Page 399 - Clinical Small Animal Internal Medicine

37 Cardiopulmonary Resuscitation 367

Following the first round of compressions, the first dorsally. Successful intubation can be confirmed by
VetBooks.ir ECG rhythm check will be performed and a definitive direct visualization of the endotracheal tube between the
arytenoid cartilages or visualization of normal chest rise
attempt will be made to secure an airway. The purpose of
the rhythm check is to determine if a cardiac rhythm
be useful but should not be used as the sole means of
may be amenable to electrical conversion. If no such during positive pressure ventilation. Capnography may
rhythm is identified then chest compressions are imme- confirming correct placement of an endotracheal tube
diately resumed. Ideally, the chest compression provider during CPA since end‐tidal CO 2 in CPA patients may be
is changed at this time. This two‐minute cycle is repeated 0 due to lack of pulmonary blood flow.
as needed, alternating the compression provider at each Once an endotracheal tube is placed and correct posi-
planned rhythm check (i.e., every two minutes) or sooner tioning is confirmed, the tube should be secured to the
if fatigue occurs. patient with tape, gauze tie or rubber band to prevent
There are four arrest rhythms, two of which are respon- tube dislodgment. The cuff on the endotracheal tube
sive to electrical defibrillation: pulseless electrical activity should be inflated to ensure an airtight seal. This will
(PEA), asystole, ventricular fibrillation, and pulseless ven- allow the patient to be effectively ventilated with positive
tricular tachycardia. The most common arrest rhythms pressure during chest compressions. In some cases, oro-
in veterinary medicine are asystole, which accounts for tracheal intubation may not be possible due to severe
72% of arrest rhythms, and pulseless electrical activity, swelling, inability to open the mouth or severe facial
neither of which is responsive to defibrillation. trauma necessitating emergency tracheostomy.
Interruptions in chest compressions must be mini-
mized during CPR. Following each interruption in chest Ventilation
compressions, it takes approximately 60–90 seconds to
return CO to the preinterruption level. Eliminating Positive pressure ventilation with 100% oxygen is begun
hands‐off time is therefore a major focus in improving once an airway is secured. Breaths can be provided by a
both veterinary and human CPR. Minimizing interrup- number of means, including rescue bag, anesthesia
tions during CPR must be balanced with the need to machine or mechanical ventilator. Hyperventilation is
prevent compression provider fatigue. Many studies in common in the clinical CPR scenario and can be caused
human CPR providers document a tendency to lean dur- by an excessive respiratory rate, tidal volume or inspira-
ing the provision of chest compressions. This tendency tory time. Regardless of the cause, hyperventilation is
increases as the duration of compressions increases. The detrimental to outcome. During positive pressure venti-
effect of leaning on a patient during CPR decreases car- lation, venous return occurs during the expiratory phase
diac filling and the overall efficiency of CPR by at least and if insufficient expiratory time is allowed (due to
25%. CPR is hard work and two minutes of high‐quality either excessive rate or inspiratory time), cardiac filling
chest compressions on even a small to medium‐sized will be reduced. Hyperventilation can also lead to
dog should be exhausting. decreased cerebral carbon dioxide levels and subsequent
cerebral vasoconstriction, further impairing blood flow
to the brain during the critical time of resuscitation.
Airway
No clear association has been made regarding the tim-
Orotracheal intubation of dogs and cats is relatively easy, ing of rescue breathing with compressions and it is not
making rapid intubation possible in most circumstances. recommended to attempt to synchronize breaths with
In the majority of patients that experience cardiopulmo- compressions. Current recommendations for ventilation
nary arrest, an airway can be secured via routine orotra- are a rate of 8–10 breaths per minute with a tidal volume
cheal intubation. Occasionally, the glottis is obscured by of approximately 10 mL/kg and an inspiratory time of
vomit, fluid or saliva. If suction is available, it can be one second. Assigning the role of rescue breathing to a
helpful in clearing the oropharynx of excess fluid. If suc- single team member and providing them with clear
tion is unavailable a gauze 4 × 4 or paper towel can be instructions on ventilation rates is the best way to prevent
used to swab the area free of fluid or debris. Care should hyperventilation.
be taken to avoid excessive manipulation of the epiglottis
as this can induce a vagal response. A laryngoscope
should be used to facilitate intubation. Advanced Life Support
If the glottis cannot be visualized, the orotracheal
route may still be considered for intubation if the epiglot- Advanced life support (ALS) consists of all resuscitative
tis can be palpated. A blind intubation is performed by measures that are not included in the BLS algorithm,
palpating and depressing the tip of the epiglottis and including vasopressor therapy, vagolytic therapy, fluid
directing the endotracheal tube through the glottis and electrolyte therapy, and electrical defibrillation.