Page 448 - Clinical Small Animal Internal Medicine

416 Section 5 Critical Care Medicine

development of pulmonary edema. Occasionally, acute orthogonal views or performing a limited echocardio-
VetBooks.ir worsening of a previously detected murmur with or gram or thoracic ultrasound rather than a complete
exam to preserve patient safety. In fact, thoracic ultra-
without development of a precordial thrill is present
and may be indicative of rupture of a first‐order chorda
restrain and can produce repeatable results with a small
tendina. sound can often be performed in the ER with minimal
In some instances, as in the case of cardiac tamponade, amount of training. It is extremely disappointing when
the history may be one of subacute progression. Physical patients die during diagnostic procedures so the patient’s
exam findings suggestive of pericardial effusion include condition, stability, and the value of the potential infor-
muffled heart sounds, decreased precordial impulse, mation obtained should be taken into consideration
detection of pulsus paradoxus (although weak pulses are prior to ordering or performing a test.
also common), and presence of jugular pulses. The find- The use of ECG provides real‐time evaluation of the
ing of ascites and a positive hepatojugular reflex is more electrical conductance of the heart and enables the clini-
likely to occur in cases of chronic pericardial effusion cian to determine the source of cardiac depolarization
and may be absent in the patient presenting with cardio- and if a conduction abnormality exists. When evaluating
genic shock. a patient with suspected cardiogenic shock, an ECG
Respiratory distress may or may not occur as a result of should always be obtained. Patients are usually tolerant
cardiogenic shock but respiratory failure is rare. of ECG leads placed with either alligator clips or pads.
Tachypnea is likely to be present as a result of normal The goal of ECG evaluation in this setting is to deter-
compensatory mechanisms to improve oxygen delivery. mine which cardiac cells are acting as pacemaker cells
Significant hypoxia or hypoxemia can occur in situations and if electrical conduction is occurring in an organized
such as pulmonary hypertension or pulmonary edema fashion. Therefore, patients can often be allowed to
due to chordae tendinae rupture. For a more in‐depth remain in sternal recumbency with minimal restraint.
discussion on respiratory failure, the reader is referred to Evaluation of a lead II ECG should enable the clinician to
Chapter 39. answer pertinent urgent questions. A more thorough
six‐lead ECG can be performed if the patient’s condition
is considered stable enough to allow for restraint in lat-
Diagnosis eral recumbency. While the presence of sinus tachycar-
dia will not enable diagnosis of cardiogenic shock (sinus
Unique clinical characteristics of cardiogenic shock tachycardia is expected to occur in most shock states
include concurrent hypotension (systolic blood pressure regardless of etiology), the presence of paroxysmal ven-
<90 mmHg or mean arterial pressure <60 mmHg), tricular tachycardia supports the diagnosis. Additionally,
decreased cardiac output, and elevated central venous or the finding of multiform ventricular ectopy or electrical
left atrial pressures. There is no single diagnostic test alternans may increase the clinician’s suspicion of a car-
that will confirm the presence of cardiogenic shock. diac origin of shock.
Rather, the clinician will be forced to reconcile available Radiography is a useful diagnostic tool and is readily
diagnostic results (limited by patient stability, availability available in most veterinary facilities. When using radi-
within the clinic, and finances) with the patient’s histori- ography in the emergency setting, it is important to keep
cal findings, presenting complaint, and physical exam patient safety in mind, realizing that the quality and
findings to achieve a diagnosis. completeness of the study may have to be compromised
When presented with a patient in cardiogenic shock, to ensure patient safety. Diagnostic radiographs can
the clinician will be faced with the decision about often be obtained with minimal restraint. In fact, patients
whether or not the restraint required to perform a diag- can often be allowed to remain in sternal recumbency
nostic test is going to be tolerated by the patient. while a dorsoventral (DV) projection is obtained. A sin-
Unfortunately, it may be necessary to delay or forego gle lateral or DV projection may provide clues regarding
some diagnostic tests that require restraint due to the the cause of shock (e.g., a globoid cardiac silhouette) but
tenuous nature of the patient’s condition and every effort orthogonal views are always preferred if possible.
should be made to limit stress to the patient. Staging of Animals with rupture of a first‐order chorda may mani-
testing can be helpful, focusing efforts on performing fest fulminant pulmonary edema characterized by the
tests in the order most likely to yield meaningful results. presence of an alveolar lung pattern while animals with
As an example, it would be best to delay collection of cardiogenic shock secondary to ventricular tachycardia
blood in order to obtain even a single thoracic radio- may have no radiographic abnormalities.
graph or an electrocardiograph (ECG). Occasionally, it is Echocardiography can be used to diagnose many of the
necessary to accept less than ideal results for testing causes of cardiogenic shock. The minimally experienced
such as obtaining a single radiographic view rather than ultrasonographer will be able to recognize the presence of