Page 398 - Clinical Small Animal Internal Medicine

366 Section 5 Critical Care Medicine

the provision of chest compressions is an inefficient Diagnosing Cardiopulmonary Arrest
VetBooks.ir way to move blood out of the heart and into systemic Prompt recognition of cardiopulmonary arrest is para-
circulation. Even ideal chest compressions are only
capable of generating 25–30% of normal cardiac output
(CO). However, to maximize the efficiency of chest mount to the success of CPR. Therefore any nonrespon-
sive, apneic patient should be immediately evaluated for
compressions, the provider should attempt to achieve CPA and resuscitative measures should be started. The
30–50% compression of the thoracic diameter. Good– clinician should spend no more than 10 seconds
quality chest compressions consist of a 50% duty cycle, attempting pulse detection and cardiac auscultation
meaning 50% of the entire compression cycle is spent before beginning chest compressions. The risk of caus-
with the chest wall being compressed and 50% is spent ing serious injury to a patient by providing unnecessary
allowing the chest wall to recoil. Failure to allow com- chest compressions is quite small. In a study of human
plete recoil of the thoracic wall can result in severe patients receiving unnecessary chest compressions, the
impairment to cardiac filling during the noncompres- injury rate was less than 2% with no life‐threatening
sion phase. It is often helpful to lift the heel of the hand injuries present, leading to the conclusion that the pro-
off the chest wall to ensure that complete recoil has vision of CPR is not harmful, while inaction may prove
been accomplished. fatal.
Hand position during CPR in veterinary patients is not If the patient is found to be only in respiratory arrest
standardized and is left to the individual providing com- following the brief pulse evaluation then the clinician
pressions to find what works best for them. In small dogs should proceed with securing an airway with an endotra-
and cats, a one‐handed technique can be employed by cheal tube or tracheostomy tube. After the airway is
placing the sternum in the palm of the hand with the secure, the patient should be manually ventilated with
thumb and fingers centered over the heart on opposite 100% oxygen. If not already obtained, attempts at venous
sides of the chest. The heart is then compressed between access should be made at this time and the patient should
the thumb and fingers in a rhythmic pattern. For larger be monitored for progression to cardiac arrest. If, on the
dogs, it may be necessary to use one or two hands to other hand, the patient is found to be in cardiac arrest at
achieve the desired amount of chest wall compression. In the time of the pulse check then basic life support (BLS)
small dogs (<15 kg) and cats, the compressions should be should be instituted immediately.
located directly over the heart in an effort to take advan-
tage of direct compression of the ventricles forcing blood
forward through the semilunar valves. This is termed the Basic Life Support
cardiac pump theory. In larger dogs (>15 kg), the com-
pressions should be located at the widest part of the tho- Chest Compressions
rax, realizing that this may be at the caudalmost portion
of the costal arch. In this case, the clinician is reliant on While the definitive order in which BLS measures are
the intrathoracic pressure generated during chest implemented is not established, it is reasonable to con-
compressions to compress the vascular structures in the tinue using the Airway, Breathing, Circulation approach
thorax forcing blood forward. This is called the thoracic in which ventilation precedes compressions. Practically,
pump theory. however, instituting compressions does not require any
An oft‐overlooked facet of chest compressions is equipment and can often be started earlier than an air-
patient positioning relative to the compression provider. way can be secured. Therefore, BLS begins with high‐
It is important that the position of the provider is com- quality chest compressions performed at a rate of
fortable and will allow for the best‐quality compressions 100–120 beats per minute, making every effort to avoid
with the least amount of fatigue. Therefore, having the interruptions. During the first cycle (two minutes) of
patient at approximately waist level or lower is ideal. If chest compressions, the patient should be instrumented
the patient’s position is fixed then the provider should with an electrocardiograph (ECG) and capnography if
stand on a step stool to achieve the desired amount of available. Attempts can also be made to achieve intrave-
leverage. If compressions are provided on a table, the nous access if this has not already been done. Intubating
tabletop should be rigid and would ideally be incapable or securing an airway can be attempted during this first
of conducting electricity. Wet tables should be avoided. round of compressions while minimizing interruptions.
Larger dogs can often be more comfortably resuscitated It is often easier to perform the first cycle of compres-
on the floor with the compression provider kneeling next sions while other members of the arrest team obtain
to the patient. An adjustable height hydraulic table proper sized endotracheal or tracheostomy tubes and
should be considered if CPR is performed on a regular laryngoscope and mobilize the crash cart to the location
basis. of the arrest.