The effect of intravenous lidocaine to prevent intracranial pressure increase in endotracheal intubation assessed by optic nerve sheath diameter

Persistent elevated intracranial pressure (ICP > 20 mmHg) is associated with
poor outcome after traumatic brain injury (TBI).[1,4] In the early
posttraumatic period there is a high risk of secondary ischemic damage to the
brain.
It is therefore necessary that further elevations are prevented and
interventions that lower ICP should be initiated as soon as possible to save
brain tissue. To evaluate the effect of these strategies ICP should be
monitored.[5,6]
Ocular ultrasonography has been investigated to assess elevated ICP. The optic
nerve sheath is anatomically continuous with the dura mater, and has a
trabeculated arachnoid space through which cerebrospinal fluid (CSF) slowly
percolates. Therefore, the optic nerve is subjected to the same pressure
changes as the intracranial compartment.[5,7,8] The intra-orbital part of the
subarachnoid space is distensible and can therefore inflate when pressure
increases.[5,9,10] For this reason, the ONSD as measured by ocular
ultrasonography can be considered as a representative for elevated ICP:
Several studies investigated the relationship between ONSD and ICP. [10-20] A
meta-analysis, including 6 studies and 231 patients, showed that
ultrasonography of the ONSD is accurate for detection of an elevated
ICP.[19-20] The analysis revealed a pooled sensitivity of 0.90 (95% confidence
interval 0.80-0.95) and a pooled specificity of 0.85 (95% confidence interval
0.73-0.93).[21] A study investigating the reliability of the sonographic ONSD
measurement in ICU patients, whilst manipulating their endotracheal tube,
concluded that ONSD and ICP correlate well (R2=0.80). A sensitivity of 94% and
specificity of 98% was detected at a cutoff of ONSD >= 5.0 mm, indicating that
measuring ONSD is a reliable tool for monitoring ICP.[22] In this study,
invasive ICP measuring methods were used.

Patients with traumatic brain injury (TBI) present a particular clinical
challenge in prehospital setting, since many airway management techniques
potentially increase ICP. Emergency Medical Service (EMS) services in the
Netherlands are equipped to perform endotracheal intubation (ETI) or inserting
a laryngeal mask airway (LMA) if the airway is not safe. All patients with a
Glascow Coma Score (GCS) less than or equal to 8 need to be intubated. Even
with a minimal GCS (=3) after TBI, intubation without sedatives and relaxants
will trigger laryngeal reflexes that increase ICP.
Coughing and titillation of the laryngeal area causes increased intracranial
pressure [23,24].
Adding Lidocaine 1% IV. is used to prevent postoperative cough and sore throat
[2]. There is some evidence that giving Lidocaine 1,5 mg/kg BW before
intubation might decrease the intracranial response to intubation [3]. Using
lidocaine is common practise in ear nose throat (ENT) surgery to prevent from
coughing due to irritation of the endotracheal tube. Some of our HEMS
physicians use this routinely for anaesthesia induction and intubation of TBI
patients for that reason.
The question arises whether the use of lidocaine iv before intubation should
become a standard therapy in patients with traumatic brain injury.
To evaluate the effects on ICP in patients without TBI we use the non-invasive
ultra-sonographic evaluation of the optical nerve sheath (ONSD). ONSD diameters
correlate with ICP changes. [21]

Primary Objective:
To investigate the effect on the distention of the ONSD while using lidocaine
1,5 mg/kg IV during endotracheal intubation versus placebo.
Secondary Objectives:
The secondary objective of this study is to investigate the effect size of
lidocaine 1,5 mg/kg IV

We will conduct a double blinded single-centre randomized controlled trial.
Patients undergoing general surgery will be asked to give informed consent to
participate. Our study population will be divided in 2 groups. One group of the
patients will get an endotracheal tube, the other group will get an
endotracheal tube after receiving lidocaine 1,5 mg/kg IV. Lidocaine will be
administered 2 minutes before intubation, because than the effect is maximal
[25].
Both groups will get standardized anaesthesia to make sure we have one variable.

For the endotracheal tube only group:
opioid (Fentanyl) -> sedative (Propofol) -> muscle relaxant (Rocuronium)
For the endotracheal tube with lidocaine group:
opioid (Fentanyl) -> lidocaine 1,5 mg/kg iv -> sedative (Propofol) ->
muscle relaxant (Rocuronium)

The dosage of medication is as followed.
- Fentanyl: 4,0 microgram / kilogram
- Propofol: 2,5 milligram / kilogram
- Rocuronium: 0,6 milligram / kilogram
- Lidocaine: 1,5 milligram / kilogram
See appendix for the leaflets.

Obese patients require special dosing regiments [26]. Therefor we calculate the
amount of medication for patients with a BMI greater than or equal to 35 with
lean body weight (LBW) and patients with a BMI less than 35 with total body
weight (TBW).
LBW is calculated with the formula described by Hume [27]
For men: LBW = (0.32810 × W) + (0.33929 × H) * 29.5336
For women: LBW = (0.29569 × W) + (0.41813 × H) * 43.2933
W = body weight in kilograms and H =body height in centimeters

Patients will randomly assigned to one of the 2 groups using a randomisation
list. The ratio will be 1:1. The randomisation list will be made by an
independent person, not involved in this research.

lidocaine 1,5 mg/kg iv or placebo

The technique of OSND-measurement is an accepted technique for an indirect
measurement of the intracranial pressure. To our knowledge there are no adverse
events associated with applying sterile echo gel to the eyelid. There is also
no additional risk regarding the intubation technique because it doesn*t differ
from the normal procedure. The burden for the patient is minimal as each
measurement will take approximately 2 minutes and no other extra interventions
are needed. The subjects do not benefit from the measurement itself. Perhaps in
the near future this non-invasive, in vivo measurement could be used to benefit
patients with elevated intracranial pressure. Our results might be food for
thoughts to change current protocols.
All drugs used are standard drugs for anesthesia induction. The additional use
of lidocaine IV is a commonly used method in daily medical practice. The risk
of adverse events is minimal.