Intradermal compared with prick testing in the diagnosis of anaesthetic allergy.

We have tested the hypothesis that intradermal testing is a more effective method for determining the drug responsible for anaesthetic anaphylactic reactions than prick testing in 212 consecutive patients, aged more than 10 yr, referred to an anaesthetic allergy clinic over a 4-yr period. The study was a prospective, non-randomized design. Intradermal testing was conducted using a previously described method and diluted drugs, and prick testing using undiluted drugs (with the exception of opioid analgesics which were diluted 1:10). The tests were performed on individual patients' forearms on the same occasion. Patients were followed-up to determine the results of subsequent anaesthesia and the difference between tests was analysed using kappa and tau statistics. There was 93% agreement overall between the paired tests. Which test detected the drug responsible was dependent on diagnostic criteria for positivity. The differences between the tests were not statistically significant. Using both tests improved predictability by 67% (tau = 0.67, P < 0.001). We conclude that in the absence of data to support one test being superior, other factors influence the choice of test. Prick testing was cheaper, and the reduction in pain and trauma with prick testing makes it more suitable for children. However, there are no data available on the safety of subsequent anaesthesia based on the results of prick testing alone, and reliability with time has not been assessed. Intradermal testing may be easier for the infrequent user. Skin testing is valuable in the investigation of anaesthetic anaphylaxis whichever test is chosen. When there is doubt both tests should be performed.

Type B lactic acidosis following cardiopulmonary bypass.

OBJECTIVE: To describe, characterize, and identify the associations of postcardiac surgical lactic acidosis occurring in the absence of clinical evidence of tissue hypoperfusion. DESIGN: The preliminary study is a report of a series of observations in 12 patients. The prospective study is also observational, involving the structured collection of hemodynamic and metabolic variables in a prescribed series of patients. SETTING: Cardiac surgical intensive care unit of a university teaching hospital. PATIENTS: Twelve patients who developed an unexplained lactic acidosis after cardiac surgery are reported in the preliminary study. The prospective study involved observations in 112 consecutive patients undergoing cardiopulmonary bypass for cardiac surgery. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Preliminary study: Cardiac index was increased before, during and after recovery from lactic acidosis. Recovery from lactic acidosis was associated with a decrease in oxygen transport index and significant increases in oxygen consumption index and oxygen extraction ratio. PROSPECTIVE STUDY: Hemodynamic, oxygen transport, and oxygen consumption variables, together with arterial blood gas and lactate concentrations, were assessed every 6 hrs for 24 hrs after surgery. Sixteen patients developed lactic acidosis (peak lactate concentration > 5.0 mmol/L). Compared with the remainder of the patients, this subgroup had longer duration of cardiopulmonary bypass (116 +/- 31 vs. 76 +/- 31 mins, p < .01), greater intraoperative hypothermia (24.9 +/- 2.0 degrees vs. 26.6 +/- 2.3 degrees C, p < .01), more frequent requirement for vasopressor agents (14/16 vs. 35/96, p < .05) and a higher frequency of hyperglycemia (15/16 vs. 28/96, p < .01). Hemodynamic variables, including cardiac index, were remarkably similar in the acidotic and nonacidotic groups. All of the acidotic patients, in both parts of this study, recovered from their acidosis. Eleven of the patients in the preliminary study and all of the 16 acidotic patients in the prospective study were ultimately discharged from the hospital. CONCLUSIONS: This report documents the occurrence of lactic acidosis in a subgroup of patients undergoing cardiopulmonary bypass. The pathogenesis of this disorder is uncertain, but it appears to not relate to inadequate oxygen delivery. Systemic vasodilation and reduced oxygen extraction appear to be features of this disorder, which has an excellent prognosis.

Alleged allergy to local anaesthetics.

The aim of this study was to determine the incidence of true local anaesthetic allergy in patients with an alleged history of local anaesthetic allergy and whether subsequent exposure to local anaesthetics is safe. Two hundred and eight patients with a history of allergy to local anaesthesia were referred over a twenty-year period to our Anaesthetic Allergy Clinic. In this open study, intradermal testing was performed in three patients and progressive challenge in 202 patients. Four patients had immediate allergy and four patients delayed allergic reactions. One hundred and ninety-seven patients were not allergic to local anaesthetics. In 39 patients an adverse response to additives in local anaesthetic solutions could not be excluded. In all but one patient local anaesthesia has been given uneventfully subsequently. A history of allergy to local anaesthesia is unlikely to be genuine and local anaesthetic allergy is rare. In most instances LA allergy can be excluded from the history and the safety of LA verified by progressive challenge.

External chest compression in acute asthma: a preliminary study.

The technique of external chest compression to assist expiration has been used in asthmatic patients for some years, but it has not been described in detail in the medical literature. We describe a method for assisted expiration and its apparent value in the emergency treatment of asthma. The technique requires further evaluation to determine its role in the resuscitation of asthmatics.

Urban envenomation.

Over a 12-year period, 61 patients were admitted to a metropolitan hospital on 67 occasions with envenomation from snakes, spiders, ticks or bees. We describe the epidemiology of the bites and the patient's response to treatment. First aid was used in only 50% of patients with potentially-lethal bites. All patients who developed severe envenomation showed symptoms within 30 minutes, and all patients survived.

Can clinical anaphylaxis to anaesthetic drugs be predicted from allergic history?

The incidence of a history of allergy, atopy or asthma is greater in patients who undergo life-threatening clinical anaphylaxis to anaesthetic drugs. However, because the incidence is low, the presence of such a history is not a reliable predictor of the likelihood of a reaction in an individual patient, and does not indicate that the patient should be investigated or pretreated, or that the selection of drug(s) be altered to reduce the likelihood of a reaction.