Transcript Anesthetic management for strabismus surgery

Anesthetic management for
strabismus surgery
• Associated neurological abnormalities
include:
cerebral palsy, myelomeningocele,
hydrocephalus, craniofacial syndromes,
neurofibromatosis, seizure disorders structural
abnormalities of the eye
• In the preanesthetic evaluation, it is important
to consider diseases or syndromes associated
with strabismus, such as congenital heart
disease or cardiomyopathy, as each has its
specific anesthetic considerations that are
important to review
Malignant hyperthermia,
masseter muscle spasm
• Patients with MH were noted as having a higher
incidence of musculoskeletal abnormalities, such
as strabismus or ptosis
• A review of more than 2,500 patients tested for
MH susceptibility was unable to show an
association with strabismus surgery patients
• Children with strabismus are now routinely
anesthetized with inhalational anesthetics
without any apparent increase in the incidence of
MH
• fourfold incidence of MMS in pediatric strabismus
patients compared with nonstrabismus patients
after a halothane induction followed by a single
dose of succinylcholine
• The ‘‘jaws of steel’’ represents a clinical state
during which the mandible cannot be displaced
from the maxilla to facilitate insertion of any
airway
• Some suspect that certain cases of MMS may be
a normal response to succinylcholine
• Summary:
• Association between strabismus and MH is no
longer an issue; however, if MMS is suspected
in a patient, it is important to recognize that
this patient may be susceptible to MH
• The importance of a detailed anesthetic family
history is emphasized
• Oculocardiac reflex
• Definition:
• 20% decrease in heart rate(HR) from baseline,
dysrhythmias, or sinoatrial arrest associated
with ocular muscle traction
• 10-30% decrease in HR from baseline
• It is a trigeminal-vagal reflex that can lead to a
variety of arrhythmias, including sinus
bradycardia, junctional rhythm, atrial ectopic,
atrioventricular block, ventricular bigeminy,
wandering pacemaker, multifocal premature
ventricular contractions, idioventricular
rhythm, ventricular tachycardia, or asystole
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Incidence :
14-90% depending on:
administration of an anticholinergic,
the choice of anesthetic agents,
the definition of OCR used
• Triggers
• 1:traction on the extraocular muscles
• 2: pressure on orbital structures or on the
tissue remaining in the orbital apex after
enucleation,
• 3: ocular trauma
• 4: increase in intraorbital pressure from an
injection or hematoma
• The response generally disappears as the
stimulation is discontinued
• This phenomenon is called vagal escape or
OCR fatigue
• It is a physiologic defense mechanism where
the HR response diminishes after sustained or
repeated extraocular muscle manipulation
• Oculorespiratory reflex:
• Reduction in tidal volume and respiratory rate
• The afferent pathways are the same as in OCR,
but they are directed to the respiratory control
area of the brainstem instead, and the efferent
fibers travel along the phrenic nerve and other
nerves involved in respiration
• The oculorespiratory reflex may produce
hypercapnia and hypoxemia that can increase the
incidence of OCR
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Prevention of OCR:
surgical manipulation must be gentle,
depth of anesthesia must be adequate,
hypoxia and hypercarbia must be avoided
Administering atropine or glycopyrrolate
decreases the incidence of OCR
• systematic prophylactic anticholinergic
administration remained controversial in the
past because it was associated with
ventricular arrhythmias
• the incidence of OCR is affected significantly
by the type of anesthetic administered
• Treatment:
• The initial response to OCR is to ask the surgeon
to stop surgical manipulation immediately,
• Assess the patient’s ventilatory status to rule out
hypercarbia or hypoxia
• Evaluate the depth of anesthesia
• Atropine should be administered if hemodynamic
instability or arrhythmias occur as a result of
bradycardia
• Postoperative nausea and vomiting:
• Incidence of PONV without prophylaxis varies
from 37-90%
• Complications: dehydration, electrolyte
imbalance, subconjunctival hemorrhage,
loosening of surgical attachments, delayed
discharge, unplanned admissions, decrease
satisfaction, increase the use of resources
• Major risk factors:
• General:The type of surgery (e.g., strabismus surgery,
tonsillectomy), age>three years, duration of
anesthesia>30 min, and a personal or family history of
POV, PONV, or motion sickness
• Specific: oculoemetic reflex, alteration in visual
perception postoperatively, positive OCR, the surgical
technique, and the number of repaired eye muscles
• The surgical technique, myopexy, where posterior
fixation of the muscle via a suture results in a more
sustained stimulation, is associated with an increased
incidence of PONV
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Treatment:
Droperidol 75mic.kg.IV
Dexamethasone : 50 mic.kg.IV
Ondansetron: 0.05-0.2 mg.kg.IV
Combination anti-emetic therapy
• Factors affecting the incidence of the
oculocardiac reflex:
• Increase: Propofol, Light anesthesia,
Hypercarbia, Hypoxia, Traction on extraocular
muscles, Stimulation of orbital structures,
Halothane>sevoflurane,
Remifentanil>sevoflurane, Desflurane
• Deacrease: Anticholinergics, Ketamine,
Midazolam, Rocuronium
• No effect: Sevoflurane = desflurane,
Spontaneous ventilation, Controlled
ventilation
• Analgesia:
• 1: Opioids: fentanyl, meperidine, Remifentanil
• 2: Topical analgesics: topical tetracaine, topical
diclofenac; low incidence of PONV
• 3: Blocks: Regional blocks
Malignant Hyperthermia
• Genetic counseling: Malignant hyperthermia
susceptibility (MHS) is inherited in an
autosomal dominant manner
• pharmacogenetic disorder of skeletal muscle
calcium regulation associated with
uncontrolled skeletal muscle hypermetabolism
• Manifestations of malignant hyperthermia
(MH) are precipitated by certain volatile
anesthetics :halothane, isoflurane,
sevoflurane, desflurane, enflurane, either
alone or in conjunction with depolarizing
muscle relaxants (succinylcholine)
• The triggering substances release calcium
stores from the sarcoplasmic reticulum,
causing contracture of skeletal muscles,
glycogenolysis, and increased cellular
metabolism, resulting in production of heat
and excess lactate
• Affected individuals experience: acidosis,
hypercapnia, tachycardia, hypoxemia,
rhabdomyolysis with subsequent increase in
serum creatine kinase (CK) concentration,
hyperkalemia with a risk of cardiac arrhythmia
or even arrest, and myoglobinuria with a risk
of renal failure
• the first manifestations of MH, tachycardia
and tachypnea, occur in the operating room;
however, MH may also occur in the early
postoperative period
• Diagnosis/testing: In vitro measurement of
contracture response of biopsied muscle to
graded concentrations of caffeine and the
anesthetic halothane
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Management:
Treatment of manifestations:
Early diagnosis of MHS
Discontinuation of potent inhalation agents
and succinylcholine
• Treatment of metabolic abnormalities
• Administration of dantrolene sodium
intravenously
• Prevention of primary manifestations:
avoidance of potent volatile anesthetic agents
and succinylcholine