Vascular resistance and transit time of sickle red blood cells

Changes in vascular resistance and mean transit time caused by the introduction either normal or sickled red blood cells (SSRBC) into the circulation were measured in the coronary and mesenteric vascular beds. The cat mesentery was perfused at constant flow through the superior mesenteric artery with a Ringer solution containing albumin. A rise in input pressure was observed after introducing RBC's. (10% hematocrit) at a constant rate, into the perfusate. The pressure rise caused by SSRBC's relative to that caused by normal RBC's represents the relative change in vascular resistance caused by the former cells as the perfusion flow was the same for both infusions. Similar measurements were performed in Ringer's perfused rabbit hearts in vitro. SSRBC's produced a 2 +/- 0.12 (M +/- SE) times relative increase in resistance in the mesentery and a 4 +/- 0.5 times increase in the coronary vasculature. Mean transit time, t was measured by monitoring the light transmission change caused by the injection of a small amount of RBC's into the arterial side of a Ringer's perfused rabbit heart. For normal RBC's t was 3.67 +/- 0.08 s and it rose to 6.1 +/- 0.6 s when SSRBC's were used. The simultaneous measurement of both mean transit time and pressure rise may help to identify the cell changes that cause circulatory impairment is SS cell anemia patients and it may also provide a convenient index to relate with the severity of the crisis.