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Tracheal intubation with a flexible intubation scope versus other intubation techniques for obese patients requiring general anaesthesia

  1. Amanda Nicholson1,
  2. Andrew F Smith2,
  3. Sharon R Lewis3,*,
  4. Tim M Cook4

Editorial Group: Cochrane Anaesthesia, Critical and Emergency Care Group

Published Online: 17 JAN 2014

Assessed as up-to-date: 18 JAN 2013

DOI: 10.1002/14651858.CD010320.pub2


How to Cite

Nicholson A, Smith AF, Lewis SR, Cook TM. Tracheal intubation with a flexible intubation scope versus other intubation techniques for obese patients requiring general anaesthesia. Cochrane Database of Systematic Reviews 2014, Issue 1. Art. No.: CD010320. DOI: 10.1002/14651858.CD010320.pub2.

Author Information

  1. 1

    University of Liverpool, Liverpool Reviews and Implementation Group, Liverpool, UK

  2. 2

    Royal Lancaster Infirmary, Department of Anaesthetics, Lancaster, Lancashire, UK

  3. 3

    Royal Lancaster Infirmary, Patient Safety Research, Lancaster, UK

  4. 4

    Royal United Hospital, Department of Anaesthesia, Bath, UK

*Sharon R Lewis, Patient Safety Research, Royal Lancaster Infirmary, Pointer Court 1, Ashton Road, Lancaster, LA1 1RP, UK. Sharon.Lewis@mbht.nhs.uk. sharonrlewis@googlemail.com.

Publication History

  1. Publication Status: New
  2. Published Online: 17 JAN 2014

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Characteristics of included studies [ordered by study ID]
Abdelmalak 2011

MethodsSingle-centre RCT, University hospital, Cleveland, Ohio, USA


Participants75 participants > 18 years requiring orotracheal intubation for elective surgery. No details given of type of surgical procedure. BMI > 30 kg /m2

Exclusions: known difficult airway needing awake intubation; loose teeth; pregnant; patient required rapid sequence induction; attending anaesthesiologist required non-standard TT

Median BMI (IQR):  FIS 37 (33 to 49); Glidescope 36 (34 to 44)

Mean age (SD): FIS 54 years (11); Glidescope 52 years (16)

% female: FIS 49%; Glidescope 68%

% Caucasian: FIS 97%; Glidescope 87%

   


Interventions37 participants randomly assigned to fibreoptic intubation (FIS). Model of FIS not given. Sniffing position used, with ramp positioned under shoulders. Permitted to use external laryngeal manipulation or to change the position of the participant's head to improve the glottis view or to facilitate intubation

38 participants randomly assigned to videolaryngoscope (VLS). Glidescope: Verathon Medical. Sniffing position used, with ramp positioned under shoulders. Used with Mallinckrodt Satin-Slip intubating stylet. Permitted to use external laryngeal manipulation or to change the position of the participant's head to improve the glottis view or to facilitate intubation

Both groups used Flex-Tip TT (Parker), size 7.5 for men and 7.0 for women


OutcomesFailed intubation or change of airway device required. Failed intubation considered as > than three minutes taken or > four attempts

Hypoxia < 90% at any time 1 minute before intubation to 10 minutes after

Participant-reported sore throat or hoarseness: rated as mild/ moderate or severe on POD1

Number of attempts for intubation

Bleeding on intubation

Placement: total time for securing airway device from insertion of Glidescope or for FIS insertion of Williams airway to when end-tidal PCO2 > 2.7 kPa (given as medians)

Difficulty of tracheal intubation, as assessed by intubator on VAS 0 to 100 (given as medians)


Details of anaesthetic induction and intubationPreoxygenated to end-tidal O2 conc 80%

Standard IV induction. Induction and maintenance of anaesthesia overseen by anaesthesiologist who chose NMBA  agent. When paralysed, randomization revealed 

Used Flex-Tip TT (Parker), size 7.0 for men and 7.5 for women

After induction, ventilated with 100% oxygen until confirmed NMB

Mask ventilation permitted between intubation attempts


Training and seniority of intubatorTwo “experienced” intubators


NotesStudy supported through internal funding from Cleveland Clinic. Statement indicating no conflicts of interest


Risk of bias

BiasAuthors' judgementSupport for judgement

Random sequence generation (selection bias)Low riskComputer-generated codes

Allocation concealment (selection bias)Low risk"Maintained in sequentially numbered opaque envelopes"

