Global incidence and case fatality rate of pulmonary embolism following major surgery: a protocol for a systematic review and meta-analysis of cohort studies
Temgoua et al. Systematic Reviews
Global incidence and case fatality rate of pulmonary embolism following major surgery: a protocol for a systematic review and meta-analysis of cohort studies
Mazou N. Temgoua 0
Joel Noutakdie Tochie 2
Jean Jacques Noubiap 1
Valirie Ndip Agbor 4
Celestin Danwang 2
Francky Teddy A. Endomba 0
Njinkeng J. Nkemngu 3
0 Department of Medicine and sub-Specialties, Faculty of Medicine and Biomedical Sciences, University of Yaounde I , Yaounde , Cameroon
1 Department of Medicine, Groote Schuur Hospital and University of Cape Town , 7925 Observatory, Cape Town , South Africa
2 Department of Surgery and sub-Specialties, Faculty of Medicine and Biomedical Sciences, University of Yaounde I , Yaounde , Cameroon
3 Department of Anesthesia, University of Toronto , Toronto , Canada
4 Ibal sub-Divisional Hospital , Oku, North-west Region , Cameroon
Background: Pulmonary embolism (PE) is a life-threatening condition common after major surgery. Although the high incidence (0.3-30%) and mortality rate (16.9-31%) of PE in patients undergoing major surgical procedures is apparent from findings of contemporary observational studies, there is a lack of a summary and meta-analysis data on the epidemiology of postoperative PE in this same regard. Hence, we propose to conduct the first systematic review to summarise existing data on the global incidence, determinants and case fatality rate of PE following major surgery. Methods: Electronic databases including MEDLINE, EMBASE, SCOPUS, WHO global health library (including LILACS), Web of Science and Google scholar from inception to April 30, 2017, will be searched for cohort studies reporting on the incidence, determinants and case fatality rate of PE occurring after major surgery. Data from grey literature will also be assessed. Two investigators will independently perform study selection and data extraction. Included studies will be evaluated for risk of bias. Appropriate meta-analytic methods will be used to pool incidence and case fatality rate estimates from studies with identical features, globally and by subgroups of major surgical procedures. Random-effects and risk ratio with 95% confidence interval will be used to summarise determinants and predictors of mortality of PE in patients undergoing major surgery. Discussion: This systematic review and meta-analysis will provide the most up-to-date epidemiology of PE in patients undergoing major surgery to inform health authorities and identify further research topics based on the remaining knowledge gaps. Systematic review registration: PROSPERO CRD42017065126
Pulmonary embolism; Major surgery; Incidence; Mortality; Determinants; Cohort studies
Globally, about 234 million major surgical interventions
are performed each year [
] and postoperative
complications inflict a significant morbidity, mortality and
economic burden to surgical patients as well as healthcare
]. Pulmonary embolism (PE), a
lifethreatening complication of venous thromboembolism
(VTE), represents a major postoperative complication
. Indeed, surgery increases the risk of PE by fivefold
]. The pathogenesis involves the interplay of an acute
inflammatory reaction triggered by vascular endothelial
lesions due to surgical dissections [
induced by surgical stress and anaesthetic drugs [
and venous stasis due to perioperative immobilisation
and delayed rehabilitation, all described by Virchow
more than a century ago . PE is known to be relatively
frequent during major surgery, where the following
incidence rates have been reported: 0.7–30% after
orthopaedic surgery [
], 1.5–7.6% following thoracic
], 0.33–6.6% after abdominal surgery [
0.3–4.1% in gynaecologic surgery [
], 0.9–1.1% after
urologic procedures [
], and 0.6% after cardiac
surgery . Furthermore, despite the widespread adoption
of thromboembolic prophylactic measures, PE accounts
for a 30-day major surgery-specific case fatality rate
ranging between 16.9 and 31% [
] and a 37% 
1year case fatality rate following major surgery.
