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Fluid Prescribing and electrolyte abnormalities Flashcards

1
Q

What it the average total body water of humans?

A

Males = 60%
Females = 50%
Infant = 75%

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2
Q

How is total body water divided between intracellular and extracellular?

A

2/3 - intracellular
1/3 - extracellular

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3
Q

How is water distributed in the extracellular fluid?

A

Interstitial fluid - 3/4
Plasma - 1/4

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4
Q

What is meant by obilagated and free water in the body?

A

Obligated - follows electrolytes gradients typically Na+
Free water - created by loop of Henle left in ascending limb LOH, contains no electrolytes, used to concentrate urine, influenced by ADH.

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5
Q

What is a transcellular fluid?

A

Fluid in epithelial lined spaced e.g fluids of the gut, synovial fluid, cerebrospinal fluid,

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6
Q

Give an overview of the intra-cellular fluid compartment.

A

Stable compartment
Do not adjust to rapid changes
Maintains osmolarity for chemical reactions

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7
Q

What is meant by third spacing in fluid regulation?

A

When fluid moves from the intra-vascular compartment (where it contributes to cardiac output) to a compartment where it does not (ascities, burn sites and pleural effusion)
The fluid is essentially lost -> hypovolemic/hypotensive.

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8
Q

What are the main fluid balance abnormalities?

A

Fluid overload = oedema
Decrease in effective fluid = dehydration

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9
Q

What are the different factors that control the direction of flow of interstitial fluid?

A

Hydrostatic pressure
Oncotic pressure
Endothelial integrity
Lymphatic systems.

(Relates to Starling law)

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10
Q

What are the key forces at play in Starling forces?

A

Capillary and interstitium hydrostatic pressure
Capillary and interstitium oncotic pressures.

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11
Q

What makes up microcirculation in the body?

A

Capillaries (connection between venules and metaarterioles)
And lymphatic vessels.

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12
Q

What are the common modes of transport at microcirculations?

A

Simple diffusion
Vesicular transport
Osmosis.

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13
Q

What are the common causes of oedema?

A

Heart Failure
Renal Failure
Liver disease

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14
Q

How does heart failure lead to oedema?

A

Decreased cardiac efficienct and capacity of left side of heart creates back pressure in pulmonary veins/systemic veins -> increasing hydrostatic pressure.

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15
Q

How does renal failure lead to oedema?

A

Failure to remove fluids and osmotic componenets from the body results in increased osmotic pull into tissues and increased hydrostatic push out of capillaries.

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16
Q

How does liver disease lead to oedema?

A

Failure to produce osmotically active proteins (albumin) decreases the osmotic pull into the capillaries.

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17
Q

What is the average required water intake of an adult?

A

1600 to 2500ml of water per day

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18
Q

What are the different primary sources of fluid loss?

A

Insensible losses
urine, stool, respiration and sweat.

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19
Q

What are the common pathological causes of fluid loss?

A

Diarrhoea
Vomiting
infection
Polyuria
Burns

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20
Q

What is the common presentation of dehydration?

A

Decreased urine output
Dizziness
Fatigue
Tachycardia
Increased skin turgidity
Tachycardia
Low BP
Dry mucosal membranes.

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21
Q

How do we calculate fluid deficit?

A

Use following calculation for both pre-dehydration and post-dehydration weight
0.6*weight (kg) * [1-(140/sodium)]

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22
Q

When should IV fluids be prescribed for dehydration?

A

When needs cannot be met by oral intake or enteral routes
e.g NBM, vomiting, severe diarrhoea, acute blood loss

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23
Q

What should be included ina fluid prescription?

A

Type, volume and rate of fluid

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24
Q

What is included in an IV fluid management plan?

A

Regular monitoring
Re-assessment of clinical volumes status
U+Es
Fluid input/output balancing
Fasting weight measurements.