Blinding of participants and personnel (performance bias)
Failed intubation, first success, ease of intubation and time for intubation
High riskIntubators not blinded

Blinding of participants and personnel (performance bias)
Hypoxia
Low riskStandardized preoxygenation protocol. Randomization not revealed until participant paralysed

Blinding of participants and personnel (performance bias)
Patient-reported outcomes
Unclear riskParticipants were blinded to allocation. No details of how participants were treated after surgery and pain relief, etc, given. Unclear whether recovery staff were blinded

Blinding of outcome assessment (detection bias)
Failed intubation, first success, ease of intubation and time for intubation.
High riskIntubators not blinded

Blinding of outcome assessment (detection bias)
Hypoxia
Low riskObserver collecting postintubation records was blinded

Blinding of outcome assessment (detection bias)
Patient-reported outcomes
Low riskParticipants were blinded to allocation

Incomplete outcome data (attrition bias)
All outcomes
Low riskNo apparent losses to follow-up

Selective reporting (reporting bias)Low riskAll outcomes prespecified in Methods section and on trial register. No outcomes not reported

Other biasLow riskMore men in FIS group. Article gives effect estimates adjusted for age

Aikins 2010

MethodsSingle-centre RCT. University Hospital, Texas, USA


Participants20 obese patients BMI > 27.5 kg/m2. Unclear whether patients undergoing surgery. Inclusion criteria: ASA II to III. Exclusion criteria: ASA IV to V

Mean BMI (SD): FIS 32 (2.5); intubating SAD 34 (7); VLS 35 (4.5); stylet 34 (7)

Mean age (SD): FIS 48.4 (16); intubating SAD 46.8 (9); VLS 40 (17); stylet 43 (14)


InterventionsFour intervention groups. Five participants randomly assigned to each of the following.

  • FIS fibreoptic bronchoscope. 30 cc oral Bicitra (0.2 mg glycopyrrolate intravenously).


  • Intubating SAD (Fastrach size 4 or 5)


“Following insertion the cuff was inflated with 25-40 ml of air and manual ventilation attempted. Tidal volumes >10 ml/kg, adequate movement of the chest wall and over 15 cm H2O airway pressure were judged acceptable ventilation. Only one attempt at blind intubation through the Fastrach™ with the silicone ett was undertaken. If unsuccessful, one attempt at fibreoptic
bronchoscope guided tracheal intubation through the Fastrach™ was allowed”

  • VLS (Bullard)
  • Stylet (Trachlight)


OutcomesFailed intubation.

  • VLS, stylet and FIS: two attempts allowed with max time of 120 s


  • Intubating SAD: one blind attempt, then one with FIS with max time 120 s


Complications such as mucosal bleeding injury, hoarseness, dental injury, sore throat, difficult or painful swallowing assessed by participant review on POD0 and POD1

Time of insertion of test device into oropharynx to manual ventilation through TT


Details of anaesthetic induction and intubationRapid sequence induction

Preoxygenation for three to five minutes; general anaesthesia was induced intravenously with 1 to 2 mg/kg propofol, 1 to 3 mcg/kg fentanyl and 1 mg/kg succinylcholine IV. After induction, cricoid pressure was maintained and mask ventilation verified. In all groups, an appropriately sized tracheal tube (TT) for oral intubation was chosen (inner diameter 7.5 to 8.0 mm in males and 7.0 to 7.5 mm in females)

NBMA: 1 mg/kg succinylcholine


Training and seniority of intubatorNovice intubator (physician anaesthetist). Ten months' experience with direct laryngoscopy

Viewed instructional videos and received didactic instruction on four devices. No more than five practical experience with devices


NotesStatement indicating no sources of support and no conflicts of interest


Risk of bias

BiasAuthors' judgementSupport for judgement

Random sequence generation (selection bias)Unclear riskParticipants randomly assigned—no further details

Allocation concealment (selection bias)Unclear riskNo details

Blinding of participants and personnel (performance bias)
Failed intubation, first success, ease of intubation and time for intubation
High riskNo mention of blinding

Blinding of participants and personnel (performance bias)
Patient-reported outcomes
Unclear riskNo details of how participants were treated after surgery and of pain relief, etc, given. Unclear whether recovery staff were blinded

