Managing Diastolic Dysfunction as a Cause of Weaning Failure in Critically Ill Older Adults
Diastolic dysfunction is a major, often overlooked cause of weaning failure in critically ill older adults, and echocardiography should be performed to assess cardiac function when patients fail spontaneous breathing trials, with treatment focused on rate control, preload optimization, and avoidance of excessive fluid administration. 1, 2, 3
Initial Recognition and Diagnostic Approach
When to Suspect Cardiac-Related Weaning Failure
Echocardiography is specifically recommended to determine the cause of failure to wean from mechanical ventilation, particularly when clinical and laboratory clues are ambiguous. 1 The assessment should occur early—ideally within 10 minutes of starting a spontaneous breathing trial (SBT)—as this timing is sufficient to detect diastolic dysfunction that predicts weaning failure. 2
Key indicators that diastolic dysfunction may be causing weaning failure include:
- Failure of SBT despite adequate respiratory mechanics (RSBI ≤105 breaths/min/L, adequate oxygenation) 4
- Development of tachycardia, hypertension, or disproportionate dyspnea during weaning attempts 1
- Presence of multiple cardiac comorbidities (hypertension, coronary disease, atrial fibrillation) common in older adults 1
Echocardiographic Assessment
The E/e' ratio is the most robust predictor of weaning failure related to diastolic dysfunction, with patients who fail weaning demonstrating significantly higher E/e' ratios (mean difference 2.65) compared to those who succeed. 3, 5 This parameter can be assessed even in patients with atrial fibrillation, making it particularly valuable in older adults. 2
Specific echocardiographic findings associated with weaning failure:
- E/e' ratio >15 strongly predicts weaning failure and indicates elevated left ventricular filling pressures 2, 6
- Reduced e' wave velocity (indicating impaired diastolic relaxation) 3
- Elevated E wave velocity (indicating increased filling pressures) 3
- Importantly, left ventricular ejection fraction (LVEF) is NOT predictive of weaning failure—patients with preserved LVEF can still fail due to isolated diastolic dysfunction 3, 5, 6
Transthoracic echocardiography should be the initial imaging modality; transesophageal echocardiography is indicated only when transthoracic studies are non-diagnostic or in intubated patients where adequate windows cannot be obtained. 1
Physiological Stress Testing During Weaning
Physiological stress echocardiography (targeted echocardiography during a weaning trial) can reveal dynamic diastolic dysfunction that is not apparent at rest. 1 However, this may be limited by tachycardia, tachypnea, and patient agitation. 1
In patients with preserved systolic function at rest who fail weaning:
- Dobutamine stress echocardiography can unmask latent diastolic dysfunction, showing increased E/e' ratios (from ~7 to ~16) and deterioration of strain parameters during stress 6
- Ephedrine stress testing can reveal dynamic functional mitral regurgitation that worsens with increased afterload, contributing to weaning failure 6
Treatment Strategy for Diastolic Dysfunction During Weaning
Rate Control and Rhythm Management
Beta-blockade to lower heart rate and increase the diastolic filling period is a primary therapeutic intervention for diastolic dysfunction. 1 In older adults with multiple comorbidities:
- Target heart rate <100-110 bpm to maximize diastolic filling time 1
- Restoration of atrioventricular synchrony may significantly enhance cardiac output—prompt cardioversion of atrial fibrillation or treatment of bradyarrhythmias should be considered in hemodynamically unstable patients 1
- Verapamil-type calcium antagonists may be used for rate control and to improve diastolic relaxation, though beta-blockers are generally preferred 1
Preload Optimization
Diuretics are necessary when fluid overload is present but must be used cautiously to avoid excessive preload reduction that decreases stroke volume and cardiac output. 1
The approach to volume management:
- Assess volume status with inferior vena cava diameter and respiratory variation on echocardiography 1
- In mechanically ventilated patients with diastolic dysfunction, target euvolemia rather than aggressive diuresis 1
- Small hyperdynamic ventricles with reduced end-diastolic area suggest hypovolemia and potential volume responsiveness, but this technique should only be applied in patients with normal LV function 1
Afterload Management
ACE inhibitors may improve diastolic relaxation and cardiac distensibility directly, have long-term effects through regression of hypertrophy, and reduce hypertension. 1 In older adults:
- Initiate with low doses due to greater likelihood of hypotension and delayed excretion 1
- Monitor supine and standing blood pressure, renal function, and serum potassium levels 1
- Treatment can be introduced in the outpatient setting with appropriate precautions 1
Inotropic Support Considerations
Milrinone, a phosphodiesterase-3 inhibitor, improves diastolic function as evidenced by improvements in left ventricular diastolic relaxation, in addition to its inotropic effects. 7 This may be particularly useful in patients with combined systolic and diastolic dysfunction who fail weaning despite optimization of other parameters.
