cardio.hypertensive-emergency.serotonin-syndrome-related.v1PRODUCTION

cardio.hypertensive-emergency.serotonin-syndrome-related.v1

Serotonin syndrome hypertensive crisis (autonomic instability + neuromuscular hyperactivity + altered mental status + HTN crisis ± hyperthermia)

cardiologyacuteadult

Hard-required inputs

0 / 11

Care setting:

Encounter flow

10/12 authored

Canonical 12-phase frame with authored status for this dossier.

Current phase

Frame

Detailed

Serotonin syndrome HTN crisis = excess 5-HT2A agonism from serotonergic polypharmacy → autonomic instability + neuromuscular hyperactivity (clonus dominant) + altered mental status + HTN crisis ± hyperthermia. Pharmacology pivot: STOP all serotonergic agents IMMEDIATELY; BENZODIAZEPINE FIRST for sympatholysis + neuromuscular + sedation; cyproheptadine (5-HT2A antagonist) for refractory severe SS; cooling for hyperthermia; AVOID droperidol (QTc), nitroprusside (cyanide), succinylcholine (rhabdo hyperK), bromocriptine (worsens SS).

Inputs

Actions

Advance rule

Set

Advance when

serotonin syndrome diagnosis confirmed by Hunter criteria + serotonergic exposure documented

Patient inputs (12)

age*demographic • CONTEXT

Elderly + serotonergic polypharmacy = highest SS risk; tramadol + SSRI common combo in older adults

serotonergic_medication_review*history • CONTEXT

not present

Confirms etiology — SSRI/SNRI/MAOI/TCA/tramadol/triptan/linezolid/methylene-blue/St-John's-wort/MDMA/cocaine; mandatory for diagnosis (Hunter criteria)

clonus_inducible_or_spontaneous*symptom • INITIAL_WORKUP

Hunter criteria cornerstone: spontaneous clonus = SS; inducible clonus + agitation/diaphoresis/temp >38 = SS; ocular clonus + agitation/diaphoresis = SS (Dunkley QJM 2003 PMID 12925718)

neuromuscular_exam*symptom • INITIAL_WORKUP

Hyperreflexia (lower > upper extremity), tremor, rigidity (severe), myoclonus — distinguish from NMS (rigidity dominant, hyporeflexia)

ecg_12_lead*imaging • INITIAL_WORKUP

not present

QTc prolongation risk from serotonergic + antiemetic combinations; baseline for droperidol AVOID decision

creatine_kinase*lab • INITIAL_WORKUP

Rhabdomyolysis common in severe SS (neuromuscular hyperactivity + hyperthermia); CK >5000 → aggressive IV fluids

creatinine*lab • INITIAL_WORKUP

Rhabdomyolysis-AKI risk; drives fluid + drug dosing; eGFR for nicardipine titration

sbp*vital • RED_FLAGS

Defines crisis threshold; drives titration of nicardipine/labetalol after benzo-first sympatholysis

dbp*vital • RED_FLAGS

Component of MAP; DBP >120 supports crisis criterion + autonomic severity

heart_rate*vital • RED_FLAGS

Sinus tachycardia universal in moderate-severe SS; >120 with HTN drives benzo escalation

temperature*vital • RED_FLAGS

Hyperthermia >38°C = moderate SS, >40°C = severe — life-threatening, requires aggressive cooling + paralysis (Boyer NEJM 2005)

lactatelab • INITIAL_WORKUP

Hyperthermia + neuromuscular activity → lactate elevation; tracks severity + response to cooling/paralysis

* = hard-required. Engine cannot meaningfully run until these are filled.

Severity triggers (5)

5 need judgement

informationallife_threateningserotonin_syndrome_with_hyperthermia_above_40c
Core temperature >40°C in serotonin syndrome — requires aggressive active cooling + paralysis + intubation; mortality risk if uncontrolled
Trigger could not be auto-evaluated — needs clinician judgement.
informationallife_threateningserotonin_syndrome_with_autonomic_instability_progression
Progressive autonomic instability — labile BP swings (HTN crisis alternating with hypotension), tachycardia >150, persistent diaphoresis despite benzo
Trigger could not be auto-evaluated — needs clinician judgement.
informationallife_threateningserotonin_syndrome_with_ICH_or_focal_neuro_deficit_in_HTN_crisis
Focal neurologic deficit or sudden severe headache in serotonin syndrome HTN crisis — exclude ICH (HTN crisis can drive ICH; severe SS can also have CNS complications)
Trigger could not be auto-evaluated — needs clinician judgement.
informationalsevereserotonin_syndrome_refractory_clonus_or_seizures
Persistent severe clonus / seizures despite escalating benzo + cessation of serotonergic agents
Trigger could not be auto-evaluated — needs clinician judgement.
informationalsevereserotonin_syndrome_rhabdomyolysis_AKI
CK >5000 + creatinine rise + myoglobinuria in severe SS — neuromuscular hyperactivity + hyperthermia driving muscle breakdown
Trigger could not be auto-evaluated — needs clinician judgement.

