Pharmacological strategies to decrease excessive blood loss in cardiac surgery: a meta-analysis of clinically relevant endpoints

Coagulation Disorders and Blood Product Use in Patients Undergoing Thoracoabdominal Aortic Aneurysm Repair

Repair of thoracoabdominal aortic aneurysms (TAAA) is associated with major blood loss, often exceeding the patient's intravascular volume, and complex intraoperative and postoperative coagulopathies necessitating large-volume transfusion of blood products. Abnormalities sufficient to cause thrombocytopenia or clinically important prolongation of clotting parameters are rarely present before surgery in elective aneurysms but are more common with ruptured aneurysms. The finding of intraoperative and postoperative deficiencies of clotting factors, along with thrombin generation and activation of the thrombolytic system, is reflective of massive blood losses, visceral ischemia, and massive transfusions. An aggressive strategy of transfusion of blood products is critical to the prevention of clinically significant coagulopathy during surgery. Adjuncts to reduce blood losses and blood product use include low-dose aprotinin or epsilon -aminocaproic acid, intraoperative blood salvaging, and acute normovolemic hemodilution. In TAAA repair, an average blood loss of 5000 to 6000 mL and average transfusion of allogeneic blood products of 50 to 60 U are to be anticipated.

Antifibrinolytic agents in cardiac surgery: Current controversies

Antifibrinolytic agents play a prominent role in adult cardiac surgery. This article is a review of the modern published experience of antifibrinolytic agent use in adult cardiac surgery. The use of tranexamic acid, epsilon-aminocaproic acid, and aprotinin is examined during primary cardiac surgery, deep hypothermic circulatory arrest, reoperative cardiac surgery, and off-pump coronary artery bypass surgery. In addition, the issues of vein graft patency and hypersensitivity reaction in the presence of antifibrinolytic agents are examined.

Preoperative use of enoxaparin increases the risk of postoperative bleeding and re-exploration in cardiac surgery patients

OBJECTIVE

The purpose of this study was to investigate if the preoperative use of new platelet inhibitors and low-molecular-weight heparins may contribute to bleeding after cardiac surgery.

DESIGN

Retrospective data review.

SETTING

University teaching hospital.

PARTICIPANTS

One hundred eleven patients divided in 5 groups.

INTERVENTIONS

Patients were grouped according to preoperative antithrombotic regimen: group 1, control, no agents (n=55); group 2, clopidogrel (n=9); group 3, enoxaparin (n=17); group 4, any GP IIb/IIIa inhibitor (n=14); and group 5, any drug combination (n=15). Data included cumulative mediastinal chest tube drainage, allogeneic blood transfusions, total blood donor exposures, and re-exploration.

MEASUREMENTS AND MAIN RESULTS

Use of any drug (groups 2-5) resulted in greater total blood transfusions and donor exposure (p=0.0003) than control, especially red cells (p=0.002) and platelets (p=0.006). A greater percentage of patients on enoxaparin required mediastinal re-exploration for nonsurgical bleeding versus control (3/17 v 0/55, p=0.001). The use of enoxaparin was associated with significantly higher chest tube output after the first 24 hours postoperatively (p=0.048).

CONCLUSION

Newer antithrombotic agents were associated with greater transfusion rates and total donor exposures. Enoxaparin use was associated with greater overall blood loss and with higher incidence of mediastinal re-exploration. The relative risk-benefit ratio of reduced periprocedure morbidity versus increased bleeding complications has yet to be determined.

Activated recombinant factor VII in cardiac surgery

PURPOSE OF REVIEW

Severe bleeding after cardiac surgery is a potential problem that poses major risks and challenges. Severe bleeding after cardiac surgery still occurs despite many pharmacological approaches to decrease bleeding and reduce transfusion requirements. Activated recombinant factor VII may be a therapy that is potentially useful in the management of refractory bleeding after cardiac surgery and in other postoperative bleeding states.

RECENT FINDINGS

Several small, uncontrolled case series have suggested that activated recombinant factor VII may be useful in the management of some patients with intractable bleeding after cardiopulmonary bypass in both pediatric and adult populations. Blood loss or transfusion requirements have been reported to be substantially reduced in some patients who receive activated recombinant factor VII perioperatively. However, these reports have not established the optimal dosing or ideal timing of the administration of activated recombinant factor VII, or determined the frequency of serious adverse events related to its use.

SUMMARY

Current reports summarized in this review suggest that activated recombinant factor VII may be a promising agent in the management of uncontrolled bleeding after cardiopulmonary bypass, but additional randomized, placebo-controlled trials are needed to support this use.

Antifibrinolytics in orthotopic liver transplantation: current status and controversies

This article reviews the current status and controversies of the 3 commonly used antifibrinolytics-epsilon-aminocaproic acid, tranexamic acid and aprotinin-during liver transplantation. There is no general consensus on how, when or which antifibrinolytics should be used in liver transplantation. Although these drugs appear to reduce blood loss and decrease transfusion requirements during liver transplantation, their use is not supported uniformly in clinical trials. Aprotinin has been studied more extensively in clinical trials and appear to offer more advantages compared to two other antifibrinolytics. Because of the diverse population of liver transplant recipients and the potential adverse effects of antifibrinolytics, especially life-threatening thromboembolism, careful patient selection and close monitoring is prudent. Further studies addressing the risks and benefits of antifibrinolytics in the setting of liver transplantation are warranted.

Reducing allogeneic transfusion in cardiac surgery: a randomized double-blind placebo-controlled trial of antifibrinolytic therapies used in addition to intra-operative cell salvage

BACKGROUND

The transfusion of allogeneic red blood cells and allogeneic coagulation products is associated with risk to the patient and the depletion of an increasingly scarce resource. This prospective, randomized, double-blind, placebo-controlled trial investigated practices to avoid transfusion in patients undergoing first-time cardiac surgery.

METHODS

Patients were randomized to one of three treatment groups: an aprotinin group, a tranexamic acid group, and a control group receiving normal saline. Intra-operative cell salvage was used for all patients. The primary outcomes were the number of patients exposed to allogeneic red blood cells, allogeneic coagulation products or any allogeneic transfusion (allogeneic red blood cells and/or allogeneic coagulation products).

RESULTS

Patients were 2.5 times more likely to receive any allogeneic transfusion in the tranexamic group than in the aprotinin group (21 patients out of 60 compared with nine out of 60, respectively). The relative risk of any allogeneic transfusion comparing aprotinin with tranexamic acid was 0.43 (95% confidence interval 0.21-0.86; P=0.019). Patients in the control group were four times more likely to receive any allogeneic transfusion when compared with the aprotinin group (37 patients out of 60 compared with nine out of 60, respectively). The relative risk of any allogeneic transfusion comparing aprotinin with control was 0.24 (95% confidence interval 0.13-0.46; P<0.001).

CONCLUSIONS

When used in addition to intra-operative cell salvage, aprotinin is the most efficacious pharmacological therapy for reducing patient exposure to any allogeneic transfusion during first-time cardiac surgery.

