General Anaesthesia in Elderly Patients with Renal Impairment
Elderly patients with renal impairment require mandatory dose reduction of anaesthetic agents, routine renal function assessment using creatinine clearance calculations (not serum creatinine alone), and careful avoidance of nephrotoxic drugs to prevent perioperative morbidity and mortality. 1
Pre-operative Renal Function Assessment
Calculate creatinine clearance using the Cockcroft-Gault equation rather than relying on serum creatinine alone, as serum creatinine significantly underestimates renal impairment in elderly patients due to decreased muscle mass—renal function may have declined by 40% by age 70 while serum creatinine remains falsely "normal." 2, 3
Renal function declines by approximately 1% per year after age 40, with considerable variation related to nephrotoxic effects of comorbidities (hypertension, diabetes) and drugs (particularly NSAIDs and ACE inhibitors). 1, 3
Renal function directly affects the pharmacokinetics and pharmacodynamics of anaesthetic drugs and therefore must be assessed routinely before surgery. 1
Anaesthetic Drug Selection and Dosing
Induction Agents
Reduce initial doses of hypnotic agents by 25-50% in elderly patients with renal impairment, as age-related alterations in pharmacokinetic and pharmacodynamic profiles render older patients sensitive to relative overdose, resulting in myocardial depression, reduced blood pressure homeostasis, and delayed recovery. 1, 4
The dose required to induce anaesthesia is lower in elderly patients, and the onset time is longer—depth of anaesthesia monitoring is recommended. 1
Maintenance Agents
Sevoflurane and propofol appear to have different effects on renal function during anaesthesia: sevoflurane reduces urine output and sodium excretion and increases plasma renin compared with propofol, though the clinical significance for acute kidney injury requires further investigation. 5
Sevoflurane anesthesia at low or high fresh gas flow rates is probably no more injurious to the kidneys than other commonly used maintenance agents. 6
Neuromuscular Blocking Agents
Cisatracurium is preferred in patients with renal impairment as it undergoes Hofmann elimination and does not require dose adjustment, though slower onset times may necessitate extending the interval between drug administration and intubation attempt. 7
Rocuronium in patients with renal failure demonstrates clinical durations similar to but somewhat more variable than subjects with normal renal function, though individualization of dose is required. 8
Regional vs. General Anaesthesia
The choice between regional and general anaesthesia is less important than how sympathetically either is administered with regard to the patient's pathophysiological status—observational studies and meta-analyses do not reliably show significant differences in outcome. 1
Regional anaesthesia with minimal/no sedation may offer benefits in avoiding short-term morbidities including hypotension, delirium, cardiorespiratory complications, and need for opioid analgesia, though patients with cognitive dysfunction may not comply without heavy sedation. 1
Thoracic epidural anesthesia and postoperative analgesia are associated with decreased incidence of renal failure in patients undergoing coronary artery bypass grafting. 6
Intraoperative Management
Positioning and Pressure Care
Elderly patients are at higher risk of preventable peripheral nerve injuries during prolonged surgery—probable sites of nerve injury should be comprehensively padded before surgery and assessed routinely every 30 minutes throughout. 1
Reduced skin depth and vascularity, together with reduced muscle mass, predispose older patients to preventable tissue pressure necrosis, usually over bony protuberances—prolonged hypotension may contribute to pressure sore development. 1
Fluid Management
Monitor for fluid retention and electrolyte disturbances closely, as elderly patients with renal impairment are prone to volume overload and should have hydration status assessed and optimized before and during therapy. 2
Appropriate fluid therapy, combined with positioning and antithrombotic measures, reduces the risk of perioperative thromboembolism in the elderly. 1
Monitoring Requirements
Complete an end-of-surgery checklist before the patient leaves the operating theatre, including assessment of core temperature, haemoglobin concentration, and confirmation of age-adjusted and renal function-adjusted medication doses. 1
Renal function monitoring every 48-72 hours is recommended during acute illness, as elderly patients' kidney function can deteriorate rapidly. 2
Medication Avoidance
Avoid nephrotoxic medications that could worsen renal function, particularly NSAIDs, COX-2 inhibitors, and drugs that precipitate delirium (benzodiazepines, antihistamines including cyclizine, atropine, sedative hypnotics). 1, 2
Chronic treatment with ACE inhibitors is associated with increased incidence of postoperative renal impairment in patients undergoing elective aortic surgery. 6
Postoperative Analgesia
Paracetamol is safe and should be considered first-line therapy for postoperative pain in elderly patients with renal impairment. 1
NSAIDs should be used with caution at lowest doses and shortest duration, with proton pump inhibitor gastric protection and routine monitoring for gastric and renal damage. 1
Morphine should be administered cautiously, particularly to patients with poor renal function, with consideration for co-administration of laxatives and anti-emetics as required. 1
Critical Pitfalls to Avoid
Never rely on serum creatinine alone to assess renal function in elderly patients—it significantly underestimates impairment due to reduced muscle mass. 2, 3
Do not use standard adult doses of anaesthetic agents without adjustment for both age and renal function—this leads to relative overdose and complications. 1, 4
Avoid co-prescribing multiple nephrotoxic agents (NSAIDs with ACE inhibitors, for example) that could precipitate acute-on-chronic renal failure. 1, 2
Extend the time interval between drug administration and intubation in elderly patients with renal dysfunction, as slower onset times are expected. 7