By the end of this note you will be able to take a focused history, perform a targeted exam and interpret basic investigations to recognise, grade and begin appropriate management of fluid imbalance in Kenyan adult patients. Always verify drug choices, doses and local protocols against the Kenya Ministry of Health guidelines and your hospital formulary.
Definition
Fluid balance is the net difference between fluid intake (oral, enteral, parenteral, metabolic water) and fluid output (urine, feces, insensible loss, drains, vomiting, diarrhea, third‑space loss). A positive balance leads to fluid overload; a negative balance results in dehydration or hypovolaemia.
Anatomy and physiology you need
| Structure/ system | Key role in fluid homeostasis |
|---|---|
| Kidneys (nephron) | Filter plasma, re‑absorb Na⁺/water, excrete waste |
| Renin‑angiotensin‑aldosterone system (RAAS) | Conserves Na⁺ and water when volume falls |
| Antidiuretic hormone (ADH) | Increases water re‑absorption in collecting ducts |
| Natriuretic peptides (ANP, BNP) | Promote natriuresis and vasodilation in overload |
| Capillary membrane (Starling forces) | Governs fluid shift between intravascular and interstitial spaces |
| Lymphatic system | Returns interstitial fluid to circulation |
| Gastro‑intestinal tract | Provides bulk intake, absorbs water and electrolytes |
Understanding how these components interact explains why disease states tip the balance toward excess or deficit.
Causes and risk factors
| Category | Common Kenyan examples | Why they disturb balance |
|---|---|---|
| Infectious | Severe malaria, TB meningitis, HIV‑associated opportunistic infections, bacterial sepsis | Fever, vomiting, diarrhoea, capillary leak, adrenal insufficiency |
| Hematologic | Sickle cell crisis, severe anaemia | Vaso‑occlusion → renal medullary ischemia, increased urine loss |
| Cardiovascular | Congestive heart failure, rheumatic valvular disease | Reduced forward flow → renal hypoperfusion, activation of RAAS |
| Renal | Acute kidney injury (AKI) from nephrotoxins, glomerulonephritis, HIV‑associated nephropathy | Impaired excretion, sodium retention |
| Gastro‑intestinal | Acute gastroenteritis, chronic diarrhoea (e.g., from parasitic infection) | Direct fluid loss, electrolyte depletion |
| Endocrine | Diabetes mellitus (DKA), adrenal insufficiency | Osmotic diuresis, loss of aldosterone effect |
| Iatrogenic | Over‑aggressive IV fluids, diuretic over‑use, dialysis errors | Direct alteration of intake‑output ratio |
| Pregnancy & obstetric | Preeclampsia, postpartum haemorrhage | Altered plasma volume, bleeding |
Risk factors specific to our setting include limited access to clean water, high prevalence of infectious diseases, delayed presentation, and use of traditional remedies that may contain diuretics.
Pathophysiology
Fluid overload → infection/heart failure → systemic inflammation → ↑ capillary permeability → third‑space shift → ↓ effective circulating volume → RAAS & ADH activation → Na⁺/water retention → further overload → pulmonary/edema.
Dehydration / hypovolaemia → vomiting/diarrhoea/fever → ↓ intravascular volume → ↓ renal perfusion → RAAS activation → Na⁺ retention but insufficient → continued loss → tissue hypoperfusion → lactic acidosis, AKI.
Mixed states (e.g., septic shock) → simultaneous vasodilation (relative hypovolaemia) and capillary leak (relative overload) → requires careful assessment of intravascular vs. interstitial compartments.
These causal chains guide the clinical focus: identify the primary driver (loss vs. retention) and the organ systems involved, then target therapy accordingly.
