Alterations in coagulation following major liver resection

The international normalised ratio is frequently raised in patients who have undergone major liver resection, and is assumed to represent a potential bleeding risk. However, these patients have an increased risk of venous thromboembolic events, despite conventional coagulation tests indicating hypocoagulability. This prospective, observational study of patients undergoing major hepatic resection analysed the serial changes in coagulation in the early postoperative period. Thrombin generation parameters and viscoelastic tests of coagulation (thromboelastometry) remained within normal ranges throughout the study period. Levels of the procoagulant factors II, V, VII and X initially fell, but V and X returned to or exceeded normal range by postoperative day five. Levels of factor VIII and Von Willebrand factor were significantly elevated from postoperative day one (p < 0.01). Levels of the anticoagulants, protein C and antithrombin remained significantly depressed on postoperative day five (p = 0.01). Overall, the imbalance between pro- and anticoagulant factors suggested a prothrombotic environment in the early postoperative period.

Patient blood management to reduce surgical risk

BACKGROUND

Preoperative anaemia and perioperative blood transfusion are both identifiable and preventable surgical risks. Patient blood management is a multimodal approach to address this issue. It focuses on three pillars of care: the detection and treatment of preoperative anaemia; the reduction of perioperative blood loss; and harnessing and optimizing the patient-specific physiological reserve of anaemia, including restrictive haemoglobin transfusion triggers. This article reviews why patient blood management is needed and strategies for its incorporation into surgical pathways.

METHODS

Studies investigating the three pillars of patient blood management were identified using PubMed, focusing on recent evidence-based guidance for perioperative management.

RESULTS

Anaemia is common in surgical practice. Both anaemia and blood transfusion are independently associated with adverse outcomes. Functional iron deficiency (iron restriction due to increased levels of hepcidin) is the most common cause of preoperative anaemia, and should be treated with intravenous iron. Intraoperative blood loss can be reduced with antifibrinolytic drugs such as tranexamic acid, and cell salvage should be used. A restrictive transfusion practice should be the standard of care after surgery.

CONCLUSION

The significance of preoperative anaemia appears underappreciated, and its detection should lead to routine investigation and treatment before elective surgery. The risks of unnecessary blood transfusion are increasingly being recognized. Strategic adoption of patient blood management in surgical practice is recommended, and will reduce costs and improve outcomes in surgery.

Risk of bleeding and adverse outcomes predicted by thromboelastography platelet mapping in patients taking clopidogrel within 7 days of non-cardiac surgery

BACKGROUND

Patients often fail to stop clopidogrel appropriately before non-cardiac surgery. Thromboelastography platelet mapping (TEG-PM) can be used to measure the percentage adenosine 5'-diphosphate platelet receptor inhibition (ADP-PRI) by clopidogrel in these patients.

METHODS

This prospective case-control study investigated the risk of bleeding in patients who had taken clopidogrel within 7 days of scheduled operation. Patients underwent TEG-PM to stratify their bleeding risk. Low-risk (ADP-PRI below 30 per cent) and urgent priority high-risk (ADP-PRI 30 per cent or more) patients proceeded to surgery. The outcomes of these patients were compared with those of matched controls. Regression analysis, with bootstrapping validation, was used to identify independent risk factors for bleeding and an optimal cut-off value of ADP-PRI for cancellation of surgery.

RESULTS

From May 2008 to October 2013, 182 patients failed to discontinue clopidogrel. No correlation was observed between duration of clopidogrel omission and percentage ADP-PRI; 112 low-risk and 19 high-risk patients proceeded to surgery. High-risk patients had significantly greater intraoperative packed red blood cell (PRBC) transfusion in comparison with their matched controls, and a strong positive correlation between percentage ADP-PRI and units of intraoperative PRBCs transfused (r = 0·749, 95 per cent confidence interval (c.i.) 0·410 to 0·940; P < 0·001). Percentage ADP-PRI was the only independent risk factor for intraoperative PRBC transfusion (odds ratio 1·07, 95 per cent c.i. 1·02 to 1·13; P = 0·005).

CONCLUSION

An objective measure of platelet inhibition with TEG-PM, using an ADP-PRI cut-off of 34 per cent, can be used to prevent unnecessary cancellations, while minimizing patient risk.

