Effects of delaying fluid resuscitation on an injury to the systemic arterial vasculature.

OBJECTIVES: To determine the effects of delaying fluid on the rate of hemorrhage and hemodynamic parameters in an injury involving the arterial system.

METHODS: Twenty-one adult, anesthetized sheep underwent left anterior thoracotomy and transection of the left internal mammary artery. A chest tube was inserted into the thoracic cavity to provide a continuous measurement of blood loss. The animals were randomly assigned to one of three resuscitation protocols: 1) no fluid resuscitation (NR), 2) standard fluid resuscitation (SR) begun 15 minutes after injury, or 3) delayed fluid resuscitation (DR) begun 30 minutes after injury. All of the animals in the two resuscitation groups received 60 mL/kg of lactated Ringer's solution over 30 minutes. Blood loss and hemodynamic parameters were measured throughout the experiment.

RESULTS: Total hemorrhage volume (mean +/- SD) at the end of the experiment was significantly lower (p = 0.006) in the NR group (1,499 +/- 311 mL) than in the SR group (3,435 +/- 721 mL) or the DR group (2,839 +/- 1549 mL). Rate of hemorrhage followed changes in mean arterial pressure in all groups. Hemorrhage spontaneously ceased significantly sooner (p = 0.007) in the NR group (21 +/- 14 minutes) and the DR group (20 +/- 15 minutes) than in the SR group (54 +/- 4 minutes). In the DR group, after initial cessation of hemorrhage, hemorrhage recurred in five of six animals (83%) with initiation of fluid resuscitation. Maximum oxygen (O2) delivery in each group after injury was as follows: 101 +/- 34 mL O2/kg/min at 45 minutes in the DR group, 51 +/- 20 mL O2/kg/min at 30 minutes in the SR group, and 35 +/- 8 mL O2/kg/min at 60 minutes in the NR group.

CONCLUSIONS: Rates of hemorrhage from an arterial injury are related to changes in mean arterial pressure. In this animal model, early aggressive fluid resuscitation in penetrating thoracic trauma exacerbates total hemorrhage volume. Despite resumption of hemorrhage from the site of injury, delaying fluid resuscitation results in the best hemodynamic parameters.