Perioperative platelet reactivity and the effects of clonidine

Postoperative myocardial injury and platelet reactivity in patients undergoing vascular surgery: The platelet reactivity and postoperative myocardial injury after major vascular surgery (PROMISE) study

BACKGROUND

Postoperative myocardial injury (PMI) after major vascular surgery, detected by elevated cardiac troponin (cTn), has been associated with morbidity and mortality. It is unclear whether the pathophysiology of PMI is determined by increased platelet activity.

OBJECTIVE

To examine the relationship between platelet activation (P-selectin expression) and PMI in patients undergoing elective open abdominal aortic surgery.

METHODS

This prospective, single-centre, observational, cohort study included 33 patients undergoing elective open abdominal aortic surgery between March 2018 and April 2021. Patients were routinely treated with aspirin. Unstimulated platelet activation was measured by platelet bound P-selectin expression (range 0-100 %). Explorative coagulation measurements were: stimulated platelet aggregation measured with the VerifyNow® assay (aspirin cartridge), with the Multiplate® analyzer (ASPI, ADP and TRAP) and stimulated coagulation status evaluated by the TEG® Hemostasis Analyzer System (global hemostasis cartridge). The primary outcome was cTn release assessed by the fifth generation high-sensitive cTn assay. Multivariable generalized linear mixed models were used to evaluate the association between platelet function and cTn concentrations over time.

RESULTS

Ten patients (30.3 %) developed PMI. Increased P-selectin expression directly after surgery was associated with the cTn concentrations over 48 h (β = 1.39 (1.1-1.75), P = 0.0064). No association was found between P-selectin measured later after surgery (at 24 h or 48 h) and cTn concentrations. Furthermore, there was no association between the explorative coagulation parameters and cTn release.

CONCLUSION

Platelet reactivity, assessed by P-selectin expression measured directly after surgery is associated with PMI, assessed by elevated cTn concentrations in the early postoperative period in patients undergoing elective open abdominal aortic surgery.

Perioperative Myocardial Infarction in Free Flap for Head and Neck Reconstruction

INTRODUCTION

Acute myocardial infarction (AMI) is a postoperative complication of major surgical procedures, including free flap surgery. It is the most common cause of postoperative morbidity and mortality. Moreover, patients receiving free flap reconstruction for the head and neck have significant risk factors such as coexisting coronary artery disease (CAD). Our primary aim was to ascertain predictors of perioperative AMI to enable early detection and consequently early treatment of perioperative AMI. Our secondary aim was to determine the group of patients who would be at a high risk for perioperative AMI after free flap surgery.

MATERIALS AND METHODS

This retrospective study enrolled patients who underwent free flap reconstruction surgery at the Division of Plastic and Reconstructive Surgery of Taipei Veterans General Hospital between 2013-01 and 2017-12.

RESULTS

This study included 444 patients and 481 free flap head and neck reconstruction surgeries. Fifteen (3.1%) patients were diagnosed with perioperative AMI. Statistical analysis of the variables revealed that patients with underlying CAD or cerebrovascular accident (CVA) were at a high risk of developing perioperative AMI (odds ratio: 6.89 and 11.11, respectively). The flap failure rate was also higher in patients with perioperative AMI compared with those without perioperative AMI (P = 0.015).

CONCLUSIONS

Patients with underlying diseases, such as CAD or CVA, constituted high-risk groups for perioperative AMI.

Preoperative clinical model to predict myocardial injury after non-cardiac surgery: a retrospective analysis from the MANAGE cohort in a Spanish hospital

OBJECTIVES

To determine preoperative factors associated to myocardial injury after non-cardiac surgery (MINS) and to develop a prediction model of MINS.

DESIGN

Retrospective analysis.

SETTING

Tertiary hospital in Spain.

PARTICIPANTS

Patients aged ≥45 years undergoing major non-cardiac surgery and with at least two measures of troponin levels within the first 3 days of the postoperative period. All patients were screened for the MANAGE trial.

PRIMARY AND SECONDARY OUTCOME MEASURES

We used multivariable logistic regression analysis to study risk factors associated with MINS and created a score predicting the preoperative risk for MINS and a nomogram to facilitate bed-side use. We used Least Absolute Shrinkage and Selection Operator method to choose the factors included in the predictive model with MINS as dependent variable. The predictive ability of the model was evaluated. Discrimination was assessed with the area under the receiver operating characteristic curve (AUC) and calibration was visually assessed using calibration plots representing deciles of predicted probability of MINS against the observed rate in each risk group and the calibration-in-the-large (CITL) and the calibration slope. We created a nomogram to facilitate obtaining risk estimates for patients at pre-anaesthesia evaluation.

