The purposes of this study are to quantify the use of nitroglycerin (NTG) in prehospital care, to detect deviations from the Standing Medical Orders (SMO), to determin the effectiveness of its administration, and the incidence of clinically significant adverse reactions (hypotension, bradycardia).

Retrospective review of 7683 Advanced Life Support (ALS) telemetry, base-station contacts over a three month period (June, July, Auguest 1990) to identify all prehospital patient contacts in which NTG was utilized.

The Resource Hospital/Telemetry Base-Station a two community hospitals/Telemetry Base-Stations for the Chicago North EMS System.

There were 445 runs in which NTG was indicated as per SMO. Two hundred eighty-eight patients (64.7%) received NTG for appropriate indications as per SMO, 203 for ischemic chest pain (45.6%), 79 for pulmonary edema (17.7%), and six for both (1.3%). There were 157 (35.5%) runs in which NTG was indicated, but not administered. There were 22 patients who received NTG for indications that deviated from the SMO. Reassessment data concerning the subjective symptom was completed on 118 patients (40.9%), 92 (45.3%) patients with chest pain and 26 with dyspnea (32.9%). Following the administration of NTG, 21 patients (10.1%) with chest pain were unchanged, while 13 with dyspnea (15.3%) improved, 13 patients (15.3%) were unchanged, and none worsened. In 121 patients, the systolic blood pressure (SBP) decreased, while 24 were unchanged (5.4%), and 28 had an increase (6.3%). The mean initial value SBP was 176±44 mmHg and the repeat mean SBP was 164±41 mmHg with a mean decrease of 12±22 mmHg. The diastolic blood pressure (DBP) decreased in 87 patients, was unchanged in 53 (11.9%), and increased in 33 (7.4%). The initial mean DBP was 97±24 mmHg, the repeat mean DBP was 92±23 mmHg, a mean decrease of 5±15 mmHg. Only one patient became hypotensive with the administration of NTG and was successfully resusticated with a fluid bolus of 300 ml normal saline.

In this EMS system, NTG is under-utilized based on the indications delineated by this system's SMOs. Reassessment is documented infrequently, but when completed, clinically significant adverse reactions are rare. Since the incidence of hypotension and bradycardia are rare, the inability to establish an IV line should not preclude the administration of NTG.