Clinical features
| History element | Why it matters |
|---|---|
| Onset and tempo of weight change (gain or loss) | Rapid gain suggests fluid overload; rapid loss suggests dehydration or diuresis. |
| Daily fluid intake (water, tea/coffee, oral rehydration solutions, alcohol, IV fluids) | Quantifies net balance; excess intake can precipitate overload, especially with renal impairment. |
| Urine output (volume, frequency, colour, presence of foaming) | Low output (<0.5 mL/kg/h) points to oliguria/AKI; high output with dilute urine suggests loss (diabetes insipidus, osmotic diuresis). |
| Vomiting, diarrhoea, loose stools, fever, night sweats | Gastro‑intestinal losses are common causes of dehydration in tropical settings (malaria, dysentery, TB). |
| Pulmonary symptoms (dyspnoea, orthopnoea, cough, frothy sputum) | Fluid accumulation in lungs (pulmonary oedema) is a hallmark of volume overload or cardiac failure. |
| Edema distribution (peripheral, sacral, facial, abdominal) | Dependent oedema indicates hydrostatic pressure rise; facial/ periorbital swelling suggests hypo‑albuminaemia or nephrotic syndrome. |
| Recent infections (HIV, TB, malaria, schistosomiasis) | These diseases can cause capillary leak, renal loss of protein, or direct renal injury leading to fluid shifts. |
| Medications (diuretics, ACE‑inhibitors, ARBs, antiretrovirals, anti‑TB drugs) | Diuretics can precipitate dehydration; ACE‑I/ARBs may cause renal hypoperfusion; some antiretrovirals cause nephrotoxicity. |
| Past renal disease (CKD, glomerulonephritis, sickle‑cell nephropathy) | Baseline renal reserve determines ability to handle fluid loads or losses. |
| Pregnancy status | Physiological plasma volume expansion; pre‑eclampsia can cause abrupt fluid shifts. |
| Dietary sodium intake | High salt intake promotes water retention, worsening overload. |
| Symptoms of orthostatic intolerance (dizziness, syncope) | Suggest intravascular depletion. |
Examination findings and pathophysiology
| Finding | Mechanistic explanation |
|---|---|
| Weight change (gain >2 kg in 24 h or loss >2 kg) | Direct measure of net fluid balance. |
| Blood pressure (hypotension or hypertension) | Low BP → volume depletion; high BP with signs of overload may reflect fluid excess or renal sodium retention. |
| Pulse (tachycardia) | Compensatory response to hypovolaemia; may also be sinus tachycardia from fever or pain. |
| Skin turgor & mucous membranes (dry, poor recoil) | Dehydration reduces interstitial fluid, flattening skin folds. |
| Capillary refill (>2 s) | Peripheral hypoperfusion from low intravascular volume. |
| Jugular venous pressure (JVP) (elevated) | Increased right‑sided filling pressures from volume overload or heart failure. |
| Peripheral edema (pitting, dependent) | Elevated hydrostatic pressure in capillaries pushes fluid into interstitium. |
| Facial/ periorbital edema | Low oncotic pressure (hypo‑albuminaemia) or fluid overload. |
| Ascites (shifting dullness, fluid wave) | Severe plasma volume expansion with portal hypertension or hypo‑albuminaemia. |
| Lung auscultation (crackles, wheeze) | Interstitial fluid from pulmonary oedema. |
| Heart sounds (S3 gallop) | Volume overload leading to rapid ventricular filling. |
| Abdominal exam (bowel oedema, tenderness) | Fluid sequestration in gut wall (common in severe malaria, sepsis). |
| Neurological status (confusion, lethargy) | Cerebral hypoperfusion in dehydration or cerebral oedema in severe overload. |
Differential diagnosis
| Condition | Points toward it | Distinguishing feature |
|---|---|---|
| Dehydration (hypovolaemia) | Polyuria, vomiting/diarrhoea, orthostatic hypotension, dry mucosa | Low JVP, high urine specific gravity, BUN/creatinine ratio >20 |
| Congestive heart failure | Dyspnoea, orthopnoea, elevated JVP, S3 | Pulmonary crackles, cardiomegaly on CXR, BNP high |
| Nephrotic syndrome | Massive proteinuria, hypo‑albuminaemia, oedema, hyperlipidaemia | Urine albumin >3 g/day, oedema despite normal BP |
