Immunological and non-immunological mechanisms involved in adverse reactions to drugs

Mechanisms of activation of human mast cells and basophils by general anesthetic drugs

A study was performed about the effects of increasing concentrations of muscle relaxants (suxamethonium, d-tubocurarine, vecuronium, and atracurium), hypnotics (propofol, ketamine, and thiopental), opioids (morphine, buprenorphine, and fentanyl), and benzodiazepines (diazepam, flunitrazepam, and midazolam) on the release of preformed (histamine and tryptase) and de novo synthesized (prostaglandin D2: PGD2 and peptide-leukotriene C4: LTC4) chemical mediators from human basophils and mast cells isolated from skin (HSMC), lung parenchyma (HLMC) and heart tissue (HHMC). None of the drugs tested induced the release of histamine or LTC4 from basophils of normal donors. Suxamethonium did not induce mediator release from any type of human mast cell tested. Only the highest concentration of d-tubocurarine used caused histamine release from HSMC and HLMC. Atracurium, more than vecuronium, induced concentration-dependent histamine release from HSMC and HLMC. Propofol induced a concentration-dependent histamine release from HLMC, but not from HHMC. Only the highest concentrations of ketamine and thiopental used caused a significant release of histamine from HLMC. The muscle relaxants and hypnotics examined did not induce any de novo synthesis of PGD2 or LTC4 in mast cells. Morphine only induced histamine and tryptase release from HSMC, but not the de novo synthesis of PGD2. In contrast, buprenorphine caused histamine and tryptase release from HLMC, and not from HSMC, whilst it also induced de novo synthesis of PGD2 and LTC4 in HLMC. Fentanyl did not give any histamine and tryptase release from mast cells. Diazepam and flunitrazepam only induced a small release of histamine from mast cells, whereas midazolam caused the release of histamine from HLMC. The biochemical pathways underlying the release of mediators from human mast cells induced by drugs used during general anaesthesia are different from those underlying the immune release of histamine. From the results obtained with the in vitro model described here, it is clear that new drugs promising for the anesthesiologic arena should be tested in vitro before their potential histamine-releasing activity is experienced in vivo.

Perioperative uses of histamine antagonists

Histamine release and adverse pseudoallergic/allergic reactions during the perioperative period occur frequently. The incidence of such reactions is 20%-30% for all grades of severity, 1%-5% for systemic reactions, and 0.1%-0.5% for life-threatening reactions. They can be elicited by all commonly used anesthetic agents and by surgical interventions. Both the incidence and severity can be reduced by the use of combined prophylaxis with H1- + H2-receptor antagonists. The authors recommend that this prophylaxis be given to the following groups of patients: those with a history of adverse reactions or history of allergy, patients undergoing surgery with a high risk of histamine release, elderly patients, and those with poor physical status due to underlying systemic diseases. These indications have been developed by heuristic medical decision-making, including a decision tree.

[Processes of perioperative risk from the viewpoint of the anesthesiologist]

Nearly all of the pharmaceutical preparations that are used for anesthesia can release histamine. H1 and H2 receptor blockades are recommended for the following groups of patients at risk: 1) Patients who show hypersensitivity to i.v. administered medications and radiological contrast media. 2) Patients with risk factors in their case histories, e.g., atopy, previous cardiac and/or pulmonary damage, and an age of over 70 years. 3) Conditions with a pathological increase in the plasma histamine level. Such conditions include (a) polytrauma, chronic kidney insufficiency, patients under radium irradiation treatment; (b) the exploration phase during a surgical procedure, more frequent blood transfusions, extracorporeal circulation, and Palacos implantation. 4) Chymopapain for chemonucleolysis.

Anaphylactoid reactions and histamine release do not occur after application of the opioid tramadol

After an i.v. application of 100 mg tramadol in 13 healthy volunteers no change in plasma histamine concentration could be detected,( systemic anaphylactoid reactions did not occur, cutaneous reactions were not rated as anaphylactoid since itching and erythema were seen only once after tramadol whereas erythema was also observed twice after saline, blood pressure and heart rate were only very slightly and transiently elevated without any abnormalities in ECG-readings and only side effects typical for opioid therapy were observed.

[Non-specific histamine liberation and propofol]

The variations in blood pressure, heart rate and plasma histamine levels were monitored for 10 min in 40 patients at risk of releasing histamine after they had been given 2.5 mg X kg-1 propofol in oil emulsion (n = 20) or 7 mg X kg-1 thiopentone (n = 20). The measurements were carried out before anaesthesia, and 1, 2, 3, 5, 7 and 10 min after injecting the drug. All the patients were premedicated with a specific anti-H1 antagonist only (terfenadine). Histamine was measured by radio-immunology (Immunotech). Two patients from the propofol group and three from the thiopentone group showed minor signs, that may have been linked to a release of histamine. Blood pressure fell in both groups by about 20% (p less than 0.001) within the first minute, becoming stable afterwards. The heart rate did not change significantly. Plasma histamine levels did not change in either group, nor in those patients who had presented a local erythema. Propofol did not seem to induce non-specific histamine release when injected over a period of 60 s in patients at risk of doing so.

[Drugs inhibiting complement activation]

Complement may be activated by anaesthetic agents as well as contrast media, and so could anaphylactoid reactions be induced. Efficient and harmless complement blocking agents were still lacking. The only agents actually used by anaesthetists were steroids and/or antifibrinolytic drugs. Other agents were not indicated in surgical patients because of their adverse effects and the impossibility of giving them by the intravenous route.