SIAH Flashcards
A 55-year-old man with a history of type 2 diabetes mellitus, hypothyroidism and epilepsy has bloods taken as part of his annual diabetic review:
- Na+129 mmol/l
- K+3.8 mmol/l
- Bicarbonate24 mmol/l
- Urea3.7 mmol/l
- Creatinine92 µmol/l
Due to his smoking history a chest x-ray is ordered which is reported as normal. Which one of the following medications is most likely to be responsible for the abnormality seen in the urea and electrolytes?
- Metformin
- Levothyroxine
- Carbamazepine
- Atorvastatin
- Pioglitazone
- Submit answer
Carbamazepine
The syndrome of inappropriate ADH secretion (SIADH) is characterised by hyponatraemia secondary to the dilutional effects of excessive water retention.
A 43-year-old man is admitted to hospital with pneumonia. His past medical history includes Addison’s disease for which he takes hydrocortisone (20mg in the mornings and 10mg in the afternoon). What is the most appropriate action with respect to his steroid dose?
- Continue to take the same dose
- Double hydrocortisone to 40mg mornings and 20mg afternoon
- Halve hydrocortisone to 10mg mornings and 5mg afternoon
- Continue to take the same dose + prescribe a proton pump inhibitor
- Continue the same morning dose + stop the afternoon dose
Double hydrocortisone to 40mg mornings and 20mg afternoon
You review a 49-year-old woman who has recently been diagnosed with rheumatoid arthritis. Around three months ago she was started on methotrexate with the addition of prednisolone to gain rapid control of her symptoms. She is now taking methotrexate 15mg once weekly and is still taking prednisolone 10mg od. Unfortunately she is experiencing a number of side-effects. Which one of the following is most likely to be secondary to the prednisolone?
- ‘Loss of appetite’
- ‘Tired all the time’
- ‘My shoulder and leg muscles feel weak’
- ‘Diarrhoea’
- ‘Blue tinge to my vision’
My shoulder and leg muscles feel weak’
Proximal myopathy is common with longer term steroid use. Some of the other side-effects may of course be secondary to either the methotrexate or ongoing rheumatoid disease.
A 70-year-old woman is started on alendronate after sustaining a Colles’ fracture. The orthopaedic consultant asks you to prescribe alendronate 70mg once weekly and explain the new treatment to the patient.
Select the two most appropriate pieces of information to communicate with the patient:
- A.Tablets should be swallowed 30 minutes after breakfast the same day each week
- B.Alendronate commonly causes constipation
- C.Antibiotics such as erythromycin and clarithromycin should be avoided
- D.Patients should see their dentist before treatment and have regular check-ups during treatment
- E.They should stop treatment and seek medical attention if heartburn or pain on swallowing develops
Correct answer: D E
The current BNF advice on how to take oral bisphosphonates is ‘Tablets should be swallowed whole with plenty of water while sitting or standing; to be taken on an empty stomach at least 30 minutes before breakfast (or another oral medicine); patient should stand or sit upright for at least 30 minutes after taking tablet’.
Oesophageal reactions are an important adverse effect of oral bisphosphonates. This is why the instructions on taking them are so specific. Patients should be made aware of this and the need to report new oesophageal-related symptoms.
Bisphosphonates have been linked to osteonecrosis of the jaw and it is therefore important to warn patients about this risk.
Constipation is a side-effect of alendronate but it is not as important to discuss as the other two points.
A 55-year-old woman who has type 2 diabetes mellitus is found to have a sodium of 127 mmol/l. She is a non-smoker. Which one of her medications is most likely to be responsible?
- Simvastatin
- Metformin
- Aspirin
- Pioglitazone
- Glimepiride
Glimepiride
Sulfonylureas such as glimepiride are known causes of SIADH.
A 24-year-old man is presecribed an extended course of oral prednisolone following a flare of ulcerative colitis. Which one of the following side-effects is most associated with prolonged corticosteroid use?
- Insomnia
- Thrombocytopaenia
- Hypotension
- Bronchospasm
- Hyperkalaemia
Psychiatric problems are common with longer term steroid use.
