Awareness Dr S Parthasarathy MD DA DNB MD

Awareness Dr. S. Parthasarathy MD. , DA. , DNB, MD (Acu), Dip. Diab. Dip. Software statistics Ph. D ( physiology), IDRA , FICA

Definitions • Awareness—Postoperative recall of events occurring during general anesthesia • Explicit memory—Conscious recollection of previous experiences (“awareness” is evidence of explicit memory) • Implicit memory— Changes in performance or behavior that are produced by previous experiences but without any conscious recollection of those experiences (“unconscious memory formation” during general anesthesia)

Definitions • Amnesic wakefulness—Responsiveness during general anesthesia without postoperative recall • Dreaming—Any experience (excluding awareness) that patients are able to recall postoperatively that they think occurred during general anesthesia and that they believe is dreaming.

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Incidence of Awareness • Around 7 % with nitrous alone previously • 0. 1 % to 0. 3 % - now • Up to 7 % in selected cases especially dreaming Light anes • Trauma, CABG, LSCS • Opioid abuse , pain states • Previous awareness , hemodynamic imbalance • Difficult airway, ASA 4 • Emergency – long duration Difficult to • More with the use of assess ? neuromuscular blockers

Abouleish and Taylor modified the Brice questionnaire 1. What was the last thing you remembered before going to sleep? 2. What was the first thing you remembered on waking? 3. Do you remember anything between going to sleep and waking? 4. While you were sleeping during the operation, did you dream?

Why we should be bothered ? Let him recall ? ? • “ Suddenly I felt that I could not breathe. I was totally alert. I could not feel my chest rising and I had no sensation of air moving in or out. It was a terrifying feeling !” • Its part of the contract between us and the patient for complete anesthesia !!

Consequences • Most cases of awareness are inconsequential • some patients experience prolonged and unwanted outcomes like post-traumatic stress disorder and depression. ( 14 %) • These late symptoms include nightmares, flashbacks and anxiety and have been reported to occur in up to 33% of the cases who experienced awareness. • Fear of future surgeries

For us ? • Recent examination of the American Society of Anesthesiologists’ (ASA) Closed Claim Project revealed that 2% of all claims were for awareness. Such claims are frequently successful, and poor anaesthetic technique is often blamed.

Identify awareness • The signs of awareness are generated through sympathetic activation. • Tachycardia, hypertension, movement, sweating, pupillary dilatation, lacrimation and sweating are often used as clinical signs of an inadequate level of anesthesia secondary to sympathetic activation. • Consider opioids, beta blockers, anticholinergics, relaxants and the response may change with the use of such drugs !

Depth of Anesthesia (Do. A) Monitors • Assurance of 0. 8 -1 MAC of exhaled anesthetic agent is likely to assure lack of awareness • But hypotension, bronchodilators and COPD • Will it correlate ? • When there is increased dead space, the inhaled gas will come back again to increase ET agent concentration but is it in the brain ?

Advanced monitoring • Bispectral index (BIS) • complex, processed electroencephalogram that uses a computer algorithm to assign a numerical value to the probability of consciousness • Keep it 40 – 60 • Better than clinical but with end tidal agent monitoring , advantage is ? • End tidal agent monitor is OK

Advanced monitoring • • Entropy Patient state analyser Narcotrend Cerebral function monitors • Only in very high risk ( for awareness) we may contemplate

Management Prevention !!

Three clinical scenario • Normal Requirement—Low Delivery • (IV or inhaled – problem in administration? Equipment ) • • • an empty vaporizer, miscalibration, impurities in the volatile agent (reducing its saturated vapour pressure) disconnection from the anesthetic machine. Blockage of an i. v. infusion pump or catheter, disconnection from the cannula or extravascular location of the cannula may risk awareness during TIVA.

Low delivery • Drug error • Infusion or inhalation • Check equipment prior proper • Miller quote • “ If the patient moves during anesthesia, if we give relaxants , its fine for the surgeon and anesthesiologist but for the patient , We need to add narcotics or agents”

When ? • Low Requirement—Very Low Delivery • LSCS • High Requirement—Normal Delivery • Opioid addict, alcohol addict , population variance: obesity; anxiety; young age; tobacco smoking; • (e. g. opioids, amphetamines, cocaine); chronic use of sedatives (e. g. temazepam); • previous and repeated exposure to anaesthetic agents

Use • Preoperative benzodiazepines • Midazolam admin decrease awareness • Think about delayed emergence in selected cases Preoperative consent for awareness possibility in sick patients

Clinical tip ! • If cardiovascular or respiratory depression occurs then these systems may require support (e. g. mechanical ventilation, inotropes). • Titration of anesthetic agents to arterial pressure risks intra operative awareness.

Postoperative management • establish the perioperative timing of the episode and distinguish between dreaming and awareness. • He should apologize to the patient if awareness has occurred and sympathize with the patient’s suffering. • A logical attempt should be made to explain what happened and its possible reasons, • Often the patient needs consultation from psychiatrist

Summary • • • Definition Incidence Consequences Identification Management Thank you all » Prevention and treatment