Hypotension
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Hypotension
Definition
Hypotension is generally defined as a systolic blood pressure (SBP) < 90 mmHg, a diastolic BP < 60 mmHg, or a mean arterial pressure (MAP) < 65 mmHg. In hypertensive patients, a drop of ≥ 20–25% from baseline may be clinically significant even if absolute values remain above these thresholds.
Classification & Etiology
1. Absolute Hypotension (Systemic)
| Category | Examples |
|---|---|
| Hypovolemic | Hemorrhage, dehydration, burns, GI losses, third-spacing |
| Cardiogenic | MI, heart failure, arrhythmias, cardiomyopathy, severe valvular disease |
| Distributive | Septic shock, anaphylaxis, neurogenic shock, adrenal insufficiency |
| Obstructive | Pulmonary embolism, tension pneumothorax, cardiac tamponade, aortic stenosis |
| Iatrogenic / Drug-induced | Antihypertensives, diuretics, opioids, anesthetics, nitrates |
2. Orthostatic (Postural) Hypotension
A drop of ≥ 20 mmHg systolic or ≥ 10 mmHg diastolic within 3 minutes of standing.
Causes:
- Autonomic dysfunction (Parkinson's disease, diabetes mellitus, pure autonomic failure, multiple system atrophy)
- Volume depletion
- Medications (alpha-blockers, diuretics, tricyclics, antipsychotics)
- Prolonged bed rest / deconditioning
- Aging (impaired baroreflex sensitivity)
3. Postprandial Hypotension
BP drop > 20 mmHg within 2 hours of a meal; common in elderly and autonomic neuropathy.
4. Postoperative Hypotension
(Bailey & Love, p. 341): Associated with adverse outcomes; often due to hypovolaemia, myocardial impairment, or vasodilation from neuraxial (subarachnoid/epidural) anaesthesia.
Pathophysiology
Blood pressure = Cardiac Output (CO) × Systemic Vascular Resistance (SVR)
CO = Heart Rate × Stroke Volume
CO = Heart Rate × Stroke Volume
Hypotension results from:
- ↓ Preload (hypovolemia)
- ↓ Contractility (cardiogenic)
- ↓ SVR (distributive)
- ↓ Venous return (obstructive)
Clinical Presentation
| Severity | Features |
|---|---|
| Mild | Lightheadedness, dizziness, fatigue |
| Moderate | Syncope or presyncope, blurred vision, diaphoresis, pallor |
| Severe / Shock | Altered consciousness, cold/clammy extremities, oliguria, cyanosis |
Diagnosis
History
- Onset, triggers (posture, meals, medications)
- Volume status (fluid intake, bleeding, diarrhea)
- Comorbidities (cardiac disease, diabetes, Parkinson's)
- Full medication review
Examination
- Orthostatic vitals (supine, sitting, standing BP/HR)
- Skin: warm/flushed (distributive) vs. cold/clammy (cardiogenic/hypovolemic)
- Jugular venous pressure, heart sounds, lung auscultation
- Capillary refill, pulse volume
Investigations
| Test | Purpose |
|---|---|
| FBC, U&E, creatinine | Anemia, renal impairment, electrolytes |
| Blood glucose | Hypoglycemia-associated symptoms |
| Lactate | Tissue perfusion / shock severity |
| ECG | Arrhythmia, myocardial ischemia |
| Echo | Cardiogenic cause, tamponade, valvular disease |
| CTPA / CXR | PE, pneumothorax |
| Blood cultures | Sepsis |
| Cortisol / short synacthen | Adrenal insufficiency |
| Autonomic function tests | Orthostatic hypotension workup |
Management
General / Acute
- Position: Supine with legs elevated (Trendelenburg) if no contraindication
- IV access + fluid resuscitation (crystalloids, colloids, blood products as indicated)
- Treat the underlying cause (source control for sepsis, reperfusion for MI, pericardiocentesis for tamponade, decompression for pneumothorax)
- Vasopressors (if MAP < 65 mmHg despite adequate fluid resuscitation):
- Norepinephrine — first-line in septic shock
- Dopamine — alternative (higher risk of arrhythmia)
- Vasopressin — adjunct
- Phenylephrine — neurogenic/anaphylactic shock
- Inotropes (cardiogenic shock): dobutamine, milrinone
Orthostatic Hypotension (Harrison's, p. 709)
Step 1 — Remove reversible causes: withdraw or reduce vasoactive medications.
