Venous thromboembolism (VTE) is a common complication among patients who undergo surgery: 20% to 30% after general surgical operations, 50% to 75% after orthopedic procedures,1 and 0.2% to 9.5% after laparoscopic surgery.1–6 Patients with VTE are at increased risk of dying, especially within the first year after diagnosis, but also during the entire 30 years of follow-up with VTE as an important cause of death.7 Although 30-day mortality after deep vein thrombosis (DVT) remained fairly constant over the last 3 decades, it has improved markedly for pulmonary embolism.7 Pulmonary thromboembolism is a feared complication of DVT. The mortality rate in untreated cases is 25% to 30%, whereas the mortality rate in treated cases decreased to 5% to 8%.8 In the existing literature, the magnitude of long-term mortality after VTE varies substantially.7 A recent study reported an 8-year mortality risk of 12%, whereas, in an earlier study, mortality risk reached 50% after 8 years of follow-up.7 Previous studies were limited by short follow-up time (maximum 10 y).7 Currently, laparoscopic operations account for about 50% to 60% of all surgical interventions; moreover, their range has already expanded rapidly and continues to grow. As the number of patients undergoing laparoscopic fundoplication remain fairly constant, there is an increased likelihood of the incidence of both DVT and pulmonary embolism. To prevent these complications, an optimal preventative strategy is necessary.
The aim of this study was to assess and recommend the optimal DVT prophylaxis regimen for patients undergoing laparoscopic fundoplication according to the blood coagulation changes and the rate of DVT in 2 patients groups receiving different prophylaxis regimens.
Our hypothesis before the study was that low–molecular-weight heparin (LMWH) administered 1 hour before the laparoscopic fundoplication will cause higher intraoperative hypocoagulation and therefore lower rates of postoperative DVT than when administered 12 hours before surgery.
MATERIALS AND METHODS
A prospective, randomized clinical trial was performed at the Hospital of Lithuanian University of Health Sciences Kaunas Clinics. The study protocol was evaluated and approved by the Kaunas Regional Committee on Biomedical Research Ethics (October 8, 2014, No. BE-2-13). This clinical trial was also registered at the BioMed Center of the International Center for Clinical Trials ISRCTN on December 29, 2014 (ID ISRCTN62203940).
The study population consisted of patients scheduled to undergo laparoscopic fundoplication because of gastroesophageal reflux disease (GERD) at the Surgery Department of HLUHS KK during the period 2013 to 2016. A total of 121 patients were examined; among them 41 were male individuals and 80 female individuals.
Patients were randomly allocated (according to the distribution of random numbers by line) into 2 groups. Each group received a different DVT prophylaxis regime. The study scheme is shown in Figure 1.
The first group of 59 patients received LMWH Bemiparin (Zibor; Berlin Chemie, Luxembourg) 2500 TV 0.2 mL subcutaneously 12 hours before the operation. The second group of 62 patients received LMWH Bemiparin 2500 TV 0.2 mL subcutaneously 1 hour before the operation. Both groups received intermittent pneumatic compression (IPC) during the entire laparoscopic fundoplication. The IPC was performed using “Kendall SCD 700 Series” apparatus.
All the operations were performed using standardized endotracheal anesthesia.
Premedication: all patients received 7.5 mg of midazolam 1 hour before their transfer to the operating room. In the operating room, standard monitoring, including electrocardiogram (5-electrode system), peripheral oxygen saturation, and noninvasive blood pressure (“S/5 Compact” Datex-Ohmeda), was established. Preoxygenation with 100% oxygen via a face mask for 3 minutes was followed by the standardized induction of anesthesia with thiopentone 4 to 6 mg/kg, fentanyl 2.5 μg/kg, and pipecuronium 0.08 mg/kg. Anesthesia was subsequently maintained with isoflurane 0.6 to 0.7 of the minimal alveolar concentration and fentanyl 1.0 to 1.25 μg/kg every 20 to 25 minutes. The lungs were artificially ventilated with “S/5 Aespire” Datex-Ohmeda (FiO2 0.40 to 0.45). Respiration was monitored with “S/5 Compact” Datex-Ohmeda, parameters of artificial lung ventilation were changed according to capnography readings, maintaining end-tidal partial pressure of CO2 at 35 to 40 mm Hg. Neuromuscular blockade was reversed by atropine 1.0 mg and neostigmine 2.0 mg. All patients were extubated in the operating room.