Blinding of outcome assessment (detection bias)
Failed intubation, first success, ease of intubation and time for intubation.
High riskNo mention of blinding

Blinding of outcome assessment (detection bias)
Patient-reported outcomes
Unclear riskNot clear whether participant blinded. No standardized instruments described

Incomplete outcome data (attrition bias)
All outcomes
Low riskNo apparent loss to follow-up

Selective reporting (reporting bias)Low riskAll outcomes prespecified in Methods

Other biasLow risk

Rosenstock 2012

MethodsMulti-centre RCT. Three university hospitals, Copenhagen, Denmark


Participants93 adult elective participants with anticipated difficult laryngoscopy requiring GA and awake oral intubation. Scheduled for gynaecological, abdominal, urological and ENT procedures

No obesity inclusion, but 46 participants with BMI > 30 kg/m2 presented as subgroup. Outcome data (ITT analysis) obtained in personal communication with study authors

Inclusion criteria: age > 18 years; ASA I to III; simplified airway risk index (SARI) > =4.

Exclusion criteria: mouth opening < 15 mm; poor dental status; surgeon request of nasal intubation; contraindication to transtracheal injection

9 of total 93 participants did not complete protocol; 7 transtracheal injection impossible & 2 lack of co-operation. Unclear how many of these were obese

Mean BMI (SD): FIS 36.7 (6.1); VLS 38.2 (5.3)

Mean age (SD): FIS 59.5 years (8.9); VLS 65.0 years (11.2)


Interventions26 obese participants randomly assigned to FIS. Scope make not given. Berman II intubation airway size 8 or 9 for women  size 9 or 10 for men Assistant performed jaw thrust to expand oropharyngeal space. TT model not given. Participant position left to discretion of intubator

20 obese participants randomly assigned to VLS (McGrath series 5). Sniffing position used. A stylet was used to bend the tip of the tube 80 to 100 degrees


OutcomesFailed intubation: "in the case the first technique failed after three attempts, then optimal patient positioning was secured before an attempt at tracheal intubation with the alternative device"

Hypoxia of < 90% oxygen saturation during intubation attempt

Participant report of discomfort during awake intubation measured on VAS score 0 (none) to 10 (worst possible) on discharge from recovery

Tooth damage and signs of soft tissue damage. Bleeding reported

Number of attempts at intubation

Total time for intubation (from advancement of FIS or VLS behind teeth until appearance of a capnography curve)

Intubator's evaluation of ease of technique VAS 0 to 10 (presented as medians)


Details of anaesthetic induction and intubationAwake intubation

Participants given glycopyrrolate 4 to 5 mcg/kg after IV cannula placed

Nasal catheter giving 2 to 4 litres O2

Continuous remifentanil infusion 0.1 to 0.15 mcg/kg/min with bolus dose of 0.75 mcg/kg as needed to keep participant sedation to Ramsay score of 2 to 4.

Topical analgesia: lidocaine 10% to oropharynx

50 to 100 mg lidocaine given by transtracheal injection

Sufficient analgesia given to avoid coughing and achieve acceptance of TT

Make of TT used not standardized—size and make chosen before randomization


Training and seniority of intubatorSix investigators all “thoroughly trained in difficult airway management and also specifically experienced in using [both devices]"


NotesTwo McGrath VLSs were provided by SECMA (Skaevinge, Denmark) to two hospitals for the duration of the trial. Statement that authors had no conflicts of interest and were not provided with any funding from the manufacturers


Risk of bias

BiasAuthors' judgementSupport for judgement

Random sequence generation (selection bias)Low risk"Variable block-size randomization, computer-generated random numbers. First block included 20 patients and second block 15 patients"

Allocation concealment (selection bias)Low risk"Number assignment kept in sealed envelopes" Personal communication from authors—also numbered and opaque

Blinding of participants and personnel (performance bias)
Failed intubation, first success, ease of intubation and time for intubation
High riskParticipants, investigators and care providers knew allocation

Blinding of participants and personnel (performance bias)
Hypoxia
Low riskAll participants given 2to 4 litres of oxygen

Blinding of participants and personnel (performance bias)
Patient-reported outcomes
High riskParticipants, investigators and care providers knew allocation

Blinding of outcome assessment (detection bias)
Failed intubation, first success, ease of intubation and time for intubation.
High riskParticipants, investigators and care providers knew allocation

