Comparison Between the Efficacy of Rivaroxaban vs Enoxaparin in Post-Operative Deep Venous Thrombosis Prophylaxis After Exploratory Laparotomy
Phase: PHASE4
Conditions: Deep Venous Thromboses, Laparotomy Patients
Sponsor: Mayo Hospital Lahore

Dated: 13/3/2023 
SYNOPSIS FOR FCPS-II 
(GENERAL SURGERY) 
 
 
“COMPARISON BETWEEN THE EFFICACY OF RIVAROXABAN VS 
ENOXAPARIN IN POST-OPERATIVE DEEP VENOUS THROMBOSIS 
PROPHYLAXIS AFTER EXPLORATORY LAPAROTOMY” 
 
 
SUBMITTED BY: 
DR. MUHAMMAD MASHHOOD AHMAD SHAD 
POSTGRADUATE RESIDENT FCPS GENERAL SURGERY 
WEST SURGICAL WARD 
KEMU/MAYO HOSPITAL LAHORE 
SUPERVISOR: 
PROF. DR. AHMAD UZAIR QURESHI 
PROFESSOR OF GENERAL SURGERY 
WEST SURGICAL WARD 
MAYO HOSPITAL LAHORE 

 
 
 
 
COMPARISON BETWEEN EFFICACY OF RIVROXABAN VS ENOXAPARIN IN 
POST-OPERATIVE DVT PROPHYLAXIS AFTER EXPLORATORY LAPAROTOMY 
 
Unique identifier. _________________   
Reg. No. _________________________ Group:   R / E   Dosage:_________________________ 
Patient Name:____________________________________________ Age: _________________ 
Gender: M/F  Date of Admission: ____________________ Date of Discharge_______________ 
Diagnosis:_____________________________________________________________________ 
Operation______________________________________________________________________
Previous DVT  Yes / No 
POST OPERATIVE VARIABLES 
VARIABLE 
VALUES AT DAY 5 
VALUES AT DAY 10 
DEEP VENOUS 
THROMBOSIS ON 
CDUS 
(YES/NO) 
 
 
WELL’S SCORE 
(-2 TO 9) 
 
 
 

 
 
 
 
 
 
 
 
CONSENT FORM 
 
Title of Research: Comparison Between the Efficacy of Rivaroxaban and Enoxaparin in 
Post-Operative Deep Venous Thrombosis (DVT) Prophylaxis After Exploratory Laparotomy 
You are invited to participate in a research study aimed at comparing the effectiveness of two medications, 
rivaroxaban and enoxaparin, in preventing blood clots (DVT) following surgery. This study involves 
patients who have undergone exploratory laparotomy. If you choose to participate, you will be randomly 
assigned to receive either rivaroxaban or enoxaparin post-surgery. Your health will be monitored closely 
through regular follow-ups, including Doppler ultrasound studies on the 5th and 10th days after surgery to 
check for any blood clots. 
Both medications are approved for the prevention of blood clots, but may have side effects such as bleeding. 
We will take all necessary precautions to minimize these risks. Participation in this study may help enhance 
our understanding of DVT prevention and benefit future patients undergoing similar surgeries. Your 
personal information will be kept strictly confidential and used only for research purposes. Data will be 
anonymized to protect your privacy. 
Participation in this study is entirely voluntary. You are free to withdraw at any time without any negative 
consequences. If you have any questions about the study, please contact Dr. Muhammad Mashhood Ahmad 
Shad at 03390420285. By signing below, you agree to take part in this study. 
Patient Name and Signatures 
 
Patient’s CNIC No. 
               
Date and Time 
               
Witness   1
  
 
CNIC No. 
Witness 2
                 
CNIC No. 

INTRODUCTION 
Deep vein thrombosis (DVT) is the formation of blood clots in deep veins more likely 
to occur in lower limbs than in upper limbs. It is one of the major but preventable causes of 
morbidity and mortality and leads to 60,000 to 100.000 deaths every year in the United States.1 
Although DVT is a major complication in many orthopedic surgeries,2 it also occurs in up to 
4.9 % of abdominal surgeries lasting more than 2 hours.3 
 Medications as well as mechanical techniques are used as primary prophylaxis of 
DVT1. Rivaroxaban is one of the oral medications used for DVT prophylaxis after surgeries. 
4Rivaroxaban is a factor Xa inhibitor commonly used in once daily dosage.5 In a trial on 
Orthopedic setting, Rivaroxaban is considered superior to enoxaparin in preventing DVT.6 
Rivaroxaban has improved efficacy as compared to LMWH but has an increased risk of 
bleeding in Orthopedic patients. Moreover, Rivaroxaban is more cost-effective as compared to 
Enoxaparin.7 In another study, incidence of DVT in enoxaparin group was 26.61% vs 9.5% in 
Rivaroxaban group. 8Exploratory laparotomy is a cost-effective procedure as compared to other 
emergency interventions and is common in low- and mid-income countries.9 In emergency 
general surgery incidence of DVT is highest in GI surgeries (1.705%) and DVT is a significant 
burden on resources in emergency general surgery.10 The ASH 2019 guidelines for DVT 
prophylaxis after surgery recommend mechanical prophylaxis over no prophylaxis, pneumatic 
compression over graduated compression stockings, and pharmacological prophylaxis with 
low-molecular-weight heparin or unfractionated heparin for major general surgery11. Current 
practice at Mayo hospital Lahore is according to ASH 2019 guidelines for DVT prophylaxis. 
This research is crucial to compare the relative efficacy of Rivaroxaban versus enoxaparin in 
postoperative DVT prophylaxis in general surgical settings. As there is no study conducted on 

