Safe sedation—general principles
- DOI:
- 10.1093/med/9780198703860.003.0070
• IV sedation commonly used for bronchoscopy and thoracoscopy and, less frequently, for other procedures, e.g. chest drain insertion. Studies show that both patients and physicians usually prefer the use of sedation for bronchoscopy, although some tolerate unsedated bronchoscopy well; consider patient preference and comorbidities
• Follow Summary of Safe Sedation Practice (UK Academy of Medical Royal Colleges) (see Table 70.1)
• Sedation is usually the responsibility of the physician performing a procedure, although some units have anaesthetist-delivered sedation
• Desired depth of sedation is usually conscious sedation—patient maintains airway patency and cardiorespiratory function, and verbal contact with the patient is possible at all times. Some procedures (e.g. interventional bronchoscopy) may require deeper sedation provided by anaesthetists, with same level of care and monitoring as for a general anaesthetic
• Significant interpatient variability to IV sedation; therefore, essential to titrate sedatives, using small incremental doses, to avoid oversedation
• Assess (and document) sedation depth. Tools, such as the Ramsay Scale (see Table 70.2) and the Modified Observer’s Assessment of Alertness/Sedation (MOAAS) (see Table 70.3) score, may help documentation.
Table 70.1 Summary of Safe Sedation Practice
Domain |
Safe practice |
|---|---|
Patient assessment |
|
Level of sedation |
Sedation provided only to the level of ‘conscious’ sedation (verbal contact possible) |
IV sedation |
|
Monitoring |
Defined professionals have responsibility for monitoring patient safety and making a written record. Pulse oximeter monitoring continued until discharge from unit. Consider monitoring BP and ECG in higher-risk patients |
O2 therapy |
Nasal cannula and facial mask O2 delivery available |
Table 70.2 Ramsay scale
Level |
Response |
|---|---|
1 |
Anxious and agitated or restless |
2 |
Cooperative, orientated, and tranquil |
3 |
Responds only to commands |
4 |
Brisk response to light glabellar touch or loud noise |
5 |
Sluggish response to light glabellar touch or loud noise |
Ramsay MA et al Controlled sedation with alphaxalone-alphadolone. Br Med J 1974;2(5920):656–9.
Table 70.3 Modified Observer’s Assessment of Alertness/Sedation (MOAAS) scale
Level |
Response |
|---|---|
5 |
Responds readily to name spoken in normal tone |
4 |
Lethargic response to name spoken in normal tone |
3 |
Responds only after name is called loudly or repeatedly |
2 |
Responds only after mild prodding or shaking |
1 |
Does not respond to mild prodding or shaking |
Chernik DA et al. Validity and reliability of the Observer’s Assessment of Alertness/Sedation Scale: study with intravenous midazolam. J Clin Psychopharmacol 1990;10(4):244–51.
See Appendix 5 for further details about drug doses, pharmacology, and side effects.
Benzodiazepines
• Benzodiazepines cause sedation, anxiolysis, and anterograde amnesia by binding to, and increasing the activity of, γ-aminobutyric acid (GABA), a brain neuroinhibitory transmitter
• Midazolam (used by 78% of bronchoscopists) improves experience of bronchoscopy, reduces procedural discomfort, causes anterograde amnesia, and increases willingness of patients to have further procedures without worsening adverse event profile
• Other benzodiazepines (e.g. diazepam and lorazepam) have also been used, but midazolam has particular suitability with rapid peak effect and relatively short half-life
• Natural variability in action of cytochrome P450 (CYP) 3A4 and 3A5, responsible for benzodiazepine metabolism, may prolong elimination half-life by up to sixfold
• Flumazenil (benzodiazepine antagonist) reverses benzodiazepine oversedation and must be immediately available, although administration should not be routine. Flumazenil has a shorter half-life than midazolam, so potential risk of re-sedation
• A 2008 NPSA report documented harm and death from excessive midazolam. To prevent inadvertent injection of high-strength midazolam solution (2 or 5mg/mL), NPSA mandates that only low-strength midazolam solution (1mg/mL) should normally be available in clinical areas
• Following a 2004 NCEPOD report (see Sedation in specific circumstances,
p. [link]), no more than 5mg midazolam should be initially drawn up into any syringe prior to a procedure for patients aged <70 (2mg midazolam for patients >70), to reduce likelihood of oversedation.
Opioids
• Mechanism of action of opioids are not completely understood, but they are known to be mu-opioid receptor agonists, causing analgesia, sedation, and cough suppression
• Fentanyl and alfentanil both have favourable pharmacological profiles, having a rapid peak effect and a relatively short half-life
• Naloxone (competitive antagonist) reverses opioid-induced respiratory depression and oversedation. For oversedated patients who have received both benzodiazepine and opioid, initial reversal with flumazenil (rather than naloxone) recommended, unless the patient has received particularly high dose of opioid
• Addition of an opioid to midazolam for bronchoscopy improves procedural cough, reduces lidocaine usage, and increases patient procedural tolerance. Most frequent combination agents used for bronchoscopy are midazolam and fentanyl/alfentanil. Opioids should be administered (and allowed to reach maximal effect) prior to administration of midazolam. Risk of oversedation may increase when using combination agents, although several studies fail to show an increase in clinically significant adverse events.
Other drugs
• Propofol (and its pro-drug fospropofol) are sedative-hypnotics that exert their actions partly by increasing GABA activity. Together with ketamine, these drugs have a relatively narrow therapeutic window between ‘conscious’ sedation and general anaesthesia and are currently recommended for use solely by anaesthetists in the UK.
Sedation in specific circumstances
• Risks may be increased when using combined sedation for patients in respiratory failure, and caution is recommended
• Elderly patients are likely to require lower doses of sedatives and may suffer with prolonged after-effects (e.g. amnesia and coordination impairment). A 2004 NCEPOD report for elderly patients undergoing therapeutic GI endoscopy recommended that no more than 2mg should be initially drawn up for patients aged >70
• Other comorbidities likely to require dose modification include hepatic impairment, heart failure, and renal impairment
• Concomitant medications (e.g. antifungals, antiretrovirals, CCBs, and macrolide antibiotics) inhibit cytochrome P450 3A4 (which also metabolizes benzodiazepines and opioids) and may prolong sedation.
