MEASUREMENT OF CIRCULATING BLOOD-VOLUME IN-VIVO AFTER TRAUMA-HEMORRHAGE AND HEMODILUTION

Measurement of circulating blood volume in vivo after trauma-hemorrhag e and hemodilution. Am. J. Physiol. 266 (Regulatory Integrative Comp. Physiol. 35): R368-R374, 1994. - Although cardiac output (CO) and othe r hemodynamic variables are used to assess the adequacy of fluid resus citation after hemorrhage, it is not known whether there is any correl ation between restoration of CO and circulating blood volume (CBV). To determine this, rats underwent a midline laparotomy (i.e., trauma ind uced) and were bled to and maintained at a mean arterial pressure of 4 0 mmHg until 40% of maximum bleedout volume was returned in the form o f Ringer lactate (RL). The animals were then resuscitated with four or five times the volume of maximum bleedout in the form of RL. CO and h epatocellular function were measured using an in vivo hemoreflectomete r. CBV was monitored by using in vivo indocyanine green clearance. A g ood correlation between the values of blood volume obtained by this me thod and the I-125-albumin method indicates that the indocyanine green method is also a reliable technique for measuring CBV. Results indica te that resuscitation after hemorrhage improved the decreased CBV but did not restore it to control levels despite the fact that CO was rest ored and central venous pressure was more than doubled. A good correla tion between depressed CBV and hepatocellular dysfunction was also obs erved under such conditions. Thus measurement of CBV appears to be use ful for evaluating the adequacy of fluid resuscitation after trauma-he morrhage and hemodilution.