In spite of recent advances in the diagnosis of PE,
notably with the advent of multi-detector computed
tomography pulmonary angiography and ventilation-perfusion
], PE remains the most common cause of
preventable death in surgical patients that is often easily
]. Furthermore, these diagnostic
imaging tests [
] have been described to be inaccessible for
the majority of patients with suspected PE in
resourcelimited settings [
]. While several patients with PE
remain asymptomatic, others will experience a fatal PE as
the first manifestation of thromboembolism [
Therefore, identifying perioperative risk factors of PE is an
important step towards prevention of PE in patients
undergoing major surgery, primarily via prompt
thromboembolic prophylaxis [
]. Hence, this
protocol is designed for a systematic review and meta-analysis
to critically synthesise the global incidence, determinants
and case fatality rate of PE following major surgery.
Findings will provide evidence on the current
epidemiology of PE following major surgery and inform
policymakers on major determinants of PE for which control
interventions can be tailored to curb this burden.
The aim of this systematic review and meta-analysis is
to ascertain the global incidence, determinants and case
fatality rate of PE after major surgery.
To this end, the proposed systematic review will answer
the following questions:
1. What is the global incidence of PE in patients
undergoing major surgery?
2. What are the determinants of PE among patients
undergoing major surgery?
3. What is the specific case fatality rate for PE after
Methods and design
This review is reported in accordance with the Preferred
Reporting Items for Systematic Review and
MetaAnalysis Protocols (PRISMA-P) 2015 Guidelines [
and applicable to observational studies. An additional
file shows this in more detail (see Additional file 1).
Criteria for considering studies for the review
1. We intend to include cohort studies reporting any of
the following three data: incidence, determinants,
and case fatality rate of PE following major surgical
procedures round the world. Cohort studies that
report other postoperative complications including
PE will be included provided they present data
enabling the calculation of any of the
aforementioned three endpoints.
2. Study participants will be all patients who
underwent a major surgical intervention. Major
surgery will be defined as any intervention involving
the incision, resection, manipulation or suturing of
tissue and that requires general or regional
anaesthesia or profound sedation for analgesia [
4. The diagnosis of PE will be based on computed
tomographic pulmonary angiography and
ventilation-perfusion scintigraphy as defined by the
European Society of Cardiology [
] and the
American Heart Association [
]. Studies reporting PE
based on histopathology diagnoses made at autopsy
shall also be considered. We intend to consider all
published and unpublished data from inception to
April 30, 2017.
5. Study settings: health care facilities in either rural or
6. No language restriction.
1. Studies where there are no appropriate diagnostic
tool for PE.
2. For duplicate publications, only the publication with
the most person-years will be retained.
Search strategy for study identification
We intend to search MEDLINE, EMBASE, SCOPUS,
WHO global health library (including LILACS), Web of
Science and Google scholar from January 1, 1997, to
