SUCCINYLCHOLINE/LARYNGOSCOPY
| SUCCINYLCHOLINE AND THE OPEN EYE —Elie Joseph Chidiac, MD, Vice Chair for Education, Wayne
State University School of Medicine, and Director of Anesthesia, Kresge Eye Institute, Detroit Medical Center,
Detroit, MI |
| Intraocular pressure (IOP): spectrum (increases in prone position vs standing position; also increases in daytime
vs nighttime); flow of aqueous humor major determinant (production of ciliary process; elimination
through Schlemm’s canal and angle of Fontan); choroidal blood volume other determinant (autoregulated; related
to systolic blood pressure [BP] and central venous pressure [CVP]); sudden changes in systolic BP or
CVP affect choroidal blood volume; requires time to readjust
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| Effects of anesthetics on IOP: all induction agents, except ketamine, decrease IOP; but other intraoperative
events detrimental to IOP (eg, hypoxia, intubation, coughing, bucking, vomiting, mask pressure, forceful
blinking, hypoventilation [relationship between choroidal blood volume and CO2 tension not autoregulated])
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| Succinylcholine and IOP: succinylcholine called “ideal muscle relaxant” when introduced in 1952; quickly
followed by report in German literature of increased IOP; Lincoff study followed with anecdotal reports of
aqueous and vitreous extrusion in patients given succinylcholine; Dillon study also showed similar results in
open-eye injuries; succinylcholine appeared hazardous under light anesthesia; Libonati review of studies in
1985 found no eye complications from succinylcholine; one follow-up letter to editor confirmed safety of succinylcholine,
but another letter reported loss of vitreous and enucleation
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| IOP increase with succinylcholine: sudden transient increase ≈1 min after administration of succinylcholine;
duration 10 to 12 min; IOP may increase ≤10 mm Hg; several possible mechanisms proposed, including tonic
contraction of extraocular muscles, choroidal vascular dilation, and decrease in drainage secondary to elevated
CVP; 2 studies showed that, even after extraocular muscles detached, IOP increased after succinylcholine
administration; inappropriately timed or inappropriately performed induction can cause greater rise in
IOP than succinylcholine alone; increase in IOP from succinylcholine inconsequential if optimal intubating
conditions not provided
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| Alternatives to succinylcholine: “fraught with problems”; priming—small priming dose alone can cause
partial paralysis and loss of airway control; administering neuromuscular agent before induction agent—
results in delay in intubation and longer time with airway unprotected; possibility of awareness; high-dose
regimens—effective using vecuronium and rocuronium; may result in delay in intubation and prolonged duration
of action; risks include nonideal intubating conditions at 45 sec, longer time with unprotected airway,
and prolonged paralysis after administering drug
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| Succinylcholine after pretreatment: self-taming (small dose of succinylcholine initially, followed by remaining
amount of succinylcholine) ineffective; questions about effectiveness of precurarization; lidocaine, narcotics,
nifedipine, nitroglycerin, metoprolol, and propranolol do help
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| Protocol at Kresge Eye Institute: 2 questions asked before decision about use or avoidance of succinylcholine;
1) is airway difficult or easy? (assess airway using, eg, Mallampati classification, submental distance); if
airway easy, succinylcholine can be avoided (do not use regional anesthesia either; use vecuronium, cisatracurium,
or rocuronium); 2) if difficult airway, question ophthalmologist about viability of eye; if eye not viable,
speaker prefers awake fiberoptic laryngoscopy; if eye viable, speaker prefers succinylcholine; start with
above drugs that attenuate IOP increase; succinylcholine used for rapid recovery of muscle power (able to
bring patient back to spontaneous respiration as quickly as possible)
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| Summary: succinylcholine use declining, “but we have yet to find another muscle relaxant that can be called
ideal”; balance of risk and timing; in situation of difficult airway and viable eye, succinylcholine should be
used, not another muscle relaxant
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| LARYNGOSCOPY: MAXIMIZING BENEFIT, MINIMIZING RISK —Randolph H. Hastings, MD, Associate
Professor of Anesthesiology, University of California, San Diego, School of Medicine; Staff Physician, Veterans
Affairs San Diego Healthcare System, San Diego, CA
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| Introduction: laryngoscopy procedure for exposing vocal cords and inserting endotracheal tube, securing airway,
ensuring ventilation, and maintaining gas exchange; key component of general anesthesia, critical care,
and emergency medicine; failure to secure airway, ventilate, and maintain oxygenation can result in significant
morbidity and costly claims against anesthesia provider
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| Benefits of laryngoscopy: intrinsic to procedure; able to secure airway rapidly; inexpensive; portable; possibly
more secure than other methods (eg, blind nasal intubation); able to “see where the tube’s going to go”; opportunity
to look at other pathology in upper airway and larynx
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| Risks of laryngoscopy: difficult or failed intubation; oral and dental trauma; aspiration (occasionally in setting
of full stomach or incompetent lower esophageal sphincter); laryngospasm and bronchospasm due to
stimulation
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| Difficult intubation: difficult laryngoscopy defined as grade III or grade IV laryngeal view of vocal cords; incidence
1% to 10% in various studies; difficult intubation less frequent; American Society of Anesthesiologists
(ASA) defines difficult intubation as procedure that requires ≥3 attempts or takes >10 min; failed
intubation even less frequent (<0.1%)
