Hypotension during septic shock does not correlate with plasma levels of nitric oxide metabolites in the conscious rat

Hypotension following administration of lipopolysaccharide may be due to excessive production of the potent vasodilator nitric oxide brought about by induction of nitric oxide synthase. The purpose of this study was to determine in conscious, fasted rats what role nitric oxide played in lipopolysaccharide-induced hypotension. When examined by Western immunoblot analysis, inducible nitric oxide synthase immunoreactivity was detected in the aorta at 3 hours and increased over time following administration of intraperitoneal lipopolysaccharide (20 mg/kg). When compared with saline-treated control rats, significant hypotension was observed at 2, 4, and 6 hours following lipopolysaccharide treatment. Blood pressure at 2 hours did not differ significantly from that at 6 hours. Using the Griess reaction to quantify plasma levels of nitrates and nitrites as an index of systemic nitric oxide production, an augmentation in the formation of these nitric oxide metabolites was demonstrated at 4 and 6 hours but not at 2 hours. Subcutaneous administration of the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (5 mg/kg) prevented lipopolysaccharide-induced hypotension, an effect reversed by subcutaneous L-arginine but not D-arginine (350 mg/kg). However, nitric oxide synthase inhibition did not attenuate the ability of lipopolysaccharide to increase plasma nitrate/nitrite levels. These data indicate that lipopolysaccharide-induced production of nitric oxide metabolites does not correlate with lipopolysaccharide-induced hypotension.

Randomised trial of dopamine compared with hydrocortisone for the treatment of hypotensive very low birthweight infants

AIM

To compare the efficacy of hydrocortisone with dopamine for the treatment of hypotensive, very low birthweight (VLBW) infants.

METHODS

Forty infants were randomly allocated to receive either hydrocortisone (n = 21) or dopamine (n = 19).

RESULTS

All 19 infants randomised to dopamine responded; 17 of 21 (81%) did so in the hydrocortisone group. Three of the four non-responders in the hydrocortisone group had clinically significant left to right ductal shunting. The incidence of bronchopulmonary dysplasia, retinopathy of prematurity, intraventricular haemorrhage, necrotising enterocolitis, symptomatic patent ductus arteriosus, hyperglycaemia, sepsis (bacterial or fungal) or survival did not differ between groups. The adrenocorticotrophic hormone (ACTH) stimulated plasma cortisol activity, either before or after treatment, did not differ between the two groups of infants. Although a significant difference in efficacy between dopamine and hydrocortisone was not noted (P = 0.108), there were four treatment failures in the hydrocortisone group, compared with none in the dopamine group.

CONCLUSION

Both hydrocortisone and dopamine are effective treatments for hypotension in very low birthweight infants.

Vasoactive hormones in uraemic patients with chronic hypotension

BACKGROUND

We evaluated the possible role of an imbalance between vasoconstrictor and vasodilator hormones in the pathophysiology of chronic hypotension in uraemia.

METHODS

Fourteen hypotensive haemodialysed patients, 14 normotensive haemodialysed patients, and 17 control subjects were included in this study. Plasma renin activity (PRA) and plasma levels of catecholamines, angiotensin II (AII), atrial natriuretic peptide (ANP), and arginine vasopressin (AVP) were measured.

RESULTS

The mean time on haemodialysis (HD) was longer in hypotensive patients than in normotensive patients (P < 0.01). Catecholamine levels were higher in the whole group of HD patients than in controls (P < 0.01). Catecholamine levels were higher in hypotensive patients than in normotensive patients, but the differences reached significance only for adrenaline (P < 0.05). PRA and plasma AII levels were higher in hypotensive patients than in the other two groups (P < 0.05), while no differences were observed between normotensive patients and controls. Plasma ANP and AVP levels were higher in HD patients than in controls (P < 0.01), but there were no differences between hypotensive and normotensive patients. In HD patients, mean blood pressure inversely correlated with PRA (r = -0.59, P < 0.01) and plasma AII levels (r = -0.80, P < 0.01).

CONCLUSIONS

Our results indicate that in HD patients with chronic hypotension there is an activation of the sympathetic and the renin-angiotensin systems. This activation is probably secondary in an attempt to compensate the vascular resistance to pressor stimuli reported in these patients.

Phlebotomy for pulmonary edema in dialysis patients

STUDY OBJECTIVE

To assess the efficacy of phlebotomy in the treatment of pulmonary edema in hemodialysis patients.

PROCEDURE

Maintenance hemodialysis patients presenting to the emergency room in respiratory distress from apparent pulmonary edema were assessed with regard to clinical response, change in blood pressure, change in hematocrit, and interval until the next hemodialysis treatment,

RESULTS

Twenty-one patients underwent phlebotomy and seventeen improved markedly and did not require intubation or emergent dialysis. Hemodialysis was initiated 15.6 +/- 13.6 SD hours later. Four were able to have their treatment 24 or more hours later. Thirteen of 21 (62%) were hypertensive at the time of treatment and blood pressure tended to normalize in this subset. Four of 21 (19%) developed transient hypotension without permanent sequelae. Pre-mean hematocrit = 25.0 + 6.0 and post phlebotomy = 22.6 + 4.6 SD. All patients receiving phlebotomy survived to hospital discharge.

