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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
Applied Sciences Lecture Course

Oliguria in a surgical patient

Mahesh Nirmalan MD, FRCA, PhD

Consultant, Critical Care Medicine

Manchester Royal Infirmary

case history 1
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
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
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
slide5
PRE

POST

Parenchymal organ

systematic approach to oliguria
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

slide7
GFR

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
What is the relationship between Mean Arterial Pressure (MAP) and urine output in a patient?
rbf gfr uop vs map
RBF→ GFR→UOP Vs MAP
  • 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
Renal blood supply

Cortical Vs Juxtamedullary nephrons

pressure diuresis and pressure natriuresis
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
reduction in map is the most frequent cause for reduced uop in the immediate peri operative period
Cardiac output

Peripheral vascular resistance

Contractility

Effective Blood volume

Vascular tone

Reduction in MAP is the most frequent cause for reduced UOP in the immediate peri-operative period.
slide13
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
Net filtering pressure
  • Afferent arteriolar constriction reduces NFP
  • Pain
  • Hypovolaemia
  • Anxiety
slide15
Cardiac Output

Effective Renal

Functions

MAP

Local Glomerular

Factors

slide18
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
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

how is auto regulation of glomerular filtration rate achieved
Glomerulo-Tubular Feedback

Renin-Angiotensin system

Myogenic autoregulation

How is auto-regulation of glomerular filtration rate achieved?
slide21
Angiotensin II

Flow rate in loop of Henle

Macula Densa NaCL

Glomerular Hydrostatic pressure

Glomerular Filtration Pressure

Na Cl resorption

Arterial Pressure

Renin

Afferent arteriole Resistance

GFR

Efferent Arteriole Resistance

slide23
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
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
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
slide26
Glomerular Filtration

Tubular Re-absorbtion

Pre-Renal

MAP

CO

Post-renal

Blocked catheter

Retention

Damage to ureters

Renal

Renal parenchymal damage

Pre-existing

Acquired during the peri-operative period

Sepsis

Neprotoxic agents

“Acute Tubular necrosis”

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

Urine production

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