Epidural anaesthesia and analgesia for liver resection

Although epidural analgesia is routinely used in many institutions for patients undergoing hepatic resection, there are unresolved issues regarding its safety and efficacy in this setting. We performed a review of papers published in the area of anaesthesia and analgesia for liver resection surgery and selected four areas of current controversy for the focus of this review: the safety of epidural catheters with respect to postoperative coagulopathy, a common feature of this type of surgery; analgesic efficacy; associated peri-operative fluid administration; and the role of epidural analgesia in enhanced recovery protocols. In all four areas, issues are raised that question whether epidural anaesthesia is always the best choice for these patients. Unfortunately, the evidence available is insufficient to provide definitive answers, and it is clear that there are a number of areas of controversy that would benefit from high-quality clinical trials.

The impact of aprotinin on renal function after liver transplantation: an analysis of 1,043 patients

Renal dysfunction is frequently seen after orthotopic liver transplantation (OLT). Aprotinin is an antifibrinolytic drug which reduces blood loss during OLT. Recent studies in cardiac surgery suggested a higher risk of postoperative renal complications when aprotinin is used. The impact of aprotinin on renal function after OLT, however, is unknown. In 1,043 adults undergoing OLT, we compared postoperative renal function in patients who received aprotinin (n = 653) or not (n = 390). Using propensity score stratification (C-index 0.82) and multivariate regression analysis, aprotinin was identified as a risk factor for severe renal dysfunction within the first week, defined as increase in serum creatinine by >or= 100% (OR = 1.97, 95% CI = 1.14-3.39; p = 0.02). No differences in renal function were noted at 30 and 365 days postoperatively. Moreover, no significant differences were found in the need for renal replacement therapy (OR = 1.52, 95% CI = 0.94-2.46; p = 0.11) or in 1-year patient survival rate (OR = 1.14, 95% CI = 0.73-1.77; p = 0.64) in patients who received aprotinin or not. In conclusion, aprotinin is associated with a higher risk of transient renal dysfunction in the first week after OLT, but not with a higher need for postoperative renal replacement therapy or an increased risk of mortality.

Use of the platelet function analyser (PFA-100) to quantify the effect of low dose aspirin in patients with ischaemic heart disease

Continuing aspirin up until surgery in cardiac surgical patients may increase peri-operative blood loss. It is possible that there is a subset of patients particularly sensitive to aspirin. The platelet function analyser (PFA-100) can demonstrate the antiplatelet effect of aspirin. This study was designed to assess the effect of daily 75 mg aspirin on platelet function, as measured by the PFA-100, in 92 patients with ischaemic heart disease. Patients were classified into three groups according to their PFA-100 results; aspirin hyper-responders (16%), aspirin normal responders (33%) and aspirin non-responders (51%). The PFA-100 has potential as a screening tool to identify patients who are either hyper-responsive or resistant to aspirin. Pre-operative PFA-100 screening to isolate aspirin hyper-responders could enable the vast majority of patients to continue with aspirin therapy pre-operatively, avoiding the risks of stopping treatment.

The effects of balanced versus saline-based hetastarch and crystalloid solutions on acid-base and electrolyte status and gastric mucosal perfusion in elderly surgical patients

The IV administration of sodium chloride solutions may produce a metabolic acidosis and gastrointestinal dysfunction. We designed this trial to determine whether, in elderly surgical patients, crystalloid and colloid solutions with a more physiologically balanced electrolyte formulation, such as Hartmann's solution and Hextend, can provide a superior metabolic environment and improved indices of organ perfusion when compared with saline-based fluids. Forty-seven elderly patients undergoing major surgery were randomly allocated to one of two study groups. Patients in the Balanced Fluid group received an intraoperative fluid regimen that consisted of Hartmann's solution and 6% hetastarch in balanced electrolyte and glucose injection (Hextend). Patients in the Saline group were given 0.9% sodium chloride solution and 6% hetastarch in 0.9% sodium chloride solution (Hespan). Biochemical indices and acid-base balance were determined. Gastric tonometry was used as a reflection of splanchnic perfusion. Postoperative chloride levels demonstrated a larger increase in the Saline group than the Balanced Fluid group (9.8 vs 3.3 mmol/L, P = 0.0001). Postoperative standard base excess showed a larger decline in the Saline group than the Balanced Fluid group (-5.5 vs -0.9 mmol/L, P = 0.0001). Two-thirds of patients in the Saline group, but none in the Balanced Fluid group, developed postoperative hyperchloremic metabolic acidosis (P = 0.0001). Gastric tonometry indicated a larger increase in the CO2 gap during surgery in the Saline group compared with the Balanced Fluid group (1.7 vs 0.9 kPa, P = 0.0394). In this study, the use of balanced crystalloid and colloid solutions in elderly surgical patients prevented the development of hyperchloremic metabolic acidosis and resulted in improved gastric mucosal perfusion when compared with saline-based solutions.

