors for venous thromboembolism (VTE), pharmacologic and non-pharmacologic strategies for perioperative VTE prophylaxis have had a major impact on patient outcome. For patients undergoing surgery who are treated with anticoagulants and anti-aggregants, "bridging" strategies have been proposed. Bleeding management strategies have shifted focus from replacing lost blood volume to new approaches aimed at preventing blood loss, reducing the potential complications of blood loss, and preventing the transfusion of blood products. For some areas of perioperative thrombosis and hemostasis management, randomized controlled trial (RCT) data are emerging, but the database remains insufficient to date. Clearly, more RCTs need to be published for perioperative thrombosis and hemostasis management to become an evidence-based approach.

Haemostatic monitoring during postpartum haemorrhage and implications for management

Postpartum haemorrhage (PPH) is a major risk factor for maternal morbidity and mortality. PPH has numerous causative factors, which makes its occurrence and severity difficult to predict. Underlying haemostatic imbalances such as consumptive and dilutional coagulopathies may develop during PPH, and can exacerbate bleeding and lead to progression to severe PPH. Monitoring coagulation status in patients with PPH may be crucial for effective haemostatic management, goal-directed therapy, and improved outcomes. However, current PPH management guidelines do not account for the altered baseline coagulation status observed in pregnant patients, and the appropriate transfusion triggers to use in PPH are unknown, due to a lack of high-quality studies specific to this area. In this review, we consider the evidence for the use of standard laboratory-based coagulation tests and point-of-care viscoelastic coagulation monitoring in PPH. Many laboratory-based tests are unsuitable for emergency use due to their long turnaround times, so have limited value for the management of PPH. Emerging evidence suggests that viscoelastic monitoring, using thrombelastography- or thromboelastometry-based tests, may be useful for rapid assessment and for guiding haemostatic therapy during PPH. However, further studies are needed to define the ranges of reference values that should be considered ‘normal’ in this setting. Improving awareness of the correct application and interpretation of viscoelastic coagulation monitoring techniques may be critical in realizing their emergency diagnostic potential.

The Platelet Function Analyzer (PFA-100) as a Screening Tool in Neurosurgery

We investigated whether the inclusion of the PFA-100 in the preoperative screening of neurosurgical patients might reduce perioperative bleeding complications. Patients with intracranial space-occupying lesions who were scheduled for neurosurgery underwent routine preoperative PFA-100 testing. In case of an abnormal PFA test, patients received prophylactic treatment with desmopressin. 93 consecutive patients were compared to 102 consecutive patients with comparable characteristics operated before introduction of the PFA-100 testing. 2 patients (2.2%) in the PFA group and 2 patients (2.0%) in the non-PFA group experienced clinically relevant intracranial bleeding confirmed by computed tomography (OR 1.05, 95% CI 0.39–2.82; P = 1.0). Transfusions were not significantly different between the two groups. 13 (14.0%) patients in the PFA group and 5 (4.9%) patients in the non-PFA group received desmopressin (OR 3.2, 95% CI 1.1–9.2; P = 0.045). Preoperative screening with the PFA-100 did result in a significant increase in the administration of desmopressin, which could not reduce perioperative bleeding complications or transfusions.

[Intraoperative surgical and anesthesiological problems and the consequences for surgery]

Although the procedures for severe intraoperative complications have largely been defined, in everyday life less dramatic but equally important problems and issues arise which are controversially debated between treating surgeons and the anesthesiologists. Preoperative anemia, transfusion therapy, fluid management, patient positioning, hypothermia and neuromuscular blockade are the focus of the occasionally conflicting interests of anesthesiologists and surgeons. Good reciprocal communication and mutual understanding are a requirement for proactive management of complications. The overall objective is the reduction of intraoperative risks thereby reducing morbidity and mortality. This can be achieved through modern fluid management, blood conserving techniques and maintenance of normothermia. Surgeons further require an optimal view during minimally invasive surgery even by complex patient positioning and adequate neuromuscular blockade.

Perioperative point of care coagulation testing

BACKGROUND

Conventional laboratory tests of blood coagulation yield only partial diagnostic information. "Point of care" (POC) devices are increasingly being used at the bedside perioperatively for rapid, detailed testing of hemostatic function and for treatment monitoring in patients with coagulopathies. In this review, we discuss the benefits and limitations of POC coagulation testing-in particular, its effects on the rate of perioperative transfusion of allogeneic blood products, on the frequency of other types of hemostatic treatment, and on the clinical outcome.