Pakistani population regarding efficacy of these drugs, locally relevant data can optimize 
patient care in Pakistan, guiding more efficient and effective treatment strategies.  
RESEARCH QUESTION: To assess the comparative efficacy of Rivaroxaban vs Enoxaparin 
in preventing deep vein thrombosis (DVT) in patients undergoing emergency exploratory 
laparotomy in general surgical settings in local population of Pakistan. 
OBJECTIVE: To compare the outcome of Rivaroxaban vs Enoxaparin as post-operative DVT 
prophylaxis in patients undergoing emergency exploratory laparotomy in terms of DVT 
findings detected by color Doppler ultrasound after  
HYPOTHESIS: There is a difference in the efficacy of Rivaroxaban vs Enoxaparin as post-
operative DVT prophylaxis in patients undergoing emergency exploratory laparotomy. 
OPERATIONAL DEFINITIONS: 
Exploratory Laparotomy: A surgical intervention performed to examine the abdominal 
cavity, often indicated for patients presenting with acute abdominal conditions that cannot be 
diagnosed through less invasive methods. This procedure is crucial for diagnosing and 
sometimes treating injuries or diseases within the abdominal space.12 
Deep Venous Thrombosis (DVT): The formation of blood clots in deep veins, mostly in legs 
as detected by color Doppler ultrasound as obliterated and non-compressible vein at 5th and 
10th post operative days.13 
Post-Operative Period: The duration immediately following surgery during which the patient 
is monitored for recovery and potential complications. This period typically encompasses the 
first 30 days post-surgery, aligning with the common timeframe used in clinical research to 
assess short-term postoperative outcomes 
 

MATERIALS AND METHODS: 
Study Settings: Male and Female West Surgical Wards, Mayo Hospital, Lahore 
Study Design: Randomized Control Trial 
Duration of Study: Six (06) months after approval of synopsis 
Sampling Technique The study will utilize the Clinical Trial Randomization Tool provided 
by the National Cancer Institute for random allocation of participants. The asymptotic maximal 
method will be used with a maximal tolerance imbalance of 3. 
Sample Size: A sample size of 106 in each group is estimated with 5% level of significance 
amd 90% power of the test with anticipated p1 = 9.5% and p2 = 26.61%. 
INCLUSION CRITERIA: 
• Patients aged 18 to 80 years 
• Both male or female patients 
• Patients who have undergone emergent exploratory laparotomy for any reason whether 
traumatic or non-traumatic 
• Patients with expected immobility for more than 24 hours 
EXCLUSION CRITERIA: 
• Patients with diagnosed pre-operative DVT 
• BMI more than 40 
• Patient who are on mechanical ventilation post operatively 
• Patient with postoperative Myocardial infarction, ischemic heart disease or 
cerebrovascular accident 
• Patients who have undergone limb surgery in addition to exploratory laparotomy 

• Patients who are allergic or intolerant to either Rivaroxaban or Enoxaparin 
• Patients with a known history of bleeding disorder or bleeding complications 
• Patients who are currently taking anticoagulant medications or have taken them in the 
last 48 hours 
• Patients 
with 
a 
history 
of 
thrombocytopenia 
or 
HIT 
(Heparin-induced 
thrombocytopenia) 
• Any patient developing postoperative bleeding 
DATA COLLECTION: 
After formal approval of the synopsis, patients eligible for the study will be identified 
upon admission to the surgical ER using convenience sampling. Once consented and enrolled, 
each patient will be assigned a unique identifier. The Clinical Trial Randomization Tool will 
use these identifiers to randomly allocate patients to either the Rivaroxaban or Enoxaparin 
group while maintaining a balance between the groups within the maximally tolerated 
imbalance value of 3. Rivaroxaban (Tab. Xcept) will be given 10mg orally once daily and 
Enoxaparin (Inj. Clexane) will be given 4000IU (40mg or 0.4ml) subcutaneously once daily 
for 7 days.  
All the patients will be scheduled for complete duplex ultrasonography by the 
radiologist who is blind to the treatment group within 48 hours after surgery to rule out any 
previous DVT. Patients having already established DVT will be excluded.The complete duplex 
ultrasonography of bilateral lower limb veins from common femoral, popliteal to tibial veins 
will be performed by the radiologist after 5th and 10th postoperative day to detect evidence of 
deep venous thrombosis on CDUS to assess presence or absent of deep venous thrombosis and 
simultaneously assessed using Well’s score to assess the risk of DVT. In case any patient 
develops DVT postoperatively in either group will be marked as treatment failure and will be 

subjected to anticoagulation with LMWH at therapeutic dosage as per international guidelines 
and later shifted to oral warfarin 5-10mg once a day with INR monitoring.  
DATA ANALYSIS: 
The IBM SPSS statistics V25.0 for Windows program will be used to conduct the statistical 
analysis of the data (IBM, Armonk, New York, USA). The % for descriptive data will be 
displayed for variables including gender, BMI classes, surgical indication, blood transfusion, 
and DVT diagnosis. Age is one of the variables for which the mean and standard deviation will 
be determined. The chi-square test will be used to compare the outcome data of the two groups 
to identify any statistically significant differences; a p-value of 0.05 or less will be regarded as 
statistically significant. Age, gender, surgical indication, blood transfusion, and BMI classes 
will be used to stratify outcome data, and a post-stratification chi-square test will be used. 
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