Comprehensive Study Guide for Adrenergic Drugs, Shock, and Electrolyte Therapy

Overview of the Autonomic Nervous System

• The autonomic nervous system is defined as part of the vertical nervous system.

• Function: It is responsible for automatically regulating essential body functions including heart rate, pupil size, and breathing. These are actions the individual does not have to consciously initiate.

• Major Branches:

  • Sympathetic: Responsible for the "fight, flight, or freeze" response. This branch takes over during danger, medical emergencies, or perceived threats (e.g., an attacking dog).

  • Parasympathetic: Known as the "rest and digest" system.

• Primary Mechanism: The sympathetic nervous system directs blood flow to parts of the body required for rapid reaction.

Adrenergic Drugs and Receptor Mechanisms

• Adrenergic drugs are medications that function similarly to epinephrine (EPI) or adrenaline.

• Terminology:

  • Sympathomimetic drugs: Drugs that mimic the sympathetic nervous system.

  • Adrenergic system: Synonymous with the sympathetic branch.

  • Sympatholydex: Refers to adrenergic blockers.

• Primary Neurotransmitter: Norepinephrine is the primary neurotransmitter, which serves as a precursor to epinephrine.

• Receptor Types and Functions:

  • Alpha-1 ($\alpha_1$): Primarily located in peripheral blood vessels; stimulation causes vasoconstriction (described as "squeezing the vessels").

  • Alpha-2 ($\alpha_2$): Located in presynaptic neurons; regulates neurotransmitter release, decreases GI tone, decreases GI motility, and decreases GI secretions.

  • Beta-1 ($\beta_1$): Primarily located in the heart. Memory tip: "You've got one heart." Stimulation increases heart rate and the force of contraction.

  • Beta-2 ($\beta_2$): Located in the lungs and peripheral blood vessels. Memory tip: "You've got two lungs." Stimulation causes bronchodilation and vasodilation.

Physiological Effects of Adrenergic Drugs

• Central Nervous System (CNS) Effects: Increased wakefulness, faster reaction times, and increased reflexes.

• Cardiovascular Effects: Increased heart rate, increased cardiac output, vasoconstriction of many blood vessels, and increased blood pressure.

• Respiratory Effects: Bronchodilation leading to easier breathing.

• Gastrointestinal Effects: Slowed motility and decreased GI secretions (the body does not need to use the bathroom while outrunning danger).

• Metabolic Effects: Increased glucose availability and the release of fatty acids for energy. This allows for extreme physical feats, such as a mother lifting a car to save a child under severe stress.

• General Overview of Effects: Increased alertness, dilated pupils, and bronchodilation.

Respiratory Medications: Beta-Two Agonists

• Short-Acting Beta-Two Agonists (SABA):

  • Mechanism of Action: Relaxation of bronchial smooth muscle and bronchodilation.

  • Uses: Rapid relief of bronchospasms and respiratory distress (e.g., used by respiratory therapists for COPD patients).

  • Adverse Effects: Tachycardia, nervousness, headaches, and nausea.

• Clinical Conflict:

  • Patients often have an increased heart rate (e.g., $120\,\text{bpm}$) due to the panic of being unable to breathe.

  • If a Beta-2 agonist is given when the heart rate is already high, it may "shoot up" further.

  • Alternatives include calling a provider to change the drug to one with less cardiac effect or decreasing the dosage strength while increasing frequency.

• Long-Acting Beta-Two Agonists (LABA):

  • Mechanism: Stimulate Beta-2 receptors for prolonged bronchodilation.

  • Uses: Long-term management of respiratory disorders.

  • Forms: Often used alongside a separate rescue inhaler for home management.

  • Adverse Effects: Tachycardia, headache, nervousness, and hypertension.

• Nursing Considerations:

  • Monitor respiratory status, heart rate, and blood pressure.

  • Perform morning assessments and reassess after treatment. Improvement should see stabilized respiratory status and a lower heart rate as the patient's panic subsides.

Management of Shock and Adrenergic Vasopressors

• Shock Definition: A state resulting in inadequate tissue perfusion, hypotension, and decreased oxygen delivery.

• Adrenergic Drugs Used in Shock:

  • Epinephrine

  • Norepinephrine

  • Dopamine

  • Dobutamine

  • Midodrine (specifically used for patients who are consistently hypotensive; never given after dinner to prevent them from "bottoming out" overnight).

  • Isoproterenol

• Types of Shock:

  • Septic Shock: Overwhelming infection (e.g., UTI, pneumonia, wound infection) affecting multiple organs. Part of distributive shock.

  • Hypovolemic Shock: Caused by loss of circulating volume due to hemorrhage, burns, dehydration, or excessive diuresis (e.g., from Lasix/furosemide overuse).

