Increased platelet, leukocyte, and endothelial cell activity are associated with increased coagulability in patients after total knee arthroplasty

Tourniquet use benefits to reduce intraoperative blood loss in patients receiving total knee arthroplasty for osteoarthritis: An updated meta-analysis with trial sequential analysis

PURPOSE

The efficacy and safety of tourniquets use during total knee arthroplasty (TKA) in patients with osteoarthritis remain debated. This updated systematic review and meta-analysis aimed to further evaluate the role of tourniquets use in patients undergoing TKA for knee osteoarthritis by introducing trial sequential analysis.

METHODS

PubMed, Embase, and the Cochrane Library were searched. We used the Cochrane risk of bias tool for quality assessment. Statistical heterogeneity across studies was evaluated using Cochran's Q and I2 statistic. Meta-analysis was performed using Stata/SE 14.0, and trail sequential analysis was performed using TSA software version 0.9.5.10 Beta. In addition, qualitative summary was also used to describe results.

RESULTS

15 randomized controlled trials (RCTs) involving 1202 patients were included in the meta-analysis. The pooled results showed that tourniquet use during TKA significantly reduced intraoperative blood loss (mean difference (MD)= -123.84, 95% confidence interval (CI): -163.37 to -84.32, p < .001)and shortened operation time (MD = -4.71, 95% CI: -7.6 to -1.82, p = .001), but there were no significant differences in postoperative blood loss, calculated blood loss, total blood loss, transfusion rate (p = .939), and deep venous thrombosis (DVT) rate between the tourniquet and no-tourniquet groups. TSA confirmed that the result of operation time was false positive, but the results of other outcomes were conclusive. The results of qualitative summary showed conflicting findings in terms of pain, range of motion (RoM) and swelling ratio between the two groups.

CONCLUSIONS

Tourniquet use in patients receiving TKA for osteoarthritis benefits to reduce intraoperative blood loss but has no effect on postoperative blood loss, calculated blood loss, total blood loss, operation time, transfusion rate, and DVT rate. In addition, it remains unclear the difference between the tourniquet and non-tourniquet groups in terms of pain, RoM and swelling ratio.

Perioperative Thromboprophylaxis Is Associated With Lower Risk of Venous Thromboembolism After Knee Arthroscopy

PURPOSE

To determine the rate of symptomatic venous thromboembolism (VTE) among patients undergoing arthroscopic knee procedures, risk factors associated with postoperative VTE, and current perioperative thromboprophylaxis prescription patterns associated with this population in the United States.

METHODS

Medical records for patients ≥18 years of age were queried from the Mariner database using Current Procedural Terminology codes for knee arthroscopy performed in the United States from 2010 to 2020 in this cross-sectional study. Patients who received thromboprophylaxis and those diagnosed with VTE, including deep-vein thrombosis or pulmonary embolism, within 90 days of surgery were identified using International Classification of Diseases and National Drug Codes. Two multivariable logistic regression models were used to identify VTE risk factors and likelihood of perioperative thromboprophylaxis. Covariates included procedure type, age, oral contraceptive pill (OCP) use, and medical comorbidities.

RESULTS

A total of 718,289 patients met inclusion criteria and 7,618 patients (1.06%) experienced VTE, including deep-vein thrombosis (n = 6,394, 0.9%) and/or pulmonary embolism (n = 2,211, 0.3%). A total of 10,769 patients (1.5%) filled perioperative thromboprophylaxis, including aspirin (n = 5,353, 0.7%), low-molecular-weight heparin (n = 4,563, 0.6%), and oral factor Xa inhibitors (n = 947, 0.1%). Perioperative thromboprophylaxis was associated with decreased odds of experiencing VTE (adjusted odds ratio [aOR] 0.65, 95% confidence interval [CI] 0.51-0.80). Procedure types categorized as moderate-to-greater risk were associated with increased odds of VTE (aOR 1.42, 95% CI 1.34-1.50). OCP use (aOR 1.63, 95% CI 1.38-1.91), obesity (aOR 1.17, 95% CI 1.11-1.24), renal disease (aOR 1.33, 95% CI 1.18-1.50) and congestive heart failure (aOR 1.30, 95% CI 1.13-1.50) were associated with increased odds of VTE.

CONCLUSIONS

While the overall rate of symptomatic VTE following knee arthroscopy remains low, procedure types that are more complex and generally require restrictive rehabilitation protocols, OCP use, obesity, renal disease, and congestive heart failure are associated with increased odds of postoperative VTE. Conversely, the use of perioperative thromboprophylaxis is associated with significantly lower VTE risk.

LEVEL OF EVIDENCE

III, retrospective comparative prognostic trial.

Effect of lower-leg trauma and knee arthroscopy on procoagulant phospholipid-dependent activity

Background

Lower-leg injury and knee arthroscopy are both associated with venous thromboembolism (VTE). The mechanism of VTE in both situations is unknown, including the role of procoagulant microparticles. This may provide useful information for individualizing thromboprophylactic treatment in both patient groups.

Objective

We aimed to study the effect of (1) lower-leg trauma and (2) knee arthroscopy on procoagulant phospholipid-dependent (PPL) activity plasma levels.

Methods

POT-(K)CAST trial participants who did not develop VTE were randomly selected for the current study. Plasma was collected shortly after lower-leg trauma or before and after knee arthroscopy. For aim 1, samples of 67 patients with lower-leg injury were compared with control samples (preoperative samples of 74 patients undergoing arthroscopy). Linear regression was used to obtain mean ratios (natural logarithm retransformed data), adjusted for age, sex, body mass index, infections, and comorbidities. For aim 2, pre- and postoperative samples of 49 patients undergoing arthroscopy were compared using paired t tests. PPL activity was measured using modified activated factor X-dependent PPL clotting assay.

Results

For aim 1, PPL activity levels were almost threefold higher in patients with lower-leg injury compared with controls, that is, mean ratio, 2.82 (95% confidence interval [CI], 1.98-4.03). For aim 2, postoperative PPL activity levels did not change significantly, that is, mean change, -0.72 mU/mL (95% CI, -2.03 to 0.59).

Conclusion

Lower-leg trauma was associated with increased plasma levels of PPL activity, in contrast to knee arthroscopy. Lower-leg trauma triggers the release of procoagulant microparticles.

Association of Use of Tourniquets During Total Knee Arthroplasty in the Elderly Patients With Post-operative Pain and Return to Function

Objective

During total knee arthroplasty (TKA), tourniquet may negatively impact post-operative functional recovery. This study aimed at investigating the effects of tourniquet on pain and return to function.

Methods

Pubmed, Embase, and Cochrane Library were comprehensively searched for randomized controlled trials (RCTs) published up to February 15th, 2020. Search terms included; total knee arthroplasty, tourniquet, and randomized controlled trial. RCTs evaluating the efficacies of tourniquet during and after operation were selected. Two reviewers independently extracted the data. Effect estimates with 95% CIs were pooled using the random-effects model. Dichotomous data were calculated as relative risks (RR) with 95% confidence intervals (CI). Mean differences (MD) with 95% CI were used to measure the impact of consecutive results. Primary outcomes were the range of motion (ROM) and visual analog scale (VAS) pain scores.

