Page 254 - Clinical Small Animal Internal Medicine

222 Section 3 Cardiovascular Disease

pedal artery is most frequently used for anesthesia and read BP accurately at high heart rates (>180 bpm) or if an
VetBooks.ir postanesthesia monitoring, but is typically impractical arrhythmia is present, and a Doppler or invasive meas-
urement system should be used in these patients.
for clinical use on conscious patients for diagnostic pur-
poses. Direct femoral puncture may be used for acute
results in a given patient, nor will different measure-
measurement of BP in conscious animals with local Doppler and OSC devices may not deliver the exact same
anesthesia, but is time‐consuming and cumbersome in ments sites in the same patient deliver the exact same
clinical practice. results for SBP. Therefore, the same technique and the
same cuff site should be used consistently in a given
Doppler Sphygmomanometry patient when monitoring BP over time.
Doppler sphygmomanometry (DS) is the most common
method of measuring BP in cats and is also used com-
monly in dogs. A piezoelectric crystal attached to an Therapy
audio amplifier is applied to the skin overlying a periph-
eral artery and an occlusion cuff inflated with a pressure Acute or chronic HT may result in life‐altering or life‐
bulb is positioned proximally on the same limb. The BP limiting TOD and may affect the quality and therefore
cuff is premeasured and sized such that the width of the length of life in an affected patient. The goals of HT ther-
cuff is approximately 40% of the circumference of the apy are to stop or limit the extent of TOD in affected ani-
limb at the level of cuff placement. mals and to improve the quality of life in all patients. This
In dogs and cats, the forelimb is the most common may be accomplished by use of medications that decrease
measurement site with the animal in lateral recumbency SBP and concurrent therapy of underlying causative dis-
or sitting and the limb held at the level of the right atrium. ease. In all cases, control or resolution of the underlying
The cuff is placed at mid‐antebrachium and attached to condition is an important part of HT management.
the sphygmomanometer. The probe (with coupling gel)
is held or taped in place over an artery distal to the cuff Medical Therapy
(usually the palmar arterial arch) and the position is
adjusted until a clear pulsatile audio signal can be The goal of therapy of HT is reduction of SBP to
detected. The cuff is inflated to approximately <160 mmHg, and ideally to 120–140 mmHg. Optimal
20–40 mmHg past the point at which the sound of blood therapy of HT usually involves use of a direct vasodilat-
flow is occluded and then slowly deflated. The pressure ing agent (e.g., amlodipine or hydralazine) along with an
at which the sound signal reappears is recorded as the agent to prevent reactive stimulation of the RAAS (usu-
systolic BP. As the cuff is further deflated, the audio sig- ally an angiotensin‐converting enzyme inhibitor [ACEI]
nal will become muffled – this pressure may be recorded or more recently, angiotensin receptor blockers [ARBs],
as diastolic BP but is less reliable than the systolic BP by e.g., telmisartan).
this method. Three to five repeated measurements taken In cats, amlodipine (0.625–1.25 mg per cat PO q24h) is
approximately 30 seconds to one minute apart can be often successful as a single agent to control HT, with
averaged to render a representative SBP. minimal side‐effects in most patients. In dogs, ACEIs
(enalapril or benazepril 0.25–0.5 mg/kg PO q12–24h) are
Oscillometry (OSC) useful in decreasing proteinuria commonly associated
Oscillometric BP devices deliver systolic, diastolic, and with HT and are typically considered a first‐line agent to
mean BP values as well as heart rate. These systems are treat HT of any etiology. Angiotensin‐converting enzyme
most reliable in cats when a tailhead cuff is used in unre- inhibitors alone may not bring BP into the desired range
strained sternal recumbency, but forelimb (radial level), in dogs and amlodipine (0.2–0.4 mg/kg PO q24h) or
hindlimb (metatarsal level or proximal to hock in recum- hydralazine (0.5–2.0 mg/kg PO q12h) may be added. The
bent animal) or tailhead (in standing or recumbent ani- once‐daily dosing regimen of amlodipine makes use of
mals) cuffs may be used in dogs. this drug more appealing than twice‐daily dosing with
The cuff width is chosen similarly to the DS technique. hydralazine in most patients. Telmisartan has recently
The cuff is positioned with the bladder of the cuff (usu- been approved for therapy of HT due to CRD in cats and
ally identified on the cuff by a small arrow) centered expected decreases in SBP are similar to those expected
squarely over the artery and secured. The OSC machine with amlodipine therapy. Spironolactone (1–2 mg/kg PO
is set to read BP at approximately one‐minute intervals. q12h) has theoretical benefits in limiting RAAS activa-
The arithmetic mean of 3–5 SBP replicates is used as a tion in chronic HT, but studies supporting improved
representative value, with any obvious erroneous or out- quality of life or survival outcomes with this medication
lying values discarded. OSC equipment may be unable to are lacking at this time. Beta‐blocking medications like