Perioperative systemic haemostatic agents

Skilful surgery combined with blood-saving methods and careful management of blood coagulation will all help reduce unnecessary blood loss and transfusion requirements. Excessive surgical bleeding causes hypovolaemia, haemodynamic instability, anaemia and reduced oxygen delivery to tissues, with a subsequent increase in postoperative morbidity and mortality. The role of anaesthetists in managing surgical blood loss has increased greatly in the last decade. Position of the patient during surgery and the provision of a hypotensive anaesthetic regimen were once considered the most important contributions of the anaesthetist to decreasing blood loss. Now, several pharmacological haemostatic agents are being used by anaesthetists as blood-saving agents. After a brief discussion of the physiology of haemostasis, this article will review the evidence for the role of such agents in reducing perioperative blood loss and transfusion requirements.

Tranexamic acid in control of primary hemorrhage during transurethral prostatectomy

OBJECTIVES

To determine whether short-term treatment of patients about to undergo transurethral resection of the prostate (TURP) with tranexamic acid (TXA) would be beneficial in reducing the associated blood loss.

METHODS

A prospective and randomized trial was conducted with 136 men requiring TURP for obstructive urinary symptoms. The treatment group received 2 g TXA three times daily on the day of, and first day after, the operation.

RESULTS

Short-term TXA treatment significantly reduced the operative blood loss associated with TURP (128 mL versus 250 mL, P = 0.018), and this difference was not a result of the amount of tissue resected between the two groups (16 g versus 16 g, P = 0.415). In addition, TXA treatment reduced the amount of blood loss per gram of resected tissue (8 mL/g versus 13 mL/g, P = 0.020). Furthermore, the volume of irrigating fluid required (15 L versus 18 L, P = 0.004) and operating time (36 minutes versus 48 minutes, P = 0.001) were also reduced. However, TXA treatment did not influence the number of patients requiring a blood transfusion. Six patients in the treatment group (7.2%) and five in the control group (6.8%) required a transfusion (P = 0.709). Moreover, TXA treatment did not affect the duration of catheterization (1 day versus 1 day, P = 0.342) or hospitalization (3 days versus 3 days, P = 0.218).

CONCLUSIONS

Short-term TXA treatment is effective in reducing the operative blood loss associated with TURP.

The independent association of massive blood loss with mortality in cardiac surgery

BACKGROUND

Although the association between massive perioperative blood loss (MBL) and adverse outcomes is well recognized, it is unclear whether MBL is an independent risk factor or, instead, simply a marker for other adverse events or severity of illness. The objective of this cohort study was to quantify the independent association of MBL in cardiac surgery with all-cause in-hospital mortality.

STUDY DESIGN AND METHODS

Data were prospectively collected on consecutive patients who underwent cardiac surgery with cardiopulmonary bypass at a quaternary-care academic center from 1999 to 2003. The number of red blood cell (RBC) units transfused within 1 day of surgery was used as a surrogate measure of perioperative blood loss. Receiver-operating characteristic curve analyses were employed to identify the most appropriate cutoff for defining MBL. The independent association of MBL with mortality was determined with multivariable logistic regression analyses. Bootstrapping and sensitivity analyses were used to confirm the validity of the results.

RESULTS

MBL was defined as receiving at least 5 units of RBCs within 1 day of surgery. Of 9215 patients analyzed, 1.8 percent (n = 169) died and 9.7 percent (n = 890) had MBL. After adjusting for multiple potential confounders (including perioperative adverse events), MBL was associated with an 8.1-fold (95% confidence interval, 3.9-17.0) increase in the odds of death. This risk estimate was stable across different modeling conditions as well as in bootstrap sampling.

CONCLUSION

MBL after cardiac surgery has a strong, independent association with in-hospital mortality.

Inflammatory response to cardiac surgery: cardiopulmonary bypass versus non-cardiopulmonary bypass surgery

Cardiac surgery has been routinely performed using cardiopulmonary bypass (CPB) ever since its clinical introduction during the 1950s. CPB is, however, associated with an intense inflammatory response because of conversion to laminar flow, blood contact with the artificial bypass surface, cold cardiac ischaemia and hypothermia. The inflammatory reaction can intensify to a systemic inflammatory response syndrome (SIRS) associated with serious morbidity and mortality. Strategies to suppress inflammation had some success but fell short of controlling SIRS. The development of cardiac immobilization techniques allowing complete revascularization has caused a renaissance of coronary artery bypass grafting surgery on the beating heart (OPCAB). This strategy avoids all inflammation caused by CPB and reduces the pro-inflammatory stimulus to sternotomy and the revascularization procedure itself. This review summarises the pathophysiological features of the inflammatory response to CPB, revisits therapeutic anti-inflammatory strategies designed to suppress CPB-induced inflammation and balances the clinical evidence available comparing off-pump and on-pump revascularization.

Effect of aprotinin on clinical outcomes in coronary artery bypass graft surgery: A systematic review and meta-analysis of randomized clinical trials

OBJECTIVE

Despite proven blood transfusion benefits, aprotinin may be underused in coronary artery bypass grafting. Reluctance to use aprotinin may stem from safety concerns. The current objective was to evaluate clinical outcomes (mortality, myocardial infarction, renal failure, stroke, atrial fibrillation) in patients undergoing coronary artery bypass grafting who receive aprotinin by performing a quantitative overview of published, randomized, controlled trials.

METHODS

MEDLINE, EMBASE, and PHARMLINE (1988-2001) and reference lists of relevant articles were searched for coronary artery bypass grafting studies. Criteria for data inclusion were as follows: (1) random allocation of study treatments, (2) placebo control, (3) enrollment only of patients undergoing coronary artery bypass grafting, (4) no combination with another experimental medication or device, and (5) prophylactic and continuous intraoperative use.

RESULTS

Data from 35 coronary artery bypass grafting trials (n = 3879) confirm that aprotinin reduces transfusion requirements (relative risk 0.61, 95% confidence interval 0.58-0.66) relative to placebo, with a 39% risk reduction. Aprotinin therapy was not associated with increased or decreased mortality (relative risk 0.96, 95% confidence interval 0.65-1.40), myocardial infarction (relative risk 0.85, 95% confidence interval 0.63-1.14), or renal failure (relative risk 1.01, 95% confidence interval 0.55-1.83) risk, but it was associated with a reduced risk of stroke (relative risk 0.53, 95% confidence interval 0.31-0.90) and a trend toward reduced atrial fibrillation (relative risk 0.90, 95% confidence interval 0.78-1.03).

CONCLUSIONS

Aprotinin reduces transfusion requirements. Concerns that aprotinin therapy is associated with increased mortality, myocardial infarction, or renal failure risk is not supported by data from published, randomized, placebo-controlled clinical trials. Evidence for a reduced risk of stroke and a tendency toward reduction of atrial fibrillation occurrence was observed in patients who received aprotinin.

Effects of tranexamic acid on postoperative bleeding and related hematochemical variables in coronary surgery: Comparison between on-pump and off-pump techniques

OBJECTIVES

Bleeding and inflammation are major complications of extracorporeal circulation. Off-pump coronary artery bypass grafting may reduce the rate of complications, but it can only be applied in selected cases. Pilot studies have shown a potential benefit from the use of antifibrinolytic drugs, but efficacy in randomized double-blind studies evaluating off- and on-pump coronary artery bypass grafting has not been proved.