Results

Thirty-three RCTs involving a total of 2,393 patients were included in this study. The mean age is 65.58 years old. Compared to no tourniquet group, the use of a tourniquet resulted in suppressed ROM on the 3rd post-operative day [MD, −4.67; (95% CI, −8.00 to −1.35)] and the 1st post-operative month [MD, −3.18; (95% CI, −5.92 to −0.44)]. Pain increased significantly when using tourniquets on the third day after surgery [MD, 0.39; (95% CI, −0.19 to 0.59)]. Moreover, tourniquets can reduce intra-operative blood loss [MD, −127.67; (95% CI, −186.83 to −68.50)], shorter operation time [MD, −3.73; (95% CI, −5.98 to −1.48)], lower transfusion rate [RR, 0.85; (95% CI, 0.73–1.00)], higher superficial wound infection rates RR, 2.43; [(5% CI, 1.04–5.67)] and higher all complication rates [RR, 1.98; (95% CI, 1.22–3.22)].

Conclusion

Moderate certainty evidence shows that the use of a tourniquet was associated with an increased risk of higher superficial wound infection rates and all complication rates. Therefore, the findings did not support the routine use of a tourniquet during TKA.

Comparison of efficacy and safety of different tourniquet applications in total knee arthroplasty: a network meta-analysis of randomized controlled trials

OBJECTIVE

Total knee replacement (TKA) is an effective way to treat teratogenic and disabling knee diseases such as advanced osteoarthritis. Tourniquets are often used in TKA to reduce bleeding and to get a better visualization of the surgical field, while it is related to safety concerns. We did this network meta-analysis to comprehensively compare the efficacy and safety of various tourniquet application strategies.

METHOD

PubMed, Embase, Cochrane Library, CNKI, and WanFang Database were systematically searched from January 1990 to May 2020. A network meta-analysis with a frequentist framework was done to assess the relative efficacy and safety by comparing seven clinical important endpoints.

RESULTS

38 eligible studies that assessed 3007 participants who underwent TKA were included in this network meta-analysis. Tourniquet inflation before osteotomy then deflation after wound closure effectively reduce perioperative bleeding (WMD compared with control group -234.66, 95% CI [-409.19 to -60.13]), while shortening the operation time (WMD -8.98, 95%CI [-14.07 to -3.88]) and reducing postoperative complications, including DVT (OR -0.58, 95%CI [-1.19 to 0.03]) and minor wound complications (OR -1.38, 95%CI [-3.00 to 0.25]). No difference was found in the late postoperative knee pain and function outcomes.

CONCLUSIONS

Using tourniquets during the entire operation can effectively reduce blood loss, but it also can cause many safety problems, including DVTs, wound oozing, delayed healing, and serious wound complications. Tourniquet inflation before osteotomy then deflation after wound closure effectively can reduce perioperative bleeding while shortening the operation time and reducing postoperative complications, so it could be the ideal tourniquet application strategy in TKA.Key messagesThis is the first study that comprehensively compared different tourniquet application strategies to evaluate their impact on postoperative recovery following TKA, and five clinically important endpoints were assessed in this study: perioperative blood loss, operation time, postoperative pain and function, and complications.We conclude that tourniquet inflation before osteotomy then deflation after wound closure could be the ideal tourniquet application strategy in TKA.

Impact of tourniquet on short-term outcomes in opening wedge high tibial osteotomy with modern tranexamic acid protocols: a retrospective cohort study

BACKGROUND

The use of a tourniquet during high tibial osteotomy (HTO) is a routine procedure, but there is currently no research on the benefits and potential risks of tourniquet use during HTO. The aim of this study was to investigate the impact of tourniquet on perioperative blood loss, early functional recovery and complications in opening wedge HTO with modern tranexamic acid protocols.

METHODS

This was a retrospective cohort study of patients who underwent unilateral opening wedge HTO between January 2019 and September 2020. All patients were divided into two groups according to whether a tourniquet was applied during HTO. Patients in both groups received the same surgical procedures, tranexamic acid protocols and other perioperative treatments. Preoperative baseline data, intraoperative data, early postoperative recovery and all complications during the 3-month follow-up were collected and compared between the two groups.

RESULTS

A total of 62 patients were enrolled in this study, including 32 in the tourniquet group and 30 in the non-tourniquet group. There was no significant difference in preoperative baseline data between the two groups (P > 0.05 in all). Intraoperative blood loss in the tourniquet group was significantly lower than that in the non-tourniquet group (80.22 ml versus 94.00 ml, P < 0.001), but there was no difference in total blood loss (187.39 ml versus 193.31 ml, P = 0.714). And no patient in either group required blood transfusion. In terms of early postoperative recovery, tourniquet use significantly increased pain scores and reduced knee range of motion on the first and second postoperative days, but there was no significant difference between the two groups at postoperative third day and third month. Furthermore, there was no significant difference between the two groups in terms of lower limb force line correction, length of stay, Knee Society Score or the incidence of complications during the 3-month follow-up (P > 0.05 in all).

CONCLUSIONS

In opening wedge HTO with modern tranexamic acid protocols, not using a tourniquet does not increase perioperative total blood loss or the risk of complications, but facilitates early postoperative recovery by reducing pain and increasing range of motion.

Medium-Term Clinical Results of High-Flexion Knee Prostheses in Patients with Rheumatoid Arthritis

Objective

This study was performed to evaluate the function and satisfaction outcome of patients with rheumatoid arthritis (RA) who underwent total knee arthroplasty (TKA) with high‐flexion prostheses.

Materials and methods

Twenty‐two patients (35 knees) using high‐flexion prostheses (Zimmer, Warsaw, IN) were followed up for a period of 7–11 years from February 2007 to December 2009. Clinical and radiographic follow‐up was performed using Hospital for Special Surgery (HSS), Short‐Form 36 scores (SF‐36), American Knee Society score (KSS), and Knee Society Total Knee Arthroplasty Roentgenographic Evaluation and Scoring System. Patient satisfaction assessments took place at the final follow‐up sessions using the Marsh Satisfaction Questionnaire.

Results

The average ROM improved from preoperative 68.43° ± 33.78° to 95.54° ± 7.03° at the final follow‐up. The HSS score and KSS score for pain improved from (46.49 ± 12.73) points to (85.46 ± 3.90) points and from 20.57 ± 5.91 points to 47.43 ± 3.51 points at the follow‐up evaluation, respectively. Physical Component Summary(PCS) and Physical Component Summary (MCS) scores were 45.38 and 52.56, respectively by the end of follow‐up. Deep venous thrombosis developed in one patient and one patient required surgical revision due to infection. There were no instances of prosthetic loosening. The satisfaction rate of patients was 95.5%.

Conclusion

Although this particular model of TKA did not yield high‐flexion angles (ie, 140°) required for kneeling, squatting, or rising from the floor, significant clinical and radiographic gains were evident in these patients with RA.

A preliminary study to assess neutrophil and endothelial response to knee arthroplasty with the use of a tourniquet : effects of spinal or sevoflurane anesthesia

Background : During orthopedic surgery, the use of a pneumatic tourniquet results in side effects secondary to ischemia-reperfusion phenomena. We tested the hypothesis that total knee arthroplasty with a tourniquet is associated with increase in plasma concentrations of biomarkers of neutrophil activation and endothelial injury. The second aim was to compare these changes during spinal or general inhalational anesthesia. Methods : 40 adult ASA I-II patients scheduled for total knee arthroplasty with a tourniquet under spinal or sevoflurane anesthesia were included. Venous blood samples were collected before surgery, 1 h, 3 h, and 24 h after tourniquet deflation. To assess neutrophil activation, plasma concentrations of total and active fractions of myeloperoxidase, as well as elastase concentrations and proteolytic activity were measured. Endothelial injury was assessed by measurement of plasma concentrations of syndecan-1, soluble thrombomodulin, soluble E-selectin, and vascular endothelial growth factor. Results were analyzed with a two-way analysis of variance. P< 0.05 was considered statistically significant. Results : Plasma concentrations of active but not total myeloperoxidase and elastase significantly increased following tourniquet deflation. The level of syndecan-1, soluble thrombomodulin, soluble E-selectin, but not vascular endothelial growth factor, significantly decreased postoperatively. These changes of biomarkers were similar during spinal and sevoflurane anesthesia. Conclusions : Total knee arthroplasty with pneumatic tourniquet is associated with systemic release of markers of neutrophil activation which was comparable during spinal or sevoflurane anesthesia. Systemic expression of endothelial injury was not detected in our clinical conditions.

