Barry Gelman

An Analysis of the Association between Serum Citrulline and Acute Rejection among 26 Recipients of Intestinal Transplant

Small preliminary studies suggest that serum citrulline levels may act as a marker for acute cellular rejection in small intestinal transplant recipients. The results comparing serum citrulline concentrations with biopsy‐based grades of rejection are summarized here for an expanded group of 26 isolated intestinal and multivisceral transplant recipients. Other factors considered included patient and donor age and sex, ischemia time, serum creatinine, and type of transplant. Straight‐line fits reasonably described how each patients citrulline levels changed over time. Among 21 patients who demonstrated increasing citrulline levels over time, the estimated median time‐to‐achieve normal citrulline (≥30 μmol/L) was 79 days post‐transplant. Using stepwise linear regression, two characteristics were associated with a significantly higher maximum grade of rejection after 14 d post‐transplant: longer time‐to‐achieve normal citrulline (using ranks, p < 0.00001) and the patient not receiving a multivisceral transplant (p = 0.0005). Only the latter characteristic was significantly associated with maximum grade of rejection during the first 14 d post‐transplant (p = 0.01). Clearly, time‐to‐normalization of citrulline was delayed by the incidence of rejection, and in some cases with moderate‐to‐severe rejection, normalization of citrulline levels never occurred. We plan to further examine the use of citrulline as a marker for rejection in larger prospective studies.

Selective brain cooling in infant piglets after cardiac arrest and resuscitation

OBJECTIVES To test the hypothesis that selective brain cooling could be performed in an infant model of cardiac arrest and resuscitation without changing core temperature and to study its acute effects on regional organ blood flow, cerebral metabolism, and systemic hemodynamics. DESIGN Prospective, randomized, controlled study. SETTING Research laboratory at a university medical center. SUBJECTS Fourteen healthy infant piglets, weighing 3.5 to 6.0 kg. INTERVENTIONS piglets were anesthetized and mechanically ventilated, and had vascular catheters placed. Parietal cortex (superficial brain), caudate nucleus (deep brain), esophageal, and rectal temperatures were monitored. All animals underwent 6 mins of cardiac arrest induced by ventricular fibrillation, 6 mins of external cardiopulmonary resuscitation (CPR), defibrillation, and 2 hrs of reperfusion. Normal core temperature (rectal) was regulated in all animals. In seven control animals (group 1), brain temperature was not manipulated. In seven experimental animals (group 2), selective brain cooling was begin during CPR, using a cooling cap filled with -30 degrees C solution. Selective brain cooling was continued for 45 mins of reperfusion after which passive rewarming was allowed. Regional blood flow (microspheres) and arterial and sagittal sinus blood gases were measured prearrest, during CPR, and at 10 mins, 45 mins, and 2 hrs of reperfusion. MEASUREMENTS AND MAIN RESULTS Rectal temperature did not change over time in either group. In group 1, brain temperature remained constant except for a decrease of 0.6 degrees C at 10 mins of reperfusion. In group 2, superficial and deep brain temperatures were lowered to 32.8 +/- 0.7 (SEM) degrees C and 34.9 +/- 0.4 degrees C, respectively, by 15 mins of reperfusion. Superficial and deep brain temperatures were further lowered to 27.8 +/- 0.8 degrees C and 31.1 +/- 0.3 degrees C, respectively, at 45 mins of reperfusion. Both temperatures returned to baseline by 120 mins. Cerebral blood flow was not different between groups at any time point, although there was a trend for higher flow in group 2 at 10 mins of reperfusion (314% of baseline) compared with group 1 (230% of baseline). Cerebral oxygen uptake was lower in group 2 than in group 1 (69% vs. 44% of baseline, p=.02) at 45 mins of reperfusion. During CPR, aortic diastolic pressure was lower in group 2 than in group 1 (27 +/- 1 vs. 23 +/- 1 mm Hg, p = .007). Myocardial blood flow during CPR was also lower in group 2 (80 +/- 7 vs. 43 +/- 7 mL/min/100 g, p=.002). Kidney and intestinal blood flows were reduced during CPR in both groups; however, group 2 animals also had lower intestinal flow vs. group 1 at 45 and 120 mins of reperfusion. CONCLUSIONS Selective brain cooling by surface cooling can be achieved rapidly in an infant animal model of cardiac arrest and resuscitation without changing core temperature. Brain temperatures known to improve neurologic outcome can be achieved by this technique with minimal adverse effects. Because of its ease of application, selective brain cooling may prove to be an effective, inexpensive method of cerebral resuscitation during pediatric CPR.

