REVIEW OF SEDATION FOR EYE SURGERY

Journal Club Sedation during ophthalmic surgery. : 

Dr. Rajendra Prasad Koduri Specialist - Dept. of Anesthesia Mafraq hospital. Review article from the European Journal of Anesthesiology- EJA September 2008. Journal Club Sedation during ophthalmic surgery.

Introduction : 

Introduction The most common procedure in eye surgery is cataract surgery – with or without sedation followed by examination under anesthesia EUA for the pediatric population (sedation- sedoanalgesia to general anesthesia). Trends have shifted from G/A with ETT LMA Regional anesthesia( retro bulbar/ peribulbar & subtenon blocks topical anesthesia.

Intro-contd. : 

Intro-contd. What are the issues : Anxiety –eye/pain/discomfort/visual experiences -16% counselling is of help – but not widely practiced. Anxiety induces catecholamine release and can widely affect cardiovascular co-morbidity and diabetes –elderly patient. Patient satisfaction surveys showed 96.8 % were satisfied , 2.3 % were somewhat dissatisfied and 0.9 were dissatisfied- with a strong correlation between dissatisfaction and younger age , shorter procedures, post-op pain , nausea and vomiting and awareness.

Management of eye surgery under L/A. : 

Management of eye surgery under L/A. RCA-RCO (UK) & Agency for Healthcare Research and Quality (AHRQ) – USA have published guidelines. Goals –anxiolysis & per-operative/ post op pain relief. Objectives- block procedure as painless as possible/anesthetise the globe and conjuctiva produce akinesia of the eyeball and to reduce the intraocular and intraorbital pressures. Advantages-fewer systemic side effects/ easy communication with patients during the procedure.

Contra indications to local anesthesia. : 

Contra indications to local anesthesia. Patient uncooperative especially mentally impaired. Communication is difficult- language barrier/ deaf. Those who have involuntary movement disorders. Cardiovascular co-morbid patient with Grade 3 dyspnea/ orthopnea. Uncontrolled coughing or sneezing. Severely anxious patient or claustrophobic patient. Undergoing bilateral surgery. Difficult and prolonged surgery is likely. Preference by patient / surgeon/ anesthetist.

Local anesthesia vs.Topical anesthesia. : 

Local anesthesia vs.Topical anesthesia. Topical anesthesia may not provide pain control as complete as needle based techniques. Avoids serious complications such as retrobulbar hemorrhage, globe damage and spread of local anesthetics to unusual locations leading to life threatening complications. Akinesia of the eye is not ensured & coupled with the inadequate pain control and the activation of the central reflexes may stimulate nausea and vomiting.

sedation vs. sedo-analgesia. : 

sedation vs. sedo-analgesia. Patient preference stats show that 72% prefer a block compared to topical anesthesia and 66% preferred oral sedation to intravenous sedation. With iv sedations there were more interventions for heart rate rhythms and arterial oxygen desaturations. Katz et al found that sedation alone reduced pain during surgery but 3.4% of the patients had intra-operative pain and 2.7 % were dissatisfied. Drowsiness was seen in 2.7% and nausea and vomiting were a problem in 4.1%. The addition of an opiod significantly reduced the pain during surgery / reduced the drowsiness/and increased the patient satisfaction.

Sedo-analgesia. : 

Sedo-analgesia. Goals of sedo-analgesia --- induce drowsiness ,alleviate fear ,anxiety and pain without loss of verbal communication. Sedation must be achieved with preserved cardiovascular stability, little or no respiratory depression, good operating conditions with a rapid return to pre-op mental and physical state and little residual effects. The ASA has quantitated various levels of sedation with the help of scoring systems.

The sedation scales. : 

The sedation scales. The Ramsey sedation scale.

Observer’ assessment of awareness, sedation scale- OASS : 

Observer’ assessment of awareness, sedation scale- OASS

UMSS- University of Michigan sedation scale. : 

UMSS- University of Michigan sedation scale.

