Failure of nitroglycerin (glyceryl trinitrate) to improve villi hypoperfusion in endotoxaemic shock in sheep.

OBJECTIVE

To evaluate the effects of nitroglycerin (glyceryl trinitrate) on intestinal microcirculation during endotoxaemic shock.

DESIGN

Controlled experimental study.

SETTING

Research laboratory.

SUBJECTS

20 anaesthetised, mechanically ventilated sheep.

INTERVENTIONS

Septic shock was induced by endotoxin infusion. After 60 minutes without resuscitation, sheep received fluid resuscitation and were randomised to control or nitroglycerin groups. Nitroglycerin was infused at a rate of 0.2 µg/kg/min for 90 minutes.

MAIN OUTCOME MEASURE

Improved villi microcirculation.

RESULTS

Endotoxin lowered arterial blood pressure, cardiac output and intestinal blood flow, which were improved by fluid resuscitation. Mean (SD) ileal intramucosal-arterial PCO2 gradient increased during shock and remained elevated after resuscitation in control and nitroglycerin groups (8 [8], 15 [9] and 17 [9], and 6 [6], 13 [11] and 14 [9]mmHg, respectively; P < 0.05, baseline v shock and resuscitation for both groups). Villi microvascular flow index was reduced during shock and remained lower than baseline after the resuscitation in both groups (3.0 [0.0], 2.5 [0.2] and 2.7 [0.2], and 3.0 [0.0], 2.3 [0.3] and 2.6 [0.3], respectively; P < 0.05, baseline v shock and resuscitation for both groups). The red blood cell velocity behaved similarly (859 [443], 553 [236] and 670 [276], and 886 [440], 447 [124] and 606 [235] µm/s, respectively; P < 0.05, baseline v shock and resuscitation for both groups).

CONCLUSIONS

In endotoxaemic sheep, low doses of nitroglycerin failed to improve the subtle but persistent villi hypoperfusion that remains present after fluid resuscitation.