Workflow calculators

Run this disease's risk and dosing calculators inline.

TREATMENTrequiredDrives monitoring threshold

Loading…

Recommended regimen

Serotonin syndrome HTN crisis — STOP serotonergic agents; benzodiazepine-first sympatholysis + neuromuscular control; cyproheptadine for refractory severe disease; nicardipine/labetalol for BP; AVOID droperidol/nitroprusside/succinylcholine/bromocriptine

axis: serotonin_syndrome_htn_crisis_pharmacology

Selected axis "Serotonin syndrome HTN crisis — STOP serotonergic agents; benzodiazepine-first sympatholysis + neuromuscular control; cyproheptadine for refractory severe disease; nicardipine/labetalol for BP; AVOID droperidol/nitroprusside/succinylcholine/bromocriptine" by default fallback (first axis)

lorazepam
first line
benzodiazepine
1-2 mg IV q5-10 min PRN, max 8 mg in 1 h • IV • PRN
triggers: serotonin_syndrome_with_agitation_or_HTN_or_clonus, sympatholysis_required
Boyer NEJM 2005 PMID 15784664 first-line — benzodiazepine for sympatholysis + neuromuscular control + sedation; titrate to symptom control + sedation level
rxcui 6470
diazepam
first line
benzodiazepine
5-10 mg IV q5-10 min • IV • PRN
triggers: serotonin_syndrome_with_severe_clonus, persistent_autonomic_features
Boyer NEJM 2005 — alternative to lorazepam; longer half-life advantageous for sustained neuromuscular control
rxcui 3322
cyproheptadine
second line
h1_5ht2a_antagonist
12 mg PO/NG load → 2 mg PO/NG q2h until improvement; max 32 mg/24 h then 8 mg PO q6h maintenance • PO/NG • load + q2h titrated
triggers: moderate_to_severe_serotonin_syndrome_refractory_to_benzo, persistent_HTN_clonus_hyperthermia_after_benzo_load
Boyer NEJM 2005 + Gillman Pharmacother 2010 PMID 20429837 — 5-HT2A antagonist; case-series + animal-model evidence; reserved for moderate-severe disease; available only PO/NG (no IV)
rxcui 104592
nicardipine
second line
dihydropyridine_CCB
5 mg/h IV titrate q5 min by 2.5 mg/h to max 15 mg/h • IV • continuous
triggers: persistent_HTN_after_benzo_with_target_SBP_lt_160
AHA 2025 HTN guideline + ACC 2017 — preferred IV agent for HTN crisis; titratable + autoregulation-aware; avoids unopposed alpha concern of pure beta-blockers
rxcui 7396
labetalol
second line
mixed_alpha_beta_blocker
10-20 mg IV q10 min, max 300 mg cumulative; OR infusion 0.5-2 mg/min titrate • IV • PRN bolus or infusion
triggers: HTN_with_tachycardia_after_benzo, serotonin_syndrome_with_tachy_HTN_complex
AHA 2025 HTN guideline — mixed alpha-beta acceptable in SS HTN crisis (alpha component prevents unopposed alpha; benefit of HR control); avoid pure beta-blocker monotherapy in concurrent stimulant exposure
rxcui 6185
rocuronium
rescue
non_depolarizing_neuromuscular_blocker
0.6-1.2 mg/kg IV bolus • IV • as needed for intubation
triggers: severe_SS_requiring_intubation_with_rhabdomyolysis_or_hyperK
Preferred over succinylcholine for intubation in SS with rhabdomyolysis (avoids hyperK + ↑K from depolarization); supports active cooling + neuromuscular control in severe SS
rxcui 32521
AVOID droperidol/haloperidol high-dose
contraindication substitute
do_not_use
AVOID • N/A • N/A
triggers: serotonin_syndrome_with_QTc_prolongation_risk
QTc prolongation + dystonia risk; can worsen autonomic instability; antiemetic alternative if needed: ondansetron caution (5-HT3 antagonist — avoid in SS), prefer prochlorperazine or simply benzo
AVOID nitroprusside
contraindication substitute
do_not_use
AVOID • N/A • N/A
triggers: serotonin_syndrome_with_hyperthermia_or_rhabdomyolysis_or_hepatic_dysfunction
Cyanide accumulation worsens with hyperthermia + rhabdo + hepatic dysfunction; nicardipine or labetalol preferred
AVOID succinylcholine
contraindication substitute
do_not_use
AVOID • N/A • N/A
triggers: rhabdomyolysis_with_hyperK_in_serotonin_syndrome
Hyperkalemia from rhabdomyolysis + succinylcholine = arrest risk; use rocuronium for RSI
AVOID bromocriptine/dantrolene
contraindication substitute
do_not_use
AVOID • N/A • N/A
triggers: serotonin_syndrome_misdiagnosed_as_NMS
Bromocriptine is dopamine agonist — worsens serotonin syndrome (used for NMS); dantrolene has no role in SS (used for malignant hyperthermia + sometimes NMS); aggressive cooling + benzo + paralysis preferred for severe hyperthermia
STOP all serotonergic agents
first line
medication_cessation
STOP • N/A • mandatory
triggers: serotonin_syndrome_diagnosis
Boyer NEJM 2005 + Hunter criteria — mandatory first step; resolution in 70% within 24-48 h after cessation; if MAOI on board, requires 14-d washout before reintroducing serotonergic agent

