Acetazolamide induces indomethacin and ischaemia-sensitive pial arteriolar vasodilation in the piglet

AIM: Acetazolamide (AZD) produces cerebral vasodilation. The underlying mechanism is unclear, but it is assumed to be largely due to CO2 retention and acidosis. We tested if cerebrovascular effects of AZD were similar to hypercapnia in the newborn pig. METHODS: We used the closed cranial window/intravital microscopy technique to determine pial arteriolar diameters simultaneously with laser-Doppler flowmetry (LDF) to monitor cortical blood perfusion. Anaesthetized (Na-thiopenthal +alpha-chloralose), ventilated, 1-day-old instrumented piglets (n=38) were divided into five experimental groups: time control (n=11), indomethacin, ibuprofen, Nomega-nitro-L-arginine methyl ester (L-NAME) treatments (1, 30, 15 mg/kg, i.v., n=6, 6, 4, respectively), and global ischaemia/reperfusion (I/R, 10 min induced by elevated intracranial pressure, n=11). Responses to 5-10% inhaled CO2 were recorded before and after the treatments, and then in a similar manner to AZD (10-20 mg/kg, i.v.). RESULTS: Hypercapnia and AZD produced pial arteriolar vasodilation and increases in cortical perfusion. Consistent with previous data, hypercapnia-induced changes were abolished by indomethacin, unaltered by ibuprofen and L-NAME and were significantly attenuated after I/R. AZD-induced vasodilation was also sensitive to indomethacin and I/R and was unaltered by ibuprofen or L-NAME. CONCLUSION: The mechanism of AZD-induced vasodilation appears to be similar/identical to hypercapnia, and pial arteriolar diameter changes reflect changes in cortical perfusion.     

Cerebrovasodilatory contribution of endogenous carbon monoxide during seizures in newborn pigs

Carbon monoxide (CO) and the excitatory amino acid glutamate both dilate cerebral arterioles in newborn pigs. The key enzyme in CO synthesis is heme oxygenase, which is highly expressed in neurons with glutamatergic receptor activity as well as cerebral microvessels. During seizures the extracellular level of glutamate is increased, which results in excessive depolarization of neurons. We hypothesized that CO is a mediator of excitatory amino acid-induced dilation of the cerebral microvasculature during seizures. Three groups of piglets were examined: 1) i.v. normal saline (sham control), 2) topical chromium mesoporphyrin (Cr-MP, 15 x 10(-6) M), and 3) i.v. tin-protoporphyrin (Sn-PP, 4 mg/kg). Synthetic metalloporphyrins (Cr-MP and Sn-PP) are heme oxygenase inhibitors, thereby reducing CO synthesis. Implanted closed cranial windows were used to monitor changes in pial arteriolar diameters. Seizures were induced by administration of i.v. bicuculline. Changes in pial arteriolar diameters were monitored during 30 min of status epilepticus. The percent increase in pial arteriolar dilation in the saline group during seizures was 68 +/- 3%. In the metalloporphyrin groups, the pial arteriolar dilation was markedly reduced (35 +/- 3% and 13 +/- 1%, for Cr-MP and Sn-PP, respectively; p < 0.05, compared with the saline group). We conclude that metalloporphyrins by inhibition of heme oxygenase and prevention of CO synthesis attenuate pial arteriolar dilation during seizures. Therefore, CO appears to be involved in cerebral vasodilation caused by glutamatergic seizures.     

Differences in the effects in the newborn piglet of various nonsteroidal antiinflammatory drugs on cerebral blood flow but not on cerebrovascular prostaglandins