Effects of tourniquet use on clinical outcomes and cement penetration in TKA when tranexamic acid administrated: a randomized controlled trial

Background

The role of a tourniquet is still controversial for patients undergoing total knee arthroplasty (TKA). Our current study was performed to determine whether the nonuse of the tourniquet combine with tranexamic acid (TXA) application in TKA patients with end-stage osteoarthritis would accelerate the perioperative recovery rate and provide enough cement mantle thickness for implant fixation.

Methods

In this prospective, randomized controlled trial, 150 end-stage knee osteoarthritis patients receiving TKA were divided into three groups: group A (tourniquet group), group B (non-tourniquet group), and group C (tourniquet in cementation group). All enrolled patients received 3 g of intravenous TXA and 1 g topical TXA. The primary outcomes included blood loss variables and transfusion values. The secondary outcomes included VAS pain score, inflammatory factors level, range of motion, HSS score, postoperative hospital stay, and complication. Furthermore, by using a digital linear tomosynthesis technique, tibial baseplate bone cement mantle thickness was measured in four zones based on the knee society scoring system.

Results

No significant difference was found among the three groups with regards to total blood loss, transfusion, and complication. However, patients in group B showed lower inflammatory factors levels, shorter length of hospital stay, better range of motion, and lower postoperative pain. No significant difference was found among the three groups in four zones in terms of bone cement mantle thickness.

Conclusions

For end-stage knee osteoarthritis patients, the absence of tourniquet did not appear to affect blood loss and cement penetration in TKA patients. Furthermore, less inflammation reaction and better knee function can be achieved without a tourniquet. We recommend no longer use a tourniquet in primary TKA for patients with end-stage osteoarthritis when TXA is administrated.

Trial registration

ChiCTR-INR-16009026.

Level of evidence

Therapeutic Level I.

Does tourniquet use affect the periprosthetic bone cement penetration in total knee arthroplasty? A meta-analysis

BACKGROUND

A tourniquet is a device commonly used to control massive hemorrhage during knee replacement surgery. However, the question remains whether the use of tourniquets affects the permeability of the bone cement around the knee prosthesis. Moreover, the long-term effects and stability of the knee prosthesis are still debatable. The aim of this study was to examine whether the use of a tourniquet increases the thickness of the cement mantle and affects the postoperative blood loss and pain during primary total knee arthroplasty (TKA) using meta-analysis.

METHODS

We searched the Cochrane Central Library, MEDLINE, Embase, PubMed, CNKI, and Wang Fang databases for randomized controlled trials (RCTs) on primary TKA, from inception to November 2019. All RCTs in primary TKA with and without a tourniquet were included. The meta-analysis was conducted using RevMan 5.2 software.

RESULTS

A total of eight RCTs (677 knees) were analyzed. We found no significant difference in the age and sex of the patients. The results showed that the application of tourniquet affects the thickness of the bone cement around the tibial prosthesis (WMD = 0.16, 95%CI = 0.11 to 0.21, p < 0.00001). However, in our study, there was no significant difference in postoperative blood loss between the two groups was observed (WMD = 12.07, 95%CI = - 78.63 to 102.77, p = 0.79). The use of an intraoperative tourniquet can increase the intensity of postoperative pain (WMD = 1.34, 95%, CI = 0.32 to 2.36, p = 0.01).

CONCLUSIONS

Tourniquet application increases the thickness of the bone cement around the prosthesis and may thus increase the stability and durability of the prosthesis after TKA. The application of an intraoperative tourniquet can increase the intensity of postoperative pain.

More pain and slower functional recovery when a tourniquet is used during total knee arthroplasty

PURPOSE

Although a tourniquet can effectively control intraoperative blood loss and offer clear surgical field in total knee arthroplasty (TKA), its optimal usage has been controversial. The aim of this research was to perform a systematic review and meta-analysis to compare and explore the best application of a tourniquet in TKA.

METHODS

MEDLINE, PubMed, EMBASE, the Cochrane Library, Wanfang database, and Web of Science were searched for randomized controlled trials (RCTs) comparing the four different strategies of tourniquet application in TKA. In Group I, a tourniquet was not used and was called the non-tourniquet (NT) group. In Group II, a tourniquet was only used during the cementation of implants and was called the specific duration tourniquet (SDT) group. In Group III, the tourniquet was only released before wound closure to control the bleeding sources and was called the majority duration tourniquet (MDT) group. In Group IV, a tourniquet was used throughout the procedure, from skin incision to wound closure and was called the whole duration tourniquet (WDT) group.

RESULTS

Forty-six RCTs were included in this systematic review and meta-analysis. In a comparison between the NT and WDT groups (25 RCTs), intraoperative blood loss (IBL) (P = 0.0001) and range of motion (ROM) (P = 0.0001) were significantly increased in the NT group, while the visual analog score (VAS) (P = 0.0001), rate of deep vein thrombosis (DVT) (P = 0.01), and all complications (AC) (P = 0.0001) were significantly decreased in the NT group. In a comparison between the SDT and WDT groups (10 RCTs), IBL (P = 0.0001), TBL (P = 0.009), and ROM (P = 0.0001) were significantly increased in the SDT group, while thigh pain (P = 0.04) and the rate of DVT (P = 0.03) were significantly decreased in the SDT group. There were no significant differences between the MDT and WDT groups (12 RCTs) except for the rate of all complications (P = 0.01).

CONCLUSION

Despite the decrease in IBL with a tourniquet, no difference was found in TBL. In conclusion, not using a tourniquet or only using it during the cementation of implants was preferable based on the faster functional recovery, lower rate of DVTs and complications compared with using a tourniquet throughout the TKA procedure.

LEVEL OF EVIDENCE

I.

Effect of remote ischaemic conditioning on coagulation function as measured by whole blood impedance aggregometry and rotational thromboelastometry in off-pump coronary artery bypass surgery: A randomised controlled trial

INTRODUCTION

Remote ischaemic conditioning (RIC) has been shown to prevent platelet activation during ablation for atrial fibrillation. RIC has also been associated with more postoperative transfusion in the off-pump coronary artery bypass graft surgery (OPCAB) patients. We evaluated the effects of RIC on coagulation function in OPCAB patients.

METHODS

A total of 58 patients undergoing OPCAB were randomised to the RIC or control group. In the RIC group, four cycles of 5 min of ischaemia and 5 min of reperfusion were applied twice to the upper arm after the induction of anaesthesia (preconditioning), and after the completion of coronary anastomoses (postconditioning). Whole blood impedance aggregometry (Multiplate®) and rotational thromboelastometry (ROTEM®) were performed before the induction of anaesthesia, at the end of surgery, and at postoperative day 1.

