Newsletter 13, March 2006 - British Ophthalmic Anaesthesia Society

30 Pages·2010·0.58 MB·English

by  Chandra Kumar

1

Ophthalmic Anaesthesia News
The Official Newsletter of the British Ophthalmic Anaesthesia Society
Issue 13, March 2006

Page - Contents Controversies in anaesthesia: anaesthesia technique and trabeculectomy
1. Controversies in
failure
anaesthesia: anaesthesia
Tom Eke, Consultant Ophthalmologist, Norwich
technique and trabeculectomy
failure: Tom Eke
6. Agents for sedation in Can anaesthesia technique influence the outcome of surgery? A good
ophthalmic surgery: a review
anaesthetic will provide optimum conditions for the surgeon, thereby reducing
of the pharmacodynamics and
the likelihood of per-operative complications. But can the choice of anaesthetic
clinical applications: Hannes
have a more lasting effect on surgical outcome? In glaucoma surgery, the
Loots & Roger Wiseman
18. Weill-Marchesani answer may be yes, though this is still a matter of controversy.
Syndrome-is it difficult to This issue was raised in a 1993 paper from Moorfields Eye Hospital. Sub-
intubate?:Waleed Riad
conjunctival anaesthesia (SCA) was being used for more and more
20. A small model for
trabeculectomies, until one of the clinicians noticed what appeared to be a high
practising sub-Tenon‘s block:
incidence of avascular, leaky blebs with this technique. A chronically leaking
M Baloch & T Vorster
21-24. BOAS 2006 meeting bleb is undesirable as it can lead to endophthalmitis or hypotony, each of which
details is potentially devastating to the vision. A review of cases showed that the
25. BOAS Annual Meeting
prevalence of bleb leakage was indeed higher in the SCA group, though
Report: S Tighe
pressure control was good in both groups. At around one year post-operatively,
26. News and information
bleb leak was seen in 77% for patients who had had SCA (2ml of 2% lidocaine),
28. BOAS Committee
29. Joining form as opposed to 25% for those who had GA for their trabeculectomy surgery. The
authors speculated that the LA might exert an inhibitory effect on conjunctival
Editor:
healing.
Prof Chandra Kumar
A large prospective study of trabeculectomy also concluded that sub-

Associate Editors conjunctival anaesthesia may be undesirable, but for completely different
Dr Monica Hardwick reasons. The 1997 National Audit of Trabeculectomy looked prospectively at
Dr Stephen Mather
1454 cases of primary trabeculectomy, done under the care of 382 UK
Mr David Smerdon
consultant ophthalmologists. Only a small proportion of trabeculectomies
Dr Sean Tighe
(38/1454, 2.6%) were done using SCA. Data was collected for numerous
The Society cannot be held aspects of the surgery, and follow-up was done at one year. Late bleb leakage
responsible for the statements
was less than 3% in all groups. Sub-analysis suggested that trabeculectomy
or views of the contributors.
failure (defined in terms of intra-ocular pressure reduction) was more prevalent
No part of this Newsletter may
in the SCA group. It appeared that ‗success‘ rates were only 39.5% in the SCA
be reproduced without prior
permission. group, as opposed to 65-70% for GA or other LA techniques.
So where does this leave us? One study suggests that SCA leads to a very high
Articles of interest for future
likelihood of chronic leakage, but good pressure control. The other suggests that
issues or correspondence
chronic leakage should not be a problem with any anaesthesia technique, but
should be sent by post, disk or
email: found poorer success rates when SCA was used. It must be remembered
that the Moorfields study was retrospective and non-randomised, and the
Professor Chandra Kumar
National Audit of Trabeculectomy was also a non-randomised observational
The James Cook University
study with relatively few SCA cases, and therefore other confounding factors
Hospital
Middlesbrough TS4 3BW, UK could easily explain the apparent low success rates with SCA. The National
Tel [phone]