To characterize the role of prostaglandins (PG) in the regulation of basal cerebral blood flow (CBF) in the newborn, we determined the effects of four nonsteroidal antiinflammatory drugs, indomethacin (3 mg/kg, n = 8 and 10 mg/kg, n = 5), aspirin (65 mg/kg, n = 6), ibuprofen (30 mg/kg, n = 8), and naproxen (15 mg/kg, n = 6), on CBF, cerebral metabolism, and cerebrovascular PG in conscious 1- to 3-d-old piglets. Drugs and vehicle (n = 8) were injected i.v., and measurements were made 5 min before and 20 and 60 min after injections. Neither the vehicle nor any of the nonsteroidal antiinflammatory drugs exerted significant effects on mean arterial blood pressure and on blood gases and pH. All four drugs, with the exception of indomethacin at the lower dose (3 mg/kg), decreased PG to nearly undetectable levels within 20 min; the low dose of indomethacin caused a small decrease (18-32%) in PG at 60 min. However, the effects of these agents on CBF were diverse. CBF increased after the administration of aspirin, decreased to almost the same extent after both low and high doses of indomethacin, and did not change after the administration of ibuprofen and naproxen. Cerebral metabolic rate for oxygen was increased by aspirin but was unaltered by the other drugs. The data suggest that PG may not play a critical role in the regulation of basal CBF in the newborn animal and that certain nonsteroidal antiinflammatory drugs may have additional actions unrelated to the inhibition of PG synthesis.     

Postasphyxial increases in prostanoids in cerebrospinal fluid of piglets

The dilator stimuli that contribute to postasphyxial increases in cerebral blood flow in the neonate are unclear. To assess the possible role of cyclooxygenase products in these responses, we measured pial arteriolar diameter in six piglets and determined levels of prostaglandin (PG) E2 and 6-keto-PG F1 alpha (hydrolysis product of PGI2) in cerebrospinal fluid (CSF) bathing the parietal cortex during control conditions, after 4-10 min of complete respiratory arrest (asphyxia), and after 5-12 min of reventilation. Pial arterioles are important resistance vessels in the cerebral circulation. Baseline pial arteriolar diameter was 220 +/- 40 micron (mean +/- SEM) and increased to a maximum of 252 +/- 49 and 267 +/- 56 micron after asphyxia and reventilation, respectively. During control conditions, CSF PGE2 (n = 6) and 6-keto-PGF1 alpha (n = 4) levels were 1947 +/- 310 and 794 +/- 147 pg/ml, respectively. During asphyxia, CSF levels of PGE2 did not increase, whereas 6-keto-PGF1 alpha increased modestly. During reventilation, CSF PGE2 increased to 3576 +/- 499 pg/ml, and 6-keto-PGF1 alpha increased to 2846 +/- 123 pg/ml. In other experiments, we determined that these CSF levels of PGE2 and PGI2 (as 6-keto-PGF1 alpha) were within the vasodilator range for pial arterioles. We conclude that postasphyxial increases in pial arteriolar diameter are associated with a rise in CSF levels of dilator prostanoids.     

Effect of therapeutic dose of indomethacin on the cerebral circulation of newborn pigs

The effects of treatment with 0.2 mg/kg of indomethacin on the cerebral blood flow and cerebral oxygen consumption of hypotensive, unanesthetized, newborn pigs were investigated. Hypotension was induced by hemorrhage (30 ml/kg) which reduced mean arterial pressure from 60 to 34 mm Hg. The decline in cerebral vascular resistance that occurred with hemorrhage allowed blood flow to all brain regions and cerebral oxygen consumption to continue unchanged. Treatment with 0.2 mg of indomethacin decreased plasma 6-keto-prostaglandin F1 alpha markedly and caused a modest increase in cerebral vascular resistance from 0.75 +/- 0.07 to 0.85 +/- 0.02 mm Hg X 100 g X min/ml at 40 min posttreatment. As a result, blood flow throughout the brain fell about 20%. Similarly, cerebral oxygen consumption declined from 2.88 +/- 0.13 to 2.03 +/- 0.21 ml O2/100 g X min following treatment of hypotensive piglets with 0.2 mg/kg of indomethacin. However, all piglets were conscious 40 min after treatment. We conclude that, although 0.2 mg/kg of indomethacin affects cerebral hemodynamics of hypotensive piglets, the effects are very modest in comparison to large increases in cerebral vascular resistance, decreases in cerebral blood flow and oxygen consumption, and coma that follow treatment of hypotensive piglets with 5 mg/kg of indomethacin.     

