Symptoms essential to the experience of sodium lactate-induced panic

We report on subjective ratings and symptoms experienced before and during sodium lactate infusion by patients with panic disorder or agoraphobics with panic attack (DMS-III-R criteria). Symptoms were assessed using the Acute Panic Inventory (API). During the lactate infusion 59% of the patients were rated by an attending psychiatrist as having experienced lactate-induced panic attacks. Patients experiencing lactate-induced panic attacks overwhelmingly rated this experience as very similar to their typical naturally occurring attacks. Among the individual API symptoms items at baseline (prelactate) only Afraid in general (r = 0.26) was significantly, but not strongly, correlated with the panic response. Controlling for baseline symptom levels, the most robust partial correlations of symptomatic increment with panic were Desire to flee (0.70), Fear of losing control (0.57), Afraid in general (0.49), and Dyspnea (0.48). Using a dichotomized symptom increment greater than 1, 13 of 29 API items indicated a panic response to lactate infusion; the best were Dyspnea, Feeling confused, Afraid in general, Difficulty speaking, Difficulty concentrating, Desire to flee, and Fear of losing control. A logistic regression analysis showed that among baseline measures, Afraid in general and Feeling confused significantly predicted panic. For dichotomized change scores, Afraid in general, Dyspnea, and Dizziness/lightheadedness significantly indicated panic. In these analyses three symptom items stand out as the most predictive and revealing of panic to lactate infusion: Afraid in general, Dyspnea, and Desire to flee. These results are discussed in the context of Klein's (1993) suffocation false alarm theory of panic.