  • Cardiogenic/Obstructive Shock: The heart cannot pump effectively (e.g., MI, CHF, cardiomyopathy, ventricular arrhythmias).

  • Distributive Shock: Involves abnormal vasodilation; includes Septic, Anaphylactic (severe allergic reaction), and Neurogenic (neurological issues/autonomic involvement) shock.

• Adverse Effects of Shock Treatment: Cardiac arrhythmias (tachycardia or bradycardia), headache, nausea, vomiting, and severe hypertension.

Nursing Considerations for Vasopressor Administration

• Monitoring Requirements: Continuously monitor BP (as frequently as every $3$ to $15$ minutes in ICU/step-down units), heart rate, arrhythmias, respiratory status, and urine output ($I\&O$).

• IV Administration: Must be administered via infusion pumps. Standard practice involves maintaining at least two functional IV lines (sometimes up to four).

• Extravasation and Infiltration Risk:

  • Drugs like dopamine are extremely destructive and can cause severe tissue death (necrosis), potentially leading to limb loss.

  • Immediate Action: Stop the infusion and establish a new IV line immediately. Notify the provider regarding possible tissue damage and the duration the patient was without medication.

• Drug Contraindications:

  • Isoproterenol: Patients with tachyarrhythmias or heart block caused by DIT toxicity.

  • Dopamine: Patients with adrenal gland tumors (pheochromocytoma) or uncontrolled arrhythmias/ventricular fibrillation.

  • Epinephrine: Clients with narrow-angle glaucoma; should not be used as a local anesthetic on fingers and toes.

  • Norepinephrine: Patients hypotensive from blood volume deficit.

• Interactions:

  • Antidepressants: Increase the sympathomimetic effect.

  • Oxytocin: Increases the risk of hypertension.

  • Dopamine + Phenytoin: Increased risk of seizures, hypotension, and bradycardia.

  • Dobutamine + Beta Blockers: Can cause increased hypertension.

Fluid and Electrolyte Fundamentals

• The human body is approximately $70\%$ fluid by molecular weight. Fluids transport oxygen, nutrients, medications, and waste.

• Electrolytes: Electrically charged particles (sodium, potassium, magnesium, calcium) essential for cellular function, neuromuscular activity, cardiac function, and acid-base balance.

• Causes of Imbalance: Vomiting, diarrhea (stomach bug), surgery, burns, trauma, kidney disease, dialysis, and medications (especially diuretics).

• IV Therapy Responsibilities: Monitor lab values, $I\&O$, vital signs, IV sites, and cardiac rhythms.

• Cardiac Monitoring: Vital for any patient with electrolyte imbalances or a history of arrhythmias, as even narrow deviations in levels (e.g., magnesium) can trigger issues.

Intracellular Electrolytes: Potassium ($K^+$)

• Form: Potassium chloride or potassium gluconate. It cannot be stored by the body.

• Normal Range: $3.5$ to $5.0\,mEq/L$.

• Function: Nerve pulse transmission, skeletal and smooth muscle contraction, and cardiac muscle contraction.

• Hypokalemia (Low K): Muscle weakness, fatigue, leg cramps, decreased reflexes, paralytic ileus (always replace GI residuals from NG tubes to avoid loss), and irregular pulse.

• Hyperkalemia (High K): Weakness, paresthesia, hypotension, arrhythmias, and potential cardiac arrest.

• Drug Interactions:

  • ACE inhibitors and Potassium-sparing diuretics (e.g., spironolactone): Can lead to hyperkalemia.

  • Salt substitutes: Can lead to hyperkalemia.

  • Digoxin: Can lead to toxicity.

• Administration Rules:

  • NEVER IV PUSH: Potassium is used in lethal injections on death row. Administering it as an IV push will cause immediate cardiac arrest.

  • Infusion: Given as a slow drip (e.g., $25\,ml/hr$). It often burns; provider may allow dilution with normal saline.

  • Oral: Take with or after meals with a full glass ($8\,oz$) of water to avoid GI distress. Do not crush or chew tablets. Effervescent tablets must stop fizzing before consumption.

Intracellular Electrolytes: Magnesium ($Mg^{2+}$)

• Form: Magnesium sulfate. Supports nerve pulse transmission and carb metabolism.

• Normal Range: $1.5$ to $2.5\,mEq/L$.

• Uses: Treatment of hypomagnesemia, prevention of seizures in preeclampsia/eclampsia, and TPN supplementation.

• Hypomagnesemia (Excited Nervous System): Tremors, hyperactive reflexes, leg cramps, tachycardia, hypertension, and seizures.

