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Intravenous anesthetics are drugs administered parenterally to induce anesthesia or sedation. Propofol is a widely used agent formulated as a 1% emulsion in soybean oil, glycerol, and egg phosphatide. It induces rapid anesthesia primarily due to its rapid distribution from the bloodstream to target tissues and is metabolized in the liver. However, it can cause significant pain on injection and hypertriglyceridemia. Fospropofol, a water-based prodrug of propofol, lacks these adverse effects.
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Supine syncope induced by needle insertion.

Peter Novak1, Vera Novak2

  • 1Department of Neurology, Mass General Brigham, Harvard Medical School, Boston, Massachusetts, USA pnovak2@bwh.harvard.edu.

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|April 25, 2025
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Summary
This summary is machine-generated.

Needle insertion can trigger supine reflex syncope, characterized by a drop in heart rate, blood pressure, and cerebral blood flow. This study details the hemodynamic changes during such events.

Keywords:
BradycardiaTachycardia, SupraventricularUltrasonography

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Area of Science:

  • Cardiology
  • Neurology
  • Autonomic Nervous System

Background:

  • Supine reflex syncope is a vasovagal response.
  • Needle phobia can trigger syncope in susceptible individuals.

Purpose of the Study:

  • To characterize the hemodynamic profile of supine reflex syncope triggered by needle insertion.
  • To investigate the physiological responses during syncope induced by needle insertion.

Main Methods:

  • Retrospective study of patients with orthostatic intolerance undergoing autonomic testing.
  • Continuous monitoring of cerebral blood flow velocity, end-tidal CO2, ECG, and blood pressure.
  • Needle insertion used to induce supine syncope.

Main Results:

  • Syncope occurred in 0.1% of patients following needle insertion.
  • Symptoms of cerebral hypoperfusion preceded loss of consciousness.
  • Hemodynamic changes included decreased heart rate, blood pressure, and cerebral blood flow velocity, with hyperventilation and widened transcranial Doppler signal.

Conclusions:

  • Supine syncope from needle insertion involves cardioinhibitory and vasodepressor responses.
  • Cerebral arteriolar vasodilation contributes to syncope.
  • Understanding these mechanisms aids in managing reflex syncope.