The Dose of Succinylcholine in Morbid Obesity

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The Dose of Succinylcholine in Morbid Obesity

• Anesthesia and Analgesia 2006102438 42
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Introduction

• Succinylcholine (SCH) has been used for more than
  50 years.
• Its rapid onset and short duration
• SCH an excellent choice for morbidly obese
  patients because hemoglobin desaturation occurs
  rapidly after apnea.
• The appropriate intubating dose of SCH in obese
  patients is unknown.

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Methods

• We studied 45 morbidly obese (body mass index
  (BMI) 40 kg/m2) adults scheduled for elective
  laparoscopic gastric bypass surgery
• ASA class II and III. No neuromuscular disease,
  normal hepatic and renal function.
• Severe gastroesophageal reflex disease and those
  problematic tracheal intubation (Mallampati score
  III or IV and a large neck) were excluded.

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Methods
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Methods

• Premedication midazolam, 2 mg IV.
• Pre-oxygenation lungs was demonstrated by an
  end-tidal oxygen concentration 90 for 3 min.
• General anesthesia was then induced with fentanyl
  IV, 3 ug/kg lean body weight (LBW), and propofol
  IV, 2.5 mg/kg LBW.
• An accelerometer was taped to that thumb, and the
  response to ulnar nerve stimulation of the
  adductor pollicis muscle at the wrist was
  recorded using the TOF-Watch SX Acceleromyograph

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Methods

• Patients were assigned to one of three study
  groups.
• Group I received SCH 1 mg/kg ideal body weight
  (IBW)
• Group II received 1 mg/kg LBW.
• Group III received 1 mg/kg total body weight
  (TBW).
• IBW 22 x H m2. For morbidly obese patients, LBW
  was estimated as 130 IBW

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Methods

• The trachea was intubated when after two
  consecutive stimuli, no further decrease in
  twitch height was observed.
• Laryngoscopy conditions were scored based on the
  guidelines of the Consensus Conference on Good
  Clinical Research Practice
• Conditions were rated as (a) excellent, (b) good,
  (c) poor.

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Methods

• The recovery from neuromuscular block was
  recorded for 20 min, during which time the
  patient received no additional muscle relaxants.
• The incidence and degree of fasciculation after
  SCH administration were recorded. scored as
  absent (no fasciculation), mild
  (fibrillations),or gross (fasciculations).
• Each patient was interviewed on postoperative Day
  1 to determine the incidence of myalgias

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Results
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Results
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Results
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Results
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Discussion

• It is important to establish a safe, secure
  airway in the morbidly obese patient undergoing
  general anesthesia, because hemoglobin can
  desaturate rapidly once the patient is paralyzed
  for intubation.
• Its rapid onset and relatively short duration of
  action, is an excellent choice for tracheal
  intubation in obese patients.

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Discussion

• In average weight patients, TBW approximates IBW
  95 of average weight patients, intubating
  conditions are satisfactory with SCH 0.5 0.6
  mg/kg TBW
• In morbidly obese patients, TBW is much heavier
  than IBW. the level of plasma pseudocholinesterase
  activity and the volume of extracellular fluid
  determine the duration of action of SCH, and both
  of these factors are increased in obesity.
• it is postulated that morbidly obese patients may
  have larger absolute SCH dose requirements than
  average weight patient

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Discussion

• The onset time to maximum block (based on IBW,
  LBW, or TBW) in all study groups was
  approximately 90 s. However, maximum block was
  only 93 of control in Group I, compared with 99
  in Group II and 100 in Group III.
• All tracheas were intubated successfully. Group
  III good to excellent. Group I poor 33. Group
  IIpoor, 27.

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Discussion

• Time to recovery (50 of twitch height ). Group
  I5 min, Group II7 min, Group III 8.5 min.
• If difficulty is encountered with laryngoscopy
  and mask ventilation
• It was suggested that SCH (0.5 mg/kg TBW) would
  provide adequate conditions while allowing for a
  more rapid return of spontaneous breathing and
  airway reflexes

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Discussion

• The hemoglobin of an apneic morbidly obese
  patient will desaturate to hypoxemic levels in
  34 min, whereas an average-weight patient has
  810 min before hypoxemia develops.
• Decease dose of SCH provide lessthan- optimal
  intubating conditions without protecting the
  morbidly obese patient from hypoxemia

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Discussion

• Decrease dose of SCH ? postoperative myalgias
• The incidence of postoperative nonincisional pain
  in our study was almost nonexistent, and no
  patient in any group experienced moderate or
  severe nonincisional pain.

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Summary

• For morbidly obese patients successful tracheal
  intubation can be achieved when 1.0 mg/kg SCH is
  administered based on IBW, LBW or TBW
• For complete neuromuscular paralysis and
  predictable laryngoscopy conditions, a larger SCH
  dose (1 mg/kg TBW) is recommended.
• None of these dosing regimens will provide both
  adequate intubating conditions and a safe (short)
  duration of apnea

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Thanks for your attention
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• Excellent laryngoscopy easy with a relaxed jaw
  and no resistance to the laryngoscopy blade,
  vocal cords abducted and do not move, and no
  airway reaction or limb movement during
  endotracheal intubation
• Good jaw not fully relaxed with a slight
  resistance to the laryngoscopy blade, vocal cords
  not fully abducted or are moving, diaphragmatic
  movement (cough, hiccups, or breathing) for less
  than 10 s after intubation, or slight limb
  movement during endotracheal intubation
• Poor poor jaw relaxation or active resistance of
  the patient to laryngoscopy, or vocal cords
  closed, or if diaphragm moves for more than 10 s,
  or if vigorous limb movement during endotracheal
  intubation