SCRIPT: renal dysfunction Flashcards
Analgesia and renal disease.
a) Paracetamol
b) Oral/systemic NSAIDs
c) Topical NSAIDs
d) Weak opioids (eg. codeine, tramadol)
e) Strong opioids (eg. morphine, oxycodone, fentanyl)
f) Corticosteroids
g) Neuropathic drugs (eg. gabapentin, pregabalin, amitryptilline and duloxetine)
a) Safe
b) Avoid
c) Use with caution (there may be some systemic absorption)
d) - Use with caution
- May need to reduce dose
e) - Use with caution (may need to reduce dose)
- Generally fentanyl is safer than oxycodone, which is safer than morphine
f) - Use with caution, may need to reduce dose
g) - Gabapentin/pregabalin - reduce dose according to GFR
- Amitryptilline - normal dose
- Duloxetine - avoid if GFR < 30
AKI classification.
a) Stage 1 (3 possible criteria)
b) Stage 2 (2 criteria - think ‘2 = double’)
c) Stage 3
a) AKI stage 1:
Urine output < 0.5 ml/kg/hr for 6 hours (< 35 ml/hr in 70kg person)
OR
Creatinine rise > 26.4 micromol/L over last 48 hours
OR
Creatinine rise by 50% from baseline over last 7 days
b) AKI stage 2:
Creatinine rise of ≥ x 2 from baseline over last 7 days
OR
Urine output < 0.5 ml/kg/hr for 12 hours
c) AKI stage 3:
Creatinine rise of ≥ x 3 from baseline within 7 days
OR
Creatinine rise to ≥ 354 micromol/litre with either:
- Acute rise in creatinine of ≥ 26 micromol/litre within 48 hours or
- ≥ 50% rise from baseline within 7 days
OR
Urine output of < 0.3 ml/kg/hour for 24 hours
OR
Anuria for 12 hours
OR
Any requirement for renal replacement therapy
Principles of good prescribing in renal medicine.
- Good fluid balance: correct hypovolaemia
- Minimise renal hypoperfusion (often caused by drug therapy, eg. ACE inhibitors, NSAIDs)
- Treat precipitating factors (eg. sepsis)
- Avoid the use of (or withdraw) nephrotoxic agents
- Consider drugs that are renally excreted and may need adjustment* (particularly water-soluble drugs)
- Adjustment can involve:
- reducing drug doses (eg. with opiates)
- increasing the interval between doses (eg. with gentamicin)
Principles of preventing AKI.
- Good fluid balance
Potentially nephrotoxic medication.
a) Pre-renal (cause hypovoleamia/ hypotension or renal hypoperfusion)
b) Renal (directly nephrotoxic)
c) Post-renal (causing/worsening obstruction)
a) Hypovolaemia/ hypotension:
- Diuretics
- Antihypertensives
Renal hypoperfusion:
- NSAIDs (constrict afferent arteriole - reduce GFR; prostaglandins help to maintain glomerular pressure)
- ACE inhibitors (dilate efferent arteriole - reduce GFR; angiotensin II helps to maintain glomerular pressure)
- Radiocontrast (renal vasoconstriction)
- Ciclosporin/tacrolimus (renal vasoconstriction)
b) - Aminoglycosides
- Amhotericin
- Certain cytotoxic drugs (eg. cisplatin)
- Lithium (but of vital use in bipolar so generally continued but with vigilant monitoring of levels)
- Cocaine
- Any cause of rhabdomyolysis (eg. statins)
c) - Anticholinergics
- Benzos, opiates, antidepressants, antipsychotics
- Anaesthetics - GA, regional, local
- Calcium channel blockers
- Alpha-agonists (eg. midodrine)
GFR vs. Cockcroft-Gault formula
a) when is GFR not accurate?* (patient factors, disease factors, specific drugs)
b) what is the Cockroft-Gault formula?
c) what does creatinine clearance actually tell us?
*Hence use Cockcroft-Gault formula in these groups
a) Patient factors:
- Children
- Pregnancy
- Elderly patients, i.e. > 75 years (due to sarcopenia)
- Patients at extremes of muscle mass/ body weight (anorexia, cachexia, body-builders, obesity)
- Amputees (or people with missing limbs, as it is standardised to a body surface area 1.73 m2)
Disease factors:
- AKI (or any oliguria)
- Patients with renal impairment (when estimating renal function or calculating drug doses)
- Patients with muscle disorders (due to distorted creatinine levels)
Specific drugs:
- Direct oral anticoagulants (DOACs)
- Medicines with a narrow therapeutic index (gentamicin, lithium, digoxin)
- Nephrotoxic medication (eg. gentamicin, vancomycin)
b) Calculation of creatinine clearance:
Cl(Cr) = F x (140 - age) x weight in kg / serum Cr
(F = 1.03 in women and 1.23 in men)
c) - The volume of plasma that is cleared of creatinine per minute
- Creatinine clearance is a surrogate for GFR (but is slightly higher as there is net secretion of creatinine, which can be blocked by cimetidine)
A 38 year old obese woman has a serum creatinine of 225 and an eGFR of 22 ml/min/1.73m2.