outpatient playbook — drug actions (3)

1. continue HTN regimen (non-serotonergic-interaction-prone)
rxcui 17767
Amlodipine 5-10 ± lisinopril ± chlorthalidone • PO • daily
trigger: Stable maintenance
ACC/AHA 2025 HTN
2. continue non-serotonergic antidepressant if depression
rxcui 42347
Bupropion 150-300 mg PO daily (if appropriate) • PO • daily
trigger: Depression treatment
Non-serotonergic alternative; avoid SS recurrence
3. non-serotonergic chronic pain regimen
rxcui 7052
Acetaminophen + topical NSAIDs + non-pharm; AVOID tramadol/meperidine • PO/topical • as needed
trigger: Chronic pain
Lifetime SS-prevention strategy

Auto-drafted A&P note

outpatient

Subjective

- Possible entry pathways: Serotonergic agent (SSRI/SNRI/MAOI/TCA/tramadol/triptan/linezolid/methylene-blue/St-John's-wort/MDMA/cocaine) added or escalated within 24-72 h + autonomic + neuromuscular features (Boyer NEJM 2005 PMID 15784664); Hypertensive crisis + tachycardia + diaphoresis + tremor/clonus (lower-extremity dominant) + agitation/delirium + temperature ≥38°C — serotonin toxidrome; Inducible or spontaneous clonus with concurrent BP ≥180/120 — Hunter criteria entry trigger.

Objective

- No vitals, labs, or imaging entered for this encounter.

Assessment

**Serotonin syndrome hypertensive crisis (autonomic instability + neuromuscular hyperactivity + altered mental status + HTN crisis ± hyperthermia)** (cardio.hypertensive-emergency.serotonin-syndrome-related.v1).
Scope: Serotonin syndrome HTN crisis = excess 5-HT2A agonism from serotonergic polypharmacy → autonomic instability + neuromuscular hyperactivity (clonus dominant) + altered mental status + HTN crisis ± hyperthermia. Pharmacology pivot: STOP all serotonergic agents IMMEDIATELY; BENZODIAZEPINE FIRST for sympatholysis + neuromuscular + sedation; cyproheptadine (5-HT2A antagonist) for refractory severe SS; cooling for hyperthermia; AVOID droperidol (QTc), nitroprusside (cyanide), succinylcholine (rhabdo hyperK), bromocriptine (worsens SS).

No severity triggers fired against current inputs.

