Publication

• Title: Conventional vs Video-Assisted Laryngoscopy for Perioperative Endotracheal Intubations: A Randomized Clinical Trial
• Acronym: COVALENT
• Year: 2026
• Journal published in: JAMA Network Open
• Citation: Schmid B, Grüßer L, Müller L, et al; German Society of Anaesthesiology and Intensive Care (GSAIC) Trials Group. Conventional vs video-assisted laryngoscopy for perioperative endotracheal intubations: a randomized clinical trial. JAMA Netw Open. 2026;9(8):e2625965.

Context & Rationale

• Background

  • Direct laryngoscopy had long been the conventional first-line technique for routine perioperative tracheal intubation, while videolaryngoscopy was increasingly used for predicted or encountered difficulty and, in many centres, for routine intubation.
  • The COVALENT protocol was designed to resolve whether this transition should extend to unselected adult operating-theatre practice and whether blade geometry mattered.¹
  • An updated Cochrane review found that videolaryngoscopes probably reduced failed intubation and increased first-attempt success, but the evidence combined heterogeneous devices, operators, indications and settings.²
  • Recent perioperative trials had favoured Macintosh-style videolaryngoscopy over direct laryngoscopy, including during rapid-sequence induction, and hyperangulated videolaryngoscopy over direct or Macintosh-style approaches; however, most evaluated a single device, a single centre or a selected difficult-airway population.³⁴⁵⁶
• Research Question/Hypothesis

  • Would first-line videolaryngoscopy with either a Macintosh blade or a hyperangulated blade be non-inferior to direct Macintosh laryngoscopy for first-pass tracheal intubation in routine adult perioperative practice?
  • If both video strategies were non-inferior, would either be superior to direct laryngoscopy, and would hyperangulated videolaryngoscopy be superior to Macintosh videolaryngoscopy?
• Why This Matters

  • Tracheal intubation is performed at enormous scale; even a modest absolute increase in first-pass success could prevent many repeat laryngoscopies and rescue manoeuvres.
  • A universal video-first policy has implications for equipment procurement, training, maintenance of direct-laryngoscopy skills, adjunct use and cost.
  • Hyperangulated blades had traditionally been viewed mainly as difficult-airway or rescue devices, so demonstrating benefit as the initial device in an unselected population would materially change practice.

Design & Methods

• Research Question: In adults undergoing perioperative oral tracheal intubation, are Macintosh and hyperangulated videolaryngoscopy each non-inferior to direct Macintosh laryngoscopy within a 5-percentage-point margin, and, if so, are they superior to direct laryngoscopy and is the hyperangulated strategy superior to the Macintosh video strategy?
• Study Type: Investigator-initiated, pragmatic, three-arm, parallel-group, individually randomised, patient-blinded and analyst-blinded multicentre trial conducted at five university hospitals and one intermediate-level hospital in Germany and Austria from 28 March 2022 to 17 February 2025.
• Population:
  • Adults capable of consent who were scheduled for elective surgery under general anaesthesia and required oral tracheal intubation.
  • Exclusions included pregnancy, planned nasal or fibreoptic intubation, and any pre-randomisation clinical concern that made unrestricted assignment to one of the three devices unsafe.
  • Bariatric and cardiac surgery were initially excluded under local rules; these exclusions were removed by protocol amendment on 4 May 2023.
  • Patients were sampled consecutively within the daily capacity of the study-observer team rather than enrolling every eligible case.
  • Operators had performed at least 25 previous videolaryngoscopic intubations; no trial-specific intubation training was provided.
• Intervention:
  • Macintosh videolaryngoscopy: first attempt with a videolaryngoscope using a Macintosh-shaped blade.
  • Hyperangulated videolaryngoscopy: first attempt with a videolaryngoscope using a hyperangulated blade.
  • Device manufacturer and model were determined by local availability; C-MAC, GlideScope, McGrath MAC and HEINE visionPRO devices were used.
  • Stylets, bougies, external laryngeal manipulation and subsequent rescue techniques were permitted at the responsible anaesthetist's discretion and were recorded.
• Comparison:
  • First-attempt direct laryngoscopy with a conventional Macintosh blade.
  • All other induction, positioning, airway adjuncts, rescue procedures and co-interventions followed local practice and clinician judgement.
• Blinding: Patients and data analysts were blinded; the intubating clinicians and real-time study observers could not be blinded. Allocation was revealed non-verbally on a tablet shortly before induction.
• Statistics: The sample-size section targeted 2,532 participants and stated 842 patients per arm to test a 5-percentage-point non-inferiority margin against an assumed 90% direct-laryngoscopy first-pass success rate, with 90% power, one-sided α=0.025 for each video-versus-direct comparison and 10% attrition. A fixed-sequence hierarchy first tested both video arms for non-inferiority, then superiority versus direct laryngoscopy and finally superiority between video strategies. The primary analysis was modified intention-to-treat, including all randomised patients who received any intervention and analysing them by allocation; a per-protocol sensitivity analysis excluded crossovers. Holm correction was applied to secondary outcomes where appropriate.
• Follow-Up Period: From induction through tracheal intubation, with sore throat, hoarseness and cough assessed approximately 2 hours after extubation; there was no longer-term clinical follow-up.