Blinding of outcome assessment (detection bias)
Hypoxia
High riskParticipants, investigators and care providers knew allocation

Blinding of outcome assessment (detection bias)
Patient-reported outcomes
High riskParticipants, investigators and care providers knew allocation

Incomplete outcome data (attrition bias)
All outcomes
Low riskNo apparent losses to follow-up in obese participants. ITT analyses in personal correspondence from study author

Selective reporting (reporting bias)Low riskAll outcomes prespecified in Methods are reported

Other biasLow risk

 
Characteristics of excluded studies [ordered by study ID]

StudyReason for exclusion

Ezri 2004Observational study of methods of intubation in obese participants undergoing bariatric surgery

Gercek 2008RCT of different methods of intubation in non-obese participants to assess cervical spine motion

ISRCTN71888001RCT of nasotracheal intubation using FIS or Macintosh laryngoscope in maxillofacial surgery participants. BMI > 35 kg/m2 excluded

Liang 2010Letter with no data presented

NCT01656967RCT of use of AMBU AScope2 Fiberoptic Intubation versus Fastrach Intubating LMA. BMI > 35 kg/m2 excluded. Personal communication from study authors—only five participants with BMI > 30 kg/m2

 
Comparison 1. Intubation with FIS versus videolaryngoscope

Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size

 1 Change of intubation method3Risk Ratio (M-H, Fixed, 95% CI)Totals not selected

 2 Participants with episodes of desaturation2Risk Ratio (M-H, Random, 95% CI)Totals not selected

 3 Bleeding during/after intubation3Risk Ratio (M-H, Fixed, 95% CI)Totals not selected

 4 Sore throat2Risk Ratio (M-H, Fixed, 95% CI)Totals not selected

 5 Successful first intubation3Risk Ratio (M-H, Fixed, 95% CI)Totals not selected

 6 Intubator's assessment of difficulty of intubationOther dataNo numeric data

 
Analysis 1.6 Comparison 1 Intubation with FIS versus videolaryngoscope, Outcome 6 Intubator's assessment of difficulty of intubation.
Intubator's assessment of difficulty of intubation

StudyGroup (N)MedianIQRSignificance test

Abdelmalak 2011FIS (37)2011-40

Abdelmalak 2011VLS (38)1510-21P=0.19 (Cox regression)

Abdelmalak 2011Measure : VAS 0-100 (extremely difficult)

Rosenstock 2012FIS (26)21-3

Rosenstock 2012VLS (20)11-6.5

Rosenstock 2012Measure: VAS -10 (most difficult)N/A

 
Summary of findings for the main comparison. Intubation with FIS versus videolaryngoscope for obese patients requiring general anaesthesia

Intubation with FIS versus videolaryngoscope for obese patients requiring general anaesthesia

Patient or population: obese patients requiring general anaesthesia
Settings:
Intervention: intubation with FIS versus videolaryngoscope

OutcomesIllustrative comparative risks* (95% CI)Relative effect
(95% CI)
No of participants
(studies)
Quality of the evidence
(GRADE)
Comments

Assumed riskCorresponding risk

ControlIntubation with FIS versus videolaryngoscope

Change of intubation methodSee commentSee commentNot estimable131
(3)
See commentResults from all studies were inconclusive and consistent with an increased or decreased risk of change of device in the FIS group1

Patients with episodes of desaturationSee commentSee commentNot estimable121
(2)
See commentResults from all studies were inconclusive and consistent with an increased or decreased risk of hypoxia in the FIS group1

Bleeding during/after intubationSee commentSee commentNot estimable131
(3)
See commentResults from all studies were inconclusive and consistent with an increased or decreased risk of bleeding in the FIS group1

Sore throatSee commentSee commentNot estimable85
(2)
See commentResults from all studies were inconclusive and consistent with an increased or decreased risk of sore throat in the FIS group

Successful first intubationSee commentSee commentNot estimable131
(3)
See commentResults from all studies were inconclusive and consistent with an increased or decreased risk of successful first attempt in the FIS group

*The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).
CI: Confidence interval.

GRADE Working Group grades of evidence.
High quality: Further research is very unlikely to change our confidence in the estimate of effect.
Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.
Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.
Very low quality: We are very uncertain about the estimate.

 1Because of substantial differences in study design, these studies were not suitable for data synthesis.