| Acute kidney injury (intrinsic) | Oliguria, recent nephrotoxic drugs, sepsis, HIV/TB | Rising creatinine, granular casts, fractional excretion of Na >2% |
| Liver cirrhosis with ascites | History of alcohol, hepatitis, jaundice, spider naevi | Low albumin, portal hypertension signs, ascitic fluid SAAG >1.1 g/dL |
| Pulmonary oedema secondary to malaria | Recent fever, malaria smear positive, hemolysis | Rapid onset, haemoglobin fall, malaria parasites on smear |
| Sickle‑cell vaso‑occlusive crisis with renal involvement | Known sickle cell, pain crises, haematuria | Positive sickle cell test, renal papillary necrosis on imaging |
Investigations
| Test | What it answers | Interpretation |
|---|---|---|
| Full blood count | Anaemia, infection, eosinophilia | Low Hb suggests chronic disease; leukocytosis points to infection |
| Serum electrolytes & creatinine | Volume status, renal function, electrolyte disturbances | ↑Creatinine = AKI/CKD; ↑Na with oedema = hypernatraemic dehydration |
| Blood urea nitrogen (BUN) | Prerenal vs intrinsic renal loss | BUN/Cr >20 suggests hypovolaemia |
| Serum albumin | Oncotic pressure, protein loss | <30 g/L indicates hypo‑albuminaemia (nephrotic, liver disease) |
| Urinalysis (dipstick + microscopy) | Proteinuria, haematuria, casts | +3 protein = nephrotic; granular casts = ATN |
| Urine sodium & fractional excretion of Na (FENa) | Prerenal vs intrinsic AKI | FENa <1% = prerenal; >2% = intrinsic |
| Chest X‑ray | Pulmonary congestion, pleural effusion | Kerley B lines, cardiomegaly = fluid overload |
| Echocardiogram (if available) | Cardiac function, ejection fraction | EF <40% supports heart failure |
| Abdominal ultrasound | Ascites, liver size, renal size | Small kidneys = chronic disease; large liver with nodularity = cirrhosis |
| BNP/NT‑proBNP | Cardiac vs renal cause of oedema | Elevated >500 pg/mL favors heart failure |
| Malaria rapid diagnostic test / thick smear | Presence of Plasmodium | Positive in febrile patients with oedema |
| HIV test (if status unknown) | Immunosuppression risk factor | Positive influences differential (TB, nephropathy) |
| TB GeneXpert (sputum/urine) | Active TB | Positive in disseminated TB causing renal involvement |
Diagnosis and severity
- Integrate history, exam and investigations to categorize the fluid imbalance as hypovolaemia, euvolaemia, or hypervolaemia and identify the underlying aetiology (e.g., diarrhoeal dehydration, nephrotic syndrome, heart failure, AKI).
- Severity grading (adapted for bedside use):
| Category | Clinical criteria | Management urgency |
|---|---|---|
| Mild | Weight change <2 kg, stable vitals, urine output >0.5 mL/kg/h, no organ dysfunction | Outpatient monitoring or oral therapy |
| Moderate | Weight change 2–5 kg, BP borderline, urine output 0.3–0.5 mL/kg/h, early signs of organ stress (elevated creatinine, mild dyspnoea) | Admit, IV fluid titration or diuretics, close labs |
| Severe | Weight change >5 kg, hypotension or severe hypertension, urine output <0.3 mL/kg/h, overt organ failure (pulmonary oedema, encephalopathy, AKI stage 3) | ICU/high‑dependency care, aggressive fluid management, treat underlying cause urgently |
- Document primary diagnosis (e.g., “Severe hypovolaemic dehydration secondary to acute gastro‑enteritis in a HIV‑positive adult”) and secondary contributors (e.g., “Concurrent mild AKI”).
- Re‑assessment schedule:
- Every 2 h for severe cases (vitals, urine output, weight).
- Every 4–6 h for moderate cases.
- Daily for mild cases.
- Safety checkpoints: ensure electrolytes are checked before and after any major fluid shift; watch for rapid correction of hyponatraemia or hyperkalaemia; avoid fluid overload in patients with reduced cardiac reserve.
By following this structured approach, Year‑4 MBChB students will be able to recognise, categorise and manage fluid balance disturbances efficiently in the Kenyan clinical environment.
