Mechanisms of Toxicity and Clinical Presentation
Barbiturates are characterized by a narrow therapeutic index. This means the margin between the therapeutic dose and the toxic dose is minimal. Consequently, the risk of acute intoxication remains high in clinical practice.
The clinical presentation of severe poisoning develops due to massive depression of central nervous system (CNS) functions. The patient loses consciousness, reflex activity is completely abolished, and a deep comatose state ensues.
The primary life-threatening danger involves the toxin's effect on vital centers located in the medulla oblongata:
- Respiratory center: Its depression leads to a significant decrease in minute ventilation. Ultimately, complete respiratory arrest is the direct cause of death.
- Vasomotor center: Its suppression causes a sharp drop in blood pressure (BP). Hypotension is further exacerbated by the ganglion-blocking action of barbituates and their direct myotropic (relaxing) effect on the vascular wall.
Treatment Principles: Preventing Absorption
The treatment strategy is built upon three key pillars: preventing further entry of the poison into the bloodstream, accelerating its elimination, and maintaining vital body functions.
The first stage involves decontaminating the gastrointestinal tract to halt drug absorption. The following measures are performed:
- Copious gastric lavage.
- Administration of saline cathartics to accelerate the transit of contents through the intestine.
- Use of adsorbents that bind the toxin within the gastrointestinal lumen.
Detoxification: Elimination of Absorbed Substance
To eliminate barbiturates that have already entered the systemic circulation, active detoxification methods are employed:
- Forced diuresis. Large volumes of fluid (typically 1–2 liters of 0.9% NaCl solution) are administered intravenously, followed by potent diuretics such as furosemide or mannitol.
- Alkalinization of the filtrate. Using alkaline drinks or administering appropriate solutions aims to shift the pH of the renal filtrate toward the alkaline side. This mechanism is crucial: it prevents the reabsorption of barbiturates in the renal tubules, forcing them to be excreted faster in the urine.
- Extracorporeal methods. When blood concentrations of the toxin are critically high, medical management alone is insufficient. In such cases, mechanical blood purification—hemadsorption or hemodialysis—is indicated.
Symptomatic Therapy and Resuscitation
The third direction of therapy targets life-threatening symptoms and organ support.
Respiratory support depends on the severity of poisoning:
- In mild forms, analeptics (e.g., bemegride) may be used to stimulate the respiratory center.
- In severe forms, analeptics are strictly contraindicated, as their administration only exhausts the CNS and worsens the patient's condition. The only adequate method is mechanical ventilation.
Hemodynamic support is required if circulatory shock or marked hypotension develops. To stabilize blood pressure, intravenous administration of plasma expanders (to restore intravascular volume) and vasopressors (e.g., norepinephrine) are used.