Page 382 - Clinical Small Animal Internal Medicine

350 Section 5 Critical Care Medicine

Oxygenation and Ventilation combination of the two. In addition to pH, PCO 2 and
VetBooks.ir Oxygenation can be assessed by arterial blood gas meas- HCO 3 , lactate levels should be evaluated to assist in
−
identifying the origin of an acid–base disorder. Most
urement (PaO 2 ) or pulse oximetry (SpO 2 ), and allows a
clinician to evaluate how well a patient is moving oxygen hyperlactatemia is the result of impaired oxygen delivery
and rapid resolution is generally associated with better
into the blood. A PaO 2 <80 mmHg or a SpO 2 <96% indi- patient outcome.
cates the need for supplemental oxygen which can be
provided by flow‐by oxygen, nasal oxygen cannula, an
oxygen chamber or endotracheal intubation with 100% Mentation and Intracranial Pressure
oxygen. Ventilation is evaluated by assessing the arterial Close monitoring and documentation of a patient’s men-
PaCO 2 or indirectly by using end‐tidal CO 2 concentra- tation is necessary to allow prompt detection of any
tion. End‐tidal CO 2 monitoring can be used on intubated changes that may indicate progression of intracranial
as well as nonintubated patients using a tight‐fitting disease or a hemodynamic or metabolic disease with
facemask or a nasal cannula. In situations of hypoventila- neurologic consequences. Elevated ICP is common in
tion, hypercarbia (PaCO 2 >60 mmHg) should be treated patients with head trauma and inflammatory encepha-
with supplemental oxygen and mechanical ventilation if litides. It should be remembered that not all mentation
needed. Repeated measurements are required to moni- changes are due to structural changes or ICP alterations.
tor response to therapy.
Hypotension and hypoglycemia can manifest as altered
mentation. Hepatic diseases resulting in encephalopathy
Glucose can lead to neurologic signs that may indicate progres-
sion of a disease process.
Ideally, glucose should be maintained in the normal
range (75–120 mg/dL). Hypoglycemia can manifest as
peripheral weakness, altered neurologic function (obtun- Coagulation
dation, stupor or seizures), and hypotension. Severe Impaired coagulation in the critical patient due to throm-
infection, synthetic liver failure, neoplasia, and hypoad- bocytopenia or clotting factor deficiency is easy to
renocrticism are common causes of hypoglycemia in identify. It is more difficult to evaluate patients for hyper-
critical patients. Young and undernourished animals are coagulability, which can result in thromboembolic
predisposed to developing hypoglycemia. Administration sequela and secondary complications. Hypercoagulability
of supplemental dextrose in IV fluids is indicated if can be due to systemic inflammation from trauma, infec-
normoglycemia cannot be maintained via enteral nutri- tion or neoplasia as well as a multitude of underlying
tion. Hyperglycemia due to diabetes requires exogenous metabolic and endocrine disorders. Advanced diagnos-
insulin administration to prevent ketoacidosis, hyperos- tics, including thromboelastography, are required to
molarity, and dehydration due to osmotic diuresis. fully evaluate a patient for hypercoagulability. As under-
Hyperglycemia associated with trauma is associated with lying conditions predisposing to a hypercoagulable state
a worsening prognosis. Although well described in the are identified, clinicians should weigh the benefits versus
human medical literature, the benefits of tight glycemic risks of initiating thromboprophylaxis.
control for hyperglycemia in veterinary medicine are
unproven and should only be attempted at a 24‐hour
critical care facility. Red Blood Cell and Hemoglobin
Concentration
Adequate oxygen delivery is important for all patients,
Electrolyte and Acid–Base Balance
but is especially crucial for critical patients whose
Critically ill patients often have significant acid–base systems are already taxed by underlying conditions.
and electrolyte disorders that contribute to their overall Hemoglobin is necessary for oxygen transport and deliv-
clinical condition. Important electrolytes to be moni- ery and red blood cell transfusions should be adminis-
tored include sodium, potassium, ionized calcium, chlo- tered in response to clinical signs associated with anemia,
ride, magnesium, and phosphorus. Many disease states including tachycardia, increased respiratory rate, hypo-
are associated with particular electrolyte arrangements tension, and weakness. While there is no standard trans-
and care should be taken to customize monitoring to an fusion “trigger” point, each patient should be individually
individual patient’s signs and diagnosis. Critical patients assessed for the need for a transfusion based on clinical
should have electrolytes monitored at least once daily signs, underlying disease processes, and anticipated
while on IV fluid therapy. Acid–base derangements can losses. Evaluation of venous oxygen saturation may allow
be the result of metabolic or respiratory conditions, or a early identification of inadequate oxygen delivery.