renal Flashcards
what are the main roles of the kidneys?
- Regulate water and electrolyte content in the
body (e.g. Sodium, Potassium) - Retention of substances needed by the body
–Glucose, Protein - Maintain acid/base balance
- Key role in regulating blood pressure
- Excrete waste products (e.g. urea, creatinine),
water soluble toxic substances
and drugs - Endocrine functions
how is urea produced?
Produced when protein or a.a’sare broken down in
the liver. Urea is normally cleared by glomerular
filtration and reabsorbed in the kidney tubules.
what causes an increase in urea?
dehydration
concurrent infection
gastric blood loss
what causes a decrease in urea?
oedema
low protein diet
decrease liver function
pregnancy
chronic nutritional status
what is the reference range for urea?
3.0-6.5mmol/L
how is creatine produced?
Produced continuously in muscle and is a function
of muscle mass
waste product of muscle metabolism
how is creatine predominantly cleared?
Predominantly cleared from the body via glomerular
filtration
why is creatine often used to determine kidney function?
Plasma concentration of creatinine linked to both
muscle mass and the kidneys ability to excrete
creatinine
what factors affect renal function?
gender
age
weight
race
muscle mass
what equation is used to calculate crcl?
cockcroft- gault
F x (140 –age) x weight (Kg)//
Serum Creatinine (μmol/L)
what is the eGFR?
modified diet in renal disease
what ways can you estimate renal function?
- Cockcroft and Gault equation
- Modified Diet in renal disease
- EPI-CKD
- 24 hour urine output
what calculation should you use to check renal clearance if the patient is on a narrow therapeutic index drug?
For narrow therapeutic index drugs, use eGFR –
However correct for patients actual BSA
eGFR x Actual BSA//
1.73
OR If in doubt, and narrow therapeutic index drugs
calculate CrCl via Cockcroft and Gault equation
whats the most important thing when interrpting results?
you need to know the patients baseline
you cannot determine it on one result
what are the different ways in which an AKI presents?
AKI: No previous CKD, patient recovers or
continues with degree of CKD
* Acute on chronic: Unknown CKD presents with
AKI
* Routine appointment finds an increase in
creatinine and refers to nephrology clinic
what is AKI ( acute renal failure- old name)
‘The abrupt transition from functioning
kidneys to kidney function which is unable to
accomplish biochemical homeostasis‘
how is AKI defined?
- Serum creatinine rises by ≥ 26μmol/L within 48
hours or - Serum creatinine rises ≥ 1.5 fold from the reference value, which is known or presumed to have occurred within one week or
- urine output is < 0.5ml/kg/hr for >6 consecutive
hours
what are the criteria for stage 1 AKI?
SCr- increase> 26umol/L within 48 hours or increase> 1.5 to 1.9x reference SCr
and <0.5ml/kg/hr for>6 consecutive hours
what is the criteria for stage 2 AKI?
increase to >2-2.9x reference SCr
or <0.5ml/kg/hr for >12 hours
what is the criteria for AKI stage 3?
increase >3x ref SCR or inc >354 umol/L or commenced on renal replacement therapy of stage
or <0.3ml/kg/hr for >24 hours or anuria for 12 hours
what causes a kidney injury?
pre-renal causes: eg sepsis, decreased BP, GI bleed
intrinsic: rhabdomyolysis, tubular necrosis
post renal: eg retention, prostate cancer
what are the 3 R’s of kidney care?
- Reducing Risk
- Early Recognition
- Right Response
who is at risk of kidney problems?
- Advanced Age
- Sepsis, hypovolaemia and hypotension
- Diabetes mellitus, Heart failure, liver disease
and atherosclerotic PVD - CKD, Hx of AKI, Oliguria
- Surgical procedures
- Medication, Use of contrast media
- Low Albumin
how do you reduce risk of kidney probelms?
- Recognise and assess high risk pts
- Assess fluid status
- Avoid nephrotoxic agents
- Obtain baseline renal function
- Treat infection early
- Maintain effective circulatory volume
- Recognise and treat hypoxia
- Check for acidosis
what are early recognition signs?
fluid balance chart
U AND ES
drug hist
urine dipstick
vital signs
what is a good way to detect?
Monitor serum creatinine regularly in all adults,
children and young people with or at risk of
acute kidney injury.
what are the possible correct responses to kidney damage?
- Assess fluid status
- Avoid nephrotoxic agents
- Treat infection early
- Maintain effective circulatory volume
- Recognise and treat hypoxia
- Check for acidosis
when doing a medicines optimisation for an AKI what would you check?