CONCLUSION

Phlebotomy can often obviate the need for intubation or emergent dialysis in ESRD patients presenting with pulmonary edema.

Effects of progesterone on blood pressure, plasma volume, and responses to hypotension

Gonadal steroids have been implicated in the control of blood pressure and fluid homeostasis. These experiments test the effect of progesterone in ovariectomized ewes on blood pressure, volume, and hormone responses to hypotension. Eight ewes were each studied in four conditions: ovariectomized, progesterone and estrogen replaced, progesterone replaced, or sham treated. During each treatment mean arterial pressure (MAP), plasma volume (PV), baroreflex responsiveness, and adrenocorticotropic hormone (ACTH), arginine vasopressin (AVP), and renin responses to hypotension were determined. Progesterone treatment significantly reduced resting MAP and increased PV compared with ovariectomy or sham treatments. Heart period at 85 mmHg was reduced with progesterone treatment. There was no effect of progesterone treatment on ACTH, AVP, or renin or heart rate responses to hypotension. Basal AVP levels were increased, and angiotensin II concentrations were decreased, by estrogen and progesterone and by sham treatments; plasma Na+ also tended to be increased during these treatments. These results suggest that a small increase in progesterone can reset resting MAP and PV without altering reflex heart rate or endocrine responses to hypotension.

[Therapy refractory arterial hypotension after heart operation]

Adrenalin insufficiency associated with adrenal hemorrhage, is a rare complication after cardiac surgery in neonates. A boy suffering from transposition of the great arteries, who had an arterial switch-operation on day three of his life, acquired a bilateral adrenal hemorrhage. Clinically the situation resembled a septic shock. Despite large doses of catecholamines, he continued to have severe arterial hypotension, anuria, and kyperkalemia. The clinical condition did not change, although sepsis specific therapy was initiated. Consequently adrenal insufficiency, as a possible postoperative complication, was considered and prednisolon, initially in a dose of 15 mg/kg/d, was administered. The clinical condition improved dramatically. The diagnosis could be confirmed by ultrasound examination and determination of cortisol and ACTH plasma levels. Adrenal insufficiency was only transitory, adrenal sonography on day 135 returned to normal. The surgical procedure on heart-lung bypass, the obligatory anticoagulation and the perioperative stress have to be considered as pathogenetic factors.

Effect of methylene blue on refractory neonatal hypotension

Excess nitric oxide is a mediator of the hypotension in septic shock. Nitric oxide dilates vascular smooth muscle through activation of soluble guanylate cyclase. We report the increase in blood pressure caused by methylene blue (MB), a soluble guanylate cyclase inhibitor, in five neonates with presumed septic shock unresponsive to colloids, inotropic agents, and corticosteroids. MB was given intravenously at a dose of 1 mg/kg during a 1-hour period. MB increased blood pressure in each patient (average, 33% +/- 20%). Blood pressure subsequently decreased to near baseline values in three patients, who then received a second infusion of MB. Blood pressure again increased in these patients. Three of five patients were weaned from inotropic support within 72 hours. Three of five patients survived and were discharged home. We suggest that MB increased blood pressure in these neonates with refractory hypotension.

High level of circulating human tissue kallikrein induces hypotension in a transgenic mouse model

We established a unique transgenic mouse model in liver-targeted expression of human tissue kallikrein using a mouse albumin enhancer and promoter. Northern blot analysis and ELISA showed that human tissue kallikrein was predominantly expressed in the liver of transgenic mice and secreted into the circulation at a high level. The transcript was also detected in the kidney, pancreas, salivary gland and heart at a low level by reverse transcription-polymerase chain reaction followed by Southern blot analysis. Systolic blood pressures were measured by the tail-cuff method, all three independent transgenic mouse lines are hypotensive (84.6 +/- 1.0 mmHg, n = 17; 84.5 +/- 1.5 mmHg, n = 9; 83.1 +/- 0.8 mmHg, n = 13, P < 0.01) compared with the control mice (100.9 +/- 0.9 mmHg, n = 17). Administration of aprotinin, a potent tissue kallikrein inhibitor or Hoe 140, a bradykinin receptor antagonist, restored the blood pressure of transgenic mice but had no significant effect on control littermates. These studies show that over-production of tissue kallikrein in the circulation plays a role in blood pressure regulation.

Blood density monitoring during dialysis

Continuous monitoring of blood density (BD) was preformed in 4 stable dialysis patients in 20 sessions using a density meter based on a mechanical oscillator technique. Mean predialysis and postdialysis BDs were 1.0427 +/- 0.0031 g/cm3 and 1.0502 +/- 0.0055 g/cm3, respectively. For similar predialysis to postdialysis total body water reduction, significant difference in the mean BD increase was found between hypotensive and nonhypotensive groups (1.29 +/- 0.07%, 0.47 +/- 0.12%, respectively; p < 0.001). Eight hypotensive episodes occurred during 6 sessions. The mean value of the blood density changes slope (dBD/dr) during the 5 min preceding a hypotensive episode increased about 2.5 times more than did the mean of the predialysis to postdialysis blood density slope (27.6 +/- 2.2 g/cm3.min.10(-5), 10.5 +/- 0.4 g/cm3.min.10(-5), respectively; p < 0.001) under the condition of a constant ultrafiltration rate of 18.9 +/- 0.6 ml/min. Continuous monitoring of blood density allows abrupt change in plasma volume to be identified and seems to have a potential utility to the prevention of symptomatic hypotension episodes in patients receiving hemodialysis.

