4.3 Neurological Emergencies & Acute Toxicology

4.3 Neurological Emergencies & Acute Toxicology

Core Clinical Rule: In suspected Acute Bacterial Meningitis, never delay antibiotic administration for a CT scan or lumbar puncture if the patient is unstable or imaging will take $> 30\text{ minutes}$; obtain blood cultures and administer IV Ceftriaxone 2 g combined with IV Dexamethasone 10 mg immediately. Dexamethasone must be given prior to or concurrently with the first antibiotic dose; administering it hours after antibiotics confers no benefit. In Status Epilepticus, time is brain: after 5 minutes of continuous convulsion, neuronal death accelerates; escalate without delay through the emergency pharmacological protocol.

Neurological emergencies and acute poisonings represent some of the most critical, time-sensitive presentations encountered by Clinical Officers in casualty departments across Kenya. Rapid identification of meningeal inflammation, distinguishing stroke subtypes, arresting prolonged seizures, and delivering antidotal therapy in pesticide or venom toxicity can mean the difference between complete neurological recovery and fatal multiorgan failure.

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1. Acute Bacterial Meningitis

Acute Bacterial Meningitis is a life-threatening infection of the arachnoid mater, pia mater, and intervening cerebrospinal fluid (CSF). Pathogens reach the subarachnoid space via hematogenous dissemination from nasopharyngeal colonization or direct contiguous spread (otitis media, mastoiditis, sinusitis, or penetrating skull trauma).

Microbial Etiology by Patient Age & Predisposition

• Neonates ($< 1\text{ month}$): Streptococcus agalactiae (Group B Streptococcus), Escherichia coli, and Listeria monocytogenes.
• Infants, Children & Adults ($1\text{ month} - 50\text{ years}$): Streptococcus pneumoniae (Pneumococcus; leading cause across all ages in Kenya), Neisseria meningitidis (Meningococcus; epidemic potential in the African meningitis belt), and Haemophilus influenzae type b (unimmunized individuals).
• Older Adults ($> 50\text{ years}$) & Immunocompromised: Streptococcus pneumoniae, Neisseria meningitidis, and Listeria monocytogenes (impaired cell-mediated immunity).
• Advanced HIV Disease (CD4 $< 100\text{ cells}/\mu\text{L}$): Cryptococcus neoformans (subacute presentation) and Mycobacterium tuberculosis.

Clinical Presentation & Physical Examination

• The Classic Clinical Triad: Fever, nuchal rigidity (neck stiffness), and altered mental state (present in $> 70%$ of adults; virtually all patients exhibit at least two signs from fever, headache, neck stiffness, and altered consciousness).
• Meningeal Irritation Signs:
  • Kernig's Sign: With the patient supine and hip flexed at 90°, passive extension of the knee elicits severe resistance and pain in the posterior thigh.
  • Brudzinski's Sign: With the patient supine, passive flexion of the neck induces involuntary spontaneous flexion of the hips and knees.
  • Jolt Accentuation: Worsening of headache by rotating the head horizontally at a frequency of 2 to 3 rotations per second (highly sensitive physical sign).
• Signs of Raised Intracranial Pressure (ICP): Depressed Glasgow Coma Scale (GCS), papilledema, cranial nerve palsies (CN III and VI), and Cushing's Triad (bradycardia, systolic hypertension with widened pulse pressure, and irregular/agonal respirations; heralds impending brainstem herniation).

Lumbar Puncture (LP) & CSF Analysis

• Contraindications to Immediate LP (Mandating CT Prior to Puncture): New-onset focal neurological deficits, new-onset seizures within 1 week, papilledema, severely depressed consciousness ($GCS < 10$), or known immunocompromise. If a head CT is required, draw blood cultures and immediately administer IV Ceftriaxone + Dexamethasone before transporting the patient to the scanner!

Stepwise Pharmacological Management Protocol

1. Empirical Antibiotic Therapy:
   • Adults ($1\text{ month} - 50\text{ years}$): IV Ceftriaxone 2 g every 12 hours (or IV Cefotaxime 2 g every 6 hours) infused over 30 minutes for 10 to 14 days.
   • Neonates, Adults $> 50\text{ years}$, or Immunocompromised: Add IV Ampicillin 2 g every 4 hours to cover Listeria monocytogenes (resistant to all cephalosporins).
2. Adjunctive Corticosteroid Therapy (Dexamethasone):
   • Dose & Administration: IV Dexamethasone 10 mg administered 15 to 20 minutes before or concurrently with the first antibiotic dose, continued at 10 mg IV every 6 hours for 4 days.
   • Evidence-Based Rationale: Antibiotic-induced bacterial lysis releases cell wall endotoxins and teichoic acid fragments, triggering intense subarachnoid inflammation. Dexamethasone blunts cytokine release (TNF-alpha, IL-1), significantly reducing sensorineural hearing loss, neurological sequelae, and overall mortality in pneumococcal meningitis.
3. Chemoprophylaxis for Close Contacts (Meningococcal Disease):
   • Single dose Oral Ciprofloxacin 500 mg, OR Oral Rifampicin 600 mg twice daily for 2 days, OR single dose IM Ceftriaxone 250 mg (preferred in pregnant women).