Early endothelial damage and leukocyte accumulation in piglet brains following cardiac arrest

This study examined the early microvascular and neuronal consequences of cardiac arrest and resuscitation in piglets. We hypothesized that early morphological changes occur after cardiac arrest and reperfusion, and that these findings are partly caused by post-resuscitation hypertension. Three groups of normothermic piglets (37.5°–38.5°C) were investigated: group 1, non-ischemic time controls; group 2, piglets undergoing 8 min of cardiac arrest by ventricular fibrillation, 6 min of cardiopulmonary resuscitation (CPR) and 4 h of reperfusion; and group 3, non-ischemic hypertensive controls, receiving 6 min of CPR after only 10 s of cardiac arrest followed by 4-h survival. Immediately following resuscitation, acute hypertension occurred with peak systolic pressure equal to 197 ±15 mm Hg usually lasting less than 10 min. In reacted vibratome sections, isolated foci of extravasated horseradish peroxidase were noted throughout the brain within surface cortical layers and around penetrating vessels in group 2. Stained plastic sections of leaky sites demonstrated variable degrees of tissue injury. While many sections were unremarkable except for luminal red blood cells and leukocytes, other specimens contained abnormal neurons, some appearing irreversibly injured. The number of vessels containing leukocytes was higher in group 2 than in controls (3.8±0.6% vs 1.4±0.4% of vessels, P<0.05). Evidence for irreversible neuronal injury was only seen in group 2. Endothelial vacuolization was higher in groups 2 and 3 than in group 1 (P<0.05). Ultrastructural examination of leaky sites identified mononuclear and polymorphonuclear leukocytes adhering to the endothelium of venules and capillaries only in group 2. The early appearance of luminal leukocytes in ischemic animals indicates that these cells may contribute to the genesis of ischemia reperfusion injury in this model. In both groups 2 and 3 endothelial cells demonstrated vacuolation and luminal discontinuities with evidence of perivascular astrocytic swelling. Widespread microvascular and neuronal damage is present as early as 4 h after cardiac arrest in infant piglets. Hypertension appears to play a role in the production of some of the endothelial changes.

Hemodynamic effects of nitric oxide synthase inhibition before and after cardiac arrest in infant piglets

Using infant piglets, we studied the effects of nonspecific inhibition of nitric oxide (NO) synthase by N G-nitro-l-arginine methyl ester (l-NAME; 3 mg/kg) on vascular pressures, regional blood flow, and cerebral metabolism before 8 min of cardiac arrest, during 6 min of cardiopulmonary resuscitation (CPR), and at 10 and 60 min of reperfusion. We tested the hypotheses that nonspecific NO synthase inhibition 1) will attenuate early postreperfusion hyperemia while still allowing for successful resuscitation after cardiac arrest, 2) will allow for normalization of blood flow to the kidneys and intestines after cardiac arrest, and 3) will maintain cerebral metabolism in the face of altered cerebral blood flow after reperfusion. Before cardiac arrest, l-NAME increased vascular pressures and cardiac output and decreased blood flow to brain (by 18%), heart (by 36%), kidney (by 46%), and intestine (by 52%) compared with placebo. During CPR, myocardial flow was maintained in all groups to successfully resuscitate 24 of 28 animals [ P value not significant (NS)]. Significantly,l-NAME attenuated postresuscitation hyperemia in cerebellum, diencephalon, anterior cerebral, and anterior-middle watershed cortical brain regions and to the heart. Likewise, cerebral metabolic rates of glucose (CMRGluc) and of lactate production (CMRLac) were not elevated at 10 min of reperfusion. These cerebral blood flow and metabolic effects were reversed byl-arginine. Flows returned to baseline levels by 60 min of reperfusion. Kidney and intestinal flow, however, remained depressed throughout reperfusion in all three groups. Thus nonspecific inhibition of NO synthase did not adversely affect the rate of resuscitation from cardiac arrest while attenuating cerebral and myocardial hyperemia. Even though CMRGluc and CMRLac early after resuscitation were decreased, they were maintained at baseline levels. This may be clinically advantageous in protecting the brain and heart from the damaging effects of hyperemia, such as blood-brain barrier disruption.Using infant piglets, we studied the effects of nonspecific inhibition of nitric oxide (NO) synthase by NG-nitro-L-arginine methyl ester (L-NAME; 3 mg/kg) on vascular pressures, regional blood flow, and cerebral metabolism before 8 min of cardiac arrest, during 6 min of cardiopulmonary resuscitation (CPR), and at 10 and 60 min of reperfusion. We tested the hypotheses that nonspecific NO synthase inhibition 1) will attenuate early postreperfusion hyperemia while still allowing for successful resuscitation after cardiac arrest, 2) will allow for normalization of blood flow to the kidneys and intestines after cardiac arrest, and 3) will maintain cerebral metabolism in the face of altered cerebral blood flow after reperfusion. Before cardiac arrest, L-NAME increased vascular pressures and cardiac output and decreased blood flow to brain (by 18%), heart (by 36%), kidney (by 46%), and intestine (by 52%) compared with placebo. During CPR, myocardial flow was maintained in all groups to successfully resuscitate 24 of 28 animals [P value not significant (NS)]. Significantly, L-NAME attenuated postresuscitation hyperemia in cerebellum, diencephalon, anterior cerebral, and anterior-middle watershed cortical brain regions and to the heart. Likewise, cerebral metabolic rates of glucose (CMRGluc) and of lactate production (CMRLac) were not elevated at 10 min of reperfusion. These cerebral blood flow and metabolic effects were reversed by L-arginine. Flows returned to baseline levels by 60 min of reperfusion. Kidney and intestinal flow, however, remained depressed throughout reperfusion in all three groups. Thus nonspecific inhibition of NO synthase did not adversely affect the rate of resuscitation from cardiac arrest while attenuating cerebral and myocardial hyperemia. Even though CMRGluc and CMRLac early after resuscitation were decreased, they were maintained at baseline levels. This may be clinically advantageous in protecting the brain and heart from the damaging effects of hyperemia, such as blood-brain barrier disruption.

