Advanced Medical Management for Anesthesia and Sedation

Management of Hypertension and Pharmacotherapy

• Stages of Hypertension Management

  • Stage One management primarily focuses on lifestyle modifications, including diet, exercise, and certain over-the-counter supplements.
  • Stage Two Hypertension is defined as a blood pressure of $140\,mmHg$ or higher. At this stage, medications are introduced to control the condition.

• Pharmacological Interventions

  • Beta Blockers: These are considered the first line of drugs for hypertension management.
    • Selective Beta Blockers: Example provided is Metoprolol (referred to as "toperol").
    • Nonselective Beta Blockers: Example provided is Propranolol.
  • Diuretics: These often follow beta blockers in the treatment regimen. A specific example is Lasix.
  • Calcium Channel Blockers (CCBs): Common examples include Norvasc or Amlodipine.
  • Sympatholytics and Vasodilators: Examples include Clonidine and Nitroglycerin. These function by decreasing venous return to the heart.
  • Polypharmacy: Many patients require a combination of two or more of these medications to achieve adequate blood pressure control.

• Preoperative Considerations for Hypertensive Patients

  • A thorough evaluation of the patient's medical history is critical.
  • Review all antihypertensive medications.
  • Generally, patients should take their antihypertensive medications the morning of their appointment with a few ounces of clear water, even if they are required to be NPO (nothing by mouth) after midnight.

• Pathophysiology of Chronic Uncontrolled Hypertension

  • Triggers atherosclerotic changes, leading to stenosis and thrombosis.
  • Pressure overload of the heart can lead to renal failure because the kidneys are highly sensitive to changes in the mean arterial blood pressure ($MAP$).
  • The retina and the brain are also highly sensitive to these pressure changes.

• Clinical Guidelines for Elective Procedures

  • Multiple studies, including a notable study in JAMA (2002), indicate that elective cases can be performed safely as long as the patient's blood pressure does not exceed $180/110\,mmHg$.
  • If a patient's history confirms they do not have diabetes, heart disease, or coronary artery disease ($CAD$), treatment may proceed even if blood pressure is slightly higher than $180/110\,mmHg$.
  • Crucial Limitation: Many patients are poor historians or have not sought medical care in $10$ to $15$ years, making it difficult to rule out underlying comorbidities.
  • Mandatory Cancellation: Once blood pressure reaches $210/120\,mmHg$, regardless of whether the patient is symptomatic or asymptomatic, the procedure must be canceled, and the patient referred for immediate treatment.

• Hypertensive Urgency vs. Crisis

  • The term "hypertensive crisis" is often viewed as alarming and suboptimal terminology.
  • Hypertensive Urgency: High blood pressure without symptoms. It rarely requires immediate treatment.
  • Hypertensive Emergency (Symptomatic): If the patient presents with symptoms such as chest pain, headache, or altered mental status, EMS transport and support are warranted.

Obesity, Body Mass Index (BMI), and Respiratory Risks

• BMI Classifications

  • Overweight: BMI greater than $25$.
  • Obese: BMI greater than $30$.
  • Morbidly Obese: BMI greater than $35$.

• Epidemiology and Comorbidities

  • $20\%$ of Americans have a BMI greater than $30$.
  • $10\%$ of obese patients suffer from Obstructive Sleep Apnea ($OSA$).
  • Obesity acts as a catalyst for other serious systemic conditions, including hypertension, myocardial ischemia, ventricular hypertrophy, congestive heart failure ($CHF$), diabetes, coronary artery disease ($CAD$), and $OSA$.

• Anesthetic Challenges in Obese Patients

  • Most obese patients have a poor airway when sedated.
  • Typical airway maneuvers may be insufficient to relieve obstructions.
  • Challenges include difficulty with mask ventilation and intubation.
  • Metabolic Demand: They have a higher oxygen requirement and a higher metabolic demand because they have more tissue to perfuse. Consequently, they desaturate very quickly during periods of apnea.
  • Obesity is characterized as a restrictive lung disease.

• Screening and Diagnosis

  • The "STOP-BANG" acronym is used to screen for $OSA$ risk.
  • Multiple positive findings indicate a high risk (though not a definitive diagnosis).
  • Multiple positive findings should prompt a referral for a sleep study to determine the type and severity of $OSA$.

Geriatric Patient Considerations

• Physiological Changes in the Elderly (Aged 65 and Older)

  • Autonomic changes typically begin to occur around age $65$.
  • Cardiac Changes: Prone to arrhythmias due to decreased conduction from the SA node. Dampened baroreceptor reflexes lead to orthostatic hypotension, which increases the risk of syncope or falls.
  • Epinephrine Sensitivity: Geriatric patients show increased sensitivity to epinephrine; injections should be administered slowly.
  • Liver Function: The liver shrinks and blood flow is reduced, decreasing overall drug metabolism.
  • Albumin Production: A decrease in albumin production leads to an increase in the concentration of active (unbound) drugs within the plasma.
  • Respiratory Changes: Lungs become stiffer and less compliant. Functional residual capacity ($FRC$) decreases. Chest wall and diaphragm strength are reduced. This leads to an increased incidence of hypoventilation and apnea.

