Effect of dexmedetomidine premedication on the intraocular pressure changes after succinylcholine an

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Effect of dexmedetomidine premedication on the
intraocular pressure changes after
succinylcholine and intubation
BJA British Journal of Anaesthesia

• British Journal of Anaesthesia 100 (4) 4859
  (2008) February 19, 2008
• 2008.04.08 presentation ???

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Background

• Anaesthesia for patients with open globe injury
  who need emergency surgery may be hazardous.
• Factors ? the intraocular pressure (IOP) may
  drain the aqueous humour or extrude the vitreous
  humour via the wound, which damage vision
  permanently.

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Background

• Succinylcholine is still recommended for some
  situations in open globe injuries.
• However, the use of succinylcholine is associated
  with an ? intraocular pressure (IOP).
• This may be deleterious in open globe injuries.
  No method has previously been shown to abolish
  completely this rise in the IOP.
• We investigated whether dexmedetomidine, an
  alpha-2 agonist, could attenuate this increase in
  the IOP after succinylcholine and intubation.

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Succinylcholine

• Facilitate rapid tracheal intubation in high-risk
  patients for aspiration because of its fast onset
  time and excellent intubating conditions.
• It is, however, associated with an increase in
  the IOP.
• Durant NN, Katz RL. Suxamethonium. Br J Anaesth
  1982 54 195208
• Edmondson L. Intraocular pressure and
  suxamethonium. Br J Anaesth 1997 79 146

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Dexmedetomidine

• Highly selective alpha-2 adrenergic agonist that
  has sedative and analgesic effects.
• Dexmedetomidine an updated review. Ann
  Pharmacother 2007 41 24552
• Intraoperative use of alpha2- adrenoceptor
  agonists. Best Pract Res Clin Anaesthesiol 2000
  14 33545

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Method

• Informed consent
• 40 adult patients of ASA I or II.
• Elective non-ophthalmic surgeries
• General anaesthesia

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Exclusion

• gt 60 yr
• Body weight more than 150 ideal body weight
  using Brocas index
• acute or chronic Eye disease
• Contraindication to the study drugs
• Receiving any medication known to alter IOP.

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www.randomizer.org

• 2 equal groups (20 patients each)
• Receive single bolus i.v. dose of dexmedetomidine
  (dexmedetomidine group)
• Saline (control group)

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Method

• 40 patients with no pre-existing eye disease
  undergoing general anaesthesia were randomly
  premedicated by i.v. dexmedetomidine 0.6 mcg/kg,
  or saline.
• Heart rate (HR), mean arterial pressure (MAP),
  and IOP (using Schioetz tonometer) were measured
• Before premedication
• after premedication
• after thiopental,
• after succinylcholine,
• immediately after intubation,
• and then every 2 min for 6 min.

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Monitoring

• Standard monitoring including ECG, pulse
  oximeter, capnometry, and non-invasive arterial
  pressure.
• (Datex-Ohmeda S/5, ADU, Sweden).
• IOP was measured with a Schioetz tonometer by an
  ophthalmologist
• (For this procedure, topical oxybuprocaine
  hydrochloride 0.4 (BNX) was applied to the
  cornea before measurement.)

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Premedication

• Diluted 1 ml Dexmedetomidine 100 mg/ml with 49 ml
  normal saline to a concentration of 2 mg/ml.
• Syringes containing solutions of either
  dexmedetomidine or saline were done in a
  Doubleblind fashion by a team member who was not
  in data recording.
• Before induction, a single dose of
  dexmedetomidine 0.6 mg/kg was administered
• i.v. syringe pump (Life Care 5000 Infusion
  System, Abbot) over 10 min.
• Saline was given in the control group using the
  same pump.

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Anaesthesia was standardized

• Preoxygenation for 3 min,
• induced with thiopental 5 mg/kg fentanyl 1
  mg/kg.
• Succinylcholine 1.5 mg/kg.
• When the fasciculations had ceased, tracheal
  intubated under direct vision laryngoscopy
• correct position of the tracheal tube was
  verified by auscultation of the chest and by
  capnometry.