Infusion therapy: before insufflation, all the patients received 500 mL of Ringer solution intravenously; the total amount of fluid administered during surgery was 1.500 mL of Ringer solution.
Two experienced surgeons performed all the operations. Toupet fundoplication was performed for all patients. All the operations were performed according the standard methodology. Pneumoperitoneum was induced by inserting Veress needle above the umbilicus and connecting it to the CO2 insufflator, which achieved and maintained an intra-abdominal pressure of 12 to 14 mm Hg. The patients were placed in reverse Trendelenburg position (45 degrees) before intra-abdominal manipulation.
Blood Collection and Processing
During the course of the study, venous blood was taken for future analysis [thrombin-antithrombin complex (TAT), plasma prothrombin fragment F1+2 (F1+2), free tissue factor pathway inhibitor (fTFPI), and MP-TF activity in plasma]:
- Before the injection of LMWH (Bemiparin).
- One hour before the start of surgery.
- After extubation on the postoperative ward.
Hypercoagulation state was assessed by measuring the F1+2, the TAT, and tissue factor microparticles (MP-TF). The hypocoagulation effect was evaluated by measuring fTFPI. Blood was drawn by a clean venipuncture following a double syringe technique and placed into Vacutainer 4.5 mL tubes containing 3.9% (0.129 M) trisodium citrate (Becton Dickinson Vacutainer Systems, Plymouth, UK) in the ratio of 1 part citrate and 9 parts whole blood using minimal tourniquet time. The blood was taken from the basilic vein into vacuum tubes (Becton Dickinson Vacutainer Systems) without sodium citrate for an assessment of an activity of MP-TF in the plasma.
All patients underwent color duplex scan examination preoperatively and spiral CT venography on the third postoperative day to detect possible DVT. One experienced radiologist performed all these examinations. Criteria for DVT diagnosis were as follows: intraluminal filling defect or noncompressible venous segment.
Data analysis was performed using the program package SPSS/version 12.0 (SPSS Inc.) and standard Windows Excel programs. Demographic data and averages for comparison were compared using 2-tailed t tests. For variables not normally distributed, Freidman tests were used to analyze the significance of temporal effects within each surgical group. Wilcoxon signed rank tests were used to evaluate significant differences from baseline values within each group, and Mann-Whitney U tests were used to assess the significance between groups at each timepoint. Nonparametric values were compared using the χ2 criterion. A P-value <0.05 was considered significant. Continuous variables are presented as mean±SD. When the interrelation between the quantitative variables, MP-TF and fTFPI, was assessed, the Pearson correlation coefficient and Spearman rank correlation coefficient were calculated.
The patients in both groups were similar in terms of age, weight, height, sex, duration of surgery, postoperative stay, and American Society of Anesthesiologists class (Table 1). There was no major or minor bleeding during or after any laparoscopic operation. No drains were left after the operation. There were no intraoperative and postoperative complications in either group.
TAT value changes in both groups are presented in Figure 2. TAT was similar in both groups before the surgery, with no significant difference. In group I, TAT significantly increased (3.6%) 1 hour after the introduction of the laparoscope, but reached preoperative levels just after the operation; in group II, TAT slightly (1.1%) increased just 1 hour after surgery and significantly decreased to preoperative levels after extubation.
F1+2 value changes in both groups are presented in Figure 3. F1+2 was similar in both groups before surgery, with no significant difference. In group I, F1+2 significantly increased 1 hour after the introduction of the laparoscope, and significantly decreased after the operation; in group II, F1+2 significantly increased 1 hour after the introduction of the laparoscope, but significantly decreased after the operation.