RESULTS

The trend towards a decrease in adenosine diphosphate-induced whole blood aggregation at the end of surgery was greater in the RIC group than in the control group, but this effect was not statistically significant (-10.4 [18.1] vs. -5.7 [24.8] U, P = 0.424). In ROTEM® analysis, the EXTEM area under the velocity curve was lower in the RIC group than in the control group at the end of surgery (3567 [1399-5794] vs. 5693 [4718-6179] mm∗100, respectively; P = 0.030). A tendency of larger perioperative blood loss was identified in the RIC group.

CONCLUSIONS

Although some parameters indicated a tendency for hypocoagulation in the RIC group at the end of surgery, most effects were not statistically significant. RIC does not significantly affect perioperative platelet aggregability and coagulation in patients undergoing OPCAB.

The effects of tourniquet use on blood loss in primary total knee arthroplasty for patients with osteoarthritis: a meta-analysis

Background

The tourniquet is a common medical instrument used in total knee arthroplasty (TKA). However, there has always been a debate about the use of a tourniquet and there is no published meta-analysis to study the effects of a tourniquet on blood loss in primary TKA for patients with osteoarthritis.

Methods

We performed a literature review on high-quality clinical studies to determine the effects of using a tourniquet or not on blood loss in cemented TKA. PubMed, Web of Science, MEDLINE, Embase, and the Cochrane Library were searched up to November 2018 for relevant randomized controlled trials (RCTs). We conducted a meta-analysis following the guidelines of the Cochrane Reviewer’s Handbook. We used the Cochrane Collaboration’s tool for assessing the risk of bias of each trial. The statistical analysis was performed with Review Manager statistical software (version 5.3).

Results

Eleven RCTs involving 541 patients (541 knees) were included in this meta-analysis. There were 271 patients (271 knees) in the tourniquet group and 270 patients (270 knees) in the no tourniquet group. The results showed that using a tourniquet significantly decreased intraoperative blood loss (P < 0.002), calculated blood loss (P < 0.002), and the time of operation (P < 0.002), but tourniquet use did not significantly decrease postoperative blood loss (P > 0.05), total blood loss (P > 0.05), the rate of transfusion (P > 0.05), and of deep vein thrombosis (DVT) (P > 0.05) in TKA.

Conclusions

Using a tourniquet can significantly decrease intraoperative blood loss, calculated blood loss, and operation time but does not significantly decrease the rate of transfusion or the rate of DVT in TKA. More research is needed to determine if there are fewer complications in TKA without the use of tourniquets.

The effect of red blood cell transfusion on platelet function in critically ill patients

INTRODUCTION

Red blood cell (RBC) transfusion is associated with an increased risk of pro-thrombotic events, but the underlying mechanism is poorly understood. We hypothesized that RBC transfusion modulates platelet activity in critically ill patients with and without sepsis.

METHODS

In a prospective cohort study, 37 critically ill patients receiving a single RBC unit to correct for anemia were sampled prior to and 1 h after transfusion. Platelet exposure of P-selectin, CD63 and binding of PAC-1 as well as formation of platelet-leukocyte complexes were measured by flow cytometry. The ability of plasma from critically ill patients to induce ex vivo platelet aggregation was assessed by flow cytometry after incubation with platelets from a healthy donor.

RESULTS

RBC transfusion neither triggered the expression of platelet activation markers nor the formation of platelet-leukocyte complexes. Plasma from critically ill patients induced more spontaneous platelet aggregation prior to RBC transfusion compared to healthy controls, which was further augmented following RBC transfusion. Also collagen-induced platelet aggregation was already increased prior to RBC transfusion compared to healthy controls, and this response was unaffected by RBC transfusion. In contrast, ristocetin-induced platelet agglutination was decreased when compared to controls, suggesting impaired vWF-dependent platelet agglutination, even in the presence of high vWF levels. Following RBC transfusion, ristocetin-induced platelet agglutination further decreased. There were no differences between septic and non-septic recipients in all assays.

CONCLUSION

Ex vivo platelet aggregation is disturbed in the critically ill. Transfusion of a RBC unit may further increase the spontaneous platelet aggregatory response.

Changes in platelet Bax levels contribute to impaired platelet response to thrombin after cardiopulmonary bypass: prospective observational clinical and laboratory investigations

Background

Anucleate platelets can undergo apoptosis in response to various stimuli, as do nucleated cells. Cardiopulmonary bypass (CPB) causes platelet dysfunction and can also activate platelet apoptotic pathways. We therefore evaluated time-dependent changes in blood platelet Bax (a pro-apoptotic molecule) levels and platelet dysfunction after cardiac surgery.

Methods

We assessed blood samples obtained from subjects having on-pump or off-pump coronary artery bypass graft surgery ( n =20 each). We also evaluated the in vitro effects of platelet Bax increase in eight healthy volunteers.

Results

Thrombin-induced platelet calcium mobilisation and platelet-surface glycoprotein Ib (GPIb) expression were lowest at weaning from CPB and did not recover on postoperative day one. On-pump surgery increased platelet expression of Bax, especially the oligomerised form, along with translocation of Bax from the cytosol to mitochondria and platelet-surface tumour necrosis factor-alpha (TNF-α)-converting enzyme (TACE) expression. In contrast, mitochondrial cytochrome c expression was reduced. While similar in direction, the magnitude of the observed changes was smaller in patients having off-pump surgery. In vitro , a cell-permeable Bax peptide increased platelet Bax expression to the same extent seen during bypass and produced similar platelet changes. These apoptotic-like changes were largely reversed by Bcl-xL pre-administration, and were completely reversed by combined application of inhibitors that stabilise outer mitochondrial membrane permeability and TACE.

Conclusions

CPB increases platelet Bax expression, which contributes to reduced platelet-surface GPIb expression and thrombin-induced platelet calcium changes. These changes in platelet apoptotic signalling might contribute to platelet dysfunction after CPB.

Clinical trial registration

UMIN Clinical Trials Registry (number UMIN000006033).

The role of platelet hyperreactivity in venous thromboembolism after total knee arthroplasty in elderly population without pharmacologic prophylaxis: A single-center study

INTRODUCTION

While it is suggested that platelet hyperreactivity plays a role in the arterial thrombi, its link with venous thromboembolism (VTE) is not well defined. Aggregometry using low concentrations of agonists is proposed as a reliable method to detect hyperreactivity. The aim of this study was to examine whether platelet hyperreactivity affects the development of VTE after total knee arthroplasty (TKA).

METHODS

Total 150 elderly patients without VTE history were enrolled. Mechanical prophylaxis was used for VTE after TKA. We performed platelet aggregation using Chrono-log (Chrono-log Corporation, USA) in the presence of low concentrations of ADP (1.0 μmol/L) and epinephrine (0.4, 1.0 μmol/L), and measured maximal aggregation (%).

RESULTS

At 0.4 μmol/L epinephrine, 69.3%, 15.3%, and 15.3% displayed low (<40%), moderate (40-60%), and high (>60%) levels of aggregation, respectively. The proportion of high level of aggregation was 36.7%, 30.7% at 1.0 μmol/L of epinephrine and ADP, respectively. The incidence of VTE was higher in the moderate/high aggregation group (10/46, 21.7%) than in the low aggregation group (1/104, 1.0%) at 0.4 μmol/L epinephrine (P < 0.0001). In predicting postoperative VTE, sensitivity and specificity of ≥40% aggregation at 0.4 μmol/L epinephrine were 90.9% and 74.1%. Higher mean platelet volume and lower volume of blood loss were seen in the high aggregation group than in the low aggregation group.

