Charles L. Schleien

The effect of nitric oxide synthase inhibition on infarct volume after reversible focal cerebral ischemia in conscious rats.

Background and Purpose Previous in vitro and in vivo studies of the effects of nitric oxide synthase inhibition in the central nervous system have yielded conflicting results concerning the role of nitric oxide in the events that lead to ischemic injury. In this study, we tested the hypothesis that preischemic inhibition of nitric oxide synthase increases infarct volume after reversible focal cerebral ischemia in rats. Methods NG-nitro-L-arginine methyl ester hydrochloride 15 mg/kg IV or an equivalent volume of saline was administered to adult Wistar rats 15 minutes before middle cerebral artery occlusion by the intraluminal suture method. After 2 hours of ischemia, the suture was withdrawn, and rats were allowed to survive for 3 days. Areas of infarction in 10 hematoxylin-eosin-stained sections were measured and used to determine infarct volume. Results Administration of NG-nitro-L-arginine methyl ester hydrochloride increased hemispheric infarct volume by 137% over control (60.9±30.5 to 144.3±19.6 mm3, P<.05; mean±SEM). Cortical and subcortical infarct volumes were increased by 176% (33.8±21.9 to 93.3±15.2 mm3, P<.05) and 103% (25.1±9.4 to 51.0±5.5 mm3, P<.03), respectively. Conclusions Nitric oxide synthase inhibition increases infarct volume and decreases the variability of the response to middle cerebral artery occlusion in Wistar rats, a strain that is normally resistant to focal cerebral ischemic injury owing to extensive collateralization. The mechanism of the deleterious effect of nitric oxide synthase inhibition likely involves a more severe degree of blood flow reduction during and after middle cerebral artery occlusion, primarily by preventing the vasodilatory response of collateral vessels to proximal middle cerebral artery occlusion. Maintenance of nitric oxide synthase activity during and after focal cerebral ischemia appears to minimize ischemic injury.

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.

Portosystemic shunting in children during the era of endoscopic therapy : Improved postoperative growth parameters

BACKGROUND Surgical portosystemic shunting has been performed less frequently in recent years. In this retrospective study, recent outcomes of portosystemic shunting in children are described, to evaluate its role in the era of endoscopic therapy. METHODS Retrospective chart review of children who underwent surgical portosystemic shunt procedures between October 1994 and October 1997. RESULTS Twelve children (age range, 1-16 years) underwent shunting procedures. The causes of portal hypertension were extrahepatic portal vein thrombosis (n = 6), congenital hepatic fibrosis (n = 2), hepatic cirrhosis (n = 2), and other (n = 2). None of the patients were immediate candidates for liver transplantation. Types of shunt included: distal splenorenal (n = 10), portocaval (n = 1), and other (n = 1). Median follow-up was 35 months (range, 24-48 months). All patients are currently alive and well with patent shunts. The mean hospital stay was 8 days. Three patients required readmission for further interventions because of shunt stenosis in two and small bowel obstruction in the other. Mild portosystemic encephalopathy was seen in one child with pre-existing neurobehavioral disturbance. Excluding a patient who underwent placement of a portosystemic shunt for a complication of liver transplantation, mean weight-for-age z score in nine prepubertal patients improved from -1.16 SD to +0.15 SD (P = 0.023), and mean height-for-age z score from -1.23 SD to 0.00 SD (P = 0.048) by 2 years after surgery. CONCLUSIONS Surgical portosystemic shunting is a safe and effective method for the management of portal hypertension in childhood. Patients show significant improvements in growth parameters after the procedure. Surgical portosystemic shunting should be actively considered in selected children with portal hypertension.

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.

Epidermal growth factor reduces ischemia-reperfusion injury in rat small intestine.

Objective To measure the effect of pre-ischemic administration of intraluminal epidermal growth factor on the changes in intestinal permeability induced by 30 mins of superior mesenteric artery occlusion, followed by 2 hrs of reperfusion. Design Prospective, randomized, placebo-controlled experimental study. Setting University basic science research laboratory. Subjects Healthy, young, adult, male Sprague-Dawley rats. Interventions A 10-cm segment of small intestine was isolated and studied in situ in rats that were anesthetized with fentanyl and mechanically ventilated. Intestinal ischemia-reperfusion injury was induced by temporary occlusion of the superior mesenteric artery for 30 mins, followed by 2 hrs of reperfusion. Three groups were studied: time controls with a sham operation, saline-treated ischemia-reperfusion, and epidermal growth factor–treated ischemia-reperfusion. Epidermal growth factor, 100 ng/min, was infused intraluminally, beginning 30 mins before and continued until 40 mins after ischemia. Measurements and Main Results Intestinal permeability was measured for each 10-min time period by using chromium-labeled EDTA. Histopathologic injury was assessed by light microscopy. After superior mesenteric artery occlusion, intestinal permeability increased approximately ten-fold and was sustained for 2 hrs of reperfusion in saline-treated rats. Pretreatment with epidermal growth factor significantly reduced the permeability changes during reperfusion by >60% compared with saline-treated animals (p < .05). Histopathologic sections revealed apparently more extensive loss of epithelial cells and mucosal disruption in saline-treated intestine compared with epidermal growth factor–treated intestine. Conclusion Pre-ischemic administration of intraluminal epidermal growth factor significantly protects against intestinal ischemia-reperfusion injury.

Ten days of orotracheal intubation with successful extubation in an infant with junctional epidermolysis bullosa.

OBJECTIVE: The most severe form of generalized junctional epidermolysis bullosa, the Herlitz variant, is associated with a number of extracutaneous manifestations. We report on a 45-day-old infant with laryngotracheobronchial mucosa involvement who underwent successful tracheal extubation after 10 days of orotracheal intubation and mechanical ventilatory support. Issues regarding airway management and mechanical ventilatory support in the pediatric intensive care unit are discussed.