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• failed intubation at the 1st try, the patient was
  excluded.
• Rocuronium provided the intraoperative
  neuromuscular block.
• Anaesthesia was maintained with sevoflurane in a
  mixture of oxygen and air.
• Fluid administration of lactated Ringer solution
  was standardized at 4 ml/kg/h.
• If hypotension (MAP 30 from the baseline) or
  bradycardia (HR,40 beat/min) occurred, it was
  recorded and managed according to the preference
  of the attending anaesthetist.

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• Mean arterial pressure (MAP), heart rate (HR),
  and IOP were recorded at the following time
  points
• T1 5 min after arrival to OR, before
  premedication (baseline).
• T2 10 min after premedication.
• T3 30 s after thiopental.
• T4 30 s after succinylcholine.
• T5 immediately after intubation.
• T68 every 2 min for 6 min after intubation.

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Results
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Heart Rate

• No significant differences in HR between the two
  groups were recorded at any time.
• HR ? significantly after injection of thiopental,
  succinylcholine, intubation in control group.
• These ? in HR were not observed in the
  dexmedetomidine group.

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Mean Arterial Pressure

• The MAP increased significantly compared with the
  preoperative value after intubation in the
  control group and was significantly higher than
  the MAP in the dexmedetomidine group (P0.041).
• In the dexmedetomidine group, the MAP was not
  significantly higher than the preoperative value
  at all times.
• No incidence of hypotension or bradycardia
  requiring intervention was reported in both
  groups.

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Intraocular Pressure

• There was no significant difference in the
  baseline IOP between both groups.
• After dexmedetomidine injection, there was a
  significant decrease in IOP, compared with
  baseline (P0.017).
• Thiopental decreased IOP significantly in both
  groups (Plt0.001).
• Succinylcholine and intubation increased IOP in
  both groups. However, IOP in the dexmedetomidine
  group after intubation was not significantly
  different from that at baseline (P0.65), unlike
  that in the control group (Plt0.001).

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Results

• Succinylcholine and intubation increased IOP in
  both groups.
• However, in the dexmedetomidine group, the IOP
  rise was not different from the baseline value
  (P0.65) and was significantly lower than in the
  saline group (P0.003).
• After intubation, the MAP in the control group
  was higher than that in the dexmedetomidine group
  (P0.041) and exceeded the baseline value
  (Plt0.001).
• The HR also showed less fluctuation in the
  dexmedetomidine group than in the saline group.

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Disscusion

• The main finding was that premedication with a
  dose dexmedetomidine 0.6 mg/kg over 10 min
  blunted the ?IOP caused by succinylcholine
  intubation.
• Attenuated the haemodynamic response to
  laryngoscopy intubation.

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• Dexmedetomidine intraocular hypotensive effect is
  consistent with previous researches on alpha-2
  agonists.
• Clonidine was effective in preventing the rise of
  the IOP in response to succinylcholine tracheal
  intubation.
• The effects of clonidine on intraocular pressure,
  perioperative hemodynamics and anesthetic
  requirements. Anesthesiology 1988 68 70716
• Oral clonidine premedication for elderly patients
  undergoing intraocular surgery. Acta Anaesthesiol
  Scand 1992 36 15964

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• Dexmedetomidine infusion adjunct to local
  analgesia in ophthalmic surgery was effective in
  ? IOP significantly.
• Dexmedetomidine during local anesthesia. J Anesth
  2006 20 546
• Intramuscular Dexmedetomidine reduces IOP in
  elderly during cataract surgery. (1.0mcg/kg) ?32
  IOP.
• Dexmedetomidine as intramuscular premedication in
  outpatient cataract surgery a placebo-controlled
  dose-ranging study. Anaesthesia 1993 48 4827