IMPLICATIONS

This prospective, randomized, blinded trial showed that, in elderly surgical patients, the use of balanced IV solutions can prevent the development of hyperchloremic metabolic acidosis and provide better gastric mucosal perfusion compared with saline-based fluids.

Reducing red blood cell transfusion in elective surgical patients: the role of audit and practice guidelines

In 1996, we prospectively audited peri-operative transfusion practice in elective surgical patients over a 3-month period. Two-unit transfusions represented 60% of all transfusions. Haemoglobin was measured infrequently prior to transfusion and the main 'trigger' for transfusion was an estimated blood loss in excess of 500 ml. Transfusion guidelines that required the haemoglobin level to be measured immediately before transfusion were introduced. The audit was repeated in 1998; transfusion 'triggers' and the number of transfusions for the two periods were compared. In the second audit, the total number of transfusions decreased by 43%. The mean estimated blood loss associated with a 2-unit transfusion had increased from 608 (373) ml to 1320 (644) ml (p < 0.01) and the estimated haemoglobin concentration after transfusion had decreased from 12.4 (1.8) g.dl-1 to 9.9 (2.4) g.dl-1 (p < 0.01). These results suggest that transfusion guidelines can have a significant impact on clinical practice.

Anticoagulant-induced pseudothrombocytopenia in a patient presenting for coronary artery bypass grafting

A 73-yr-old man with severe ischaemic heart disease presented for coronary artery bypass grafting. His preoperative platelet count, obtained from an ethylene diamine tetraacetic acid (EDTA) sampling bottle, was 61 x 10(9) litre-1, but he had no history of bleeding problems. Previous platelet counts demonstrated results ranging from 16 x 10(9) litre-1 to 254 x 10(9) litre-1 with variable degrees of in vitro platelet clumping. Preoperative thrombelastography reflected a normal coagulation profile. The laboratory findings and the absence of a history of haemorrhagic complications suggested a diagnosis of EDTA-dependent pseudothrombocytopenia. We present the perioperative implications of this in vitro phenomenon and methods of detecting the functional and numerical integrity of circulating platelets.

Use of heparinase modified thrombelastography in liver transplantation

Severe coagulopathies can occur during liver transplantation, particularly after reperfusion of the grafted liver. Heparin release has been proposed as one of the factors contributing to this coagulopathy. We have analysed the thrombelastograph (TEG) traces of 55 patients after reperfusion using native and heparinase-treated samples. In almost all cases an abnormal native TEG was improved in vitro by heparinase, demonstrating the presence of heparin or a heparin-like substance. The heparinase-modified TEG allowed assessment of the underlying coagulation status, providing a rational guide to blood component replacement or treatment of fibrinolysis.

Thrombelastography reveals two causes of haemorrhage in HELLP syndrome

We describe the use of thrombelastography in HELLP syndrome (Haemolysis, Elevated Liver Enzymes, Low Platelets). It differentiated between two possible causes of significant haemorrhage and revealed an accompanying underlying fibrinolysis. This allowed specific therapy to be directed at both abnormalities and, we believe, helped prevent this patient from undergoing radical surgery to curb blood loss.

Hypomagnesaemia, cardiac arrhythmias and orthotopic liver transplantation

Two patients who underwent orthotopic liver transplantation and developed peroperative cardiac arrhythmias are presented. In one, the arrhythmias were refractory to treatment with anti-arrhythmic drug therapy until serum magnesium levels were restored to normal. The other patient had a low pre-operative serum magnesium level and developed atrial fibrillation on induction of, and during, anaesthesia. Patients undergoing orthotopic liver transplantation may be a group especially predisposed to hypomagnesaemia. The importance of monitoring serum magnesium levels in such patients who develop peroperative cardiac arrhythmias is emphasised.

