Fluid therapy in urinary tract disease Flashcards
Discuss Fluid therapy for urinary disease?
- Despite the many types of kidney disease the underlying principles of fluid and electrolyte management are the same
- Appropriate, well planned fluid therapy is critical to treating most of the patients with urinary tract disease (and so many other conditions…)
Fluid therapy for urinary disease – a recap?
Normal fluid losses = insensible + sensible
What are insensible and sensible losses?
Sensible losses: main one is urine but others include V++, D++, body cavity drainage etc, (burns)
Insensible losses: are those that are not easily measured (resp, panting, sweating etc)
- In the normal healthy animal these are replaced by drinking water and the fluid in food
- In sick animals the fluid therapy needs to be tailored for the individual patient to maintain fluid balance
With renal dz, urine volume is often abnormal (high or low) and so?
Fluid therapy needs to be tailored to each patient.
What is important in assessing fluid deficits?
- A well taken history is very valuable for assessing the extent/duration of the disease e.g number of days its been missing fluid
- A full clinical examination must be performed (and regularly repeated)
- Clinical signs may give an approximation to the degree of fluid deficit
What are the clinical signs associated with differente % of fluid deficits?
How does overhydration appear?
- wet mucous membranes
- increased skin elasticity
- shivering
- nausea
- V++
- restlessness
- serous nasal disch
- chemosis
- tachypnoea
- cough
- dyspnoea
- pulm crackles
- pul oedema
- pleural effusion
- ascites
- D++
- SC oedema etc (hocks intermandibular space)
Patient Assessment?
Assess Perfusion status and Hydration status
Understand what each parameter is an indication of
- Pulse quality. Feel in femoral and dorsal metatarsal.
- CRT
- Heart rate Can be influenced by many other things
- demeanour
- Skin tent gets worse as animals age as they loose collagen
- Blood pressure useful to have serial measurements but cuff itself will elevate BP
- Mucous membranes
- Eye position is the 1/3 eyelid coming over
In monitoring fluid therapy for urinary disease what must you do?
- In addition in small animals, compare dorsal and femoral pulses.
- Also assess capillary refill time
- Weigh the animal twice daily
- In some hospitalised patients it is useful to place a central venous catheter and measure CVP (dogs and cats)
- Assess blood pressure (trends)
- Note fluids offered to patient (e.g 200mls then check later what is gone)
Discuss CVP measurement?
- CVP can give info about intravascular filling, a volume depleted animal will have a CVP less than 0cm H20
- A CVP > 10 cm H20 is consistent with volume overload or congestive heart failure
- Pleural effusion falsely elevates CVP.
Discuss bodyweight measurements and fluid therapy?
•An accurate bodyweight is very valuable. A sick animal may lose up to 0.5-1% of its bodyweight per day because of anorexia, and change in excess of this are caused by changes in fluid status.
Discuss blood pressure monitoring?
- Blood pressure going up may indicate a gain of fluid and vice versa. But high % patients have hypertension, the trend is valuable rather than exact amount.
- 80% dogs with severe acute uraemia have hypertension
- 20-30% cats with CKD have hypertension
Knowing the following parameters will also assist in devising and monitoring the response to a fluid therapy plan?
–Plasma electrolytes
–Packed cell volume (PCV) and total proteins (TPP)
–Lactate values (good value to follow gives us an idea of how effective treatment is. Are we improving perfusion of the organs)
–Acid base status
–(e.g. Equine colic patient on fluids would benefit from serial PCV/TP, Lactate)
–What about Colloid Osmotic Pressure? Device that measures influence of plasma proteins within the blood
Look at this table?
Having assessed the extent of the fluid deficit, the next step is to consider the route for fluid administration. What are these routes?
–Oral
–Rectal
–Subcutaneous (small furries)
–Intraosseous
–Intraperitoneal
–Intravenous
Fluid therapy for urinary disease. What type of fluid is appropriate?
A balanced polyionic solution for initial resuscitation is usual e.g. Hartmann’s (also known as Lactated Ringers Solution –LRS)
What is in Hartmann’s ?
Vetivex® 9 (Ringer’s Solution for Infusion)
Contains: Active substances:
Sodium chloride 0.860% w/v
Potassium chloride 0.030% w/v
Calcium chloride dihydrate 0.033% w/v
Approximate ionic content in millimoles per litre:
Sodium 147 mmol/l
Potassium 4 mmol/l
Calcium 2.25 mmol/l
Chloride 155.5 mmol/l
What is in Vetivex® 1 (Sodium Chloride 0.9 % w/v Intravenous Infusion BP (Vet))?