METHODS

We enrolled 102 patients scheduled for on-pump (n = 51) or off-pump (n = 51) coronary artery bypass grafting. Patients were separately double-blind randomly assigned to treatment with tranexamic acid (1 g as 20-minute bolus before skin incision, followed by continuous infusion of 400 mg/h, with 500 mg added to priming in patients undergoing on-pump coronary artery bypass grafting) or placebo (saline solution of equivalent volume). Bleeding in the first 24 postoperative hours was the primary outcome. Requirement for allogeneic transfusions, thrombotic complications, outcomes, and monitoring of coagulation, fibrinolysis, and inflammation were also recorded.

RESULTS

Tranexamic acid reduced total postoperative bleeding by 43% in patients undergoing on-pump coronary artery bypass grafting and by 27% in those undergoing off-pump coronary artery bypass grafting (P <.0001), with 80% reduction in bleeding exceeding 600 mL (P <.001), 58% reduction in the requirement for all allogeneic transfusions (P =.07), and no apparent effect on thrombotic complications or outcome. This was associated with a reduction in plasma D-dimer levels (P <.0001), to a greater degree in patients undergoing on-pump coronary artery bypass grafting (P <.0001), and interleukin 6 levels (P <.0001), to a greater degree in patients undergoing off-pump coronary artery bypass grafting (P <.001).

CONCLUSIONS

By affecting fibrinolysis, tranexamic acid significantly reduces bleeding both in off- and on-pump coronary artery bypass grafting and may modulate inflammation in these surgical settings.

Coagulation disorders of cardiopulmonary bypass: a review

BACKGROUND

Postoperative bleeding is one of the most common complications of cardiac surgery.

DISCUSSION

Extensive surgical trauma, prolonged blood contact with the artificial surface of the cardiopulmonary bypass (CPB) circuit, high doses of heparin, and hypothermia are all possible triggers of a coagulopathy leading to excessive bleeding. Platelet activation and dysfunction also occur and are caused mainly by heparin, hypothermia, and inadequate protamine administration. Heparin and protamine administration based on heparin concentrations as opposed to fixed doses may reduce coagulopathy and postoperative blood loss.

CONCLUSIONS

A better comprehension of the multifactorial mechanisms of activation of coagulation, inflammation, and fibrinolytic pathways during CPB may enable a more effective use of the technical and pharmaceutical options which are currently available.

Recombinant Factor VIIa for Life-Threatening Bleeding in High-Risk Cardiac Surgery Despite Full-Dose Aprotinin

We report the case of an orthotopic heart transplant in a patient with multiple previous cardiac surgeries. The case was prolonged and complicated by severe coagulopathy and bleeding despite the use of full-dose aprotinin throughout. Bleeding was not controlled after 30 U of platelets, 20 U of fresh frozen plasma, and 10 U of cryoprecipitate. However, after the administration of recombinant factor VIIa 90 microg/kg, the rate of bleeding slowed dramatically and no further factor replacement was required. There was no evidence of unwanted clot formation within the newly transplanted heart or around the intraaortic balloon pump that remained in situ for 72 h postoperatively. With the combined risks of coagulopathy and bleeding as well as acute right ventricular failure with increases in pulmonary vascular resistance, the re-do sternotomy for heart transplant seems to be an ideal situation in which to consider the use of recombinant factor VIIa.

Efficacy and safety of aprotinin in cardiac surgery

Cardiac surgery and cardiopulmonary bypass produces bleeding and the need for allogenic blood product transfusions in many patients. Blood conservation is important in the perioperative management of patients. Aprotinin, a serine protease inhibitor isolated from bovine lung, is a complex protease inhibitor that is an antifibrinolytic, inhibits contact activation, and decreases the inflammatory response to cardiopulmonary bypass. Aprotinin reduces blood loss and transfusion requirements in adult and pediatric patients undergoing cardiac surgery with cardiopulmonary bypass. Full-dose aprotinin significantly reduces postoperative blood loss and has been demonstrated in multiple prospective blinded studies to be safe and effective. One of the major adverse effects is anaphylaxis that occurs on re-exposure to aprotinin.

[Pharmacological alternatives to blood transfusion: what is new about?]

Pharmacological approaches to reduce blood transfusion include the protease inhibitor aprotinin, lysine-analogue antifibrinolytics synthetic arginine-vasopressin derivatives (DDAVP) and recombinant factor VII (rfVIIa). These agents are known to prevent the need for blood after major surgery (cardiac, hepatic, and orthopaedic). Among the nonhemostatic agents erythropoietin (EPO) may be effective to reduce blood requirements in medical and surgical patients. Aprotinin is consistently effective in reducing blood transfusion in cardiac and hepatic surgical procedures, but there is little data to support its use in elective orthopaedic surgery. Antifibrinolytics show no evidence of efficacy in cardiac and hepatic surgery and its use is not warranted in orthopaedic surgery. Limited data suggest that DDAVP may be effective when a defect in platelet function is demonstrated. rFVIIa emerges as a promising haemostatic agent with proven benefit to reduce bleeding in haemophiliacs with inhibitors but might also be effective in patients with thrombocytopenia and thrombopathy, as well as in life-threatening hemorrhage in postsurgical patients. Ongoing studies will established its role a possible "universal haemostatic agent". Hematopoietic cytokines, such as EPO, may have a place to avoid blood transfusion in a variety of clinical conditions, including cancer and critically ill patients.

Strategies to reduce perioperative blood loss related to non-surgical bleeding

The treatment of critically ill patients has advanced markedly over the last decade. However, non-surgical bleeding of a diffuse nature from numerous tiny capillaries still remains a challenge. Once initiated, this type of bleeding may be troublesome and a vicious circle develops since it is not a single vessel contributing to this blood loss. The description 'non-surgical blood loss' is often given to this. This review describes a step-by-step approach for the treatment of non-surgical bleeding and includes various measures, such as desmopressin, blood components, antifibrinolytics, antithrombin III, prothrombin complex concentrates and factor XIII. While most non-surgical bleedings can be managed using the approach described here, a number of patients still continue to bleed. In these cases, the surgeon should re-evaluate the bleeding in terms of its surgical origin. If this can positively be excluded and if all of measures described fail to reduce or stop the bleeding, further treatment of such uncontrolled bleeding remains symptomatic.

Prophylactic Treatment with Desmopressin Does Not Reduce Postoperative Bleeding After Coronary Surgery in Patients Treated with Aspirin Before Surgery

The synthetic vasopressin analog desmopressin has hemostatic properties and may reduce postoperative bleeding after coronary artery bypass grafting (CABG). A study on the effects of recent aspirin ingestion on platelet function in cardiac surgery showed a greater impairment of platelet function in patients treated with aspirin <2 days before the operation. We evaluated the effects of desmopressin on postoperative bleeding in CABG patients who were treated with aspirin 75 or 160 mg until the day before surgery. The study was a prospective, randomized, double-blinded, placebo-controlled, parallel group trial. One-hundred patients were included and divided into two groups. One group received desmopressin 0.3 micro g/kg and the other received placebo (0.9% NaCl) after the neutralization of heparin with protamine sulfate. Postoperative blood loss was recorded for 16 h. The mean (SD) bleeding was 606 (237) mL in the desmopressin group and 601 (301) mL in the placebo group (P = 0.93), representing no significant difference (95% confidence interval, -107 to 117 mL). We conclude that desmopressin does not reduce postoperative bleeding in CABG patients treated with aspirin until the day before surgery.