METHODS

This article is based on a selective review of pertinent literature retrieved by a search in PubMed.

RESULTS

The clinical value of preoperative POC screening for coagulopathies has not yet been examined in a prospective, randomized clinical trial. On the other hand, studies in patients with coagulopathies undergoing (mainly cardiac) surgery have shown that algorithm-based hemostatic treatment based on viscoelastic POC coagulation testing reduces both perioperative blood loss and the rate of transfusion of allogeneic blood products. None of the studies published to date had adequate power to reveal any independent effect of POC coagulation testing on perioperative morbidity or mortality.

CONCLUSION

Despite certain limitations that must be borne in mind, POC techniques are a valuable means of testing various aspects of hemostasis rapidly and in detail. Their implementation in hemostatic treatment algorithms may reduce both the rate of transfusion of allogeneic blood products and the total cost of treatment for blood loss and coagulopathies. The putative effect of POC testing on perioperative morbidity and mortality has not yet been demonstrated.

Abnormal pre-operative tests, pathologic findings of medical history, and their predictive value for perioperative complications

BACKGROUND

Laboratory tests, electrocardiogram (ECG) and chest X-rays still serve as part of the routine assessment before elective surgery in many institutions, even though there is little evidence of their predictive value relating to perioperative complications. This study investigates the correlation of abnormal findings in pre-operative tests and pathologic findings in the medical history with perioperative complications.

METHODS

Patients scheduled for elective surgery in a secondary care hospital were included in this prospective cohort study. Abnormal pre-operative tests, significant findings from the medical history and perioperative complications were recorded. Regression analysis was performed in order to identify the strongest predictors for perioperative complications.

RESULTS

A total of 1363 (56.1% female) patients were consecutively included in this study. The percentage of abnormalities in pre-operative tests ranged from 1.6% (electrolytes) and 29.7% (echocardiography). Eighty-six (6.3%) patients had at least one perioperative complication. The most frequent complications were hypo- or hypertension in 55 cases (4.0%), followed by 20 patients (1.5%) who suffered from hemodynamically relevant cardiac dysrhythmias such as supraventricular tachycardia, ventricular tachycardia, bradycardia and ventricular extrasystoles. The binary logistic regression analysis to identify predictors of perioperative complications showed significant results for age, invasiveness of the procedure, history of renal disease or anemia and abnormal ECG.

CONCLUSION

Our results indicate that age, type of surgery and medical history are appropriate predictors of perioperative complications, whereas abnormalities in laboratory tests seem to have restricted ability in predicting adverse perioperative outcome.

Impact of loss of high-molecular-weight von Willebrand factor multimers on blood loss after aortic valve replacement

BACKGROUND

Severe aortic stenosis is associated with loss of the largest von Willebrand factor (vWF) multimers, which could affect primary haemostasis. We hypothesized that the altered multimer structure with the loss of the largest multimers increases postoperative bleeding in patients undergoing aortic valve replacement.

METHODS

We prospectively included 60 subjects with severe aortic stenosis. Before and after aortic valve replacement, vWF antigen, activity, and multimer structure were determined and platelet function was measured by impedance aggregometry. Blood loss from mediastinal drainage and the use of blood and haemostatic products were evaluated perioperatively.

RESULTS

Before operation, the altered multimer structure was present in 48 subjects (80%). Baseline characteristics and laboratory data were similar in all subjects. The median blood loss after 6 h was 250 (105-400) and 145 (85-240) ml in the groups with the altered and normal multimer structures, respectively (P=0.182). After 24 h, the cumulative loss was 495 (270-650) and 375 (310-600) ml in the groups with the altered and normal multimer structures, respectively (P=0.713). Multivariable analysis revealed no significant influence of multimer structure and platelet function on bleeding volumes after 6 and 24 h. After 24 h, there was no obvious difference in vWF antigen, activity, and multimer structure in subjects with and without the altered multimer structure before operation or in subjects with and without perioperative plasma transfusion.

CONCLUSIONS

The altered vWF multimer structure before operation was not associated with increased bleeding after aortic valve replacement. Our findings might be explained by perioperative release of vWF and rapid recovery of the largest vWF multimers.

