Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_885_Библиотеки_им_академика_М_И_Перельмана.pdf
198 M. M. Sawyer
Airway equipment/management
• The advent of the video laryngoscope has helped to revolutionize modern
airway management. While knowledge of the fiber optic bronchoscope is
helpful in the ICU, when fiber optic assistance is needed, the anesthesiologist
presence is mandatory.
• It is useful to be facile with the basic laryngoscope blades, the utility of the
Laryngeal Mask Airway, and the percutaneous cricothyrotomy kit as well.
• The ASA difficult airway algorithm depicts a step wise approach to management of the difficult airway. At DHMC, we consider all ICU intubations
difficult airway intubations for the reasons previously described.
• In our ICU each intubation plan is accompanied by the Respiratory therapy
team, anesthesiology either on standby or in the room, and a uniform ICU
intubation tray.
• These trays are prepackaged and checked frequently to make sure they are
stocked and that batteries have been changed.
• Medications to be used are chosen based on the physiologic state of the
patient, and from agreement between both the ICU and Anesthesiology
services.
• After pre-oxygenation, as best as possible the patients is induced.
• The decision on the use of depolarizing versus non-depolarizing neuro-
muscular blockade, as well as the need for fiber optic back up requires close
communication between the ICU and Anesthesiology services.
• Generally, the ICU intubation is done in a rapid sequence fashion unless
contraindicated either by airway issues (requiring awake fiber optic assistance)
or neurologic issues (burn injury, spinal cord injury, prolonged immobilization).
• A simple method to follow for the ICU physician is the ‘Pop, Drop, and Roll’
3-step intubation.
{ (1) As much as possible, attempt to ‘Pop’ the mandible open while being
sure to not greatly sublux or dislocate the mandible.
{ (2) ‘Drop’ the laryngoscope as far into the posterior pharynx as possible.
Being mindful to not attempt to visualize the vocal cords at this point
because, as with most any instrument used in the OR, the laryngoscope must
be set up correctly to work correctly. All too often, untrained practitioners
attempt to visualize the epiglottis and vocal cords before the blade is deep
enough. By placing the blade in until the posterior pharynx is contacted,
the blade will be assumed to be deep enough to view the epiglottis and
vocal cords when the oropharangeal, laryngeal, and pharyngeal axis are
aligned.
Airway Management 199
{ (3) If not contraindicated, gently roll the patient’s head back to align the
three axis in play for intubation.
{ These steps should allow the laryngoscope blade to be resting near the
epiglottis, and is a simple strategy for manipulating an airway for those
with limited airway experience.
• Management of the difficult airway in the ICU follows the difficult airway
exam put forth by the ASA. The one caveat is swift decision and timely use
of alternative measures. This includes early change from laryngoscopy to
video laryngoscopy.
• The use of the LMA, while essential for airway management and a critical
part of the difficult airway algorithm, can only be considered a temporizing
agent in the ICU.
• Therefore, if intubation has failed and video laryngoscopy has failed, an LMA
may help in the short-term but is not a long-term answer.
• The LMA will allow the ICU/Anesthesia team to create a new plan, or allow
short-term management while a surgical airway is obtained.
• To that end, the decision to move towards a surgical airway should be part of
every conversation and this decision should become a swift action if there is
airway difficulty.
• Overall at DHMC, the key is our easy communication between services, an
Airway Care Plan, access to advanced airway tools and personnel and our
close approximation between the OR and ICU.
• This allows Anesthesiology to easily help in management of the difficult
airway, as well as to discuss management with the ICU team.
Extubation
• Both the intensive care literature and the anesthesiology literature have
exhaustive algorithims for intubation of the challenging airway. But there is
very scant knowledge guidelines for the extubation of these difficult
patients.
• A similar level of vigilance is required for the safe extubation of the
previously ventilated patient as there has been for the safe intubation of the
ICU patient.
• In fact, extubation should be considered more dangerous than intubation and
studies have shown greater complications during extubation.
• The ASA guidelines for management of the difficult airway do not give any
concrete guidelines for extubation.
200 M. M. Sawyer
• Traditional extubation criteria should be applied if possible and correlated to
the clinical picture of the patient. These include:
{ Following commands
{ Clear oropharynx with intact gag refl ex
{ 5 second head lift/ hand grasp
{ Vital capacity > = 10 ml/kg
{ NIF > 20 cmH
{ Tidal volume > 6 cc/kg
{ Arterial Blood gas showing adequate oxygenation
O
2
• One should realize that the majority of ICU patients that are intubated are
actually intubated before they are brought to the ICU, hence a review of the
previous airway notes are essential before embarking on routine extubation.
• Extubation should be addressed with the plan already in place for possible
failure and urgent reintubation.
• It is best done during the day shift.
• If trial extubation over an airway exchange catheter is planned. Anesthesia
should be at bedside, this is a advanced technique that is not commonplace.
• Simply, extubation should include members of the ICU team, respiratory
therapy team and anesthesiology should be present when there is a possibility
of failure if the Airway Care Plan indicates a difficult airway.
Airway Management 201
Practical Algorithm(s)/ Diagrams
Fig. 1. Pharmacokinetic properties of commonly used anesthetics.
Fig. 2. Wilhelm and Kreuer, Crit Care 2008 12(Suppl 3): S5.
202 M. M. Sawyer
Fig. 3. Patient responsiveness to increasing partial pressure of carbon dioxide.
• The curve is a basic CO
increasing CO
, as sedation is administered the patient’s ability to maintain respiratory
2
drive in the face of increasing PaCO
• From MG Levitzky, Pulmonary Physiology, 5
response curve, it illustrates the patient responsiveness to
2
is diminished.
