What is the cause of and how to manage a female hemodialysis (HD) patient's 'mmm' sound while sleeping during dialysis, with no evidence of obstructive sleep apnea (OSA), snoring, or airway difficulties?

Management of "Mmm" Sounds During Dialysis Sleep

This patient is likely experiencing catathrenia (nocturnal groaning), a benign sleep-related breathing disorder distinct from obstructive sleep apnea, which requires no specific treatment but warrants assessment for underlying sleep disturbances common in hemodialysis patients.

Understanding the Clinical Presentation

The "mmm" sound during sleep in a hemodialysis patient without OSA, snoring, or airway difficulties most likely represents:

• Catathrenia (sleep groaning): A benign parasomnia characterized by prolonged expiratory groaning sounds during sleep, typically occurring during REM sleep without associated oxygen desaturation or arousal 1
• Not pathological sleep apnea: The absence of snoring, airway difficulties, and OSA features distinguishes this from obstructive or central sleep apnea syndromes that affect 34-37% of dialysis patients 2

Systematic Assessment Approach

Evaluate Dialysis Adequacy First

Before attributing symptoms to primary sleep disorders, ensure adequate dialysis delivery:

• Calculate Kt/V targeting spKt/V ≥1.3 per session to assess whether uremic symptoms are contributing to sleep disturbances 3
• Verify dialysis frequency: Confirm patient receives at least 3 sessions weekly for minimum 3 hours each, as inadequate dialysis drives uremic symptoms including sleep disorders 3
• Consider extended dialysis (4-6 times weekly) if sleep disturbances persist despite standard thrice-weekly treatment 3

Screen for Concurrent Sleep-Disrupting Conditions

Sleep disorders affect up to 60% of dialysis patients and significantly impact mortality 4:

• Apply Pittsburgh Sleep Quality Index (PSQI): Scores ≥5 indicate poor sleep quality, present in 65-83% of dialysis patients 3
• Assess for uremic pruritus: Affects up to 40% of dialysis patients and significantly disrupts sleep 4, 2
• Screen for depression: Prevalence of 22.8% in dialysis patients; both cause and consequence of sleep disturbance 4, 2
• Evaluate for restless legs syndrome and pain: These directly impair sleep quality 3

Assess Fluid Status and Hemodynamic Stability

Fluid overload commonly causes respiratory disturbances in ESRD patients:

• Examine for signs of volume overload: Peripheral edema, abnormal lung sounds, elevated jugular venous pressure 2
• Implement strict sodium restriction (100 mmol/day) and appropriate ultrafiltration to achieve dry weight, as fluid overload directly contributes to sleep-related breathing abnormalities 2
• Minimize intradialytic hypotension: Episodes of volume depletion during HD contribute to more rapid loss of residual kidney function and patient discomfort 5

Management Strategy

If Sleep Quality is Impaired Despite Benign Groaning

First-line pharmacologic intervention:

• Gabapentin 100-300 mg after each dialysis session is the preferred medication with proven efficacy and favorable safety profile in dialysis patients 4, 3, 2
• Maximum daily dose should not exceed 200-300 mg in ESRD due to renal elimination 3

Non-pharmacologic interventions:

• Implement sleep hygiene measures: Consistent 7-8 hour sleep schedule, dark quiet environment, leg elevation 2-3 hours before bed to reduce fluid redistribution 2
• Prescribe cognitive behavioral therapy (CBT) when available, as it has proven efficacy in reducing depression and improving sleep in dialysis patients 3
• Aerobic exercise programs decrease depressive symptoms and may improve sleep quality 3

If No Sleep Quality Impairment

Reassurance and monitoring:

• Catathrenia itself requires no treatment if the patient reports feeling refreshed upon waking and has no daytime symptoms 1
• Educate patient and family that groaning sounds are benign and not associated with oxygen desaturation or health risks
• Monitor at each dialysis visit using standardized tools like PSQI to detect any deterioration in sleep quality 3, 2

Monitoring and Follow-Up

• Evaluate sleep quality and medication efficacy at each dialysis visit using PSQI or similar validated tools 3, 2
• Monitor specifically for morning drowsiness, cognitive impairment, and falls risk if gabapentin is initiated 3
• Reassess fluid status regularly, as poor fluid control independently associates with decreased quality of life and contributes to sleep disturbances 2

Red Flags Requiring Urgent Escalation

Escalate care immediately if the patient develops:

• Altered mental status or confusion suggesting uremic encephalopathy 3
• Oxygen desaturation or respiratory distress indicating true sleep apnea or pulmonary edema 2
• Severe electrolyte abnormalities or volume overload refractory to current dialysis prescription 3

Common Pitfalls to Avoid

• Do not assume all nocturnal sounds represent pathological sleep apnea: Catathrenia is benign and distinct from OSA 1
• Do not rely solely on serum creatinine or urea nitrogen to assess adequacy: Use validated Kt/V calculations or measured clearances 3
• Avoid long-acting benzodiazepines due to accumulation risk and worsening cognitive function in patients already at risk for uremic encephalopathy 3
• Do not use sedating antihistamines long-term due to limited efficacy and increased dementia risk 3