[Current coagulation diagnostics in intensive care medicine]

In the preoperative setting, a standardized questionnaire on bleeding history cannot be replaced by the Quick test or activated partial thromboplastin time (APTT) measurement. Thrombelastometry provides rapid measurement of coagulation in the intra- and postoperative settings. Besides the Quick test and APTT, thrombelastometry provides information about clot firmness and clot stability. This allows goal-directed management in coagulopathy, which results in a reduction of transfusion of blood products. Furthermore, this can lead to not only an overall reduced length of stay in the hospital, but also in the intensive care unit, thus, contributing to a significant cost reduction.

[Management of bleeding disorders in intensive care medicine]

Bleeding disorders are frequent in intensive care medicine, the most common form being acquired. Trauma, gastrointestinal bleeding, liver failure, hematologic malignancies, and adverse drug reactions play an important role. Moderate to severe hereditary bleeding disorders are usually known prior to the acute disease state, while mild hereditary forms may manifest for the first time in association with the acute stress condition. Generally, proper history taking and structured observation are decisive in order to conduct an appropriate diagnostic workup and initiate logical hemostatic management. One cannot always wait for laboratory results during continuous blood loss or conditions such as hypothermia and acidosis. In such cases, pathophysiological extrapolation of expected hemostatic disturbances is essential for timely hemostatic management.

Significance of advanced haemostasis investigation in recurrent, severe post-tonsillectomy bleeding

Objective:

To evaluate the significance of advanced post-operative haemostasis investigation in cases of recurrent, severe post-tonsillectomy bleeding.

Materials and methods:

Of the 120 patients treated at our tertiary centre between 2006 and 2010 due to post-tonsillectomy haemorrhage, 22 with recurrent, severe episodes of bleeding underwent further, advanced haemostasis investigation.

Results:

Underlying haemorrhagic disease was not diagnosed in any case. Isolated abnormal clotting factor levels were identified in two patients. Decreased fibrinogen concentration due to dilutional coagulopathy was found in nine cases (40.9 per cent).

Conclusion:

Recurrent, severe post-tonsillectomy haemorrhage is rarely related to undiagnosed haemostatic disorders. Thus, advanced haemostasis studies have little therapeutic relevance. However, repetitive post-tonsillectomy bleeding may be related to decreased fibrinogen levels due to dilutional coagulopathy. Therefore, fibrinogen concentration should be tested, and dilutional coagulopathy treated promptly.

Occurrence of coagulation factor deficiency in post-tonsillectomy hemorrhage

INTRODUCTION

Tonsillectomy is one of the most common surgical procedures in Otorhinolaryngology and approximately 500 tonsillectomies are performed annually at the University Hospital of Vienna. Substantial postoperative bleeding is observed in 1.8% of cases, which is comparable to frequencies of 2-4% reported in other studies. Currently, routine pre-surgical coagulation investigations to predict bleeding status do not include the analysis of individual coagulation factors.

MATERIAL AND METHODS

Within 2007 complete coagulation diagnostics were carried out in three patients presenting with recurrent (2-7 times) post-tonsillectomy hemorrhage but normal pre-surgical coagulation status parameters.

RESULTS

After the appearance of recurrent late bleeding, single factor diagnostic analysis revealed the causes to be factor XIIa deficiency, reduced factor XIIIa or von Willebrand disease. Recurrent late bleeding was stopped by the application of coagulation active plasma.

CONCLUSION

This study shows that, even if routine diagnostics show normal pre-surgical coagulation findings, the investigation of single factors in cases of post-surgical late bleeding may identify coagulation disorders allowing the application of tailored therapy. Including such analysis in pre-operative diagnostics could therefore significantly help to limit postoperative bleeding.

Platelet function testing in clinical diagnostics

Although the utility of platelet function testing is still under debate, the necessity to inhibit platelets in patients suffering from cardiovascular and cerebrovascular disease is undoubted and well proven. The wide variety of available platelet function tests often using different methodologies, the apparent lack of standardization, and finally the emerging evidence on the clinical value of platelet function testing are resulting in a considerable uncertainty in the clinical practice, how to deal with the issue of platelet function testing. Platelet function testing might not only yield clinical benefits for the patients but also economical advantages by identifying the right drug at the right dose for the right patient. This article intends to provide an overview of the current platelet function tests such as light transmittance aggregometry, whole blood impedance aggregometry, the PFA-1001 system, the VerifyNow2 system, flow cytometry, as well as other promising technologies like Plateletworks3, IMPACT-R4, PADA, thromboelastography, and the mean platelet component (MPC), briefly addressing strengths, weaknesses and clinical utility of these tests.