Randomized double-blind controlled trial comparing the effects of ibuprofen with indomethacin on cerebral hemodynamics in preterm infants with patent ductus arteriosus

A prospective randomized controlled trial was performed to compare the effects of ibuprofen with indomethacin on cerebral hemodynamics measured using near infrared spectroscopy in preterm infants during treatment for patent ductus arteriosus. Infants were randomly assigned to three intravenous doses of either indomethacin (0.20-0.25 mg/kg, 12 hourly) or ibuprofen (5-10 mg/kg, 24 hourly) and also received a dose of saline. The primary end points of the study were the effects of the first dose on cerebral blood flow (CBF) and cerebral blood volume. Fifteen infants received indomethacin and 18 received ibuprofen. The group mean (SD) values for CBF (mL x 100 g(-1) x min(-1)) before and after the first dose of indomethacin were 13.6 (4.1) and 8.3 (3.1), respectively, the change being significant (p<0.001). In contrast, no significant changes in CBF were observed with the first dose of ibuprofen, the respective before and after values being 13.3 (3.2) and 14.9 (4.7) mL x 100 g(-1) x min(-1). The median (interquartile range) value for change in cerebral blood volume (mL/100 g) after the first dose in the indomethacin group was -0.4 (-0.3 to -0.6) and in the ibuprofen group was 0.0 (0.1 to -0.1), the difference between the two groups being significant (p<0.001). Cerebral oxygen delivery changed significantly after the first dose in the indomethacin group but not in the ibuprofen group. Significant reductions in CBF, cerebral blood volume, and cerebral oxygen delivery also occurred after the 24-h dose of indomethacin, but there were no significant changes after the 48-h dose of saline in the indomethacin group or after the 24- and 48-h doses of ibuprofen. The patent ductus arteriosus closure rates after indomethacin and ibuprofen were 93 and 78%, respectively. We conclude that ibuprofen, unlike indomethacin, has no adverse effects on cerebral hemodynamics and appears to mediate patent ductus arteriosus closure.     

Preservation of cerebrovascular tone and reactivity by sodium channel inhibition in experimental prolonged asphyxia in piglets

Sodium channels using cAMP as a second messenger play a role in the regulation of cerebral circulation and metabolism. Cerebrospinal fluid (CSF) cAMP levels have been shown to correlate with the degree and duration of hypoxic injury and outcome and to be an indicator of cerebral vascular reactivity. We hypothesize that sodium channel inhibition either before or at termination of experimental asphyxia will attenuate cerebrovascular alterations and maintain CSF cAMP levels. Three groups of piglets with closed cranial windows were studied: asphyxia or group 1 (n = 5) and two treatment groups. Pigs were treated with 50 mg/kg of sodium channel blocker before asphyxia (group 2, n = 6) and after the termination of asphyxia and start of reventilation (group 3, n = 6). Asphyxia was sustained over 60 min by ventilating piglets with 10% O2 gas mixture and decreasing minute ventilation followed by 60 min of reventilation with room air. Every 10 min, pial arterial diameters were measured, and CSF samples were collected for cAMP determination. Vascular reactivity to topically applied isoproterenol (10(-4) M) was evaluated 60 min after recovery. During asphyxia, cAMP levels in group 2 peaked and declined at a later time with mean values remaining significantly higher than those of groups 1 and 3. During reventilation, CSF cAMP concentrations were highest in group 3 and lowest in group 1. Pial arteriolar dilation occurred during asphyxia in all three groups but to a lesser degree in the pretreated group compared with groups 1 and 3. Pial arteriolar reactivity to isoproterenol postasphyxia was preserved in both groups 2 and 3. In summary, in newborn pigs, pretreatment with sodium channel blocker resulted in higher CSF cAMP levels and a lesser degree of pial arteriolar dilation during prolonged asphyxia. Pretreatment or treatment at reventilation restored vascular tone and reactivity.     