CONCLUSION

Aggregation response to 0.4 μmol/L epinephrine is an optimal assay to classify platelet activity. Platelet hyperreactivity may increase the risk of postoperative VTE in an elderly population, and can be an indication of pharmacologic prophylaxis.

Comparison of tourniquet application only during cementation and long-duration tourniquet application in total knee arthroplasty: a meta-analysis

Background

Tourniquet is widely used by orthopedic surgeons in total knee arthroplasty (TKA). However, there are still controversies on the optimal timing of tourniquet application. The aim of this meta-analysis was to compare the effect and safety of tourniquet application only during cementation with long-duration tourniquet application in TKA.

Methods

An electronic literature search of PubMed, the Cochrane library, Embase, and Web of Science was conducted in July 2017. All randomized controlled trials (RCTs) comparing tourniquet application only during cementation with long-duration tourniquet application in TKA were included. RevMan 5.3 software was selected to perform the meta-analysis.

Results

Seven studies involving 440 TKAs were included for meta-analysis. The results suggested that although significant less intraoperative and total blood loss were observed with long-duration tourniquet application, tourniquet application only during cementation would not increase the number of transfusion and operation time. Tourniquet application only during cementation results in less knee pain on post-operative day 1 (POD 1), less time needed to achieve straight-leg raise, and less minor complications following TKA.

Conclusions

Tourniquet application only during cementation might reduce the rate of minor complications and have faster functional recovery during the early rehabilitation period following TKA, but it could not limit intraoperative and total blood loss. No definitive conclusions can be drawn based on the current evidences. Further, large well-designed RCTs with extensive follow-up are still needed to validate this research.

Platelets, inflammation and tissue regeneration

Blood platelets have long been recognised to bring about primary haemostasis with deficiencies in platelet production and function manifesting in bleeding while upregulated function favourises arterial thrombosis. Yet increasing evidence indicates that platelets fulfil a much wider role in health and disease. First, they store and release a wide range of biologically active substances including the panoply of growth factors, chemokines and cytokines released from α-granules. Membrane budding gives rise to microparticles (MPs), another active participant within the blood stream. Platelets are essential for the innate immune response and combat infection (viruses, bacteria, micro-organisms). They help maintain and modulate inflammation and are a major source of pro-inflammatory molecules (e.g. P-selectin, tissue factor, CD40L, metalloproteinases). As well as promoting coagulation, they are active in fibrinolysis; wound healing, angiogenesis and bone formation as well as in maternal tissue and foetal vascular remodelling. Activated platelets and MPs intervene in the propagation of major diseases. They are major players in atherosclerosis and related diseases, pathologies of the central nervous system (Alzheimers disease, multiple sclerosis), cancer and tumour growth. They participate in other tissue-related acquired pathologies such as skin diseases and allergy, rheumatoid arthritis, liver disease; while, paradoxically, autologous platelet-rich plasma and platelet releasate are being used as an aid to promote tissue repair and cellular growth. The above mentioned roles of platelets are now discussed.

Influence of tourniquet use in primary total knee arthroplasty with drainage: a prospective randomised controlled trial

Background

We aimed to compare the effect of tourniquet use or lack of it on recovery following uncomplicated primary total knee arthroplasty (TKA).

Methods

In a prospective randomised double-blinded study, 150 patients undergoing primary TKA were assigned to either a tourniquet or non-tourniquet group. At the early phase, 3 and 6 months after surgery, an independent observer assessed the primary outcome measure (i.e. total blood loss) and secondary outcome measures (i.e. wound complications, visual analogue scale pain score and knee range of motion).

Results

The tourniquet group exhibited reduced intraoperative blood loss (215.7 ± 113.7 ml vs. 138.6 ± 93.9 ml, P < 0.001) and shorter operating time (77.2 ± 14.5 min vs. 82.0 ± 12.7 min, P = 0.038). However, the non-tourniquet group showed less postoperative blood loss (180.2 ± 117.0 ml vs. 253.7 ± 144.2 ml, P = 0.001) and drainage volume (89.2 ± 66.3 ml vs. 164.5 ± 97.8 ml, P = 0.004), less thigh pain (all P < 0.001) in the initial 3 weeks, better knee range of motion (ROM) in the initial 3 days (day 1 81.6 ± 17.1 vs. 75.95 ± 14.55, P = 0.036; day 3 99.8 ± 13.7 vs. 93.95 ± 11.15, P = 0.005) and fewer wound tension vesicles (10.3 vs. 29.2%, P = 0.005). Earlier straight-leg raising (4.6 ± 3.8 h vs. 6.4 ± 4.3 h, P = 0.01) and shorter length of stay (6.3 ± 1.7 days vs. 7.1 ± 1.9 days, P = 0.001) were found in the non-tourniquet group. Similar total blood loss and blood transfusion rate were observed for both groups. All other parameters revealed no significant differences.

Conclusions

Our study suggests that a non-tourniquet TKA would lead to early rehabilitation without increasing side effects.

Trial registration

Chinese Clinical Trials Registry, ChiCTR-IOR-16007851, 1/29/2016

Tourniquet use during total knee arthroplasty does not modulate the neutrophil-to-lymphocyte ratio, pain, or activity

Abstract

The purpose of our study was to identify the influence of tourniquet use during total knee arthroplasty (TKA) on the neutrophil-to-lymphocyte ratio (NLR) shortly after surgery and patient-reported outcomes (pain and physical activity) from outpatient physical therapy. This retrospective study consisted of 104 subjects who underwent primary unilateral TKA (51 subjects with and 53 subjects without tourniquet assistance) between 2010 and 2012. The NLR was calculated from the absolute neutrophil and lymphocyte counts obtained immediately before and after (1 and 2 days) knee arthroplasty. The Knee Outcome Survey (KOS) of Activities of Daily Living and numeric pain scores collected at the first [33.0 (34.2) days after surgery] and last [85.5 (40.7) days after surgery] outpatient physical therapy visits were extracted from an electronic database. The NLR, pain, and KOS score were not significantly (all p > 0.05) different with tourniquet use. Based on these findings, we conclude that tourniquet use during TKA neither increases systemic inflammation shortly after surgery nor impairs patient-reported outcomes obtained during outpatient physical therapy.

Level of evidence

IV.

A single-centre study of haemostatic outcomes of joint replacement in von Willebrand disease and control patients and an analysis of the literature

INTRODUCTION

Haemostatic assessments of patients with von Willebrand disease (VWD) who undergo total knee arthroplasty (TKA) and total hip arthroplasty (THA) have mainly relied on subjective parameters.

AIMS

To compare objective haemostatic outcomes of TKA/THA in VWD patients and controls without bleeding disorders.

METHODS

We retrospectively analysed haemostatic outcomes in VWD patients undergoing TKA/THA from 1993 to 2011 and compared them with two matched controls per operation. Using one-way analysis of variance, we tested the effect of VWD on bleeding risk after TKA and THA.

RESULTS

Twelve VWD patients (6 type 1, 3 type 2M, 1 each of types 2A/2B/3) undergoing 19 operations (12 TKA, 7 THA) were matched to 38 controls. One (5%) of 19 operations in VWD patients and none of the control operations met clinical criteria for major bleeding. Baseline and postoperative day 1 haemoglobin levels, postoperative blood loss, transfused red blood cells (RBCs) and mean hospitalization days were not significantly different. More VWD patients than controls received RBC transfusions [12 (63%) vs. 12 (32%)]. Only 9 (47%) VWD patients vs. 38 (100%) controls received pharmacologic VTE prophylaxis. No postoperative symptomatic VTE occurred in either group.

