1. Bezold-Jarisch Reflex

Definition

Receptor & Pathway

• Afferent: Unmyelinated vagal C fibers (type C, juxtacapillary/chemosensitive) from left ventricular wall, atria, great veins, and pulmonary artery
• Efferent: Increased parasympathetic (vagal) tone
• The reflex arc runs through the medullary cardiovascular center

Triggers / Stimuli

Clinical Significance

1. Vasovagal syncope (VVS) - The classic faint. Originally described as the cardiorespiratory response to IV injection of Veratrum alkaloids. During prolonged standing, blood pools in the lower extremities, reducing intracardiac volume. The left ventricle responds paradoxically - baroreceptors in the ventricular wall trigger sudden bradycardia and hypotension instead of the expected compensatory tachycardia, causing syncope. (Medical Physiology, p. 801)
2. Inferior wall MI - The BJ reflex is commonly activated during inferior (posterior) MI because the inferior LV wall is rich in vagal receptor endings. This explains the bradycardia and hypotension seen with inferior STEMI.
3. Anaphylaxis - Bradycardia in anaphylaxis (rather than expected tachycardia) can occur due to BJ reflex activation. (Washington Manual of Medical Therapeutics)
4. Thrombolysis/revascularization - Reperfusion after MI can trigger the BJ reflex, causing post-thrombolysis hypotension and bradycardia.
5. Cardioprotective role - Because it induces bradycardia (reducing cardiac oxygen demand) and coronary dilatation, it is considered a protective reflex. This may be modulated by ANP/BNP (natriuretic peptides); thus the reflex may be blunted in cardiac hypertrophy or atrial fibrillation.

Vasovagal Syncope Mechanism (BJ pathway)

1. Prolonged standing → blood pools in legs → decreased ventricular filling
2. Paradoxically, low-volume, vigorously contracting LV stimulates mechanoreceptors
3. Vagal C-fiber afferents → medulla
4. Massive parasympathetic output + withdrawal of sympathetic tone
5. Bradycardia + vasodilation → hypotension → global cerebral ischemia → loss of consciousness (if ~10 seconds)

• (Ganong's Review of Medical Physiology, 26e, p. 593)
• (Miller's Anesthesia, 10e, p. 1432)

2. Bainbridge Reflex

Definition

Receptor & Pathway

• Receptors: Stretch receptors (low-pressure B fibers) in the right atrial wall and cavoatrial junction
• Afferent: Vagal afferent fibers → medullary cardiovascular center
• Efferent: Inhibition of parasympathetic tone + sympathetic stimulation → increased heart rate via SA node
• Direct mechanical stretch of the SA node also contributes

Key Features

• The increase in heart rate is greatest at low baseline heart rates (the reflex saturates at high rates)
• Acts only on heart rate - effects on contractility and stroke volume are insignificant
• Serves as a counterbalance to the baroreceptor reflex: when circulating volume rises, Bainbridge reflex raises HR; when volume falls, baroreceptor reflex raises HR - so both volume loading AND volume depletion raise heart rate, with minimum HR at normal volume
• (Medical Physiology, p. 801)
• (Miller's Anesthesia, 10e, p. 1432)

Quick Comparison

Antibiotic (Antimicrobial) Stewardship

Definition & Goal

• Improve patient outcomes
• Minimize adverse drug effects (including C. difficile infection)
• Slow the emergence and spread of antimicrobial resistance
• Reduce unnecessary healthcare costs

Why It Matters: The Problem

• Time pressure in outpatient settings
• Fear of missing a rare bacterial diagnosis
• Concern about rare bacterial complications
• Mistaken belief that patients expect antibiotics
• Lack of salience of antibiotic adverse effects (Harrison's 22e)

CDC 7 Core Elements of Hospital Antimicrobial Stewardship Programs (ASP)

• (Tietz Textbook of Laboratory Medicine, 7e; Red Book 2021)

Key ASP Interventions (The "Action" Element)

Inpatient Strategies

Outpatient Strategies (CDC "Core Elements of Outpatient Stewardship")

1. Commitment - Clinician and practice-level commitment to appropriate prescribing
2. Action for policy and practice - At least one concrete policy or practice change
3. Tracking and reporting - Prescribing audits and peer comparison feedback
4. Education and expertise - Clinician + patient education

• Peer comparison (audit + feedback showing individual prescribing vs. peers)
• Accountable justification (require written rationale for antibiotic prescriptions)
• Precommitment strategies
• Communication skills training - making a clear diagnosis, focusing on symptom relief, explaining expected illness course, identifying red flags
• Patient education materials
• Telemedicine - can reduce inappropriate prescribing in virtual visits (Harrison's 22e)

The ASP Team (Multidisciplinary)

• Infectious disease physician (program leader)
• Clinical pharmacist with ID expertise (co-leader)
• Clinical microbiologist
• Hospital epidemiologist / infection preventionist
• Information systems / IT specialists
• Nurses (frontline educators)

Metrics Tracked by ASPs

The Lab's Role in Stewardship

• Annual cumulative antibiogram - facility-specific and unit-specific (e.g., ICU) susceptibility data guides empiric therapy choices
• Rapid diagnostics (PCR-based blood culture ID panels, MALDI-TOF) - faster organism identification allows faster de-escalation
• Rapid susceptibility testing - reduces time on inappropriate empiric therapy
• Bug-drug mismatch alerts - automated IT flags when prescribed antibiotic does not match susceptibility
• Postanalytical reporting - critical result communication, antimicrobial susceptibility interpretation (Tietz Lab Medicine, 7e)