RESULTS

Our cohort included 3633 patients recruited from 9 September 2014 to 17 July 2017. The incidence of MINS was 9%. Preoperative risk factors that increased the risk of MINS were age, American Status Anaesthesiology classification and vascular surgery. The predictive model showed good performance in terms of discrimination (AUC=0.720; 95% CI: 0.69 to 0.75) and calibration slope=1.043 (95% CI: 0.90 to 1.18) and CITL=0.00 (95% CI: -0.12 to 0.12).

CONCLUSIONS

Our predictive model based on routinely preoperative information is highly affordable and might be a useful tool to identify moderate-high risk patients before surgery. However, external validation is needed before implementation.

Perioperative Ketorolac Use and Postoperative Hematoma Formation in Reduction Mammaplasty: A Single-Surgeon Experience of 500 Consecutive Cases

BACKGROUND

In light of the escalating opioid crisis, surgeons are increasingly focused on minimizing opioid use. Ketorolac has well-documented opioid-sparing effects in the postoperative period; however, its use is limited because of concerns of postoperative bleeding and hematoma formation. This study explores the relationship between hematoma formation and administration of perioperative ketorolac in adolescent female patients and young adult women undergoing reduction mammaplasty. It also aims to determine the effect of perioperative ketorolac administration on the requirement for opioid analgesia.

METHODS

The authors reviewed the medical records of 500 consecutive female patients who underwent reduction mammaplasty for bilateral macromastia from 2007 to 2017. The authors collected data pertaining to perioperative analgesia use and postoperative hematoma formation.

RESULTS

Five-hundred patients were included in analyses. The average age of the patients was 18.1 ± 2.2 years. Three hundred eighty-nine patients (77.8 percent) received intravenous ketorolac during the perioperative period. Seven patients (1.4 percent) developed a postoperative hematoma. Hematoma was not associated with intraoperative, postoperative, and perioperative ketorolac use (p > 0.43, all). Intraoperative ketorolac use was associated with lower total intraoperative dosing of fentanyl and morphine, and postoperative ketorolac use was associated with lower total postoperative doses of oxycodone and morphine (p < 0.001, all).

CONCLUSIONS

Ketorolac use was largely associated with decreased perioperative opioid use, but not with hematoma formation. Ketorolac may be a safe alternative to opioids in adolescents and young women undergoing reduction mammaplasty without increasing the risk of hematoma formation.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Alpha-2 adrenergic agonists for the prevention of cardiac complications among adults undergoing surgery

BACKGROUND

The surgical stress response plays an important role on the pathogenesis of perioperative cardiac complications. Alpha-2 adrenergic agonists attenuate this response and may help prevent postoperative cardiac complications.

OBJECTIVES

To determine the efficacy and safety of α-2 adrenergic agonists for reducing mortality and cardiac complications in adults undergoing cardiac surgery and non-cardiac surgery.

SEARCH METHODS

We searched CENTRAL (2017, Issue 4), MEDLINE (1950 to April Week 4, 2017), Embase (1980 to May 2017), the Science Citation Index, clinical trial registries, and reference lists of included articles.

SELECTION CRITERIA

We included randomized controlled trials that compared α-2 adrenergic agonists (i.e. clonidine, dexmedetomidine or mivazerol) against placebo or non-α-2 adrenergic agonists. Included trials had to evaluate the efficacy and safety of α-2 adrenergic agonists for preventing perioperative mortality or cardiac complications (or both), or measure one or more relevant outcomes (i.e. death, myocardial infarction, heart failure, acute stroke, supraventricular tachyarrhythmia and myocardial ischaemia).

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality, extracted data and independently performed computer entry of abstracted data. We contacted study authors for additional information. Adverse event data were gathered from the trials. We evaluated included studies using the Cochrane 'Risk of bias' tool, and the quality of the evidence underlying pooled treatment effects using GRADE methodology. Given the clinical heterogeneity between cardiac and non-cardiac surgery, we analysed these subgroups separately. We expressed treatment effects as pooled risk ratios (RR) with 95% confidence intervals (CI).

