Fluid management in renal failure

Surgical approach (context-dependent)

• Not a single operation: principles apply across surgery (major abdominal/vascular/orthopaedic), interventional radiology, and renal replacement therapy access procedures.
• Typical surgical priorities that drive fluid decisions
  • Haemostasis and avoidance of hypotension (bleeding control, clamp time, tourniquet use).
  • Minimise tissue oedema (anastomoses, bowel handling) and avoid abdominal compartment syndrome in large-volume resuscitation.
  • Use of contrast (angiography/CT) and nephrotoxic exposures (antibiotics, NSAIDs) in peri-operative pathway.
  • If dialysis access surgery: AVF/AVG creation or tunneled line insertion—usually short, low fluid requirement; avoid hypotension compromising fistula flow.

Anaesthetic management (typical patterns; tailor to case)

• Type of anaesthesia
  • GA common for major surgery; regional/neuraxial feasible but consider anticoagulation (dialysis), platelet dysfunction (uraemia), and haemodynamic effects.
• Airway
  • ETT for major surgery/aspiration risk; SGA may be appropriate for short minor procedures (e.g., access surgery) if aspiration risk low.
• Duration
  • Procedure-dependent: access surgery ~0.5–2 h; major abdominal/vascular often 2–6+ h.
• How painful
  • Access surgery: mild–moderate; major abdominal/orthopaedic: moderate–severe—plan multimodal analgesia avoiding nephrotoxins (NSAIDs) and dose-adjust opioids.
• Monitoring focus
  • Aim: maintain renal perfusion pressure and avoid fluid overload—consider arterial line, frequent blood gases/electrolytes, strict fluid balance, and dynamic assessment of responsiveness.

Definitions and classification relevant to fluids

• Renal failure spectrum
  • AKI: abrupt decline in kidney function (KDIGO: creatinine rise and/or oliguria).
  • CKD: eGFR <60 for ≥3 months and/or markers of kidney damage; ESKD: dialysis-dependent or transplant candidate.
• Why fluid management is different
  • Reduced ability to excrete sodium/water → pulmonary oedema risk.
  • Impaired potassium and acid excretion → hyperkalaemia and metabolic acidosis.
  • Altered drug handling and haemodynamics (anaemia, autonomic dysfunction, LVH, diastolic dysfunction).

Goals of peri-operative fluid therapy in renal failure

• Primary goals
  • Maintain effective circulating volume and organ perfusion (especially renal perfusion) while avoiding fluid overload.
  • Avoid hypotension and large swings in MAP; consider individualised MAP targets (e.g., chronic hypertension).
  • Prevent/treat electrolyte and acid–base derangements (K+, Na+, bicarbonate).
  • Minimise iatrogenic kidney injury: avoid nephrotoxins, contrast load, and chloride-rich over-resuscitation.
• Targets (pragmatic, case-dependent)
  • Urine output: interpret cautiously—oliguria may reflect CKD/ESKD or anaesthesia; do not chase with fluid blindly.
  • Haemodynamics: maintain MAP adequate for perfusion; use vasopressors early if euvolaemic.
  • Fluid balance: aim neutral to slightly negative post-op in those prone to overload; daily weights helpful.

Pre-operative assessment (what to ask and check)

• History and functional status
  • Baseline renal function, trend in creatinine/eGFR, urine output, cause of renal failure.
  • Dialysis: modality (HD/PD), schedule, last session, usual ultrafiltration, target weight, intradialytic hypotension.
  • Fluid status symptoms: orthopnoea, PND, peripheral oedema; exercise tolerance; heart failure history.
• Examination and bedside tests
  • Volume assessment: JVP, lung crepitations, oedema; consider ultrasound (IVC, lung B-lines) if available.
  • BP profile: chronic hypertension implies right-shifted autoregulation—avoid low MAP.
• Investigations
  • U&E, bicarbonate, K+, Ca2+/PO4, Mg2+; FBC (anaemia), coagulation if uraemia/anticoagulation; ABG/VBG if unwell.
  • ECG for hyperkalaemia changes; CXR if fluid overload suspected; echo if significant cardiac disease.
• Medication review (fluid/electrolyte relevant)
  • ACEi/ARB: risk of refractory hypotension and AKI; often withheld on day of surgery for major cases (local policy).
  • Diuretics: may be withheld if hypovolaemic; continue if congested (individualise).
  • Potassium binders, bicarbonate, phosphate binders; anticoagulation (heparin during HD), antiplatelets.
  • Avoid NSAIDs; adjust doses of opioids/antibiotics.

Choice of IV fluids in renal failure

• Crystalloids: general principles
  • Prefer balanced crystalloids (lower chloride) for large-volume resuscitation to reduce hyperchloraemic acidosis and renal vasoconstriction risk.
  • 0.9% saline: useful in hypochloraemic metabolic alkalosis or hyponatraemia with hypovolaemia; avoid large volumes (hyperchloraemia, acidosis, oedema).
  • Hartmann’s/Plasma-Lyte: contain small K+ (typically 4–5 mmol/L) but do not usually cause hyperkalaemia; overall effect often less acidotic than saline.
• Glucose-containing fluids
  • Use for maintenance if needed (e.g., 5% glucose) but beware hyponatraemia and fluid overload; reduce rates in oliguric/anuric patients.
  • In ESKD, maintenance fluids often minimal; focus on replacing measured losses and drug carriers.
• Colloids and albumin
  • Synthetic starches: avoid (associated with AKI and need for RRT in critical illness).
  • Albumin: may be considered in selected patients (e.g., cirrhosis, hypoalbuminaemia) but not routine; still risk of overload and cost.
• Blood products
  • Use for haemorrhage/anaemia; avoid unnecessary transfusion (volume, potassium load, sensitisation in transplant candidates).