Hemostatic and hemorrhagic problems in neurosurgical patients

BACKGROUND

Abnormalities of the hemostasis can lead to hemorrhage, and on the other hand to thrombosis. Intracranial neoplasms, complex surgical procedures, and head injury have a specific impact on coagulation and fibrinolysis. Moreover, the number of neurosurgical patients on medication (which interferes with platelet function and/or the coagulation systems) has increased over the past years.

METHOD

The objective of this review is to recall common hemostatic disorders in neurosurgical patients on the basis of the "new concept of hemostasis". Therefore the pertinent literature was searched to provide a structured and up to date manuscript about hemostasis in Neurosurgery.

FINDINGS

According to recent scientific publications abnormalities of the coagulation system are discussed. Pathophysiological background and the rational for specific (cost)-effective perioperative hemostatic therapy is provided.

CONCLUSIONS

Perturbations of hemostasis can be multifactorial and maybe encountered in the daily practice of neurosurgery. Early diagnosis and specific treatment is the prerequisite for successful treatment and good patients outcome.

Diagnostic performance of the platelet function analyzer (PFA-100®) for the detection of disorders of primary haemostasis in patients with a bleeding history–a systematic review and meta-analysis

The Platelet Function Analyzer (PFA-100) is increasingly being used in the workup of patients with a bleeding diathesis. A profound knowledge of the possible diagnostic performance of this test is essential in order to make sound clinical decisions based on its results. It was the aim of this study to systematically review the published literature and provide valid estimates of the diagnostic performance of the PFA-100 for detecting disorders of primary haemostasis in newly presenting patients with a bleeding diathesis. A comprehensive literature search was performed for studies published between January 1994 and February 2006. Studies were eligible for the systematic review if they provided data supposed to be applicable to the determination of the diagnostic performance of the PFA-100. Furthermore, they were included in a meta-analysis if study reporting allowed calculation of sensitivity and specificity and if study quality ensured minimized biases of these estimates for the described clinical setting. Pooled weighted sensitivity, specificity and diagnostic odds ratio were calculated applying random effects modelling and constructing summary operator characteristic curves. This was done separately for the available test modifications using either collagen/epinephrine (PFA-EPI) or collagen/adenosine-diphosphate (PFA-ADP) for platelet activation. Thirty-six articles were included in the systematic review. Six studies met our eligibility criteria for a meta-analysis. The major reason for exclusion from the meta-analysis was a case-control design. A total of 1486 and 1259 patients were included in the meta-analysis of the diagnostic performance of the PFA-EPI and PFA-ADP, respectively. Pooled weighted sensitivity and specificity of the PFA-EPI/PFA-ADP in detecting a disorder of primary haemostasis were: 82.5/66.9% (95%-confidence interval (95%-CI): 76.0-88.9%/57.9-75.9%), and 88.7/85.5% (95%-CI: 84.3-93.1%/82.0-89.1%). 83/75% of patients with a positive PFA-EPI/PFA-ADP result do have a disorder of primary haemostasis whereas 88/79% with a negative PFA-EPI/PFA-ADP result do not. The PFA-EPI appeared to have a higher sensitivity and better predictive values than the PFA-ADP in detecting disorders of primary haemostasis, although a rigorous gold standard definition for a disorder of primary haemostasis, particularly for platelet disorders, was not applied in most studies. The majority of the studies lacked important requirements for quality and reporting, precluding a more precise and definitive characterization of the clinical utility of the PFA-100. This emphasizes the need for an evidence-based critical appraisal of diagnostic studies in haemostasis research in order to promote the conducting of studies that produce clinically relevant results.

Tonsillectomy in children

INTRODUCTION

Tonsillectomy is one of the most frequently performed surgical interventions in children. In the following, indications, preoperative evaluation, surgical techniques and postoperative complications will be discussed.

METHODS

Literature search in PubMed (National Library of Medicine) focusing on publications in German or English up to June 2008.

RESULTS

Indications are selected infectious diseases, upper airway obstruction for example due to tonsillar hypertrophy, and a suspected malignancy. Viral infections of the tonsils without upper airway obstruction are not an indication for surgery; in the case of acute bacterial tonsillitis, tonsillectomy is no longer recommended. In recurrent tonsillitis, tonsillectomy is only effective in specific and narrow indications. The indication for tonsillectomy in sleep-disordered breathing due to adenotonsillar hypertrophy has to be based on clinical assessment, medical history, and a sleep history. The most relevant risk factors are obstructive sleep apnea and coagulation disorders. A standardized history regarding hemostasis and bleeding is mandatory, and is superior to routine coagulation tests. Postoperative bleeding is still the most relevant complication of tonsillectomy and is always an emergency situation.