IMPLICATIONS

Continuation of aspirin until the day before coronary artery bypass grafting may increase postoperative bleeding. The administration of desmopressin to these patients after the neutralization of heparin with protamine sulfate does not reduce postoperative bleeding.

New strategies to control the inflammatory response in cardiac surgery

PURPOSE OF REVIEW

To present and interpret data from recent clinical studies (July 2002-August 2003) of strategies to control the inflammatory response after cardiac surgery.

RECENT FINDINGS

Off-pump coronary artery bypass techniques, which avoid the need for extracorporeal circulation, attenuate the inflammatory response and appear to confer clinical benefit. Concerns regarding the quality of the revascularization after off-pump coronary artery bypass appear to have been allayed. At present, ventricular assist devices do not enhance the efficacy of off-pump coronary artery bypass. In patients undergoing cardiopulmonary bypass, heparin-coated circuits, hypothermic pulmonary perfusion, normoxic reperfusion after aortic unclamping, and modified ultrafiltration hold promise. Strategies to maintain perioperative haemodynamic stability, such as enoximone therapy, may be beneficial, particularly in elderly patients. Aprotinin may have important beneficial anti-inflammatory actions in higher-risk adult and paediatric patients. The therapeutic potential of corticosteroids, particularly when administered in multiple dosages is increasingly clear. Direct anti-mediator therapies that focus upon key effector molecules and pathways of the inflammatory response offer future therapeutic options.

SUMMARY

The potential for strategies that inhibit the inflammatory response to improve outcome after cardiac surgery is clear. Large-scale multicentre trials investigating the most promising strategies, including off-pump coronary artery bypass, heparin-coated circuits, and perioperative corticosteroid and aprotinin therapy, are urgently needed. These trials need to be restricted to the high-risk patient groups most likely to experience benefit. In the interim, the optimal strategy to minimize the inflammatory response to cardiac surgery will remain elusive.

Avoidance of Bleeding During Surgery in Patients Receiving Anticoagulant and/or Antiplatelet Therapy

Perioperative management of chronically anticoagulated patients and/or patients treated with antiplatelet therapy is a complex medical problem. This review considers the pharmacokinetic and pharmacodynamic properties of commonly used antiplatelet and anticoagulant drugs with special emphasis on loss of effects after discontinuation and possible counteracting (or antidote) strategies. These drugs are aspirin (acetylsalicylic acid), ticlopidine/clopidogrel, abciximab, tirofiban and eptifibatide, heparin (unfractionated and low-molecular-weight), warfarin and direct thrombin inhibitors. Since the pharmacological mechanisms of some of these drugs are based on irreversible or slowly reversible effects, their pharmacokinetic profiles are not necessarily predictive for their pharmacodynamic profiles. A close and direct relationship between plasma concentrations and effects is seen only for the glycoprotein (GP) IIb/IIIa inhibitors tirofiban and eptifibatide with a fast off-rate for dissociation from the GPIIb/IIIa receptor, and for direct thrombin inhibitors (hirudin and argatroban). For other compounds, drug concentrations in plasma and pharmacodynamic effects are not closely correlated because of, for example, irreversible binding to their target (aspirin, clopidogrel and abciximab), inhibition of the generation of a subset of clotting factors with differing regeneration and degradation rates (coumarins) or sustained binding to the vascular wall (heparins). Surgery in patients on anticoagulant and/or antiplatelet therapy may be categorised as: (i) elective versus urgent; and (ii) cardiopulmonary bypass (CPB) versus non-CPB. Monotherapy with clopidogrel or aspirin need not be discontinued in elective non-CPB surgery, and temporary discontinuation of warfarin should be accompanied by preoperative intravenous heparin only in selected high-risk patients. Vitamin K as an antidote for warfarin should only be used subcutaneously and solely in urgent/emergency surgery. In elective surgery requiring CPB (coronary artery bypass grafting), it is recommended to discontinue aspirin 7 days preoperatively in patients with a low risk profile. Patients requiring urgent CPB surgery (e.g. after failure of a percutaneous coronary angioplasty with or without coronary stent deployment) are usually pretreated with several antiplatelet agents (e.g. aspirin and clopidogrel, together with a GPIIb/IIIa inhibitor) together with unfractionated or low-molecular-weight heparin. With judicious planning, urgent/emergency cardiac surgery can be safely performed on these patients. Delaying surgery (e.g. for 12 hours in patients treated with abciximab) should be considered if possible. Standard heparin doses should be given to achieve optimal anticoagulation for CPB. Prophylactic use of aprotinin (intra- and/or postoperatively), aminocaproic acid or tranexamic acid should be considered. Early (in the operating theatre prior to chest closure) and judicious use of replacement blood products (platelets) should be commenced when clinically indicated.

Desmopressin for minimising perioperative allogeneic blood transfusion

BACKGROUND

Public concerns regarding the safety of transfused blood have prompted re-consideration of the use of allogeneic (from an unrelated donor) red blood cell (RBC) transfusion, and of a range of techniques designed to minimise transfusion requirements.

OBJECTIVES

To examine the evidence for the efficacy of desmopressin acetate (1-deamino-8-D-arginine-vasopressin; DDAVP), in reducing perioperative blood loss and the need for red cell transfusion in patients who do not have congenital bleeding disorders.

SEARCH STRATEGY

Articles were identified by: computer searches of MEDLINE, EMBASE, Current Contents (to May 2003), and the Cochrane Central Register of Controlled Trials (CENTRAL) (Cochrane Library, Issue 1, 2003). References in the identified trials and review articles were searched and authors contacted to identify additional studies.

SELECTION CRITERIA

Controlled parallel group trials in which adult patients, scheduled for non-urgent surgery, were randomised to DDAVP, or to a control group, who did not receive the intervention.

DATA COLLECTION AND ANALYSIS

Trial quality was assessed using criteria proposed by Schulz et al. (Schulz 1995) and Jadad et al. (Jadad 1996). Main outcomes measured were: the number of patients exposed to allogeneic red cell transfusion, and the amount of blood transfused. Other outcomes measured were: re-operation for bleeding, blood loss, post-operative complications (thrombosis, infection, non-fatal myocardial infarction), mortality, and length of hospital stay (LOS).

MAIN RESULTS

Eighteen trials of DDAVP (n=1295) reported data on the number of patients transfused with allogeneic RBC transfusion. In subjects treated with DDAVP, the pooled relative risk of exposure to perioperative allogeneic RBC transfusion was 0.95 (95%CI = 0.86 to 1.06). The use of DDAVP did not significantly reduce blood loss; weighted mean difference (WMD) = -114.3ml: 95% confidence interval (95%CI) = -258.8 to 30.2ml per patient) or the volume of RBC transfused (WMD = -0.35 units: 95%CI = -0.70 to 0.01 units). In DDAVP-treated patients the relative risk of requiring re-operation due to bleeding was 0.69 (95%CI = 0.26 to 1.83). There was no statistically significant effect overall for mortality and non-fatal myocardial infarction in DDAVP-treated patients compared with control (RR = 1.72: 95%CI = 0.68 to 4.33) and (RR = 1.38: 95%CI = 0.77 to 2.50) respectively.

REVIEWER'S CONCLUSIONS

There is no convincing evidence that desmopressin minimises perioperative allogeneic RBC transfusion in patients who do not have congenital bleeding disorders. These data suggest that there is no benefit from using DDAVP as a means of minimising perioperative allogeneic RBC transfusion.

