20% of all patients requiring mechanical ventilation suffer from neurological dysfunction.
Major contributor to prolongation of mechanical ventilation in over a third of patients admitted in ICU.
2. INTRODUCTION:
• Brain injury may be main indication for mechanical ventilation in up to 20% of cases
• Major contributor to prolongation of mechanical ventilation in over a third ofpatients
• 20% of all patients requiring mechanical ventilation suffer
from neurological dysfunction.
• Major contributor to prolongation of mechanical
ventilation in over a third of patients admitted in ICU.
3. Indications for mechanical
ventilation:
• Loss of respiratory drive,
• Dysfunction of lung compliance,
• low Glasgow Coma Scale (GCS) that is hampering gas
exchange
• Ventilatory failure due to disorders of the neuromuscular
junction
• Airway obstruction caused by the falling back of flaccid
tongue on the posterior pharyngeal wall in neurologically
obtunded patients
• Life-threatening sequelae such as pneumonia and acute
respiratory distress syndrome (ARDS).
12. Neuromuscular diseases:
• This should focus on four elements:
• 1. Determining the severity of weakness
• 2. Characterising involvement of bulbar muscles (and thus risk of
aspiration)
• 3. Characterising involvement of respiratory muscles
• 4. Determining the cause, such that appropriate treatment can be
instigated
13. • Maximal negative inspiratory force (an index of inspiratory muscle
function)
• Maximal expiratory force (reflecting force of cough)
• Forced Vital Capacity
• Peak Expiratory Flow Rate
14. • A rough estimate of the Forced Vital Capacity can be obtained
by asking the patient to count to 20 after taking a single
breath: inability to do so corresponds to a greatly reduced vital
capacity in the order of 15–18 mL/kg (normal values are 65–75
mL/kg).
• A VC of less than 1 L (or <20-25 mL/kg) or a NIF <30 cm H2O
indicates significant respiratory weakness;
• In addition, a PEF <40 cm H2O indicates poor expiratory
function .
15.
16. Respiratory Care:
• The airway should be opened by suctioning secretions after positioning the jaw
and tongue.
• High-flow oxygen should be administered and oxygen saturation be monitored by
pulse oximetry continuously.
• The 20/30/40 rule (FVC<20 mL/kg; MIP<30 cmH2O; and MEP<40 cmH2O) is
probably the most helpful guide to decide intubation
• Elective intubation of a patient with impending respiratory failure is favoured
over emergent intubation
17. Intubation and Ventilation:
• Neuromuscular blocking agents (paralytics) should be used
with caution when intubating these patients.
• Depolarizing agents (for example, succinylcholine) are less
potent in myasthenics because fewer functional post-synaptic
anti-AChR are available.
• This decrease in receptors also results in a decrease in the
safety margin or remaining AChR available for neuromuscular
transmission.
• Nondepolarizing agents (fornexample, vecuronium) have
increased potency, and reduced doses are required for
paralysis.
• A rapid-onset nondepolarizing agent (ie, rocuronium,
vecuronium) is the preferred paralytic agent for these patients.
18. Spinal cord:
• Lesions above C5 cause complete paralysis of the
phrenic and intercostal nerves requires long periods of
controlled ventilation and an early tracheostomy.
• Lesions below C5 shows variable course with high
incidence of delayed-onset respiratory failure because
of :
1. Muscle fatigue,
2. Aspiration pneumonia
3. Atelectasis,
4. Pooling of secretions
19. • Development of spasticity in the intercostal muscles,
favorable effect on the lung mechanics.
• Patients with spinal cord injury require either controlled
or assisted modes of ventilation depending
1. Site and extent of the lesion,
2. Amount of respiratory muscle compromise,
3. Degree of respiratory drive present,
4. Duration of injury.
20. Brainstem and cortex:
• TBI, ICSOLs, Stroke cause:
1. Impairment of the respiratory drive
2. Result in aberrant respiratory patterns such as hypo-
and hyperventilation syndromes, apnea, and Cheyne–
Stokes breathing.
