Renal ~ Short Answer

Question 1.

A 6 year old child weighing 25 kg with no significant past history presents with diabetic ketoacidosis.

A.) What criteria need to be met to diagnose DKA?

Show Answer

  • Venous pH < 7.3 or HCO3 < 15 mmol/L
  • Presence blood or urinary ketones

(2 marks)

 B.) List the major management steps in this child in order.

Show Answer

  • Resuscitation
  • Supportive measures
  • Fluids
  • K replacement
  • Insulin
  • Monitoring
  • Bicarbonate

(5 marks, bold and in that order)

C.) How would you assess the need for fluid boluses and what volume would you give?

Show Answer

  • Acidosis confounds accurate assessment of dehydration
  • Use central capillary refill > 2s as indication of shock
  • 10 ml/kg fluid bolus IV (+ 250 mls) and reassess
  • Rarely need > 20 ml/kg bolus (500 mls)
  • Danger of precipitating cerebral oedema

(3 marks)

D.) Describe, with calculations, the fluid volume and rate you would start in this child assuming 5% dehydration.

Show Answer

  • Deficit + maintenance
  • Replace over 24-48 hours
  • Deficit = % x BW x 10 = 5 x 25 x 10 = 1250 ml
  • Maintenance
    • Rule of 4/2/1 ml/kg/hr = 40 + 20 + 5 = 65 ml/hr
    • OR 100/50/20 ml/g/d = 1000 + 500 + 100 = 1600 ml/d = 67 ml/hr
  • Replacement over 24 hours:
    • 1250/24 = 52 ml/hr
    • 52 + 65 = 117 ml/hr
  • Replacement over 48 hours
    • 1250/48 = 26 ml/hr
    • 26 + 65 = 91 ml/hr
  • Reassess frequently

(6 marks, bold equations + reasonably long replacement time)

 E.) When would you replace K and how?

Show Answer

  • Once serum K < 5.5 mmol/l
  • Not if anuric
  • KCL 40 mmol/L of fluids if < 30 kg
  • Then replace based on K levels
  • Continue whilst giving fluids and insulin

(4 marks)

 F.) What type, dose and route of insulin would you give?

Show Answer

  • Rapid-acting insulin e.g. Actrapid
  • 1 U/kg/hr = 2.5 U/hr

(4 marks)

Show Answer

 G.) When would you discontinue the IV insulin?

Show Answer

  • Child alert
  • Metabolically stable i.e. pH > 7.3 and HCO3 > 15 mmol/L

(2 marks)

 H.) What ongoing monitoring is required initially?

Show Answer

  • Hourly obs (HR, BP, RR, LOC, neuro status); q2-4 hr temp
  • Hourly glucose and blood ketones whilst on IV insulin
  • K within 1 hour starting insulin infusion
  • VBS and BSL q2hr for 6 hours then q2-4 hours after (more frequent if severe)
  • U&Es q2-4 hrs for first 12-24 hours

(4 marks)

This table shows this patient’s 3 VBGs taken after treatment has commenced:

Renal Table 1A Short Answer

I.) What is the main concern here and why?

Show Answer

  • Na
  • Na should rise as glucose falls
  • If Na fall indicates too much fluid correction and can herald cerebral oedema

(3 marks)

J.) Calculate the true serum values for the electrolyte referred to above

Show Answer

  • Corrected Na = measured Na + 0.3 (BSL – 5.5) mmol/L
  • OR for every 10 mmol/L rise in BSL above 5.5 mmol/L the Na rises by 3 mmol/L
  • 162; 161: 156

(2 marks)

K.) After 6 hours of treatment the child becomes irritable and confused. What is the likely diagnosis and what are the risk factors for this condition?

Show Answer

  • Cerebral oedema
  • Risk factors:
  • First presentation
  • Long history of poor control
  • < 5 years old
  • Initial hypernatraemia > 160 mmol/L
  • No Na rise and BSL falls
  • Na falling as BSL falls

(4 marks)

L.) What are your next management steps?

Show Answer

  • Mannitol 20% 0.5g/Kg = 12.5 g IV over 20minutes
  • Nurse head up
  • Reduce fluid input by at least 1/3
  • Reassess
  • May need repeat Mannitol
  • Intubation and ventilation
  • ICU

(4 marks)

Author: J Haire

Ref: RCH DKA guidelines


 

Question 2.

A 62 year old man with known chronic renal failure presents with respiratory failure secondary to pulmonary oedema. Oxygen saturation is 89% on 100% oxygen utilizing bi-level positive airway pressure (BiPAP). His observations are:

  • Glasgow Coma Score 14
  • Temperature 37.0°C
  • Respiratory Rate 32/min
  • Systolic blood Pressure 90mmHg
  • Electrocardiograph rate of 105/min with regular broad complex rhythm

An urgent potassium level of 8.7 mmol/L (reference range: 3.5-4.9 mmol/L) had been recorded

A.) What are the main problems this patient is presenting with?

Show Answer

  • Critical hyperkalaemia causing malignant arrhythmia
  • Respiratory failure secondary to pulmonary oedema despite non-invasive ventilation
  • Hypotension

(3 marks)

 B.) What are the potential life-threats if you perform rapid sequence induction on this patient?