April 30, 2017, for published studies on PE in adults
undergoing major surgery. A comprehensive search
strategy combining key search terms of different major
surgical procedures cross-referenced with pulmonary
embolism will be used in order to obtain the maximum
possible number of studies. The search strategy for
MEDLINE/PubMed is shown in Table 1. This will be
adapted for the other databases. We will scan the
reference lists of retrieved articles in order to identify any
additional relevant studies. Our search will extend to
include grey literature from book chapters, conference
proceedings, theses, non-governmental organisations
and government reports.BTW70647BTW70647
(“Non-cardiac surgery” [tw] OR “Non-cardiac surgical
procedure” [tw] OR “Gynaecologic surgery” [tw] OR
“Gynecologic surgery” [tw] OR “Hysterectomy” [tw] OR
“Caesarean section” [tw] OR “Caesarean delivery” [tw]
OR “Wertheim” [tw] OR “Ovarian cystectomy [tw] OR
“Myomectomy [tw] OR “Fimbrioplasty [tw] OR
“Cervicectomy” [tw] OR “Oophorectomy” [tw] OR
“Salpingoophrorectomy” [tw] OR “Salpingectomy” [tw]
OR “Vaginectomy” [tw] OR “Vulvectomy” [tw] OR
“Salpingostomy” [tw] OR “Hysterotomy” [tw] OR
“Abdominal Surgery” [tw] OR “Visceral surgery” [tw] OR
“Laparotomy” [tw] OR “Oesophagectomy” [tw] OR
“Nissen fundoplication” [tw] OR “Hernia repair” [tw] OR
“Herniorraphy” [tw] OR “Appendectomy” [tw] OR
“Appendicectomy” [tw] OR “cholecystectomy” [tw] OR
“Colectomy” [tw] OR “Colostomy” [tw] OR “Gastrectomy”
[tw] OR “Gastrotomy” [tw] OR “Gastroplasty” [tw] OR
“Gastroduodenostomy” [tw] OR “Gastroenterostomy”
[tw] OR “Ileostomy” [tw] OR “Jejunostomy” [tw] OR
“Colostomy” [tw] OR “Cholecystostomy” [tw] OR
“Splenectomy” [tw] OR “Splenoplexy” [tw] OR “Whipple”
[tw] OR “Pancreatectomy” [tw] OR
“Pancreatoduodenectomy” [tw] OR “Protocolectomy”
[tw] OR “Omentopexy” [tw] OR “Hepatectomy” [tw] OR
“Hepatoportoenterostomy” [tw] OR “Sigmoidostomy”
[tw] OR “Sphinterotomy” [tw] OR “Pyloromyotomy” [tw]
OR “Hemorrhoidectomy” [tw] OR “Urology surgery” [tw]
OR “Nephrectomy” [tw] OR “Lithotomy” [tw] OR “Urinary
Cystectomy” [tw] OR “Nephrostomy” [tw] OR
“Ureterostomy” [tw] OR “Nephrotomy” [tw] OR
“Nephropexy” [tw] OR “Urethropexy” [tw] OR “Kidney
transplantation” [tw] OR “Adenectomy” [tw] OR
“Prostatectomy” [tw] OR “Urethroplasty” [tw] OR
“Pyeloplasty” [tw] OR “Orthopedic surgery” [tw] OR
“Osteosynthesis” [tw] OR “Fracture fixation” [tw] OR
“Fracture stabilisation” [tw] OR “Internal fixation” [tw] OR
“External fixation” [tw] OR “Hip replacement” [tw] OR
“Knee replacement” [tw] OR “Arthroplasty” [tw] OR
“Ostectomy” [tw] OR “Osteotomy” [tw] OR “Arthrotomy”
[tw] OR “Laminotomy” [tw] OR “Foraminotomy” [tw] OR
“Epiphysiodesis” [tw] OR “Arhrodesis” [tw] OR “Ligament
reconstruction” [tw] OR “Limb Amputation” [tw] OR
“Fasciotomy” [tw] OR “Prosthestic surgery” [tw] OR
“Prosthesis” [tw] OR “Spinal Surgery” [tw] OR “Back
Surgery” [tw] OR “Facetectomy” [tw] OR “Laminectomy”
[tw] OR “Discectomy” [tw] OR “Thoracotomy” [tw] OR
“Thoracostomy” [tw] OR “Pneumectomy” [tw] OR
“Pneomotomy” [tw] OR “Lobectomy” [tw] OR
“Bronchotomy” [tw] OR “Tracheotomy” [tw] OR
“Pleuridesis” [tw] OR “Lung transplantation” [tw] OR
“Neurosurgery” [tw] OR “Craniotomy” [tw] OR
“Craniectomy” [tw] OR “Hemispherectomy” [tw] OR
“Ureterosigmoidostomy” [tw] OR “Fistulotomy” [tw] OR
“Cerebral lobectomy” [tw] OR “Cerebral lobotomy” [tw]
OR “Hypophysectomy” [tw] OR
“Amydalohippocampectomy” [tw] OR “Ventriculostomy”