• Controlled ventilation as the initial mode, followed by
switching to assisted modes if improvement
21. Cerebral Perfusion
Cerebral Perfusion
Cerebral Perfusion:
• Adult brain is only 2% of body weight
–15 % of the resting cardiac output
–20 % of the total body oxygenconsumption
• Blood flow regulated by three primaryfactors
1. Metabolic stimuli
2. Chemical stimuli
3. Perfusion pressure
23. ALI / ARDS is Common…
• In polytrauma with traumatic brain injury
But Also in
1. Isolated traumatic brain injury
2. Subarachnoid hemorrhage
• ALI rates as high as 30% in severe brain injury ALI/ARDS risk associated with severity of injury
Associated with worse outcomes
24. Conflicting Paradigms:
Historical brain directed strategies
Optimize oxygen delivery
Control of PCO2 (higher VT and VE)
minimize potentiall effects of PEEP
Lung protective mechanisms
Avoid overdistention (Volutrauma)
Open the lung
Avoid cyclical collapse (Atelectrauma)
29. CO2 : Concern Over Hypercapnia
• Concern that hypercapnia may worsen:
– Hyperemia
– ICP cerebral herniation
• This is a concern in patients with very low
intracranial compliance(little
compensatory reserve)
31. CO2 : Too Little of a Good Thing!
• Hypocapnia-related reduction in CBFcauses:
– Metabolic crisis
– Increases ischemic brain volume
• Early, prophylactic hyperventilation intraumatic brain injury
associated withworse outcomes
32. So The bottom line…….
•Eucapnia should be maintained
•Hypocapnia only if ICP emergency
•No ICP? Be wary of PCO2 if signs of low intracranial compliance
CT:
–Effaced basal cisterns
–Small ventricles
–Hydrocephalus
–Sulcal effacement
33. PEEP: Concern Over ICP
• High levels of PEEP may be bad inbrain-injured patients:
1.Decreased venous drainage
Transmission of intrathoracic pressure
Increased ICP
2. Deceased Cardiac Output
Decreased CBF
34. PEEP & ICP: Complex Relationship
Venous Drainage
Intracranial
Compliance Head Elevation
ICP Starling
Resistors
Pulmonary
compliance
35. Weaning readiness Criteria
• Awake and alert
• Hemodynamically stable
• Arterial blood gases (ABGs) normalized or at patient’s
baseline - PaCO2 acceptable
• PH of 7.35 – 7.45
• PaO2 > 60 mm Hg ,
• SaO2 >92% -
• FIO2 ≤40%
36. • Positive end-expiratory pressure (PEEP) ≤5 cm H2O
• RR< 25 / minute
• Vt 5 ml / kg
• VE 5- 10 L/m (RR x Vt)
• VC > 10- 15 ml / kg
37. • Chest x-ray reviewed for correctable factors; treated as
indicated,
• Major electrolytes within normal range,
• Hematocrit >25%,
• Core temperature >36°C and <39°C,
• Adequate management of pain/anxiety/agitation,
• Adequate analgesia/ sedation (record scores on flow
sheet),
• No residual neuromuscular blockade.
39. T-Piece trial
• It consists of removing the patient from the ventilator
having him / her breathe spontaneously on a T-tube
connected to oxygen source.
• During T-piece weaning, periods of ventilator support are
alternated with spontaneous breathing.
• The goal is to progressively increase the time spent off
ventilator
40. Synchronized Intermittent Mandatory Ventilation ( SIMV)
Weaning
• SIMV is the most common method of weaning. •
• It consists of gradually decreasing the number of breaths
delivered by the ventilator to allow the patient to increase
number of spontaneous breat
41. Continuous Positive Airway Pressure ( CPAP) Weaning
• When placed on CPAP, the patient does all the work of
breathing without the aid of a back up rate or tidal
• No mandatory (ventilator-initiated) breaths are delivered
this mode i.e. all ventilation is spontaneously initiated by
the patient.
• Weaning by gradual decrease in pressure value
42. Parameters to be looked before weaning:-
1- Ensure that indications for the implementation of Mechanical ventilation have
improved
2- Ensure that all factors that may interfere with successful weaning are
• - Acid-base abnormalities
• Fluid imbalance
• Electrolyte abnormalities
• Infection
• Fever
• Anemia
• Hyperglycemia
• Sleep deprivation
43. Cont..
3- Assess readiness for weaning
4- Ensure that the weaning criteria / parameters are met.
5- Explain the process of weaning to the patient and offer
reassurance to the patient.
6- Initiate weaning in the morning when the patient is
rested.
