What causes chills in a patient undergoing hemodialysis (HD)?

Chills During Hemodialysis: Causes and Clinical Approach

Chills during hemodialysis are most commonly caused by bacterial contamination of dialysate water or catheter-related bloodstream infections, with 60% of hemodialysis patients presenting with chills having a documented infection. 1

Primary Causes of Chills During HD

Water Quality and Pyrogenic Reactions

• Bacterial contamination and endotoxin exposure from dialysis water is a critical cause of chills and fever during HD, with short-term exposure to high levels of bacteria and endotoxin causing pyrogenic reactions ranging from chills and fever to septicemia with severe hypotension and shock. 2
• Contaminated heparinized saline solutions can cause pyrogenic reactions, with documented bacterial counts of 7.4 × 10⁵/ml and endotoxin levels of 1,300 ng/ml leading to chills in 75% of affected patients, with mean onset 1.1 hours after starting dialysis. 3
• Monthly microbial testing of dialysis water is mandatory, and if bacterial or endotoxin levels exceed action levels, the medical director must decide whether it is safe to continue dialyzing patients. 2

Catheter-Related Bloodstream Infections

• Among hemodialysis patients with chills, 33.5% have bacteremia and 60.2% have any type of infection, making infection the dominant concern when chills occur during or after dialysis. 1
• Vascular catheter as dialysis access is the strongest risk factor for bacteremia (OR 6.2; 95% CI, 3.2-12.0), followed by fever (OR 1.6; 95% CI, 1.1-2.3). 1
• Patients with tunneled hemodialysis catheters experiencing chills should have the infected catheter removed for CRBSI due to S. aureus, Pseudomonas species, or Candida species, with a temporary catheter inserted into another anatomical site. 2

Temperature Dysregulation

• Standard dialysate temperature (37-38°C) can paradoxically increase core body temperature during HD, leading to cutaneous vasodilation and potential cardiovascular instability, which may manifest as chills when combined with rapid temperature changes. 4
• Lowering dialysate temperature to 34-35.5°C improves cardiovascular stability and prevents the deleterious cycle of temperature elevation, though excessively low temperatures can trigger shivering and chills (only 0.3-0.8°C separates vasodilation threshold from shivering threshold). 4
• Isothermic dialysis (maintaining predialysis body temperature unchanged) reduces intradialytic morbid events by 25% compared to standard temperature dialysis, preventing both hypotension and temperature-related symptoms including chills. 2

Clinical Decision Algorithm

Immediate Assessment When Chills Occur

• Check for fever, leukocytosis, and vascular access type immediately, as these determine infection risk stratification. 1
• Obtain blood cultures from peripheral vessels not intended for future fistula creation before initiating antibiotics. 2
• Inspect dialysis water quality records and consider pyrogenic reaction if multiple patients affected simultaneously. 2

Risk Stratification for Infection

Low-risk patients (6% bacteremia rate): Fistula or graft access + no fever + normal leukocyte count + normal albumin + no obvious infection source—these patients may be investigated without prompt antibiotic treatment. 1

High-risk patients (require immediate antibiotics): Catheter access OR fever OR leukocytosis OR hypoalbuminemia OR obvious infection source—empirical therapy should include vancomycin plus gram-negative coverage based on local antibiogram (third-generation cephalosporin, carbapenem, or β-lactam/β-lactamase combination). 2, 1

Addressing Non-Infectious Causes

• Review dialysate temperature settings and consider reducing to 35-35.5°C if chills occur without infection, particularly in patients with recurrent intradialytic hypotension. 2, 4
• Verify monthly water quality testing results and ensure bacterial counts <200 CFU/mL and endotoxin levels <2 EU/mL per AAMI standards. 2
• Assess ultrafiltration rate, as excessive fluid removal increases metabolic rate and alters thermal balance, potentially contributing to chills. 5

Critical Pitfalls to Avoid

• Never dismiss chills as benign in catheter patients—the infection rate approaches 60% and bacteremia rate is 33.5%, with catheter access conferring 6-fold increased bacteremia risk. 1
• Do not delay blood cultures while waiting for fever to develop, as chills alone predict infection in the majority of cases. 1
• Avoid using procalcitonin to rule out infection in hemodialysis patients, as it has only 77% sensitivity and 59% specificity at cutoff ≥1 ng/mL, making it unreliable for clinical decision-making in this population. 6
• Do not attribute chills solely to "cold dialysate" without investigating infection, as this delays appropriate antibiotic therapy in high-risk patients. 1
• Ensure hand hygiene observation, vascular access care observation, alcohol-based chlorhexidine at exit sites, and catheter hub disinfection are consistently performed, as these measures reduce catheter-related BSI risk. 2