Increasing ventilation pressure increases cortical subarachnoid cerebrospinal fluid prostanoids in newborn pigs

This study examines the responses of pial arterioles and venules to increased mean airway pressure (P aw-) in newborn pigs. We further characterized the changes in cortical subarachnoid cerebrospinal fluid prostanoids with increased P aw-, both before and after cyclooxygenase inhibition with indomethacin. Eight chloralose anesthetized newborn pigs were equipped with closed cranial windows and ventilated with a conventional infant pressure-cycled respirator. Increasing P aw- from 3.2 +/- 0.3 cm water to 14.3 +/- 0.6 cm water did not change pial arteriole or venule diameters. Cerebrospinal fluid prostanoids (6-keto-PGF1 alpha, TxB2, PGE2, and PGF2 alpha), however, were increased reversibly (3- to 5-fold) by increasing P aw-. After indomethacin (5 mg/kg, intravenous) pial arterioles constricted approximately 15% with increased P aw-. These results suggest that increasing ventilation pressure increases brain prostanoid production. Prostanoids appear to inhibit vasoconstriction and may be important in maintaining cerebral blood flow during the stress of mechanical ventilation.     

Effect of the cyclo-oxygenase blocker ibuprofen on cerebral blood volume and cerebral blood flow during normocarbia and hypercarbia in newborn piglets

Indomethacin modifies baseline cerebral haemodynamics and metabolism, as well as vasomotor adaptive responses. However, the significance of arachidonic acid metabolites in the regulation of cerebral circulation remains unclear. A study was made of the effect of inhibition of the cyclo-oxygenase pathway on baseline cerebral haemodynamics and CO2-induced vasodilation using the more specific cyclo-oxygenase blocker ibuprofen in a neonatal pig model. Two methods were used: radiolabelled microspheres to measure cerebral blood flow and near infrared spectroscopy to calculate absolute changes in cerebral blood volume. The relationship between CO2-induced changes in these two haemodynamic parameters was evaluated. Fifteen newborn piglets <7 d old received an i.v. infusion of either ibuprofen (30 mg/kg) (IB group, n = 8) or saline (control group, n = 7). Cerebral blood flow and absolute changes in cerebral blood volume were measured while the piglets were breathing room air at baseline and 30 min after infusion of ibuprofen or saline, and 15 min and 30 min after inducing hypercarbia. Global and regional cerebral blood flow (ml/hg/min) and absolute changes in cerebral blood volume (ml/hg) did not vary between baseline and 30 min after infusion of ibuprofen or saline. During hypercarbia, global and regional cerebral blood flow and absolute changes in cerebral blood volume increased significantly in both the ibuprofen and control groups (p < 0.01). The mean percentage increases in blood flow and blood volume at each measurement were almost identical, with approximately 90% of the increase in both parameters occurring after 15 min of hypercarbia, then reaching a plateau. However, we found no agreement between cerebral blood flow changes and absolute changes in cerebral blood volume. We conclude that ibuprofen did not alter either baseline cerebral circulation or physiological CO2-induced vasodilation in newborn pigs. We speculate that hypercarbic cerebral vasodilation could be caused either by mediators other than the cyclo-oxygenase metabolites of arachidonic acid or by a direct effect on vessel walls.     

Comparison of ibuprofen and indomethacin therapy for patent ductus arteriosus in preterm infants