MAIN RESULTS

We included 47 trials with 17,039 participants. Of these studies, 24 trials only included participants undergoing cardiac surgery, 23 only included participants undergoing non-cardiac surgery and eight only included participants undergoing vascular surgery. The α-2 adrenergic agonist studied was clonidine in 21 trials, dexmedetomidine in 24 trials and mivazerol in two trials.In non-cardiac surgery, there was high quality evidence that α-2 adrenergic agonists led to a similar risk of all-cause mortality compared with control groups (1.3% with α-2 adrenergic agonists versus 1.7% with control; RR 0.80, 95% CI 0.61 to 1.04; participants = 14,081; studies = 16). Additionally, the risk of cardiac mortality was similar between treatment groups (0.8% with α-2 adrenergic agonists versus 1.0% with control; RR 0.86, 95% CI 0.60 to 1.23; participants = 12,525; studies = 5, high quality evidence). The risk of myocardial infarction was probably similar between treatment groups (RR 0.94, 95% CI 0.69 to 1.27; participants = 13,907; studies = 12, moderate quality evidence). There was no associated effect on the risk of stroke (RR 0.93, 95% CI 0.55 to 1.56; participants = 11,542; studies = 7; high quality evidence). Conversely, α-2 adrenergic agonists probably increase the risks of clinically significant bradycardia (RR 1.59, 95% CI 1.18 to 2.13; participants = 14,035; studies = 16) and hypotension (RR 1.24, 95% CI 1.03 to 1.48; participants = 13,738; studies = 15), based on moderate quality evidence.There was insufficient evidence to determine the effect of α-2 adrenergic agonists on all-cause mortality in cardiac surgery (RR 0.52, 95% CI 0.26 to 1.04; participants = 1947; studies = 16) and myocardial infarction (RR 1.01, 95% CI 0.43 to 2.40; participants = 782; studies = 8), based on moderate quality evidence. There was one cardiac death in the clonidine arm of a study of 22 participants. Based on very limited data, α-2 adrenergic agonists may have reduced the risk of stroke (RR 0.37, 95% CI 0.15 to 0.93; participants = 1175; studies = 7; outcome events = 18; low quality evidence). Conversely, α-2 adrenergic agonists increased the risk of bradycardia from 6.4% to 12.0% (RR 1.88, 95% CI 1.35 to 2.62; participants = 1477; studies = 10; moderate quality evidence), but their effect on hypotension was uncertain (RR 1.19, 95% CI 0.87 to 1.64; participants = 1413; studies = 9; low quality evidence).These results were qualitatively unchanged in subgroup analyses and sensitivity analyses.

AUTHORS' CONCLUSIONS

Our review concludes that prophylactic α-2 adrenergic agonists generally do not prevent perioperative death or major cardiac complications. For non-cardiac surgery, there is moderate-to-high quality evidence that these agents do not prevent death, myocardial infarction or stroke. Conversely, there is moderate quality evidence that these agents have important adverse effects, namely increased risks of hypotension and bradycardia. For cardiac surgery, there is moderate quality evidence that α-2 adrenergic agonists have no effect on the risk of mortality or myocardial infarction, and that they increase the risk of bradycardia. The quality of evidence was inadequate to draw conclusions regarding the effects of alpha-2 agonists on stroke or hypotension during cardiac surgery.

Use of ivabradine and atorvastatin in emergent orthopedic lower limb surgery and computed tomography coronary plaque imaging and novel biomarkers of cardiovascular stress and lipid metabolism for the study and prevention of perioperative myocardial infarction: study protocol for a randomized controlled trial

Background

The incidence of perioperative myocardial infarction (PMI) globally is known to be around 2 to 3% and can prolong hospitalization, increased morbidity and mortality. Little is known about the pathophysiology and risk factors for PMI. We investigate the presence of elevated novel cardiac markers and preoperative coronary artery plaque through contemporary laboratory techniques to determine the correlation with PMI, as well as studying ivabradine and atorvastatin as protective pharmacotherapies against PMI in the context of orthopedic surgery.

Methods/Design

We aim to enroll 200 patients aged above 60 years who suffer from neck of femur fracture requiring surgery. Patients will be randomized to four arms (no study drugs, atorvastatin only, ivabradine only and ivabradine and atorvastatin). Our primary outcome is incidence of PMI. All patients will receive an electrocardiogram, cardiac echocardiography, measurement of novel cardiac biomarkers and computed tomography (CT) coronary angiography. A telephone interview post discharge will be conducted at 30 days, 60 days and 1 year.

Discussion

We postulate that ivabradine and atorvastatin will reduce the rate and magnitude of PMI following surgery by reducing heart rate and attenuating catecholamine-induced tachycardia postoperatively. Secondly, we postulate that postoperative reduction in heart rate and catecholamine-induced tachycardia with ivabradine will correlate with a reduction in cardiovascular novel biomarkers which will reduce atrial stretch and postoperative incidence of arrhythmia. We aim to demonstrate that treatment with ivabradine and atorvastatin will cause a reduction in the incidence and magnitude of PMI, the benefit of which is derived primarily in patients with greater atherosclerotic burden as measured by higher CT coronary calcium scores.