NaCl
What is in Vetivex® 3 (Sodium Chloride 0.9 % w/v and Glucose 5 % w/v Intravenous Infusion BP (Vet))?
Contains: Active substances:
Sodium chloride 0.9% w/v
Glucose monohydrate 5.5% w/v
(equivalent to anhydrous glucose 5.0% w/v)
Approximate ionic content in millimoles per litre:
Sodium 150 mmol/L
Chloride 150 mmol/L
Each one litre provides approximately 200 kcal.
List isotonic crystalloids:
Isotonic-Lactated Ringer’s solution (LRS) aka Hartmann’s – most common fluid therapy used
- It has a very close constitution to plasma (very alike) with respect to sodium and chloride.
- Na + 130 mEq/l , Cl – 109mEq/l
- Buffered, contains lactate as a bicarbonate precursor
- Inadequate potassium for long term: meaning if an animal is hyperkalaemic- this will not push it over the edge
- Good for shock, diuresis, during anesthesia & can use for maintenance (can add other things to it)
- Low levels of calcium: again if hypercalcaemic, will not push over the edge
- Similar tonicity to plasma
- Of 1 litre administered, 250 ml remains in vascular space
- If in doubt choose Hartmann’s!
Other examples of licensed crystalloids:
NaCl solution- like Hartmann’s but without the electrolytes and lactate
Ringers solution- like Hartmann’s but no lactate
5% glucose- small amounts of glucose
What are colloids?
They are much bigger molecules within the fluid and have the action to expand plasma volume quicker and usually last longer than crystalloids as well.
They support colloid osmotic pressure and are used to support the circulating blood volume when needed e.g. severe hypovolaemia, SIRS (systemic inflammatory response syndrome), haemorrhage, hypoproteinaemia
- Colloids are isotonic but exert a colloid osmotic pressure and may be associated with problems- can be linked with anaphylaxis
- More rapid initial re-expansion of volume
- Support circulation longer than crystalloids
- Types - artificial -oxypolygelatins, dextrans rarely used by V/S in UK, starches, HBOCs, also natural colloids e.g. albumin, plasma etc
What may be ok for patients with hyperkalaemia?
0.9% NaCl
After rehydration consider fluid with
less sodium than LRS or 0.9% NaCl (DIY fluids)
Colloids (gelatins & starches used in UK) are useful if patient is suffering from?
hypoalbuminaemia (20-50ml/kg/day depending on the colloid)
What volume of fluid should I give and at what rate?
For mild to moderate hypovolaemia
- Fluid deficit x BW = fluid deficit in litres
Hypovolaemic shock how do these patients look?
Shock patients have dull mentation, hypotension (ABP (systolic) < 80mmHg), cold extremities, poor perfusion, grey or pale mucous membranes and a slow CRT, hypothermia and tachycardia (bradycardia for cats).
Hypovolaemic shock rates?
–60-90ml/kg dog, and 45-60ml/kg cat
–Give ¼ of this over 5-15 minutes, then repeat if no improvement
–CVP can be valuable here
(CVP goes up 2-4cmH20 in euvolaemia and >4 in hypervolaemia but no change in hypovolaemia, if given 10-15ml/kg bolus of crystalloid or 3-5ml colloid)
Fluid therapy for urinary disease. Rate of replacement depends on the clinical case in acute kidney injury what is indicated?
Rapid replacement is indicated (2-4 hours) to prevent ongoing damage to that kidney to prevent those cells dieing
–Allows assessment of oliguria (path vs volume depletion)
–Prevents further damage and restores renal perfusion
Fluid therapy for urinary disease. Rate of replacement depends on the clinical case in chronic kidney injury what is indicated?
- In more chronic cases a more gradual (12-24 hours) rate is advised
- NB Slower rates for animals with cardiac insufficiency. Heart will not cope with increased volume increased quickly.
What is maintenance rate?
- There are several formulae for calculating maintenance rate
- Most of these formulae assume a normal fluid balance though!
- 2-4ml/kg/hr, or 66ml/kg/d or [30xBW]+70 are some of the commonest formulae (see pic for others)
- Anyway, they are a starting point!
Look at these cute little notes from kate?
Maintenance rate is the fluid rate based on average fluid losses from insensible and sensible losses
Administering a rate that exceeds maintenance rate to help with the excretion of the uraemic toxins is often given in animals that can increase urine production in response to a fluid challenge
Twice maintenance rate is equal to maintenance plus a 6% push for diuresis.