• Sedation and Anesthesia Management

  • Postoperative Complications: The most common complications are confusion, forgetfulness, and delirium. Caregivers should be informed that the patient may need support for $2$ to $3$ days post-surgery.
  • Dosing Rules: Due to metabolic and plasma changes, initial drug doses should often be adjusted by almost half.
  • Narcotics: High sensitivity to narcotics. Guidelines: "Start slow and go slow" and "Less is more."
  • Drug Choice: Preferences should be given to agents with shorter half-lives and reversible agents. Keep appointment times short.
  • Assume some level of cardiovascular disease exists. Baseline tests like a $12$-lead EKG, Complete Blood Count ($CBC$), and Basic Metabolic Panel ($BMP$) are helpful to unmask underlying issues.

• Specific Drug Concerns in Geriatrics

  • Benadryl: Its anticholinergic properties can prevent the bladder from contracting and slow urine flow, creating problems for patients with Benign Prostate Hypertrophy ($BPH$).
  • Meperidine (Demerol): The molecular structure is similar to Atropine; it causes an increase in heart rate, which is non-ideal for elderly patients.

Psychiatric Medications and Drug Interactions

• Selective Serotonin Reuptake Inhibitors (SSRIs)

  • The most commonly prescribed psychiatric medications.
  • Patients should continue taking SSRIs (and Tricyclic Antidepressants) on their regular schedule prior to procedures.
  • CYP2D6 Inhibition: SSRIs inhibit the hepatic enzyme family $CYP2D6$.
  • Codeine/Hydrocodone Metabolism: Codeine is a prodrug that requires demethylation by $CYP2D6$ to be transformed into its active form, morphine. Without this removal of the methyl group, it has no analgesic effect. Hydrocodone follows a similar process.
  • Genetic Variation: Approximately $10\%$ of Caucasians lack the $CYP2D6$ enzyme and will not receive pain relief from codeine or hydrocodone. Oxycodone should be prescribed instead, as it is not affected by the $CYP2D6$ family.
  • Benzodiazepines: SSRIs cause a delay in the clearance of benzodiazepines, though this is usually not clinically significant.

• Lithium

  • Lithium has a low therapeutic index, meaning there is a narrow margin between a therapeutic dose and a toxic dose.
  • NSAID Interaction: Do not prescribe NSAIDs to patients on Lithium. NSAIDs enhance the renal absorption of Lithium, leading to toxic levels that can cause hallucinations and seizures.

Thyroid Disorders

• Physiology of the Thyroid

  • Regulated by the hypothalamic-pituitary-thyroid axis.
  • Produces Thyroxine and Calcitonin.
  • Regulates metabolic rate, growth, body temperature, and heart rate.
  • Thyroid disease is more common in females than males.

• Hypothyroidism

  • The most common thyroid disorder.
  • Symptoms: Loss of energy, intolerance to cold, and drowsiness.
  • Treatment: Supplementation with Synthroid. Patients typically become euthyroid within a couple of weeks of starting treatment.
  • Anesthetic Consideration: Hypothyroid patients can be very sensitive to CNS depressants like benzodiazepines.

• Hyperthyroidism

  • Associated with a hyperactive metabolic state.
  • Symptoms: Weight loss, intolerance to warmth, heart palpitations, nervousness, and irritability.
  • Hallmark sign: Exophthalmos (bulging eyes).
  • Anesthetic Consideration: Requires a medical consult before dental care. Hyperthyroidism causes an upregulation of beta receptors in the heart, leading to an exaggerated response to epinephrine. Use epi with caution.

Diabetes Mellitus Management

• Classification

  • Type 1: Autoimmune destruction of pancreatic beta cells. Requires exogenous insulin administration.
  • Type 2: Patients produce some insulin but are insensitive to its effects (insulin resistance).
  • Commonality: Both lead to uncontrolled high blood glucose, causing end-organ damage, neuropathies, vasculopathies, $CAD$, and renal failure.

• Monitoring and Diagnostics

  • Hemoglobin A1c ($HbA1c$): Reflects average glucose levels over a $90$-day period. The ADA target is $≤ 7$.
  • Fasting Blood Glucose: A value greater than $100\,mg/dL$ is now considered pre-diabetic.

• Diabetes Medications

  • Oral/Non-insulin meds for Type 2:
    • Glucose synthesis inhibitors: Metformin, Actos, Avandia.
    • Insulin release promoters (hypoglycemic agents): Glimepiride, Glyburide, Glipizide.
  • Insulin Preparations:
    • Standard concentration: $100\,units/mL$.
    • Concentrated Regular Insulin ($U-500$): $500\,units/mL$.
  • Insulin Pumps: Utilize subcutaneous glucose sensors to infuse insulin based on a pre-programmed sliding scale. Primarily used for Type 1 diabetics needing tight control. Consult the endocrinologist; usually, pump settings do not require modification for sedation.

• Perioperative Protocols

  • General Rule: If the patient is not NPO, no modifications are needed. If NPO, consult a physician.
  • Morning of Appointment: Usually omit oral pills.
  • Night Before Appointment: Usually reduce the long-acting insulin dose depending on wake-up glucose levels.
  • Surgical Impact: Anticipate a mild increase in blood glucose due to surgical stimulation and epinephrine injections.
  • Steroids: Steroids increase blood glucose. An antiemetic dose of Decadron increases glucose by roughly $20\,mg/dL$. Use cautiously.
  • Post-op: Reintroduce diabetic meds only after food and fluid intake are near normal. Prevent and treat postoperative nausea and vomiting ($PONV$) aggressively to ensure intake returns to normal quickly.
  • Drug Interactions: Aside from steroidal dose packs, there are no significant interactions between diabetic medications and antibiotics, sedatives, or NSAIDs.