Trial registration

This study protocol has been listed in the Australia New Zealand Clinical Trial Registry (registration number: ACTRN12612000340831) on 23 March 2012.

Alterations in homeostasis after open surgery. A prospective randomized study

INTRODUCTION

Alterations in homeostasis, and a subsequent increased risk for postoperative thromboembolic complications, are observed as a result of open surgery. Additionally, the stress response to surgical trauma precipitates a transient hypercoagulable state as well as inflammation. This study was conducted to evaluate the patterns in postoperative alterations of blood coagulation, and to detect their correlations with inflammatory markers.

PATIENTS AND METHODS

The study included 50 patients with comparable demographic data, who were randomly assigned to undergo abdominal surgery. No previous coagulation disorders were noted. Blood samples were collected preoperatively and 72 h postoperatively. The following parameters were measured: prothrombin time (PT) and activated partial thromboplastin time (APTT); fibrinogen (FIB), D-dimer (D-D), and C-reactive protein (CRP) levels; and platelet (PLT) count. Prophylactic doses of low molecular weight heparin were administered to all patients.

RESULTS

The PT mean value significantly changed from 90.38% before surgery to 81.25% after surgery. No statistical difference was observed between APTT values before and after surgery. FIB levels significantly increased from 381.50 mg/dL preoperatively to 462.57 mg/dL postoperatively. Mean D-D levels also significantly increased from 235.54 μg/L preoperatively to 803.59 μg/L postoperatively. PLT count significantly declined after surgery. Mean CRP levels significantly increased from 12.33 mg/L preoperatively to 44.28 mg/L postoperatively. A strong correlation was observed between D-D and C-RP levels after surgery.

CONCLUSION

These results indicate that, despite administering antithromboembolic prophylaxis, a hypercoagulable state was observed following surgery. This state was enhanced by inflammation.

Myocardial Injury After Noncardiac Surgery and its Association With Short-Term Mortality

Background—

To identify patients at risk for postoperative myocardial injury and death, measuring cardiac troponin routinely after noncardiac surgery has been suggested. Such monitoring was implemented in our hospital. The aim of this study was to determine the predictive value of postoperative myocardial injury, as measured by troponin elevation, on 30-day mortality after noncardiac surgery.

Methods and Results—

This observational, single-center cohort study included 2232 consecutive intermediate- to high-risk noncardiac surgery patients aged ≥60 years who underwent surgery in 2011. Troponin was measured on the first 3 postoperative days. Log binomial regression analysis was used to estimate the association between postoperative myocardial injury (troponin I level >0.06 μg/L) and all-cause 30-day mortality. Myocardial injury was found in 315 of 1627 patients in whom troponin I was measured (19%). All-cause death occurred in 56 patients (3%). The relative risk of a minor increase in troponin (0.07–0.59 μg/L) was 2.4 (95% confidence interval, 1.3–4.2; P <0.01), and the relative risk of a 10- to 100-fold increase in troponin (≥0.60 μg/L) was 4.2 (95% confidence interval, 2.1–8.6; P <0.01). A myocardial infarction according to the universal definition was diagnosed in 10 patients (0.6%), of whom 1 (0.06%) had ST-segment elevation myocardial infarction.

Conclusions—

Postoperative myocardial injury is an independent predictor of 30-day mortality after noncardiac surgery. Implementation of postoperative troponin monitoring as standard of care is feasible and may be helpful in improving the prognosis of patients undergoing noncardiac surgery.

Alpha-2 adrenergic agonists for the prevention of cardiac complications among patients undergoing surgery

BACKGROUND

The surgical stress response plays an important role on the pathogenesis of perioperative cardiac complications. Alpha-2 adrenergic agonists attenuate this response and may thereby prevent cardiac complications.

OBJECTIVES

This review assessed the efficacy and safety of preoperative (within 24 hours), intraoperative, and postoperative (first 48 hours) alpha-2 adrenergic agonists for preventing mortality and cardiac complications after surgery performed under either general or neuraxial anaesthesia, or both.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2008, Issue 3), MEDLINE (1950 to August week 4 2008), EMBASE (1980 to week 36 2008), the Science Citation Index, and reference lists of articles.

SELECTION CRITERIA

We included randomized controlled trials that compared alpha-2 adrenergic agonists (clonidine, dexmedetomidine, or mivazerol) against placebo or non-alpha-2 adrenergic agonists. Included studies had to report on mortality, myocardial infarction, myocardial ischaemia, or supraventricular tachyarrhythmia.