Insomnia
A 42-year-old female has presented with vomiting. She has had multiple episodes of vomiting over the past 3 days and has felt extremely nauseous. In addition to this she describes having a constant headache, and has felt particularly tired. Her past medical history includes depression which is managed with sertraline).
On examination, her pulse is 87 beats per minute, blood pressure 127/76mmHg and oxygen saturations of 98% on air. There is no evidence of peripheral oedema or a raised jugular venous pressure. On auscultation of her chest, heart sounds are normal and the lungs are unremarkable. You send for some investigations which yield the following:
- Na+122 mmol/L(135 - 145)
- K+3.8 mmol/L(3.5 - 5.0)
- Bicarbonate27 mmol/L(22 - 29)
- Urea3.1 mmol/L(2.0 - 7.0)
- Creatinine86 µmol/L(55 - 120)
- Random Blood Glucose4.1 mmol/L(4 - 11)
- Serum osmolality263 mOsm/kg(275 - 295)
- Urine osmolality857 mOsm/kg(300 - 900)
Which of the following management strategies is effective in the short term?
- Fluid restriction
- Furosemide
- Increased fluid intake
- Theophylline
- Vasopressin
SIADH is treated with fluid restriction
This patient has a marked hyponatremia alongside a low serum osmolality and high urine osmolality. This is therefore diagnostic of the syndrome of inappropriate antidiuretic hormone secretion (SIADH).
Fluid restriction is an effective short-term treatment for SIADH. This is because restriction of fluids temporarily increase the serum sodium in order for the underlying cause of SAIDH to be identified and treated.
Increasing fluid intake would have the opposite effect by further reducing the serum sodium causing a more severe hyponatremia.
Loop diuretics (such as furosemide) may be effective in hypervolemic patients with SIADH, however it is clear from this question stem that this patient is euvolemic.
In SIADH there is a lack of an effective negative feedback mechanism which results in continual anti-diuretic hormone (ADH) production, independent of serum osmolality. Giving vasopressin/ADH would therefore be inappropriate since this will worsen the effects of the SIADH.
Theophylline is a medication known to cause SIADH, not treat it.
Which one of the following is most associated with the syndrome of inappropriate ADH secretion?
- Colorectal adenocarcinoma
- Small cell lung cancer
- Malignant melanoma
- Gastric adenocarcinoma
- Squamous cell lung cancer
Small cell lung cancer
A common endocrine complication of small cell lung cancer is SIADH
A 38-year-old male presents to the emergency department with nausea and confusion. He has a background medical history of bipolar affective disorder, type two diabetes mellitus, alcohol dependency and he was recently in a road traffic accident where he sustained a minor head injury. His regular medications include lithium, carbamazepine, and metformin. He has been binge drinking more than 28 units of alcohol at a time for the last 3 months. On examination, he appears euvolemic.
Further investigations reveal:
- Na+119 mmol/L(135 - 145)
- Serum osmolality264 mOsm/kg(275 - 300)
- Urinary sodium42 mEq/L
- Urine osmolality556 mOsm/kg(50 - 1200)
- Lithium level 1.4 mmol/L(0.4 – 1.0)
What is the most likely cause for this patient’s hyponatremia?
- Alcohol binge drinking
- Carbamazepine
- Cranial diabetes insipidus secondary to head trauma
- Lithium
- Metformin
SIADH - drug causes: carbamazepine, sulfonylureas, SSRIs, tricyclics
Carbamazepine is the correct answer. The above clinical scenario is consistent with the syndrome of inappropriate antidiuretic hormone secretion (SIADH). Carbamazepine tricyclic antidepressants, serotonin selective reuptake inhibitors (SSRIs), and sulfonylureas are known to cause SIADH. SIADH causes hyponatremia with low serum osmolality and concentrated urine (urinary sodium >40 mEq/L) with inappropriate urine osmolality (>100 mOsm/kg) levels. In the setting of serum hypotonicity (serum osmolality <275 mOsm/kg), it is expected that the urine osmolality would be <100 mOsm/kg. These are the key features of SIADH.