7- Elevate the head of the bed & Place the patient upright
8- Ensure a patent airway and suction if necessary before a
weaning trial
44. Cont..
9 - Provide for rest period on ventilator for 15 – 20 minutes
after suctioning.
10- Ensure patient’s comfort & administer pharmacological
agents for comfort, such as bronchodilators or sedatives as
indicated.
11- Help the patient through some of the discomfort and
apprehension.
12- Evaluate and document the patient’s response to
weaning
45. Signs of Weaning Intolerance Criteria
• Diaphoresis
• Dyspnea & Labored respiratory pattern
• Increased anxiety ,Restlessness, Decrease in level of
consciousness
• Dysrhythmia, Increase or decrease in heart rate of > 20
beats /min. or heart rate > 110b/m, Sustained heart rate
>20% higher or lower than baseline
46. Cont…
• Increase or decrease in blood pressure of > 20 mm Hg
Systolic blood pressure >180 mm Hg or <90 mm Hg •
• Increase in respiratory rate of > 10 above baseline or >
Sustained respiratory rate greater than 35 breaths/minute
• Tidal volume ≤5 mL/kg, Sustained minute ventilation
mL/kg/minute •
• SaO2 < 90%, PaO2 < 60 mmHg, decrease in PH of < 7.35.
Increase in PaCO2
47. Complications of mechanical ventilation and
its prevention
• Hypotension- increase preload by fluids and decreasing airway pressures
• Pneumothorax- reduce VT and PEEP to be used cautiously
• Decreased cardiac output- use of fluids and ionotropes
• Nosocomial pneumonia-
1. Avoid cross-contamination by frequent handwashing
2. Decrease risk of aspiration (cuff occlusion of trachea, positioning, use of small-
bore NG tubes).
3. Suction only when clinically indicated, using sterile technique.
4. Maintain closed system setup on ventilator circuitry and avoid pooling of
condensation in the tubing
5. Ensure adequate nutrition
6. Avoid neutralization of gastric contents with antacids and H2 blockers
7. Use humidifier.
48. Cont……..
• Positive water balance- decrease fluid intake
• Increased ICP- reduce PEEP
• Sinusitis and nasal injury- proper airway management and gentle
suctioning and removal of all tubes with antibiotics
• Mucosal lesions- may resolve on its own or surgical intervention
• Aspiration- proper airway patency with antibiotic use.
49. Non-Invasive Ventilation
• Non invasive ventilation (NIV) may be used to prevent intubation or reintubation
of patients in myasthenic crisis.
• With bi-level positive airway pressure (Bi PAP), positive pressure is applied during
both phases of respiration, enhancing airflow and alleviating the work of
breathing during inspiration and preventing airway collapse and atelectasis
during expiration
• Initial use of NIV is associated with a shorter duration of ventilatory support.
50. • Independent predictors of NIV success are a serum bicarbonate <30 mmol/L
• Independent predictor of NIV failure is hypercapnia (PCO2 >45mm Hg).
51. ICU AQUIRED WEAKNESS
• RISK FACTORS
Mechanical Ventilation for more than 7days
Systemic Inflammatory Response syndrome, sepsis
Multi organ Failure
52. • CLINICAL FEATURES
1. Difficult to wean
2. Lower limb weakness More than Upper Limb
3. Symmetric Flaccid Paralysis
• Electrophysiological Studies
I. Nerve conduction shows distal sensorimotor axonopathy
with reduced CMAP and sensory action potential.
II. No evidence of demyelination.
53. Conclusion:
• Mechanical ventilation in neurological and neurosurgical cases
is a multidisciplinary approach requiring involvement of
Neurologist, neurosurgeon and anaesthesiologist.
• Acute Lung Injury is common in patients with
brain injury
• Be vigilant about PCO2 – hypocapnia can beharmful!
• PEEP appears safe in patients who need it
• Protect the lungs, but prioritize CO2 controland cerebral
perfusion
• Proper hand hygiene should be maintained
54. References
• Bradley 8th Edition.
• Continuum Journal.
• Bratton SL et al. Neurosurgery 1997.
• Kahn JM et al. Crit Care Med 2006.
• Holland MC et al. J Trauma 2003.
• Coles JP et al. Crit Care Med. 2007.
• Muizelaar et al. J Trauma. 1991.
• Carrera E et al. J Neurol Neurosurg Psychiatry. 2010
• Up to date