BACKGROUND: Patent ductus arteriosus (PDA) is commonly found in very low-birthweight (VLBW) infants. The presence of respiratory distress syndrome (RDS) is also associated with increased frequency of significant PDA. Intravenous indomethacin has been used to treat and to prevent PDA in premature infants since 1976. However, concern remains regarding the safety of indomethacin, which affects renal, gastrointestinal and cerebral perfusion. Intravenous ibuprofen has recently been used to treat and to prevent PDA premature infants with PDA without reducing cerebral blood flow or affecting intestinal or renal hemodynamics. The aim of the present study is to compare intravenous ibuprofen and indomethacin with regard to efficacy and safety for the early treatment of PDA in preterm infants. METHODS: A total of 63 preterm infants with RDS who had a birthweight of < or =1500 g and gestational age of < or =32 weeks, were enrolled in the present study. All patients were treated with nasal continuous positive airway pressure with additional oxygen supply in inspired air>30%, or with mechanical ventilation. The patients' serum platelet counts were>100,000/uL, and serum creatinine values were <1.5 mg/dL. There were no 3-4 grade intraventricular hemorrhages before randomization, and all patients were aged 2-7 days and had echo-cardio-graphic evidence of significant PDA. Patients were randomized into two groups: the first group of neonates (group A, n = 32) received intravenous ibuprofen lysine 10 mg/kg, followed by 5 mg/kg after 24 and 48 h; the second group (group B, n = 31) received intravenous indomethacin 0.2 mg/kg every 12 h for three doses. RESULTS: Patent ductus arteriosus closed in 27 patients from the ibuprofen group (84.4%) and in 25 patients from the indomethacin group (80.6%). PDA reopened in three patients from the ibuprofen group (9.4%) and in three patients from the indomethacin group (9.7%). One patient in the ibuprofen group and two patients in the indomethacin group required ductal ligation. Serum creatinine and blood urea nitrogen (BUN) concentrations were lower in the ibuprofen group than in the indomethacin group. Urine output and creatinine clearance values were higher in the ibuprofen group than in the indomethacin group. CONCLUSIONS: Ibuprofen therapy is as efficacious as indomethacin for the treatment of PDA in preterm infants. Infants treated with ibuprofen have higher creatinine clearance and urine output and lower serum creatinine and BUN values than infants treated with indomethacin.     

Impact of prostaglandin and thromboxane synthesis blockade on disposition of group B streptococcus in lung and liver of intact piglet.

Group B streptococci (GBS) localizing in the lungs of infant piglets is killed in part by an oxygen radical-dependent mechanism (Bowdy BD, Marple SL, Pauly TH, Coonrod JD, Gillespie MN: Am Rev Respir Dis 141:648-653, 1990). The source of bactericidal oxygen radicals is unknown, but cyclooxygenation of arachidonic acid, an initial event in prostanoid synthesis, is accompanied by substantial oxygen radical generation. Because blockade of prostaglandin H synthase (cyclooxygenase) with indomethacin prevents GBS-induced pulmonary hypertension, we reasoned that the salutary effect of indomethacin might be associated with a reduction in the efficacy of bactericidal activity directed against GBS. To address this possibility, the distribution and viability of 111In-labeled GBS (10(8) colony forming units/kg/min i.v. for 15 min) were assessed in lungs and livers of control piglets, piglets treated with indomethacin (1 mg/kg), and piglets treated with OKY-046 (10 mg/kg), an inhibitor of thromboxane synthase that also forestalls GBS-induced pulmonary hypertension. Relative to control animals, indomethacin treatment increased pulmonary GBS uptake with no change in bacterial distribution into the liver. OKY-046 failed to influence pulmonary bacterial uptake but promoted a substantial increase in GBS depositing in the liver. In contrast to its effects on pulmonary bacterial deposition, indomethacin failed to increase lung bacterial viability relative to control animals. Indomethacin also was without effect on hepatic bacterial viability. OKY-046 failed to influence pulmonary bacterial viability but markedly augmented hepatic GBS viability to the extent that significant bacterial proliferation occurred.(ABSTRACT TRUNCATED AT 250 WORDS)     

Indomethacin does not alter the circulating catecholamine response to asphyxia in the neonatal piglet

The response of circulating catecholamines to asphyxia in unanesthetized, spontaneously breathing neonatal piglets was measured before and after treatment with indomethacin. Prior to treatment with indomethacin, baseline levels [geometric mean, pg/ml (95% confidence limits)] of D, E, and N were 162 (99-266), 174 (52-579), and 380 (286-506), respectively. Inhalation of 10% O2/9% CO2 for 20 min caused significant increases in arterial levels of all three catecholamines to 389 (230-659, 1514 (993-2306), and 3802 (2731-5293), respectively. Treatment with indomethacin (5 mg/kg, intravenous) did not significantly alter either baseline levels of the catecholamines or the levels after 20 min of the asphyxiating gas. In time control piglets, baseline levels and the response to asphyxia were similar before and after placebo. These results suggest that the circulating catecholamine response to asphyxia of the neonatal piglet is independent of the prostaglandin system.     

