By relieving anxiety, reducing pain, and providingamnesia, sedation techniques have the potential to render potentially uncomfortablediagnostic and therapeutic procedures more comfortable and acceptable for patients. However, they also have the potential to cause life-threatening complications.
Outline Definition of sedation Drugs used for sedation Generic principles of adult procedural sedation The role of anaesthetists and ensuring safe sedation practice
Sedation is a drug-induced depression of consciousness , a continuum culminating in general anaesthesia,used for the reduction of irritability or agitation by administration of sedative drugs
Levels of Sedation Minimal Moderate Deep Minimal sedation: • responds normally to verbal commands • Cognitive function and physical coordination may be impaired, but airway reflexes, and ventilatory and cardiovascular functions are unaffected.
Moderate sedation(conscious sedation): • Conscious,response to verbal commands • airway reflexes is normally unaffected • Adequate spontaneous ventilation
Deep sedation: • loss of consciousness, responds to repeated or painful stimulation • Loss of airway reflexes ( risk of airway obstruction and aspiration) • ventilatory depression
Aspiration of Gastric content: Stimulation of pharyngeal reflexes due to these procedures increases risk of aspiration which may followed by death within minutes from asphyxiation or chemical pneumonitis.
Drugs used for sedation during these procedures are: midazolam and propofol. Midazolam: • water soluble short-acting benzodiazepine • presents as a clear colourless solution 1/2/5 mg/ml • has many indications including for sedation during endoscopy • Onset: 2-3 min, Duration: 20-60 min.
Main actions : hypnosis sedation anxiolysis anterograde amnesia anticonvulsant muscular relaxation
Mode of action: act via specific benzodiazepine receptors linked to GABA receptors. • Dose: for sedation 0.07-0.1 mg/kg IV, titrated according to response(drowsiness,slurring of speech,respose to command). • Effects on: CVS: decrease SBP by 5%, DBP by 10%, SVR by 15-33%. Increase HR by 18% .
RS: Decrease tidal volume but increase RR, impairs ventilatory response to hypercapnia. CNS: Hypnosis,sedation,anterograde amnesia. Decrease cerebral oxygen consumption and cerebral blood flow. AS: decrease hepatic blood flow. GU: decrease renal blood flow.
Kinetics: 96% protein bound, metabolized in liver and excreted in urine. • Cautions and Contraindications: in the elderly, during pregnancy, in children, in alcohol- or drug-dependent individuals or those with comorbid psychiatric disorder, Additional caution is required in critically ill patients, as accumulation of it and its active metabolites may occur. hypersensitivity, acute narrow angle glaucoma, shock, hypotension or head injury, most are relative contraindications. • The clinical effects can be reversed by physostigmine,glycopyrronium and flumazenil.
Propofol: • A 2,6-diisopropylphenol • Presents as a white oil-in-water emulsion 1% or 2%. • Has many indications including for sedation during some procedures. • Rapid onset of action with short duration of action. • Main action: hypnotic. • Mode of action: is unclear.
Dose: 0.5-1 ng/kg/min by infusion pump (TCI) for conscious sedation. • Effects: CVS: Decrease BP and SVR by 15-25% without a compensatory increase in HR, decrease CO by 20%, may cause vasodilatation,bradycardia even asystole. RS: Bolus dose may produce apnoea and suppresion of aiway reflexes.
Infusion of propofol decreases tidal volume, increases RR, depresses ventilatory response to hypercarbia and hypoxia. CNS: Smooth rapid induction with rapid and clear-headed recovery. AS: antiemetic. • Kinetics: 97% protein bound, rapidly metabolized in liver, excreted in urine,renal and hepatic disease have no clinically significant effect on its metabolism.
Caution and Contraindication: Reduce dose in elderly and haemodynamically unstable patient. Caution in severe allergy to egg and in epilepsy. Not recommended in C/S.(pregnancy??)
Generic principles • Pre-assessment • Patient management and choice of technique • Multiple drugs and anaesthetic drugs/infusions • Monitoring • Setting
Pre-assessment The importance of pre-assessment and preparation of patient for such procedures is such as for GA .
Patient management and choice of technique A clear explanation at every stage is essential to reassure the patient, particularly where sudden movements may compromise the procedure. The principle of minimum intervention, the simplest and safest effective technique, based on patient assessment and clinical need, should be used.
Careful consideration of the demands of the procedure being undertaken, particularly whether it is painful or not, is critical to success. For non-painful procedures sedation alone is sufficient. Painful procedures require the administration of a specific analgesia agent.
Multiple drugs and anaesthetic drugs/infusions Drugs in combination may produce synergistic effects, have differing times to onset and peak effect, and be unpredictable or difficult to titrate to effect. Safety margins may be narrowed, increasing the likelihood of overdose, loss of consciousness, respiratory depression and the need for airway interventions.
Where a combination of a benzodiazepine and an opioid is administered, the opioid should be given first and the benzodiazepine only given once the peak effect of the opioid is observed. Benzodiazepines may be up to eight times more potent after prior administration of an opioid and so must be titrated with care.
Anaesthetic drugs and infusions (e.g. propofol) have a narrow therapeutic index and reduced margins of safety, increasing the likelihood of adverse events. Multiple drug/anaesthetic drug techniques should only be considered where there are full resuscitation and general anaesthetic facilities.
Monitoring Oxygenation pulse oximetry ECG NIBP Capnography Verbal communication Monitoring should be continued through recovery until the discharge criteria are met.
Setting Staffing and equipment. Appropriate recovery facilities and discharge criteria. Resuscitation equipment must be checked, maintained, and include all the drugs necessary for life support. The management of sedation-related complications and medical emergencies should be regularly rehearsed as a team.
The role of anaesthetists and ensuring safe sedation practice • Anaesthetists, as experts in the use of anaesthetic drugs and management of the unconscious patient, should be qualified to provide sedation services. • The Royal College has developed a curriculum detailing the competencies, training, and assessment necessary for safe and appropriate use of sedation techniques by anaesthetists.
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