Sedation and analgesia

Question 1

Discuss causes of distress during ventilation

Answer 1

Pain, (infection lines and tubes)
dyspnoea (blocked ETT, pneumothorax)
anxiety
delirium (infection)

Question 2

Define delirium

Answer 2

acute reversible disturbance of consciousness and cognitive function that fluctuates in severity

Characteristic include

• defective perception
• reduced short term memory
• confusion
• disorientation
• occasionally hallucinations

Question 3

Discuss Richmond Agitation and sedation scale : The RASS

Answer 3

Scale from +4(combative) to -5 (unrousable)
0(alert and calm)
used to assess agitation and depth of sedation

Likley aiming for moderate sedation in early presentation with progressively reducing score

Question 4

Discuss approaches to agitation in sedated patient

Answer 4

One practice is to use opioids as the first line treatment of all agitated patient with ETT as there is inherent discomfort with the ETT and opioids are good at suppressing air hunger

If bolus doses need are increasing and becoming more frequent consider infusion if still not adeqaute consider sedative such as propofol

Question 5

Discuss drugs commonly implored in the agitated patient

Answer 5

Benzo
Opioid
neuroleptic and IV anaethetics
a2 adrenoreceptor agonist (dexmedetomidine)

Question 6

Discuss opiods in the setting of mechanical ventilation

Answer 6

preferred systemic analgesia
may be the best agents for relieving dyspnea during mechanical ventilation

Opiods elicit their action through stimulation of the mu, kappa and delta receptors which are widely distributed in the CNS. Stimulation of the U1 subunit blocks transmission of pain
Interaction at other sites lead to adverse affects including GIT hypomotility, CNS depression and hypotension.

Respiratory depression with opioids produces reduced resp rates and preservation of tidal volume which may be ideal for ventilated patients

Tolerance can be seen with all opioid drugs, psuedotolerance is an increase in dose needed for analgesia due to increase of noxious stimulus

Question 7

Discuss benzodiazepines in mechanical ventilation

Answer 7

Act through the GABA receptor causing an increase in frequency of the channel which is neuro inhibitory and thus causes neurons to be less excitable

These drugs have anxiolytic sedative amnestic and hypnotic effects

Because the anxiolytic efficacy and adverse effects of the commonly used IV benzodiazapines are similar selction should be based on PK

Midaz with short halflife and rapid onset is ideal for procedural sedation
loraz is ideal for those with advanced liver disease as glucuronidation remains preserved even preserved even advanced cirrhosis

Intermittent IV dosing is preferred as infusion have been associated with prolonged mechanical ventilation and excessive sedation

Patient who have recieved benzo for more then 1-2 weeks should receive tapering doses to avoid withdrawal

Question 8

Discuss propofol in mechanical ventilation

Answer 8

Commonly used in patient needing continuous sedation
exhibits sedative and hypnotic properties and amnestic properties similar to benzol

Modulates GABA
Onset seconds to mintues as is lipophilic ++
Rapid re-distibrution to tissue leading to early recovery of conciousness after ceasing infusion even if prolonged use

Reduces ICP and cerebral metabolism and blood flow

Hypotension is common asa result of decrease in venous and arterial tone and therefore cardiac output
Triglycerides need to monitored when using prop infusion
Strict asceptic technique needs to be used as medium supports bacterial growth

Question 9

Discuss propofol infusion syndrome

Answer 9

Characterised by refractory bradycardia and

1) rhabdo
2) metabolis acidosis
3) hyperlipidaemia
4) enlarged liver
5) hyperkalaemia

Question 10

Discuss the use of central alpha agonists in mechanical ventilation

Answer 10

Drugs that stimulate a2 adrenoreceptors decrease norad release form both central and peripheral sympathetic nerve terminals

These affects at both spinal and supraspinal sites provide a combination of sedative and analgesic effect without resp depression. Patient remain sedated when undisturbed but a easily rousable and it also provide anxiolytic effect comparable to benzo

Dexmedetomidine is highly selective a2 agonist

Primary side effects of dexmedetomidine are bradycardia and hypotension

Question 11

Discuss Spontaneous awakening trials

Answer 11

All patient should once daily have sedative drugs or analgeisc infusion interrupted once daily to minimize the risk of excessive side effects and to accessed for the ability to be weaned

contraindication include, neuromuscular blockade, ongoing obvious agitation or pain, uncontrolled seizures, alcohol or benzo withdrawal, elevated ICP and active myocardial ischaemia