DATA COLLECTION AND ANALYSIS

Three authors independently assessed trial quality and extracted data. Two authors independently performed computer entry of abstracted data. We contacted study authors for additional information. Adverse event data were gathered from the trials.

MAIN RESULTS

We included 31 studies (4578 participants). Study quality was generally inadequate, with only six studies clearly reporting methods for blinding and allocation concealment. Overall, alpha-2 adrenergic agonists reduced mortality (relative risk (RR) 0.66; 95% CI 0.44 to 0.98; P = 0.04) and myocardial ischaemia (RR 0.68; 95% CI 0.57 to 0.81; P < 0.0001). However, their effects appeared to vary with the surgical procedure. The most encouraging data pertained to vascular surgery, where they reduced mortality (RR 0.47; 95% CI 0.25 to 0.90; P = 0.02), cardiac mortality (RR 0.36; 95% CI 0.16 to 0.79; P = 0.01), and myocardial infarction (RR 0.66; 95% CI 0.46 to 0.94; P = 0.02). With regard to adverse effects, alpha-2 adrenergic agonists significantly increased perioperative hypotension (RR 1.32; 95% CI 1.07 to 1.62; P = 0.009) and bradycardia (RR 1.66; 95% CI 1.14 to 2.41; P = 0.008).

AUTHORS' CONCLUSIONS

Our study provides encouraging evidence that alpha-2 adrenergic agonists may reduce cardiac risk, especially during vascular surgery. Nonetheless, these data remain insufficient to make firm conclusions about their efficacy and safety. A large randomized trial of alpha-2 adrenergic agonists is therefore warranted. Additionally, future research must determine which specific alpha-2 adrenergic agonist should be used, and whether it is safe to combine them with other perioperative interventions (for example beta-adrenergic blockade).

Fibrinolytic and coagulation pathways after laparoscopic and open surgery: a prospective randomized trial

BACKGROUND

Tissue injury poses increased risk for postoperative thromboembolic complications. Laparoscopic surgery, by causing limited tissue injury, is associated with lower risk for thromboembolism than is open surgery. We conducted a prospective randomized study in order to detect potentially existing differences in activation of coagulation and fibrinolytic pathways between open and laparoscopic surgery.

METHODS

Forty patients with chronic cholelithiasis were randomly assigned to undergo open (group A) or laparoscopic cholecystectomy (group B). Blood samples were taken preoperatively, at the end of the procedure, and at 24 and 72 h postoperatively. Prothrombin time (PT), activated partial thromboplastin time (APTT), international normalized ratio (INR), platelets (PLT), soluble fibrin monomer complexes (F.S. test), fibrin degradation products (FDP), D-dimers (D-D), and fibrinogen (FIB) were measured and compared within each group and between groups: Thrombin-antithrombin complexes (TAT) and prothrombin fragments (F1 + 2) were measured at 24 and 72 h postoperatively.

RESULTS

Demographics were comparable between groups. Immediately postoperatively, TAT and F1 + 2 were significantly higher in group A (p < 0.05). They also increased significantly postoperatively as compared with preoperative levels within each group (p < 0.05). D-dimers were significantly higher in group A (p < 0.01) immediately postoperatively. D-dimers also increased significantly postoperatively in group B as compared with preoperative levels (p < 0.001). FIB decreased slightly in both groups at 24 h postoperatively but there was a significant increase in group A (p < 0.01). Soluble fibrin monomer complexes (SFMC) were detected twice in group A and only once in group B. FDP levels over 5 μg/ml were detected more often in group A (p < 0.05). There was not any case of thromboembolism or abnormal bleeding.

CONCLUSIONS

Open surgery leads to higher activation of the clotting system than do laparoscopic procedures. Although of a lower degree, hypercoagulability is still observed in patients undergoing laparoscopic surgery and therefore routine thromboembolic prophylaxis should be considered.

Alterations of hemostasis after laparoscopic and open surgery

BACKGROUND

After tissue injury caused by trauma or surgery, alterations of hemostasis are observed and there is a risk for postoperative thromboembolic complications. Laparoscopic surgery, by causing limited tissue injury, appears to be associated with a lower risk for thromboembolism than open surgery. We conducted a prospective randomized study in order to detect potentially existing differences in activation of coagulation and fibrinolytic pathways between open and laparoscopic surgery.