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 | Difficult intubation: include increased respiratory and hemodynamic compromise, hypoxemia, aspiration, and
cardiac arrest; closed claims analysis of airway-related injury found increased chance of death or brain damage;
airway events responsible for ≈30% of deaths attributed to anesthesia; oral and dental trauma also frequent
cause of claims against anesthesia providers; incidence of dental trauma depends, to large extent, on
patient circumstances; actual injuries may be higher than detected by anesthesia provider in postoperative
visits or reported by patient; dental examination may find changes in ≈10% of patients
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| Dental trauma: chipped or broken tooth (cosmetic defect; may also be associated with pain and problems eating);
tooth lodged in airway (upper airway causing severe airway obstruction or inability to ventilate; lower
respiratory tree causing gas exchange abnormalities, infection, or abscess); final consequence in both areas
can be large financial impact
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| Strategies to manage risk
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| Avoid risk: involves identifying patient most likely to suffer insult; modify plan to minimize adverse outcomes
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| Control damage: if difficulty suspected, have rescue plan to avoid negative outcome; minimize effects of adverse
event; reduce losses due to event
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Dental Injuries
| Anatomy: basic components of tooth include crown and root (anchors tooth in alveolar bone [mandible or
maxilla]); other parts include enamel, dentine, cementum, and periodontal ligament (connective tissue structure);
fibers in root oriented in predominantly horizontal direction; provides hammock-type mechanism for
supporting tooth during downward pressure; less protection from movement or dislodgement with lateral
force
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| Laryngoscopy: when first entering mouth, blade comes into close proximity to maxillary teeth; once laryngoscope
in position, goal to put upward and forward lift on laryngoscope to lift epiglottis away; if achieved,
blade moves away from maxilla, and teeth safe; tendency to rock laryngoscope handle backwards brings
laryngoscope blade up against teeth (lateral force); forces that laryngoscope exerts on maxillary incisors significantly
less than during normal chewing (force that dental hygienist puts on teeth during cleaning approximately
same as laryngoscopy)
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| Laryngoscopy, intubation, history of difficulty, and limited neck motion: intubation causes significant increase
in risk; other risk from biting on oral airway or damaging diseased tooth; 89 times greater risk for
dental injury during general anesthesia; teeth clenching also poses considerable threat; condition of teeth
big factor in whether person has risk for injury
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| Tooth abnormalities: children at particular risk due to lack of firmly established root to hold teeth in place
(possible to damage permanent teeth by hitting deciduous teeth; problem unknown until months after event;
if patient suspects earlier trauma, blame may be placed on anesthesia provider); when performing laryngoscopy
in children, use caution and document “that you were off the teeth”; worst period ≈2 yr of age (permanent
tooth bud beginning to develop; most vulnerable to insults); caries, periodontal disease, and dental
prostheses also increase risk; cavities cause loss of structural components of tooth; consequently, tooth becomes
brittle, weak, and more likely to crack or break; periodontitis loosens teeth due to inflammation; begins
as gingivitis (inflammation of gums; due to bacteria and plaque that develop around lower parts of
teeth between crown and gums); factors that make tooth vulnerable after bone loss include loss of horizontal
fibers from periodontal ligament and longer moment arm (resulting in greater torque); progressive bone
loss leads to progressively more vulnerable teeth
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| Risk avoidance: ask about previous dental work, condition of teeth, predisposing medical factors (eg, patient
with AIDS, Down syndrome, or various metabolic disorders more likely to have periodontal disease; patient
with diabetes and various connective tissue diseases more likely to have cavities); upper incisors involved in
≈66% of injuries during laryngoscopy (close to flange on laryngoscope); other upper teeth involved in ≈25%
of injuries; lower teeth <10% risk for damage; 33% risk for damage to lower teeth for things other than laryngoscopy
(eg, biting down on bite block); airway examination also indicates patient who has risk to teeth (factors
include oral view, jaw mobility, and full range of mobility in neck); patient with loose tooth may allow
prophylactic removal of tooth (may require antibiotic coverage; chance of bleeding from gums); avoid if patient
requires heparin for cardiac procedure or possibly even vascular procedure; use regional anesthesia to
avoid dental problems; if teeth at risk, avoid placing hard objects in mouth; mouth guards protect teeth during
laryngoscopy (spreads force over larger area; occupy more space; may make laryngoscopy more difficult); if
necessary, change intubation technique (eg, fiberoptic or nasal intubation; alternative laryngoscope blades either
lack flange or have specific angulation to create greater space between metal and teeth); good communication
with patient important; document discussion and if necessary, special plan to protect teeth; if
successful, document that as well; record condition of teeth at key steps (eg, during laryngoscopy, upon entering
and leaving postanesthesia care unit [PACU]); if injury occurs, have dentist in as soon as possible; after
anesthetic, talk in detail with patient about what has happened; involve risk management to marshall support
for patient
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Educational Objectives
| The goal of this program is to educate the participant about succinylcholine and the open eye and about laryngoscopy.