- If urine output can be quantified then more accurate (‘ins and outs’) can be documented and the plan can be more precise
- Often in practice accurate volume of urine is not measured how can you do it?
Indwelling urinary catheter and measure volume passed
Look at this fluid therapy for urinary disease (ins and outs) example case?
- A 3.5kg cat
- Insensible losses = 22ml/kg/d = 77ml/d
- Urine output e.g. 80 ml in 24 hours (indwelling urinary catheter)
- Ongoing losses = 6 vomits per day (4ml each) = 24ml vomit/day
- Add these all together 77+ 80 + 24 = 181
- Divide by e.g 4 to get 6 hourly requirement = 45ml in 6 hours or if using a fluid pump 8ml/hr
- Accurate, but still need to monitor patient and respond
Look at this case example which does not have the out measurements?
- 11 year old MN DSH (Arnie)
- 4.1kg
- History of anorexia, polydipsia, polyuria for 5 days
- Laboratory evaluation
–↑ BUN, ↑ creatinine,
↑ phosphorous
–Urine SG 1.012
Clinical examination
–Pulse rate 220
–Resp rate 60
–T 38.2° C (100.8F)
–Mucous membranes tacky
–Approx 5% fluid deficit
Fluid therapy plan- need to calculate
–Maintenance fluids for 24 hours
–Deficit volume based on 5% dehydrated
–Total volume of fluids to be administered
Type of fluids suitable for chronic renal failure?
–0.9% NaCl initially, then reassess over time (hartmans wont kill him but some stuff in it that’s not suitable for renal patients)
Fluid therapy plan
–Maintenance fluids for 24 hours (choose your formula!)
–[(30 x 4.1) + 70] = 193 ml/day
–Dehydration deficit (in % x BW (Kg)
–(0.05 x 4.1) = 0.205L (205ml)
Total fluid requirement for dehydration plus daily maintenance for the first 24 hours:
193 ml + 205 ml = 398 ml
Fluid therapy plan rate
–In this case the deficit should be corrected more rapidly (e.g. 6-8 hours) to prevent further renal damage
–First 8 Hours
–193/3 = 62 mls for maintenance
–Plus the deficit 205 ml
- Total volume = 62 + 205 = 267 ml or 33 ml/hour for first 8 hours …. Or ….
- In practice what you might see is fluid just being give 2-3 times the maintenance rate (i.e.120-180ml/kg/24 hrs)
- MONITOR !!!
- This gives kidneys chunk of help to start with and then monitoring over time with maintenance rate.
Oliguria – what to do?
- ‘Rehydrate’ the patient
- Then try to determine if the oliguria is pathological or physiological
- If the patient is <5% dehydrated no clinical signs will be evident so give normal looking patients a volume 3-5% of their bodyweight – ‘fluid push’ – if no urine –> its pathological
- Rule out anuria being caused by obstruction or leakage before assuming it is due to renal damage
- Pic: cat with retroflexed bladder.
Define normal urine output, anuria and oliguria?
- Normal urine output 1-2ml/hg/hr
- Anuria – no urine
- Oliguria < 1-2ml/kg hr
- All are relative to the fluids the animal is on!
Fluid therapy for urinary disease – NTK. Referral level stuff
If oliguria or anuria persists despite correcting pre-renal factors some clinicians will go on to use diuretics. List them?
–Osmotic diuretic – mannitol or hypertonic dextrose
–Loop diuretics e.g. frusemide
–Dopamine has been advocated in the past, but now only used for as a pressor
–Dopamine agonists? e.g. fenoldopam
–Calcium channel antagonists
–Dialysis …
Poor prognosis if having to do the above
Discuss monitoring fluid therapy:
- This is ongoing and MUST be repeated throughout the day and the plan changed accordingly
- Physical examination and weighing must be performed at least 2x daily
- Record all details on the kennel sheet or ICU sheet to detect trends
Whats the daily weight loss for an anorexic patient?
•Daily weight loss for an anorexic animal 0.5%-1% of BW per day,
What should you monitor for fluid therapy for urinary disease?
- Blood sampling
- PCV
- Plasma proteins
- Electrolytes
- Urea
- Creatinine
- Blood gas values
Fluid therapy for urinary disease when to stop fluids? End points??