METHODS

Forty patients suffering from chronic cholelithiasis were randomly assigned to undergo open (group A n = 20) or laparoscopic cholecystectomy (group B n = 20) by the same surgical and anesthesiology team. Demographic data were comparable. Blood samples were taken (a) preoperatively, (b) at the end of the procedure, (c) 24 h postoperatively and (d) 72 h postoperatively. The following parameters were measured and compared within each group and between groups: platelets (PLT), soluble fibrin monomer complexes (SFMC), fibrin degradation products (FDP), D-dimers (D-D), fibrinogen (FIB), activated partial thromboplastin time (APTT), prothrombin time (PT). Thrombin-antithrombin III complexes (TAT) were measured at 24 and 72 h postoperatively. Prothrombin fragment 1 + 2 (F1 + 2) was measured at 24 and 72 h postoperatively in 11 patients of group A and 13 patients of group B, respectively.

RESULTS

Demographics were comparable between groups. Immediately postoperatively, TAT and F1 + 2 were significantly higher in group A as compared to group B (p < 0.05). They also increased significantly postoperatively as compared to preoperative levels within each group (p < 0.05). D-dimers were significantly higher in group A as compared to group B (p < 0.01) immediately postoperatively. D-dimers also increased significantly postoperatively in group B as compared to preoperative levels (p < 0.001). FIB decreased slightly in both groups at 24 h postoperatively but there was a significant increase in group A as compared to group B (p < 0.01). SFMC were detected twice in group A and only once group B. FDP levels over 5 mug/ml were detected more often in group A than in group B (p < 0.05). No patient from either group suffered thromboembolism or abnormal bleeding as a postoperative complication.

CONCLUSIONS

Open surgery as compared to laparoscopic procedures leads to activation of the clotting system of a higher degree. Although of a lower degree, hypercoagulability is still observed in patients undergoing laparoscopic surgery and, therefore, routine thromboembolic prophylaxis should be considered.

Haematological effects of anaesthetics and anaesthesia

Halothane is still unique in its ability to inhibit platelet aggregation and to increase bleeding time in vivo at clinical concentrations, although sevoflurane inhibits platelet aggregation induced by weak agonists. Propofol itself, but not its fat emulsion, inhibits platelet aggregation and suppresses calcium mobilization. Extradural anaesthesia has been shown to prevent hypercoagulability during the perioperative period. Aprotinin reduces both blood loss and the incidence of blood transfusion during major orthopaedic and cardiac surgery.

The effect of clonidine on perioperative blood coagulation

STUDY OBJECTIVE

To evaluate the influence of perioperative stress protection by clonidine on blood coagulation.

DESIGN

Prospective, randomized, double-blinded, placebo-controlled clinical trial.

SETTING

University hospital.

PATIENTS

50 patients scheduled for elective gynecoabdominal surgery.

INTERVENTIONS AND MEASUREMENTS

Patients were randomly assigned to control (placebo) or clonidine group (single intravenous clonidine dose; 4 microg/kg(-1) or 3 microg/kg(-1) for age >65 years). Three measurement time points were defined: before administration of placebo/clonidine and anesthesia induction, (t1; baseline measurement); after surgery, before emergence of anesthesia (t2); and at the first postoperative day, 24 hours after anesthesia induction (t3). Blood coagulation was analyzed at all time points measuring international normalized ratio, platelets, thrombin-antithrombin complex, von Willebrand factor, soluble thrombomodulin, d-dimers, plasminogen activator inhibitor 1, and Thrombelastograph analysis.

MAIN RESULTS

In the postoperative period (t2, t3), hypercoagulability was present in all patients compared with baseline measurements (t1) but without differences between the control and clonidine group. Regarding hematologic, laboratory blood coagulation, and Thrombelastograph parameters, there was no statistically and clinically relevant difference throughout the study period between the 2 groups. No hemodynamic adverse events of clonidine were observed in the perioperative period. Until day of discharge, no thrombotic or thromboembolic events were reported in both groups.

CONCLUSIONS

Preoperative administration of a single dose of clonidine has no effect on perioperative blood coagulation.

Thromboelastography for monitoring prolonged hypercoagulability after major abdominal surgery

Despite clinical and laboratory evidence of perioperative hypercoagulability, there are no consistent data evaluating the extent, duration, and specific contribution of platelets and procoagulatory proteins by in vitro testing. We tested the hypothesis that the parallel use of standard and abciximab-cytochalasin D-modified thromboelastography (TEG) can assess 7 days' postoperative hypercoagulability and can estimate the independent contribution of procoagulatory proteins and platelets. Thromboelastograms were performed before surgery, at the end of surgery, 6 h after surgery, and on postoperative days 1, 2, 3, and 7; they were analyzed for the reaction time and the maximal amplitude (MA). We calculated the elastic shear modulus of standard MA (G(t)) and modified MA (G(c)), which reflect total clot strength and procoagulatory protein component, respectively. The difference was an estimate of the platelet component (G(p)). There was a 10% perioperative increase of standard MA, corresponding to a 50% increase of G(t) (P < 0.0001) and an 86%-90% contribution of the calculated G(p) to G(t). We conclude that serial standard and modified thromboelastography may reveal prolonged postoperative hypercoagulability and the independent contribution of platelets and procoagulatory proteins to clot strength.

