A STUDY OF THE MAGNITUDE, PATTERN AND PREDICTORS OF POST-OPERATIVE ACUTE KIDNEY INJURY AT THE UNIVERSITY OF ILORIN TEACHING HOSPITAL

TABLE OF CONTENTS

                                                                                                                                            PAGE

DECLARATION ……………………………………………………………………..              i

CERTIFICATION……………………………………………………………………..            ii

ACKNOWLEDGEMENT……………………………………………………………..          iv

DEDICATION………………………………………………………………………….           v

TABLE OF CONTENTS……………………………………………………………..           vi

LIST OF ABBREVIATIONS…………………………………………………………         viii

LIST OF TABLES…………………………………………………………………….            x

LIST OF FIGURES……………………………………………………………………         xi

SUMMARY …………………………………………………………………………….          1

CHAPTER ONE: 

INTRODUCTION………………………………………………………………… 3

CHAPTER TWO:

LITERATURE REVIEW……………………………………………………….. 8

CHAPTER THREE: 

SUBJECTS, METHODS AND MATERIALS………………………………… 29

CHAPTER FOUR:

RESULTS………………………………………………………………………. 40          

PAGE 

CHAPTER FIVE:

DISCUSSION…………………………………………………………       59

LIMITATIONS………………………………………………………….      64

CONCLUSION…………………………………………………………     65

RECOMMENDATIONS………………………………………………… 66

REFERENCES…………………………………………………………………     67

SUMMARY

BACKGROUND: Acute deterioration in renal function is a common entity that may occur within the community or hospital setting. Acute kidney injury occurring within the hospital setting is associated with an increased length of hospital stay, an increased cost of health care with an attendant increased demand on scarce health care resources and an increase in mortality.  Surgery, among other factors, is a recognized cause of AKI in the hospitalized patient.  The magnitude of AKI in Nigeria has been described among various in-patient groups such as among intensive care and medical unit patients but there is however a paucity of data on AKI among surgical patients. This study therefore set out to determine the magnitude of post-operative acute kidney injury among surgical patients in a tertiary hospital in Nigeria.

AIMS: The aim of this study was to determine the magnitude of acute kidney injury in post-surgical patients at the University of Ilorin Teaching Hospital, Ilorin and its associated predictors in these patients. It also set out to establish the association between patient outcomes and severity of post-operative acute kidney injury.

METHODS:  A total of 182 patients consisting 122 surgical patients and 60 medical patients were consecutively recruited via convenience sampling. A structured proforma was used to obtain socio-demographic characteristics and relevant clinical information. A physical examination was also done. Patients with baseline elevated serum creatinine were excluded. Acute kidney injury (AKI) was determined using the Acute Kidney Initiative Network (AKIN) criteria.  The incidence of AKI, the predisposing factors and its predictors were determined. The relationship between severity of AKI and patient outcome was also determined.

RESULTS: One hundred and twenty two surgical patients (cases) and 60 age- and sexmatched medical patients (controls) were recruited for the study. The mean ages of cases and controls were 44.2 ± 15.4 and 47.9 ± 14.0 years (p= 0.115) respectively while the proportion of males was 63.1% and 65.0% (p= 0.804) in each respective group. The median admitting plasma creatinine was76µmol/L and 98µmol/L (p= 0.303) among cases and controls respectively. The incidence of AKI was 15.6% among cases and 21.7% controls (p=0.597).  Cases that had orthopedic surgical procedures had the highest incidence of post-operative AKI (20.7%) while patients that had urologic surgical procedures had the lowest incidence of AKI (5.0%). The correlate of AKI in the postsurgical patient was the amount of fluid administered intra-operatively (r= -0.595, p= 0.007). Using stepwise multiple linear regression the identified predictors of postoperative AKI were the amount of intraoperative fluid administered (r² = 0.337) and the combination of pre-operative PCV and administered fluid intra-operatively (r² = 0.488). Across all AKIN severity stages, 63.2% of patients with post-operative AKI returned to baseline admitting serum creatinine levels (i.e. recovery) in 7 days while no patient required renal replacement therapy or died.  There was no association between the severity stage of AKI and the recovery of renal function.  Also, there was no significant association found between severity stage of AKI and length of hospital stay.

CONCLUSION: Acute kidney injury is common in our environment. Amongst surgical patients, there is the highest preponderance in orthopaedic in-patients and the least in urologic patients. The amount of intra-operative fluid administered and preoperative PCV were the most important predictors.

 

CHAPTER ONE

1.1                                                   INTRODUCTION

Acute kidney injury (AKI) is defined as a sudden decrease in glomerular filtration rate (GFR) with a rise in blood urea nitrogen (BUN) and creatinine.¹ The clinical entity of acute renal dysfunction was first described by Homer Smith as “acute renal failure”

(ARF) in 1951 to describe acute kidney dysfunction associated with traumatic injury.² For more than five decades after the introduction of the term into the medical lexicon, there was no universally acceptable and applicable definition for acute renal disturbances to enable uniform case identification and description. The term ARF was thus applied to a very wide range of acute renal disturbances. Indeed, surveys revealed the use of at least 35 definitions in literature, and more than 200 definitions in clinical

practice by critical care nephrologists, for ARF.^3,4   All these varied definitions had their focus on severe forms of acute renal impairment as the term “failure” inherently excluded mild forms of acute renal dysfunction.⁵  Due to the lack of uniformity in definition of ARF, its incidence, prevalence, morbidity and mortality trends and their implications for public health could not be ascertained.