MP-TF value changes in both groups are presented in Figure 4. MP-TF was similar in both groups before surgery, with no significant difference. In group I, MP-TF significantly increased 1 hour after the introduction of the laparoscope and slightly decreased after the operation but still remained above the preoperative level; in group II, MP-TF significantly increased 1 hour after the start of the operation as well, but reached preoperative levels after extubation.
fTFPI value changes in both groups are presented in Figure 5. In group I, fTFPI significantly decreased 1 hour after the introduction of the laparoscope and regained the preoperative level at the end of the surgical intervention. In group II, fTFPI significantly increased 1 hour after the introduction of the laparoscope and after the operation.
TAT and F1+2 values were not significantly different between the groups before LMWH injection, and during and after laparoscopic fundoplication (Table 2). MP-TF values were significantly different between the groups after laparoscopic fundoplication (Table 2). fTFPI values were significantly different between the groups before LMWH injection, and during and after laparoscopic fundoplication (Table 2).
Postoperative DVT Diagnosis
There was no proximal DVT in our study patients. CT venography revealed calf vein thrombosis in 2 group I patients on the third postoperative day (Figs. 6, 7). Total postsurgical DVT frequency was 1.65%: 3.6% in group I and 0% in group II.
Virchow coagulation defects are now generally referred to as hypercoagulability and are known to result from a trauma or from surgical procedures. Laparoscopic surgery may potentially predispose to thrombosis, as it alters the venous flow and coagulability and causes endothelial injuries.9,10 Earlier studies have shown that endotracheal anesthesia significantly reduces venous drainage from the legs, disturbing the activity of the calf muscle pump (relaxation). This results in venous stasis, which is one of the major risk factors, for intraoperative DVT.
A series of highly sensitive and specific immunochemical tools have been developed that can quantitate the levels and activities of various steps of the hemostatic mechanism in vivo. These include F1+2, which measures the cleavage of prothrombin molecule by factor Xa and TAT complexes, reflecting the vivo thrombin generation process. The increases in plasma F1+2 and TAT complex indicate an increased formation of thrombin. In this study, plasma F1+2 and TAT complex were used as markers of activation of the coagulation pathway.
The study by Ota et al11 has shown that plasma levels of F1+2, D-dimer, and TAT were significantly higher in patients with thrombosis. The sensitivity and specificity of F1+2 were 86.2% and 80.6%, respectively. Plasma levels of F1+2 were closely correlated with D-dimer, and TAT, and the correlation between F1+2 and TAT was the closest. The findings suggest that high concentrations of hemostatic molecular markers, especially F1+2, which is known as a marker of a hypercoagulable state, reflect a high risk for thrombosis. Specificity for thrombosis was better for F1+2 than for TAT, thus suggesting that F1+2 may be the most useful marker for the earlier phase of thrombosis.
Our study results demonstrated that LMWH similarly protected from possible operation-induced hypercoagulation when administered 1 and 12 hours before laparoscopic fundoplication. F1+2 plasma levels were significantly increased 1 hour after the introduction of laparoscope when compared with baseline levels. These results suggest that operatively induced hypercoagulability was controlled by the end of the surgical intervention.
In group I, TAT plasma levels increased significantly during the first hour of laparascopic surgery. In contrast, TAT levels only marginally increased in group II. It can be speculated that LMWH administered 1 hour before surgery provides better control of plasma TAT levels during the first hour of operation compared with LMWH administered 12 hours before surgery. In both groups, TAT levels significantly decreased after the operation when compared with 1 hour after the introduction of the laparoscope; hence, surgical intervention–induced hypercoagulabilty was controlled equally well by both prophylactic regimens in the immediate postoperative period. In their pilot study, Zezos et al12 found significant activation of coagulation and fibrinolysis indices in the immediate postoperative period in all patients, supporting the increased thromboembolism risk following laparoscopic surgery. However, no significant differences between the 2 laparoscopic techniques were observed, which in turn suggests a similar pattern and an equivalent degree of hemostasis activation in both conventional multiport and single-incision laparoscopic cholecystectomy. They found that, in both procedures, the activation of coagulation and fibrinolysis cascades shows a similar pattern. F1+2 and TAT plasma levels show an increase in the immediate postoperative period (1 h postoperatively), with a drop after 24 hours, and it means that they found a similar pattern as ours in the variation of F1+2 and TAT plasma values preoperatively and postoperatively. Schietroma et al13 investigated changes in the blood coagulation and fibrinolysis during laparoscopic and open cholecystectomy and found a similar pattern as ours in the variation of F1+2 and TAT plasma values preoperatively and postoperatively, but with more marked changes in the open group.
