Etiology and causes of development
The development of anaphylactic shock is based on the immediate interaction of antigen and antibodies following contact between the body and an allergen. In a surgical clinic, contact with potentially hazardous substances occurs regularly, which requires a high level of vigilance from the physician.
The main causes (allergens) in surgical practice include:
- Protein-based blood substitutes used for infusion therapy.
- Various immunological agents.
- Antibacterial agents (antibiotics).
- Chemical antiseptics, primarily iodine preparations, which are frequently used for surgical site preparation or during angiography.
A special risk group comprises patients with a history of concurrent allergic diseases. Particular attention should be paid to patients suffering from bronchial asthma, drug dermatitis, and other manifestations of hypersensitivity.
Clinical forms of anaphylactic shock
Depending on which organ systems predominantly manifest symptoms, three main clinical forms of anaphylactic shock are distinguished:
- Cardiovascular form. Characterized by acute circulatory failure. The patient presents with marked tachycardia, a sharp drop in blood pressure, and severe cardiac rhythm disturbances, up to atrial or ventricular fibrillation.
- Respiratory form. Acute respiratory failure comes to the forefront. Due to profound microcirculatory disruption, edema of the larynx, epiglottis, and lung tissue develops rapidly. Clinically, this manifests as dyspnea, pronounced cyanosis, moist rales in the lungs, and bubbling stridulous breathing.
- Cerebral form. Develops against the background of profound tissue hypoxia, total microcirculatory failure, and subsequent cerebral edema. The patient suffers from impaired consciousness (up to coma), accompanied by focal symptoms of central nervous system involvement.
Severity grades of the condition
The severity of anaphylactic shock is determined by the rate of symptom progression and the depth of hemodynamic disorders. Four degrees of severity are generally distinguished:
| Grade | Severity | Characteristic clinical manifestations |
|---|---|---|
| Grade I | Mild | Skin itching, rash, headache, dizziness, flushing of the face. |
| Grade II | Moderate | Symptoms of Grade I with the addition of angioedema, tachycardia, decreased blood pressure, and an elevated Allgower index. |
| Grade III | Severe | Loss of consciousness, acute cardiovascular and respiratory failure (dyspnea, cyanosis, stridulous breathing, thready rapid pulse, sharp drop in BP, high Allgower index). |
| Grade IV | Extremely severe | Profound loss of consciousness, critical cardiovascular failure (peripheral pulse is not palpable, blood pressure is extremely low). |
Principles of emergency therapy
The treatment of anaphylactic shock follows the general principles of anti-shock therapy. The main objective is the immediate restoration of systemic hemodynamics and capillary blood flow.
All medications are administered strictly intravenously:
- Vasoconstrictors: epinephrine (adrenaline), norepinephrine, or ephedrine are used to combat vasodilation.
- Normalization of BCC and microcirculation: administration of colloidal solutions, gelatin, and dextran with a medium molecular weight of 30,000–40,000 is indicated.
- Pharmacological prevention of antigen action: antihistamines (diphenhydramine, chloropyramine, promethazine), high-dose glucocorticoids (prednisolone, dexamethasone, hydrocortisone), and calcium preparations are used.
- Specific antigen inactivation: whenever possible, agents that destroy the allergen are used. For example, in shock caused by penicillin antibiotics, the administration of enzymes (penicillinase or beta-lactamase) is indicated.
Prevention of anaphylactic reactions
Preventing the development of anaphylaxis is a crucial task for the surgeon prior to performing any invasive procedures or prescribing pharmacotherapy. Prevention includes three mandatory stages:
- Taking an allergological history. It is necessary to thoroughly investigate any past allergic diseases in the patient.
- Caution when prescribing medications. The selection of drugs must be carried out with strict consideration of the medical history; potential drug allergens should be avoided.
- Performing sensitivity tests. In the case of an unfavorable allergic history, performing tests is strictly mandatory prior to the administration of antibiotics, chemical antiseptics, and iodine preparations (which is particularly relevant before contrast angiography).
Briefly: answers to topical questions
What dosages of epinephrine (adrenaline) should be administered in the emergency treatment of anaphylactic shock?
In the emergency treatment of anaphylactic shock, epinephrine (adrenaline) should be administered subcutaneously at a dose of 0.5 ml of a 0.1% solution. This therapeutic volume contains 0.5 mg of the active substance. The drug belongs to the sympathomimetic group and is used to relieve acute allergic reactions accompanied by loss of consciousness and collapse.
What stages of pathogenesis underlie the development of anaphylactic shock?
The development of anaphylactic shock is based on three stages of the immediate-type allergic reaction (type I hypersensitivity).
- Immunological stage — the phase of immune reactions (sensitization), including the initial exposure to the antigen and the fixation of IgE on mast cells.
- Pathochemical stage — the phase of biochemical reactions upon re-exposure to the antigen, accompanied by degranulation and the release of mediators.
- Pathophysiological stage — the stage of clinical manifestations caused by the pharmacological effects of mediators on blood vessels and airways.
How is the Allgower index, which increases in grades II and III of shock severity, calculated?
The Allgower index is calculated as the ratio of the pulse rate to the systolic blood pressure. Calculation formula: Index = Pulse (bpm) / SBP (mmHg). The indicator is based on the feedback of circulatory parameters during shock: as the condition worsens, the pulse rate increases while systolic blood pressure decreases. The normal index is 0.5. A value of 1.0 indicates the transition to pronounced shock, and 1.5 or higher indicates developed severe shock.
For quick memorization of the key areas of shock therapy: "Three C's" — Circulation/Vessels (epinephrine), Cardiac/BCC (colloids), Specific blockade (glucocorticoids, antihistamines, and antigen inactivators).
Class and exam questions
Which solutions are optimal for restoring BCC in anaphylaxis?
To normalize circulating blood volume and microcirculation, colloidal solutions, gelatin preparations, and dextran (average molecular weight 30,000–40,000) are used.
Which drugs are administered for antigen inactivation in case of antibiotic allergy?
In the event of anaphylactic shock in response to antibiotic administration, specific enzymes that destroy the drug are used, such as penicillinase or beta-lactamase.
What is included in pharmacotherapy to prevent the action of the antigen?
The patient is administered intravenous antihistamines (diphenhydramine, chloropyramine, promethazine), calcium preparations, and high doses of glucocorticoids (dexamethasone, prednisolone, hydrocortisone).
What else to study on this topic
- Methodology and rules for calculating the Allgower index to assess shock severity
- Algorithms for performing skin sensitivity tests to antibiotics and iodine
- Mechanism of action of dextrans and colloidal solutions on capillary blood flow
- Differential diagnosis of the cerebral form of anaphylaxis and primary CNS lesions
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