A randomized trial of aprotinin (Trasylol) on blood loss, blood product requirement, and myocardial injury in total arterial grafting

BACKGROUND

Total arterial grafting is increasingly preferred in coronary artery bypass grafting, but it increases blood loss. Aprotinin (Trasylol; Bayer Corp, Leverkusen, Germany) reduces blood loss in cardiac surgery but has not been subjected to a randomized trial in total arterial grafting.

METHODS

A single-center, randomized, double blind, placebo-controlled trial of aprotinin administration in total arterial grafting was performed. The primary outcome variable was postoperative blood loss, and the secondary outcome variable was the number of units of donor blood or coagulant products transfused. The incidence of myocardial injury was determined from serial measurements of cardiac troponin T and creatine kinase-MB and renal injury from serum creatinine.

RESULTS

The placebo group (n = 34) and aprotinin group (n = 36) were similar with respect to all preoperative and intraoperative comparisons. One patient in each group underwent reexploration for bleeding. Open-label aprotinin was administered to 9 patients in the placebo group (26%) and to 2 patients in the aprotinin group (6%). There was a highly significant reduction in the median (interquartile range) blood loss in the aprotinin group compared with the placebo group (785 mL [590-1025 mL] vs 1525 mL [1175-1920 mL], respectively). Similarly, the aprotinin group demonstrated a marked reduction in the need for blood transfusion (77% vs 39%; P =.0001), the mean number of transfused blood units (2.6 vs 0.8, P <.001), and the number of patients requiring coagulant products (24% vs 3%; P <.001). There was no difference in myocardial injury in the 2 groups. Four patients in the aprotinin group had persistently elevated creatinine levels in the postoperative period (3 of whom had elevated preoperative creatinine levels and perioperative complications).

CONCLUSIONS

Aprotinin significantly reduces blood loss and the need for blood component transfusion in patients undergoing total arterial grafting without increasing the risk of myocardial injury. Aprotinin should be considered routinely in patients undergoing total arterial grafting but cautiously in patients with an elevated preoperative creatinine level.

Antifibrinolytic therapy during cardiopulmonary bypass reduces proinflammatory cytokine levels: a randomized, double-blind, placebo-controlled study of ϵ-aminocaproic acid and aprotinin

OBJECTIVES

Aprotinin is a broad-spectrum serine protease inhibitor that has been shown to attenuate the systemic inflammatory response in patients undergoing cardiac surgery with cardiopulmonary bypass. Although epsilon-aminocaproic acid is similar to aprotinin in its ability to inhibit excessive fibrinolysis (ie, plasmin activity and D-dimer formation), its ability to influence proinflammatory cytokine production remains unclear. This study was designed to compare the effects of epsilon-aminocaproic acid and aprotinin on plasma levels of interleukin-6 and interleukin-8 during and after cardiopulmonary bypass.

METHODS

Sixty patients were randomized in a double-blind fashion to receive epsilon-aminocaproic acid, aprotinin, or saline (placebo) in similar dosing regimens (loading dose, pump prime, and infusion). Arterial blood samples were collected before, during, and after cardiopulmonary bypass, and plasma levels of D-dimer, interleukin-6, and interleukin-8 were measured. Data were analyzed using repeated measures analysis of variance.

RESULTS

Both epsilon-aminocaproic acid and aprotinin administration resulted in significant (P <.05) reductions in D-dimer and interleukin-8 levels compared with saline. These reductions in D-dimer and interleukin-8 levels did not differ between the 2 drug-treated groups. The effect of these two antifibrinolytic agents on interleukin-6 was qualitatively similar to that noted with interleukin-8 but did not reach statistical significance.

CONCLUSIONS

When dosed in a similar manner, epsilon-aminocaproic acid seems to be as effective as aprotinin at reducing interleukin-6 and interleukin-8 levels in patients undergoing primary coronary artery bypass graft surgery. These data indicate that suppression of excessive plasmin activity or D-dimer formation or both may play an important role in the generation of proinflammatory cytokines during and after cardiopulmonary bypass.

Current status of antifibrinolytics in cardiopulmonary bypass and elective deep hypothermic circulatory arrest

Cardiopulmonary bypass (CPB) results in many physiologic derangements, including activation of the hemostatic and fibrinolytic pathways. Deep hypothermic circulatory arrest (DHCA) adds a further insult to the coagulation systems because it involves more extreme hypothermia and organ ischemia related to blood stasis. The abnormalities induced by CPB disrupt the checks and balances in the hemostatic and fibrinolytic systems, resulting in a pathologic state that leads to excessive bleeding and other perioperative complications. Prophylactic antifibrinolytic therapy can attenuate the response to this insult by restoring the delicate balance within these systems, potentially reducing the complication rate and improving patient outcomes.

The management of perioperative bleeding

Excess perioperative bleeding remains a major complication following surgery, resulting in increased morbidity and mortality. The principal causes of non-surgical haemostatic perioperative bleeding are a pre-existing undetected bleeding disorder, related to the nature of the operation itself or from coagulation abnormalities arising from massive blood loss. Very often, it is a combination and coexistence of various pathologies. Identifying patients at risk remains a major component of preventing excessive blood loss. Understanding the haemostatic changes occurring in the perioperative period, especially in complex procedures like cardiopulmonary bypass and orthotopic liver transplantation is crucial in developing new strategies for the management of perioperative bleeding. Pharmacological interventions, especially aprotinin, tranexamic acid, desmopressin and increasingly, recombinant VIIa are being used both in prophylaxis and therapeutically to stop bleeding. The use of near patient testing like thromboelastography and platelet function analyser has allowed for more detailed assessment of the various steps of haemostasis. One of the main goals is to reduce the usage of allogeneic blood transfusion and its attendant risks.

Pharmacological strategies to decrease transfusion requirements in patients undergoing surgery

Surgical procedures are inevitably associated with bleeding. The amount of blood loss may vary widely between different surgical procedures and depends on surgical as well as non-surgical factors. Whereas adequate surgical haemostasis may suffice in most patients, pro-haemostatic pharmacological agents may be of additional benefit in patients with (diffuse) surgical bleeding or in patients with a specific underlying haemostatic defect. In general, surgical haemostasis and pharmacological therapies can be complementary in controlling blood loss. The use of pharmacological therapies to reduce blood loss and blood transfusions in surgery has historically been restricted to a few drugs. Antifibrinolytic agents (aprotinin, tranexamic acid and aminocaproic acid) have the best evidence supporting their use, especially in cardiac surgery, liver transplantation and some orthopaedic surgical procedures. Meta-analyses of randomised, controlled trials in cardiac patients have suggested a slight benefit of aprotinin, compared with the other antifibrinolytics. Desmopressin is the treatment of choice in patients with mild haemophilia A and von Willebrand disease. It has also been shown to be effective in patients undergoing cardiac surgery who received aspirin up to the time of operation. However, overall evidence does not support a beneficial effect of desmopressin in patients without pre-existing coagulopathy undergoing elective surgical procedures. Topical agents, such as fibrin sealants have been successfully used in a variety of surgical procedures. However, only very few controlled clinical trials have been performed and scientific evidence supporting their use is still limited. Novel drugs, like recombinant factor VIIa (eptacog alfa), are currently under clinical investigation. Recombinant factor VIIa has been introduced for the treatment of haemophilia patients with inhibitors, either in surgical or non-surgical situations. Preliminary data indicate that it may also be effective in surgical patients without pre-existing coagulation abnormalities. More clinical trials are warranted before definitive conclusions can be drawn about the safety and the exact role of this new drug in surgical patients. Only adequately powered and properly designed randomised, clinical trials will allow us to define the most effective and the safest pharmacological therapies for reducing blood loss and transfusion requirements in surgical patients. Future trials should also consider cost-effectiveness because of considerable differences in the costs of the available pro-haemostatic pharmacological agents.