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25
What is meant by a crystalloid fluids?
Small molecules in water - e.g NaCl, Hartmanss, dextrose Low cost Small molecules move around easily within the body Superior in initial fluid resus
26
What is meant by colloid fluids?
Solution of larger organic molecules e.g albumin, gelofusin More expensive Bigger molecules remain in blood for longer Increased risk of anaphylaxis.
27
IV fluid composition chart for reference
28
What is important to know about the tonicity of different IV fluids that can be given?
Isotonic = 0.9% sodium chloride and Hartmans solution Hypotonic = 0.18% NaCl and 4% glucose, 5% dextrose.
29
What is important to know about the Na+ content of IV fluids?
0.9% chloride is slightly higher Hartmans solution - slightly lower 0.18% NaCl and 4% glucose and 5% dextrose - significantly lower.
30
How can potassium be added into IV fluids?
Pre-mixed 20mmmol or 40mmol additives in bags that do not already contains potassium e.g 0.9% NaCl, Hartmans, dextrose.
31
What should be monitored when patients are on IV fluids in relation to their sodium levels?
BP Urine output U&Es If decrease in either should increase fluid input.
32
What is a patients history can indicate fluid imbalance?
Age Reason for admission Past medical history Medications Input/output inc fluid Symptoms of overload Fluid restrictions.
33
What on general inspection can indicate a fluid imbalance in a patient?
Cynosis SOB Pallor Mallor flush Odema Vital signs Fluid balance chart Daily weights Access to fluids.
34
What in the bedside assessment of the body can indicate fluid imbalance?
Hands - colour, leukonychia, temp, CRT, skin turgor Pulses/BP JVP Face - sunken eyes, pallor, mucous membranes Chest - RR, central CRT, Heart sounds, Lung fields Oedema - sacral or peripheral Abdomen - distention, striate, shifting dullness.
35
What are the 5 Rs of IV fluids?
Resuscitation Routine maintenance Replacement Redistribution Re-assessment
36
How does resuscitation often occur in IV fluids process?
Hypovoaemic 1. initial 250-500ml bolus IV crystalloid STAT 2. Re-assess ABCDE 3. If hypo persisted repeat bolus and re-asses 4. Can repeat until 2000ml fluid has been given 5. Contact senior If complex risk of overload give smaller boluses and get help earlier.
37
What is meant by routine maintenance of IV fluids?
Given when haemodynamically stable but unable to meet daily needs Daytime house Water = 25-30ml/kg/day K+/Na+/Cl- = 1mmol/kg/day Glucose - 50-100g/day Norm 1 salty and 2 sweet bags of fluid.
38
What is meant by replacement and redistribution in IV fluid management?
Some patients require different management Existing fluid or electrolyte abnormalities Ongoing abnormal fluid or electrolyte losses Re-distribution and other complex issues - oedema, sepsis, liver impairment etc
39
How is ADH produced?
Baroreceptors - stretch with high BV inhibit ADH release Osmorecepotrs - shrink during dehydration, trigger ADH release ADH is produced by the hypothalamus and secreted by the posterior pituitary gland.
40
What is the main action of ADH?
Acts of collecting ducts and DCT of the nephron to stimulate water re-absorption from the urine into the blood. Also acts on V1 receptors to cause vasoconstriction of vascular smooth muscle Increase ACTH release from anterior pituitary Overall effect is to reduce diuresis (dec urine output and increase fluid retention)
41
What specifically does ADH do at the nephron?
Acts on vasopressin (V2) receptors on the basal epithelial DCT and CD - resulting in signalling cascade that insertrs aquaporin 3 channels into the apical membrane This allows water to pass from the filtrate into the cell, then into the interstitial fluid through aquaporin 3 and 4 channels.
42
What factors affect ADH production in the hypothalamus?
Stimulated by: inc plasma osmolarity, inc angiotensin 2, dec BP, dec BV Inhibited by ethanol.
43
Define hyponatremia
Less than <135mmol?L
44
What are the different severities of hyponatremia?
Mild 130-135 mmol/L Moderate 125-129mmol/L Severe <125mmol/L
45
What is the difference between acute and chronic hyponatreaemia?
48 hours onset
46
What is the basic physiology underpinning sodium concentration in the body?
Determined by total body water Major determinant of effective osmolarity in the ECF - regulates pressure gradient ADH controls osmoregulation
47
What is osmolarity?
The concentration of a solute dissolved in a solution
48
What is the human body responses at different osmolarities?
Norm - 275-295mOsm/L ADH released at 280mOsm/L Thrist at 290mOsm/L
49
What are some causes of hypovolemia hyponatremia?
GI losses Skin losses Renal losses Other
50
What can cause euvolaemia hyponatremia?
SIADH Abnormal ADH release (hypothyroidism and Addisons) Psychogenic polydipsia
51
What are some causes of hypervolaemia hyponatremia?
Failure - heart, liver, renal Nephrotic syndrome
52
What causes pseudo-hyponatremia?
Artefact when serum protein or serum lipids rise.
53
What are some common symptoms of hyponatremia?
Asymptomatic or vague Headache, confusion, nausea, elthargy Severe - seizures and loss of consciousness
54
What drugs can cause hyponatremia?
ACEi and ARBs Proton pump inhibitors Anti-epiletpci drugs Amiodarone Thiazide and loop diuretics Temazepam Sulphonylureas SSRIs Ecstasy.
55
What investigations are often done for hyponatremia?
Bloods: U&Es, glucose, lipids, TFT, LFTs, 9am cortisol, plasma osmolarity Urine: osmolarity and sodium
56
What are some complications of hyponatremia?
Severe - seizures, loss of consciousness and coma Cerebral oedema - raised ICP, large fluid shift due to changes in osmolarity -> concentration, cognitive deficits, gait distrubances and falls. Osmotic demyelination syndrome - central pontine demyelination, rapid correction of hypoNa+, rapid shift of water in pons
57
How fast should sodium levels rise?
Not more than 10mmol/L in 24hrs.
58
Define hypernatremia Acute v chronc
Plasma sodium conc >145mmol/L Acute <24hrs Chronic >48 hrs
59
What are the common causes of hypernatremia?
1. Unreplaced water loss 2. Sodium overload - hypertonic saline, salt ingestion 3. Water loss into cells - extreme excersie or seizures
60
How to calculate plasma Na?
Total body Na+K ------------------------- TBW
61
What are the symptoms of hypernateraemia?
Thirst and dehydration Lethargy Fever Nausea, vomiting and diarrhoea Confusion and abnormal speech
62
What are the clinical signs of hypernatremia?
Dry mucous membranes Hypotension (postural) tachycardia Altered mental status Oliguria (dehydrated) or polyuria (diabetes inspidus)
63
What blood tests should be done for hypernatremia?
U&Es FBC Glucose LFTs Bone profile Plasma osmolarity CRP (infection) Creatine kinase

Med 2 (26 decks)

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