Step 2 — Non-pharmacologic interventions:
- Patient education on staged posture changes (supine → sitting → standing)
- Avoid large meals; avoid hot environments
- Isometric counterpressure maneuvers (leg crossing, squatting)
- Raise head of bed 10–20° to reduce supine hypertension and nocturnal diuresis
- Increase dietary fluid and salt intake
- Compression stockings / abdominal binders
Step 3 — Pharmacologic (if above fails):
- Fludrocortisone (mineralocorticoid; expands plasma volume)
- Midodrine (alpha-1 agonist vasoconstrictor)
- Droxidopa (L-DOPS) — norepinephrine prodrug; used in neurogenic orthostatic hypotension
Complications of Untreated Hypotension
- Syncope and falls (especially in elderly)
- Acute kidney injury (renal hypoperfusion)
- Myocardial ischemia
- Stroke / TIA
- Multi-organ dysfunction syndrome (shock)
- Death
Special Populations
| Population | Consideration |
|---|---|
| Elderly | Impaired baroreflex; polypharmacy; higher fall risk |
| Pregnant | Aortocaval compression in supine position; left lateral tilt required |
| Septic shock | Target MAP ≥ 65 mmHg; norepinephrine first-line (Surviving Sepsis Campaign) |
| Spinal cord injury | Neurogenic shock — loss of sympathetic tone; bradycardia + hypotension |
| Postoperative | Hypovolemia, anesthetic agents, bleeding — must be rapidly identified (Bailey & Love, p. 341) |
Sources: Harrison's Principles of Internal Medicine, 21st Ed. (p. 709) | Bailey & Love's Short Practice of Surgery, 28th Ed. (p. 341)
Septic shock
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septic shock management treatment antibiotics vasopressors fluid resuscitation
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Septic Shock
Definition (Sepsis-3 Criteria)
(Harrison's, p. 8257)
Sepsis = Suspected infection + acute organ dysfunction (SOFA score increase ≥ 2 points from baseline)
Septic shock = Sepsis plus all of the following despite adequate fluid resuscitation:
- Vasopressor therapy required to maintain MAP ≥ 65 mmHg
- Serum lactate > 2.0 mmol/L
This distinguishes septic shock from uncomplicated sepsis and identifies patients with the highest mortality (> 40%).
qSOFA (quick SOFA) — bedside screening tool (does not require labs):
- Altered mental status (GCS < 15)
- Respiratory rate ≥ 22 breaths/min
- SBP ≤ 100 mmHg ≥ 2 of 3 = high suspicion for sepsis/poor outcome; prompt full SOFA assessment
Pathophysiology
- Infection → systemic immune activation → release of PAMPs (e.g., LPS from gram-negatives, teichoic acid from gram-positives)
- Cytokine storm (TNF-α, IL-1, IL-6) → endothelial dysfunction + widespread vasodilation
- ↓ SVR → distributive shock → relative hypovolemia
- Microvascular thrombosis + tissue hypoperfusion → cellular hypoxia → lactic acidosis
- Myocardial depression (septic cardiomyopathy) — further reduces CO
- Multi-organ dysfunction syndrome (MODS) — kidneys, liver, lungs (ARDS), coagulation (DIC)
Common Sources & Organisms
| Source | Common Pathogens |
|---|---|
| Lung (pneumonia) | S. pneumoniae, Klebsiella, Pseudomonas |
| Urinary tract | E. coli, Klebsiella, Enterococcus |
| Abdomen (peritonitis) | Mixed gram-negatives, Bacteroides, Enterococcus |
| Skin / soft tissue | S. aureus (MRSA), Group A Streptococcus |
| Bloodstream (catheter) | Staph. epidermidis, Candida, S. aureus |
| CNS (meningitis) | N. meningitidis, S. pneumoniae |
Clinical Presentation
| System | Features |
|---|---|
| Cardiovascular | Hypotension, tachycardia, warm/flushed skin (early); cold/clammy (late) |
| Respiratory | Tachypnea, hypoxia, ARDS |
| Neurological | Confusion, agitation, obtundation |
| Renal | Oliguria, rising creatinine |
| GI/Hepatic | Ileus, jaundice, elevated transaminases |
| Haematological | Thrombocytopenia, DIC, leukocytosis or leukopenia |
| Metabolic | Elevated lactate, metabolic acidosis, hyperglycemia |
SOFA Score (Organ Dysfunction Assessment)
| Organ System | Parameters Scored |
|---|---|
| Respiratory | PaO₂/FiO₂ ratio |
| Coagulation | Platelets |
| Liver | Bilirubin |
| Cardiovascular | MAP / vasopressor requirement |
| CNS | Glasgow Coma Scale |
| Renal | Creatinine / urine output |
Score 0–24; higher = greater dysfunction; score ≥ 2 above baseline = sepsis-defining organ failure.