CONCLUSION

In this largest, single-institutional study, von Willebrand factor replacement based on daily levels resulted in low frequency of major bleeding in VWD patients after TKA/THA. RBC transfusion was more frequent compared with matched controls, but other objective measures of haemostasis were similar. Lack of sufficient details in published reports precluded comparison of haemostatic outcomes.

Platelet-Monocyte Aggregates and C-Reactive Protein are Associated with VTE in Older Surgical Patients

Emerging evidence implicates platelets as key mediators of venous thromboembolism (VTE). Nevertheless, the pathways by which platelets and circulating procoagulant proteins synergistically orchestrate VTE remain incompletely understood. We prospectively determined whether activated platelets and systemic procoagulant factors were associated with VTE in 32 older orthopedic surgery patients. Circulating platelet-monocyte aggregates (PMAs), p-selectin expression (P-SEL), and integrin αIIbβ3 activation (PAC-1 binding) were assessed pre-operatively and 24 hours post-operatively. The proinflammatory and procoagulant molecule C-reactive protein (CRP), which induces PMA formation in vitro, along with plasma d-dimer and fibrinogen levels were also measured. The primary outcome was VTE occurring within 30 days post-operatively. Overall, 40.6% of patients developed VTE. Patients with VTE had a significant increase in circulating PMAs and CRP post-operatively, compared to those without VTE. Changes in PMA and CRP in VTE patients were significantly correlated (r² = 0.536, p = 0.004). In contrast, P-SEL expression and PAC-1 binding, fibrinogen levels, and d-dimers were not associated with VTE. This is the first study to identify that increased circulating PMAs and CRP levels are early markers associated with post-surgical VTE. Our findings also provide new clinical evidence supporting the interplay between PMAs and CRP in patients with VTE.

Tourniquet application during anesthesia: "What we need to know?"

Tourniquets are routinely and safely used in limb surgeries throughout the world. Tourniquet application alters normal physiology. Healthy patients tolerate these physiological changes well, but the physiological changes may not be well-tolerated by patients with poor cardiac function. This review discusses the physiological changes associated with tourniquet use, safe practice and provides the latest updates regarding tourniquet use. A systematic literature search of PubMed, MEDLINE, ScienceDirect, and Google Scholar was done. The search results were limited to the randomized controlled trials and systemic reviews. The papers are summarized in this review.

Nonclinical aspects of venous thrombosis in pregnancy

Pregnancy is a hypercoagulable state which carries an excess risk of maternal venous thrombosis. Endothelial injury, alterations in blood flow and activation of the coagulation pathway are proposed to contribute to the hypercoagulability. The risk for thrombosis may be accentuated by certain drugs and device implants that directly or indirectly affect the coagulation pathway. To help ensure that these interventions do not result in adverse maternal or fetal outcomes during pregnancy, gravid experimental animals can be exposed to such treatments at various stages of gestation and over a dosage range that would identify hazards and inform risk assessment. Circulating soluble biomarkers can also be evaluated for enhancing the assessment of any increased risk of venous thrombosis during pregnancy. In addition to traditional in vivo animal testing, efforts are under way to incorporate reliable non-animal methods in the assessment of embryofetal toxicity and thrombogenic effects. This review summarizes hemostatic balance during pregnancy in animal species, embryofetal development, biomarkers of venous thrombosis, and alterations caused by drug-induced venous thrombosis.

Risk of venous thrombosis after arthroscopy of the knee: results from a large population-based case-control study

BACKGROUND

From the currently available evidence, the risk of venous thrombosis after knee arthroscopy remains unclear.

OBJECTIVES

To estimate the risk of venous thrombosis after arthroscopy of the knee, and to identify high-risk groups.

PATIENTS AND METHODS

We used data from a large population-based case-control study (the Multiple Environmental and Genetic Assessment of risk factors for venous thrombosis [MEGA] study) on the etiology of venous thrombosis (4416 cases; 6150 controls). Odds ratios (ORs) with 95% confidence intervals (CIs), adjusted for age, sex, body mass index, rheumatic disease, and regular exercise, were calculated.

RESULTS

One hundred and three patients and 24 controls had a knee arthroscopy in the year before the index date, resulting in a six-fold increased risk (OR 5.9, 95% CI 3.7-9.3). Ligament reconstructions led to a higher risk (OR 17.2, 95% CI 2.2-136) than meniscal surgery, diagnostic arthroscopy, or chondroplasty (OR 5.4, 95% CI 3.4-8.7). An additionally increased risk was found for combinations with genetic and acquired risk factors: with oral contraceptives (OR 46.6, 95% CI 6.1-353); and with factor V Leiden, factor II G20210A mutation, or non-O blood type (OR 15.3, 95% CI 8.1-28.5). The risk of venous thrombosis was particularly high in the first 3 months after knee arthroscopy, with an 18-fold increased risk (OR 16.2, 95% CI 7.8-33.7).

CONCLUSIONS

We observed a strongly increased risk of venous thrombosis after knee arthroscopy, especially in the first months after the procedure. The risk was particularly high in the presence of other acquired or genetic risk factors, making knee arthroscopy a high-risk intervention in certain individuals.

Use of a tourniquet in total knee arthroplasty: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

A tourniquet is commonly used in total knee arthroplasty (TKA). However, the effectiveness and safety of tourniquets are debated. We performed this study to investigate whether patients benefit from the use of tourniquets in TKA.

METHODS

The literature search was conducted using PubMed, Cochrane Library, MEDLINE, Embase, and other medical databases. After a literature search, 26 randomized controlled trials involving 1,450 knees were analyzed.

RESULTS

Tourniquet use significantly decreased intraoperative blood loss, transfusion rate, and operation time but not postoperative blood loss, measurable total blood loss, calculated total blood loss, transfusion volume, incidence of pulmonary embolism, or duration of hospital stay. It also slowed down joint functional recovery in the short term and increased the incidence of deep vein thrombosis and other minor wound complications.

CONCLUSIONS

Data from this meta-analysis indicate that patients may benefit from the use of a tourniquet in TKA; however, it use is accompanied by disadvantages and complications. Because of the very low-evidence quality and lower grading of recommendations, assessment, development, and evaluation recommendation strength, no guidelines can be developed based on current evidence.

The limited use of a tourniquet during total knee arthroplasty: a randomized controlled trial

BACKGROUND

Total knee arthroplasty (TKA) is commonly performed using a tourniquet. However, some studies have reported that several complications were associated with the use of a tourniquet in TKA. In this study we investigate whether the limited use of a tourniquet in TKA would reduce complications and facilitate postoperative recovery.

METHODS

Sixty patients were randomly divided into two groups (30 cases/group): group A using the tourniquet throughout the surgical procedure, and group B using the tourniquet starting from the cementation to the completion of the procedure. Operation time, total measured blood loss, and incidence of complications were all recorded.

RESULTS

There was no significant difference in operation time, total measured blood loss, and hemoglobin concentration between the two groups. Incidence of postoperative complications in group B was significantly decreased in comparison to that in group A. The limb circumference at 10 cm above the superior patellar pole or below the inferior patellar pole and the pain score in group B were significantly decreased compared with that in group A at any time point. Range of motion in group B was significantly increased at three and 5 days postoperatively in comparison to that in group A.

CONCLUSIONS

The limited use of a tourniquet in TKA provides the benefit of decreased limb swelling and knee joint pain while not compromising the operation time or blood loss and recovery.