Alcohol binge drinking is an incorrect answer. Alcohol bingeing can lead to ADH suppression in the posterior pituitary gland subsequently leading to polyuria. This is similar to cranial diabetes insipidus or partial cranial diabetes insipidus and typically causes hypernatremia with a raised serum osmolality and decreased urine osmolality. This is clearly inconsistent with the hyponatremia with low serum osmolality in this scenario.
Cranial diabetes insipidus secondary to head trauma is an incorrect answer. Diabetes insipidus is characterised by hypernatremia with a raised serum osmolality and decreased urine osmolality. This is inconsistent with the scenario above. The road traffic accident and minor head trauma in the patient’s history is a red herring.
Lithium is an incorrect answer. Lithium is associated with diabetes insipidus rather than SIADH. Diabetes insipidus is characterised by hypernatremia with a raised serum osmolality and decreased urine osmolality. Although lithium toxicity can cause nausea and confusion, it is important to note that the question is asking for the most likely cause of this patient’s hyponatremia and not his presenting symptoms. Additionally, this patient has a supratherapeutic lithium level (1.4 mmol/L), however, lithium toxicity is not typically seen with levels <1.5 mmol/L. Mild symptoms, including nausea, fatigue, and tremor occur at lithium levels between 1.5 to 2.5 mmol/L. Moderate symptoms, including confusion, tachycardia, ataxia, and hypertonia occur at lithium levels between 2.5 to 3.5 mmol/L. Severe symptoms, including hyperthermia, hypotension, seizures and coma occur at lithium levels between >3.5 mmol/L.
Metformin is an incorrect answer. Metformin is not associated with SIADH. However, sulfonylureas, such as glimepiride and glipizide, are associated with SIADH.
A 70-year-old man with a history of smoking 15 cigarettes/day presents with drowsiness, weight loss and a persistent cough. His investigations show:
- Na+115 mmol/l135-145 mmol/l
- K+5.1 mmol/l3.5 - 5.0 mmol/l
- Urea3 mmol/l2.0-7 mmol/l
- Creatinine74 µmol/l55-120 µmol/l
- Plasma osmolality270 mOsm/kg285-295 mOsm/kg
- Urine osmolality1210500 - 800 mOsm/kg
What is the most likely diagnosis?
- Small cell lung cancer
- Hypothyroidism
- Adenocarcinoma of the lung
- Congestive cardiac failure
- Squamous cell carcinoma
A common endocrine complication of small cell lung cancer is SIADH
Hyponatraemia, reduced plasma osmolality and increased urine osmolality are suggestive of syndrome of inappropriate ADH secretion (SIADH).
The increase in ADH causes more aquaporin utilisation in the collecting duct system of the kidney. This causes more water to be retained, diluting the electrolytes in the blood and making the electrolytes in the urine more concentrated.
Small cell lung cancer is a common cause of SIADH and is the most likely diagnosis in this man with an extensive smoking history, cough and weight loss.
A 42-year-old female has presented with vomiting. She has had multiple episodes of vomiting over the past 3 days and has felt extremely nauseous. In addition to this she describes having a constant headache, and has felt particularly tired. Her past medical history includes depression which is managed with sertraline).
On examination, her pulse is 87 beats per minute, blood pressure 127/76mmHg and oxygen saturations of 98% on air. There is no evidence of peripheral oedema or a raised jugular venous pressure. On auscultation of her chest, heart sounds are normal and the lungs are unremarkable. You send for some investigations which yield the following:
- Na+122 mmol/L(135 - 145)
- K+3.8 mmol/L(3.5 - 5.0)
- Bicarbonate27 mmol/L(22 - 29)
- Urea3.1 mmol/L(2.0 - 7.0)
- Creatinine86 µmol/L(55 - 120)
- Random Blood Glucose4.1 mmol/L(4 - 11)
- Serum osmolality263 mOsm/kg(275 - 295)
- Urine osmolality857 mOsm/kg(300 - 900)
Which of the following management strategies is effective in the short term?