Analysis of vascular access in intestinal transplant recipients using the Miami classification from the VIIIth International Small Bowel Transplant Symposium.

Background. Loss of vascular access in patients with intestinal failure is considered an indication for intestinal transplantation. Such patients often have one or more occluded vein sites. Venous access could be classified according to the number of occluded vessels, to facilitate pre- and postoperative management. Methods. At the VIIIth International Small Bowel Transplant Symposium in September 2003, a new classification of vascular access in patients who were candidates for bowel transplant was proposed. The classification was then applied to stratify all patients that underwent intestinal transplantation at the University of Miami between 1998 and 2003. Data were collected on Doppler ultrasonography, angiography, and vein angioplasty in such patients. Results. A total of 106 cases in 91 patients were included in the study. Based on Doppler ultrasound results, 51.9% of patients fell into class I (no thrombosed vessels), 21.7% were in class II (one occluded vessel, or positive risk factors for thrombosis), 24.5% were in class III (multiple thrombosed vessels), and 1.9% were in class IV (all vessels thrombosed). Fifteen percent of the patients required preoperative angiography to better evaluate venous access. Most of the patients that required angiography were in class III or IV, and 53.3% of patients requiring angiography needed additional venous angioplasty to achieve access. Conclusions. All patients that are referred for intestinal transplantation should undergo preliminary mapping of their venous access by Doppler ultrasound and then be assigned to a vascular access class. Those patients with multiple thrombosed vessels (class III and above) should be strongly considered for additional angiographic evaluation.

Cerebral blood flow during partial liquid ventilation in surfactant-deficient lungs under varying ventilation strategies.

Objective To test the hypothesis that cerebral and other regional organ blood flow would be maintained during partial liquid ventilation (PLV) in an animal model of acute lung injury during different ventilation strategies. Design A prospective, randomized study. Setting Animal research facility. Subjects Sixteen piglets, 2 to 4 wks of age. Interventions Severe lung injury was induced in infant piglets by repeated saline lavage and high tidal volume ventilation. Animals were then randomized to either conventional volume controlled ventilation or PLV. Measurements and Main Results Organ blood flow was determined in both groups using radiolabeled microspheres under four conditions: high mean airway pressure, P―aw; high Paco2, high P―aw; normal Paco2; low P―aw, high Paco2; low P―aw, normal Paco2. There were no differences in cerebral blood flow during conventional ventilation and PLV, regardless of ventilation strategy. Conclusions These results suggest in an acute lung injury model, PLV does not affect cerebral blood flow or other regional organ blood flow over a range of airway pressures.