Oliguria in a surgical patient
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Applied Sciences Lecture Course. Oliguria in a surgical patient. Mahesh Nirmalan MD, FRCA, PhD Consultant, Critical Care Medicine Manchester Royal Infirmary. Case history 1.

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Oliguria in a surgical patient

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Applied Sciences Lecture Course

Oliguria in a surgical patient

Mahesh Nirmalan MD, FRCA, PhD

Consultant, Critical Care Medicine

Manchester Royal Infirmary

Case history 1

A 68 years old; open repair of a 7cm diameter infra-renal aortic aneurysm; 2litre blood loss; transfused 5 Units of packed red cells; duration of the surgery was 250 minutes; admitted to ICU post-op; mechanically ventilated.

Hourly urine output was approximately 15-20 ml.hr-1 for 8 hours.

What are your initial thoughts and considerations?

Case History 2

70 Years old female

Radical Cystectomy

Difficult dissection due to adhesions

4 hour procedure

1 litre blood loss

In ward…….called to review 5 hours post surgery

No urine output since surgery

What are your initial thoughts and considerations?

When managing a patient with reduced urine output after major surgery your first response should be:

  • Give fluids

  • Give diuretics

  • Give dobutamine

  • Give vasopressors

  • None of the above



Parenchymal organ

New problems

Exacerbation of pre-existing problems

Systematic approach to oliguria

  • Pre renal causes

    • Renal flow, perfusion pressure

  • Renal causes

    • Acute tubular necrosis(ATN)

    • Neprotoxicity

  • Post renal causes

    • Obstruction: ureters, bladder, prostate,

      urethra, catheter


UOP = Volume filtered at the glomerulus – Volume reabsorbed by the renal tubules

GFR Vs Clearance

What is the relationship between Mean Arterial Pressure (MAP) and urine output in a patient?


  • RBF= 25% of cardiac output

  • Way in excess of metabolic needs

  • Marked regional differences

  • Cortices: luxury perfusion

  • Medullary flow is low: why?

  • Autoregulation of RBF and GFR

  • UOP is proportional to the MAP

Regulation curve is shifted to the right in patients with chronic hypertension

Renal blood supply

Cortical Vs Juxtamedullary nephrons

Pressure diuresis and pressure natriuresis

  • Auto-regulation of GFR is not absolute

  • Small differences in GFR leads to large differences in UOP

  • Increased venous pressure in the vasa-recta

  • Reduced production of angiotensin

Cardiac output

Peripheral vascular resistance


Effective Blood volume

Vascular tone

Reduction in MAP is the most frequent cause for reduced UOP in the immediate peri-operative period.

Renal perfusion pressure

Net Filtering pressure

Cardiac output or Renal blood flow

Afferent & Efferent

Vascular Tone

Direct and Indirect effects

Other than reduced MAP what other physiological factors may account for reduced UOP in the above patient?

Net filtering pressure

  • Afferent arteriolar constriction reduces NFP

  • Pain

  • Hypovolaemia

  • Anxiety

Cardiac Output

Effective Renal



Local Glomerular


500 ml “Gelafusine” fluid challenge

What do you think of the choice of a colloidal solution and the volume (500ml) that was used during the above fluid challenge?

Colloids vs crystalloids and tissue oxygen tension after major abdominal surgery

*p < 0.05

vs HES group

Lang et al. Anesth Analg 2001;93:405–9

Glomerulo-Tubular Feedback

Renin-Angiotensin system

Myogenic autoregulation

How is auto-regulation of glomerular filtration rate achieved?

Angiotensin II

Flow rate in loop of Henle

Macula Densa NaCL

Glomerular Hydrostatic pressure

Glomerular Filtration Pressure

Na Cl resorption

Arterial Pressure


Afferent arteriole Resistance


Efferent Arteriole Resistance

Glomerulo-tubular feed back

If the patient complained of severe pain, would you consider the use of nonsteroidal anti-inflammatory drugs?

Which is the correct statement: Most non-steroidal anti-inflammatory drugs:

  • Increase the synthesis of prostaglandins

  • Increases the conversion of arachidonic acid into prostaglandins and thromboxane

  • Act as non selective COX inhibitors

  • Act as selective COX-1 inhibitors

  • Act as selective COX-2 inhibitors

The functions of the kidneys

  • Excretion of metabolic waste

  • Regulation of water and electrolyte balance

  • Regulation of ECF volume and osmolality

  • Regulation of arterial pressure: Long and short term

  • Regulation of Acid-base balance

  • Hormones: secretion, metabolism and excretion

  • Gluconeogenesis

Glomerular Filtration

Tubular Re-absorbtion





Blocked catheter


Damage to ureters


Renal parenchymal damage


Acquired during the peri-operative period


Neprotoxic agents

“Acute Tubular necrosis”

Very Rarely the primary cause of the problem in the immediate post-operative period

Urine production

Thank you

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