Page 1058 - Cote clinical veterinary advisor dogs and cats 4th

523.e4 Hypotension, Systemic

and increased chronotropy and inotropy; TREATMENT Recommended Monitoring
mechanisms include: Treatment Overview • Monitor BP indirectly (cuff) or directly
VetBooks.ir and adrenocorticotropic hormone from the The primary goal is to treat the underlying monitoring is technically challenging and
(arterial line) until it has normalized. Direct
• Release of antidiuretic hormone (vasopressin)
has possible minor complications, but it has
pituitary
disease, but if results of treatment may not be
• Release of catecholamines from the adrenal
nous fluids or vasoactive medications may be
medulla immediate, restoration of BP using intrave- the benefit of greater accuracy, continuous
measurement, and ability to easily perform
• Renin-angiotensin-aldosterone system necessary. Before initiating these treatments, arterial blood sampling for acid-base and
activation cardiogenic causes of hypotension must be ruled ventilation/perfusion analysis. The dorsal
out because treatment for cardiogenic shock pedal artery in cats is recommended only
DIAGNOSIS may involve decreasing intravascular volume for short-term arterial catheterization (<8
and/or positive inotrope administration. hours) due to risk of limb ischemia; the tail
Diagnostic Overview artery may be safer for long-term use.
Suspicion of systemic hypotension involves Acute General Treatment • Central venous pressure (CVP) can be used
recognition of compatible clinical signs and • Volume replacement selected according to as an indicator of volume status. If CVP is
physical exam findings. Confirmation is done type of fluid lost low (<5 cm H 2 O), more fluids should be
by measurement of arterial BP. Systemic ○ Isotonic crystalloids (lactated Ringer’s given unless pulmonary edema is present.
hypotension in a patient showing overt signs solution, 0.9% NaCl) 40-90 mL/kg IV Adequate fluid resuscitation is present if the
of illness justifies diagnostic testing to identify to effect. Typically given in 10-30 mL/kg CVP is between 5 and 10 cm H 2 O. However,
an underlying cause and initiating treatment to increments as a bolus over 15-20 minutes in left-sided heart disease, fluid-overload
correct the hypotension and underlying disease. followed by reassessment of need for pulmonary edema can occur despite normal
additional boluses CVP.
Differential Diagnosis ○ Synthetic colloids 5-20 mL/kg IV to effect. • Monitor for signs of end-organ damage (e.g.,
Rule out inaccurate measurement (recommend Typically given in 5 mL/kg increments urine output, mentation).
recheck measurement if reading does not fit followed by patient reassessment, similar • If hemorrhage is suspected, monitor hema-
the clinical picture [p. 1065]). to isotonic crystalloids tocrit and total protein.
○ Hypertonic saline 2-4 mL/kg IV to • Monitor ECG if arrhythmias are present.
Initial Database effect. Avoid if patient is dehydrated or
• Indirect or direct arterial BP: to confirm hypernatremic. PROGNOSIS & OUTCOME
and monitor hypotension and as part of ○ Blood, plasma transfusions, as appropriate
evaluation for underlying disorders (p. 1169) • Prognosis depends largely on the underly-
• CBC: white blood cell count, hematocrit, • Positive inotropic support (only after volume ing cause, as well as on initial response to
or platelet count may support diagnosis of resuscitation if low cardiac contractility is supportive treatment.
sepsis or hemorrhage documented or highly suspected and typically • Most patients with a noncardiogenic cause
• Serum biochemistry profile: azotemia may for short-term use only while underlying for hypotension respond to IV isotonic
have a prerenal cause in hypovolemic patients disease is addressed or longer-term agents crystalloids given as boluses.
but may also indicate renal or postrenal can be obtained): dobutamine 5-20 mcg/ • Correction of hypotension within the first
disease. Other abnormalities (e.g., liver kg/min hour of treatment is correlated with improved
enzyme elevations) may be related to the • Vasopressor support (only after adequate outcome.
causes or may be the effects of hypotension. volume resuscitation and if hypotension is • The need for high-dose or multiple vasoactive
• Urinalysis: evidence of primary renal disease suspected to be due to systemic vasodilation) or inotropic medications may imply a worse
(e.g., isosthenuria) or infection ○ Dopamine 7-12 mcg/kg/min prognosis.
• Thoracic and abdominal radiographs: ○ Norepinephrine 0.05-1 mcg/kg/min • Nonresponsive hypotension implies a poor
evidence of pulmonary infiltrates (edema, ○ Epinephrine 0.1-1 mcg/kg/min prognosis, with multiple organ dysfunction
hemorrhage, metastases), pneumonia, ○ Vasopressin 0.1-1 mU/kg/min syndrome (p. 665) a likely outcome.
trauma, or effusions; assess cardiac and vena
cava size Chronic Treatment PEARLS & CONSIDERATIONS
• Ultrasonography: assess for effusions, assess Treatment of the underlying cause (e.g., locate
cardiac function and chamber size, and assist and stop source of hemorrhage, IV antibiotics Comments
in diagnostic paracentesis if indicated for sepsis) • Hypotension is a serious consequence of
• Paracentesis (abdominal, pleural, pericardial): numerous disease processes. Prompt iden-
assess the nature of a patient’s effusion (e.g., Drug Interactions tification and treatment of the underlying
hemorrhage) if present (pp. 1056, 1150, • High-dose or multiple vasopressors may lead cause is essential to a successful outcome.
1164, and 1343) to intense vasoconstriction that could result • Persistent hypotension implies ongoing
in organ ischemia. hemorrhage, systemic vasodilation, decreased
Advanced or Confirmatory Testing • Catecholamines can precipitate cardiac cardiac function, or capillary leakage.
• Invasive BP measurement with an arterial arrhythmias. • If it is necessary to add another pressor agent
catheter attached to a pressure transducer is • Cardiogenic causes of hypotension must due to lack of effect, the new agent should be
ideal for diagnosis and monitoring response be ruled out before IV fluid or vasopressor added without stopping the previous agent
to therapy of critical patients with systemic therapy because these treatments may further and can be gradually discontinued after the
hypotension. This technique can be techni- decrease oxygen delivery and dramatically more potent agent is working.
cally challenging and complications such as worsen patient condition. • It is very unlikely to identify hypotension
thrombosis, hemorrhage, and infection are of any clinical significance in a patient that
possible. Possible Complications appears normal on physical exam.
• Indirect BP measurement techniques may Renal failure, loss of gastrointestinal integrity
be inaccurate compared with direct means with translocation of bacteria and bacterial Technician Tips
but can generally be used serially to monitor toxins, myocardial dysfunction, brain ischemia, • Early identification of systemic hypotension
response to therapy (pp. 1058 and 1065). loss of vascular tone in ill animals can allow prompt intervention.

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