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2. Acute Stroke Management

Stroke is an acute focal neurological deficit of vascular origin lasting $> 24\text{ hours}$ or leading to death. Approximately 85% are Ischemic Strokes (thrombotic, cardioembolic secondary to atrial fibrillation, or lacunar) and 15% are Hemorrhagic Strokes (intracerebral hemorrhage [ICH] secondary to chronic hypertension or Charcot-Bouchard microaneurysm rupture, or subarachnoid hemorrhage [SAH] secondary to saccular 'berry' aneurysm rupture).

The FAST Assessment Protocol

• F - Face: Sudden facial droop, asymmetry when smiling.
• A - Arms: Arm drift or motor weakness when held elevated at 90° for 10 seconds.
• S - Speech: Slurred speech, expressive aphasia, or inability to repeat simple phrases.
• T - Time: Document the precise 'last known normal' time and transport urgently.

Emergency Neuroimaging: The First Crucial Step

Every suspected stroke patient requires an immediate Non-Contrast Brain CT (NCCT). It is clinically impossible to distinguish ischemic from hemorrhagic stroke without imaging. NCCT reveals:

• Hemorrhagic Stroke: Immediate hyperdense (bright white) intraparenchymal blood or blood within the basal cisterns.
• Ischemic Stroke: Typically normal in the initial hyperacute window ($< 3 - 6\text{ hours}$), or shows subtle early ischemic changes (loss of insular ribbon, sulcal effacement, dense middle cerebral artery [MCA] sign). Its primary emergency role is to definitively rule out intracranial hemorrhage.

Acute Blood Pressure Management Strategy

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|                    BLOOD PRESSURE TARGETS IN ACUTE STROKE                         |
+-----------------------------------------------------------------------------------+
| ISCHEMIC STROKE (NOT Eligible for Thrombolysis / Conservative):                   |
| • PERMISSIVE HYPERTENSION: Withhold antihypertensives unless:                     |
|   Systolic BP > 220 mmHg OR Diastolic BP > 120 mmHg.                              |
| • Rationale: Cerebral autoregulation is lost in the ischemic penumbra. Blood flow  |
|   is linearly dependent on systemic MAP. Lowering BP precipitates penumbral death! |
| • If BP > 220/120: Cautiously reduce MAP by 15% over the first 24 hours using IV  |
|   Labetalol (10-20 mg IV) or Nicardipine.                                         |
+-----------------------------------------------------------------------------------+
| ISCHEMIC STROKE (Eligible for Intravenous Thrombolysis with Alteplase):           |
| • Pre-treatment BP must be strictly reduced to < 185/110 mmHg.                    |
| • Post-thrombolysis BP must be maintained < 180/105 mmHg to prevent hemorrhage.   |
+-----------------------------------------------------------------------------------+
| ACUTE INTRACEREBRAL HEMORRHAGE (Hemorrhagic Stroke):                              |
| • Rapid, controlled lowering of Systolic BP to target 140 mmHg (range 130-150)    |
|   within 1-2 hours using IV Labetalol or Hydralazine to limit hematoma expansion. |
+-----------------------------------------------------------------------------------+

Antiplatelet & Supportive Protocols

• Aspirin Loading: In acute ischemic stroke, administer chewable Aspirin 300 mg orally or rectally within 24 to 48 hours after symptom onset, provided intracranial hemorrhage is excluded on CT. If intravenous thrombolysis was administered, hold aspirin for 24 hours post-thrombolysis.
• Glycemic Control: Maintain blood glucose between 7.8 and 10.0 mmol/L; treat hyperglycemia ($> 10.0\text{ mmol/L}$) with subcutaneous soluble insulin. Avoid hypotonic intravenous dextrose solutions (causes cerebral edema).
• Temperature Control: Aggressively treat pyrexia ($> 37.5^\circ\text{C}$) with paracetamol; fever increases metabolic rate and accelerates penumbral necrosis.