She weighs 122 kg.
a) Calculate her creatinine clearance
b) Then explain why eGFR is not useful in her
a) Cl(Cr) = F x (140 - Age) x weight in kg / serum Cr
… Cl(Cr) = 1.04 x (140 - 38) x 122 / 225
= 57 ml/min
b) eGFR underestimated her renal function as 22 (CKD stage 4), when actually it was 57 (CKD stage 3a)
Fluid management in AKI.
a) Initial
b) Maintenance
c) When to use sodium bicarb 1.26%
d) When to escalate for RRT
a) - Assess fluid status - HR*, BP, urine output, clinical signs (chest, ankles, skin turgor, mucous membranes, thirst, etc.)
- IV access and take bloods (U+Es, etc.)
- ECG if ?hyperkalaemia, CXR if ?pulmonary overload
- If hypovolaemic, fluid resus (250 - 500 ml boluses of 0.9% NaCl** up to 2L before escalation) - always be monitoring
- If hypervolaemic with AKI, involve senior
- Consider cause of AKI - manage if possible (eg. Sepsis 6)
*Can assess for postural tachycardia (>30 after 1 minute on standing) and postural hypotension (< 20/10 after 3 mins on standing)
**Generally NaCl is best in AKI, not potassium-containing fluids like Hartmann’s due to risk of hyperK+
b) - Generally maintenance fluids involving adequate sodium, potassium, glucose, etc. (eg. Dex/saline + KCl)
- Monitor fluid status clinically (examination) and objectively (obs, fluid balance charts)
- Monitor U+Es
- If potassium high, ECG + treat as necessary
- If ?pulmonary overload - CXR
c) - If acidotic (HCO3- < 20), to alkalinise the urine
- Only under guidance from renal specialist (registrar or consultant)
d) AEIOU
- Acidosis
- Electrolytes - refractory hyperK+
- Intoxicants - eg. paracetamol, alcohol, aspirin OD
- Overload - pulmonary
- Uraemic complications (encephelopathy, pericarditis)
Diuretics in CKD.
a) Indications
b) If rapid effect needed - dose and route?
c) Why are IV infusion rates of furosemide limited to no more than 4 mg per minute?
d) Which diuretics are permissible and which are not?
a) - Fluid overload
- Hyperkalaemia
- Hypertension
b) - IV furosemide 250 mg infusion over 1 hour
(i. e. rate not exceeding 4 mg per minute)
c) Quicker infusions have higher risk of deafness (never give bolus dose!)
d) - Furosemide often used
- Thiazides generally not useful when eGFR < 30, except metolazone (but risk of excessive diuresis - use only under specialist supervision)
- Potassium-sparing diuretics* generally avoided
*Note: ACE inhibitors and spironolactone may be useful in CKD for reducing proteinuria (under specialist supervision, due to risk of hyperK+)
Hypertension management in CKD.
a) Best drugs and how to titrate
b) Contraindications to these
c) BP targets
d) Non-drug management
a) ACE + ARBs
- check K+ before starting
- must be started low and titrated slowly
- check K+ after 7 days, and 7 days after each dose increase
- If >20% rise in creatinine permissible/ 25% decrease in GFR, consider other reasons (eg. dehydration), but if likely due to ACE/ARB, stop medication
- If cough on ACE, switch to ARB
- Titrate up to maximum tolerated dose before adding other agents (eg. CCBs, loop diuretics)
b) - Bilateral renal artery stenosis,
- Renal artery stenosis in a patient with a single functioning kidney, or
- Known widespread vascular disease (“vasculopaths”) as renovascular disease is likely to be present compromising blood flow
- Hyperkalaemia
c) - Generally < 140/90
- Diabetes (or ACR >70): < 130/80
d) - Salt restriction
- Healthy lifestyle
Patient with fast AF and heart failure - drug of choice
Digoxin
Hyperkalaemia: management
a) Cardioprotection
b) Serum potassium-lowering medication
c) Rid the body of excess potassium
K+ >6.5 or ECG changes*
- 10% calcium gluconate 10mls over 10 mins
- effect lasts only ~ 1 hour
- repeat as necessary according to ECG changes
- (or calcium chloride)
(note: NEVER give calcium and bicarbonate via same line as it forms chalk)
*Tented T waves, flattened P waves, prolonged PR, wide QRS, sinusoidal QRS (peri-arrest)
b) Insulin + dextrose
- 50 ml of 50% glucose*, plus
- 5-10 units of Actrapid
- over 10 minutes
- monitor glucose and K+
*Omit glucose if BM > 15
Nebulised salbutamol*
- 5 - 10 mg over 15-30 minutes
- Note: it can cause tachycardia
c) - Reduce dietary potassium
- Calcium resonium* - chelates potassium in gut, give with lactulose to reduce risk of faecal impaction
- Stop potassium-raising medication (eg. ACE, ARB, spiro, NSAIDs, Sando-K)
*Seek nephrology advice if you want to use this!
Insulin prescribing in renal failure
- Insulin accumulates in renal failure
- So in general, as renal failure progresses, insulin doses should be reduced
- Also, metformin generally stopped once eGFR < 30