[Identification of risk factors for allogenic transfusion in cardiac surgery from an observational study]

OBJECTIVE

To determine perioperative variables for predicting allogenic transfusion in adult cardiac surgery.

STUDY DESIGN

Prospective study.

PATIENTS

We included 335 consecutive patients undergoing cardiac surgery between February and April 2001.

METHODS

Perioperative variables were prospectively collected in a database. For each patient who received transfusion, hemoglobin threshold for transfusion and total number of units of red cell concentrates were collected. Univariate and multivariate analysis were performed.

RESULTS

The two strategies for blood conservation which were predominantly used were aprotinin therapy (78%) and blood salvage from the extracorporeal circuit (68%). During perioperative period, 42% of patients [95% CI: 37-47%] received allogenic transfusion. The haemoglobin threshold for transfusion was 7.4 +/- 1.1 and 8.0 +/- 0.7 g x dl(-1) in operating room and in intensive care unit, respectively. On average, 3.4 +/- 2.7 units of red cell concentrates were transfused perioperatively per patient. Using multivariate analysis, perioperative allogenic transfusion was significantly associated with the following variables: preoperative haemoglobin level < 12 g x dl(-1) (odds ratio 8.9; p = 0.001), emergency procedure (odds = 3.7, p = 0.01), reoperation (odds ratio = 3.3; p = 0.002), chronic obstructive pulmonary disease (odds ratio = 2.5; p = 0.03) and complex surgery (odds ratio = 2.4; p = 0.01). The age, the gender, and body mass index were only independent risk factors by univariate analysis.

CONCLUSION

In despite of techniques to limit requirement of allogenic transfusion, a large proportion of cardiac surgical patients remains transfused. Independent risk factors of perioperative transfusion are haemoglobin level < 12 g x dl(-1), emergency procedure, reoperation, chronic obstructive pulmonary disease and complex surgery.

Single-dose tranexamic acid reduces postoperative bleeding after coronary surgery in patients treated with aspirin until surgery

Tranexamic acid reduces postoperative bleeding after coronary artery bypass grafting. We evaluated the effects of a single dose of tranexamic acid given immediately before cardiopulmonary bypass (CPB) in patients treated with aspirin until the day before surgery. The study was a prospective, randomized, double-blinded, placebo-controlled, parallel-group trial. Eighty patients were included and divided into two groups: one group received tranexamic acid 30 mg/kg, and one group received placebo (0.9% NaCl) as a bolus injection before CPB. Postoperative blood loss was recorded for 16 h. Transfusions of blood products were recorded for the whole hospital stay. Transfusions of packed red cells were given when the hematocrit value was less than 20% during CPB and less than 25% after surgery. The patients in the tranexamic acid group had significantly less postoperative bleeding compared with the patients in the placebo group (mean [SD]) (475 [274] mL versus 713 [243] mL; P < 0.001). An effective inhibition of fibrinolysis was found in patients receiving tranexamic acid. Tranexamic acid reduces postoperative bleeding in coronary artery bypass grafting patients treated with aspirin until the day before surgery.

IMPLICATIONS

Continuation of aspirin medication until the day before coronary artery bypass grafting may increase postoperative bleeding. The administration of a single dose of tranexamic acid (30 mg/kg) immediately before cardiopulmonary bypass significantly reduced postoperative bleeding and inhibited fibrinolysis in these patients.

Stress doses of hydrocortisone reduce severe systemic inflammatory response syndrome and improve early outcome in a risk group of patients after cardiac surgery

OBJECTIVE

Severe systemic inflammation with a vasodilatory syndrome occurs in about one third of all patients after cardiac surgery with cardiopulmonary bypass. Hydrocortisone has been used successfully to reverse vasodilation in septic patients. We evaluated if stress doses of hydrocortisone attenuate severe systemic inflammatory response syndrome in a predefined risk group of patients after cardiac surgery with cardiopulmonary bypass.

DESIGN

Randomized, nonblinded, controlled trial.

SETTING

Anesthesiologic intensive care unit for cardiac surgical patients of an university hospital.

PATIENTS

After a risk analysis, we enrolled 91 patients into a prospective randomized trial. Patients were included according to the evaluated criteria (preoperative ejection fraction, duration of cardiopulmonary bypass, type of surgery).

INTERVENTIONS

The treatment group received stress doses of hydrocortisone perioperatively: 100 mg before induction of anesthesia, then 10 mg/hr for 24 hrs, 5 mg/hr for 24 hrs, 3 x 20 mg/day, and 3 x 10 mg/day.

MEASUREMENTS AND MAIN RESULTS

We measured various laboratory (e.g., lactate) and clinical variables (e.g., duration of ventilation and length of stay in the intensive care unit), characterizing the patients' outcome. The two study groups did not differ regarding age, preoperative medication, duration of the cardiopulmonary bypass, and type of surgery. The patients in the treatment group had significantly lower concentrations of IL-6 and lactate, higher antithrombin III concentration, lower need for circulatory and ventilatory support and for transfusions, lower Therapeutic Intervention Scoring System values, and shorter length of stay in the intensive care unit and in the hospital. The mortality rate did not differ significantly between the groups.

CONCLUSIONS

Although we acknowledge the limitations of a nonblinded interventional trial, stress doses of hydrocortisone seem to attenuate systemic inflammation in a predefined risk group of patients after cardiac surgery with cardiopulmonary bypass and improve early outcome.

Factors determining the duration of tracheal intubation in cardiac surgery: a single-centre sequential patient audit

BACKGROUND AND OBJECTIVE

The study was designed to identify those factors associated with early tracheal extubation following cardiac surgery. Previous studies have tended to concentrate on surgery for coronary artery bypass or on other selected cohorts.

METHODS

Sequential cohort analysis of 296 unselected adult cardiac surgery patients was performed over 3 months.

RESULTS

In total, 39% of all patients were extubated within 6 h, 89% within 24 h and 95% within 48 h. Delayed extubation (>6 h after surgery) appeared unrelated to age, gender, body mass index, a previous pattern of angina or myocardial infarction, diabetes, preoperative atrial fibrillation, and preoperative cardiovascular assessment, as well as other factors. Delayed tracheal extubation was associated with poor left ventricular, renal and pulmonary function, a high Euroscore, as well as the type, duration and urgency of surgery. Early extubation (<6 h) was not associated with a reduced length of stay in either the intensive care unit or in hospital compared with patients who were extubated between 6 and 24 h. In these groups, it is presumed that organizational and not clinical factors appear to be responsible for a delay in discharge from intensive care. Patients who were extubated after 24 h had a longer duration of hospital stay and a greater incidence of postoperative complications. Postoperative complications were not adversely affected by early tracheal extubation.