LEVEL OF EVIDENCE

Level I (Therapeutic).

TRIAL REGISTRATION NUMBER

NCT02102581.

The effects of a tourniquet used in total knee arthroplasty: a meta-analysis

Background

The purpose of this research is to evaluate the effects of a tourniquet in total knee arthroplasty (TKA).

Methods

The study was done by randomized controlled trials (RCTs) on the effects of a tourniquet in TKA. All related articles which were published up to June 2013 from Medline, Embase, and Cochrane Central Register of Controlled Trails were identified. The methodological quality of the included studies was assessed by the Physiotherapy Evidence Database (PEDro) scale. The meta-analysis was performed using Cochrane RevMan software version 5.1.

Results

Thirteen RCTs that involved a total of 689 patients with 689 knees were included in the meta-analysis, which were divided into two groups. The tourniquet group included 351 knees and the non-tourniquet group included 338 knees. The meta-analysis showed that using a tourniquet in TKA could reduce intraoperative blood loss (weighted mean difference (WMD), -198.21; 95% confidence interval (CI), -279.82 to -116.60; P < 0.01) but did not decrease the calculated blood loss (P = 0.80), which indicates the actual blood loss. Although TKA with a tourniquet could save the operation time for 4.57 min compared to TKA without a tourniquet (WMD, -4.57; 95% CI, -7.59 to -1.56; P < 0.01), it had no clinical significance. Meanwhile, the use of tourniquet could not reduce the possibility of blood transfusion (P > 0.05). Postoperative knee range of motion (ROM) in tourniquet group was 10.41° less than that in the non-tourniquet group in early stage (≤10 days after surgery) (WMD, -10.41; 95% CI, -16.41 to -4.41; P < 0.01). Moreover, the use of a tourniquet increased the risk of either thrombotic events (risk ratio (RR), 5.00; 95% CI, 1.31 to 19.10; P = 0.02) or non-thrombotic complications (RR, 2.03; 95% CI, 1.12 to 3.67; P = 0.02).

Conclusions

TKA without a tourniquet was superior to TKA with a tourniquet in thromboembolic events and the other related complications. There were no significant differences between the two groups in the actual blood loss. TKA with a tourniquet might hinder patients' early postoperative rehabilitation exercises.

Changes in blood coagulation-fibrinolysis markers by pneumatic tourniquet during total knee joint arthroplasty with venous thromboembolism

This study investigated changes in blood coagulation-fibrinolysis markers during total knee arthroplasty (TKA). Preoperative 16-row multidetector row computed tomography (MDCT) revealed no asymptomatic venous thromboembolism (VTE) in the 42 patients recruited. Using MDCT postoperatively, patients were divided into thrombus (asymptomatic VTE, 19 patients) and no-thrombus (23 patients) groups. Blood taken at intervals before and after pneumatic tourniquet release revealed increased plasminogen activator inhibitor type-1 (PAI-1) at 30s for both groups and at 90s (both P=0.01) in the thrombus group. D-dimer levels were highest at 30 and 90s for both groups (P = 0.01). PAI-1 and D-dimer levels were strongly correlated at both time points in the thrombus group. Inactivating fibrinolysis due to PAI-1 may lead to asymptomatic VTE after TKA.

Tourniquet use during cementation only during total knee arthroplasty: a randomized trial

BACKGROUND

Total knee arthroplasty with the use of a tourniquet during the entire operation has not been shown to improve the performance of the operation and may increase the risk of complications.

QUESTIONS/PURPOSES

We asked whether the limited use of a tourniquet for cementation only would affect (1) surgical time; (2) postoperative pain and motion of the knee; (3) blood loss; or (4) complications such as risk of nerve injuries, quadriceps dysfunction, and drainage compared with use of a tourniquet throughout the procedure.

METHODS

Seventy-one patients (79 knees) were randomized to either use of a tourniquet from the incision through cementation of the implants and deflated for closure (operative tourniquet group) or tourniquet use only during cementation (cementation tourniquet group). The initial study population was a minimum of 30 knees in each group as suggested for randomized studies by American Society for Testing and Materials standards; termination of the study was determined by power analysis performed after 40 knees in each group showed any statistical solution to our questions would require a minimum of 260 more cases. Patients were excluded who were considered in previous randomized studies as high risk for complications, which might be attributed to the tourniquet.

RESULTS

There were no differences in terms of surgical time, pain scores, pain medicine requirements, range of motion, hemoglobin change, or total blood loss. One major complication (compartmental syndrome) occurred in a patient with tourniquet inflation until closure. No other complications were attributed to the use of a tourniquet.

CONCLUSIONS

With the numbers available, our results suggest that there are no important clinical differences between patients who had a tourniquet inflated throughout the procedure compared with those who had it inflated only during cementation. Tourniquet inflation for cementation only provides the benefit of bloodless bone for fixation and may eliminate the risks associated with prolonged tourniquet use.

The study of the thrombin generation mechanism and the effect of low molecular weight heparin as thromboprophylaxis in patients undergoing total knee and hip replacement

INTRODUCTION

The recommended duration of post-operative Low-Molecular-Weight-Heparins (LMWHs) thromboprophylaxis in Total-Hip-Replacement (THR) and Total-Knee-Replacement (TKR) surgery is controversial. Our aim is to study the thrombin generation (TG) modifications induced by surgery and to evaluate the effect of LMWH on TG during and after the recommended duration.

PATIENTS/METHODS

Thirty-one patients received 4000IU anti-Xa/day of enoxaparin, 8-hours post-operatively (15 THR for 30-days and 16 TKR for 15-days). TG assay sensitive to enoxaparin was performed, pre-operatively (D0), 7-hours post-surgery (D1), 8-days post-surgery (D8), and 2-days after thromboprophylaxis withdrawal (D32 and D17), evaluating: lag-time, endogenous thrombin potential (ETP), peak amount of generated thrombin (Peak), time-to-Peak (tt-Peak), and the Mean-Rate-Index [MRI=Peak/(tt-Peak-lag-time)].

RESULTS

TKR surgery decreased lag-time and tt-Peak and increased MRI on D1 vs D0 (p<0.05). In contrast, THR did not significantly modify TG. Enoxaparin effectively reduced thrombin generation in both groups. Thromboprophylaxis withdrawal resulted in rebound increase of TG in the TKR patients (ETP, Peak & MRI significantly increased on D17 vs D0; p<0.05, and vs. D1; p<0.05) but not in THR patients. Variability in the response to enoxaparin was observed among patients of the same group.

CONCLUSIONS

TKR surgery is more thrombogenic than THR surgery. In THR patients TG was efficiently inhibited by 30-day thromboprophylaxis, whereas, in TKR patients treated for 15-days TG was not effectively inhibited. Individual variability of the response to enoxaparin was observed in both groups revealing some form of biological resistance to enoxaparin. TG assay may represent the breakthrough step to efficient antithrombotic strategy in clinical settings with high thrombotic risk.