[tw] OR “Ventriculoperitoneal shunting” [tw] OR
“Pallidotomy” [tw] OR “Thalamotomy” [tw] OR
“Cingulotomy” [tw] OR “Cordotomy” [tw] OR
“Rhizotomy” [tw] OR “Brain biopsy” [tw] OR
“Ganglionectomy” [tw] OR “Symapathectomy” [tw] OR
“Neurectomy” [tw] OR “Axotomy” [tw] OR “Vagotomy”
[tw] OR “Nerve biopsy” [tw] OR “Endocrine surgery” [tw]
OR “Thyroidectomy” [tw] OR “Thyroid lobectomy” [tw]
OR “Parathyroidectomy” [tw] OR “Adrenalectomy” [tw]
OR “Pinealectomy” [tw] OR “Ophthalmic surgery” [tw]
OR “Punctoplasty” [tw] OR “Trabeculopathy” [tw] OR
“Photorefractive keratectomy” [tw] OR “Trabeculectomy”
[tw] OR “Iridectomy” [tw] OR “Virectomy” [tw] OR
“Dacryocystorhinostomy” [tw] OR “Radial keratotomy”
[tw] OR “Corneal transplantation” [tw] OR “ENT surgery”
[tw] OR “Ear nose throat surgery” [tw] OR “Otoplasty”
[tw] OR “Stapedectomy” [tw] OR “Mastoidectomy” [tw]
OR “Auriculectomy” [tw] OR “Myringotomy” [tw] OR
“Rhinoplasty” [tw] OR “Septoplasty” [tw] OR
“Rhinectomy” [tw] OR “Laryngectomy” [tw] OR
“Tracheostomy” [tw] OR “Sinusotomy” [tw] OR
“Cricothyroidotomy” [tw] OR “Cricothyrotomy
Tonsillectomy” [tw] OR “Adenoidectomy” [tw] OR
“Palatoplasty” [tw] OR “Uvuloplasty” [tw] OR
“Gingivectomy” [tw] OR “Glossectomy” [tw] OR “Cardiac
surgery” [tw] OR “Valvuloplasty” [tw] OR
“Pericardiectomy” [tw] OR “Pericardiotomy” [tw] OR
“Cardiotomy” [tw] OR “Coronary artery bypass surgery”
[tw] OR “Heart transplantation” [tw] OR “Vascular
surgery” [tw] OR “Angioplasty” [tw] OR “Endarectomy”
[tw] OR “Lympahatic surgery” [tw] OR “Thymectomy”
[tw] OR “Lymphadenectomy” [tw] OR “Thymus
transplantation” [tw] OR “Spleen transplantation” [tw])
Pulmonary embolism [tw] OR Pulmonary emboli [tw]
OR Thromboembolism [tw] OR Thromboembolic events
[tw] OR Thromboembolic complications [tw] OR
Venous thromboembolism [tw]
#1 AND #2 Limits: 01/01/1997 to 31/04/2017
All studies identified by the search strategy will be
entered into EndNote to assess and exclude duplication of
records. This will be subsequently uploaded into
EppiReviewer, an Internet-based software program which
eases collaboration among reviewer authors during the
study selection process. Prior to the screening of studies,
the team will develop and screen questions and forms
for two levels of assessment based on the eligibility
criteria. Abstracts and full-text articles will be uploaded
with screening questions to Eppi-Reviewer.
Study screening and selection
Two review authors (JNT and MNT) will independently
screen the titles and abstracts of studies yielded by the
search against the eligibility criteria. We shall retrieve full
reports for all study titles that appear to meet the eligibility
criteria or where there is any contingency. The investigators
will then screen the full-text reports and decide whether
these meet the inclusion criteria of the systematic review.
We intend to seek additional data from corresponding
authors in the event that the publication is unclear and
hence may be subject to multiple interpretations.
Discrepancies will be solved by a third author (NJN). We
will record the reasons for excluding studies.
With the aid of a standardised and pre-tested data
extraction form, two investigators (VNA and CD) will
extract data independently from included studies. Any
disagreement shall be resolved by discussion, and a third
investigator (FTAE) will adjudicate unresolved
disagreements. A flowchart will be used to demonstrate the
entire study selection and data extraction processes.