口服消炎痛和布洛芬治疗早产儿动脉导管未闭的比较

目的：静脉注射消炎痛是早产儿动脉导管未闭的常规治疗方法,但治疗过程中常出现一些副作用,如少尿、消化道出血、脑血流灌注减少。近年来,静脉注射布洛芬已用于治疗早产儿动脉导管未闭。布洛芬治疗不会减少脑血流灌注,也不会影响胃肠道和肾脏的血流动力学。伊朗目前尚无消炎痛和布洛芬的静脉制剂供应。该研究旨在比较这两种药的口服制剂治疗早产儿动脉导管未闭的疗效和安全性。方法：36例胎龄小于34周经超声心动图确诊患有动脉导管未闭的早产儿被随机分为两组,每组18人。一组给予消炎痛口服,每次0.2 mg/kg,24 h给药 1 次,共3次。另一组给予布洛芬口服,共 3 次,间隔时间为24 h,首剂为 10 mg/kg,随后两次各 5 mg/kg。用药后观察导管闭合率、副作用、并发症及临床过程。结果：用药后布洛芬组18例患儿动脉导管都闭合（100％）,而消炎痛组18例中有15例患儿动脉导管闭合（83.3%）（P＞0.05）。两组疗效差异统计学无显著性意义。治疗前后两组的血清尿素氮和肌酐含量差异也无显著性意义。消炎痛组发生了3例（16.6%）坏死性小肠结肠炎,布洛芬组则无,差异有显著性意义 (P＜0.05)。治疗1个月后两组成活率均为 94%（17／18）。消炎痛组1例死于坏死性小肠结肠炎,布洛芬组1例死于败血症。结论：口服布洛芬治疗早产儿动脉导管未闭和口服消炎痛治疗一样有效,而且坏死性小肠结肠炎的发生率较口服消炎痛治疗低。［中国当代儿科杂志,2007,9（5）：399-403］     

Effects of indomethacin and ibuprofen on mesenteric and renal blood flow in preterm infants with patent ductus arteriosus

OBJECTIVE: To evaluate the effect of intravenous ibuprofen and indomethacin for treatment of patent ductus arteriosus (PDA) on mesenteric and renal blood flow velocity in preterm infants. STUDY DESIGN: Seventeen mechanically ventilated preterm infants (<33 weeks' gestation) with PDA received either 0.2 mg/kg indomethacin (n = 8) or 10 mg/kg ibuprofen (n = 9), infused over 15 minutes. Mesenteric and renal blood flow velocity were measured by using Doppler ultrasonography. RESULTS: Indomethacin caused a significant reduction in mesenteric and renal blood flow velocity 30 minutes after drug administration; mesenteric and renal blood flow velocity did not return to the pretreatment values by 120 minutes. Ibuprofen did not alter blood flow 30 minutes after treatment, and blood flow increased 120 minutes after treatment. Mesenteric and renal blood flow velocity changes were significantly different between the 2 treatment groups. CONCLUSIONS: Compared with indomethacin, ibuprofen did not significantly reduce mesenteric and renal blood flow velocity.     

Treatment of patent ductus arteriosus with ibuprofen

AIM—To evaluate the efficiency and side effects of ibuprofen for the early treatment of patent ductus arteriosus (PDA)and compare it with indomethacin.METHODS—Forty preterm infants with gestational ages of less than 33 weeks, with respiratory distress syndrome (RDS) and echocardiographically confirmed PDA, were randomly assigned at days 2 to 3 of life to receive either intravenous indomethacin 3 × 0.2 mg/kg at 12 hour intervals or intravenous ibuprofen 1 × 10 mg/kg, followed by 5 mg/kg 24 and 48 hours later.RESULTS—PDA closed in 15 of 20 patients from the indomethacin group (75%) and in 16 of 20 (80%) from the ibuprofen group. Seven patients (three indomethacin, four ibuprofen) required a second treatment with indomethacin and in five (three in the indomethacin group and two in the ibuprofen group) the duct was ultimately ligated. Ibuprofen patients had a better urinary output and showed no increase in serum creatinine concentrations compared with the indomethacin group. Ibuprofen was not associated with any other side effect.CONCLUSIONS—Ibuprofen treatment seems to be as efficient as indomethacin in closing PDA on the third day of life in preterm infants with respiratory distress syndrome and seems to have fewer renal side effects.     

