# Clinical Cases: Autonomic Pharmacology

## Case 1: Organophosphate Poisoning (Cholinergic Toxidrome)

### Clinical Scenario
A 42-year-old male farm worker is brought to the emergency department after collapsing in a field where he was spraying pesticides.

### Patient Demographics
- **Age:** 42 years
- **Sex:** Male
- **Weight:** 75 kg

### Chief Complaint
Found unresponsive with excessive secretions and difficulty breathing

### History of Present Illness
The patient was spraying organophosphate insecticides without proper protective equipment when he developed progressive weakness, blurred vision, and abdominal cramping. Coworkers found him collapsed with profuse salivation, labored breathing, and urinary incontinence approximately 30 minutes later. EMS noted pinpoint pupils and wheezing on arrival.

### Physical Examination
- **Vital Signs:** BP 90/60 mmHg, HR 48 bpm, RR 28 (labored), T 36.2C, SpO2 82% on room air
- **General:** Obtunded, copious oral secretions, incontinent of urine
- **HEENT:** Miosis (1 mm pupils bilaterally), profuse lacrimation and salivation
- **Respiratory:** Diffuse wheezes and rhonchi, bronchorrhea
- **Cardiovascular:** Bradycardic, regular
- **Abdominal:** Hyperactive bowel sounds, involuntary defecation
- **Neurological:** Obtunded, fasciculations visible in all extremities
- **Skin:** Profuse diaphoresis

### Workup and Results
| Test | Result | Reference Range |
|------|--------|-----------------|
| Red blood cell cholinesterase | 15% of normal | 80-120% |
| Plasma pseudocholinesterase | 800 U/L | 4,000-12,000 U/L |
| Arterial blood gas | pH 7.28, PaCO2 55, PaO2 58, HCO3 22 | - |
| Glucose | 165 mg/dL | 70-100 mg/dL |
| Potassium | 3.2 mEq/L | 3.5-5.0 mEq/L |

### Diagnosis
**Organophosphate poisoning** presenting with SLUDGE/BBB syndrome (cholinergic toxidrome)

### Autonomic Pharmacology Principles Illustrated
1. **Acetylcholinesterase inhibition:** Organophosphates irreversibly inhibit AChE, causing acetylcholine accumulation at all cholinergic synapses.
2. **SLUDGE mnemonic:** Salivation, Lacrimation, Urination, Defecation, GI distress, Emesis - all muscarinic effects.
3. **Nicotinic effects:** Muscle fasciculations and eventual paralysis (neuromuscular junction), plus variable autonomic effects.
4. **Bradycardia:** Muscarinic M2 receptor overstimulation in the heart.
5. **Bronchospasm and secretions:** M3 receptor stimulation - most life-threatening effects.

### Treatment
1. **Decontamination:** Remove clothing, wash skin thoroughly
2. **Airway management:** Intubation with succinylcholine alternatives (prolonged paralysis risk)
3. **Atropine:** 2-4 mg IV bolus, double dose every 5 minutes until secretions dry (may need 100+ mg)
4. **Pralidoxime (2-PAM):** 1-2 g IV over 30 minutes within 24-48 hours to reactivate AChE before "aging"
5. **Benzodiazepines:** Diazepam 10 mg IV for seizures
6. **ICU admission** for respiratory support and monitoring

### Clinical Image

![Miosis](case_01_image.jpg)

*Miosis (pinpoint pupils) as seen in cholinergic toxicity from organophosphate poisoning. Pupillary constriction results from muscarinic receptor stimulation of the pupillary sphincter muscle.*

**Image Source:** Wikimedia Commons
**License:** CC BY 2.0
**URL:** https://commons.wikimedia.org/wiki/File:Miosis.jpg

---

## Case 2: Anticholinergic Toxicity (Diphenhydramine Overdose)

### Clinical Scenario
A 19-year-old female is brought to the emergency department by her roommate after intentionally ingesting multiple diphenhydramine tablets.

### Patient Demographics
- **Age:** 19 years
- **Sex:** Female
- **Weight:** 58 kg

### Chief Complaint
Confusion, agitation, and "seeing things" after intentional overdose

### History of Present Illness
The patient's roommate found an empty bottle of diphenhydramine (original 100 tablets of 25 mg) and a suicide note approximately 4 hours ago. The patient is now agitated, confused, picking at invisible objects, and talking to people who are not present. She appears flushed and has not urinated despite IV fluids.

### Physical Examination
- **Vital Signs:** BP 145/92 mmHg, HR 128 bpm, RR 20, T 39.2C
- **General:** Agitated, mumbling incoherently, picking at clothing and air
- **HEENT:** Mydriasis (7 mm bilaterally, sluggishly reactive), dry mucous membranes
- **Cardiovascular:** Tachycardic, regular rhythm
- **Abdominal:** Distended bladder palpable, absent bowel sounds
- **Neurological:** Disoriented to place and time, visual hallucinations, hyperreflexia
- **Skin:** Flushed, dry, hot to touch

### Workup and Results
| Test | Result | Reference Range |
|------|--------|-----------------|
| ECG | Sinus tachycardia, QRS 102 ms, QTc 485 ms | QRS <100 ms, QTc <450 ms |
| Urine drug screen | Negative | - |
| Creatinine | 0.9 mg/dL | 0.6-1.2 mg/dL |
| Glucose | 138 mg/dL | 70-100 mg/dL |
| CK | 450 U/L | 30-170 U/L |

