RISK FACTORS FOR VENOUS THROMBOEMBOLISM IN SURGICAL PATIENTS AT OBAFEMI AWOLOWO UNIVERSITY TEACHING HOSPITALS COMPLEX, ILE-IFE

Abstract

Introduction
Venous thromboembolism is an important complication of surgery that results in
high morbidity and mortality. Screening of at risk patients and institution of
adequate thromboprophylaxis has been shown to reduce the case fatality rate.
Materials and Methods
The retrospective arm of the study was aimed at determining the risk distribution
among surgical patients from the departments of General Surgery,
Orthopaedics, Obstetrics and Gynaecology over a twelve month period in
Obafemi Awolowo University Teaching Hospital Complex, Ile-ife, and to
evaluate the pattern of usage of prophylactic anticoagulant in these patients.
The prospective arm of the study was aimed at assessing the total risk score of
VTE among surgical patients before a major operation using three tools (Venous
thromboembolism Risk Factor Assessment by Caprini et al, Revised Geneval
Score for pulmonary embolism and Pretest probability of Deep Venous
Thrombosis by Wells). It also aimed to determine the relationship between the
risk score and full blood count (FBC),activated partial thromboplastin time
(aPTT), prothrombin time/international normalised ratio (PT/INR), fibrinogen and
D-dimer assays , before and 48hours after surgery.
Results
Three thousand and twenty-eight (3,028) surgical case notes in these three
departments of surgeries carried out in 2012 were reviewed for clinical and
laboratory evidence of VTE and the pattern of usage of prophylactic
anticoagulant. Eighty two patients in the prospective arm were recruited
preoperatively and assessed for the risk of VTE. The implementation of
prophylactic anticoagulant and the modality chosen by the managing team
was documented. Venous blood (7.5mls) was taken preoperatively and 48hours
postoperatively for FBC, aPTT, PT/INR, fibrinogen and D-dimer assays using
standard operating procedures. Data was analysed using descriptive and
inferential statistics and p-value ≤0.05 was used to determine the level of
statistical significance.
The mean age of cases reviewed in the retrospective arm was 43.1±16.1years
while it was 44.5±15.0 years for patients in the prospective arm. Five hundred
and eighty-nine (19.4%) of the patients in the retrospective arm had prophylaxis
with the majority( 90.1%) being orthopaedic patients. Ten (12.2%) of the patients
in the prospective arm had prophylaxis with 80% being orthopaedic patients.
Low molecular weight heparin was the most popular agent administered in both
arms (96.4% and 100% respectively). Seventeen (0.56%) of the patients in the
retrospective arm developed clinically overt VTE with or without prophylactic
anticoagulant but no patient developed same in the prospective arm.The
majority of the patients in the prospective arm had moderate risk 41(50.0%) or
high risk 35 (42.7%) for VTE when Tool 1 was used, while tools 2 and 3 placed
most of the patients 54 (65.9%) and 76 (92.7%) respectively in the low risk
group.There was no significant correlation between the total risk score (tool 1)
and the laboratory parameters carried out both pre- and post-operatively. Also,
there was no significant difference between pre and post operative values for
the parameters measured. The D-dimer value was elevated (>400ng/l) in 82.9%
of the patients pre-operatively and 85.4% post-operatively with 76.8% (p=0.61) in
the moderate and high risk groups pre operatively and 78%(p=0.68) post
operatively. Fibrinogen was also elevated in 56.1% patients pre-operatively and
61% post-operatively with 51.2% (p=0.34) and 59.8% (p=0.42) in the moderate
and high risk group pre and post operatively.
Conclusion
Most of the patients undergoing surgery at OAUTHC, Ile-Ife have moderate to
high risk for VTE but the use of anticoagulant prophylaxis is low when compared
with other places. The laboratory investigations assessed had no significant
correlation with the total risk scores which limited their usefulness as screening
tools.

RISK FACTORS FOR VENOUS THROMBOEMBOLISM IN SURGICAL PATIENTS AT OBAFEMI AWOLOWO UNIVERSITY TEACHING HOSPITALS COMPLEX, ILE-IFE