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3. Status Epilepticus Stepwise Emergency Protocol

Operational Definition

Status Epilepticus is defined as a continuous, unremitting seizure lasting $\ge 5\text{ minutes}$, or two or more discrete seizures without complete interictal recovery of consciousness. The traditional 30-minute definition has been abandoned because irreversible excitotoxic neuronal injury (NMDA receptor activation and intracellular calcium influx) and pharmacoresistance begin at 5 minutes.

Timed Stepwise Pharmacological Algorithm

[0 to 5 MINUTES: INITIAL STABILIZATION]
• Airway: Position in lateral recovery position, suction secretions, insert nasopharyngeal airway
• Breathing: 100% High-flow oxygen via non-rebreather mask; monitor SpO2
• Circulation: Establish IV access, draw blood for glucose, electrolytes, FBC, anticonvulsant levels
• Check Point-of-Care Blood Glucose: If < 3.5 mmol/L, give 50 mL of 50% Dextrose IV (+ Thiamine 100 mg IV)
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                 v (Seizure continues >= 5 minutes)
[5 to 10 MINUTES: FIRST-LINE THERAPY - EMERGENT PHASE]
• IV Diazepam: 10 mg slow IV push (2-5 mg/min). May repeat ONCE at 10 minutes if seizures persist
  (Alternatives: IV Lorazepam 4 mg, or Rectal Diazepam 10-20 mg, or IM Midazolam 10 mg)
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                 v (Seizure continues >= 10-15 minutes)
[10 to 30 MINUTES: SECOND-LINE THERAPY - URGENT CONTROL PHASE]
• IV Phenytoin Loading Dose: 18 to 20 mg/kg IV infused in 0.9% Normal Saline at <= 50 mg/min
  - MANDATORY PRECAUTIONS: Continuous ECG and blood pressure monitoring (risk of severe hypotension
    and ventricular arrhythmias). NEVER mix with Dextrose (causes instant chemical precipitation).
  - (Alternatives: IV Levetiracetam 60 mg/kg over 10 min, or IV Sodium Valproate 40 mg/kg over 10 min)
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                 v (Seizure continues >= 30 minutes)
[> 30 MINUTES: THIRD-LINE THERAPY - REFRACTORY STATUS EPILEPTICUS]
• Emergent Endotracheal Intubation & Mechanical Ventilation in HDU / ICU
• Continuous General Anesthetic Infusion titrated to EEG burst suppression:
  - Propofol: 1-2 mg/kg IV bolus, then continuous infusion at 2-10 mg/kg/hour, OR
  - Midazolam: 0.2 mg/kg IV bolus, then continuous infusion at 0.05-2.0 mg/kg/hour

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4. Acute Toxicology in the Kenyan Setting

Organophosphate & Carbamate Poisoning

Organophosphates (e.g., diazinon, malathion, chlorpyrifos) and carbamates are common agricultural pesticides in Kenya. They bind to and inhibit the enzyme acetylcholinesterase (AChE) through phosphorylation, leading to massive accumulation of acetylcholine at muscarinic, nicotinic, and central nervous system synapses.

+-----------------------------------------------------------------------------------+
|              ORGANOPHOSPHATE TOXIDROME: CLINICAL MANIFESTATIONS                   |
+-----------------------------------------------------------------------------------+
| MUSCARINIC OVERDRIVE: "SLUDGE" / "DUMBELS"                                        |
| • Salivation (copious pooling)         • Diarrhea                                 |
| • Lacrimation (tearing)                • Urination                                |
| • Urination                            • Miosis (pinpoint, unreactive pupils)     |
| • Defecation                           • Bradycardia                              |
| • GI distress (cramping, vomiting)     • Bronchorrhea (masses of watery secretions)|
| • Emesis                               • Bronchospasm (severe wheeze / stridor)   |
|                                        • Emesis                                   |
|                                        • Lacrimation / Salivation                 |
| *PRIMARY KILLER: Asphyxiation from copious Bronchorrhea & Bronchospasm ('wet chest')|
+-----------------------------------------------------------------------------------+
| NICOTINIC OVERDRIVE:                                                              |
| • Striated muscle fasciculations, muscle twitches, profound muscular weakness,    |
|   and diaphragmatic respiratory muscle paralysis.                                 |
+-----------------------------------------------------------------------------------+
| CENTRAL NERVOUS SYSTEM OVERDRIVE:                                                 |
| • Anxiety, restlessness, confusion, generalized seizures, central coma.          |
+-----------------------------------------------------------------------------------+