**Bladder scan:** 650 mL residual

### Diagnosis
**Anticholinergic toxicity** from diphenhydramine overdose - "Hot as a hare, dry as a bone, red as a beet, blind as a bat, mad as a hatter"

### Autonomic Pharmacology Principles Illustrated
1. **Muscarinic blockade:** Diphenhydramine competitively blocks muscarinic receptors throughout the body.
2. **Central effects:** Crosses blood-brain barrier causing delirium, hallucinations, seizures.
3. **Peripheral effects:** Mydriasis, tachycardia (loss of vagal tone), urinary retention, decreased secretions, ileus.
4. **Hyperthermia:** Loss of sweating (sympathetic cholinergic pathway) impairs thermoregulation.
5. **QT prolongation:** Diphenhydramine also blocks cardiac potassium channels (off-target effect).

### Treatment
1. **Supportive care:** Primary approach
2. **Cooling measures:** Ice packs, cooling blankets for hyperthermia
3. **Benzodiazepines:** Lorazepam 2 mg IV for agitation and seizure prevention
4. **Foley catheter:** For urinary retention
5. **Activated charcoal:** If within 1-2 hours and airway protected
6. **Physostigmine:** Consider 1-2 mg IV slowly for severe, refractory agitation ONLY if no QRS widening (risk of seizures and asystole)
7. **Psychiatric consultation** after medical stabilization

### Clinical Image

![Atropine Structure](case_02_image.jpg)

*Chemical structure of atropine, a prototypical muscarinic antagonist. Diphenhydramine and many other drugs produce anticholinergic toxicity through the same mechanism of muscarinic receptor blockade.*

**Image Source:** Wikimedia Commons
**License:** Public Domain
**URL:** https://commons.wikimedia.org/wiki/File:Atropine.svg

---

## Case 3: Beta-Blocker Overdose

### Clinical Scenario
A 65-year-old male presents to the emergency department after intentional ingestion of his propranolol prescription.

### Patient Demographics
- **Age:** 65 years
- **Sex:** Male
- **Weight:** 82 kg

### Chief Complaint
Found lethargic with an empty pill bottle

### History of Present Illness
The patient has a history of hypertension, migraine prophylaxis, and depression. His wife found him minimally responsive with an empty bottle of propranolol 80 mg (90 tablets dispensed 3 days ago). He was recently diagnosed with terminal cancer and expressed suicidal ideation. Last seen normal 3 hours prior.

### Physical Examination
- **Vital Signs:** BP 70/45 mmHg, HR 38 bpm, RR 8, T 35.8C, SpO2 91% on room air
- **General:** Obtunded, responds only to painful stimuli
- **Cardiovascular:** Severe bradycardia, weak pulses
- **Respiratory:** Shallow respirations, mild wheezes bilaterally
- **Neurological:** GCS 7 (E2V2M3), pupils 3 mm reactive
- **Skin:** Cool, pale, mottled
- **Glucose (bedside):** 52 mg/dL

### Workup and Results
| Test | Result | Reference Range |
|------|--------|-----------------|
| ECG | Sinus bradycardia 38 bpm, first-degree AV block, QRS 88 ms | - |
| Glucose | 48 mg/dL | 70-100 mg/dL |
| Potassium | 5.4 mEq/L | 3.5-5.0 mEq/L |
| Lactate | 6.2 mmol/L | 0.5-2.0 mmol/L |
| Troponin I | 0.12 ng/mL | <0.04 ng/mL |

### Diagnosis
**Severe beta-blocker toxicity** with cardiogenic shock, bradycardia, bronchospasm, and hypoglycemia

### Autonomic Pharmacology Principles Illustrated
1. **Beta-1 blockade (cardiac):** Negative chronotropy (bradycardia) and negative inotropy (decreased contractility).
2. **Beta-2 blockade (bronchial):** Bronchospasm from unopposed parasympathetic tone - significant with non-selective blockers like propranolol.
3. **Beta-2 blockade (metabolic):** Hypoglycemia from impaired glycogenolysis and gluconeogenesis.
4. **CNS effects:** Propranolol is lipophilic and crosses BBB, causing sedation, seizures.
5. **Hyperkalemia:** Beta-2 receptors normally promote potassium uptake into cells.

### Treatment
1. **Airway management:** Intubation for airway protection
2. **IV fluids:** Bolus crystalloid for hypotension
3. **Atropine:** 1 mg IV for bradycardia (limited efficacy)
4. **Glucagon:** 5-10 mg IV bolus, then 2-10 mg/hr infusion - first-line specific antidote
5. **High-dose insulin/euglycemia therapy:** Regular insulin 1 unit/kg bolus, then 0.5-1 unit/kg/hr with dextrose
6. **Calcium gluconate:** 3 g IV for inotropy
7. **Vasopressors:** Norepinephrine if refractory
8. **Lipid emulsion:** 1.5 mL/kg 20% intralipid for lipophilic beta-blockers
9. **Dextrose:** For hypoglycemia
10. **Consider transcutaneous pacing** for refractory bradycardia

### Key Learning Points
- Beta-blocker toxicity causes the triad of bradycardia, hypotension, and hypoglycemia
- Non-selective agents (propranolol) also cause bronchospasm
- Glucagon works by activating adenylyl cyclase independent of beta-receptors
- High-dose insulin improves cardiac contractility through enhanced glucose utilization
- Lipid emulsion therapy is effective for lipophilic beta-blockers