Hypertension, Fluids and Electrolytes

Blood Pressure Drugs, Fluids, and Electrolytes

• Objectives include comparing hypertension types, describing treatment protocols, comparing pharmacological management drugs, discussing nonpharmacological management, and reviewing fluid volume functions.
• Also includes identifying electrolytes and disorders, identifying solutions for deficiencies/excesses, discussing solution mechanisms, and comparing solutions to expand/decrease fluid volumes.

Blood Pressure (BP) Basics

• Blood pressure is calculated as cardiac output (CO) multiplied by systemic vascular resistance (SVR).
• Hypertension is defined as high blood pressure.
• High-normal BP involves a systolic reading of 130–139 mm Hg or a diastolic reading of 85–89 mm Hg.
• Approximately 7.5 million Canadians are affected.

Hypertension Etiology

• Essential hypertension is idiopathic or primary, and represents 90–95% of cases.
• Secondary hypertension accounts for 5–10% of cases.
• Common causes of secondary hypertension includes pheochromocytoma, pre-eclampsia, renal artery disease, sleep apnea, thyroid disease, or parathyroid disease.
• Malignant hypertension is a medical emergency, indicated by BP exceeding 180/120.

Antihypertensive Medications

• Used to treat hypertension and includes adrenergic drugs, ACE inhibitors, ARBs, calcium channel blockers and diuretics.

Adrenergic Drug Subcategories

• Adrenergic drugs have five subcategories including: adrenergic neuron blockers, alpha-2 receptor agonists, alpha-1 receptor blockers, beta-receptor blockers, and combination alpha-1/beta-receptor blockers.

Centrally Acting Adrenergic Drugs

• Clonidine and methyldopa are centrally acting adrenergic drugs.
• Centrally acting drugs decrease norepinephrine production and stimulate α2-adrenergic receptors to reduce renin activity in the kidneys, resulting in decreased BP.
• Peripherally acting drugs block α1-adrenergic receptors, decreasing BP by dilating arteries and veins.

Alpha 2-Adrenergic Receptor Stimulators (Agonists)

• Clonidine and methyldopa are not typically first-line antihypertensive agents.
• Adverse effects includes fatigue, dizziness and orthostatic hypotension.
• Functions as adjunct drugs for hypertension treatment after other drugs have failed, and are often used with diuretics.

Beta-Blockers

• Beta-blockers include propranolol, metoprolol, and atenolol.
• Reduce heart rate through β1-receptor blockade.
• Causes reduced secretion of renin.
• Long-term use results in reduced peripheral vascular resistance.

Adrenergic Drugs Adverse Effects

• High incidence of orthostatic hypotension, sleep disturbances, nausea, rash, and cardiac disturbances may occur.
• Bradycardia, dry mouth, drowsiness, constipation, depression, edema, sexual dysfunction, and headaches also occur.

Angiotensin-Converting Enzyme (ACE) Inhibitors

• ACE inhibitors are safe and effective drugs often used as first-line agents for heart failure (HF) and hypertension.
• ACE inhibitors includes ramipril, captopril, enalapril, perindopril, and quinapril.
• ACE inhibitors may be combined with a thiazide diuretic or calcium channel blocker.

ACE Inhibitors - Mechanism and Indications

• ACE Inhibitors inhibits ACE, responsible for angiotensin I to angiotensin II conversion.
• They treat hypertension and HF if used alone or combined with diuretics.
• ACE inhibitors can slow left ventricular hypertrophy after myocardial infarction (MI) and offers renal protection for individuals with diabetes.

ACE Inhibitors Cardiovascular Effects

• ACE inhibitors reduces BP by decreasing systemic vascular resistance (SVR) and promotes sodium and water excretion by inhibiting aldosterone secretion.
• They decrease blood volume through diuresis, and reduces heart workload by reducing preload - the left ventricular end-diastolic volume.

Renal-Protective Effects of ACE Inhibitors

• ACE inhibitors Reduce glomerular filtration pressure
• They are cardiovascular drugs of choice for patients with diabetes.
• Reduces proteinuria
• Functions as standard therapy for diabetic patients aimed at preventing diabetic nephropathy progression.

ACE Inhibitors - Adverse Effects

• Fatigue, dizziness, headache, and impaired taste may occur.
• Other side effects include mood changes, first-dose hypotension, hyperkalemia, dry cough reversible with therapy cessation, angioedema and other effects.

Angiotensin II Receptor Blockers (ARBs)

• Also referred to as angiotensin II blockers and are well tolerated.
• ARBs affect vascular smooth muscle and the adrenal gland, and selectively block angiotensin II binding to type 1 receptors; also blocks vasoconstriction and aldosterone secretion.
• ARBs do not cause dry cough.

Angiotensin II Receptor Blockers (ARBs) Details

• ARBs includes losartan, eprosartan mesylate, valsartan, candesartan cilexetil, olmesartan, telmisartan, and azilsartan medoxomil potassium.
• Use is beneficial for those with hypertension and HF but with caution in patients with renal or hepatic issues and renal artery stenosis.
• ARBs are contraindicated for breastfeeding women.