2
th
.
Fig. 4. From (Miller’s Anesthesia 6th Edition).
Airway Management 203
Fig. 5. ASA Task force 2003 difficult airway algorithm.
204 M. M. Sawyer
Review of Current Literature with References
• Current literature consists mainly of hospital specific experiences and retrospective studies.
• The addition of more user friendly advanced airway tools such as the video
laryngoscopes have been helpful in the ICU.
• Most of these studies have similar plans to what is done at Denver Health. Our
adoption of close communication and team approach toward the Airway Care
Plan helps to ensure that less surprise airway emergencies occur.
• Some have advocated for a specific airway cart with every airway tool
available. We feel that by limiting these devices, it prohibits the undertrained
resident or ICU personel from inadvertanly getting into a difficult situation.
This will ensure that the lines of communication remain open for these
difficult patients.
Chapter 6-(ii)
Acid-Base Physiology
Dominykas Burneikis, MD* and Fredric M. Pieracci, MD, MPH
* Medical Student, University of Colorado School of Medicine
†
Acute Care Surgeon, Denver Health Medical Center
Take Home Points
• Acid-base disturbances are always a consequence of an underlying disease
process or metabolic derangement.
• Correctly interpreting the arterial blood gas (ABG) aids in identifying the
underlying disease process so that it can be addressed appropriately.
Background
• Acid-base physiology incorporates processes that increase or decrease [H+] in
blood.
†
Contact information: (Dominykas Burneikis) 12631 East 17th Ave, MSC313, Aurora,
CO 80045; Tel.: 720-220-2053, (Fredric M. Pieracci) Denver Health Medical Center, 777
Bannock Street, MC 0206, A388, Denver, CO 80206; Email: dburneikis@gmail.com;
Fredric.pieracci@dhha.org
205
206 D. Burneikis and F. M. Pieracci
• [H+] in extracellular fluids is represented by the pH, which is defined by the
following equation:
{ pH = −log
10
[H+]
• pH is tightly regulated, and relatively small derangements have profound
physiologic consequences on cardiovascular, hematologic, and endocrine
homeostasis.
• In blood, the ratio of PCO2 to HCO3 determines [H+], and thus pH. This rela-
tionship is classically defined by the Henderson-Hasselbach equation:
{ pH = 6.1 + log
([HCO3]/0.03 × [PCO2])
10
• Combining the above equations, a simplified relationship between [H+],
HCO3, and PCO2 can be derived:
+
{ [H
] = 24 × ([PCO2]/[HCO3])
• PCO2 is regulated primarily through ventilatory gas exchange at the level of
the alveoli, while changes in HCO3 are directed by the proximal tubules in the
kidneys.
• Whereas changes in minute ventilation rapidly change PCO2 (seconds to
minutes), changes in HCO3 reabsorption occur over the course of days.
• Normal values of pH, PCO2, and HCO3 are: 7.40, 40 mmHg, and 24 mEq/L
respectively.
• Acidosis and alkalosis refer to the processes that lead to states of low and high
blood pH (acidemia or alkalemia respectively).
• A patient is acidemic when blood pH < 7.38, and alkalemic when blood
pH >7.42.
• ABG analysis yields values of pH, PCO2 and HCO3, which are key in identi-
fying primary disturbances of acid-base balance and evaluating secondary
compensatory responses.
Main Body
I. Common indications for ABG:
• Admission to the ICU
• New onset hypoxia, acute respiratory failure, or clinical deterioration of a
mechanically ventilated patient
• Shock
• Intracranial hypertension
Acid-Base Physiology 207
II. ABG interpretation
Primary acid-base disturbances
• Check the pH to determine whether the patient is acidemic (pH < 7.38) or
alkalemic (pH > 7.42).
• Check PCO2 and HCO3 to identify the primary driver of acid-base distur-
bance (metabolic vs. respiratory).
• If the patient is acidemic (pH < 7.38) and PCO2 is elevated (>40), then the
primary disturbance is respiratory acidosis. Alternatively, if the patient is
acidemic and HCO3 is decreased (<24), then the primary disturbance is metabolic acidosis.
• In cases of severe acidemia, both respiratory and metabolic acidosis can be
present simultaneously. Such acid-base disturbance is easily identified
without accounting for compensatory response, as PCO
HCO3 < 24.
• If the patient is alkalemic (pH > 7.42) and PCO2 is decreased (<40), then the
primary disturbance is respiratory acidosis. Alternatively, if the patient is
alkalemic and HCO3 is increased (>24), then the primary disturbance is
metabolic alkalosis.
• As with acidemia, severe alkalemia can be the result of compound respiratory
and metabolic alkalosis (PCO
< 40 while HCO3 > 24). There is no need to
2
account for compensatory response in such cases.
• It is possible to see normal pH (7.38 < pH < 7.42) in the context of equal-andopposite metabolic disturbances, as in metabolic alkalosis and concomitant
respiratory acidosis.
is >40 while
2
Compensatory responses and mixed acid-base disorders
• To offset the changes in pH produced by the primary acid-base disturbance,
the body mounts a secondary response by adjusting either PCO
lungs and kidneys, respectively.
• The degree of compensatory response can be predicted and should be calculated in order to identify any co-existing primary acid-base disturbances.
• In metabolic acidosis and metabolic alkalosis, PCO
should decrease and
2
increase, respectively, by the amount predicted in Table 1. If actual PCO2 is
less than predicted, then a concomitant respiratory alkalosis may be present.
Alternatively, if actual PCO2 is greater than predicted, then a coexisting respiratory acidosis must be considered.
or HCO3 via
2