In 2004, a consensus definition for AKI was introduced by the Acute Dialysis Quality Initiative (ADQI) group with a view to standardizing the criteria for establishing the presence or absence of ARF and, in addition, defining severity classes of ARF.⁶  It redefined the entire spectrum of acute renal dysfunction, encompassing early, mild and severe forms of dysfunction requiring renal replacement therapy (RRT). The consensus definition termed RIFLE (R-risk, I– injury F-failure, L– loss, E– end stage kidney disease) identified AKI as a spectrum consisting of 3 severity categories (Risk, Injury and Failure) and 2 outcome categories (Loss and End stage Renal Disease). The Acute Kidney Injury Network (AKIN) in 2007 introduced the term “acute kidney injury” (AKI) to replace ARF and also made refinements to ADQI definition and staging system with a view to increasing the sensitivity of the criteria.⁷ One of the considerations that influenced the adoption of this term was the recognition that even relatively modest changes in serum creatinine are highly associated with adverse outcomes in hospitalized patients.⁸  Also a definition which captures minor deteriorations in glomerular filtration rate (GFR) and kidney injury would allow the early detection and intervention of the clinical condition³. Since its introduction, AKI is gradually replacing the term acute renal failure (ARF) in literature.

Acute kidney Injury may occur within the community or hospital setting.  It is a commonly encountered event in the hospital setting occurring in 5-7% of hospitalized patients.^9,10   Within the hospital setting, AKI is common in the Intensive Care Unit ICU, burns unit, medical wards and surgical wards.^11–16  The occurrence of AKI in these various settings is associated with adverse outcomes such as prolonged hospital stay,

increased cost of care, need for renal replacement therapy and even death.^11–16 Causes of AKI in the hospital-setting include volume depletion, aminoglycoside use, surgery and sepsis and the recognized risk factors for mortality are  gender (male), presence of co-morbid diseases and the pathophysiologic type of AKI (intrinsic renal

AKI and hemodynamically-mediated AKI).^9,10,17

The occurrence and outcomes of AKI have been variously described in Nigeria among medical admissions and in the ICU.^11,15,18,19 In the study by Chijioke  among medical admissions 79% of affected individuals were less than 40 years old while mortality was found to be as high as 54.7%.¹⁵ Mortality was 35.7% among those who had dialytic intervention. In an ICU cohort, Okunola et alreported a 19.6% prevalence of ARF using the criteria of rapidly rising serum urea and creatinine (from a baseline of 8mmol/L and 140µmol/L respectively) and urine output < 400mls/24hrs; they also found that the severity of ARF according to LIANO score [and not according to the acute physiologic and chronic health II (APACHE II) severity of disease scoring system] correlated with patient outcomes.¹¹

AKI has been poorly characterized among post-operative patients in developing countries. Carmichael et al described the incidence of post-operative AKI (PO-AKI) as ranging from 5% of all hospital admissions to 31% of patients undergoing cardiac surgery.²⁰  AKI in the post-operative patients is associated with an increased occurrence of ICU admissions, increased length of hospital stay and, an increased incidence of gastrointestinal bleeds, respiratory tract infections and sepsis.²¹ Aetiologic considerations for PO-AKI include pre-operative factors such as pre-existing renal dysfunction and intra-operative factors such as hypovolaemia.²² Mortality rate in this group of patients in developed nations is high despite the availability and easy access to cutting edge technology in intensive care and dialysis modalities.²³ Due to the significant morbidity and mortality associated with PO-AKI the need thus arises to describe its magnitude and outcomes among Nigerian post-operative patients.

 

 

 

 

 

1.2                                                   JUSTIFICATION

The pattern of AKI in surgical patients in developing nations has not been well characterized as it has been in developed/industrialized nations. Studies also abound in industrialized nations which, in addition to describing the magnitude of  AKI in post operative patients as a whole, further characterize the pattern of AKI in specific surgical groups.24–26

An extensive literature search on AKI in Nigeria and other developing countries however yields a paucity of information on the prevalence, incidence, determinants, or outcomes of AKI in post-operative patients; this is in contrast to the availability of literature on other causes of acute kidney injury.

This gap in knowledge has made the development of position statements and best practices guidelines that best suit the Nigerian setting for the prevention and management of AKI in postoperative patients difficult. Deductive reasoning will suggest that the magnitude of post operative AKI (PO-AKI) may be quite significant given the ubiquitous problems in developing countries such as sepsis, limited availability of blood and blood products, and the probable use of older generation anaesthetic agents such as halothane for surgical procedures. In addition, there is a lack of health insurance and reimbursement plans for a majority of the populace. An unpublished review of the inpatient registers of the Nephrology unit of our centre showed that the major reason for nephrology consultation requests by the surgeons is a significant reduction in urine output post operatively.

It is therefore imperative that studies be undertaken in this group of patients to ascertain the magnitude of PO-AKI, its characteristics and its predictors. The outcome of this study may provide information that may guide clinicians about preventive and therapeutic measures. This study is thus designed to determine the magnitude (frequency), pattern and predictors of AKI following surgery with a view to addressing the factors that may be promoting or sustaining it among this group of patients.

 

1.3 AIMS AND OBJECTIVES

1.3.1 AIM OF THE STUDY

This study aims at determining the prevalence (magnitude), pattern and predictors of acute kidney injury among patients who have undergone major surgery at the University of Ilorin Teaching Hospital.

1.3.2 OBJECTIVES OF THE STUDY

1. To determine the magnitude of acute kidney injury in post operative patients at the University of Ilorin Teaching Hospital.
2. To determine the predictors of acute kidney injury in these patients.
3. To correlate the severity of acute kidney injury with patient outcome.

 

A STUDY OF THE MAGNITUDE, PATTERN AND PREDICTORS OF POST-OPERATIVE ACUTE KIDNEY INJURY AT THE UNIVERSITY OF ILORIN TEACHING HOSPITAL

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