From the Guidelines
Oliguria in a 163 kg man is defined as urine output less than 0.5 mL/kg/hour, which would be approximately less than 81.5 mL per hour or less than 1,956 mL per day. This calculation is based on the patient's actual body weight, though some clinicians may use adjusted body weight for extremely obese patients 1. Monitoring urine output is essential for assessing kidney function and fluid status, particularly in critically ill patients. Oliguria serves as an early warning sign of acute kidney injury or inadequate perfusion of the kidneys. When caring for obese patients, it's important to recognize that using standard definitions without weight adjustment might delay recognition of decreased renal function. If oliguria is detected, prompt evaluation of the cause is necessary, including assessment of volume status, hemodynamics, and potential nephrotoxic exposures. Treatment should be directed at the underlying cause, which may include fluid resuscitation, discontinuation of nephrotoxic medications, or management of obstructive processes.
Some key points to consider in the definition and management of oliguria include:
- The importance of monitoring urine output in critically ill patients to detect early signs of acute kidney injury or inadequate perfusion of the kidneys 1.
- The use of adjusted body weight for extremely obese patients to avoid delayed recognition of decreased renal function 1.
- The need for prompt evaluation and treatment of the underlying cause of oliguria, including assessment of volume status, hemodynamics, and potential nephrotoxic exposures 1.
- The definition of oliguria as urine output less than 0.5 mL/kg/hour, which is a key indicator of acute kidney injury or inadequate perfusion of the kidneys 1.
It is also important to note that oliguria can be a complex process with various causes, not only hemodynamic changes or ‘tubular necrosis’ 1. Real-time monitoring of GFR showed that oliguria and GFR usually, but not always, show parallel changes in AKI. Oliguria is a frequent occurrence in intensive care, but is infrequently followed by AKI, as defined by a later creatinine rise.
In clinical practice, it is essential to use the most recent and highest quality evidence to guide the definition and management of oliguria, such as the study published in the Journal of the American College of Radiology in 2021 1. This study provides a comprehensive overview of the definition and management of oliguria, including the importance of monitoring urine output, the use of adjusted body weight for extremely obese patients, and the need for prompt evaluation and treatment of the underlying cause of oliguria.
From the Research
Definition of Oliguria
Oliguria is a medical condition characterized by a decreased urine output. In a 163 kg man, oliguria can be defined as a urine output of less than 400 mL per 24 hours 2.
Causes and Diagnosis
Oliguria can be caused by various factors, including:
- Transitory changes in volume status
- External influences, such as drug administration
- Acute kidney injury (AKI)
- Chronic heart failure (CHF)
Diagnosis of oliguria is typically based on the assessment of urine output, which is a relevant marker of kidney function 2.
Clinical Significance
Oliguria is an important clinical sign, as it can indicate kidney dysfunction or other underlying medical conditions. In critically ill patients, oliguria can be a predictor of adverse outcomes, including increased mortality and morbidity 3, 4.
Treatment and Management
Treatment of oliguria depends on the underlying cause and may involve the use of diuretics, such as furosemide, to increase urine output 5, 3, 4, 6. However, the effectiveness of diuretics in improving outcomes in patients with oliguria is still a topic of debate, and further research is needed to determine the optimal treatment strategies 3, 4, 6.