• Hypermagnesemia (Slowed System): Lethargy, drowsiness, hypotension, respiratory depression, and decreased reflexes.

• Nursing Considerations: Assess deep tendon reflexes (DTRs) periodically. Monitor urine output; must be at least $100\,ml$ every $4$ hours.

• Antidote for Toxicity: IV Calcium.

• Interactions:

  • CNS depressants: Increased depression.

  • Neuromuscular blockers: Respiratory depression.

  • Digoxin: Risk of heart block.

Extracellular Electrolytes: Sodium ($Na^+$)

• Common IV Solutions:

  • Normal Saline: $0.9\%$ sodium chloride.

  • Half Normal Saline: $0.45\%$ sodium chloride.

  • D5NS: $5\%$ dextrose and $0.9\%$ normal saline.

  • D5 1/2 NS: $5\%$ dextrose and $0.45\%$ normal saline.

• Normal Range: $132$ to $145\,mEq/L$.

• Hyponatremia: Confusion, irritability, headache, seizures, hypotension, tachycardia.

• Hypernatremia: Thirst (body wants to dilute salt), dry mucous membranes, restlessness, edema, and weight gain ("waterfall of salt").

• Nursing Considerations: Assess for pulmonary edema (cough, crackles in lungs), especially when giving hypertonic solutions. Cardiac patients are kept on low-salt diets to prevent fluid retention.

• Saline Flush: Essential nursing task. Flush before and after every medication to prevent drugs from touching. Standard pocket stock is $15$ saline flushes.

Extracellular Electrolytes: Calcium ($Ca^{2+}$)

• Form: Calcium carbonate, calcium gluconate.

• Normal Range: $4.5$ to $5.3\,mEq/L$ (or $9$ to $11\,mg/dL$).

• Significance of Parathyroid: Controls calcium. Thyroidectomy patients must stay overnight for lab monitoring because accidental damage to parathyroids can cause calcium to "tank."

• Hypocalcemia: Muscle cramps, tetany, hyperactive reflexes, polyneurotristot sign, Chstec sign, and seizures.

• Hypercalcemia: Lethargy, weakness, constipation, polyuria, bone pain, and cardiac arrest.

• Nursing Considerations: Rapid IV administration can cause bradycardia and arrhythmias. Always use a heart monitor during supplementation.

Combined Solutions and Blood Products

• Combined Solutions: Lactated Ringer's, Plasma-Lyte, and dextrose solutions. Used for hydration, electrolyte replacement, and providing calories (if NPO).

• Plasma: Hard to obtain due to short shelf life; used for massive hemorrhage, burns, and shock. Note: Does not require typing or cross-matching.

• Albumin: A protein colloid that maintains plasma volume and colloid osmotic pressure by pulling fluid into the vascular space. Primary nursing check: Listen for crackles (fluid overload).

• Plasma Expanders: Examples include Ketostarch and Dextran. Used in trauma and shock; requires close monitoring for allergic reactions.

Total Parenteral Nutrition (TPN) and Fat Emulsions

• TPN: Contains dextrose, amino acids, fat emulsions, electrolytes, vitamins, and minerals. Administered via central line when the GI tract is inadequate (e.g., bowel perforations, ruptured stomach).

• Fat Emulsions: Replaces essential fatty acids. Looks like a smaller separate bag, not run all day.

  • Contraindications: Egg allergy and acute pancreatitis.

  • Nursing: Monitor the first $30$ minutes for hypersensitivity and breathing difficulties.

• TPN Risks: Hyperglycemia and hypoglycemia (if stopped abruptly).

• Nursing Considerations: Never stop TPN abruptly. Monitor glucose every $4$ to $6$ hours and check the central line site for infection.

Acid-Base Management and Electrolyte Summary

• Sodium Bicarbonate: Used to treat metabolic acidosis by raising pH. Can cause nausea, vomiting, and metabolic alkalosis. Do not give within $2$ hours of incompatible medications.

• Ammonium Chloride: Used to treat metabolic alkalosis by lowering pH. Can cause potassium loss and metabolic acidosis.

• Final Summary of Ranges and Rules:

  • Potassium: $3.5$ to $5.0\,mEq/L$ (Never push).

  • Magnesium: $1.5$ to $2.5\,mEq/L$ (Antidote: Calcium).

  • Sodium: $132$ to $145\,mEq/L$.

  • Calcium: $4.5$ to $5.3\,mEq/L$ (Monitor for cardiac arrest if high).

  • Hypertonic saline risk: Pulmonary edema/crackles.

  • Fat Emulsions: Contraindicated in egg allergies and pancreatitis.

  • TPN: Monitor glucose every $4$ to $6$ hours.