Hemodynamic Effects of Methamphetamine and General Anesthesia

DESIGN: A retrospective analysis of all anesthetic records at our institution over a two-year period was performed. Setting. Operating room cases under balanced anesthesia. Patients. All patients with ASA class I or II, who did not have trauma or were initially admitted to ICU, aged 18–65, without preexisting cardiac, renal, or pulmonary disease. Patients were divided into three groups: those acutely positive for methamphetamine within 48 hours of surgery (n = 137), those positive for methamphetamine between 48 hours and 7 days of surgery (n = 69), and randomly selected controls who were negative for methamphetamine within 7 days of surgery (n = 159). Measurements. Intraoperative hemodynamic instability was defined as either a drop of more than 40% in MAP for greater than 5 minutes or requirement for significant amount of vasopressors. Main Results. Among the patients who were acutely positive for methamphetamine within 24 hours, 31.4% met the criteria for hemodynamic instability within the first hour of general anesthesia, compared to 26.1% of the subacutely positive patients and 6.3% of controls (p < 0.0001). This was despite lower doses of anesthetic medications in the acutely and subacutely positive groups. CONCLUSION: Patients who present to the operating room with a positive urine drug screen for amphetamines within 2 days of surgery are at increased risk of hemodynamic instability. Postponing surgery up to 7 days somewhat decreases this risk, but not to the levels of patients who do not use methamphetamines.