Fax [phone]
Ophthalmic Anaesthesia News, Issue 13, March 2006
[email protected]
[email protected] Website http://www.boas.org
2
Audit investigators suggested a prospective failure or late bleb leakage. More work is needed
randomised trial to look at whether SCA itself is to look into a likely dose-dependent ‗anti-
a risk factor for failure. Studies on skin wounds scarring‘ effect of lidocaine on the conjunctiva.
have shown that infiltration with 1% or 2% An interesting possibility is that lidocaine may be
lidocaine will significantly weaken a scar, as good as cytotoxics in modulating wound
whereas 0.5% lidocaine has little or no effect. healing after trabeculectomy surgery.
Thus, it is possible that sub-conjunctival
lidocaine has a dose-dependent anti-scarring References
effect on the conjunctiva, similar to that of the 1 Noureddin BN, Jeffrey M, Franks WA,
anti-metabolites that are frequently used to Hitchings RA. Conjunctival changes after
enhance success rates for trabeculectomy. subconjunctival lignocaine. Eye. 1993;7 ( Pt
Many glaucoma specialists have been using SCA 3):457-460.
successfully for some years. My own practice is 2 Edmunds B, Bunce CV, Thompson JR,
to use a low dose SCA, as 0.5ml 0.5% lidocaine Salmon JF, Wormald RP. Factors associated with
SCA supplemented with intra-cameral lidocaine, success in first-time trabeculectomy for patients
for virtually all trabeculectomy surgery. I use this at low risk of failure with chronic open-angle
lower strength because of concerns about a glaucoma. Ophthalmology. Jan 2004;111(1):97-
possible detrimental effect of lidocaine on wound 103.
healing. Clinical audit has shown that the 3 Vicary D, McLennan S, Sun XY. Topical plus
technique is highly acceptable to patients. subconjunctival anesthesia for
Success rates are significantly better than the phacotrabeculectomy: one year follow-up. J
National Audit of Trabeculectomy, with no Cataract Refract Surg. Sep 1998;24(9):1247-
leakage at one year and virtually identical success 1251.
rates to those of my colleague who routinely uses 4 Drucker M, Cardenas E, Arizti P, Valenzuela
peribulbar LA. There is a suggestion of a higher A, Gamboa A. Experimental studies on the effect
rate of early bleb leakage, but this may be due to of lidocaine on wound healing. World J Surg. Apr
surgical technique rather than anaesthesia per se. 1998;22(4):394-397; discussion 397-398.
Sub-conjunctival anaesthesia (SCA) does not
appear to increase the risk of trabeculectomy

Ophthalmic Anaesthesia News, Issue 13, March 2006
[email protected] Website http://www.boas.org
3

Publication of this newsletter
has been possible by a
generous donation from

Abbott Laboratories Ltd
Queenborough
Kent, ME11 5EL

3
4

4
5
5
6
Agents for sedation in ophthalmic surgery: a drugs like midazolam, propofol and remifentanil
review of the pharmacodynamics and clinical are the favourites for sedation in eye surgery. It
applications might be necessary to take another look at the
group of alpha-2 adrenergic agonists and also
Hannes Loots. Faculty of Health Sciences, perhaps at low-dose ketamine.
University of Stellenbosch. South Africa
Medical Directorate, Solutio Hospital Benefit Key words: sedation agents, ophthalmic surgery,
Management, Medscheme Town, South Africa. pharmacology, dosage regimes, clinical
application.
Roger Wiseman., Medical Directorate, Solutio
Hospital Benefit Management, Medscheme ―performing painless eye blocks without sedation
Town, South Africa. is probably the safest route‖
BP Gallacher 1.
Abstract
Sedation is often required to improve patient
―Although many ophthalmic procedures can be
comfort during the placement of local blocks in
performed on the standing horse, the decision to
eye surgery. The ideal sedative should have a
perform a procedure under sedation rather than
rapid onset of action and be able to ensure
general anesthesia must be made on the basis of
immobility while allowing for patients to respond
the temperament of the horse, severity of the
to verbal commands. Furthermore, ideal
injury, and skill of the veterinarian.‖ DA Wilkie
sedatives should provide amnesia, have a 2.
sufficiently short duration of action to facilitate

