Fluid Therapy

Question 1

What would your fluid therapy approach be to an anuric cat with acute renal failure? Write a few sentences about your general approach.

Answer 1

· Need to work out why it’s anuric first!! If <5% dehydrated give 3-5% of body weight as a bolus (fluid push) over 5-15minutes then measure urine output. If no urine then pathological rather than physiological

· Anuria causes: obstruction, ruptured ureters

· Use fluid deficit to work out how much to give. Rapid replacement (with LRS) over 2-4hours, then maintenance for later on. This helps prevent further damage and prevents renal perfusion.

Question 2

On presentation and following clinical examination you assess the cat as having an 8% fluid deficit. The cat has a slight hyperkalaemia. Creatinine and BUN are also elevated. The bladder cannot be palpated and cystocentesis is un-productive.

1. How would you administer fluids to this cat? i.e. what route would you use and why?
2. What fluid would you choose and why?
3. Devise a fluid therapy plan for the first 24 hours. The practice has 24 hour nursing and access to all fluids/drugs.
4. What are your goals and end points?
5. Despite appropriate fluid therapy there is still very little urine being produced. What do you do next?

Answer 2

1. IV as need rapid perfusion of kidneys
2. LRS/Hartmans will probably be ok– but note that this contains some K and Ca – so perhaps not ideal in an animal with hyperK+ (but usually ok)
   0.9% NaCl, has no K+ in it, use this only for a short time then LRS
   In hyperK+ patients can give….

o Calcium gluconate (chelates the K+) – cardioprotective , need to also do ECG alongside

o Insulin and glucose (dextrose) – helps move the K+ back into the cells?

o Also can give sodium bicarbonate – must carefully monitor – with large amounts can get cerebrospinal fluid acidosis – neuro signs

3. Perhaps assess why auric first – do fluid push 10ml/kg over 10 mins – so 40ml in 10 minutes – as measure urine output? To see whether anuria is pathological or physiological. May be oliguria (less urine than normal), anuria (none at all). Normal 1-2ml/kg.hour

· Cat 4kg assumed, fluid defecit (% dehydration x body weight) = (0.08 x 4) = 320ml

· Maintenance = (30x4) + 70 = 190ml

· 24 hours = maintenance + defecit = 510ml

· First 4 hours – 85ml/hour (near shock rate) (85 x 4 =340ml)

· Then after this (510-240) = 170 ml for 20hours – 8.5ml/hour

4. Correct fluid defecit, electrolyte correction and acid base disorders – support it via maintenance

· Establish or maintain urine flow

· Treat underlying cause of renal failure

· End point = when BUN, creatinine, urine output, hydration state, blood pressure are normal?

5. If less then 1ml/kg/hour then consider using diurectics

· Osmotic (mannitol), Loop (furosemide), dopamine agonist (fenoldopam), Ca channel antagonists, dialysis if very end stage (peritoneal or haemo)

Question 3

A 16 year old cat with well controlled chronic renal failure requires anaesthesia to investigate a 2 week history of halitosis and anorexia. The cat is fractious and uncooperative on examination. The owners had successfully administered a 10 day course of broad spectrum antibiotics dispensed by you in the last 2 weeks, but the cat has deteriorated.

1. The cat is admitted the evening prior to anaesthesia. What are you going to do prior to the anaesthesia?
2. Describe how you will prepare the patient prior to anaesthesia. You are successful in securing iv access in the cephalic vein. What nursing orders will you give the night nurse for this patient?

Answer 3

1.

· Thorough clinical exam – HR, RR

· Urinalysis (SG, protein and culture) to assess state of kidneys

· Pre anaesthetic blood : Measure creatinine, BUN, electrolytes (K, Na, CL, Hc03, P) - may need correcting or stabilising before, arterial blood pressure. PCV measure

· Dextrose - If anorexic?

· Assess dehydration status – is CKD being managed?

· Palpate bladder

· If hypertensive à amlodipine

· If hypoK+ then correct with oral K+ supplementation, K+ citrate (treats metabolic acidosis and hypoK)

· If hyperP then oral phosphate binding agents

· Ureamia managed by diet changed – low phosphate diet, protein too? Hard if not eating. Maybe peritoneal dialysis?

· Before anaesthesia must have …… correct uraemia (adequate preload will help- IV fluids), ensure K ok, restore and ensure adequate blood volume, correct metabolic acidosis if present (oral sodium bicarbonate).

2.

· Fluids - just maintenance? Assess dehydration level first.

o Maintenance (30x3)+ 70. = 160ml/day

· Monitoring closely – reassess hydration, weight

Question 4

List causes of halitosis (3) and anorexia (3) in cats.