Investigations
| Test | Purpose |
|---|---|
| Blood cultures (×2) | Identify organism — obtain before antibiotics |
| FBC, CRP, procalcitonin | Infection severity, monitoring |
| Serum lactate | Tissue hypoperfusion; guides resuscitation |
| ABG | Acid-base status, PaO₂/FiO₂ |
| U&E, creatinine, LFTs | Organ dysfunction |
| Coagulation screen (INR, APTT, fibrinogen, D-dimer) | DIC |
| Urine culture, CXR, CT abdomen/pelvis | Source identification |
| Focused cardiac ultrasound (POCUS) | Volume status, cardiac function, tamponade |
Management
(Harrison's, p. 8273 | Surviving Sepsis Campaign Guidelines)
The "Hour-1 Bundle" (initiate within 1 hour of recognition)
- Measure lactate (re-measure if initial > 2 mmol/L)
- Obtain blood cultures before antibiotics
- Administer broad-spectrum antibiotics
- Begin IV crystalloid 30 mL/kg for hypotension or lactate ≥ 4 mmol/L
- Apply vasopressors if MAP < 65 mmHg despite fluids
1. Fluid Resuscitation
- IV crystalloid 30 mL/kg within first 3 hours
- Saline or balanced crystalloids (e.g., Hartmann's/lactated Ringer's) are acceptable
- Hydroxyethyl starches and gelatins are not recommended
- Further fluid guided by dynamic markers (pulse pressure variation, stroke volume variation, POCUS) and lactate clearance
2. Vasopressors
(Harrison's, p. 8273)
| Agent | Role |
|---|---|
| Norepinephrine | First-line — alpha + beta adrenergic; titrate to MAP ≥ 65 mmHg |
| Vasopressin | Add-on to norepinephrine to reduce its dose (0.03–0.04 units/min) |
| Epinephrine | Second-line; added if MAP target not achieved |
| Dopamine | Avoid except in bradycardic patients at low risk of tachyarrhythmias |
| Dobutamine | For myocardial dysfunction / low CO despite adequate filling pressures |
3. Antimicrobials
- Administer within 1 hour of septic shock recognition — mortality increases with each hour of delay
- Empiric broad-spectrum coverage based on likely source, local resistance patterns, and immune status:
| Suspected Source | Empiric Regimen (example) |
|---|---|
| Community pneumonia | Beta-lactam + macrolide or fluoroquinolone |
| HAP/VAP | Antipseudomonal beta-lactam ± aminoglycoside |
| Urosepsis | 3rd-gen cephalosporin or piperacillin-tazobactam |
| Abdominal | Piperacillin-tazobactam or carbapenem + metronidazole |
| Unknown source | Broad gram-positive + gram-negative + anaerobe coverage |
| MRSA risk | Add vancomycin or linezolid |
| Immunocompromised | Add antifungal (e.g., echinocandin) |
- De-escalate once organism and sensitivities known
- Total duration typically 7–10 days (shorter if source controlled)
4. Source Control
- Drainage of abscesses, removal of infected devices/lines, surgical debridement
- Should be achieved as soon as medically feasible
5. Corticosteroids
- Consider hydrocortisone 200–300 mg/day IV (continuous infusion or intermittent dosing) if shock remains refractory despite adequate fluids and vasopressors
- Do not use dexamethasone or high-dose steroids
6. Supportive ICU Care
| Intervention | Target / Details |
|---|---|
| Mechanical ventilation (ARDS) | Lung-protective: TV 6 mL/kg IBW, plateau pressure < 30 cmH₂O |
| Glucose control | Target 7.8–10 mmol/L (140–180 mg/dL); avoid hypoglycemia |
| Renal replacement therapy | For AKI with fluid overload, severe acidosis, or hyperkalemia |
| DVT prophylaxis | LMWH (unless bleeding risk) |
| Stress ulcer prophylaxis | PPI or H₂ blocker in high-risk patients |
| Nutrition | Early enteral nutrition preferred; avoid prolonged NPO |
| Transfusion | RBC transfusion if Hb < 70 g/L (< 90 g/L in myocardial ischemia) |
Monitoring Endpoints
| Parameter | Target |
|---|---|
| MAP | ≥ 65 mmHg |
| Urine output | ≥ 0.5 mL/kg/hr |
| Lactate clearance | ≥ 10% reduction per 2 hours; normalize to < 2 mmol/L |
| CVP (if used) | 8–12 mmHg (less reliable alone) |
| ScvO₂ | ≥ 70% |
Complications
- ARDS — most common cause of respiratory failure
- AKI — may require renal replacement therapy
- DIC — coagulopathy, bleeding, microvascular thrombosis
- Septic cardiomyopathy — reversible myocardial dysfunction
- Critical illness neuropathy/myopathy — prolonged weakness
- Secondary infections — fungal, C. difficile
Prognosis
- Septic shock carries in-hospital mortality of 40–60%
- Mortality correlates with: number of organs failing, lactate level, delay to antibiotics, source control adequacy
- Survivors face increased risk of long-term cognitive impairment, physical disability, and re-hospitalization (post-sepsis syndrome)
Sources: Harrison's Principles of Internal Medicine, 21st Ed. (pp. 8257, 8273) | Surviving Sepsis Campaign International Guidelines
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