- Weaning from iv fluids on to oral is important step and should take a few days
- Taper fluids as azotaemia resolves, e.g. reducing the fluids by 25% per day
- Urine production should decrease in a similar manner
- If urine production does not decrease then the kidneys cannot regulate so wean more slowly
Discuss Outpatient fluid therapy?
- This can be offered to some owners
- The patient can be injected SC daily or eod, or come to the practice for this
- Devices can be implanted to prevent having to inject the animal
- Cats seem to respond better than dogs to SC fluids?
- LRS or 0.9%NaCl (100-150ml/d or eod)
- Don’t use dextrose
Discuss nutrition for urinary disease?
- Nutrition of the patient must be addressed
- Renal failure is catabolic in nature
- Renal diets are available for CKD, but there isn’t really the equivalent for ARF
- Anorexia is common in hospitalised patients and feeding tube placement is advisable in some cases
- PPN or TPN
- If animal has nutrition will improve animal and it may feel well enough to start eating and drinking itself
Discuss Na+ Electrolyte abnormalities in renal disease?
–[Na+] can be normal decreased or increased depending on magnitude of disease
–Serum [Na+] must be regularly measured
–Fluid types may need to be changed
–Changes in [Na+] must be made gradually
–Acidosis is common in renal failure
Why is acidosis common in renal failure:
The daily load of H+ is excreted with the NH3 as NH4+ or with phosphate as H2PO4. With renal failure the kidneys are less able to excrete H+ and cannot absorb adequate amounts of HCO3-. Lactic acidosis from dehydration and poor tissue perfusion can also contribute to acidosis
Discuss K+ Electrolyte abnormalities in renal disease?
–[K+] can be elevated or decreased
–Hypokalaemia is more likely in CKD, & > likely in cats
–Alkalosis makes hypokalaemia worse
–Loop diuretics, anorexia, & vomiting can exacerbate the situation
–Consider using a potassium sparing diuretic so you don’t create a problem yourself
–What are the clinical signs?
–Fluids may need to be supplemented, can then go onto oral supplements (potassium gluconate)
Discuss how to K+ supplement?
–K+ supplementation
–Do not exceed 0.5mEq/kg/hr
Discuss Hyperkalaemia?
–Hyperkalaemia is more likely in ARF
–Mild elevations can occur in patients having ACE inhibitors
–Potentially life threatening
–Treatment involves calcium gluconate & regular insulin & dextrose (make sure you understand why these are given)
–Bicarbonate (metabolic acidosis is common in renal failure)
–Avoid drugs which can exacerbate [K+]
–Peritoneal dialysis..
Hyperkalemia is a potentially life-threatening electrolyte disorder. Why?
•The increase in extracellular potassium changes the electrical potential of excitable cells. The myocardium is relatively resistant compared to the conducting system of the heart. Typical electrocardiographic changes include bradycardia, tall spiked T waves, shortened QT interval, wide QRS complex, and small, wide, or absent P waves. Severe hyperkalemia can lead to a sinoventricular rhythm, ventricular fibrillation, or ventricular standstill. Muscle weakness may be present in patients with serum potassium concentrations more than 8 mEq/L . Characteristic electrocardiographic changes may require emergency therapy before serum potassium concentration results are available from the laboratory. Pseudohyperkalemia may occur ex vivo if red cell potassium content is high, as may occur in Akita dogs.
How does Calcium gluconate treat hyperkalaemia?
Calcium gluconate 10% 0.5-1ml/kg iv slowly to effect to restore cardiac membrane excitability
Discuss electrolyte abnormalities in renal disease with regards to calcium, phosphorus and magnesium?
Calcium
–Measure ionised calcium
–Can be elevated (needing fluids (0.9%NaCl))
–Can be low and may need Ca gluconate iv slowly (ECG)
Phosphorus
–Hyperphosphataemia can be common
–Fluid therapy and phosphate restriction/binding can be used
Magnesium
–May need to supplement
Why are dogs/cats with ARF dehydrated?
Because of GI losses (vomiting) and inability to concentrate their urine
Why do we aim to replace the deficit in ARF patients quicker than we do in other patients (e.g. 4-8) hours rather than 12-24 hours)?
This rapidly will increase renal perfusion and abate any on going renal ischaemia
What would you monitor and why during the rehydration phase?
Good close monitoring, especially for signs of overhydration. Weigh animal, PCV, TP, (CVP going up 5-7 cms probably means overhydration, but need trends, serial readings), physical signs too need to be monitored e.g. crackles, wheezes, restlessness, chemosis increased HR, but all those are real overt signs of pul oedema, and may not be demonstrated…measure urine output too