IMPLICATIONS

Postoperative hypercoagulability, occurring for at least 1 wk after major abdominal surgery, may be demonstrated by standard and modified thromboelastography. This hypercoagulability is not reflected by standard coagulation monitoring and seems to be predominantly caused by increased platelet reactivity.

Current trends in perioperative pain management

Wider use of optimized multimodal accelerated postoperative recovery programs require that anesthesiologists step out of traditional operating room anesthesia roles and even beyond current pain management consultant roles. Development of optimal postoperative recovery services requires close collaboration between anesthesiologists, surgeons, nurses, physical therapists, administrators, and others involved in the management of patients after surgery. Optimization of perioperative care is an ongoing process enhanced by clinical investigation; however, making significant improvements to clinical practice does not have to wait for additional research data, but should proceed now, with broader application of techniques known to enhance rehabilitation and recovery. Based on existing data, the challenges of developing perioperative recovery services seem likely to be rewarded with improved patient outcomes and reduced cost.

The stress response of critical illness

The integrated stress response to tissue trauma is crucial for the maintenance of homeostasis. An exaggerated or prolonged response may be detrimental in compromised patients. Knowledge of the involved afferent pathways will suggest therapeutic interventions that may modulate the intensity of the stress response. Described are these concepts as they relate to perioperative medicine.

Neuroendocrine stress hormones do not recreate the postoperative hypercoagulable state

Surgery causes changes in hemostasis, leading to a hypercoagulable state that has been linked to both arterial and venous thrombotic complications. The etiology of this state is unknown, but many investigators have hypothesized that perioperative neuroendocrine changes are responsible. We have previously demonstrated minimal increases in hemostatic function with a stress hormone infusion. This study was undertaken to further examine the relationship between neuroendocrine hormones and hemostatic function. Seventeen healthy volunteers were administered a stress hormone cocktail i.v. (epinephrine, cortisol, glucagon, angiotensin II, and vasopressin) for 24 h in a blind, placebo-controlled, cross-over design in our clinical research center. Venous blood samples were obtained for measurement of hemostatic function before the infusion and at 2, 8, and 24 h. There were no demonstrable increases in any measure of hypercoagulability. Alternatively, there was an increase in tissue plasminogen activator and protein C activity. These changes are consistent with an inhibition of coagulation and improved fibrinolysis. These data suggest that this combination of neuroendocrine hormones is not responsible for the postoperative hypercoagulable state.

IMPLICATIONS

Infusion of five stress hormones (epinephrine, cortisol, glucagon, vasopressin, and angiotensin II) to normal volunteers does not cause increases in procoagulant proteins and platelet reactivity or decreases in fibrinolytic proteins. Alternatively, these five hormones caused increased levels of fibrinolytic proteins (tissue plasminogen activator) and endogenous anticoagulants (protein C antigen and activity).

Comparison of the effect of intravenous ketoprofen, ketorolac and diclofenac on platelet function in volunteers

BACKGROUND

Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit prostaglandin synthesis which may result in impaired platelet function. Because NSAIDs have different abilities to inhibit cyclo-oxygenases we compared the effect of intravenous ketoprofen, ketorolac and diclofenac on platelet function in volunteers.

METHODS

Ten healthy male volunteers were given ketoprofen 1.4 mg x kg(-1), ketorolac 0.4 mg x kg(-1) and diclofenac 1.1 mg x kg(-1) in saline i.v. on three different occasions, at more than one-week intervals, in a randomized double-blind crossover study. Platelet function was evaluated before (sample 0), 2 (sample 2) and 24 h (sample 3) after the beginning of the infusion.