patient cooperation during surgery, have minimal
Introduction
side effects and allow for a rapid return to home-
Sedation is often required to improve patient
readiness. Combined analgesic and sedative
comfort during the placement of local blocks in
regimes are widely used in tandem with
eye surgery. The ideal sedative should have a
local/regional blocks, however, potential
rapid onset of action and be able to ensure
problems with sedative/narcotic agents are
immobility while allowing for patients to respond
considerable. These complications include
to verbal commands. Furthermore, ideal
ventilatory depression and loss of airway control
sedatives should provide amnesia, have a
with hypoxia and hypercapnia, and may cause the
sufficiently short duration of action to facilitate
patient to become confused intraoperatively.
patient cooperation during surgery, have minimal
The role of sedation in a wide variety of
side effects and allow for a rapid return to home-
ophthalmic procedures as well as the variation in
readiness. Drugs used for sedation can be
sedative agents used with regards to dosage
divided into two broad categories, namely
regimes and drug combinations as applied in
anxiolytic and sedative-hypnotics. Sedative
clinical practice can only be illustrated by
hypnotics, as a class, can be further subdivided
referring to the published data. As a result, the
into benzodiazepines, barbiturates,
goal of this paper is to examine the spectrum of
antihistaminics, narcotic analgesics, and
sedative drugs that have been used in the process
intravenous anaesthetics. Combined analgesic
of eye surgery as published in the literature since
and sedative regimes are widely used in tandem
1990 with special attention being given to the
with local/regional blocks; however, potential
pharmacodynamics and clinical applications of
problems with sedative/narcotic agents are
relevant drugs in current use.
considerable. These complications include
In conclusion there does not seem to be one drug
ventilatory depression and loss of airway control
or one regime indicative of standardization of
with hypoxia and hypercapnia, and may cause the
sedation practice in eye surgery. It rather seems
patient to become confused intraoperatively.
as if there could be a competition between drugs
The role of sedation in a wide variety of
and regimes for the position of the best and most
ophthalmic procedures as well as the variation in
favourable place in the armamentarium of
sedative agents used with regards to dosage
sedationists and anaesthesiologists. There could
regimes and drug combinations as applied in
be strong indications from the literature that
6
7
clinical practice can only be illustrated by occupied, membrane hyperpolarization and
referring to the published data. As a result, the neuronal inhibition occurs. As result,
goal of this paper is to examine the spectrum of benzodiazepines have been shown to exhibit
sedative drugs that have been used in the process anticonvulsant, anxiolytic and muscle relaxant
of eye surgery as published in the literature since activity. The action of the benzodiazepines is
1990 with special attention being given to the readily reversed by flumazenil, a benzodiazepine
pharmacodynamics and clinical applications of receptor antagonist, making the benzodiazepines
relevant drugs in current use, namely propofol, the only class of sedatives that can be reversed by
midazolam, alfentanil, fentanyl, remifentanil, a specific antagonist.
ketamine, diazepam, lorazepam, methohexital,
piritramide and clonidine/dexmedetomidine. For Midazolam
sedation in combination with eye blocks, the Pharmacokinetics and pharmacodynamics
literature presents a multitude of combinations Midazolam, a water soluble bezodiazepine, has a
that are used in clinical practice viz; wide margin of safety and a high therapeutic
ketamine/alfentanil; alfentanil/midazolam; index. The elimination half-life of midazolam
propofol/ketamine; propofol/remifentanil; ranges between 2 to 5 hours while the duration of
propofol/alfentanil; propofol/fentanyl/alfentanil; action varies between 1.5 to 3.5 hours - shorter
propofol/diazepam; propofol/midazolam; than most other benzodiazepines. Although the
alfentanil/droperidol; fentanyl/droperidol; half-life of a given agent does not predict the
fentanyl/diazepam. duration of its sedative effect after a single, pre-
Combinations of drugs can be used to sedate operative dose it is important to remember that
patients in order to limit movement during the the elimination half-life is prolonged in patients
block and to provide a cooperative, alert and with cardiac, hepatic and renal impairment.
haemodynamically stable patient during the This, coupled with absence of long-acting active
operative procedure. Excessive dosage of these metabolites, makes midazolam a suitable short-
drugs however, may result in hazardous acting sedative agent that produces minimal to no
respiratory depression in this patient population residual psychomotor impairment 8 hours
particularly in the higher dose ranges. following oral doses and 3 to 4 hours following
intravenous (IV) administration. Other
SEDATIVE AGENTS: PHARMACOLOGY, advantages include minimal pain or local