Prophylactic ibuprofen therapy of patent ductus arteriosus in preterm infants

This study was aimed at evaluating the efficacy of ibuprofen in the prophylaxis of patent ductus arteriosus (PDA) in very preterm neonates and at detecting eventual side-effects. A total of 46 preterm neonates with gestational age under 31 weeks were randomly assigned at 2 h of life: 23 to the prophylaxis group and 23 to the control group. The prophylaxis group received intravenous treatment with ibuprofen lysine (10 mg/kg), followed by 5 mg/kg after 24 h and 48 h. No placebo was given to the control group. No PDA was demonstrated at 72 h of life in 20 of the 23 babies in the ibuprofen group (87%) nor in 7 of the 23 control neonates (30.4%). All neonates with PDA received treatment with indomethacin. One neonate in the prophylaxis group and three in the control group underwent surgical ligation. Prophylaxis with ibuprofen was not associated with any significant side-effect except for food intolerance. Conclusion Ibuprofen prophylaxis seems to be efficient in closing patent ductus arteriosus and in reducing indomethacin treatment. No significant early side-effects were found due to ibuprofen. Received: 1 April 1999 / Accepted: 30 November 1999     

Cerebrovascular reactivity remains intact after cortical depolarization in newborn piglets.

Cerebrovascular reactivity is severely affected by ischemia, and changes in vascular responses have been reported after cortical spreading depression and head trauma as well. Cortical depolarization (CD) occurs during ischemia, cortical spreading depression, and head trauma, but its effects on cerebrovascular reactivity are unclear. We tested the hypothesis that CD induced by KCl diminishes the vascular responsiveness to various vasodilatory stimuli in piglets. Responses of pial arterioles were determined by changes in vascular diameter by use of a closed cranial window and intravital microscopy. Baseline arteriolar diameters were 105 +/- 3 microm (mean +/- SEM, n = 27). CD was elicited by topical administration of 1 mol/L KCl for 3 min. Vascular responses were measured before and 1 h after CD. KCl elicited CD and constricted arterioles by 54 +/- 4% (n = 27). N-methyl-D-aspartate induced dose-dependent vasodilation that was unaffected by CD; the percent changes were 9 +/- 1 versus 8 +/- 1 (before and after CD) at 10(-5) mol/L, 19 +/- 2 versus 18 +/- 3 at 5 x 10(-5) mol/L, and 29 +/- 2 versus 26 +/- 3 at 10(-4) mol/L (n = 9). Hypercapnic vasodilation was not diminished by CD; the percent changes were 15 +/- 2 versus 16 +/- 4 at 5%, and 27 +/- 5 versus 27 +/- 6 at 10% inspired CO2 (n = 8). Aprikalim and forskolin caused dilation that was also resistant to prior CD; the percent change values were 21 +/- 4 versus 18 +/- 3 and 16 +/- 2 versus 16 +/- 4 at 10(-6) mol/L, 36 +/- 5 versus 34 +/- 5 and 34 +/- 7 versus 37 +/- 7 at 10(-5) mol/L (n = 8), respectively. Finally, calcitonin gene-related peptide-induced vasodilation was unaffected by CD; percent changes were 15 +/- 3 versus 16 +/- 2 at 10(-7) mol/L and 26 +/- 4 versus 22 +/- 3 at 10(-6) mol/L (n = 8). The intact vascular responses after CD suggest that this component is not responsible for decreased cerebrovascular reactivity after ischemia, head trauma, or cortical spreading depression.     