Comparison of ACE Inhibitors and ARBs

• Appears to be equally effective for hypertension treatment.
• Evidence shows ARBs are better tolerated than ACE inhibitors and are associated with lower mortality after MI.
• Both ARBs and ACE Inhibitors are well tolerated
• ARBs do not cause cough.
• Not yet clear if ARBs provide same cardioprotective effects in heart failure compared to ACE inhibitors

Adverse Effects of ARBs

• Common adverse include upper respiratory infections and headaches
• Also includes dizziness, inability to sleep, diarrhea, dyspnea, heartburn, nasal congestion, back pain, and fatigue.
• Hyperkalemia is less likely compared to ACE inhibitors.

Calcium Channel Blockers

• Primarily treats hypertension and angina.
• Reduces BP by relaxing smooth muscle and inhibiting calcium binding, decreasing smooth muscle tone and SVR.

Specific Calcium Channel Blockers

• Include Verapamil, Nifedipine, Diltiazem and Amlodipine.

Calcium Channel Blockers - Indications

• Indicated for angina, hypertension specifically amlodipine, antidysrhythmias, migraine headaches, Raynaud's disease and, nimodipine for cerebral artery spasms after subarachnoid hemorrhage.

Diuretics

• First-line antihypertensives according to Canadian Hypertension Education Program guidelines.
• Reduces BP by lowering plasma and extracellular fluid volumes, decreasing preload, cardiac output, and total peripheral resistance, thus reducing heart workload.

Classification of Diuretics

• Loop diuretics such as Furosemide/Lasix, osmotic diuretics like Mannitol, potassium-sparing diuretics such as Spironolactone, and Thiazides like Hydrochloro-thiazide.

Adverse Effects of Diuretics

• Includes hypotension, hypokalemia, dizziness, headaches, dehydration, and muscle cramps.

Body Fluid Compartments

• Total body water is composed of intracellular (67%), interstitial (25%), and plasma volume (8%).
• Water makes up 60% of the adult human body.

Fluid Types - Crystalloids

• Crystalloids are solutions containing fluids and electrolytes that are normally found in the body, examples include NaCl, Lactated Ringers, D5W.
• Crystalloids are used for maintenance fluids.
• Crystalloids might cause edema, particularly in the periphery or pulmonary regions which can dilute plasma proteins, subsequently lowering colloid oncotic pressure.
• Crystalloids are used for AKI, Burns, Hyponatremia, Sepsis (SOCK).

Fluid Types - Colloids

• Colloids contain protein substances.
• Increase colloid oncotic pressure and mobilize fluid from interstitial to plasma compartment when plasma protein levels are low.
• Common Colloids - Albumin (5% and 25% from human donors), Dextran (40 or 70 in sodium chloride and 5% dextrose), and Hetastarch (synthetic).

Colloids Adverse Effects

• Usually safe, but may cause altered coagulation, potentially leading to bleeding.
• Has no clotting factors or oxygen-carrying capacity
• Dextran therapy rarely causes anaphylaxis or kidney failure.

Colloids: Albumin Details

• Albumin is a protein normally produced by the liver.
• Albumin generates approximately 70% of colloid oncotic pressure
• It is a sterile solution from pooled blood, plasma, serum, or placentas from healthy human donors following a pasteurization process to destroy possible contaminants.

Blood products

• Blood products are the only fluids able to carry oxygen
• Used to increase tissue oxygenation and plasma volume.
• The most expensive and least available fluid because they require human donors

IV Fluid Types

• Isotonic solutions, hypertonic solutions and hypotonic Solutions

Electrolye Imbalances

• Sodium (135-145 MEQ/L). Hyper and hypo.

• Potassium Imbalance (3.5-5.0 MEQ/L). Hyper and hypo

• Calcium Imbalance (4-5 MEQ/L). Hyper and Hypo

Sodium Therapy

• Main indication is sodium depletion when dietary measures cannot prevent.

• Mild sodium depletion is treated via oral sodium chloride or fluid restriction.

• In severe depletions use IV NS or lactated Ringer’s solution.

• Oral administration can cause Nausea, vomiting, cramps.

• IV administration can cause venous phlebitis

Potassium Therapy

• Main indication is the treatment or prevention of potassium depletion when dietary restriction is inadaquate

• Used to stop irregular heartbeats.

• Used to manage tachydysrhythmias that can occur after cardiac surgery

Potassium Adverse Effects

• Oral preparations can cause diarrhea, nausea, vomiting, gastrointestinal bleeding, ulceration

• IV administration can cause Pain at injection site and Phlebitis

• Excessive administration can cause Hyperkalemia, Toxic effects and Cardiac arrest-

Nursing Implications for Potassium

• Parenteral infusions of potassium must be monitored closely.

• IV potassium must not be given at a rate faster than 10 mmol/hr to patients who are not on cardiac monitors. For critically ill patients on cardiac monitors, rates of 20 mmol/hr may be used.

• Never give as an IV bolus or undiluted

• Must be diluted in either water or fruit juice (100 to 250 mL) and taken with food or immediately after meals to minimize gastrointestinal distress or irritation and to prevent too rapid absorption

• Monitor reports of nausea, vomiting, gastrointestinal pain, and gastrointestinal bleeding.

Nursing Implications

• Develop a list of nursing implications for the following classifications of antihypertensives
• Adrenergic drugs, Angiotensin-converting enzyme (ACE) inhibitors, Angiotensin II receptor blockers (ARBs), Calcium channel blockers, Diuretics