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Renal and Urology > Fluid Balance, Assessment, and Prescribing > Flashcards

Fluid Balance, Assessment, and Prescribing Flashcards

1
Q

Describe the distribution of water in body compartments

A 
Adults= 45-60% water
•	Intracellular 66% (25L)
•	Extracellular 34%
	Interstitial (12L)
	Plasma (3L)
	Lymph
	Transcellular (CSF, joints, vitreous of the eye)
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2
Q

Compare salt distribution between extracellular, intracellular and plasma compartments

A
  • Extracellular= much more sodium but same amount of potassium than intracellular
  • Plasma= much higher protein content than extracellular
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3
Q

What are the 4 regulatory mechanisms?

A
  • Antidiuretic hormone
  • Thirst
  • Renin-angiotensin-aldosterone mechanism
  • Vasomotor regulation
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4
Q

What is serum osmolality and what is the normal range?

A
  • Measure of total solid content in serum

- Tightly regulated at 278-300 mmol (normal= 285-295)

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5
Q

How does loss of water stimulate thirst?

A

• Loss of water= increase in serum osmolality= activates osmo receptors in roof of ventricle= stimulate thirst

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6
Q

How does ADH affect water balance?

A

• Osmoreceptors stimulate ADH= stimulates thirst and reabsorption of water in the collecting duct of the kidney by transferring aquaporins / vasoconstrictor

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7
Q

How does the renin-angiotensin-aldosterone system affect water balance?

A
  • Fluid loss= reduced renal perfusion= renin secretion
  • Angiotensinogen to angiotensin 1 by renin, angiotensin 2 by ACE (pulmonary endothelium)
  • A2= vasoconstrictor so raises blood pressure; adrenal cortex stimulates aldosterone secretion to increase sodium and water reabsorption
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8
Q

Where in the brain signals fluid loss?

A

• Fluid loss= low blood pressure= reduced baroreceptor activation (aortic arch and carotid area) = signals to medulla

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9
Q

What action does the medulla have on water balance?

A
  • Medulla= increased sympathetic activity= vasoconstriction, increased stroke volume, increased heart rate/ recued parasympathetic activity increases heart rate
  • Increased heart rate and stroke volume= increased cardiac output
  • Vasoconstriction increases blood pressure
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10
Q

Compare fluid input and output

A
  • Water input: water, liquids, tissue catabolism (carbohydrates= CO2 and water)
  • Food: 700ml, drink 1500ml, 200ml catabolism
  • Output: expiration (250), sweat (100) and diffusion (350), faeces (200), excreted through kidneys (1400)
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11
Q

What are the causes of fluid loss?

A
  • Diarrhoea, vomiting, other GI losses
  • Bleeding e.g., GI haemorrhage, trauma, surgical
  • Diuresis e.g., medication, diabetes
  • Sepsis (multifactorial as fever and hypotension/ hypovolaemia contribute to fluid state)
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12
Q

Describe causes of reduced fluid intake

A
  • Reduced oral intake-thirst is powerful driver of behaviour- reduced conscious level? Unable to reach in environment?
  • Inadequate fluid supplementation-intravenous or enteral
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13
Q

Examples of fluid overload states

A
  • Heart failure
  • Liver cirrhosis and liver failure
  • Nephrotic syndrome
  • Renal failure
  • Excess fluid administration
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14
Q

What factors in the NEWS chart show trends in fluid imbalance?

A 
	Temperature (fever)
	Pulse (tachycardia)
	Blood pressure (falling)
	Respiratory rate 
	Oxygen saturation
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15
Q

What factors in physical examination would indicate fluid imbalance?

A

• Feel hands (temperature, cold= vasoconstriction), capillary refill time (normal <2 secs)
• Peripheral cyanosis NB harder to see on black and brown skins
• Skin turgor on skin on back of hands and over sternum (loss of elastic tissue in older patients)
• Pulse: radial and brachial–rate and volume
• Repeat BP
 Postural hypotension often useful indicator of hypovolaemia
• JVP-normal is 2-3 cm above sternal angle (vertical height)
• Check mucous membranes
• Heart sounds-third heart sound may indicate fluid overload (3rd sound)
• Chest examination-pleural effusions, pulmonary oedema
• Ascites (abdominal distention, fluid thrill, shifting dullness)
• Oedema-sacral and ankle
-Sunken eyes

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16
Q

What in the fluid chart needs to be checked?

A

 Input and output
 Daily fluid balance
 Daily weight (reduction= loss)

17
Q

What drugs affect fluid balance?

A

 Diuretics
 Anti-hypertensives
 Opioids (reduces blood pressure)
 Drugs affecting kidney function e.g., Non-steroidal anti-inflammatory drugs

18
Q

What further investigations would be required to assess fluid balance?

