Special Anesthetic Considerations in the Perioperative Period

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  Maintain renal perfusion by maintaining adequate blood pressure.

  
  
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  Administer intravenous (IV) fluid judiciously; maintain adequate perfusion but avoid fluid overload.

  
  
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  Avoid any nephrotoxic drugs and insults.

The various pathophysiological abnormalities and their anesthetic implications are as follows:

1. 
   

   Fluid and electrolytes:

   
   
   
   
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     Hyperkalemia: This is caused by the inability of kidneys to excrete potassium, the majority of which is dependent on renal excretion. It may be aggravated by factors such as drugs (beta-blockers, K⁺ sparing diuretics, angiotensin-converting enzyme [ACE] inhibitors) and extracellular acidosis.

     
     

     Anesthetic implication: All patients should undergo preoperative estimation of serum potassium levels, and if elevated, then ECG should be done. Succinylcholine should be avoided if serum potassium is > 5.5 mEq/L.

     
     
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     Hypokalemia: Hypokalemia poses a patient at risk of arrhythmias. Mild hypokalemia (>3 mEq/L) do not require treatment in most of the cases.

     
     

     Anesthetic implication: Vigilant ECG monitoring (as patients are at risk of arrhythmias), avoid factors which can aggravate hypokalemia (e.g., hyperglycemia, hyperventilation).

     
     
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     Chronic metabolic acidosis: This occurs due to loss of ability to secrete protons and buffers in exchange for bicarbonate. Initially, it is of normal anion gap variety but progresses to high-anion gap variety in advanced renal failure.

     
     

     Anesthetic implication: Acidosis can be precipitated in the perioperative period and should be watched for and avoided.

     
     
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     Sodium and water retention: This is usually mild in nature. It is the cause of hypertension, fluid overload, and pulmonary edema.

     
     

     Anesthetic implications: Perioperative IV fluid administration should be judicious to avoid precipitation of overload and pulmonary edema. Usual fluid intake and urine output should be recorded.

     
     
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     Hypocalcemia: Its causes are as follows:

     
     
     
     
     1. 
        

        Decreased production of vitamin D by kidneys, leading to reduced intestinal absorption of calcium.

        
        
     2. 
        

        Hyperphosphatemia, resulting from impaired renal excretion of phosphates, causes deposition of calcium phosphate in the skin and soft tissues while also inhibiting the renal synthesis of vitamin D.

     
     

     Hypocalcemia and hyperphosphatemia lead to secondary hyperparathyroidism, which results in increased osteoclastic and osteoblastic activity, causing ostetitis fibrosa cystica.

     
     

     Anesthetic implications: Hypocalcemia can cause laryngospasm and hypotension. Therefore, symptomatic hypocalcemia must be treated before surgery. Avoid hyperventilation and alkalosis during the perioperative course, which can aggravate hypocalcemia.

     
     
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     Hypercalcemia: Hypercalcemia manifests as tetany, circumoral numbness, and carpopedal spasm.

     
     

     Anesthetic implications: Maintain hydration and adequate urine output to precipitate hypercalcemia. Anticipate need for higher doses of nondepolarizing muscle relaxants.

     
     
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     Hypermagnesemia: This results from reduced renal excretion of magnesium.

     
     

     Anesthetic implications: It may lead to muscle weakness and potentiation of the action of nondepolarizing muscle relaxants. Acidosis and dehydration can add to hypermagnesemia and must be avoided.

     
     
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     Hypomagnesemia: The causes of hypomagnesemia in chronic renal failure are increased urinary loss and decreased dietary intake.

     
     

     Anesthetic implication: It can cause ventricular arrhythmias and may be associated with refractory hypokalemia as well as hypocalcemia.

   
   
2. 
   

   Cardiovascular manifestations:

   
   
   
   
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     Hypertension: This is caused by sodium and water retention along with hyperreninemia. It leads to left ventricular hypertrophy.

     
     
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     Accelerated atherosclerosis and ischaemic heart disease: This is the result of decreased plasma triglyceride clearance, hypertension, and fluid overload, causing left ventricular hypertrophy and failure.

     
     
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     Metastatic calcific valvular heart disease: This may be a manifestation of hypocalcemia and hyperphosphatemia.

     
     

     Anesthetic implications: Cardiovascular disease (CVD) is a major cause of perioperative morbidity and mortality in CKD patients, necessitating the need for detailed cardiovascular evaluation and optimization preoperatively. Thrombosis of central veins may make cannulation difficult.

   
   
3. 
   

   Hematological abnormalities:

   
   
   
   
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     Anemia: It is a normochromic normocytic in character. It is caused by the following:

     
     
     
     
     1. 
        

        Insufficient erythropoietin production.

        
        
     2. 
        

        Iron deficiency.

        
        
     3. 
        

        Blood retention in the dialyzer.

        
        
     4. 
        

        Gastrointestinal (GI) bleeding.

        
        
     5. 
        

        Reduced red blood cells (RBC) life due to uremia.

     
     

     Anesthetic implication: A transfusion trigger of Hb < 7 g/dL is generally acceptable.

     
     
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     Prolongation of bleeding time: It is caused by the following:

     
     
     
     
     1. 
        

        Decreased activity of platelet factor.

        
        
     2. 
        

        Abnormal platelet aggregation and adhesiveness.

        
        
     3. 
        

        Impaired prothrombin consumption.

     
     

     Anesthetic implications: CKD patients should undergo platelet count, standard coagulation tests, and further qualitative analysis, if required, especially if regional anesthesia is planned. There may be increased bleeding tendency intraoperatively, and it is managed with transfusion of cryoprecipitate, platelets, or desmopressin. Heparin should be avoided during preoperative dialysis to lessen intraoperative bleeding.

   
   
4. 
   

   Pulmonary abnormalities:

   
   
   
   
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     Pulmonary congestion and edema: It occurs primarily due to fluid overload but can occur even in the absence of the latter.

     
     
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     Increased predisposition to atelectasis and infections.

   
   
5. 
   

   Gastrointestinal abnormalities:

   
   
   
   
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     Anorexia, nausea, and vomiting are common.

     
     
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     GI bleeding can be caused by uremia.

     
     
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     Delayed gastric emptying, decreased residual volume, and decreased pH lead to increased risk of peptic ulcer disease and aspiration.

     
     

     Anesthetic implication: Increased risk of aspiration should be managed with aspiration prophylaxis and rapid sequence induction and intubation.

   
   
6. 
   

   Immune system dysfunction:

   
   
   
   
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     Uremic immune dysfunction: It is caused by inhibition of cell-mediated immunity and humoral defense mechanisms.

     
     

     Anesthetic implication: Catheter and fistula site infections are common.

   
   
7. 
   

   Neurological manifestations:

   
   
   
   
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     Uremic encephalopathy.

     
     
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     Peripheral neuropathy: Distal glove-and-stocking sensory loss, progressing to motor loss.

     
     
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     Autonomic neuropathy.

     
     
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     Dialysis dementia: It is caused by aluminum toxicity from the dialysate.

     
     
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     Dialysis disequilibrium syndrome: It is caused by a reverse urea effect at the start of dialysis.

     
     

     Anesthetic implication: Caution with regional anesthesia in case of documented peripheral neuropathy.

   
   
8. 
   

   Endocrine disturbances:

   
   
   
   
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     Temperature regulation is altered.

     
     

     Anesthetic implication: Patients are prone to hypothermia intraoperatively.