CONCLUSIONS

In an unselected sequential cohort, both patient- and surgery-specific factors may be influential in determining the duration of postoperative ventilation of the lungs following cardiac surgery. In view of the changing nature of the surgical population, regular re-evaluation is useful in reassessing performance.

Injection pain of rocuronium and vecuronium is evoked by direct activation of nociceptive nerve endings

BACKGROUND AND OBJECTIVE

Rocuronium and, to a lesser extent, vecuronium can induce burning sensations associated with withdrawal reactions during administration. Dermal microdialysis in human and electrophysiological recordings of nociceptors in mouse skin were used to elucidate the underlying mechanisms of pain induction.

METHODS

Microdialysis catheters were inserted intradermally into the forearm of 10 volunteers and were perfused with two different concentrations of rocuronium and vecuronium (1 and 10 mg mL(-1)) or a control. Dialysis samples were taken every 15 min and analysed for protein, histamine, tryptase and bradykinin content. Pain intensity was rated on a numerical scale of 0-10. In a parallel design, activation of cutaneous nociceptors was assessed directly in a skin-nerve in vitro preparation of the mouse hind paw. The receptive fields of identified single C-nociceptors (n = 12) were superfused with rocuronium or vecuronium solutions (10 mg mL(-1)) at physiological pH.

RESULTS

In accordance with clinical observations, microdialysis of rocuronium (10 mg mL(-1)) induced sharp burning pain (NRS 4.1 +/- 1.8), whereas vecuronium given in the usual clinical concentration (1 mg mL(-1)) induced only minor pain sensations (NRS 0.6 +/- 1.3). At equimolar concentrations, pain sensation and concomitant mediator release evoked by both drugs were similar. No correlations were found between pain rating and mediator release. In the in vitro preparation, C-fibres showed a consistent excitatory response with rapid onset after stimulation with vecuronium as well as rocuronium (differences not significant).

CONCLUSIONS

The algogenic effect of aminosteroidal neuromuscular blocking drugs can be attributed to a direct activation of C-nociceptors.

Anaesthetic strategies to reduce perioperative blood loss in paediatric surgery

In adults, a number of measures to reduce perioperative blood loss have been established. These techniques serve to reduce patients' exposure to homologous blood. Most adults are concerned with this issue especially since many patients became infected with human immunodeficiency virus (HIV) during the 1980s through exposure to blood components. While blood-saving strategies are widely used in adults, they are mostly neglected in infants. However, it is these young patients with their whole life in front of them who, it could be argued, would benefit especially from any potentially avoidable infection (HIV, hepatitis, etc.) or immunological complications. In infants and small children, these blood-sparing techniques may not be as effective as in adults and technical limitations may prevent their application. However, some of these measures can be used and may serve to prevent or reduce exposure to homologous blood. In the following review, blood-saving techniques established in adults are described and their applicability for paediatric patients discussed.

A review of anti-inflammatory strategies in cardiac surgery

It is generally accepted that cardiac surgery is frequently associated with the development of systemic inflammatory response. This phenomenon is very variable clinically, and can be detected by measuring plasma concentrations of certain inflammatory markers. Complement component, cytokines and adhesion molecules are examples of these markers. Systemic inflammation can be potentially damaging to major organs. Several anti-inflammatory strategies have been used in recent years, aiming to attenuate the development of systemic inflammatory response. This article summarizes recently published literature concerning the use of anti-inflammatory techniques and pharmacological agents in cardiac surgery. In particular, the anti-inflammatory effects of off-pump surgery, leukocyte filtration, corticosteroids, aprotinin, phosphodiesterase inhibitors, dpoexamine, H2 antagonists and ACE inhibitors are reviewed. The overall conclusion is that although certain strategies reduce plasma levels of inflammatory mediators, convincing evidence of significant clinical benefits is yet to come.

Effects of propofol on the systolic and diastolic performance of the postischaemic, reperfused myocardium in rabbits

BACKGROUND AND OBJECTIVE

The effect of propofol on myocardial dysfunction during ischaemia and reperfusion is controversial yet important because of its frequent use in cardiac anaesthesia. Although animal studies suggest a free radical-scavenging potential, the cardioprotective properties of propofol have not been demonstrated consistently in vivo. Previous studies focused on systolic function while diastolic function may be a more sensitive marker of ischaemic injury. The main aim was to document the effect of propofol on diastolic function in isolated, blood perfused rabbit hearts subjected to moderate global ischaemia and reperfusion.

METHODS

Propofol 168 micromol L(-1), or the equivalent of its vehicle, Intralipid, was administered to 34 paced parabiotic Langendorff blood-perfused isolated rabbit hearts before and after 30 min of global normothermic ischaemia. Recovery of systolic function was quantified with the maximum rate of rise of left ventricular pressure. Diastolic performance was assessed using the time constant of the decline in left ventricular pressure (tau) and chamber stiffness (VdP/dV at 12 mmHg).

RESULTS

Recovery of systolic function during reperfusion was comparable in the two groups. There was no difference in left ventricular pressure between the two groups at any time during the experiments. Chamber stiffness increased significantly during ischaemia and reperfusion in the control group (from 34 +/- 9 to 54 +/- 8 mmHg during ischaemia, and 43 +/- 5 mmHg after 30 min reperfusion; mean +/-95% confidence interval) but not in the propofol-treated group (29 +/- 5, 36 +/- 8 and 30 +/- 8 at baseline, ischaemia and 30 min reperfusion, respectively).

CONCLUSIONS

Propofol has no protective effect on active relaxation or on systolic function in the present model, but it reduces ischaemic and postischaemic chamber stiffness.

Effects of bupivacaine used with sevoflurane on the rhythm and contractility in the isolated rat heart

BACKGROUND AND OBJECTIVE

The effects of sevoflurane on bupivacaine cardiotoxicity are mainly attributed to systemic effects. The purpose of this study was to investigate the direct myocardial effects of sevoflurane on bupivacaine toxicity.

METHODS

Hearts of 30 Wistar albino rats were isolated and mounted on a Langendorff apparatus perfused by modified Tyrode solution. Experimental groups were: a sevoflurane group (Group S, n = 10)--following baseline and 20 min (Stage 1) recordings, sevoflurane was added in doses of 1.4% (1 MAC) and 2.8% (2 MAC). In the two bupivacaine groups, bupivacaine 5 micromol (Group B5, n = 10) and bupivacaine 10 micromol (Group B10, n = 10) was added to the solution at Stage 1, and sevoflurane was added to the system as in Group S. Haemodynamic variables, i.e. heart rate, PR interval, QRS duration, left ventricular systolic pressure, contractility (+dp/dtmax), relaxation, time to reach peak systolic pressure, change in left ventricular diastolic pressure from baseline, and rate-pressure product were recorded.

RESULTS

In Group S, there was no change in cardiac rhythm. In bupivacaine groups, severe rhythm disturbances occurred and both the PR intervals and QRS complexes were prolonged significantly. All contractility variables deteriorated and the rate-pressure product decreased by 67-90% with the addition of bupivacaine. In all groups, 2 MAC sevoflurane lowered +dp/dtmax further.

CONCLUSIONS

Sevoflurane does not have any untoward effect on bupivacaine-induced cardiotoxicity in clinically relevant doses in the isolated rat heart.