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• Single i.v. dose of dexmedetomidine 0.6 mcg/kg ?
  IOP by 34.
• The present study (0.6 mcg/kg) was based on a
  previous clinical study, where the selected dose
  resulted in a significant ? IOP and prevented IOP
  response to intubation.
• Dexmedetomidine attenuates sympathoadrenal
  responses to tracheal intubation and reduces the
  need for thiopental and perioperative fentanyl.
  Br J Anaesth 1992 68 12631

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• Lee and colleagues infused dexmedetomidine as a
  supplement to isoflurane anaesthesia, they found
  no IOP lowering effect.
• Dexmedetomidine infusion as a supplement to
  isoflurane anaesthesia for vitreoretinal surgery.
  Br J Anaesth 2007 98 47783
• But, the loading dose of dexmedetomidine used in
  their study was lower. (0.4 mcg/kg)

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mechanism

• Dexmedetomidine on IOP effect may be due to
  direct vasoconstrictor effect on the afferent
  vessels of the ciliary body, which ? aqueous
  humour production.
• Macri FJ, Cervario SJ. Clonidine. Arch Ophthalmol
  1978 96 21113
• Dexmedetomidine ? outflow of the aqueous humour
  by reduce sympathetically mediated vasomotor tone
  of the ocular drainage system.
• Dexmedetomidine-induced ocular hypotension in
  rabbits with normal or elevated intraocular
  pressures. Invest Ophthalmol Vis Sci 1992 33
  201923
• Additionally, its associated haemodynamic
  response could contribute to the IOP lowering
  effect.
• Sufentanil or clonidine for blunting the increase
  in intraocular pressure during rapid-sequence
  induction. Eur J Anaesthesiol 2002 13 51922

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non-depolarizing neuromuscular blocking agents

• Use of succinylcholine in open ocular trauma is
  controversial and an alternative anaesthetic
  management based on the use of nondepolarizing
  neuromuscular blocking agents, despite its slower
  onset, was suggested.
• Various methods have been tried to speed up this
  onset, including priming, administering the
  non-depolarizing relaxant before the induction
  agent, and high-dose regimen.
• J Clin Anesth 2004 16 837
• Br J Anaesth 2007 98 60410

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non-depolarizing neuromuscular blocking agents

• Despite these strategies, non-depolarizing
  neuromuscular blocking agents can still result in
  non-ideal intubation conditions -
• increases in the IOP from mask application and
• longer time with insecure airway and
• prolonged paralysis.
• Despite this debate about the use of
  succinylcholine in open globe injury, most
  authors still agree on its use in difficult
  airway cases with salvageable eye situations.
• Succinylcholine and the open eye. Ophthalmol Clin
  North Am 2006 19 27985

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Limitations

• Effect of dexmedetomidine on the IOP changes
  after succinylcholine intubation cannot be
  isolated from its action on the haemodynamics,
  since both effects are parallel and a causal
  relationship.
• But, this limitation should not decline the
  advantage of dexmedetomidine to obtund the IOP
  changes of succinylcholine and intubation.

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Conclusions

• ? of IOP with succinylcholine endotracheal
  intubation can be blunted with i.v.
  dexmedetomidine premedication.
• The haemodynamic stability is an additional
  advantage.
• Dexmedetomidine could be a beneficial
  premedication in open globe injuries.

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End of presentation

• Thank you for your attention.

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• Dexmedetomidine premedication administered in the
  present study (0.6 mcg/kg) was based on a
  previous clinical study, where the selected dose
  resulted in a significant reduction in IOP and
  prevented the rise in the IOP in response to
  intubation.
• Dexmedetomidine attenuates sympathoadrenal
  responses to tracheal intubation.
• Br J Anaesth 1992 68 12631

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• Several previous studies have reported the
  blunting effect of dexmedetomidine on the
  sympathetic response to laryngoscopy and
  intubation.
• Hemodynamic and anesthetic advantages of
  dexmedetomidine, an alpha2-agonist, for surgery
  in prone position. Tohoku J Exp Med 2006 210
  15360
• This could be due to the centrally mediated
  sympatholytic effects of alpha-2 agonists and by
  its decreasing norepinephrine release via
  peripheral presynaptic alpha-2 receptors.