Page 402 - Clinical Small Animal Internal Medicine

370 Section 5 Critical Care Medicine

paddle would be. The assembly is then placed under the much more efficient delivery of blood to the pulmonary
VetBooks.ir patient in lateral recumbency using the normal paddle circulation by spontaneous cardiac contraction than that
achieved during manual chest compressions.
positioning recommendations. A standard paddle is then
Following the initiation of chest compressions and
used on the upward‐facing thoracic wall. This technique
allows the patient to remain in lateral recumbency while attainment of an airway, the patient should be instru-
eliminating the need to clip the area as for defibrillator mented with ETCO 2 monitoring if available. Patients
pads. with higher ETCO 2 levels (15 mmHg dogs, 20 mmHg
Nonelectrical methods of cardiac defibrillation include cats) are more likely to have ROSC than those with lower
both chemical and mechanical means. Historically, levels. During CPR, if ETCO 2 is less than 15 mmHg,
chemical defibrillation with magnesium or antiarrhyth- efforts should be made to improve the quality of chest
mic drugs has been considered acceptable. Based on the compressions. If compression providers have not been
current understanding of CPA in both human and veteri- rotated and ETCO 2 is found to be low or is decreasing, a
nary patients, the use of antiarrhythmic agents is no rotation should be considered.
longer routinely recommended. Among the possible Blood gas monitoring during CPR is challenging but is
agents available, only amiodarone has been found to be the only way to identify the severe electrolyte and acid–
routinely effective. Magnesium salts have only proven to base derangements that are common during CPA.
be useful for the treatment of torsades de pointes and Ideally, a blood sample (venous or arterial) is obtained
electrical defibrillation should always be considered as shortly after the onset of CPA and is evaluated for any
the best option for ventricular fibrillation or pulseless abnormalities. Interventions should be directed at
ventricular tachycardia. The use of a precordial thump severely abnormal results, understanding that complete
has been described as a method for providing mechani- resolution is not likely and may not be necessary. If sam-
cal defibrillation. Given the superiority of electrical pling is possible, blood gas analysis should be performed
defibrillation, a precordial thump should only be consid- every 5–10 minutes during CPR as long as collection of
ered if a defibrillator is not available. samples does not interfere with the actual provision of
rescue efforts. Information regarding acid–base and
electrolyte status during CPA and outcome is lacking
Monitoring During CPR and should not be used to predict the likelihood of
ROSC.
Monitoring during CPR can be difficult due to lack of
normal physiologic responses. The two modalities
most useful during CPR are ECG and capnography. Open Cardiac Massage
Electrocardiography is monitored to determine if an
arrest rhythm is amenable to defibrillation while ETCO 2 Open chest cardiac massage is capable of generating bet-
can be utilized as a measure of the effectiveness of chest ter cardiac output during CPR than closed chest com-
compressions, as an adjunct to verify placement of the pressions. However, the procedure is invasive and
endotracheal tube, and to determine when ROSC occurs. requires significant resources both during and after
Traditionally, patients with CPA would be subjected to resuscitation. Therefore, its use is reserved for patients
pulse detection attempts before and during CPR. with a clear indication including significant intrathoracic
Unfortunately, pulse detection takes time, is technically disease (tension pneumothorax, severe pleural effusion),
difficult in some cases and can lead to increased “hands‐ major chest wall defect (flail chest) or pericardial
off” time, with the patient receiving fewer chest com- effusion.
pressions. Capnography has allowed CPR providers a To perform open chest CPR, the patient is placed in
method to monitor not only the effectiveness of chest right lateral recumbency. The fur is rapidly clipped over
compressions but also whether or not ROSC has the 4th–6th intercostal spaces and the skin is quickly
occurred. Following CPA, blood flow through the pul- wiped with alcohol. The skin is incised at the 5th–6th
monary circulation decreases rapidly and ETCO 2 levels intercostal space with a scalpel blade. The intercostal
drop to near 0 since carbon dioxide is not being returned muscles are incised with Mayo scissors and the incision
to the alveoli for exhalation. During CPR, pulmonary is extended from the costochondral junction to the prox-
blood flow is generated by chest compressions. Therefore, imal one‐third of the rib. Care should be taken to avoid
any change in ETCO 2 levels can be attributed to the laceration of the lung tissue during this process.
cardiac output achieved by the chest compressions, pro- Respiration can be temporarily held during this time to
vided the minute ventilation is held constant. ETCO 2 is further reduce the risk of iatrogenic trauma to the lung.
also useful for the detection of ROSC, with a rapid and The ribs are then spread with manual retraction or a
sustained rise in ETCO 2 indicating ROSC due to the Fineccheto retractor. The pericardial sac is incised at the