Best Evidence Topics

Cohort

Hamill JF, Bedford RF, Weaver DC, Colohan AR
Lidocaine Before Endotracheal Intubation: IV or Laryngotracheal?
Anesthesiology
1981; 55:578-581
  • Submitted by:Dale Ray - Emergency Medicine Faculty
  • Institution:Grand Rapids MERC/ Michigan State University, Grand Rapids, MI
  • Date submitted:14th July 2006
Before CA, i rated this paper: 3/10
1 Objectives and hypotheses
1.1 Are the objectives of the study clearly stated?
  Yes, the purposes of this study were two-fold: 1) to describe the effects of laryngotracheal lidocaine administration in intracranial pressure, and 2) to determine whether there is a preferred route for administration of lidocaine before endotracheal intubation.
2 Design
2.1 Is the study design suitable for the objectives?
  Yes, prospective cohort study designed to answer the study question. However, a control group would have answered the question: is pretreatment with lidocaine even necessary in patients undergoing rapid sequence intubation?
2.2 Who / what was studied?
  Twenty-two patients with brain tumors greater than 3 cm diameter by CT (all on steroids and scheduled for craniotomy) from the University of Virginia were randomized to IV or laryngotracheal lidocaine pre-intubation. In the OR, arterial and central lines were placed along with a subarachnoid pressure screw. After assessment of baseline ICP, blood pressure, and heart rate, patients received thiopental (3 mg/kg), succinylcholine (1.5 mg/kg), and 50% nitrous oxide.
2.3 Was a control group used if appropriate?
  No, patients received either laryngotracheal lidocaine through direct visualization with a standard laryngotracheal anesthesia set, or 1.5 mg/kg IV lidocaine. The method of randomization not discussed.
2.4 Were outcomes defined at the start of the study?
  The resulting chnages in heart rate, ICP, and mean arterial pressure were measured prior to and following laryngoscopy.
2.5 Was this the right sample to answer the objectives?
  No—all were brain tumor patients. Although not an entirely unreasonable model for normotensive head injury patients, most multi-trauma patients are neither normotensive nor prepped for surgery.
2.6 Is the study large enough to achieve its objectives? Have sample size estimates been performed?
  No sample size estimates were described.
2.7 Were all subjects accounted for?
  Yes
2.8 Were all appropriate outcomes considered?
  No, the most important outcome is neurological recovery and mortality, of which ICP is only a surrogate marker.
2.9 Has ethical approval been obtained if appropriate?
  Yes
3 Measurement and observation
3.1 Is it clear what was measured, how it was measured and what the outcomes were?
  Yes
3.2 Was the assessment of outcomes blinded?
  Presumably single-blinded since the patients were under anesthesia and the families were not in the OR, although the authors do not discuss blinding. Clinicians and outcome assessors were likely aware of group allocation.
3.3 Was follow up sufficiently long and complete?
  Subjects were only followed while in the OR, so no loss to follow-up.
3.4 Are the measurements valid?
  Yes, although potential bias if physicians and/or outcome assessors were not blinded to the intervention arm.
3.5 Are the measurements reliable?
  Yes, wider confidence intervals for laryngotracheal than for IV lidocaine group, but both groups reasonably narrow and they do not cross.
3.6 Are the measurements reproducible?
  Yes
4 Presentation of results
4.1 Are the basic data adequately described?
  Yes (Figures 1-3)
4.2 Are the results presented clearly, objectively and in sufficient detail to enable readers to make their own judgement?
  Yes
4.3 How large are the effects within a specified time?
  IV appears to effectively accentuate the elevation in ICP (ÄICP at time of intubation 3 mm Hg versus 14 mm Hg), MAP (24% versus 45%), and HR (ÄHR 15 versus 30) compared with LT. LT lidocaine administration appears to independently elevate ICP even before intubation, an effect which is sustained up to two minutes post-intubation.
4.4 Are the results internally consistent, i.e. do the numbers add up properly?
  Yes
5 Analysis
5.1 Are the data suitable for analysis?
  Yes
5.2 Are the methods appropriate to the data?
  Yes
5.3 Are any statistics correctly performed and interpreted?
  Yes, statistical comparisons were performed using analysis of variance and critical difference testing.
6 Discussion
6.1 Are the results discussed in relation to existing knowledge on the subject and study objectives?
  Yes, results indicate that intravenous route is the preferred technique for administering lidocaine prior to endotracheal intubation.
6.2 Is the discussion biased?
  No
7 Interpretation
7.1 Are the author's conclusions justified by the data?
  Yes, although IV lidocaine did not entirely prevent cardiovascular stimulation in response to endotracheal intubation, significant increases in heart rate and mean arterial pressure occurred only within the first minute after intubation. In contrast, the group which received laryngotracheal lidocaine sustained significant increases in cardiovascular variables which persisted for at least two minutes (Figures 2 and 3)
7.2 What level of evidence has this paper presented? (using CEBM levels)
  2b
7.3 Does this paper help me to answer my problem?
  Yes
After CA, i rated this paper: 5/10
8 Implementation
8.1 Can any necessary change be implemented in practice?
  The use of intravenous lidocaine (1.5 mg/kg) given one minute prior to intubation may prevent intracranial hypertension as well as limit the intensity and duration of cardiovascular stimulation.
Topical laryngotracheal administration of lidocaine increases ICP, HR, and MAP and does not protect against potentially harmful cardiovascular and intracranial pressure changes induced by intubation.
8.2 What aids to implementation exist?
  IV lidocaine is inexpensive, relatively safe and easy to administer during RSI
8.3 What barriers to implementation exist?
  The pre-intubation medication regimen utilized by this study protocol is rarely, if ever, used in EM currently. The results might differ with current RSI regimens.
8.4 Are the study patients similar to your own?
  No, this is a small study of a select population in a well controlled environment. The results cannot be extrapolated to the ED where we are generally concerned about elevated intracranial pressure in traumatic brain injury with intubating physicians of various skill-level, intubations performed for a variety of indications under often suboptimal conditions, with often tenuous hemodynamic stability.
8.5 Does the paper give any conclusions that will affect what you will offer or tell your patient?
  This is the only prospective study in the english literature that evaluates intravenous lidocaine to prevent intracranial hypertension as well as limit the intensity and duration of cardiovascular stimulation.