DOSAGE REGIMES AND CLINICAL intolerance following intramuscular (IM) and IV
APPLICATION injection (as opposed to diazepam) due to its
water solubility. Furthermore, in contrast to
Benzodiazepines diazepam, midazolam is almost completely
Midazolam, diazepam and lorazepam are the absorbed following IM administration
most commonly used benzopdiazepines Dose
associated with eye surgery and local eye blocks. Usual doses for the induction of anaesthesia
Midazolam is the most popular mainly due to its range between 0.15 to 0.3 milligrams/kilogram
high lipid solubility, which results in a fast onset (mg/kg) given intravenously. For sedation,
of action as well as its rapid rate of clearance, however, the recommended dose of midazolam is
while diazepam and lorazepam have largely lost 0.04 mg/kg but this should only be taken as a
favour for this indication. Diazepam, due to its guide as patient response varies considerably.
slow clearance, is associated with delayed Subsequent incremental doses should be at doses
recovery particularly in large doses while, of 0.015mg/kg. It is suggested that midazolam
relative to midazolam, lorazepam has a should be injected at a rate of 2mg/min with the
comparatively slower onset of action due to its drug taking effect within approximately 1 to 1.5
lesser degree of lipid solubility. minutes following IV administration.
Pharmacology: Midazolam has been associated with both
The most widely accepted hypothesis for the respiratory depression and respiratory arrest most
mechanism of action of benzodiazepines is that often when combined with other central nervous
gamma aminobutyric acid (GABA) receptors and system (CNS) depressants. Elderly patients and
benzodiazepine receptors are coupled to a patients who have taken alcohol are more
chloride channel. When both receptors are sensitive to this drug and it is recommended to
Ophthalmic Anaesthesia News, Issue 6, June 2002 7
Email: [email protected] Website http://www.boas.org
8
reduce the maximum total dose by 30% in minutes. The elimination of diazepam is
patients over 60 years of age or debilitated biphasic with an initial half-life of 7 to 10 hours,
patients. Pharmacodynamic studies have followed by a second half-life ranging from 2 to 6
consistently shown that from the ages of 20 to 80 days. Extensive hepatic metabolism occurs to
years the sensitivity of the brain towards active metabolites with less than 25% of the drug
midazolam increases by at least 75%. As a being excreted unchanged in the urine.
result, a bolus dose of midazolam given to an 80 Clinical application
year old patient should be reduced to 25% of that In a study conducted by Hampl and colleagues 8,
intended for use in a patient who is 20 years old 3. diazepam was compared with propofol as
In cases when midazolam is intended to be used intravenous sedation for retrobulbar block and
in combination with an opiate, it should be borne eye surgery.
in mind that only 25% of the usual recommended The combination of diazepam and propofol
dose of each agent should be administered, giving resulted in the highest comfort scores for both
opiate first followed by a titration of the retrobulbar block and surgery. Diazepam alone
midazolam. 4. Metabolites of midazolam have did not produce adequate sedation for retrobulbar
substantial pharmacological activity and can block and propofol alone did not provide any
accumulate in patients with renal failure and in sedation during surgery.
patients with reduced CYP3A4/5 activity, while
clearance is reported to be 30% lower in patients Lorazepam
suffering from congestive heart failure 5. Lorazepam is a benzodiazepine derivative in
The mean dose of midazolam given alone was clinical use as a sedative-hypnotic,
1.82 ± 1.09mg. The dose given with opioids was anticonvulsant, anxiolytic, and muscle relaxant.
1.44 ± 0.84 in 19,250 for cataract operations in Usual oral doses range from 2 to 6 mg daily,
nine centers 6. divided into 2 to 3 doses; parenteral doses of 0.05
Clinical application mg/kg are recommended prior to surgical
Wong 7 studied the use of midazolam and procedures. Paediatric dosing for surgical
alfentanil separately, or in combination in elderly premedication has been 0.05mg/kg either
patients undergoing cataract surgery under parenterally or orally. In some cases, lorazepam
regional anaesthesia. The average age of 120 administered by the sublingual route may result
patients within this study was 73 years. Patients in a faster onset of therapeutic effect than orally
were randomized to receive one of normal saline, administered lorazepam. Sublingual
1mg midazolam, 500µg alfentanil, or 0.5mg administration of lorazepam also compares
midazolam plus 250µg alfentanil. The favourably in time to onset with intramuscular
midazolam-alfentanyl combination was shown to injection of the drug.
reduce pain perception while all IV sedation used Pharmacokinetics
reduced pain recall. Midazolam reduced systolic Adequate absorption occurs with oral or
blood pressure and alfentanil reduced oxygen intramuscular doses; onset of hypnosis is 20 to 30
saturation with or without midazolam. The minutes and the duration is 8 hours; protein
authors concluded that, firstly, the use of fine binding is 85% to 91%; elimination half-life is 10