Over the past 10 years, MPs have emerged as a potential key player in thromboembolic events.10 The repertoire of MP-exposed membrane proteins reflects that of the cell of which they were shed, and one of these proteins is TF. TF is the primary initiator of the coagulation cascade. In particular, the association between tissue factor–positive microparticles (TF-MPs) and VTE has been studied.14 MPs generated from platelets form the majority (∼80%) of all MPs found in the plasma 14 but the procoagulant activity of these MPs is limited. More likely, platelet MPs acquire TF through fusion with TF-MPs from other cellular sources, such as monocytes. Indeed, monocyte and endothelium-derived MPs expose TF in vitro and show significant clotting activity.15,16 Several, but not all studies, have found that either plasma TF-MP concentration or TF-MP procoagulant activity positively correlates with the risk of VTE.16–20 TF-MP activity and concentrations in plasma unambiguously correlate with the risk of recurrent VTE.20,21 The increased circulating MPs are associated with thrombosis; however, their role in thrombogenesis is poorly understood.15 A recent study showed an increase in TF expression in peripheral blood mononuclear cells of patients receiving total knee arthroplasty. Interestingly, the increase in TF preceded the median time of diagnosis of VTE, suggesting that TF was involved in the formation of the thrombus.22,23 Nieuwland et al24 demonstrated a procoagulant state in patients undergoing cardiopulmonary bypass. Pericardial blood from these patients had significantly increased MP-TF activity. These data suggest that endothelial damage and/or inflammation in surgical and trauma patients increase cellular TF expression, and the release of TF-MPs into the circulation, which promotes the development of VTE. Thaler et al,25 in a study with 41 patients, state that MP-TF activity is low at the acute event in patients with unprovoked DVT of the lower limb, and MP-TF activity also did not differ significantly between patients with proximal or distal DVT and between those with or without residual DVT after 6 months.
In our study, MP-TF plasma values were significantly increased 1 hour after the introduction of the laparoscope when compared with baseline levels in both groups, and MP-TF plasma levels significantly decreased after the operation only in group II; this indicator remains significantly higher after extubation in group I, suggesting that MP-TF-induced hypercoagulability still can be present at this timepoint in the early LMWH prophylaxis group. Our study results demonstrated that LMWH is useful in protecting patients undergoing laparoscopic fundoplication from possible operation-induced MP-TF-mediated hypercoagulation, especially when it is administered 1 hour before the surgical intervention, as indicated by the significant difference between MP-TF values in our 2 study groups.
We think that an increased MP-TF activity in patient’s plasma during or shortly after surgical intervention may be a potential predictor for DVT development. Further prospective studies are needed to validate its sensitivity and specificity in this setting.
Coagulation is regulated at several levels. Key inhibitors include tissue factor pathway inhibitor (TFPI), antithrombin, and the protein C pathway. The inhibition of the factor VIIa/tissue factor complex (extrinsic coagulation pathway) is effected by TFPI.9,26 TFPI acts in a 2-step manner.26 In the first step, TFPI complexes and inactivates factor Xa to form a TFPI/factor Xa complex. The TFPI within this complex then inactivates tissue factor–bound VIIa as the second step. As the formation of the TFPI/factor Xa complex is a prerequisite for the efficient inactivation of factor VIIa, the system ensures that some factor Xa generation occurs before factor VIIa–mediated initiation of the coagulation system. The TFPI-free antigen assay is specific for free circulating TFPI, and it does not detect lipid-bound TFPI. The TFPI total antigen assay is specific for the total amount of TFPI, including that which is lipid-bound.27 In our study, fTFPI was used as a marker of the hypocoagulation effect.
