What is the recommended use of chlorhexidine (CHG) baths for patients at high risk of developing infections, particularly those with compromised immune systems, open wounds, or undergoing surgery?

Pathophysiology of Chlorhexidine Baths

Mechanism of Antimicrobial Action

Chlorhexidine gluconate (CHG) works by disrupting bacterial cell membranes through its cationic (positively charged) bisdiguanide structure, which binds to negatively charged bacterial cell walls, causing membrane disruption, leakage of intracellular components, and ultimately bacterial death. 1

• CHG demonstrates broad-spectrum antimicrobial activity against gram-positive bacteria (including MRSA), gram-negative bacteria (including VRE and Pseudomonas), and fungi, with particularly strong activity against skin colonizing flora 2
• The antiseptic achieves a >5-log reduction in bacterial counts within 1 minute of exposure to 0.05% CHG concentration 2
• Concentration-dependent antimicrobial effect: 2% CHG solution (used for bathing) provides sustained antimicrobial activity, while 4% concentration is reserved for surgical hand scrubs 1, 3

Residual and Persistent Activity

The key advantage of chlorhexidine over other antiseptics is its substantial residual antimicrobial activity that persists on the skin for hours after application, providing ongoing protection against bacterial recolonization. 1

• CHG binds to the stratum corneum of skin, creating a persistent antimicrobial layer that continues killing bacteria long after the initial application 1
• This residual effect distinguishes CHG from alcohol-based products, which have no persistent activity after evaporation 4
• Mechanical friction during application enhances antimicrobial activity by improving CHG penetration into skin layers and disrupting biofilms 1

Impact on Skin Microbiome and Colonization

Daily CHG bathing reduces skin bacterial burden by 2.5 log10 colony-forming units, specifically targeting multidrug-resistant organisms while maintaining this reduction throughout the ICU stay. 4

• VRE colonization decreases from 26 to 9 colonizations per 1,000 patient-days (risk ratio 0.4,95% CI 0.1-0.9) with CHG bathing 4
• Environmental contamination reduction: CHG bathing decreases VRE contamination on healthcare workers' hands by 40% (RR 0.6) and on environmental surfaces by 70% (RR 0.3) 4
• The antimicrobial effect extends beyond the patient to create a zone of protection that reduces transmission pathways 4

Clinical Outcomes: Infection Prevention

In a multicenter trial of 7,727 ICU patients, daily CHG bathing reduced multidrug-resistant organism acquisition by 23% (5.10 vs 6.60 cases per 1,000 patient-days, P=0.03) and hospital-acquired bloodstream infections by 28% (4.78 vs 6.60 cases per 1,000 patient-days, P=0.007). 4, 1

• Central line-associated bloodstream infections decrease from 10.4 to 4.1 infections per 1,000 patient-days with CHG bathing compared to soap and water 4
• CHG demonstrates effectiveness against both gram-positive bacteremias and CVC-related fungemia, providing broader protection than initially recognized 4
• The infection reduction occurs through multiple mechanisms: direct bacterial killing, prevention of catheter colonization, and reduction in environmental contamination 4

Important Caveats and Safety Considerations

CHG must be kept away from eyes, ears, and mucous membranes due to risk of severe corneal damage, conjunctivitis, and ototoxicity when it contacts the middle ear through perforated eardrums. 1, 3

• Concentration matters for safety: 2% CHG solution for bathing minimizes skin irritation risk compared to 4% formulations used for hand hygiene 1
• Avoid soap interference: Regular soap immediately before or after CHG application reduces its antimicrobial activity and should be avoided 1
• Allergy alert: CHG can cause severe allergic reactions including wheezing, shock, facial swelling, hives, and rash; if these occur, discontinue immediately 3
• Age restriction: Only use in patients over 2 months of age 1

Limitations in Surgical Site Infection Prevention

Despite its effectiveness for ICU-acquired infections, preoperative CHG bathing shows no clear benefit for preventing surgical site infections when used as a single preoperative shower or bath. 5, 6, 7

• A meta-analysis of 16 trials (17,932 patients) found no statistically significant reduction in SSI with preoperative CHG bathing (RR 0.90,95% CI 0.77-1.05, P=0.19) 5
• The Cochrane review of 10,157 patients similarly found no evidence of benefit for preoperative CHG showering over other wash products (RR 0.91,95% CI 0.80-1.04) 6
• This discrepancy likely reflects the difference between single-dose exposure (preoperative bathing) versus repeated daily application (ICU protocol) needed to achieve sustained skin decolonization 5, 6