PANIC RESPONSE TO SODIUM LACTATE INFUSION IN PATIENTS WITH MULTIPLE CHEMICAL-SENSITIVITY SYNDROME

Background: Many patients who are first seen with what has been called multiple chemical sensitivity syndrome (RIGS) experience symptoms sug gestive of panic disorder including chest tightness, shortness of brea th, palpitations, paresthesias, lightheadedness, and mental confusion, Although such patients are often convinced that these symptoms reflec t toxic effects of environmental ''chemicals;'' direct evidence of thi s is lacking. To the contrary, a previous study has shown that some of these individuals exhibit hyperventilation responses on exposure to n onnoxious stimuli, and it has been suggested that the resulting bypoca rbia accounts for their symptoms, We postulated that some patients wit h self-identified MCS had an underlying condition similar to panic dis order and would therefore demonstrate similar responses to provocative challenges, such as sodium lactate infusion. Methods: Patients referr ed to an allergy and clinical immunology service for evaluation of ''c hemical sensitivity'' mere investigated to rule out underlying medical conditions, including asthma, as a cause of their symptoms and we wer e enrolled for study after giving informed consent. After a standardiz ed psychiatric assessment was performed, patients underwent single-bli nd intravenous infusions of normal saline solution (placebo) and sodiu m lactate (which reproduces symptoms in individuals with underlying pa nic disorder), All patients mere referred for independent psychiatric assessment. Results: The standardized psychiatric assessment identifie d four of five patients as meeting DSM III-R diagnostic criteria for p anic disorder along with other depressive and/or anxiety-related disor ders, All five patients with self-identified chemical sensitivity exhi bited a positive symptomatic response to sodium lactate compared with placebo infusion, Independent psychiatric assessment confirmed the dia gnosis of panic disorder on the basis of DSM III-R criteria in each of the five patients, Conclusions: These results suggest that MCS may ha ve a neurobiologic basis similar, if not identical, to that of panic d isorder, We speculate that treatments with demonstrated efficacy in pa nic disorder may also be of benefit in MCS, and conversely, treatments that reinforce anticipatory anxiety and avoidance behavior in patient s with MCS may be detrimental.