Key Results

This trial was not stopped early. A planned qualitative feasibility assessment after 200 randomised patients did not examine treatment effects, and recruitment continued to the stated target of 2,532 participants; 2,423 (95.7%) were included in the modified intention-to-treat analysis.

• The first-pass success advantage was modest for Macintosh videolaryngoscopy (+4.66 percentage points; published number-needed-to-treat point estimate 21.5) and larger for hyperangulated videolaryngoscopy (+9.34 percentage points; published number-needed-to-treat point estimate 10.7) compared with direct laryngoscopy.
• Videolaryngoscopy reduced repeat-attempt consequences such as intermittent ventilation and clinician change, but did not reduce desaturation, overall time to confirmed intubation or overall mechanical injury.
• Per-protocol and site-adjusted sensitivity analyses supported the direction of the primary result, and the prespecified subgroup plots did not identify a convincing subgroup-specific reversal of effect.

Internal Validity

• Randomisation and Allocation: Web-based permuted-block randomisation was stratified by site and Mallampati class, with allocation concealed until shortly before induction. This provides strong protection against pre-allocation selection bias.
• Post-randomisation Exclusions: Of 2,532 randomised patients, 109 (4.3%) did not receive an intervention and were excluded from the modified intention-to-treat analysis: 49 in DL, 29 in VLM and 31 in VLH. The imbalance was modest but favoured retention in both video groups.
• Performance and Detection Bias: Operators and observers were necessarily unblinded. The primary endpoint was objective, tightly defined and confirmed by capnography, limiting detection bias; operator-rated ease, announced glottic-view timing and discretionary rescue decisions were more vulnerable to expectancy and performance effects.
• Protocol Adherence: The assigned first-device strategy was generally delivered, but management was deliberately pragmatic. No trial-specific training was provided, and positioning, adjunct use, external manipulation and rescue choices were not standardised.
• Baseline Characteristics: Groups were well balanced. Mean age was 59.7 years, mean BMI 27.5 kg/m², 40.4% were ASA III or IV, 18.9% had Mallampati III or IV airways and 11.2% underwent rapid-sequence induction. The low 1.8% overall desaturation rate indicates a comparatively physiologically stable population in whom major harm differences were unlikely to be demonstrated.
• Heterogeneity: Raw first-pass success varied substantially by site—for example, VLM ranged from 71.0% in Salzburg to 96.2% in Leipzig—although a mixed-effects model found little site-level variance and retained treatment effects favouring VLM (OR 1.35; 95% CI 1.05 to 1.73) and VLH (OR 1.97; 95% CI 1.51 to 2.58).
• Timing: The allocated device was used at induction as the first airway strategy, which directly matched the research question. The interval from allocation to first laryngoscopy was not reported.
• Dose: Not applicable in the pharmacological sense. The relevant exposure was first-device assignment; operator eligibility required at least 25 previous videolaryngoscopic intubations.
• Key Delivery Aspects: Sufficient preoxygenation was documented in 2,192/2,306 patients (95.1%). A train-of-four count of zero was documented in only 637/1,088 measured patients (58.5%), but these measures were balanced across groups. Device choice within each blade category and all rescue sequencing remained locally determined.
• Separation of the Variable of Interest: The intervention contrast was not limited to blade geometry. Stylet use was 34.9% with DL, 72.5% with VLM and 95.7% with VLH; backward-upward-rightward pressure was used in 40.7%, 24.0% and 13.4%, respectively. The causal contrast is therefore best understood as three pragmatic intubation strategies rather than three isolated laryngoscope blades.
• Crossover: Before the first attempt, 41 DL patients changed device (32 to VLM and 9 to VLH), compared with 13 VLM patients and 8 VLH patients. This asymmetric crossover could dilute the modified intention-to-treat effect of video, but the per-protocol results were nearly identical.
• Adjunctive Therapy Use: The major imbalance in stylet use is clinically intrinsic to many hyperangulated techniques but prevents attribution of the observed advantage solely to camera view or blade shape. Bougie use was negligible at 0.1% overall.
• Outcome Assessment: First-pass success was clearly defined: withdrawal of either the laryngoscope or tracheal tube from the mouth constituted failure, and success required positive capnography. Trained independent observers recorded procedures in real time.
• Statistical Rigour: The primary hierarchy, non-inferiority margin, modified intention-to-treat analysis, per-protocol sensitivity analysis and multiplicity correction were prespecified. Nevertheless, several internal numerical inconsistencies and implausibly narrow published confidence intervals weaken confidence in the exact precision of the estimates.

