Module 3
Complications of Managing the Airway
Responses to Intubation
The larynx has the greatest afferent nerve
supply of the airway. Airway reflexes require suppression for
stress-free airway management, especially for endotracheal
intubation. Intensive autonomic responses may occur during
placement, maintenance and removal of all airway devices.
HEMODYNAMIC CHANGES
Direct laryngoscopy and endotracheal
intubation are both stimulating procedures that may cause
intense autonomic responses.33
Tachycardia, hypertension, dysrhythmias, bronchospasm, and
bronchorrhea are common; hypotension and bradycardia occur less
often. Patients with pre-existing hypertension are at
higher risk.
The sympathetically mediated responses to
mechanical stimulation of larynx, trachea-carina and bronchi may
be blocked by topical or intravenous lidocaine, by giving
opioids or short-acting selective α1-blockers
before laryngoscopy and intubation. Large hemodynamic
responses have to be prevented in patients with coexisting
cardiovascular disease. More than 11% of patients with
myocardial disease develop some degree of myocardial ischemia
during intubation.34
The key element is to provide an adequate depth of anesthesia
with either intravenous or inhalation agents before
instrumentation of the airway.
Fiberoptic intubation performed under
adequate local anesthesia and conscious sedation is an
appropriate technique to prevent major hemodynamic changes
during intubation. The lowest cardiovascular responses were
registered in patients after insertion of a LMA.
LARYNGOSPASM AND BRONCHOSPASM
Due to reflex responses to stage II of
anesthesia, laryngospasm can occur during intubation.
Laryngospasm involves more than spastic closure of the vocal
cords. An infolding of the arytenoids and the
aryepiglottic folds occurs; these structures are subsequently
covered by the epiglottis. This explains why a firm jaw
thrust can sometimes break the spasm: the hyoid is elevated,
thereby stretching the epiglottis and aryepiglottic folds to
open the forced closure. Malpositioning due to incorrect
insertion techniques, as well as inadequate depth of anesthesia
during LMA insertion, may induce laryngospasm. It may also
occur during fiberoptic intubation performed in non- or
subanesthetized laryngeal structures. Positive mask
pressure may help; treatment with a short-acting muscle relaxant
may be necessary to break the spasm.
Tracheal irritation from the endotracheal
tube can cause bronchospasm that is sufficiently severe
to prevent air movement throughout the lungs. The
incidence of intraoperative bronchospasm is almost 9% with
endotracheal intubation, 0.13% with an LMA, but close to 0% with
mask ventilation.35
Poor correlation is seen with age, sex, duration or severity of
reactive airway disease, or duration of anesthesia.
Factors that may contribute to bronchospasm include inhaled
stimulants, release of allergic mediators, viral infections,
exercise, or pharmacologic factors (including
α-blockers, prostaglandin inhibitors, and
anticholinesterases). Bronchospasm may also occur during
fiberoptic intubation.
The spasm can be treated with inhalation
of epinephrine or isoproterenol or an α2-agonist
(such as albuterol, metaproterenol, or terbutaline) or by
deepening the level of a volatile anesthetic.
COUGHING AND BUCKING
Two additional adverse responses to
intubation are coughing and bucking. Such responses are
potentially hazardous in cases of increased intracranial
pressure, intracranial vascular anomalies, open-globe injuries,
ophthalmologic surgery, or in cases in which increased
intra-abdominal pressure could rupture an abdominal incision.
Coughing and bucking occur less frequently with the LMA;
however, in the presence of lubricant globules on the anterior
surface of the cuff, light anesthesia or malpositioning, these
adverse reactions may be observed. The incidence of
coughing, gagging and retching has been reported as 0.8% using
an LMA with a fentanyl-propfol-O2-N2O-isoflurane
technique.35
VOMITING, REGURGITATION AND ASPIRATION
The overall incidence of aspiration during
general anesthesia varies and has been reported as 1/2131 (in
Sweden) to 1/14150 (in France), and 1/3216 in the USA, with an
associated mortality of 1/71829 in the USA.36
A meta-analysis of publications concerning the LMA (547
publications) suggested that the overall incidence of pulmonary
aspiration was approximately 2/10000.37
An endotracheal tube and a Combitube are most effective in
preventing pulmonary aspiration. To reduce the risk of pulmonary
aspiration, some new designs of airway management devices were
developed: the ProSeal-LMA and the Laryngeal Tube Suction™.
In any patient considered to have a full
stomach, the likelihood of vomiting in response to irritation of
the airway is increased, and aspiration of stomach contents is a
constant concern. Aspiration leads to coughing, laryngospasm and
bronchospasm, assuming that protective reflexes are intact.
In consequence of these reactions, hypertonia, bradycardia,
asystole and hypoxia may occur. The magnitude of the
pulmonary reactions depends on the type and quantity of the
aspirated material.38
The Sellick maneuver, or cricoid pressure,
has removed much of the fear of emergency intubation.
Cricoid pressure is effective in raising the pressure in the
upper esophageal sphincter, thus preventing aspiration.
INTRAOCULAR AND INTRACRANIAL PRESSURE
With thiopental, etomidate and halothane
anesthesia, an increase in intraocular pressure was
observed during laryngoscopy as well as LMA insertion, but not
with TIVA or remifentanil and sevoflurane. Decreases in
intraocular pressures were observed under endotracheal
intubation during general anesthesia with propofol and
sevoflurane, both combined with remifentanil. Intraocular
pressure may also increase during extubation.
Insertion of an LMA does not increase
intraocular pressure in children after sevoflurane induction.51
Sufentanil is also effective in preventing an intraocular
pressure increase caused by rapid-sequence induction with
succinylcholine.52
It is extremely important that an increase in intraocluar
pressure should be avoided in patients with penetrating eye
injury.
Intracranial pressure markedly and
transiently rises during laryngoscopy and endotracheal
intubation. Patients with head injury are at higher risk
from this increase as it reduces cerebral perfusion and thus may
increase secondary brain damage. Deep anesthesia during
induction can prevent these adverse effects.
LATEX ALLERGY
Almost 17% of overall anaphylaxis in
surgical procedures are related to latex anaphylaxis.39
To prevent anaphylaxis in patients during anesthesia and
surgery, the patient’s history has to be carefully evaluated
preoperatively. There is currently no therapy for latex allergy,
and avoidance of latex-containing products is mandatory for
predisposed individuals.40
Latex allergy is present in 8% of the general population in the
USA, with a prevalence of 30% in health-care workers.41
There is an increased incidence of type I and type IV latex
sensitivity in the general population. The prevalence of
latex sensitivity among anesthesiologists is approximately 12.5%
and of allergy 2.4%.42
Patients with spina bifida, rubber
industry workers, atopic patients, patients with a multiple
surgery history and with certain exotic food allergies are most
at risk. Contamination with latex in anesthesia is
possible through direct contact by face mask,
endotracheal and gastric tubes, gloves, syringes, electrodes;
through inhalation from contaminated circuits and room
air; and through the parenteral path with
latex-containing intravenous administration sets.
Considerations for anesthesiologists
handling patients with latex allergy are available at the ASA’s
website [http://www.asahq.org/publicationsAndServices/latexallergy.pdf].
In a pediatric study, Nakamura et al found that a high
percentage of children with home mechanical ventilation have
undiagnosed latex allergy.43
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