RESULTS

Two of the volunteers had no secondary platelet aggregation in their aggregation curves before the experiment (sample 0, studied three times) and their results were excluded from the final analysis. Diclofenac inhibited adrenaline (0.9 microg x m[-1]) induced platelet aggregation less (median maximal aggregation 22.5%) than ketoprofen (18.3%) and ketorolac (15.7%) (P<0.05) in sample 2. In the ketorolac group in sample 3 an impairment of adrenaline (0.9 microg x ml[-1]) induced platelet aggregation was still seen (26.7%) (P<0.05) but not in the other groups. Diclofenac did not affect adenosine diphosphate (ADP) induced platelet aggregation. However, ketorolac caused an impairment in ADP (3 microM and 6 microM) induced platelet aggregation and ketoprofen in ADP (6 microM) induced platelet aggregation in sample 2. Bleeding time was prolonged (P<0.05) after ketoprofen and ketorolac (sample 2) but not after diclofenac. Platelet retention on glass beads was unaffected by the tested drugs.

CONCLUSION

Ketoprofen, ketorolac and diclofenac caused a reversible platelet dysfunction. Diclofenac had the mildest effect, while platelet dysfunction was still seen 24 h after the beginning of ketorolac.

Intravenous ketorolac tromethamine worsens platelet function during knee arthroscopy under spinal anesthesia

Ketorolac prolongs bleeding time and inhibits platelet aggregation and platelet thromboxane production in healthy, awake volunteers. However, platelet function was recently shown not to worsen after ketorolac was given during general anesthesia. The purpose of this study was to investigate platelet function changes during a standardized spinal anesthetic and surgery, as well as after a single intraoperative dose of intravenous (IV) ketorolac. The study comprised 30 ASA physical status I patients undergoing spinal anesthesia for knee arthroscopy. Subjects were randomized to receive either ketorolac 60 mg IV 15 min after skin incision or placebo IV. Platelet function testing consisted of an Ivy bleeding time, platelet aggregometry with adenosine diphosphate (ADP) and collagen, thromboelastography (TEG), and serum thromboxane B2 (TxB2) assays. Platelet function testing was performed: 1) 15 min prior to the performance of spinal anesthesia; 2) 10 min after surgical skin incision; and 3) 45 min after administration of study drug. The placebo group demonstrated no changes in any platelet function variable during spinal anesthesia and surgery relative to preoperative values. The ketorolac group, however, demonstrated a significant increase in bleeding time from postincision to poststudy drug data points (213 +/- 60s to 275 +/- 85s, mean +/- SD; P < 0.01). Further, platelet aggregometry to collagen was diminished in the ketorolac group from preoperative to poststudy drug data points (90.8% +/- 7.6% to 60.5% +/- 32.5%; P < 0.01). Platelet aggregometry with ADP, however, was unchanged in the ketorolac group. Platelet TxB2 production decreased dramatically in the ketorolac group from preoperative to poststudy drug data points (157.2 +/- 129.4 to 0.3 +/- 0.3 ng/mL; P < 0.01). Platelet function does not appear to be accentuated during spinal anesthesia as it is during general anesthesia. Unlike during general anesthesia, platelet function during spinal anesthesia is impaired, with respect to bleeding time and platelet aggregometry to collagen, by a single intraoperative dose of IV ketorolac.

Intravenous ketorolac tromethamine does not worsen platelet function during knee arthroscopy under general anesthesia

Ketorolac (KT) prolongs bleeding time and inhibits platelet aggregation and platelet thromboxane production in healthy, awake volunteers. However, platelet function may be accentuated during the stress of general anesthesia (GA) and surgery. The purpose of this study was to investigate platelet function changes during a standard GA technique and surgery, as well as after a single intraoperative dose of intravenous (i.v.) KT. The study comprised 30 ASA physical status I patients undergoing GA for knee arthroscopy. Subjects were randomized to receive either KT 60 mg IV 15 min after skin incision or placebo i.v. Platelet function testing consisted of an Ivy bleeding time (BT), platelet aggregometry (PA) with adenosine diphosphate (ADP) and collagen, thromboelastography (TEG), and serum thromboxane B2 assays (TxB2). Platelet function testing was performed: 1) 15 min prior to the induction of GA, 2) 10 min after skin incision, and 3) 45 min after administration of study drug. BT decreased significantly in the placebo group from 263 +/- 133 s (mean +/- SD) preoperatively to 207 +/- 89 s postincision. BT did not change in the KT group. PA was unchanged after IV KT. TEG data was unchanged in both groups during anesthesia and surgery. TxB2 levels decreased markedly in the KT group from 106.9 +/- 96.2 ng/mL preoperatively to 0.4 +/- 1.2 ng/mL poststudy drug, P = 0.002. Platelet function appears to be accentuated during GA and surgery as evaluated by BT in the placebo group. Further, platelet function by BT, PA, and TEG was not inhibited after i.v. KT despite near complete abolition of TxB2 production.