Hiccups (Singultus): Mechanism, Symptoms & Management

Hiccups are involuntary, spasmodic contractions of the diaphragm and intercostal muscles, followed by sudden glottic closure → the characteristic "hic" sound.

Pathophysiology

• Afferent limb: Vagus, phrenic, sympathetic (T6–T12) — gastric distension, irritation, temperature change, alcohol, excitement.
• Central pattern generator: Medullary "hiccup center" (near respiratory centers).
• Efferent limb: Phrenic nerves (diaphragm), accessory nerves (intercostals), glottis closure (vagus).

Classification

• Acute (<48 hrs): Benign, self-limited; triggers: overeating, carbonation, alcohol, temperature change, stress.
• Persistent (48 hrs – 1 month): Investigate underlying cause.
• Intractable (>1 month): Often structural/neurologic/metabolic.

Common Causes (Persistent/Intractable)

• GERD, hiatal hernia, esophagitis
• CNS: stroke, MS, tumor, TBI, encephalitis
• Thoracic: pneumonia, pleural effusion, pericarditis, MI
• Abdominal: pancreatitis, hepatitis, subphrenic abscess
• Metabolic: uremia, hyperglycemia, hyponatremia, hypocalcemia
• Drugs: steroids, benzodiazepines, opioids, chemotherapy, dopamine agonists
• Psychogenic

Physical Maneuvers (Acute)

• Breath hold (↑PaCO₂ inhibits hiccup center)
• Valsalva / bear down
• Cold water swallow / ice water gargle
• Supraclavicular pressure / phrenic nerve block (clinical)
• Paper bag rebreathing

Pharmacologic (Persistent)

• Baclofen 10 mg TID (first-line evidence)
• Gabapentin, metoclopramide, chlorpromazine, haloperidol, amantadine
• Proton pump inhibitor if GERD suspected

When to See a Doctor

• Duration >48 hours
• Interfering with sleep, eating, breathing
• Associated neurologic, GI, or cardiac symptoms