Effect of the neuronal nitric oxide synthase inhibitor 7-nitroindazole on the righting reflex ED50 and minimum alveolar concentration during sevoflurane anaesthesia in rats

BACKGROUND AND OBJECTIVE

The aim was to determine the effect of acute and chronic administration of 7-nitroindazole, a selective neuronal nitric oxide synthase inhibitor, on the righting reflex ED50 and the minimum alveolar concentration during sevoflurane anaesthesia in rats.

METHODS

7-Nitroindazole was acutely (0, 50 and 100 mg kg(-1)) and chronically (0 and 150 mg kg(-1) day(-1), 4 days) administered to rats. After the preparation, the minimum alveolar concentration and the righting reflex ED50 were measured. The concentration of cGMP in the brain, cerebellum and spinal cord was also measured.

RESULTS

Acute administration reduced the minimum alveolar concentration (50 mg kg(-1), 58.8% (95% CI: 50.3-67.3%) of the baseline value, P < 0.01; 100 mg kg(-1), 55.8 (46.9-64.7), P < 0.01) and the righting reflex ED50 (50 mg kg(-1), 27.2 (17.2-37.2), P < 0.01; 100 mg kg(-1), 14.3 (6.6-22.0), P < 0.01). Chronic administration did not reduce the minimum alveolar concentration; however, it reduced the righting reflex ED50 (65.3 (52.9-77.7), P < 0.01). Overall, the reduction in minimum alveolar concentration in the acute and chronic protocol did not correlate with that of the righting reflex ED50. 7-Nitroindazole (100 mg kg(-1), acute) reduced the cGMP concentration within the cerebellum by 55.4%; however, it did not decrease concentrations in the brain or spinal cord.

CONCLUSIONS

Different mechanisms are responsible for the observed alterations to the minimum alveolar concentration and the righting reflex ED50 following treatment with 7-nitroindazole. The nitric oxide-cGMP pathway might play a less important role in the determination of minimum alveolar concentration than the righting reflex ED50.

Suprascapular nerve block or a piroxicam patch for shoulder tip pain after day case laparoscopic surgery

BACKGROUND AND OBJECTIVE

The reported incidence of shoulder tip pain following laparoscopic surgery varies from 35 to 63%. This study evaluated the analgesic efficacy of either performing a prophylactic suprascapular nerve block with bupivacaine or applying a piroxicam patch to the skin over both shoulders for the relief of shoulder tip pain after laparoscopy.

METHODS

Sixty healthy informed female patients were randomly assigned to one of three groups: (a) a control group (n = 20), no treatment; (b) a suprascapular nerve block group (n = 20) in which a bilateral suprascapular nerve block was performed before induction of anaesthesia with 5 mL 0.5% bupivacaine with epinephrine; and (c) a piroxicam patch group (n = 20) in which a 48 mg piroxicam patch on the skin of each shoulder was applied before induction of anaesthesia. All patients received a total intravenous anaesthesia technique with propofol, fentanyl and vecuronium. Shoulder tip and wound pain were recorded on a visual analogue pain scale at five time intervals for 24 h after surgery.

RESULTS

A total of 80% of patients in the control group, 75% in the suprascapular nerve block group and 45% in the piroxicam patch group complained of shoulder tip pain during the recording period (P < 0.05). The scores for shoulder tip pain in the piroxicam patch group were significantly lower compared with the control group at 3, 6 and 12 h, and compared with the suprascapular nerve block group at 6 and 12 h. The need for analgesics was also significantly lower in the piroxicam patch group compared with the other two groups.

CONCLUSIONS

Prophylactic piroxicam patches are effective and safe for the relief of shoulder tip pain after laparoscopy. Bilateral suprascapular nerve block is not effective in this setting.

Treatment of hiccup during general anaesthesia or sedation: a qualitative systematic review

BACKGROUND AND OBJECTIVE

Acute hiccup is a minor complication that can occur during sedation or general anaesthesia. The disorder can disturb the surgical field, might interfere with lung ventilation or could hamper diagnostic procedures. The objective was to perform a systematic search for interventions aimed at treating hiccup occurring during anaesthesia or sedation.

METHODS

A systematic search for reports describing interventions to treat hiccup in conjunction with anaesthesia was carried out (MEDLINE, EMBASE, Cochrane-Library, manual screening of reference lists and review articles, up to December 2001). Search terms were 'hiccup', 'singultus' or 'hiccough'.

RESULTS

Twenty-six reports involving approximately 581 patients focused on hiccup remedies in the anaesthesia setting. Only one report was substantiated by a randomized controlled trial. This investigated methylphenidate 10 mg intravenously in 51 patients, which did not show a beneficial effect compared with placebo. Hiccup was a self-limiting phenomenon. Case series and case reports focused on various systemically applied drugs in 12 reports, stimulating techniques (e.g. pharyngeal stimulation) in seven, topical applied remedies (e.g. intranasal ice-cold water) in four, and ventilation techniques (e.g. continuous positive pressure ventilation) in two.

CONCLUSIONS

A large variety of interventions have been proposed for the treatment of hiccup during anaesthesia and sedation. However, perioperative treatment is still based on empirical findings and no treatment is 'evidence-based'. Thus, no valid recommendations for the treatment of hiccup can be derived. Uncontrolled observations are inadequate to establish treatment efficacy.

Pharmacokinetics and pharmacodynamics of the new propofol prodrug GPI 15715 in rats

BACKGROUND AND OBJECTIVE

We studied the pharmacokinetics and pharmacodynamics of GPI 15715 (Aquavan injection), a new water-soluble prodrug metabolized to propofol by hydrolysis.

METHODS

Nine adult male Sprague-Dawley rats (398 +/- 31 g) received a bolus dose of 40 mg GPI 15715. The plasma concentrations of GPI 15715 and propofol were determined from arterial blood samples, and the pharmacokinetics of both compounds were investigated using compartment models whereby the elimination from the central compartment of GPI 15715 was used as drug input for the central compartment of propofol. Pharmacodynamics were assessed using the median frequency of the EEG power spectrum.

RESULTS

A maximum propofol concentration of 7.1 +/- 1.7 microg mL(-1) was reached 3.7 +/- 0.2 min after bolus administration. Pharmacokinetics were best described by two-compartment models. GPI 15715 showed a short half-life (2.9 +/- 0.2 and 23.9 +/- 9.9 min), an elimination rate constant of 0.18 +/- 0.01 min(-1) and a central volume of distribution of 0.25 +/- 0.02 L kg(-1). For propofol, the half-life was 1.9 +/- 0.1 and 45 +/- 7 min, the elimination rate constant was 0.15 +/- 0.02 min(-1) and the central volume of distribution was 2.3 +/- 0.6 L kg(-1). The maximum effect on the electroencephalogram (EEG)--EEG suppression for >4 s--occurred 6.5 +/- 1.2 min after bolus administration and baseline values of the EEG median frequency were regained 30 min later. The EEG effect could be described by a sigmoid Emax model including an effect compartment (E0 = 16.9 +/- 7.9 Hz, EC50 = 2.6 +/- 0.8 microg mL(-1), ke0 = 0.35 +/- 0.04 min(-1)).

CONCLUSIONS

Compared with known propofol formulations, propofol from GPI 15715 showed a longer half-life, an increased volume of distribution, a delayed onset, a sustained duration of action and a greater potency with respect to concentration.