Drugs used for sedation. : 

Drugs used for sedation. Ideal sedative drug should have rapid onset and short duration of action, does not cumulate, is non toxic, has a favorable therapeutic index and has predictable side effects. Do we have it ????----the answer is no. What are our options? Benzodiazepines, iv induction agents ,AAA such as dexmed and clonidine & opiates. The iv route is the most easily adjustable and can be used as PCA- TCI-PCS or bolus injections.

The benzodiazepines. : 

The benzodiazepines. Excellent amnesia, anxiolysis and hypnosis. Oral and intravenously PCS. Residual effects reversed when required. Midazolam is short acting with K ½ of 90 minutes and has the advantage of rapid onset & no venous irritation. Suggested iv doses are 10-15 micro /kg. and suggested set in time for sedation in the elderly is 5-10 minutes with dose reductions by 30% in patients over 60 yrs. Morley et al and Irwin et al ( Journal of anesthesia and intensive care 1997/ anesthesia -2000) compared PCS Midazolam 100 microgram bolus with PCS propofol 3.3 milligrams bolus and reported equal reductions in anxiety by the Ramsey sedation scores but concluded that Midazolam prevented increases in blood pressure with the insertion of block.

The intravenous induction agents. : 

The intravenous induction agents. Propofol – suitable for infusion and sedation. The mean target levels for sedation are 2.2 microgm/ml by the TCI. In the PCS study elderly day care surgery patients over 60 yrs received self administered propofol in 0.25 mg/kg bolus injections with a lock out of 3 mts. The total # of patients using PCA was 14/20 & only 8/ 20 used the PCA once and 6/20 used it <3 times and 18/20 patients reported complete satisfaction with the PCA.

The iv. induction agents –contd. : 

The iv. induction agents –contd. KETAMINE is another drug useful for sedation. Cardiovascular stability and no effect on respiration. Low dose ketamine 10-20 mg along with propofol 10-20 mg or midazolam 10 microgram/kg provided superior analgesia and patient comfort than with either drugs used alone. no effects on intraocular pressure but the incidence of nausea, vomiting are higher than the other groups.

Analgesic agents. : 

Analgesic agents. Fentanyl is a potent narcotic analgesic with a duration of action of about 30 minutes after a single dose. Aydin and colleagues showed that PCA fentanyl in a loading dose of 0.7 microgm/kg followed by 5 micro bolus/ 5mt lockout intervals has supplemental analgesic effects with topical analgesia and increased patient / surgeon satisfaction. Alfentanil is a more rapid and shorter acting analogue of fentanyl. The incidence of respiratory depression is high in the elderly patients. The suggested dose is 20 micro/kg and has been used for placement of RB blocks.

Analgesic agents contd. : 

Analgesic agents contd. Remifentanil is the latest analogue of fentanyl and has unique degradation characteristics with k1/2 of 3-10 minutes. Produces intense analgesia with a predictable duration of action. Profound respiratory depressant and supplemental oxygen should be given. May cause profound fall in BP/ HR and must be used with caution in the elderly. The suggested regimes by Swedish coworkers is 3 micro/kg/hr +/_ 1 micro along with propofol 70 micro/kg/hr with no changes in hemodynamics/ respiratory parameters and good pain relief.

Other agents. : 

Other agents. Dexmeditomidine is a AAA and has been used for ophthalmic sedation with good results. A suggested regime is 2.5 microgm/kg bolus in 10 mts followed by 0.4 microgm/kg /hr until the last suture without undue hemodynamic fluctuation. (s/e- hypotension) Clonidine is a centrally acting AAA that reduces sympathetic outflow from the brain secondary to its stimulating effects on the vasomotor centre. Clonidine used in the dose range of 0.5-2.0 microgm/ kg can be added to the local anesthetic itself for the block causes direct reductions in IOP, sedative effects and produces increased duration of akinesia and analgesia with decreases in both HR and SVR.

Practical and simple methods of drug administration for ophthalmic sedation. : 

Practical and simple methods of drug administration for ophthalmic sedation.

Slide 20: 

A brief review of the literature since 1953 1 slide The cleveland clinic guidelines for procedural sedation not specific to eye surgery-----------------2 slides. A total of 22 slides for the presentation.