- Avoid nephrotoxic medicines
- Monitor RF when they are used
- Review nephrotoxic medicines–E.g to prevent AKI in D&V
- Med r/v prior to surgery and radiological rocedures requiring contrast media
- Temp/Permanently withdraw meds that affect
kidney haemodynamics - Review side effect profile of medicines Ensure medicines, and their doses, are appropriate for reduced renal function
- Ensure fluid volume used for drugs is appropriate
- Monitor potassium and review drugs that cause
hyperkalaemia
what drugs should you look out for with AKI?
- Contrast Media
- Ace Inhibitors
- NSAIDs
- Diuretics
- ARBs
why is there sick day guidance for certain medications for your kidneys?
as they may promote kidney damage
be careful with diuretcs as may not be so easy to stop abruptly
what is the sick day advice and what medications are included?
if you are unwell with vom/ diarrhoea/ fever/ sweats
stop taking your medications and restart when you are well 24-48 hours after
ACEI ARBS, NSAIDS,diuretics, metformin
what are the 3 main reasons for providing sick day guidance?
- NSAIDs impair renal autoregulation by inhibiting prostaglandin-mediated vasodilatation of the afferent arteriole and may increase the risk of AKI
- Drugs that lower blood pressure, or cause volume contraction, might increase the risk of AKI by reducing glomerular perfusion.
- Drugs might accumulate as a result of reduced kidney function in AKI, increasing the risks of adverse effects
what are risk factors for kidney problems?
Hypertension
* Diabetes
* Proteinuria / albuminuria
* Others
–Obesity, Smoking, Hyperlipidaemia
–Age, CVD, NSAID use
–AKI
what are some causes of CKD?
- Diabetes
- Hypertension
- Others include:
–Glomerulonephritis
–Polycystic kidney disease
–Analgesic nephropathy
what heps cardiovascular risk in CKD?
–Exercise
–Smoking cessation
–Diabetic control
–Blood pressure control
–Cholesterol/statins
what are some medication complications for patients who have CKD?
- Renal Anaemia
–Folate, B12, Iron, ESA’s - CKD mineral and bone disorder
–Diet, Phosphate binders
–Cinacalcet
–Vitamin D - Metabolic Acidosis
–Sodium Bicarbonate
what advice should you give to patient on renal medication?
At risk of adverse events
* Multiple medicines
* High risk of drug to drug interactions
* Need to know pharmacokinetics of medicines
* Affect RRT has on medication
* Dose modification often needed below
30ml/min
* Information not always readily available
what could the possible effect be on renal impairment with multiple drugs?
- Accumulation of drug
–Adjustments usually needed when >25% of active
drug/metabolite eliminated renally
–Drug elimination affected by ↓GFR (age +/- CKD) - Accumulation of active metabolites
- Altered drug distribution (i.e. protein binding)
- Decrease in renal drug metabolism
–Drugs affected include Digoxin & Insulin
when dosing a drug does the loading or maintenance dose change?
- Loading Dose - Generally unchanged
- Maintenance Dose - Generally if a drug is
normally excreted via the kidneys, its
maintenance dose will need to be adjusted in
patients with renal impairment.
what is the goal of therapy?
- Maintain benefit of drug
- Avoid accumulation and toxicity
- Decrease the dose, keeping the interval
constant - Increase the dose interval, keeping the dose
constant
what effect does HPT have on kidney injury?
elderly- inc riskoof falls
hypoperfusion of kidneys- AKI
what should you do if a patient is on ACEi or ARB?
- When used
- Dosing
- Monitoring
- AKI
- CKD and stage
- STOP ACE study currently on going
what is an acceptable change when starting on ACEi or ARB?
small rise in creatinine
*<20% increase from baseline
creatinine
OR
*<15% fall in GFR
what Gplitins have renal impairment? are adjustments needed?
– Linagliptin –no dose adjustment needed
– Sitagliptin –eGFR 30-50mL/minute - 50 mg OD eGFR
<30mL/minute - 25 mg OD
– Saxaglitpin –2.5mg OD in moderate/severe impairment,
caution in severe impairment
– Vildagliptin –eGFR <50mL/minute –50mg OD
how is insulin renally impaired?
–1/3 of insulin degradation is carried out in the kidney and impaired kidney function is associated with prolonged half life of insulin
–Need to closely monitor blood glucose levels
–May need to reduce doses
–Also note CKD 3-5 leads to impaired gluconeogenesis - therefore prolonged hypoglycaemia
how do you manage pain in CKD?
- Step 1: Mild Pain
- Paracetamol 0.5 –1g QDS
- Step 2: Moderate PainRegular Paracetamol + weak opioid +/- adjuvant
- Acute pain: Codeine or Tramadol with caution or [low dose Oxycodone 2.5 –5mg]
- Chronic Pain: Modified release preparation + breakthrough
- Step 3: Severe PainRegular Paracetamol + strong opioid +/- Adjuvant
- Acute pain: Oxycodone IR –titrated to effect
- Chronic pain: Oxycodone M/R or Fentanyl Patch