In our study, fTFPI significantly decreased 1 hour after the introduction of the laparoscope in the early LMWH prophylaxis group and regained the preoperative levels at the end of the surgical intervention. This finding points to the suboptimal hypocoagulation effect of LMWH through fTFPI-induced TF inactivation when LMWH was administered 12 hours before the operation. In group II, when LMWH was administered 1 hour before surgery, fTFPI significantly increased 1 hour after the introduction of the laparoscope and further increased during the operation. These results argue for excellent suppression of TF activity, which is mediated by LMWH-released fTFPI, when the medication is administered shortly before the operation. This is also in line with a significant decrease of MP-TF activity at the end of laparoscopic fundoplication in group II. The antithrombotic effect of IPC is thought to be the result of increased venous velocity and stimulation of endogenous fibrinolysis. However, the results of several studies on the enhancement of hypocoagulation effect by an IPC have been controversial. Cahan et al28 showed that external pneumatic compression devices did not enhance systemic fibrinolysis or prevent postoperative shutdown either by decreasing plasminogen activator inhibitor-1 activity or by increasing tissue plasminogen activator activity. Their data suggest that external pneumatic compression devices do not prevent deep venous thrombosis by fibrinolytic enhancement; effective prophylaxis is achieved only when the devices are used in a manner that reduces venous stasis in the lower extremity. In the study by Giddings et al,29 IPC led to highly significant falls in factor VIIa, associated with increased levels of TFPI. IPC enhances fibrinolysis and suppresses procoagulant activation. Measurements of specific fibrinolytic components do not reflect overall fibrinolytic activity and are highly dependent on the method of assay. A large review involving 19 trials using IPC alone as prophylaxis was published on a variety of surgical patients. This analysis involved 2255 patients and showed that IPC significantly reduced the DVT rate from 23.4% to 4.7%.30
Our study identified 2 cases of DVT in the calf (3.6%) only in the group where LMWH was administered 12 hours before laparoscopic surgery. Collaterals were the criteria of chronic DVT. This postoperative DVT frequency is based not only on the clinical symptoms of DVT in the legs, but also on the use of advanced and new diagnostic techniques for DVT. This confirms that specificity and sensitivity of the US scanning in the evaluation of the lower leg veins is lower than when compared with the possibilities of this study to evaluate proximal veins.
Keeping in mind that patients are mobile within a few hours after laparoscopic fundoplication, we can speculate that DVT of the calf in these 2 patients occurred during the operation. Therefore, the need for pharmacological, mechanical preventive measures or a combination of them before and during these operations is obvious. The study by Garg et al31 shows a statistically significant perioperative increase in D-dimer levels, which suggests a formation of intravascular clot. The increase in D-dimer indicates that both coagulation and fibrinolysis are activated, as it is the end product of the degradation of fibrin, which must have been formed by coagulation in the first phase.
Furthermore, there is a possibility that small thrombi formed initially in the postoperative period might have been thrombolysed by increased fibrinolytic activity and therefore could not be visualized by color Doppler performed on the seventh postoperative day. It should also be kept in mind that most studies including ours have used color duplex imaging of bilateral lower limbs as a method to detect DVT, which has only 63.5% sensitivity in detecting distal DVT.32
According our study results, we can assume with caution that prophylaxis with intraoperative IPC and LMWH 12 hours before laparoscopic surgery is not efficient enough to protect against hypercoagulation state, present during laparoscopic fundoplication. LMWH accelerates the inactivation of antithrombin-mediated coagulation factor Xa and IIa and increases the concentration of fTFPI in the plasma. As both prophylactic methods (LMWH and IPC) potentiate each other and inhibit different thrombosis developmental sequences, this significantly decreases the probability of developing thrombotic complications while minimizing the risk of bleeding at the same time.
- Hypercoagulation state, determined by increased F1+2, TAT, and MP-TF indexes, is more obvious during and after laparoscopic fundoplication, when LMWH is administered 12 hours before the operation with intraoperative IPC.
- During and after laparoscopic fundoplication, LMWH controls hypercoagulation more effectively when it is administered 1 hour before surgery with intraoperative IPC: it causes significant reductions of F1+2, TAT, and MP-TF indexes and significant increase of fTFPI levels.
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