Management
Immediate stabilisation
| Problem | Immediate action | Rationale |
|---|---|---|
| Hypovolaemia (SBP < 90 mmHg, tachycardia) | Rapid isotonic crystalloid bolus (e.g. normal saline) via large‑bore IV; reassess haemodynamics after 250 ml | Restores intravascular volume, improves perfusion |
| Hypervolaemia with pulmonary oedema | Give high‑flow oxygen, position upright, start loop diuretic IV, consider non‑invasive ventilation if SpO₂ < 90 % | Reduces preload, improves gas exchange |
| Severe hyponatraemia with seizures or coma | Hypertonic saline (3 %) bolus under cardiac monitoring | Raises serum Na + rapidly enough to stop cerebral oedema |
| Hyperkalaemia with ECG changes | Calcium gluconate IV (to stabilise myocardium), insulin + glucose, nebulised β‑agonist, consider loop diuretic or dialysis | Protects heart while shifting K⁺ intracellularly |
| Acute kidney injury (AKI) with oliguria | Stop nephrotoxic drugs, optimise preload, consider renal replacement therapy if refractory | Prevents further renal insult |
Definitive treatment – directed at the underlying aetiology
- Fluid loss states (gastro‑enteritis, malaria, sickle‑cell crisis): replace with isotonic crystalloids; add oral rehydration solution (ORS) when able; treat infection (antibiotics for bacterial sepsis, antimalarials, anti‑TB drugs).
- Fluid overload states (heart failure, nephrotic syndrome, severe protein‑losing diarrhoea): loop diuretic ± thiazide, sodium restriction, treat precipitating infection, consider ACE‑inhibitor or ARB for cardiac/renal protection.
- Electrolyte derangements:
- Hyponatraemia – restrict free water, give hypertonic saline only if severe; address SIADH, adrenal insufficiency, or volume status.
- Hypernatraemia – give hypotonic fluids (5 % dextrose) slowly; correct underlying water loss.
- Hyperkalaemia – as above; address chronic renal failure with diet, potassium‑binding resins.
- Acid‑base disorders – give bicarbonate only for severe metabolic acidosis (pH < 7.1) after confirming cause; treat underlying lactic acidosis, renal failure, or toxin.
Monitoring
- Vital signs every 15 min until stable, then hourly.
- Input‑output charting (accurate urine collection, drains, insensible losses).
- Daily weight; bedside fluid balance (wet‑dry weight).
- Serum electrolytes, creatinine, urea, glucose every 6–12 h in acute phase; then daily.
- ECG for potassium or volume overload changes.
- For patients on diuretics, monitor for hypovolaemia, electrolyte loss, and renal function.
Safety / Contra‑indications
- Avoid rapid over‑correction of chronic hyponatraemia (risk of osmotic demyelination).
- Do not give loop diuretics in hypovolaemic AKI without restoring volume first.
- Hypertonic saline contraindicated in hypernatremic patients or those with fluid overload unless life‑threatening cerebral edema.
- ACE‑inhibitors/ARBs should be withheld in acute kidney injury with rising creatinine or hyperkalaemia.
Complications and prognosis
- Acute kidney injury – may progress to chronic kidney disease if insult is prolonged; early reversal improves outcome.
- Pulmonary oedema – if untreated leads to respiratory failure, need for mechanical ventilation.
- Electrolyte extremes – seizures (hyponatraemia), cardiac arrhythmias (hyperkalaemia, hypernatraemia).
- Osmotic demyelination syndrome – from overly rapid correction of chronic hyponatraemia; presents with quadriplegia, dysarthria, altered consciousness.
- Hypovolaemic shock – multi‑organ failure, high mortality if not rapidly corrected.
- Volume overload in CKD – accelerates cardiovascular disease, worsens hypertension.
Prognosis hinges on prompt recognition, correction of the underlying cause, and avoidance of iatrogenic over‑correction.
High‑yield exam points
- Look‑alike conditions – differentiate hypovolaemic hyponatraemia (low Na + low volume) from euvolaemic SIADH (low Na + normal volume).
- Common wrong first step – giving diuretics to a patient who is actually hypovolaemic; always assess volume status first.
- Bedside examiner questions – “What is your assessment of the patient’s fluid status? How will you calculate the daily fluid balance? Which investigations will you order to confirm your diagnosis?”
- Key physical signs – skin turgor, mucous membranes, jugular venous pressure, lung crackles, peripheral oedema, orthostatic vitals.
- Management hierarchy – ABC → restore perfusion → correct electrolytes → treat cause → monitor.
