Plus-Hex CLINICAL
Concentric hypertrophy resulting from HCM may not result in substantial alteration to the cardiac silhouette , and left atrial enlargement in cats cannot be appreciated on lateral radiographs to the extent that it can in dogs , due to a cranial location resulting in superimposition on the cardiac silhouette [ 4 ] .
Blood pressure
BP measurement was performed to rule out systemic hypertension , which could be related to ventricular hypertrophy , or systemic hypotension , which could indicate severe dynamic left ventricular outflow tract obstruction . As furosemide therapy and treatment with ACE inhibitors can also lower BP , it was important to establish a baseline prior to treatment .
BP was measured from the tail with the patient in sternal recumbency , with a size 2 cuff , which was approximately 30 % of the circumference of the base of the tail . A total of 10 readings were taken , with the first three discounted and the following seven consecutive consistent readings averaged to give a systolic BP of 135 mmHg , which was within normal limits .
Initial medical management
Three initial treatments to stabilise patients with CHF are oxygen therapy , thoracocentesis ( if required ) and diuresis .
Furosemide is a loop diuretic , which acts on the thick ascending loop of Henle , resulting in the loss of sodium , chloride and water via excretion into the urine . It is the most commonly used diuretic drug in veterinary medicine . Dosage is based on the minimum effective dose to achieve diuresis while minimising the adverse effects of the drug . This is especially important in feline patients , which are more sensitive to these effects , which include further activation of the renin – angiotensin – aldosterone system ( RAAS ), leading to dehydration , volume depletion , azotaemia and potassium loss . For this reason , monitoring of renal parameters and electrolytes is essential in these patients .
Constant-rate infusions ( CRIs ) allow for less handling of the patient , which can be beneficial in nervous or anxious patients which are not responding to bolus administration , and can result in greater diuresis than bolus administration [ 5 ] . This should not be given in IV fluid , which is contraindicated in patients with severe heart disease due to the risk of fluid overload , which can precipitate or worsen heart failure .
Doses for the acute treatment of CHF to reduce fluid accumulation are higher than those used for preventing its build-up in chronic management . Once the respiratory rate reduces , the dose is tapered . As soon as the patient is eating and drinking , it can be transitioned to oral therapy .
Furosemide was administered , with an initial dose of 1 mg / kg ( 6.55 mg ) IV q2h , as the respiratory rate remained over 60 breaths / min . The respiratory rate increased , despite aggressive treatment with furosemide , so the patient remained hospitalised .
The patient was anxious and there was a concern that the increased respiratory rate may be partly due to stress , so a CRI of furosemide was started at a rate of 0.25 mg / kg / h ( 1.65 mg / h ) and the patient remained in the oxygen kennel .
Hourly hands-off observations of respiratory rate and effort were scheduled to be taken overnight , with reassessment planned the following morning .
Initial nursing care
In contrast to protocols for most emergency cases , intravenous catheterisation and diagnostic tests should not be performed until the patient has been given time to stabilise . Patients should be placed in an oxygen kennel in a quiet area , following administration of diuretics and anxiolytics , if necessary . An easily accessible litter tray with plenty of litter should be provided . As diuresis increases urination , fresh water should also be provided , as increased urine output may increase the patient ' s thirst .
Hands-off monitoring is advised in order to minimise patient stress during this time , as well as to prevent a drop in oxygen concentration each time the oxygen kennel is opened .
Respiratory rate and effort and patient demeanour are the main parameters to be monitored at this stage , and should be recorded clearly every 15 – 30 min initially . For patients where nursing care is shared by more than one person , or when care is handed over during shift changes , it can be useful to assess the patient together . Parameters such as respiratory effort can be subjective .
Cardiac patients require gentle handling to minimise stress . Increased stress levels trigger the sympathetic nervous system ( the ‘ fight or flight ’ response ), which can result in vasoconstriction , increased heart rate and increased myocardial oxygen demand , all of which have a detrimental impact on the heart .
For this reason , hands-on measurements such as heart rate , temperature , oxygen saturation ( SpO 2
) and BP monitoring should be avoided until the patient is stable enough to tolerate handling without it having a negative impact on respiratory rate and effort . Even at this stage it should be kept to a minimum . When assisting with further diagnostic tests , minimal restraint should be used , wherever possible .
Echocardiography is generally performed without sedation . By maintaining a calm environment , using
Volume 38 ( 4 ) • August 2023
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