After hearing and assimilating this program, the listener will be better able to:
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| 1. Explain the effects of anesthetics on intraocular pressure (IOP).
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| 2. Discuss possible mechanisms for IOP increase with the use of succinylcholine.
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| 3. Review alternatives to succinylcholine in open-eye injuries.
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| 4. Discuss the benefits and risks associated with direct laryngoscopy.
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| 5. Summarize the risk factors for dental injuries in direct laryngoscopy and suggested precautions to avoid
them.
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Discussed on This Program
Alfentanil HCl [Alfenta]
Atracurium besylate [Tracrium]
Cisatracurium besylate [Nimbex]
Fentanyl citrate [Sublimaze]
Heparin sodium injection
Ketamine HCl [Ketalar]
Lidocaine HCl (several trade names)
Metoprolol succinate [Lopressor, Metoprolol Tartrate, Toprol XL]
Mivacurium chloride [Mivacron]
Nifedipine (several trade names)
Nitroglycerin (several trade names)
Propofol [Diprivan]
Propranolol HCl [Inderal, Inderal LA, InnoPran XL]
Remifentanil HCl [Ultiva]
Rocuronium bromide [Zemuron]
Succinylcholine chloride [Anectine, Anectine Flo-Pack, Quelicin]
Thiopental sodium [Pentothal]
Tubocurarine chloride
Vecuronium bromide [Norcuron]
Suggested Reading
Benumof JL: Difficult laryngoscopy: obtaining the best view. Can J Anaesth 41:361, 1994; Chidiac EJ et
al: Succinylcholine and the open eye. Ophthalmol Clin North Am 19:279, 2006; Chidiac EJ: Succinylcholine
and the open globe: questions unanswered. Anesthesiology 100:1035, 2004; Chiu CL et al: Effect of rocuronium
compared with succinylcholine on intraocular pressure during rapid sequence induction of anaesthesia. Br
J Anaesth 82:757, 1999; Dillon JB et al: Action of succinylcholine on extraocular muscles and intraocular
pressure. Anesthesiology 18:44, 1957; Domino KB et al: Airway injury during anesthesia: a closed claims
analysis. Anesthesiology 91:1703, 1999; Edmondson L: Intraocular pressure and suxamethonium. Br J Anaesth
79:146, 1997; Georgiou M et al: Sufentanil or clonidine for blunting the increase in intraocular pressure
during rapid-sequence induction. Eur J Anaesthesiol 19:819, 2002; Kelly RE et al: Succinylcholine increases
intraocular pressure in the human eye with the extraocular muscles detached. Anesthesiology 79:948, 1993;
Lee J et al: The Callander laryngoscope blade modification is associated with a decreased risk of dental contact.
Can J Anaesth 51:181, 2004; Libonati MM et al: The use of succinylcholine in open eye surgery. Anesthesiology
62:637, 1985; Lincoff HA et al: The effect of succinylcholine on intraocular pressure. Am J
Ophthalmol 40:501, 1955; McGoldrick KE: The open globe: is an alternative to succinylcholine necessary? J
Clin Anesth 5:1, 1993; Owen H et al: Dental trauma associated with anaesthesia. Anaesth Intensive Care
28:133, 2000; Shiga T et al: Predicting difficult intubation in apparently normal patients: a meta-analysis of
bedside screening test performance. Anesthesiology 103:429, 2005; Vachon CA et al: Succinylcholine and
the open globe. Tracing the teaching. Anesthesiology 99:220, 2003; Vinik HR: Intraocular pressure changes
during rapid sequence induction and intubation: a comparison of rocuronium, atracurium, and succinylcholine.
J Clin Anesth 11:95, 1999; Warner ME et al: Perianesthetic dental injuries: frequency, outcomes, and risk
factors. Anesthesiology 90:1302, 1999.
Faculty Disclosure
In adherence to ACCME guidelines, the Audio-Digest Foundation requests all lecturers to disclose any significant
financial relationship with the manufacturer or provider of any commercial product or service discussed.
For this issue, the faculty reported nothing to disclose.
Dr. Chidiac was recorded at the 19th Annual Scientific Meeting, presented September 23-25, 2005, by the
Ophthalmic Anesthesia Society and held in Chicago, IL; Dr. Hastings, at Anesthesiology Update 2006, presented
January 11-14, 2006, by the University of California, San Diego, School of Medicine and held in San Diego,
CA. The Audio-Digest Foundation thanks the speakers and the sponsors for their cooperation in the
production of this program.
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