Clinical case
Case: 28‑year‑old male with known sickle‑cell disease presents with 2‑day history of fever, diffuse abdominal pain, and vomiting. On exam: BP 88/54 mmHg, HR 118 bpm, dry mucous membranes, capillary refill > 3 sec, mild scleral icterus, and a tender, enlarged spleen. Labs: Hb 7 g/dL, Na⁺ 128 mmol/L, K⁺ 4.2 mmol/L, creatinine 1.8 mg/dL, urine output 20 ml/h.
Questions
- What is the most urgent immediate intervention?
Answer: Give a rapid isotonic crystalloid bolus (250 ml) and reassess haemodynamics.
- Which underlying cause is most likely driving his hyponatraemia?
Answer: Hypovolaemic hyponatraemia secondary to vomiting and sequestration of fluid in the spleen (sickle‑cell sequestration crisis).
- After stabilisation, what definitive therapy should be started?
Answer: Initiate broad‑spectrum antibiotics (covering gram‑negative sepsis), give exchange transfusion for sickle‑cell crisis, and continue isotonic fluid replacement guided by urine output and daily weight.
Practice questions
Question 1
A 45‑year‑old woman with known CKD stage 4 presents with progressive dyspnoea, bilateral basal crackles, and peripheral oedema. BP 150/90 mmHg, HR 92 bpm, SpO₂ 88 % on room air. Labs: Na⁺ 138 mmol/L, K⁺ 5.8 mmol/L, creatinine 3.2 mg/dL. What is the next best step?
A. Give oral furosemide tablets
B. Start IV loop diuretic and give supplemental oxygen
C. Administer hypertonic saline
D. Begin dialysis immediately
Answer: B. Start IV loop diuretic and give supplemental oxygen
Explanation: Volume overload with pulmonary oedema requires rapid diuresis and oxygen; oral diuretic is too slow, hypertonic saline worsens overload, dialysis is reserved for refractory cases.
Question 2
A 6‑year‑old child with malaria has a serum sodium of 122 mmol/L, is alert, and has normal skin turgor. Which statement is true?
A. Give hypertonic saline immediately
B. Restrict free water and give isotonic fluids
C. Give a large bolus of normal saline to raise Na⁺ rapidly
D. No fluid therapy is needed
Answer: B. Restrict free water and give isotonic fluids
Explanation: This is euvolaemic hyponatraemia; rapid correction risks cerebral oedema. Gentle isotonic replacement and water restriction are appropriate.
Question 3
A 30‑year‑old man with HIV presents with severe diarrhoea, BP 100/60 mmHg, HR 110 bpm, and urine output 15 ml/h. Serum potassium is 6.2 mmol/L with peaked T waves on ECG. Which intervention should be avoided?
A. IV calcium gluconate
B. IV insulin‑glucose
C. Nebulised β‑agonist
D. Immediate loop diuretic
Answer: D. Immediate loop diuretic
Explanation: The patient is hypovolaemic; diuretics would worsen renal perfusion and potassium retention. Cardiac stabilisation and intracellular shift are priorities.
Question 4
A patient on chronic ACE‑inhibitor therapy develops an acute rise in creatinine from 1.0 to 1.8 mg/dL after starting high‑dose ibuprofen for pain. What is the most appropriate action?
A. Stop ACE‑inhibitor and continue ibuprofen
B. Discontinue ibuprofen and monitor renal function
C. Add a thiazide diuretic
D. Start hypertonic saline
Answer: B. Discontinue ibuprofen and monitor renal function
Explanation: NSAIDs precipitate AKI in patients on ACE‑inhibitors; removing the offending drug allows recovery.
Question 5
A 70‑year‑old man with congestive heart failure is admitted with peripheral oedema and a serum sodium of 148 mmol/L. Which of the following is the best long‑term strategy?
A. Free water restriction only
B. Loop diuretic plus sodium‑restricted diet
C. Hypertonic saline infusion daily
D. High‑dose potassium supplements
Answer: B. Loop diuretic plus sodium‑restricted diet
Explanation: Hypernatraemia in heart failure reflects volume overload; diuretics and dietary sodium restriction correct both fluid excess and sodium concentration.
Drafted with AI assistance from standard references and reviewed for structure. Check details against your lecture notes and the Kenya MoH guideline.