• Stepwise Resuscitation Protocol:
  1. Personal Protective Equipment (PPE): Healthcare personnel must wear nitrile gloves and fluid-impermeable aprons to prevent transdermal poisoning.
  2. Decontamination: Immediately strip off all contaminated clothing and store in sealed plastic bags. Wash the patient's entire skin, hair, and nails thoroughly with copious soap and water.
  3. Airway & Oxygenation: Suction airway aggressively; administer high-flow oxygen. Hypoxemic patients have high risk of ventricular fibrillation if atropine is given without oxygenation.
  4. Intravenous Atropine (Competitive Muscarinic Antagonist):
     • Administer Atropine 2 to 5 mg IV bolus immediately.
     • Double the dose every 5 to 10 minutes if there is no response (e.g., 2 mg $\rightarrow$ 4 mg $\rightarrow$ 8 mg $\rightarrow$ 16 mg), until complete atropinization is achieved.
     • CLINICAL ENDPOINTS OF ATROPINIZATION: Clear lungs on auscultation (complete resolution of bronchorrhea and bronchospasm), heart rate $> 80\text{ bpm}$, systolic BP $> 90\text{ mmHg}$, and dry axillae/skin. Critical Rule: Pupillary dilation (mydriasis) alone is NOT an endpoint of atropinization! Tachycardia and mydriasis can be driven by nicotinic receptors; never stop atropine if the lungs remain 'wet' with secretions.
     • Maintain continuous atropine infusion (10–20% of the total dose required for initial atropinization per hour) for 24 to 48 hours.
  5. Pralidoxime (2-PAM) (Oxime Cholinesterase Reactivator):
     • Administer Pralidoxime 1 to 2 g IV in 100 mL saline over 30 minutes, followed by an infusion of 500 mg/hr. Oximes detach the organophosphate moiety from AChE before irreversible covalent 'aging' occurs, reversing nicotinic skeletal muscle weakness and fasciculations.

Acute Paracetamol (Acetaminophen) Poisoning

• Pathophysiology: At therapeutic doses, 90% of paracetamol undergoes hepatic glucuronidation and sulfation. Approximately 5–10% is metabolized by cytochrome P450 (CYP2E1) into the highly reactive, electrophilic toxic metabolite N-acetyl-p-benzoquinone imine (NAPQI), which is rapidly neutralized by hepatic glutathione to non-toxic mercapturic acid. In acute overdose ($> 150\text{ mg/kg}$ or $> 7.5 - 10\text{ g}$ in adults), glucuronidation saturates, CYP2E1 shunts massive amounts to NAPQI, and hepatic glutathione is depleted by $> 70%$. Unconjugated NAPQI binds covalently to hepatocyte macromolecules, causing centrilobular hepatic necrosis.
• Antidotal Therapy (N-Acetylcysteine - NAC):
  • NAC acts as a glutathione precursor and glutathione substitute, directly conjugating NAPQI. It is nearly 100% hepatoprotective if initiated within 8 hours of acute ingestion, but remains beneficial even in late-presenting fulminant hepatic failure.
  • Intravenous NAC Regimen (3-Bag Infusion Protocol):
    • Bag 1: 150 mg/kg in 200 mL 5% Dextrose infused over 1 hour.
    • Bag 2: 50 mg/kg in 500 mL 5% Dextrose infused over 4 hours.
    • Bag 3: 100 mg/kg in 1000 mL 5% Dextrose infused over 16 hours (total dose: 300 mg/kg over 21 hours).

Snakebite Envenomation in Kenya

Envenomation is endemic in arid and semi-arid counties (Baringo, Kitui, Machakos, Kilifi, Turkana). Bites are classified into three primary clinical syndromes based on venom constituents:

• Harmful Traditional Practices to Avoid: Strictly DO NOT make incisions or cuts across the bite site, apply arterial tourniquets (causes ischemia, gangrene, and limb loss), suck venom by mouth, apply potassium permanganate, or apply local snake stones ('black stones').
• First-Aid Protocol: Keep patient calm and reassure them; immobilize the bitten limb using a splint and keep it at heart level; remove constricting rings and jewelry; transport urgently to hospital.
• Indications for Antivenom (e.g., Inoserp PAN-AFRICA, SAIMR Polyvalent):
  1. Systemic envenomation: Neurotoxicity, systemic bleeding, abnormal 20-Minute Whole Blood Clotting Test (20WBCT) (blood remains liquid in a dry glass tube after 20 minutes), shock, or cardiac arrhythmias.
  2. Severe local envenomation: Swelling involving more than half the bitten limb, rapid progression within hours, or swelling of a whole digit.
  • Administration: Reconstitute polyvalent antivenom and infuse IV in 200–500 mL 0.9% Normal Saline over 30 to 60 minutes. Keep IV Epinephrine (Adrenaline) 1:1000 at bedside to treat immediate anaphylactoid reactions.