We will seek information concerning the following study
variables: the year the study was conducted and
published, the language of publication, demographic data of
participants (mean age, gender proportions), setting
(urban or rural hospital), sample size, number and
proportion with PE, type of major surgical procedure, risk
factors for PE, PE-related mortality rate, predictors for
PE-related mortality and measures of association
(relative risks, odds ratios, p values and confidence intervals)
will be recorded. If measures of association cannot be
calculated or are not reported in the primary study, we
shall contact the concerned authors via email for
Assessment of risk of bias
To assess the risk of bias within included studies, two
review authors (JJN and MNT) will independently assess
the risk of bias within included studies using the
Newcastle-Ottawa Scale (NOS) [
]. An additional file
shows this scale in detail (see Additional file 2). A
judgement as to the possible risk of bias in each study will be
rated as ‘high risk’, ‘moderate risk’ or ‘low risk’. In the event
of insufficient details reported in a study, we will score the
risk of bias as ‘uncertain’ and the investigators of the said
primary study will be contacted for more information. We
intend to present the risk of bias in a table. Also, we will
compute graphic representations of potential bias within
and across studies using RevMan V.5.3. Disagreements
will be resolved first by discussion and then by consulting
a third author (NJN) for arbitration.
Data synthesis, analysis and assessment of heterogeneity
Data on the incidence, case fatality rate and
determinants of PE following major surgery will be summarised
in demographic characteristic (patient age, sex), clinical
characteristics (type of major surgery, pregnancy,
obesity, prior venous thromboembolism, active malignancy,
infection, intensive care unit admission, trauma or
fracture, hormonal therapy, immobilisation), study setting and
the time the study was conducted and published.
Heterogeneity will be assessed using the chi-square (χ2) test on
Cochran’s Q statistic and quantified by calculating the
Isquared (I2) statistic [
]. I2 values of 25, 50 and 75% will
represent low, medium and high heterogeneity,
respectively. In the event of no substantial heterogeneity across
studies, a meta-analysis will be performed for the global
incidence and case fatality rates of PE following major
surgery across studies with similar characteristics. To this
end, a random effects meta-analysis model will be used to
obtain an overall summary estimate of the incidence and
mortality rate across included studies. Furthermore, an
inverse variance weighting method will be used for a
metaanalysis of risk ratios. Where substantial heterogeneity will
be detected despite lumping similar studies, subgroup
analyses will be conducted to explore the possible sources
of heterogeneity using the following grouping parameters:
gender, age, study setting, the time the study was
conducted and published, diagnostic methods and type of
major surgery. In the event that the data cannot be pooled
due to substantial heterogeneity, only a narrative summary
of the findings will be done.
Assessment of reporting bias
We will assess publication bias and selective reporting by
using funnel plots and Egger’s test. Data will be analysed
using Stata software version 13 (Stata Corp V.13, TX, USA).
In order to limit outcome reporting bias, we do not intend
to make any amendment to this protocol. However, in the
event of any amendment, we will report the date of the
amendment, a description of the modification done and
the rationale. Only protocol amendments approved by all
the authors will be documented by the guarantor.
Pulmonary embolism is a life-threatening complication
of deep venous thrombosis. The risk of incidence is
increased by major surgery. A summary and meta-analysis
of contemporary cohort studies reporting its incidence,
determinants and case fatality rate in patients
undergoing major surgery will be invaluable in assessing its true
impact in the perioperative period, and informing health
authorities on major determinants of PE for which
control interventions can be geared to curb this burden.
Additional file 1: Preferred Reporting Items for Systematic Review and
Meta-Analysis Protocols (PRISMA-P) 2015 Guidelines (DOCX 17 kb)
Additional file 2: Newcastle-Ottawa Scale (DOCX 14 kb)
This review received no specific grant from any funding agency in the
public, commercial, or not-for-profit sectors.
Availability of data and materials
JNT, JJN, MNT and NJN conceived the study. JNT drafted the manuscript.
JJN, MNT, VNA, CD, TFAE and NJN critically revised the protocol for
methodological and intellectual content. All the authors read and approved
the final manuscript.
Ethics approval and consent to participate
Consent for publication
The authors declare that they have no competing interests.
Springer Nature remains neutral with regard to jurisdictional claims in
published maps and institutional affiliations.
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