Plan

Regimen axis: **Serotonin syndrome HTN crisis — STOP serotonergic agents; benzodiazepine-first sympatholysis + neuromuscular control; cyproheptadine for refractory severe disease; nicardipine/labetalol for BP; AVOID droperidol/nitroprusside/succinylcholine/bromocriptine**.
1. lorazepam 1-2 mg IV q5-10 min PRN, max 8 mg in 1 h IV PRN (benzodiazepine, first line) — Boyer NEJM 2005 PMID 15784664 first-line — benzodiazepine for sympatholysis + neuromuscular control + sedation; titrate to symptom control + sedation level
2. diazepam 5-10 mg IV q5-10 min IV PRN (benzodiazepine, first line) — Boyer NEJM 2005 — alternative to lorazepam; longer half-life advantageous for sustained neuromuscular control
3. cyproheptadine 12 mg PO/NG load → 2 mg PO/NG q2h until improvement; max 32 mg/24 h then 8 mg PO q6h maintenance PO/NG load + q2h titrated (h1_5ht2a_antagonist, second line) — Boyer NEJM 2005 + Gillman Pharmacother 2010 PMID 20429837 — 5-HT2A antagonist; case-series + animal-model evidence; reserved for moderate-severe disease; available only PO/NG (no IV)
4. nicardipine 5 mg/h IV titrate q5 min by 2.5 mg/h to max 15 mg/h IV continuous (dihydropyridine_CCB, second line) — AHA 2025 HTN guideline + ACC 2017 — preferred IV agent for HTN crisis; titratable + autoregulation-aware; avoids unopposed alpha concern of pure beta-blockers
5. labetalol 10-20 mg IV q10 min, max 300 mg cumulative; OR infusion 0.5-2 mg/min titrate IV PRN bolus or infusion (mixed_alpha_beta_blocker, second line) — AHA 2025 HTN guideline — mixed alpha-beta acceptable in SS HTN crisis (alpha component prevents unopposed alpha; benefit of HR control); avoid pure beta-blocker monotherapy in concurrent stimulant exposure
6. rocuronium 0.6-1.2 mg/kg IV bolus IV as needed for intubation (non_depolarizing_neuromuscular_blocker, rescue) — Preferred over succinylcholine for intubation in SS with rhabdomyolysis (avoids hyperK + ↑K from depolarization); supports active cooling + neuromuscular control in severe SS
7. AVOID droperidol/haloperidol high-dose AVOID N/A N/A (do_not_use, contraindication substitute) — QTc prolongation + dystonia risk; can worsen autonomic instability; antiemetic alternative if needed: ondansetron caution (5-HT3 antagonist — avoid in SS), prefer prochlorperazine or simply benzo
8. AVOID nitroprusside AVOID N/A N/A (do_not_use, contraindication substitute) — Cyanide accumulation worsens with hyperthermia + rhabdo + hepatic dysfunction; nicardipine or labetalol preferred
9. AVOID succinylcholine AVOID N/A N/A (do_not_use, contraindication substitute) — Hyperkalemia from rhabdomyolysis + succinylcholine = arrest risk; use rocuronium for RSI
10. AVOID bromocriptine/dantrolene AVOID N/A N/A (do_not_use, contraindication substitute) — Bromocriptine is dopamine agonist — worsens serotonin syndrome (used for NMS); dantrolene has no role in SS (used for malignant hyperthermia + sometimes NMS); aggressive cooling + benzo + paralysis preferred for severe hyperthermia
11. STOP all serotonergic agents STOP N/A mandatory (medication_cessation, first line) — Boyer NEJM 2005 + Hunter criteria — mandatory first step; resolution in 70% within 24-48 h after cessation; if MAOI on board, requires 14-d washout before reintroducing serotonergic agent

Setting playbook (outpatient) — Long-term PCP + psychiatry + pain medicine coordination — sustained avoidance of serotonergic combinations, BP <130/80 if persistent HTN, ADR card carried, safer-alternative regimen maintained, harm reduction for unavoidable serotonergic exposures
12. continue HTN regimen (non-serotonergic-interaction-prone) Amlodipine 5-10 ± lisinopril ± chlorthalidone PO daily — Stable maintenance (ACC/AHA 2025 HTN)
13. continue non-serotonergic antidepressant if depression Bupropion 150-300 mg PO daily (if appropriate) PO daily — Depression treatment (Non-serotonergic alternative; avoid SS recurrence)
14. non-serotonergic chronic pain regimen Acetaminophen + topical NSAIDs + non-pharm; AVOID tramadol/meperidine PO/topical as needed — Chronic pain (Lifetime SS-prevention strategy)

Non-pharmacologic actions:
- Sustained engagement with psychiatry/pain teams
- ADR card on person + family awareness
- Annual medication review with pharmacy
- Education re: serotonergic OTC + supplement avoidance (St John's wort, 5-HTP, dextromethorphan)