Conclusion on Internal Validity: Internal validity is moderate for the direction and magnitude of the primary strategy-level effect: randomisation, allocation concealment, an objective endpoint and concordant sensitivity analyses all favour a genuine first-pass benefit. Confidence is lower in the exact effect precision and in attributing benefit specifically to videolaryngoscope blade geometry rather than the complete device–adjunct strategy.

External Validity

• Population Representativeness: The broad adult surgical cohort, inclusion of multiple specialties, 18.9% Mallampati III/IV airways and 11.2% rapid-sequence inductions support applicability to routine operating-theatre work. However, only 2,532 of 29,357 screened patients were randomised; 8,518 were missed because study personnel were unavailable, and clinicians could exclude cases in which random device assignment raised safety concerns.
• Clinical Setting: Five of six centres were university hospitals in Germany or Austria, and all operators had prior videolaryngoscopy experience. Results are most directly applicable to well-resourced European operating theatres with trained anaesthesia staff.
• Excluded Populations: The trial does not directly inform paediatric, obstetric, awake, planned fibreoptic, nasal, prehospital, emergency-department or ICU intubation, nor patients in whom one device was already judged clinically necessary.
• Device Generalisability: Four manufacturers were represented, improving breadth beyond single-device trials, but Storz C-MAC devices accounted for 62.2% of video use. Channelled videolaryngoscopes were not evaluated, and manufacturer effects were not randomised or adequately powered.
• Resource Implications: Universal videolaryngoscopy requires acquisition, maintenance, cleaning or disposable-blade supply, compatible stylets and training. Translation to resource-limited systems therefore depends on affordability and device availability.

Conclusion on External Validity: External validity is good for adult routine perioperative intubation in well-resourced settings with clinicians already competent in videolaryngoscopy. Extrapolation to emergency and critical-care intubation, unfamiliar operators, channelled devices or resource-constrained environments should be cautious.