Maintenance vs replacement vs resuscitation (practical approach)

• Maintenance
  • Oliguric/anuric renal failure: avoid routine maintenance infusions; give only what is required for medications and measured losses.
  • If some urine output and not overloaded: use low-volume maintenance; monitor Na+ and glucose closely.
• Replacement
  • Replace measured losses (NG, drains, fistula output) with appropriate fluid; consider electrolyte composition of losses.
  • GI losses often chloride-rich → saline may be appropriate in small volumes; reassess frequently.
• Resuscitation
  • Treat shock promptly; give small boluses (e.g., 250 mL) with reassessment; avoid “litres by default”.
  • If not fluid responsive or signs of overload: early vasopressor (e.g., noradrenaline) rather than further fluid.

Assessing volume status and fluid responsiveness

• Clinical and basic monitoring
  • Trends: HR, BP, capillary refill, mental state, lactate, skin temperature; strict input/output and daily weights.
  • Urine output is unreliable as a sole target in CKD/ESKD and under anaesthesia; interpret in context.
• Dynamic tests (preferred over static filling pressures)
  • Passive leg raise with real-time stroke volume/CO measurement (echo, oesophageal Doppler, pulse contour).
  • SVV/PPV in controlled ventilation with regular rhythm and adequate tidal volumes; limitations in open chest, arrhythmias, low VT.
  • Bedside echo: LV filling, RV function, IVC variation (limited), lung ultrasound for B-lines.
• Central venous pressure
  • Poor predictor of fluid responsiveness; may help identify extreme states and guide trends with other data.

Electrolyte and acid–base issues that drive fluid choice

• Hyperkalaemia
  • Common in AKI/ESKD; worsened by acidosis, tissue injury, transfusion, suxamethonium, ACEi/ARB, K-sparing diuretics.
  • Fluids: balanced crystalloids contain small K+ but often safer than saline-induced acidosis; avoid potassium-containing maintenance solutions if K+ high and rising.
• Metabolic acidosis
  • Hyperchloraemic acidosis from large-volume 0.9% saline can worsen K+ and haemodynamics; prefer balanced solutions when possible.
  • Bicarbonate therapy: consider in severe acidaemia with haemodynamic compromise or life-threatening hyperkalaemia; definitive treatment may be dialysis.
• Sodium and water balance
  • Hyponatraemia: avoid hypotonic excess; correct slowly; treat symptomatic severe cases with hypertonic saline under specialist guidance.
  • Fluid overload: pulmonary oedema risk; consider diuretics if responsive, CPAP/ventilation, and urgent dialysis/UF if refractory.

Dialysis and peri-operative fluid planning

• Timing of haemodialysis (HD)
  • Elective surgery often best the day after dialysis (optimise volume, K+, acid–base) while allowing time for heparin effect to wear off (institution-dependent).
  • If urgent surgery and hyperkalaemia/overload/acidosis: consider urgent dialysis pre-op if feasible.
• Intra-operative considerations in ESKD
  • Aim to maintain perfusion without fluid loading; use vasopressors/inotropes as needed.
  • Avoid venepuncture/BP cuff on AV fistula arm; protect access.
• Peritoneal dialysis (PD)
  • Consider aspiration risk if abdomen full; coordinate drainage pre-op; watch for glucose load and fluid shifts.

AKI prevention and management: fluid-related bundle

• Preventive measures
  • Avoid hypotension: maintain MAP; treat promptly; consider higher MAP targets in chronic hypertensives.
  • Avoid nephrotoxins: NSAIDs, aminoglycosides (if alternatives), excess contrast; adjust drug doses.
  • Optimise sepsis management: early antibiotics, source control, balanced resuscitation, vasopressors.
• Oliguria intra-operatively
  • Check simple causes: catheter kinking/obstruction, surgical factors (clamps), haemodynamics, anaesthetic depth.
  • Assess fluid responsiveness before giving bolus; consider vasopressor if hypotensive and not fluid responsive.
  • Diuretics: not for “renal protection”; may help treat overload in patients with residual function.

Special situations

• Rhabdomyolysis / crush injury
  • Early aggressive fluid in initial phase to maintain renal perfusion and dilute myoglobin (often before established renal failure); once oliguric/anuric, avoid overload and consider RRT.
• Contrast exposure
  • Hydration reduces risk in susceptible patients; balance against overload—individualise and consider haemodynamic optimisation rather than fixed-volume protocols.
• Post-obstructive diuresis
  • After relief of obstruction: high urine output with salt/water loss; replace carefully (often 50–75% of output) and monitor electrolytes.

Post-operative management

• Monitoring
  • Strict fluid balance, daily weight, serial U&E/acid–base; watch for pulmonary oedema and hyperkalaemia.
• When to involve renal team / consider RRT
  • Refractory hyperkalaemia, severe acidosis, pulmonary oedema/overload, uraemic complications, or progressive AKI with complications.