Pulmonary platelet aggregates: possible cause of sudden peroperative death in adults undergoing liver transplantation

AIMS

To determine if massive pulmonary platelet thromboembolism is a common cause of peroperative death following liver transplantation; and to compare the incidence of this event with patients dying after non-transplantation procedures.

METHODS

Necropsy tissues from all patients dying within 10 days of operation during the past three and a half years were studied (six liver transplantations and 13 unrelated operations). Haematoxylin and eosin stained sections of all tissues were examined. Additional sections of lung tissue were immunostained for constituents of thrombus (fibrin and platelets).

RESULTS

At necropsy the lungs from all six liver transplant recipients were heavy with a rubbery texture and little oedema fluid. Those from non-transplantation patients appeared normal or very oedematous. Microscopic examination showed that there were numerous platelet aggregates occluding pulmonary capillaries in all six transplant recipients, but in only three of the non-transplant patients. These thrombi were numerous in patients dying during surgery and the number was underestimated in routine sections because of the surrounding capillary congestion. Detection was improved by immunostaining for platelets with factor XIIIA and platelet glyco-protein IIIa.

CONCLUSIONS

Massive platelet thromboembolism is a likely cause of death in patients dying unexpectedly following recent liver transplantation. Non-transplantation patients dying during surgery who show similar appearances usually have conditions known to have a high risk of thrombosis or embolism (cement hypotension syndrome and disseminated intravascular coagulation). The cause of this extensive platelet activation in liver transplant recipients is uncertain and may be multifactorial. The unusual rubbery consistency of the lungs on macroscopic examination could alert the pathologist to the underlying condition. Immunostaining for platelets improves the detection microscopically.

The intra-operative use of trasylol (aprotinin) in liver transplantation

Aprotinin has been reported to reduce blood loss in difficult cases requiring cardiopulmonary bypass surgery and more recently in liver transplantation. Over a 9-month period we compared the effects of an intra-operative infusion of aprotinin on transfusion requirements and coagulation profiles in 12 patients undergoing liver transplantation for end-stage cirrhosis with an equal number of consecutive transplants in patients with similar pathology who did not receive aprotinin. Transfusion of blood and blood products was reduced to one-third in the aprotinin-treated group. Operative time was also significantly reduced, as was ICU stay post-operatively. Aprotinin profoundly inhibits fibrinolysis and this is likely to be the major effect by which blood loss is reduced. Thromboelastography revealed severe fibrinolytic changes in the anhepatic stage in 4 of 6 controlled patients; this accelerated in 3 following reperfusion of the new graft. By contrast, only 1 patient of 12 in the aprotinin-treated group showed fibrinolytic activity in the anhepatic period, and none showed evidence of fibrinolysis following reperfusion of the new graft.

Decreasing post-succinylcholine myalgia in outpatients

The effectiveness of four pretreatment regimens in decreasing succinylcholine-induced myalgias was studied in healthy outpatients undergoing general anaesthesia for ambulatory surgery. Four hundred and forty adult females were randomly assigned to one of four pretreatment groups. Three hundred and ninety-five patients completed the study. One of the following pretreatments was given prior to injection of 1.5 mg X kg-1 of succinylcholine: normal saline IV three minutes and again immediately prior to succinylcholine; 0.06 mg X kg-1 d-tubo-curarine (dTc) IV three minutes prior and normal saline IV immediately prior; normal saline IV three minutes prior and 1.5 mg X kg-1 lidocaine IV immediately prior; 0.06 mg X kg-1 dTc IV three minutes prior and 1.5 mg X kg-1 lidocaine IV immediately prior. Fasciculations after injection of succinylcholine were observed and recorded. Patients were contacted by telephone 40-48 hours postoperatively and questioned about the presence of muscle pains. These pains, if present, were graded either mild or moderate to severe. The patients in the two dTc-containing groups exhibited less fasciculations than patients in the other two experimental groups. The dTc-lidocaine group had a lower incidence of moderate to severe fasciculations than in any of the other three groups. Patients in the dTc, lidocaine, and dTc-lidocaine experimental groups reported a higher incidence of absence of muscle pain and a lower incidence of moderate-severe pain than did patients in the saline group. The dTc-lidocaine group had more patients without myalgia and less patients with moderate to severe myalgias than any of the other groups.(ABSTRACT TRUNCATED AT 250 WORDS)