Hematologic variables and venous thrombosis: red cell distribution width and blood monocyte count are associated with an increased risk

Recent studies suggest that leukocytes and erythrocytes play a role in coagulation. However, whether leukocytes, erythrocytes and other hematologic variables are associated with risk of venous thrombosis is not well known. To study this, we used data from 2473 patients with venous thrombosis and 2935 controls. The variables assessed were: total leukocytes, granulocytes, lymphocytes, monocytes, hematocrit, hemoglobin, erythrocytes and red cell indices (mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration and red cell distribution width). We found a strong dose-response relation for higher red cell distribution width and monocyte count with risk of venous thrombosis, with odds ratios of 3.1 (95% confidence interval, 2.0-4.8) and 2.8 (95% confidence interval, 1.3-5.8), respectively, after adjustment for age, sex, C-reactive protein level, malignancy and co-morbidities. Monocyte count and red cell distribution width were associated with venous thrombosis even within reference ranges. A low monocyte count (<0.12 × 10(9)/L) was associated with a lower risk of venous thrombosis after full adjustment (odds ratios 0.6; 95% confidence interval, 0.4-0.8). In summary, high red cell distribution width and blood monocyte count, two parameters that are inexpensive and easily obtainable, were clearly associated with an increased risk of venous thrombosis. Future studies should evaluate the underlying mechanism and the use of these variables in prediction models for first and recurrent thrombosis.

Platelet recruitment to venous stent thrombi

Thrombosis following venous stent placement is a morbid clinical outcome. Whether to target platelets or coagulation factors for venous stent thromboprophylaxis remains unclear. We sought to determine whether integrin α(IIb)β3 antagonism with lamifiban would inhibit platelet recruitment to venous stent thrombosis. Anti-thrombotic efficacy was compared between venous and arterial circulations. Pigs received either lamifiban (0.2 mg/kg bolus plus 0.2 mg/kg/h infusion; n = 6) or saline (n = 12). Carotid arteries were crush injured and then harvested 30 min later to provide an assessment of antithrombotic efficacy in the arterial circulation. Iliac venous stents were then deployed and thrombi allowed to propagate for 2 h before harvesting. Platelet deposition was measured by scintillation detection of autologous (111)In-platelets. Venous thrombi were quantified by weight and compared to platelet, Von Willebrand factor (VWF) and fibrinogen content. Arterial platelet deposition (×10(6)/cm(2)) was reduced >80% by lamifiban (398 ± 437) compared to controls (1,540 ± 883; p < 0.005). Lamifiban also reduced venous thrombus platelet deposition (139 ± 88 vs. 281 ± 167) however did not prevent thrombosis. In control animals, venous stent platelet deposition correlated with plasma fibrinogen content (R(2) = 0.29; p = 0.03). Fibrinogen content correlated directly with venous stent platelet deposition (p = 0.03) but not thrombus weight. Neither venous platelet deposition nor thrombus weights varied by VWF content. Platelet recruitment to venous stent thrombi occurs in part through the integrin α(IIb)β3 receptor. Unlike arterial thrombosis, inhibition of this receptor is insufficient to prevent venous stent thrombosis.

Emphasis on the Role of PF4 in the Incidence, Pathophysiology and Treatment of Heparin Induced Thrombocytopenia

Heparin Induced Thrombocytopenia (HIT) is caused by antibodies that recognize platelet factor 4 (PF4) associated with polyanionic glycosaminoglycan drugs or displayed on vascular cell membranes. These antibodies are elicited by multimolecular complexes that can occur when heparin is administered in clinical settings associated with abundant PF4. Heparin binding alters native PF4 and elicits immune recognition and response. While the presence of heparin is integral to immunogenesis, the HIT antibody binding site is within PF4. Thus HIT antibodies develop and function to cause thrombocytopenia and/or thrombosis only in the presence of PF4. Future emphasis on understanding the biology, turnover and regulation of PF4 may lead to insights into the prevention and treatment of HIT.

A platelet target for venous thrombosis? P2Y1 deletion or antagonism protects mice from vena cava thrombosis

A role for platelets in the pathogenesis of venous thrombosis was suggested by clinical and preclinical studies. However, examination of the platelet receptor, P2Y1, in this area has been limited. The goal of the current study was to examine effects of P2Y1 deletion, or selective antagonism with MRS2500, in oxidative venous thrombosis in mice. The P2Y12 antagonist, clopidogrel, was included as a reference agent. Anesthetized C57BL/6 or genetically modified mice underwent 3.5 or 5 % FeCl(3)-induced vena cava thrombosis. Pharmacokinetic properties of MRS2500 were defined for dose selection. Platelet aggregation and renal or tail bleeding times (BT) were measured to put antithrombotic effects into perspective. P2Y1 deletion significantly reduced (p < 0.001) venous thrombus weight by 74 % in 3.5 % FeCl(3) injury compared to P2Y1(+/+) littermates. MRS2500 (2 mg/kg, i.v.) significantly decreased (p < 0.001) thrombus weight 64 % in C57BL/6 mice. In the more severe 5 % FeCl(3)-induced injury model, thrombus weight significantly (p < 0.001) decreased 68 % in P2Y1(-/-) mice versus P2Y1(+/+) mice, and MRS2500 (2 mg/kg) was also beneficial (54 % decrease, p < 0.01). Renal BT doubled in P2Y1(-/-) versus P2Y1(+/+) mice, and increased threefold with MRS2500 compared to vehicle. Tail BT was markedly prolonged in P2Y1(-/-) mice (7.9X) and in C57BL/6 mice given MRS2500. The current study demonstrates that P2Y1 deletion or antagonism significantly reduced venous thrombosis in mice, suggesting that P2Y1 receptors play a role in the pathogenesis of venous thrombosis, at least in this species. However as with many antithrombotic agents the benefit comes at the potential price of an increase in provoked bleeding times.

A comparison of outcomes with and without a tourniquet in total knee arthroplasty: a systematic review and meta-analysis of randomized controlled trials

A tourniquet is often used in total knee arthroplasty resulting in improved visualization of structures, reduced intraoperative bleeding and better cementation. The risks include deep vein thrombosis and pulmonary embolism. To quantify the case for or against tourniquet use, we carried out a systematic review and meta-analysis of selected randomized controlled trials. Ten studies were included in the meta-analysis. Of the 8 outcomes analyzed (surgery duration; total, intraoperative, and postoperative blood losses; deep vein thrombosis; pulmonary embolism; and minor/major complications), the total and intraoperative blood losses were less using a tourniquet. Minor complications were more common in the tourniquet group. The remaining outcomes showed no difference between the groups. Using a tourniquet may be beneficial, but long-term studies of outcome are needed.

Markers of thrombin generation during resurfacing and noncemented total hip arthroplasty: a pilot study

BACKGROUND

Hip resurfacing arthroplasty (HRA) could be associated with an increased risk of deep vein thrombosis (DVT) compared to traditional noncemented THA because it involves greater dissection, increased kinking and distortion of the femoral vessels, takes longer to perform, and involves insertion of some cement into the femur.

QUESTIONS/PURPOSES

Does HRA lead to greater risk of thromboembolism compared with noncemented THA?

METHODS

We prospectively studied 20 patients receiving HRA and 20 receiving THA. All patients were younger than 67 years old and were similar in height, weight, American Society of Anesthesiologists status, and gender mix. Patients undergoing HRA were younger (mean, 50 versus 59 years), their surgery was longer (mean, 87 versus 65 minutes), and they required more crystalloid during surgery (mean, 2160 versus 1662 mL). Radial artery blood samples were taken at six events during surgery and assayed for prothrombin fragment F1 + 2 and thrombin-antithrombin III complex (TAT) using enzyme-linked immunosorbent assays.

RESULTS

We observed no differences in the intraoperative increases in F1 + 2 and TAT between the two groups and no differences in surgical events.

CONCLUSION

Based on these data, HRA and THA should have similar risk of thromboembolism as THA based on the parameters we measured.

LEVEL OF EVIDENCE

Level I, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.