Strengths & Limitations

• Strengths:
  • Large, individually randomised, three-arm comparison of direct, Macintosh video and hyperangulated video strategies.
  • Six-centre, two-country pragmatic design using several commercially available devices.
  • Concealed allocation, stratification by site and Mallampati class, and a prespecified hierarchical testing strategy.
  • Objective, clinically intuitive primary outcome observed in real time and confirmed by capnography.
  • Modified intention-to-treat, per-protocol and site-adjusted analyses produced concordant findings.
  • Investigator-initiated, professional-society-funded trial without manufacturer involvement.
• Limitations:
  • First-pass success is a procedural surrogate; the trial did not demonstrate less desaturation, shorter overall intubation time or fewer overall airway injuries.
  • Operators and observers were unblinded, and several secondary endpoints depended on clinician judgement.
  • Large and clinically important imbalances in stylet use and external laryngeal manipulation confounded device-specific interpretation.
  • More crossover occurred from DL to video than in the opposite direction.
  • Daily staff-capacity sampling and clinician safety exclusions may have selected a manageable subset of cases.
  • Postoperative symptoms were collected at only two centres and in 56.9% of randomised participants.
  • The study was underpowered for rare catastrophic airway events, individual manufacturers and treatment-effect heterogeneity.
  • Important inconsistencies in participant counts, sample-size arithmetic, effect labelling and confidence intervals reduce reporting reliability.

Interpretation & Why It Matters

• Video-first practice

  COVALENT provides direct randomised evidence that both Macintosh and hyperangulated videolaryngoscopy improve first-pass success over direct laryngoscopy in routine adult operating-theatre intubation.
• Magnitude of benefit

  The absolute gain was approximately 5 percentage points with Macintosh videolaryngoscopy and 9 percentage points with hyperangulated videolaryngoscopy. These are clinically meaningful at scale, although most patients in every group were intubated on the first attempt.
• Hyperangulated blades

  The VLH arm achieved the highest first-pass success and better performance after failed attempts, supporting a role beyond anticipated difficult airways. The result applies to a hyperangulated strategy that almost always incorporated a stylet, not to blade curvature in isolation.
• Patient-centred outcomes

  The trial does not establish that routine videolaryngoscopy reduces hypoxaemia, airway trauma, postoperative symptoms, rare catastrophic events or longer-term morbidity. First-pass success should therefore be interpreted as an important process outcome rather than definitive proof of improved patient safety.
• Clinical implementation

  Where suitable equipment, adjuncts and training already exist, COVALENT strengthens the case for videolaryngoscopy as the default first device. Implementation should include device-specific training, stylet technique, rescue planning, cost evaluation and continued competence with alternative airway approaches.