Answer 4

· Anorexia: pain, CKD, neoplasia,

· Halitosis: tooth decay, root abscess, CKD (uraemia)

Question 5

The cat weighs 3kg. You premedicate the cat with a combination of diazepam and methadone intramuscularly. Anaesthesia is induced following pre-oxygenation, with alfaxalone (Alfaxan) given slowly to effect. The cat is intubated and maintained on sevoflurane in oxygen.

· Good oxygenation needed.

· Avoid pre-med and use pethidine (opiod if renal dysfunction severe)

Describe your approach to intra operative fluid therapy and how you would monitor this.

Answer 5

· IV maintenance 2ml/kg.hour or (30xbw) + 70

· Monitor blood pressure and blood gas, peripheral pulses , HR and RR.

· If worried increase fluid rate

Question 6

Extensive dental extractions are required and a fractured premolar is identified. The gum disease is extensive. Comment on the analgesics you have used and duration of action.

Could you use a NSAID?

Answer 6

· Methadone : duration 3-4 hours. Its going to need more analgesia post op to go with

· NSAID?? This cat has well controlled CKD and is not hypovolemic (with correct fluid). Best avoided if possible. If needed then carprofen. Give post op okay once.

o NSAID block renal protective response to hypertension – so could worsen kidney disease . Carprofen weak inhibitory activity so safest to use

· Perhaps buprenorphine – perhaps injection before sending home?

· Fentanyl patch to go home with?

· Tramadol tablet?

Question 7

Following a dental anaesthesia the cat remains anorexic. Comment on the causes and your approach to this problem.

2. When would you discontinue fluid therapy?

Answer 7

· Pain from dental extraction? Ensure adequate pain relief.

· Negative association with food? Try and encourage with wet soft tasty warm food. Hand feed and tempt.

· Appetite stimulant à mirtazapine and cyproheptadine ? Reduce dose with CKD. Maropitant (anti-emetic) – study may also work

2.

· Continue into recovery. LRS good for intra-operative but post op will not be good for sodium balance in cats in CKD (will give excess Na). SO instead use…

· 0.18% NaCl solution + 4% dextrose

· Half strength LRS 0.45% NaCl

· Fluid needs to have some K+ in it 5mmol, more can be added if necessary (spike the bag – make sure to label the bag)

· Remain on fluids for minimum of 6-12 hours post op

Question 8

A 2 day old 50kg foal is hospitalised with renal failure complicated with hypoxic ischaemic encephalopathy following dystocia. The foal is becoming progressively more depressed and exhibiting marked dependent oedema.

1. What is the most likely cause of the oedema?

Answer 8

· Dependant oedema = limb

· PLE protein losing nephropathy

· Malignant oedema – clostridium septicum

· Lawsonia intracellularis causes PLE à oedema

· Overload fluids

· Ischemic causes hypoxia and renal damage , oedema, haemorrhage

· Prolonged ischemia results in disruption of tight junctions in the capillary endothelium and leakage of osmotic agents and fluid into surrounding brain interstitium resulting in vasogenic edema

· Sepsis? SIRS?

· Decreased renal perfusion occurs during asphyxia as a result of redistribution of fetal cardiac output. In infants renal damage has proven to be a sensitive indicator of even mild peripartum asphyxia. Clinical signs of renal ischemic damage include oliguria (,1 ml urine/kg/h), peripheral edema, elevated concentrations of serum creatinine and urine GGT, and electrolyte disturbances such as hypocalcemia, hyponatremia, and hypochloremia due to renal tubular damage.

Question 9

A 2 day old 50kg foal is hospitalised with renal failure complicated with hypoxic ischaemic encephalopathy following dystocia. The foal is becoming progressively more depressed and exhibiting marked dependent oedema.

Consider the following biochemistry results for the foal. Use the ‘The Equine Hospital Manual’ by Corley & Stephen or other equine medicine textbooks in the CSGTRs for normal values.

Na 130mmol/l normal 133-147 à low

Cl 89mmol/l normal 97-110 à low

K 2.5mmol/l normal 2.8-4.7 à low

HCO3 32mmol/l normal 22-29 à high

Total protein 34g/l normal

1. Why is the foal losing chloride and protein?
   The following information is also supplied: the horse has a serum creatinine of 500 µmol/l. Normal 77-175. SO this is massively high!!
2. What magnitude of azotaemia does the foal have?
3. What would be your action plan for this foal? List 3 main aims
4. Suggest a type of fluid(s) to administer and an appropriate rate.

Answer 9

1. Ischemia to kidneys so poor functioning
2. Very high
3. Correct azoemia, stop oedema, oxygenate? Correct electrolyte imbalances.
4. To correct azotemia – LRS