A
  • Urea and electrolytes: Elevation in urea and creatinine, estimated glomerular filtration rate
  • Full blood count: Blood loss or haemoconcentration
  • Albumin: Hypoalbuminaemic states e.g., nephrotic syndrome and liver disease
  • Chest X-ray (fluid overload)
  • Infection screen (sepsis)
19
Q

Describe a fluid balance assessment examination

A
  • Check respiratory rate and effort (accessory muscles)
  • Check for oxygen presence, obs chart, fluid balance chart and weight chart
  • Hands: assess for peripheral cyanosis and pallor (poor circulation), temperature, skin turgor, capillary refill time, pulse, blood pressure (erect and supine)
  • JVP check
  • Face: eyes for periorbital oedema, mouth for central cyanosis, drawing mucous membranes
  • Auscultate heart for cardiac failure (gallop 3rd sound)
  • Check lungs for evidence of fluid- percuss to both base (stony dullness for pleural effusion), auscultate for dine inspiratory crepitations (pulmonary oedema), sacral oedema
  • Peripheral oedema in ankles
  • Ascites with shifting dullness, fluid thrill
20
Q

What is the daily salt, glucose, and water requirement?

A

• Fluid requirement= 25-30mL/kg per day
• Kidneys can excrete/retain sodium
• Requirements are Sodium 1 mmol/kg/24 hours, Potassium 1 mmol/kg/24 hour (95% intracellular)
-50-100g/day glucose to limit starvation ketosis

21
Q

When should you prescribe fluids?

A
  • Patient is fluid deplete/hypovolaemic (resuscitation fluids)
  • Patient is unable to take adequate amounts of fluid orally (maintenance fluids)
  • Maintenance fluids also require sodium, potassium (& glucose for calories)
22
Q

What factors of a patient history may indicate fluid imbalance?

A
  • Fluid loss
  • Light headedness
  • Inadequate fluid intake
  • Thirst
  • Fluid accumulation (abdominal/ ankle swelling)
23
Q

What are the symptoms of hypovolaemia?

A
  • Thirst, dizziness
  • Tachycardia
  • Low BP, postural drop
  • Prolonged CRT (capillary refill time)
  • Reduced skin turgor
  • Dry mucous membranes
  • JVP not visible
  • Oliguria
  • Weight loss
  • Elevated urea and creatinine
24
Q

What are the symptoms of hypervolaemia?

A
  • Ankle swelling
  • Breathlessness
  • Abdominal swelling
  • Hypertension
  • Raised JVP
  • Inspiratory crepitations (pulmonary oedema)
  • Pleural effusion
  • Ascites
  • Weight gain
25
Q

What are the types of IV fluids?

A 
•	Crystalloids +/- potassium
	Plasmalyte
	0.9% Sodium chloride
	5% glucose
	0.18% sodium chloride/ 4% glucose
•	Blood and blood products
•	Colloids
26
Q

How are crystalloids used?

A
  • Resuscitation fluids= 0.9% sodium chloride OR Plasmalyte

* Maintenance fluids= 0.18% sodium chloride/4% glucose OR 5% glucose OR 0.9% sodium chloride (will need added potassium)

27
Q

What is the sequence for resuscitation fluid?

A
  • Hypovolaemic= 500mL plasmalyte/ 0.9% sodium chloride bolus over 15 mins
  • Assess response: BP rises, pulse falls, CRT shortens, urine output
  • 2000mL IV fluids if inadequate (up to)
28
Q

What needs to be considered for maintenance fluids?

A

• Can the patient manage oral or enteral fluids for some or all of their requirements?
 Patient fasting pre-operation
 Failed swallow assessment (neurological)
 Unable to meet normal intake (profound diuresis)
• Are there ongoing additional losses?
 Temperature
 Diarrhoea, vomiting
 Diuresis

29
Q

What is the maintenance fluid regimen?

A

• A simple place to start
 1000ml 0.18% NaCl/4% glucose with 40mmol/L K+ alternating with
 1000ml 0.18% NaCl/4% glucose with 20mmol/L K+
 Run at 1.25 mL/kg/hour and not more than 100 mL/hour
• Check urea and electrolytes, creatinine at least daily if giving IV fluids

30
Q

What are the caveats to maintenance fluids?

A

• 0.18% sodium chloride/4% glucose is hypotonic once glucose metabolized
 Risk of hyponatraemia especially in the elderly
 Do not use as sole replacement therapy if sodium <132 mmol/L (use 0.9% sodium chloride instead)
• Potassium replacement
 Normal serum potassium does not mean there is not potassium deficiency (intracellular)
 Do not add potassium if serum potassium >5.0 mmol/L (recheck)

Renal and Urology (43 decks)

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