Permissive hypotension and desmopressin enhance clot formation

Experimental studies of uncontrolled hemorrhage demonstrated that permissive hypotension (PH) reduces blood loss, but its effect on clot formation remains unexplored. Desmopressin (DDAVP) enhances platelet adhesion promoting stronger clots. We hypothesized PH and DDAVP have additive effects and reduce bleeding in uncontrolled hemorrhage.

Rabbits (n = 42) randomized as follows: sham; normal blood pressure (NBP) resuscitation; PH resuscitation-60% baseline mean arterial pressure; NBP plus DDAVP 1 hour before (DDAVP NBP) or 15 minutes after beginning of shock (DDAVP T1 NBP); and PH plus DDAVP 1 hour before (DDAVP PH) or 15 minutes after beginning of shock (DDAVP T1 PH). Fluid resuscitation started 15 minutes after aortic injury and ended at 85 minutes. Intraabdominal blood loss was calculated, aortic clot sent for electron microscopy. Activated partial thromboplastin time, platelet count, thromboelastometry, arterial blood gases, and complete blood count were performed at baseline and 85 minutes. Analysis of variance was used for comparison.

NBP received more fluid volume and had greater intraabdominal blood loss. DDAVP, when administered preshock, significantly reduced blood loss in NBP and fluid requirement when given postshock. Platelets, arterial blood gas, complete blood count, and activated partial thromboplastin time were similar at 85 minutes. NBP delayed clot formation and worsened thrombodynamic potential on thromboelastometry, whereas PH and DDAVP improved. Electron microscopy showed lack of fibrin on NBP clots, whereas DDAVP and PH clots displayed exuberant fibrin/platelet aggregates. DDAVP NBP presented intermediate clots.

PH reduced bleeding and improved hemostasis compared with normotensive resuscitation. DDAVP given preshock exerted similar effects with normotensive resuscitation.