Stephen O. Bader

Diagnosis of Perioperative Coagulopathy—Plasma versus Whole Blood Testing

In the course of laboratory-guidedhemostatic therapy for patients with major bleeding, the timing ofdiagnosis may affect not only the timing of hemostatic inter-vention but also the efficacy of such intervention, becausecoagulation status dynamically changes (often for the worse) overtime (Fig 1). Alternatively, the ratio-based transfusion approach(eg, a 1:1 ratio of plasma to red blood cells [RBCs]) has been usedat major trauma centers in the United States.

Novel approaches in management of perioperative coagulopathy.

Purpose of review The recent advances in hemostatic monitoring, and discussion of the clinical implications of hemostatic therapies based on different blood components and factor concentrates. Recent findings Implementing suitable laboratory tests and transfusion protocols is highly recommended because the laboratory test guided, protocol-driven transfusion approach reduces blood component utilization, and possibly leads to improved outcomes. Timely assessment of coagulation has been difficult using conventional coagulation tests, but thrombocytopenia, fibrin polymerization defects, and fibrinolysis can be quickly assessed on thromboelastometry. The latter testing can be applied to guide the dosing of fibrinogen and prothrombin complex concentrate, which are selectively used to correct fibrinogen deficiency, and improve thrombin generation in acquired coagulopathy. These therapeutic approaches are novel, and potentially effective in reducing the exposure to allogeneic components (e.g., plasma and platelets) and side-effects of transfusion. Although the accessibility of different therapies among different countries, tranexamic acid is widely available, and is an effective blood conservation measure with a good safety profile in various surgical settings. Summary Our understanding of perioperative coagulopathy, diagnostic tools, and therapeutic approaches has evolved in recent years. Additional multidisciplinary efforts are required to understand the optimal combinations, cost-effectiveness, and safety profiles of allogeneic components, and available factor concentrates.

Effects of recombinant activated factor VII on thrombin-mediated feedback activation of coagulation.

Thrombin is a key hemostatic enzyme, which propagates its own generation by activating factors V, VIII, and XI. Sustained thrombin generation also activates thrombin-activatable fibrinolysis inhibitor (TAFI), which stabilizes fibrin clot against fibrinolysis. Recombinant activated factor VII (rFVIIa) is considered a novel hemostatic intervention for refractory bleeding, but rebleeding episodes related to fibrinolysis still occur. The present study aimed to investigate the antifibrinolytic effects of rFVIIa in relation to thrombin generation. Using thrombelastography, the effects of rFVIIa on thrombin-activated fibrin formation and on fibrinolysis induced by tissue plasminogen activator were evaluated in various factor-deficient plasma samples. A Thrombinoscope was used to quantitate thrombin generation. Thrombin increased antifibrinolytic activity in a concentration-dependent manner as demonstrated by a longer clot lysis time. In plasma deficient in factors V, VIII, IX, X, or XI, clot lysis occurred early (< 20 min), and rFVIIa addition had minimal effect, except for improved antifibrinolytic effect in factor-XI-deficient plasma. A normal clot lysis time was observed in factor-XIII-deficient or dual antithrombin/factor-VIII-deficient plasma. Inhibition of TAFI increased the rate of fibrinolysis. Thrombin generation was delayed or decreased in single factor-deficient plasma except for factor XIII deficiency. After rFVIIa addition, the peak thrombin generation reached over 100 nmol/l in factor-XI-deficient plasma, but not in plasma deficient in factors V, VIII, IX, or X. Thrombin generation and subsequent activation of TAFI were important for clot stability. We conclude that rFVIIa therapy does not compensate for increased susceptibility to fibrinolysis due to lack of factor(s) necessary for the formation of tenase and prothrombinase.

An evidence-based approach to medication preparation for the surgical patient at risk for latex allergy: is it time to stop being stopper poppers?

The prevalence of latex allergy is increasing in surgical patient populations. Avoidance of exposure to the allergen is essential to minimizing perioperative complications in patients suspected to be at risk. Natural rubber latex has historically been ubiquitous in medical devices containing rubber. In 1998, the Food and Drug Administration (FDA) began to require the labeling of medical devices made from natural rubber latex; since that time substantial progress has been made in identifying latex-free alternatives. However, the rubber stoppers commonly found in pharmaceutical vial closures are exempt from FDA labeling requirements. Examination of the clinical and basic science literature regarding pharmaceutical vial closures supports limiting the rubber stopper to a single needle puncture as a safer practice, with the caveat that no strategy exists for the complete elimination of risk as long as stoppers made from natural rubber latex are used in pharmaceutical vials intended for human use.

Pneumoscrotum as the presenting symptom of pneumothorax and pneumoperitoneum after jet ventilation.

A 46-YR-OLD male presented with pneumoscrotum in postoperative recovery following dilation of tracheal stenosis using carbon dioxide laser and jet ventilation through a catheter. The patient developed stenosis after closure of a tracheostomy, which occurred during recovery from trauma involving vertebral, rib, and pelvic fractures as well as bilateral pneumothoraces. The patient was initially jet-ventilated through a 14 French catheter. After sufficient dilation, this was replaced with a 5.0-mm laser-shielded endotracheal tube, and the patient was ventilated uneventfully for the remainder of the case. The patient was extubated without incident and was recovering comfortably when he complained of scrotal fullness and, in addition to the pneumoscrotum, was found to have a large right pneumothorax and pneumoperitoneum. A chest tube was placed and, 5 days later, the pneumothorax and pneumoscrotum had resolved. Since 1960, there have been 11 case reports of pneumoscrotum caused by pneumothorax. Pneumoscrotum has a diverse differential diagnosis. Underlying causes can be categorized by three routes of air entry into the scrotum: 1) dissection of subcutaneous or retroperitoneal air into dartos lining of the scrotal wall; 2) movement of intraperitoneal air through a patent processus vaginalis; and 3) local gas production or introduction because of infection or injection. The cause in this case was clearly localized high airway pressure from jet ventilation transmitted to the scrotum by the first or second routes above. In this case, the only presenting symptom of life-threatening pathology was the pneumoscrotum. Although rare in the perioperative setting, the diagnostic implications should be recognized when discovered, and precipitate a prompt search for the cause.

Risk of latex allergy from pharmaceutical vial closures.

tively brief preoperative abstinence from smoking (less than 8 weeks) does not increase pulmonary risk compared with continued smoking. Indeed, we are not aware of any individual study that has found a statistically significant increase in pulmonary complications with brief preoperative abstinence, including the two initial studies by Warner et al. that were interpreted by some authors as raising concerns. The conjectured mechanism responsible for increased risk is a transient increase in cough and sputum production after smoking cessation. However, there is no evidence that cough and sputum production actually increase after smoking cessation, either in an ambulatory population or specifically in anesthetized patients. It does seem clear that more prolonged abstinence from smoking is necessary to reduce the risk of pulmonary morbidity because it takes several weeks for the lungs to recover from the effects of smoking. Thus, although more data would be welcome, we do not believe that there is any evidence to support the possibility that short-term smoking cessation increases pulmonary complications. It is very likely that the longer the duration of abstinence the better in terms of reducing risk of pulmonary and other complications. However, given the power of the teachable moment and the long-term benefits to health, anesthesiologists and others should seize any opportunity at any time to help their patients quit smoking, without fearing that brief preoperative abstinence could worsen outcome. The American Society of Anesthesiologists provides several tools to do so.*