Show Answer

  • Worsening of hyperkalaemia with deteriorating rhythm (VF/VT)
  • Worsening hypotension secondary to induction agent and PPV leading to asystolic arrest
  • Inability to secure airway

(3 marks)

 C.) What are your alternatives to rapid sequence intubation in this patient?

Show Answer

  • Continue BiPAP and dialyse patient
  • Delayed sequence intubation
  • Stabilisation of K and blood pressure prior to RSI

(3 marks; 3 reasonable alternatives)

D.) How would you optimise this patient prior to proceeding with RSI?

Show Answer

  • Hyperkalaemia/stabilisation of myocardium
    • 20 mls Ca gluconate IV; repeat q 10 min; aim rhythm control
    • AND
      • Salbutamol 20 mg nebulised
      • + 10 rapid-acting insulin + 50 mls 10% Dextrose over 20 mins IV
      • +/- 50 mls NaHCO3 over 10 min IV
      • Repeat q30 min until arrhythmia corrected
    • Hypotension
      • Judicious fluid boluses watching for worsening resp failure
      • + vasopressor e.g. noradrenaline infusion
      • Aim normal BP
    • If anxious then sedation with ketamine to help respiratory effort
    • Sitting up
    • Maximise NIV settings

(6 marks)

 E.) Which induction agent would you use and why? What are its drawbacks in this patient?

Show Answer

  • Ketamine
    • Maintains BP, airway reflexes, breathing, smooth
    • But could worsen arrhythmia and can cause laryngospasm, emesis
  • Propofol
    • Familiar, smooth
    • Cold worsen hypotension
  • Fentanyl
    • Maintain BP, smooth
    • Takes longer to work, respiratory depression

(2 marks; reasonable choice + reasons)

 F.) Which paralytic agent would you use and what dose?

Show Answer

  • Rocuronium 1 mg/kg

(1 mark; reasonable choice, not sux unless corrected K)

Author: J Haire

Ref: Tintinalli p.203-4


 

Question 3.

An 83 year old woman presents with a three day history of malaise and polyuria. She has a past history of Type 1 Diabetes and Hypertension.

Her observations are:

Renal Table 1 Short Answer

Renal Table 2 Short Answer

A.) Describe, with calculations her acid-base disorder.

Show Answer

  • Low HCO3 = metabolic acidosis
  • Anion gap = Na – (HCO3 + Cl) = 125 – (7 + 81) = 37
  • Raised anion gap
  • AGMA
  • Delta gap = ?AG/?HCO3 = 37/17 = 25/17 = 1.5 = pure AGMA

(3 marks)

 

B.) Comment on her electrolytes

Show Answer

  • Corrected Na = Na + 0.3 (BSL – 5.5) = 125 + 0.3 (54.5-5.5) = 139.7 = 140
  • Moderate hyperkalaemia
  • Hypochloraemia

(3 marks)

C.) Comment on her renal function

Show Answer

  • Raised urea and creatinine
  • Moderate renal failure

(2 marks)

D.) Are there any other abnormalities?

Show Answer

  • Markedly hyperglycaemic
  • Raised osmolality
  • Osmolar gap = measured Osm – calculated Osm (2 x Na + U + BSL + ETOH) = 337- (2 x 125 + 25 + 54.5) = 337 – 329.5 = 7.5 = no osmolar gap

(3 marks)

E.) What is the most likely cause of her metabolic abnormalities?

Show Answer

  • DKA
  • Dehydration

(2 marks)

Author: J Haire

Ref: Toxicology Handbook p. 107-110 and Tintinalli p. 102-12


 

Question 4.

A 45 year old woman with a past history of depression presents to your emergency department with 2 weeks of nausea, weakness and lethargy. There has been no vomiting or diarrhoea.

Renal Table 4 Short Answer

A.) Describe her acid-base disorder

Show Answer

  • Alkalotic
  • High bicarbonate and CO2 normal = metabolic alkalosis

(2 marks)

B.) Comment on her compensation.

Show Answer

  • Compensation
    • HCO3 raised by 15
    • CO2 should rise by 15 x 0.6 = expected pCO2 = 49
    • Not adequately compensated

(2 marks)

C.) Comment on her electrolytes

Show Answer

  • Moderate hyponatraemia
  • Severe hypokalaemia
  • Severe hyochloraemia

(3 marks)

D.) Are there any other abnormalities?

Show Answer

  • pO2 low normal
  • indicates raised A-a gradient
  • mild hyperglycaemia

(2 marks)

E.) What are the most likely processes occurring?

Show Answer

  • Renal loss of acid and electrolytes
  • Possible secondary lung pathology

(2 marks)

F.) What is the most likely diagnosis? And differentials?

Show Answer

  • Diuretic overuse/abuse
  • Vomiting/diarrhoea but states no GIT loss in question
  • Primary renal tubular disease e.g. Bartter’s syndrome
  • Adrenogenital syndrome
  • Cushing’s syndrome
  • Primary hyperaldosteronism

(3 marks)

Author: J Haire

Ref: Toxicology Handbook p. 107-110


 

 

 

Leave a Reply

Your email address will not be published. Required fields are marked *