Controversies & Other Evidence

• Procedural surrogate versus patient benefit: The accompanying editorial emphasised that first-pass success is clinically intuitive but remains a procedural outcome. COVALENT did not show a clear reduction in desaturation or overall dental, lip or mucosal injury, and the contemporary airway core outcome set reinforces the need to distinguish technical success from patient-centred benefit.⁷⁸
• Device effect or strategy effect: Stylet use differed profoundly—34.9% with DL, 72.5% with VLM and 95.7% with VLH. A stylet can itself increase first-attempt success, and a hyperangulated blade generally requires one; COVALENT therefore compares practical device–adjunct packages rather than isolating the effect of video imaging or blade geometry.⁷⁹
• Selection before randomisation: Of 29,357 patients assessed, 26,825 were not randomised, including 8,518 because no trial personnel were available. Clinician concerns could also prevent randomisation. Conversely, 18.9% of enrolled patients had Mallampati III or IV airways, a group in whom clinicians may already preferentially use video. The direction and size of any resulting selection effect are uncertain.⁷
• Manufacturer and device mix: The device-agnostic design increased pragmatism, but C-MAC represented 62.2% of video use and manufacturer was not randomised. The findings cannot be assumed to apply equally to every videolaryngoscope, especially channelled devices.⁷
• Post-failure analyses: Comparisons among the 414 patients whose initial attempt failed were conditioned on a post-randomisation event whose frequency differed by treatment. Randomisation no longer guarantees comparable groups within this subset, so the shorter times and lower injury composite with VLH are exploratory and cannot securely support a causal claim that VLH reduced complications.
• Protocol evolution: The original protocol included Mayo teamwork and NASA task-load outcomes. After the first 200 participants, these human-factors measures were curtailed to optional centre-specific substudies because further collection was not expected to add insight; they were not reported in the main trial. This did not alter the primary endpoint, but one element of the original rationale therefore remains unanswered.¹
• Non-inferiority framework and control performance: A 5-percentage-point margin would have allowed a video strategy to cause one additional first-pass failure per 20 patients and still be declared non-inferior. Both video arms subsequently met superiority criteria, so the principal interpretation does not depend on accepting that margin. However, observed DL first-pass success was 78.2%, far below the assumed 90%; absolute benefit will be context-dependent and may be smaller where direct-laryngoscopy performance is higher.
• Reporting inconsistencies: The text and tables state that 2,532 patients were randomised to 848 DL, 841 VLM and 843 VLH, whereas the CONSORT figure states 2,535 randomised and displays 848, 848 and 841, which sum to 2,537. The figure lists 758 VLH patients in the per-protocol analysis, while the supplement reports 804. The sample-size section states 842 patients per arm and 2,532 overall, while the protocol states 824 per arm and 2,526 overall; both descriptions are arithmetically inconsistent.
• Effect-estimate precision: The published absolute-difference intervals—for example, a 4.66-percentage-point difference with a 95% CI of 4.45 to 4.78—appear implausibly narrow for groups of approximately 800 patients. The reported NNT intervals are similarly narrow. The abstract also states that all primary comparisons had P<0.001, although VLM versus DL superiority was P=0.02, and the main text reverses the label for the VLH-versus-VLM relative risk. The raw event rates and broad direction are coherent, but the exact absolute-effect confidence intervals require correction or clarification.
• Consistency with perioperative evidence: COVALENT aligns with the EMMA trial, in which first-pass success was 93.7% with McGrath Macintosh videolaryngoscopy versus 81.6% with direct laryngoscopy; the rapid-sequence trial by Kriege and colleagues, 94.0% versus 71.6%; the Ruetzler cluster trial of hyperangulated video, 98.3% versus 92.4%; and the difficult-airway trial by Köhl and colleagues, 97% with hyperangulated versus 67% with Macintosh videolaryngoscopy.³⁴⁵⁶
• Evidence outside the operating theatre: In critically ill adults, DEVICE increased first-attempt success from 70.8% with direct laryngoscopy to 85.1% with video, but severe intubation complications were similar. This parallel supports a robust technical effect while again showing that improved first-pass success does not automatically translate into measurable patient-centred benefit.¹⁰
• Guidelines and implementation: International recommendations advocating universal videolaryngoscopy and the Difficult Airway Society guidance already favoured video-first strategies, but both predated publication of COVALENT. The trial strengthens their evidential foundation; no post-COVALENT guideline or confirmatory trial had yet incorporated these findings at the time of this summary.¹¹¹²
• Economic uncertainty: Universal deployment may be justified by fewer repeat attempts and rescue manoeuvres, but COVALENT did not evaluate cost-effectiveness. Device purchase, maintenance, reusable versus disposable blades, stylets, training, operating-theatre volume and the uncertain effect on rare complications all matter.⁷

Summary

• COVALENT randomised 2,532 adults undergoing routine perioperative intubation to direct Macintosh laryngoscopy, Macintosh videolaryngoscopy or hyperangulated videolaryngoscopy.
• First-pass success was 78.2%, 82.9% and 87.6%, respectively; both video strategies were superior to direct laryngoscopy, and hyperangulated video was superior to Macintosh video.
• Videolaryngoscopy reduced intermittent ventilation and the need to change anaesthesia clinician, but did not improve overall time to capnographic confirmation, desaturation or overall mechanical injury.
• The pragmatic strategy-level result is strengthened by concealed randomisation and concordant sensitivity analyses, but attribution to blade geometry is limited by markedly unequal stylet use.
• The trial supports video-first routine operating-theatre practice, particularly a hyperangulated strategy in experienced hands, while leaving patient-centred safety, cost-effectiveness and applicability beyond the operating theatre unresolved.

Overall Takeaway

COVALENT is a large, practice-shaping perioperative airway trial showing that first-line videolaryngoscopy—especially a hyperangulated device–stylet strategy—improves first-pass intubation success over direct laryngoscopy. It supports videolaryngoscopy as the default device in appropriately equipped and trained operating theatres, but it does not prove fewer patient-centred complications, and the publication's numerical inconsistencies require formal clarification.

Bibliography

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