CONCLUSION

Tonsillectomy is one of the most frequently performed interventions in children but should be considered with care, as life-threatening complications can occur.

[Tonsillectomy in children: preoperative evaluation of risk factors]

Tonsillectomy is one of the most frequently performed surgical procedures in children and is associated with a relatively high risk of postoperative complications. The question often arises whether paediatric obstructive sleep apnoea should be diagnosed with preoperative sleep testing and whether preoperative coagulation tests should be performed in every child undergoing tonsillectomy. In order to answer these questions, the relevant German and English literature was analysed. Adenotonsillectomy in childhood usually resolves the underlying sleep-related breathing disorder. Nevertheless, especially in children with clinical risk factors such as severe sleep apnoea, obesity or craniofacial malformation, respiratory complications should be expected in the postoperative phase. Routine sleep tests prior to tonsillectomy are neither necessary nor practical for preoperative evaluation. Inherited coagulation disorders have only a limited effect on the occurrence of postoperative bleeding and the predictive value of routine coagulation tests is limited. As long as a thorough clinical history is negative, routine coagulation tests are not helpful or necessary prior to tonsillectomy in children.

Prevalence of Platelet Dysfunction and Abnormal Coagulation: Results of a Population-Based Study

The prevalence of impairments in the hemostatic process is unknown in acutely ill people. Data on hemostasis (PFA 100®) and the coagulation cascade of 1015 people are presented here, establishing a cohort of unselected emergency patients in a population-based approach. A high prevalence of reduced platelet function (38%) was found, which was more frequent than expected. In contrast, there was a lower prevalence (20%) of abnormal plasmatic coagulation, which was almost always explained by medication, whereas medication could not predict abnormal platelet function. Moreover, a history of disproportionate bleeding did not correlate well with abnormal platelet or coagulation factor function and could not substitute for a screening in this setting. The effect of acetylsalicylic acid (ASA) on PFA-closure time was frequently missing (34%), indicating a considerable prevalence of ASA nonresponse among the study population. These data should be applicable in similar settings. The high prevalence of unexpectedly abnormal platelet function in acute illness as well as the high prevalence of possible ASA nonresponders suggests a functional platelet assay to be effective in screening certain subpopulations of emergency patients.

Point-of-care platelet function tests: detection of platelet inhibition induced by nonopioid analgesic drugs

Detection of platelet inhibition is of clinical relevance in the preinterventional risk-benefit assessment in chronic low-back-pain patients scheduled for invasive pain therapy. We evaluated the sensitivity of various point-of-care platelet function tests for the detection of platelet inhibition induced by nonopioid analgesic drugs. After Institutional Review Board approval and informed consent, citrated whole blood from 40 patients with chronic unspecific low back pain was investigated before and 30 min after intravenous infusion of the study medication consisting of diclofenac 75 mg (plus orphenadrin 30 mg; Neodolpasse; Fresenius Kabi Austria GmbH, Austria), parecoxib 40 mg (Dynastat; Pharmacia Europe EEIG, UK), paracetamol 1 g (Perfalgan; Bieffe Medital S.P.A., Italy), or normal saline in a randomized, cross-over, double-blinded, placebo-controlled study. Platelet function was assessed using the PFA-100 platelet function analyzer and thromboelastometry, as well as impedance aggregometry (in the last 17 patients recruited after it became commercially available). Sensitivity for detecting diclofenac-induced platelet inhibition was 85% for the PFA-100 using epinephrine as agonist and 94% for arachidonic acid-induced impedance aggregometry. ADP-induced platelet function tests, as well as cytochalasin D-modified thromboelastometry were unreliable. All tests had a low incidence of false-positive test results after normal saline. Paracetamol and parecoxib had no significant platelet inhibiting effect. The PFA-100 using epinephrine as agonist and arachidonic acid-induced impedance aggregometry are recommended for the detection of cyclooxygenase-I-inhibiting effects of nonsteroidal anti-inflammatory drugs such as diclofenac. Our findings confirm that a single rescue dose of paracetamol and parecoxib has no antiplatelet effect.