Page 37 - Feline Cardiology

30 Section A: Clinical Entities

endotracheal tube. These silent, gasplike movements of tions. Placing the endotracheal tube should delay
the mouth do not constitute effective breathing, and initiation of chest compressions as little as possible
agonal “breaths” should not delay the administration of and ideally is performed with the cat in lateral recum-
Clinical Entities differentiated from natural death beyond which no mea- B. Breathing. Administer 2 rescue breaths once the
CPCR.
bency while chest compressions are underway.
Cardiopulmonary arrest requiring treatment must be
patient is intubated, followed by administration of
regular artificial breaths; never administer mouth-
sures can revive the patient. This distinction matters
both for medical reasons (e.g., termination of interven-
to-muzzle breaths (risk of agonal bites).
tion at the point of futility) and for emotional, ethical, C. Circulation, compressions. There should be no pal-
and moral reasons (e.g., dignified and humane death). pable pulse (by definition) in the arrested patient,
CPCR is no longer indicated when all of the following requiring external chest compressions. In the cat,
criteria have been met: CPA is confirmed, and CPCR these are administered with the patient in lateral
efforts lasting a minimum of 3 minutes, but often longer, recumbency and either by using one hand (thumb
have not produced a return of spontaneous circulation on one side of the chest, other four fingers on the
or ventilation, and there is no evidence of brainstem other) or with the heel of one hand on the visible
function (pupils are fixed and dilated, and/or there is a side of the chest and the fingers or palm of the other
lack of electrical activity on brainstem auditory evoked on the opposite, dependent side. The position is
response or electroencephalography [EEG]). In human directly over the heart: ventral half of the thorax
medicine, contraindications to CPCR are any of the fol- approximately over the 5th intercostal space, which
lowing: 1) Do Not Attempt Resuscitation order in place; can be identified quickly by flexing the forelimb cau-
2) signs of irreversible death (e.g., rigor mortis, decapi- dally: the point at which the elbow crosses over the
tation, decomposition, or dependent lividity [purplish costochondral junctions is at or near the 5th inter-
discoloration of tissues due to gravity-induced blood costal space. Compression strength should cause the
pooling]); or 3) no physiologic benefit can be expected ribs to depress to approximately 1/3 of the diameter
because vital functions have deteriorated despite of the chest; caution is warranted in older cats
maximal therapy (e.g., progressive septic or cardiogenic with bones that are more brittle, and in general with
shock) (ECC 2005) and such parameters likely are resuscitators who are zealous or excessively forceful
appropriate in feline medicine also. Termination of life and can break ribs, cause pneumothorax or hemo-
support is considered ethically permissible in comatose thorax, and otherwise inflict injuries during CPCR.
patients who, despite optimal treatment, show all the It is helpful to remember that a cat’s heart is slightly
following signs: absent corneal reflex ≥24 hours, absent larger than a man’s thumb, and chest excursions
pupillary light response ≥24 hours, absent withdrawal during CPR generally involve movement of 1–2 cm
response to pain ≥24 hours, and absent motor response of chest width (an inch or so). Persons administering
24–72 hours (ECC 2005); feline patients in this state compressions should change roles every 2–3 minutes
likewise should not receive CPCR. to prevent fatigue.
D. Defibrillation. (Figure 5.2). Electrical defibrillation,
which is the administration of an electrical shock that
TREATMENT
abolishes all cardiac activity so as to allow reemer-
The treatment approach to CPA has recently been gence of the sinoatrial node’s activity as the dominant
updated (ECC 2005; Plunkett and McMichael 2008). pacemaker and thus normal sinus rhythm, is the
The basic premise still consists of instituting CPCR treatment of choice for ventricular fibrillation.
(Figure 5.1). A stepwise process is appropriate: Ventricular fibrillation is characterized by a pattern-
less wavy tracing where no semblance of P, QRS, or T
A. Airway. Assess airway for obstruction, and if present, deflections can be distinguished (Figure 5.3). The rate
remove (foreign body), improve (generally via intu- is usually >400 waves per minute, reflecting electrical
bation), or bypass if necessary (tracheostomy). chaos in the ventricles. Defibrillation must be admin-
Note: a solid mouth speculum must be solidly in istered early for maximal effect; the success of defibril-
place before manipulating an arresting cat’s mouth, lation in humans declines from >99% when
because periagonal bites may be profound and unre- administered in the first minute of fibrillation to
lenting, and extremely harmful to the rescuer or <10% after 10 minutes in the absence of CPCR. The
clinician. process of defibrillation in cats should take less than
If no obstruction is found, endotracheal intuba- 1 minute, and it consists of rapid clip of hair over
tion is warranted for administering artificial respira- both sides of the thorax (10 seconds); application of