Pressure ventilation increases brain vascular prostacyclin production in newborn pigs

Using awake, chronically catheterized newborn pigs, we measured cerebral blood flow (CBF), net cerebral vascular 6-keto-prostaglandin F1 alpha production, and cerebral metabolic rate of oxygen (CMRO2) during hypercapnia and during hypercapnia at increased mean airway pressure (Paw), both before and after treatment with indomethacin. CBF nearly doubled during hypercapnia. The hypercapnia-induced cerebral hyperemia was maintained when Paw was increased from 3 +/- 2 to 16 +/- 4 cm H2O during hypercapnia. Sagittal sinus pressure increased in proportion to the increase in Paw, and cardiac output was unchanged. Net cerebral production of 6-keto-prostaglandin F1 alpha increased from 9 +/- 1 to 15 +/- 1 ng/min/100 g tissue during hypercapnia and increased dramatically to 57 +/- 1 ng/min/100 g when hypercapnia was coupled with an increase in Paw. CMRO2 was not changed by either hypercapnia or increased Paw. After indomethacin, CBF decreased and cerebral vasodilation to hypercapnia did not occur. After indomethacin, adding increased Paw during hypercapnia dropped CBF below baseline, adversely affecting CMRO2. These results suggest that cerebral hypercapnia hyperemia requires brain prostanoid production and that when Paw is increased during hypercapnia, the contribution of prostanoids to maintaining CBF is increased. Increasing ventilation pressure during hypercapnia in piglets pretreated with indomethacin compromises CBF sufficiently to reduce CMRO2.     

Studies of the immaturity of the ADH-dependent cAMP system in conscious newborn piglets--possible impairing effects of renal prostaglandins

In 24 conscious newborn piglets the effects of 20 micrograms/kg body weight IV 1-deamino-8-D-arginine-vasopressin (DDAVP) in group 1, 5 mg/kg PO indomethacin in group 2, and the combined effects of both drugs in group 3 were studied by measuring urinary flow rate, urinary osmolality, creatinine clearance, total urinary and nephrogenous cyclic-adenosine 3':5'-monophosphate (cAMP) excretion, medullary cAMP content, and renal prostaglandin (PG)E2 and PGF2 alpha, excretion. DDAVP alone had no significant effects on ther above parameters, whereas indomethacin alone reduced only the PG excretion significantly. When both drugs were administered simultaneously, urinary concentration increased significantly (urinary flow rate decreased from 2.4 +/- 0.4 to 1.4 +/- 0.3 ml/hr (means +/- S.E.), and urinary osmolality increased from 444 +/- 29 to 552 +/- 33 mOsm/liter). Total urinary and nephrogenous cAMP excretion increased from 590 +/- 48 to 854 +/- 78 and 302 +/- 36 to 590 +/- 81 pmoles/hr/g kidney weight, respectively, whereas PGE2 and PGF2 alpha decreased from 249 +/- 33 to 19 +/- 4 and 192 +/- 32 to 43 +/- 7 pg/hr/g kidney weight, respectively. In addition, medullary cAMP content was considerably higher in group 3 (2010 +/- 200 pmoles/g medulla) than that observed in the control (1187 +/- 137), DDAVP (1218 +/- 115), and indomethacin (1230 +/- 168) groups.     

Oxygen free radicals and the cerebral arteriolar response to group B streptococci.

We used a cranial window preparation to observe the effects of direct application of group B streptococci to the surface of the brain in the adult rat. Continuous exposure to group B streptococci at concentrations of 10(3) and 10(5) organisms/mL caused progressive dilation of surface (pial) cerebral arterioles that became statistically significant (p less than 0.05) after 2.5 h. These results were reproduced with heat-killed organisms at the same concentration, but not with a bacteria-free filtrate of the growth medium. In separate studies, we found that infusion of alkaline cerebrospinal fluid (pH = 7.8) into the window did not reverse vasodilation, suggesting that it was not due to progressive cerebrospinal fluid acidosis. A solution of nitroblue tetrazolium infused into the window at the end of a 3-h exposure to the organism was promptly reduced, suggesting the presence of oxygen free radicals. Treatment with i.v. polyethylene glycol-superoxide dismutase and polyethylene glycol-catalase in doses of 10,000 and 20,000 U/kg, respectively, was itself without effect on pial arterioles, but treatment with these compounds before exposure to group B streptococci eliminated the vasodilation. These data support a role for oxygen free radicals in the pathogenesis of pial arteriolar dysfunction induced by exposure to group B streptococci.