- Fluid restriction
- Furosemide
- Increased fluid intake
- Theophylline
- Vasopressin
SIADH is treated with fluid restriction
This patient has a marked hyponatremia alongside a low serum osmolality and high urine osmolality. This is therefore diagnostic of syndrome of inappropriate antidiuretic hormone secretion (SIADH).
Fluid restriction is an effective short-term treatment for SIADH. This is because restriction of fluids temporarily increase the serum sodium in order for the underlying cause of SAIDH to be identified and treated.
Increasing fluid intake would have the opposite effect by further reducing the serum sodium causing a more severe hyponatremia.
Loop diuretics (such as furosemide) may be effective in hypervolemic patients with SIADH, however it is clear from this question stem that this patient is euvolemic.
In SIADH there is a lack of an effective negative feedback mechanism which results in continual anti-diuretic hormone (ADH) production, independent of serum osmolality. Giving vasopressin/ADH would therefore be inappropriate since this will worsen the effects of the SIADH.
Theophylline is a medication known to cause SIADH, not treat it.
A 32-year-old female presents to her GP. She is complaining of weakness, a headache and nausea. She has a past medical history of hypothyroidism, depression, migraine, hay fever and asthma. The GP orders some bloods:
- Na+126 mmol/l
- K+4.2 mmol/l
- Urea3.6 mmol/l
- Creatinine82 µmol/l
Which medication is most likely responsible for her symptoms?
- Propranolol
- Levothyroxine
- Loratadine
- Salbutamol
- Fluoxetine
SSRIs are a cause of SIADH
Fluoxetine is a cause of SIADH. SIADH causes low sodium which can cause the headache, weakness and nausea.
The other medications do not cause a low sodium.
A 78-year-old male presents to the medical assessment unit after becoming confused over the last 4 days. He has vomited twice and complains of a headache. He has a history of type 2 diabetes mellitus and depression, and his medications include metformin, ramipril and sertraline.
Examination findings are insignificant. He doesn’t appear septic.
A series of investigations are performed.
ResultReference Range
- Na+ 129 mmol/L(135 - 145)
- K+ 4.2 mmol/L(3.5 - 5.0)
- Urea 2.6 mmol/L(2.0 - 7.0)
- Creatinine 68 µmol/L(55 - 120)
- Glucose 5.8 mmol/L(4 - 7)
ResultReference Range:
- Serum osmolality 255 mOsm/kg >275 mOsm/kg
- Urine osmolality 136 mOsm/kg <100 mOsm/kg
- Urinary sodium 53 mmol/L <20 mmol/L
Based on the likely diagnosis, what is the most appropriate initial management?
- Desmopressin
- Fluid restriction
- IV 0.9% sodium chloride
- IV hypertonic saline
- Indomethacin
SIADH is treated with fluid restriction
Syndrome of inappropriate antidiuretic hormone secretion (SIADH) presents with hyponatremia, hypo-osmolar serum and hyper-osmolar urine with increased urinary sodium. Patients should be fluid restricted, to increase serum sodium and correct the hyponatremia. Hyponatremia can cause cerebral oedema which presents with symptoms such as lethargy, nausea and vomiting, headache, confusion and decreased GCS.
Pulmonary infections (i.e. pneumonia) and selective serotonin reuptake inhibitors (SSRIs) can both cause SIADH. The increase in ADH triggers increased insertion of aquaporin-2 channels in the collecting ducts and distal convoluted tubules, increasing water reabsorption. This results in reduced excretion of water in the urine, diluting electrolytes in the blood and increasing the osmolality of the urine.
Desmopressin is a synthetic form of ADH, used in diabetes insipidus where there is a central cause e.g. damage to the pituitary from surgery or head trauma. This patient already has excess ADH, so desmopressin would make the condition worse.
IV 0.9% sodium chloride would be used in hypovolaemic hyponatremia, but is not needed in this euvolemic patient.
IV hypertonic saline is used in moderate hyponatremia (serum sodium 120-129 mmol/L).
Indomethacin is a non-steroidal anti-inflammatory drug (NSAID) and is not used in the treatment of SIADH