Dosing considerations for older adults with renal impairment (common in this population):
- Loading dose: 50 mcg/kg over 10 minutes 7
- Maintenance infusion: 0.375-0.75 mcg/kg/min, adjusted for creatinine clearance 7
- For creatinine clearance 30 mL/min, reduce infusion rate to 0.33 mcg/kg/min; for clearance 10 mL/min, reduce to 0.23 mcg/kg/min 7
- Monitor for ventricular arrhythmias (reported in 12.1% of patients), hypotension (2.9%), and hypokalemia 7
Weaning Protocol Modifications for Diastolic Dysfunction
Spontaneous Breathing Trial Parameters
Initial SBT should be conducted with modest inspiratory pressure augmentation (5-8 cm H₂O) rather than T-piece, as pressure augmentation trials are more likely to be successful. 4
Specific SBT parameters for patients with suspected diastolic dysfunction:
- PEEP ≤5 cm H₂O 4
- FiO₂ ≤40% 4
- Monitor for signs of cardiac decompensation: heart rate >140 bpm or sustained increase >20%, systolic BP >180 or <90 mmHg, increased anxiety or diaphoresis 4
Most SBT failures occur within the first 30 minutes, but echocardiographic changes indicating diastolic dysfunction can be detected as early as 10 minutes into the trial. 4, 2
Post-Extubation Strategy
For high-risk older adults with cardiac comorbidities, prophylactic noninvasive ventilation (NIV) immediately after extubation reduces reintubation rates and mortality. 8 This is distinct from rescue NIV after respiratory failure develops, which may increase mortality. 8
NIV protocol for high-risk patients:
- Initiate immediately post-extubation with IPAP 10-12 cm H₂O and EPAP 5-10 cm H₂O 8
- Target SpO₂ 88-92% (particularly important in patients with concurrent COPD) 8
- Prophylactic NIV is beneficial; rescue NIV after respiratory distress develops is potentially harmful 8
Respiratory Muscle Training and Rehabilitation
Inspiratory muscle training (IMT) at moderate intensity (approximately 50% of maximal inspiratory pressure) significantly improves weaning success in patients with weaning failure, with 76% of the training group successfully weaned compared to 35% in sham groups. 1
Implementation strategy:
- Begin IMT sessions at 30-50% of maximal inspiratory pressure for 30 minutes daily 1
- Early mobilization and physical activity should be prioritized, as transferring patients to respiratory ICUs with dedicated rehabilitation teams increases ambulation rates threefold 1
- Multimodality chest physiotherapy including manual hyperinflation with suctioning (maintaining pressures <40 cmH₂O) enhances weaning success 9
Common Pitfalls and Contraindications
Critical Errors to Avoid
Do not assume normal LVEF excludes cardiac causes of weaning failure—isolated diastolic dysfunction with preserved ejection fraction is a major cause of weaning failure in older adults 3, 5, 6
Do not use NIV as rescue therapy after extubation failure develops—this approach may increase ICU mortality; NIV must be initiated prophylactically immediately post-extubation in high-risk patients 8
Do not aggressively diurese patients with diastolic dysfunction without echocardiographic guidance—excessive preload reduction can paradoxically worsen cardiac output in patients with stiff, non-compliant ventricles 1
Do not overlook dynamic mitral regurgitation—functional MR that worsens with increased afterload during weaning attempts can be a hidden cause of failure and requires stress echocardiography for detection 1, 6
Special Considerations for Older Adults
Older adults have altered pharmacokinetics and pharmacodynamics requiring more cautious drug titration and sometimes reduced dosages. 1 Specific concerns include:
- Renal dysfunction affecting excretion of ACE inhibitors and digoxin (calculate creatinine clearance) 1
- Orthostatic dysregulation increasing fall and hypotension risk 1
- Blunting of receptor function affecting response to beta-agonists and other cardiovascular drugs 1
Mechanical Ventilation Considerations
The decision to intubate or continue mechanical ventilation in older adults with multiple comorbidities should involve early discussion with the patient or medical decision-makers about realistic estimates of complications, mortality, and quality of life. 1
For patients requiring prolonged mechanical ventilation:
- Daily interdisciplinary assessments should monitor for escalation or de-escalation opportunities 1
- Patients with explicit do-not-resuscitate preferences should not be candidates for aggressive interventions; pharmacological support or comfort care should be provided instead 1
- Age has been strongly associated with mortality in mechanically ventilated patients, though survival depends on both initial factors and development of complications during ICU management 1
Monitoring and Reassessment
Continuous monitoring for the first 24 hours post-extubation should include SpO₂ (targeting 88-92%), respiratory rate, and work of breathing. 4
Ongoing assessment should evaluate: