Elsevier

Surgery (Oxford)

Volume 25, Issue 9, September 2007, Pages 391-398
Surgery (Oxford)

Critical illness and intensive care
Acute renal failure

https://doi.org/10.1016/j.mpsur.2007.07.001Get rights and content

Abstract

Acute renal failure (ARF) describes a syndrome characterized by a rapid decline in the ability of the kidney to eliminate waste products, regulate acid–base balance, and manage water homeostasis. ARF is a common clinical problem for the surgical patient, is associated with increased perioperative morbidity and mortality, and presents major diagnostic and therapeutic challenges. A consensus definition for ARF has recently been developed that will hopefully guide future research and work towards improving outcomes.

For simplicity, the cause of ARF is divided into probable sources of renal injury (i.e. pre-renal, renal (parenchymal) and post-renal). Several common syndromes predispose to ARF, including major surgery (specifically with cardiopulmonary bypass), rhabdomyolysis, contrast-induced nephropathy and sepsis-associated ARF. The general principles for management of ARF include identification, treatment and/or removal of the precipitant(s) while maintaining physiological homeostasis to allow renal recovery; this may include the early initiation of renal replacement therapy (RRT). There is evidence suggesting that an increased dose of RRT may improve survival. Continuous RRT (CRRT) is possibly the commonest method of RRT in critically ill patients. CRRT may improve rates of renal recovery. Conventional intermittent haemodialysis, which was being used less frequently, is now reappearing in the form of slow low-efficiency dialysis.

Section snippets

Definition

Numerous definitions of ARF have been published. A consensus definition for ARF has recently been developed and validated in hospitalized and critically ill patients.1, 2, 3 This definition divides renal dysfunction into the categories of risk, injury and failure (RIFLE) based on bedside measurements of kidney function (e.g. changes to serum creatinine and urine output; Figure 1). The RIFLE classification is likely to be the dominant approach to defining ARF for the next 5 to 10 years. With

Risk factors

The risk factors for ARF are listed in Table 1.

Assessment of renal function

Renal function is complex (acid–base balance, water balance, regulation of calcium and phosphate, erythropoiesis, disposal of some cytokines, lactate removal).

Glomerular filtration rate (GFR): monitoring of renal function in the clinic is reduced to the indirect assessment of GFR by the measurement of serum creatinine and urea. These waste products are insensitive markers of GFR and are heavily modified by numerous factors (e.g. age, sex, muscle mass, nutritional status, corticosteroid use,

Clinical classification

Dividing causes according to the probable source of renal injury is the most useful approach to the diagnosis of ARF.

Major surgery

ARF is a common complication after major surgery.8 The incidence depends on comorbidity, preoperative kidney function, and the type and urgency of surgery. Intraoperative events can hinder kidney function (Table 4); any of these factors, alone or in combination, may contribute to critical reductions in renal blood flow and ischaemia, impaired delivery of oxygen (see Ward, CROSS REFERENCES), and toxin- or inflammatory-mediated injury. Postoperative ARF is believed to be, in part, mediated by

Resuscitation

Intravascular volume must be maintained or rapidly restored; this may require admission to an ICU and invasive haemodynamic monitoring (central venous catheter, arterial cannula, pulmonary artery catheter or pulse contour cardiac output catheters). Oxygenation must be maintained. An adequate haemoglobin concentration (at least >70 g/l) must be maintained or restored. Some patients remain hypotensive once intravascular volume has been restored (mean arterial pressure <70 mmHg). Hypotension

Diagnostic investigations

An aetiological diagnosis of ARF must be determined, and may be obvious on clinical grounds. In many patients, all possibilities should be considered and common treatable causes excluded using simple investigations.

Urinalysis is a simple and non-invasive test that can yield important diagnostic information. One important investigation is microscopic examination of the urinary sediment.

Anaemia: evidence of marked anaemia in the absence of blood loss may suggest acute haemolysis, thrombotic

Basic concepts

The principles of management of established ARF is shown in Table 7.

Nutritional support (see Kaushal, CROSS REFERENCES) must be started early and must contain adequate calories (30–35 Kcal/kg/day as a mixture of carbohydrates and lipids) and protein (at least 1–2 g/kg/day). There is no evidence that specific renal nutritional solutions are useful.

Hyperkalaemia (>6 mmol/l) must be promptly treated with insulin and dextrose, bicarbonate if acidosis is present, nebulized salbutamol, or all of the

Prognosis

Renal recovery after ARF is an important measure of morbidity. Persistent chronic renal impairment or need for RRT can negatively influence quality of life, and contribute to considerable healthcare expenditures. Recovery to independence from RRT occurs in ≈68–85% of critically ill patients by the time of hospital discharge, and usually peaks by 90 days.5, 8 Older patients and those with pre-existing comorbidities such as chronic kidney disease or cardiovascular disease are less likely to

Summary

The branch of nephrology concerned with ARF (‘critical care nephrology’) has undergone many advances in recent years, but mortality remains high because sicker, older patients undergo more complex, prolonged and higher-risk surgery. Consensus definitions have been developed that guide research and potentially provide better outcomes.

The general principles of management consist of identification, treatment and/or removal of the precipitant(s) while maintaining physiological homeostasis to allow

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