AVOID / contraindication checks:
- Droperidol_avoid_in_serotonin_syndrome_QTc
- Nitroprusside_avoid_in_serotonin_syndrome_hyperthermia_rhabdo_cyanide_risk
- Succinylcholine_avoid_with_rhabdomyolysis_hyperK
- Bromocriptine_dantrolene_no_role_in_serotonin_syndrome (used for NMS / MH)
- Stop_serotonergic_agents_mandatory (Boyer NEJM 2005)
- Maoi_14d_washout_before_serotonergic_reintroduction
- 5HT3_antagonist_ondansetron_avoid_or_caution_in_SS_could_worsen
- Meperidine_AVOID_can_trigger_or_worsen_SS_via_serotonin_reuptake_inhibition

Monitoring

Regimen monitoring:
- continuous ECG q15min BP (AHA 2025 HTN)
- temperature q15-30min with active cooling if >38.5C aggressive if >40C
- serial neuromuscular exam q2-4h for clonus resolution (Hunter criteria)
- CK q6h if rhabdomyolysis suspected or severe SS
- BMP q6h for renal function K in rhabdo
- mental status and agitation assessment q1h
- UOP target >1mL/kg/h if rhabdomyolysis (alkalinization not routinely required)
- lactate q4-6h if hyperthermic

Setting (outpatient) monitoring:
- Quarterly BP + medication reconciliation
- Annual ECG + lipid + A1c
- Mental health follow-up per psychiatry

Follow-up plan: Comprehensive medication review + safer alternatives (e.g., switch tramadol to non-serotonergic analgesic; switch SSRI to bupropion if depression amenable); psychiatry consult if depression/SI driver; pharmacy MTM for SS-prevention education; document SS in allergy/ADR list; pain medicine consult if chronic pain driving tramadol use; if MAOI was on board, mandatory 14-d washout before reintroducing serotonergic agent; outpatient PCP follow-up at 1 week
- Close-out criterion: medication regimen revised + ADR documented + follow-up booked + patient/caregiver education completed

Monitoring phase: Continuous ECG + telemetry; q15-30 min BP + temp until stable; serial neuromuscular exam q2-4h (clonus resolution); CK q6h if rhabdo; UOP target >1 mL/kg/h if rhabdo; mental status reassessment q1h initially

Disposition

Current setting: outpatient — Long-term PCP + psychiatry + pain medicine coordination — sustained avoidance of serotonergic combinations, BP <130/80 if persistent HTN, ADR card carried, safer-alternative regimen maintained, harm reduction for unavoidable serotonergic exposures

Disposition criteria:
- Long-term continuation; cross-link to cardio.htn.core.v1 + psych.depression.core.v1 if applicable for chronic management

Escalation triggers (move to higher acuity):
- Recurrent SS features → ED + flag offending agent
- BP rebound → urgent visit
- New depression/SI → emergent psychiatry

Earlier-Return Triggers

Return-precaution thresholds (watch for):
- [LIFE_THREATENING] Core temperature >40°C in serotonin syndrome — requires aggressive active cooling + paralysis + intubation; mortality risk if uncontrolled
- [LIFE_THREATENING] Progressive autonomic instability — labile BP swings (HTN crisis alternating with hypotension), tachycardia >150, persistent diaphoresis despite benzo
- [LIFE_THREATENING] Focal neurologic deficit or sudden severe headache in serotonin syndrome HTN crisis — exclude ICH (HTN crisis can drive ICH; severe SS can also have CNS complications)

Citations

- Boyer & Shannon NEJM 2005 (PMID 15784664) — landmark serotonin syndrome review + Hunter criteria (Dunkley QJM 2003 PMID 12925718) + 2025 ACC/AHA HTN (Whelton) [PMID:15784664](https://pubmed.ncbi.nlm.nih.gov/15784664/)
- Cited evidence (PMID 16967514) [PMID:16967514](https://pubmed.ncbi.nlm.nih.gov/16967514/)
- Cited evidence (PMID 12925718) [PMID:12925718](https://pubmed.ncbi.nlm.nih.gov/12925718/)
- Cited evidence (PMID 20429837) [PMID:20429837](https://pubmed.ncbi.nlm.nih.gov/20429837/)
- Cited evidence (PMID 23230406) [PMID:23230406](https://pubmed.ncbi.nlm.nih.gov/23230406/)

Last reconciled with current guidelines: 2026-05-15.

References

Boyer & Shannon NEJM 2005 (PMID 15784664) — landmark serotonin syndrome review + Hunter criteria (Dunkley QJM 2003 PMID 12925718) + 2025 ACC/AHA HTN (Whelton) — PMID:15784664
Cited evidence (PMID 16967514) — PMID:16967514
Cited evidence (PMID 12925718) — PMID:12925718
Cited evidence (PMID 20429837) — PMID:20429837
Cited evidence (PMID 23230406) — PMID:23230406