Learn Med-surg: neuro, endocrine & renal from scratch
Before this: Nursing fundamentals
1What this topic covers
This topic covers the brain and spinal cord, the hormone glands and the kidneys: stroke, seizures, raised intracranial pressure, spinal cord injury, diabetes emergencies, thyroid and adrenal disorders, water balance (SIADH and diabetes insipidus), acute and chronic kidney disease and dialysis.
These systems control each other. Low sodium causes seizures, low glucose mimics stroke, and kidney failure raises potassium. Exam questions often hide one system’s problem inside another’s.
2Stroke, seizures and the injured brain
Recognise a stroke with FAST: Face drooping, Arm weakness, Speech difficulty, Time to call for help. Always check the blood glucose, because hypoglycaemia can mimic a stroke.
Most strokes are ischaemic. A CT scan first excludes bleeding. IV thrombolysis is usually given within 4.5 hours of the time the patient was last known well, with the blood pressure below about 185/110 mmHg. Keep the patient nil by mouth until a swallow screen is done.
During a seizure: protect from injury, time it, put nothing in the mouth and use the recovery position afterwards. A seizure lasting five minutes or more is status epilepticus and needs a benzodiazepine.
Raised intracranial pressure: the first sign is a change in level of consciousness. Cushing’s triad (rising blood pressure, slow pulse, irregular breathing) is late. Nurse the head up at about 30° with the neck straight, prevent straining and space out care.
Spinal cord injury: log-roll the patient. Injury at C3–C5 threatens the diaphragm. Injury at T6 or above can cause neurogenic shock and later autonomic dysreflexia, usually triggered by a full bladder.
Self-check Which change is usually the earliest sign of rising intracranial pressure?
- A change in level of consciousness
- Bilateral fixed, dilated pupils
- Bradycardia with hypertension
- Respiratory arrest
Answer: A change in level of consciousness. The cortex is very sensitive to reduced blood flow, so restlessness or drowsiness comes first. Fixed pupils, Cushing’s triad and respiratory arrest are late signs of herniation.
3Diabetes emergencies
Hypoglycaemia is a glucose below 4.0 mmol/L (about 70 mg/dL). If the patient can swallow, give 15–20 g of fast-acting carbohydrate, recheck after 10–15 minutes, then give a longer-acting carbohydrate. If they cannot swallow, give IM glucagon or IV glucose.
Compare the two hyperglycaemic emergencies:
- DKA: severe insulin lack, mostly type 1. Ketones high, pH low, Kussmaul breathing, develops over hours.
- HHS: mostly older people with type 2. Very high glucose and osmolality, little or no ketosis, severe dehydration, develops over days.
Both start with IV fluids. In DKA, a fixed-rate insulin infusion follows. Insulin drives potassium into cells, so potassium can fall fast and is checked often. When glucose falls, glucose is added to the drip and the insulin continues until the ketones have cleared.
Self-check During treatment of DKA, the glucose falls to 12 mmol/L but ketones are still raised. What usually happens?
- All IV fluids are stopped
- Glucose is added to the fluids and the insulin continues
- The insulin infusion is stopped
- The patient eats and goes home
Answer: Glucose is added to the fluids and the insulin continues. Insulin is needed to switch off ketone production, so it continues. Stopping it because the glucose looks better lets the acidosis return.
4Thyroid, adrenal and water balance
Hypothyroidism slows everything down (cold, tired, weight gain, constipation). Levothyroxine is taken on an empty stomach.
Hyperthyroidism speeds everything up (heat intolerance, weight loss, tremor, palpitations). Thionamides such as carbimazole can cause agranulocytosis: a sore throat or fever needs an urgent blood count.
After thyroid surgery watch for a neck haematoma (airway), low calcium (tingling, cramps) and hoarseness (laryngeal nerve damage).
Cortisol comes from the adrenal cortex. Too much gives Cushing’s syndrome; too little gives Addison’s disease with low sodium, high potassium, low glucose and low blood pressure. Never stop long-term steroids suddenly, and double the dose during illness as advised.
ADH controls water. Too much (SIADH) gives low sodium and concentrated urine; it is treated with fluid restriction. Too little effect (diabetes insipidus) gives large volumes of dilute urine and high sodium; cranial DI is treated with desmopressin. Correct chronic low sodium slowly.
Self-check Which pattern fits SIADH?
- High glucose with glucose in the urine
- High serum sodium with dilute urine
- Low potassium with high blood pressure
- Low serum sodium with concentrated urine
Answer: Low serum sodium with concentrated urine. Excess ADH holds on to water, diluting the blood and concentrating the urine. High sodium with dilute urine is diabetes insipidus, the opposite problem.
5Kidney injury and dialysis
Acute kidney injury is a fast fall in kidney function: a rise in creatinine or urine output below 0.5 mL/kg/h for 6 hours.
Think of three causes: pre-renal (too little blood flow, such as dehydration), intrinsic (damage, such as nephrotoxic drugs) and post-renal (blockage, such as urinary retention). Check the catheter and scan the bladder.
Chronic kidney disease brings high potassium, high phosphate, anaemia from low erythropoietin and fluid overload. Patients limit potassium, phosphate, salt and often fluid, and take phosphate binders with meals.
For haemodialysis, protect the fistula arm: no blood pressure cuffs, blood tests or cannulas, and check the thrill and bruit. Weigh before and after each session. For peritoneal dialysis, cloudy fluid with abdominal pain suggests peritonitis.
6A worked example
Look for the link between the systems before choosing an action.
Worked exampleMr de Vries, 68, has type 2 diabetes and was found confused at home after three days of a chest infection. His glucose is 46 mmol/L, osmolality 360 mOsm/kg, ketones 0.8 mmol/L, pulse 118/min and blood pressure 96/58 mmHg. His mucous membranes are dry. What is happening and what is the priority?
1Very high glucose and osmolality without significant ketones in an older person with type 2 diabetes, developing over days: this is HHS, not DKA.
2He is severely dehydrated: tachycardic, hypotensive and dry. Fluid replacement is the first priority and often lowers the glucose on its own.
3Give IV fluids as prescribed and monitor glucose, sodium and osmolality often, because a very fast fall can cause cerebral oedema. Insulin is added at a low rate only if needed.
4HHS carries a high clot risk, so VTE prophylaxis is given as prescribed. Treat the chest infection, check his feet and record fluid balance and neurological observations.
Answer HHS triggered by infection: careful IV fluids first, with close monitoring of osmolality, sodium and glucose, then cautious insulin if needed.
7Common mistakes and how questions look
- Giving thrombolysis without checking the glucose or the CT scan.
- Waiting for Cushing’s triad instead of acting on a falling level of consciousness.
- Stopping insulin in DKA as soon as the glucose looks normal.
- Treating SIADH with more fluid, or correcting low sodium too fast.
- Taking blood pressure or blood samples on a fistula arm.
Easy questions test definitions and signs. Medium questions ask why a treatment works or what to monitor. Hard questions give a case where you must recognise the condition and choose the first safe action.
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