Outpatient "Choosing Wisely" (AAP / PIDS) - Key Don'ts

1. Don't start empiric antibiotics for suspected bacterial infection without first obtaining cultures
2. Don't use broad-spectrum agents for perioperative prophylaxis or continue prophylaxis after wound closure
3. Don't treat uncomplicated CAP in healthy, immunized hospitalized patients with anything broader than ampicillin
4. Don't use vancomycin or carbapenems empirically in NICU unless specific resistance risk exists
5. Don't use PICC lines / prolonged IV antibiotics in otherwise healthy children who can transition to oral therapy (Red Book 2021, AAP)

CDC National Action Plan: 4 Pillars

1. Prevent infections - vaccines, infection control, food safety, hand hygiene
2. Track resistance - CDC AR Lab Network, surveillance data
3. Improve antimicrobial use - stewardship across all care settings (including veterinary/agricultural)
4. Develop new drugs and diagnostics - pipeline for novel mechanisms, rapid diagnostics (Red Book 2021)

Recent Evidence (PubMed, 2023-2026)

• AI-driven approaches - machine learning for antibiotic prescription optimization (PMID 39955846)
• Dental stewardship - a systematic review of interventions in dental settings (PMID 39400429), recognizing dentistry as a significant source of antibiotic overprescribing
• Penicillin allergy de-labeling - systematic review confirms high proportion of labeled penicillin-allergic patients can tolerate penicillins on testing (PMID 40738396); de-labeling is a stewardship strategy that expands use of narrow-spectrum agents

Remimazolam (Brand: BYFAVO)

Overview

• Pharmacodynamics of midazolam (GABA-A receptor agonist - sedation, anxiolysis, amnesia)
• Metabolic kinetics of remifentanil (ester hydrolysis by tissue esterases - organ-independent, no accumulation)

Chemical Structure & Mechanism

Pharmacokinetics

• (Miller's Anesthesia 10e, p. 2519-2520)

Pharmacodynamics & Effects by System

CNS

• Dose-dependent sedation → anxiolysis at low doses, deep sedation/hypnosis at higher doses
• Anterograde amnesia (like all benzodiazepines)
• Faster neuropsychiatric recovery vs. midazolam
• No anticonvulsant data yet established clinically

Cardiovascular

• Hemodynamically stable - minimal effect on heart rate, ECG, and blood pressure
• Similar cardiovascular profile to midazolam
• Less hypotension and vasopressor requirement compared to propofol - key advantage in high-risk patients
• Preservation of homeostatic reflexes

Respiratory

• Similar or fewer desaturation events and respiratory depression compared to midazolam
• Less respiratory depression than propofol in procedural sedation
• Caution when combined with opioids (fentanyl co-administration increases adverse drug reactions)
• (Miller's Anesthesia 10e; Barash Clinical Anesthesia 9e)

FDA Approval & Regulatory Status

• Trade name: BYFAVO (remimazolam besylate)
• Formulation: 20 mg lyophilized powder per 12 mL vial (2.5 mg/mL after reconstitution), IV only
• DEA Schedule: CIV (Schedule IV controlled substance)

Dosing

Procedural Sedation (FDA-Approved - Adults)

General Anesthesia (Off-label / Investigational)

• Infusion rates of 1-5 mg/min for maintenance
• Repeated boluses of 1.25-2.5 mg every 2 min
• (Goodman & Gilman; VA BYFAVO Monograph 2024)

Reversal

• Reversal time: ~1 minute with flumazenil vs. ~10.5 minutes with placebo
• No resedation reported after reversal
• Reversal is rarely needed in practice due to the drug's inherently short action
• This reversibility is a significant safety advantage, especially in high-risk patients (Miller's Anesthesia 10e)

Clinical Applications

Comparison with Key Agents

Advantages (Summary)

1. Organ-independent metabolism - safe in renal and hepatic impairment
2. No drug accumulation - predictable offset even after prolonged infusion
3. Flumazenil reversibility - unique safety net among sedative infusions
4. Hemodynamic stability - less hypotension than propofol
5. Less respiratory depression vs. propofol; fewer desaturations vs. midazolam
6. No injection pain (unlike propofol)
7. No propofol infusion syndrome (PRIS) risk
8. Faster, cleaner recovery vs. midazolam
9. Effective across high-risk populations (ASA III/IV, liver cirrhosis)

Cautions & Limitations

• Concurrent opioids: Fentanyl co-administration increases adverse drug reactions - use with caution
• Severe hepatic impairment: May increase sedative effect; dose reduction prudent
• Current FDA label: Procedures ≤30 minutes only (EU label has no duration cap)
• Pediatric use: Currently off-label (studies underway)
• Drug incompatibilities: Incompatible with several common perioperative medications (check compatibility before co-infusion)
• Not for inhalational or oral administration

Recent Evidence (2022-2025)

• A systematic review and meta-analysis (PMID 36326772) confirmed remimazolam vs. propofol for procedural sedation: comparable efficacy, less hypotension with remimazolam
• A 2024 comprehensive review (PMID 39132624) covers its expanding use in general anesthesia
• A 2025 clinical pharmacokinetics/pharmacodynamics review (PMID 40690147) provides updated PK/PD modeling data
• A 2025 WFSA tutorial highlights emerging uses in ICU and critical care sedation