Although research has been conducted since the 1960s with combination infusion of glucose, insulin, and potassium in the setting of acute myocardial infarction, the question of effect on 30-day mortality remains unresolved. The Glucose-Insulin-Potassium Study (GIPS) was designed to address this question with a large, open-label, randomized, controlled clinical trial involving patients admitted with acute myocardial infarction to a single center for primary angioplasty.

The 940 patients enrolled in the study all had acute ST-segment elevation infarctions with symptom onset of 24 hours or less before admission. Major exclusion criteria were pretreatment with a thrombolytic agent or presence of an illness associated with lowered life expectancy. Baseline characteristics were similar for the infusion and control patients with the exception of a smaller proportion of men in the infusion group.

A specific regimen of high-dose, continuously infused glucose, insulin, and potassium was used for patients in the active treatment arm. The primary endpoint was 30-day mortality. The three secondary endpoints were a composite of 30-day mortality, recurrent infarction, or repeat revascularization procedure, high enzymatic infarct size, and left ventricular ejection fraction less than 30 percent.

Post-angioplasty results were similar for the two groups, with no significant differences observed. When the 30-day mortality data were analyzed, there was no significant difference between treatment arms. However, analysis of subgroups showed that mortality was significantly improved with infusion for patients admitted in Killip Class 1 status (relative risk 0.28) and for patients with diabetes (relative risk 0.31).

Composite endpoint was also improved with infusion for patients in Killip Class 1.

Data on infarct size according to serial enzyme levels was available for 622 of the 940 patients, and analysis showed that patients in the highest quartile of enzyme peak level were more likely to have an anterior infarction, be admitted in Killip Class 2, 3, or 4, and to have no TIMI 3 blood flow after angioplasty.

The risk for post-angioplasty ejection fraction of less than 30 percent was higher for patients who were older, had an anterior infarction, had high enzyme peak levels, and who were diabetic.

The primary conclusion of the study was the significant reduction in 30-day mortality and composite endpoint for patients admitted in Killip Class 1. Additional findings were an improvement with infusion in infarct size based on blood enzyme levels and in post-angioplasty left ventricular ejection fraction.

Although there seems to be a benefit of combination infusion therapy, especially for patients in Killip Class 1, conclusions are limited by lack of data for all patients. For instance, data on enzyme levels were incomplete (and thus omitted from analysis) for 318 patients, often due to in-hospital death or early transfer to another institution.