needles combined with a slow infusion rate of to 16 hours; hepatic metabolism to inactive
anaesthetic solution caused minimal discomfort metabolites occurs, with renal excretion and
and secondly, that the routine IV sedation may be minimal faecal excretion.
unnecessary. Adverse effects include sedation, dizziness,
vertigo, delirium, disorientation, agitation,
Diazepam hepatotoxicity, respiratory depression, and
Pharmacokinetics withdrawal symptoms.
The onset of clinical effect following the oral Clinical application:
administration of diazepam occurs within 30 Lorazepam is an effective anti-anxiety and
minutes. Both oral and intramuscular absorption hypnotic agent for insomnia and as premedication
is rapid with peak levels occurring within 1 hour. to surgical procedures. The drug is also indicated
Rectal absorption is also rapid with adequate parenterally for status epilepticus.
serum levels occurring within 10 minutes and
finally intravenous use produces peaks within 8
Ophthalmic Anaesthesia News, Issue 6, June 2002 8
Email: [email protected] Website http://www.boas.org
9
In eye surgery lorazepam in a dose range of 0.5 particularly when the drug is administered via
to1.0 mg, particularly in the elderly, will be used the small veins on the dorsum of the hand or
sublingually as an axiolytic. wrist. Apnoea, a reduction in blood pressure,
and CNS effects are also relatively common with
Propofol propofol anaesthesia. The lipid based
Propofol is an intravenous sedative hypnotic formulation of propofol has a number of
useful in the induction and maintenance of undesirable properties which include the pain on
general anaesthesia in adults and children and for injection mentioned above as well as the
sedation during monitored anaesthesia care possibility of serious allergic reactions, and rapid
(MAC). Propofol is a hindered phenolic microbial growth with inadvertent contamination.
compound with intravenous general anaesthetic Propofol also appears to increases the incidence
properties and is unrelated to any of the of sneezing and might happen during placement
barbiturate, opioid, benzodiazepine, of the block 9.
arylcyclohexylamine, or imidazole intravenous Dose
anaesthetic agents that are used currently. The adult induction dose of propofol is usually 2
Propofol enjoys wide popularity as an agent for to 2.5mg/kg. For maintenance of anaesthesia,
sedation in eye surgery evident from the many continuous propofol infusions of 6 to 12
clinical applications referred to in the published mg/kg/hour (0.1 to 0.2 mg/kg/min) have been
literature. Low doses of propofol tend to lack used. For monitored anaesthesia care also called
analgesic properties and produce amnesia that is conscious sedation, most patients require an
unreliable. As a result, this agent is often used in infusion of 6 to 9 mg/kg/hr, with maintenance
combination with other preparations. rates of 0.3 to 3 mg/kg/hr. Higher maintenance
Pharmacokinetics doses may be required for ICU sedation.
Onset of anaesthesia usually occurs within 30
seconds of the end of the bolus infusion and the Clinical application
duration of effect last for approximately 3 to 10 It has been shown that propofol decreases
minutes depending on the dose and the rate of intraocular pressure where a propofol bolus of
administration. Propofol is highly lipophilic, has 0.5mg/kg followed by a low-dose continuous
a large volume of distribution and is 97% to 99% infusion of 0.5mg/kg/hr in patients undergoing
protein bound. The initial distribution half-life trabeculectomy under peribulbar block. Ocular
in surgical and healthy volunteers ranges from 1 pressure decreased 2 minutes after the start of the
to 8 minutes. The half-life of the initial propofol infusion and remained significantly
elimination phase is approximately 40 minutes, lower than in the control group 10. Neel and co-
while the terminal elimination phase half-life is authors published another study which examined
approximately 200 minutes. Mean recovery the effects on intraocular pressure during single
from anaesthesia (defined as the time when the low dose (0.98mg/kg SEM 0.04) intravenous
patient could obey verbal commands) was 3, 6, sedation with propofol before cataract surgery.
and 8 minutes following propofol doses of 1, 2, A decrease in intraocular pressure of between 17
and 3 mg/kg, respectively 5. The most and 27%, with minimal side effects, was shown
distinguishing property of propofol relates to its after sedation with intravenous propofol 11. It
pattern of clearance. It is rapidly bio was, however, shown that sedation techniques
transformed into inactive metabolites not only in with other agents e.g. fentanyl/droperidol and
the liver but also in multiple tissue sites yet to be alfentanil/droperidol combinations caused a
clearly defined, which provides for a rapid similar reduction in intra-ocular pressure 12. The
recovery even after prolonged administration. reduction of intra-ocular pressure is therefore not
Propofol is well suited for sedation and at these unique to propofol sedation but more likely due
low doses adverse respiratory and cardiovascular to the sedation per se.
