The effect of ibuprofen on endotoxin-induced injury in sheep

Decreased left ventricular contractility during porcine endotoxemia is not prevented by ibuprofen

OBJECTIVE

We investigated whether ibuprofen could prevent early decrease in left ventricular contractility that occurs during porcine endotoxemia.

DESIGN

Prospective, randomized, controlled animal study.

SETTING

University research laboratory.

SUBJECTS

Adolescent crossbred pigs (n = 28).

INTERVENTIONS

Anesthetized pigs were instrumented to measure hemodynamics and left ventricular pressures (using a Millar catheter) and volumes (using a conductance catheter). Pigs were then treated in four groups, according to pretreatment using ibuprofen (15 mg/kg) or saline and subsequent treatment using endotoxin (0111:B4, 50 microg/kg) or saline.

MEASUREMENTS AND MAIN RESULTS

Measurements of hemodynamics and left ventricular pressures and volumes were repeated after pretreatment with ibuprofen (or saline in controls), and at hourly intervals for 4 hrs after the start of endotoxin or control saline infusions. Left ventricular contractility was primarily assessed using the slope of the end-systolic pressure-volume relationship. Data were analyzed, using a repeated-measures analysis of variance. The slope of the end-systolic pressure-volume relationship was decreased at 4 hrs by 41 +/- 9% in the saline/endotoxin group (p < .05) and by 36 +/- 14% in the ibuprofen/endotoxin group (p < .05), so that ibuprofen pretreatment had no significant effect on the decrease in left ventricular contractility. Mean arterial pressure decreased in the saline/endotoxin group by 23 +/- 12% at 1 hr (p < .05) and by 35 +/- 12% (p < .05) at 4 hrs. Ibuprofen significantly reduced the decrease in mean arterial pressure (2 +/- 6% increased at 1 hr, and 17 +/- 12% decreased at 4 hrs, both p<.05 compared with saline/endotoxin). Cardiac output increased by 25% (p < .05) in the first hour, but then decreased to be slightly (NS) below baseline at 4 hrs in both endotoxin groups. Mean pulmonary arterial pressure was increased in the saline/endotoxin group by 154 +/- 52% (p < .05) at 30 mins and by 118 +/- 40% (p < .05) at 4 hrs. Ibuprofen prevented the very acute increase in pulmonary arterial pressure (increased by 11 +/- 33% at 30 mins, p < .05 compared with saline/endotoxin) and significantly reduced the pulmonary hypertension at 4 hrs (increased by 70 +/- 25%, p < .05 compared with both baseline and saline/endotoxin).

CONCLUSIONS

We conclude that products of the cyclooxygenase pathway do not play a major role in the early decrease in left ventricular contractility after endotoxin. However, ibuprofen may have a role in reducing the other cardiovascular effects of sepsis.

The role of cyclooxygenase products in lung injury induced by tumor necrosis factor in sheep

Tumor necrosis factor-alpha (TNF alpha) has been proposed as a mediator of endotoxin-induced lung injury. When given to sheep, TNF alpha mimics endotoxin (LPS) causing hypoxemia, pulmonary hypertension, leukopenia, reduced dynamic compliance (Cdyn), increased resistance to airflow (RL), exudation of lung lymph, and enhanced airway reactivity. TNF alpha also induces rapid release of thromboxane A2 (TxA2), prostaglandin E2 (PGE2), and prostacyclin (PGI2). We hypothesized that the inflammatory effects of TNF alpha are due at least in part to cyclooxygenase products, and therefore cyclooxygenase inhibition would have similar effects on TNF alpha-induced lung injury as has previously been demonstrated for LPS-induced lung damage. Using awake sheep with chronic lung lymph fistulas, we measured Cdyn, RL, and FRC using a whole-body plethysmograph. Pulmonary artery (Ppa), left atrial (PLA), and systemic arterial (Psa) pressures were recorded continuously. Arterial blood gases (for calculating AaPO2), leukocyte counts, and lymph samples (for prostanoid levels) were collected every 30 min. Eleven animals underwent paired random-order experiments receiving ibuprofen (14 mg/kg) 1 h before human recombinant TNF alpha (10 micrograms/kg), or an identical dose of TNF alpha alone. Within 15 min of initiating TNF alpha, Ppa doubled and remained elevated for 4 h. Ibuprofen prevented the early rise in Ppa after TNF alpha. In the group receiving TNF alpha alone, increases in Ppa were accompanied by a 60% decline in leukocyte count and a 50% increase in AaPo2 within 30 min. Ibuprofen prevented increases in AaPo2, but it had no effect on leukopenia or late increases in lymph flow.(ABSTRACT TRUNCATED AT 250 WORDS)