influences are minimal. Propofol also has Rewari, et al 13 studied remifentanil and propofol
notable antiemetic efficacy and nausea and for analgesia and sedation during placement of
vomiting are less frequent when propofol is a retrobulbar block. Four groups of patients were
component of the anaesthetic regimen. randomized to receive either remifentanil 1µg/kg,
Pain on injection is listed as one of the most remifentanil 0.5µg/kg and propofol 0.5mg/kg,
common adverse effects associated with propofol remifentanil 1µg/kg and propofol 0.5 mg/kg or
Ophthalmic Anaesthesia News, Issue 6, June 2002 9
Email: [email protected] Website http://www.boas.org
10
saline 0.1ml/kg. No pain was observed during hypertonus of skeletal muscle, and bradycardia.
the placement of the block in any of the groups Acute effects are competitively antagonized by
except the control group. Respiratory depression naloxone.
was observed to the greatest degree in patients Remifentanil is structurally related to alfentanil,
receiving remifentanil 1µg/kg groups. The but is 20 to 50 times more potent and has a
combination of remifentanil 0.5µg/kg with shorter elimination half-life. In surgical
propofol 0.5mg/kg as a bolus was considered to anaesthesia, remifentanil has been given as an
provide excellent relief of pain and anxiety with intravenous bolus of 1 microgram/kilogram
least number of adverse effects being associated (µg/kg) followed by a continuous infusion of 0.1
with the placement of the block. to 0.8 µg/kg/minute; the duration of opioid
The efficacy and safety of remifentanil, propofol effects is short, requiring immediate supplemental
or both for conscious sedation during eye surgery postoperative analgesia. Dose reductions are not
under retrobulbar block was compared in a required in renal or hepatic impairment.
prospective randomized study by Holas and Pharmacokinetics
colleagues 14. Remifentanil is characterized by a rapid onset of
In another study by Yee, et al 15 propofol and the analgesia and a very short duration of action (3 to
addition of alfentanil were compared for sedation 10 minutes); the time to a 50% reduction in the
during placement of retrobulbar block for cataract effective plasma concentration of the drug is
surgery. about 3.5 minutes, significantly less than that of
Sedation quality and recovery profiles in patients alfentanil. The brief duration of action of
who received propofol or propofol-ketamine remifentanil is attributed to its rapid hydrolysis
sedation during placement of retrobulbar block by blood and tissue esterases, to essentially
were compared in a study by Frey et al 16. inactive metabolites. Most of an intravenous dose
Propofol and ketamine was also used in a study is excreted in the urine as the carboxylic acid
by Senn, et al 17 who believed that deep sedation metabolite.
is needed while injecting the local anaesthetic for Remifentanil has an elimination half-life of 8 to
the eye block. 20 minutes, shorter than that of alfentanil.
Unlike alfentanil, which is metabolized in the
Opioid analgesics/narcotics liver, remifentanil contains an ester linkage in its
In this group of agents, fentanyl, remifentanil, structure and is susceptible to rapid hydrolysis in
alfentanil and piritrimide have been used in tissues and blood by nonspecific esterases to
sedation for periorbital blocks and eye surgery. essentially inactive metabolites.
Most of these agents have been referred to in Adverse effects of remifentanil resemble those of
combination with propofol and /or midazolam 7, other opioid analgesics, and include hypotension,
13, 14, 18-26. bradycardia, central nervous system effects
Opioids are generally included in anaesthetic (sedation, dizziness, euphoria), nausea, vomiting,
regimens to provide analgesia and offset muscle rigidity, skin rash, and respiratory
sympathetic responses to surgical stimuli. depression; however, due to its rapid clearance,
Opioids have relatively little effect on pharmacologic reversal should not be required.
consciousness but can be used alone or in Clinical application
combination with other sedative agents to Remifentanil is indicated as an analgesic
improve tolerance and the level of sedation component for the induction and maintenance of
during the placement of local eye blocks. general anaesthesia for inpatient and outpatient
The most common side effects with all opioids procedures, and as an analgesic into the
are respiratory depression and hypotension within immediate postoperative period. It is also
the context of sedation for eye blocks. indicated as an analgesic component of monitored
anaesthesia care (MAC). Remifentanil is shorter-
Remifentanil acting than alfentanil and advantages of
Remifentanil is an ultrashort-acting opioid remifentanil are easy titration of intraoperative
analgesic for use during surgical anaesthesia. It is opioid effects, no accumulation during prolonged
selective for mu receptors and exhibits typical infusion, minimal risk of significant postoperative
opioid pharmacologic effects, including respiratory depression, and lack of dependence
analgesia, respiratory depression, sedation, upon hepatic metabolism.
Ophthalmic Anaesthesia News, Issue 6, June 2002 10
Email: [email protected] Website http://www.boas.org