Increased nitric oxide production in hypotensive hemodialysis patients

A subset of patients on long-term hemodialysis have sustained hypotension, defined as a predialysis systolic pressure of < 100 mmHg. To determine the role of nitric oxide (NO), an important vasodilator, in this condition, the authors measured the plasma levels of nitrite (NO2-) and nitrate (NO3-), the known NO metabolites taken as an index of NO production, in 10 hypotensive patients on long-term hemodialysis. None of them had diabetes, cirrhosis of the liver, congestive heart failure, or infection. Fifteen age and gender-matched normotensive patients on hemodialysis were selected as control subjects. Measurements of plasma levels of nitrite and nitrate based on the Greiss reaction were made. There was no significant difference in hematocrit, serum intact parathyroid hormone, total calcium, inorganic phosphorus, albumin, heart rate, cardiac index, or interdialysis weight gain between these two groups. Plasma nitrite and nitrate levels did not correlate with either predialysis serum creatinine or blood urea nitrogen. The mean arterial pressure (MAP) was significantly lower and plasma nitrite and nitrate levels were significantly higher in chronic hypotensive patients than in normotensive patients (MAP: 68.30 +/- 3.24 mmHg vs 95.20 +/- 2.44 mmHg, p < 0.001; plasma nitrite and nitrate: 72.49 +/- 14.41 mumol/L vs 36.42 +/- 5.45 mumol/L, p < 0.05). In addition, MAP from hypotensive and normotensive patients on hemodialysis was inversely correlated with plasma levels of nitrite and nitrate (r = -0.54, p < 0.01). It was concluded that enhanced NO production in this subset of patients on hemodialysis may contribute to their chronic hypotension.

Inhibition of stimulated and basal ACTH by cortisol during ovine pregnancy

In pregnant ewes, as in pregnant women, plasma adrenocorticotropic hormone (ACTH) and cortisol concentrations are increased. Inhibition of free cortisol concentrations by dexamethasone, a synthetic glucocorticoid, is reduced in pregnant women compared with nonpregnant women. These experiments were designed to test the hypothesis that basal and stimulated ACTH concentrations are less sensitive to negative feedback inhibition by cortisol in pregnant ewes than in nonpregnant ewes. Ewes were infused with vehicle and with cortisol at two different rates (1 and 2 micrograms.kg-1.min-1) for 1 h; plasma ACTH concentrations during and after the infusion and after subsequent stimulation by hypotension were measured. Basal plasma ACTH concentrations during a 2-h infusion of cortisol (2 micrograms.kg-1.min-1) were also measured in undisturbed ewes. Cortisol significantly inhibited both stimulated and basal ACTH. The degree of suppression of ACTH was not reduced in the pregnant ewes compared with the nonpregnant ewes. The results indicate that both basal and stimulated ACTH are sensitive to negative feedback inhibition by cortisol during ovine pregnancy.

Does resistance to endotoxin in primates correlate with levels of plasma prekallikrein?

Increased release of BK by HK hydrolysis has been correlated with the severity of hypotension in septic patients and animals challenged with gram-negative bacteria or endotoxin (ETX). Since HK hydrolysis in vivo is attributed mainly to the catalytic reaction of kallikrein (KAL) formed by activation of plasma PK, I tested whether the known resistance to ETX-rhesus and baboon > man and chimp-correlated with PK levels. Immunoblots and amidolytic assays showed that PK levels did not correlate. They were in rhesus and man > baboon and chimp. Also, PK did not correlate with levels of other modulators of free KAL levels in plasma-factor XII, HK and KAL inhibitors. Nonetheless, the distribution of PK and its activation products in plasmas activated with kaolin at 37 degrees C is analogous in the 4 primates, suggesting a similar mechanism for KAL inhibition in vitro. The results suggest that factors not yet known must contribute to the differential resistance of primates to ETX. Knowledge of these factors will help in prophylaxis and therapy of septicemia.

Lidocaine attenuates the hypotensive and inflammatory responses to endotoxemia in rabbits

OBJECTIVE

To assess the effects of lidocaine on the hemodynamic and inflammatory responses to Escherichia coli endotoxemia in rabbits.

DESIGN

Prospective, randomized, controlled experimental study.

SETTING

University laboratory.

SUBJECTS

Twenty-seven female Japanese rabbits, anesthetized with urethane and ventilated mechanically.

INTERVENTIONS

Animals were randomly assigned to one of three groups: a) endotoxemic control group (n = 9), receiving intravenous Escherichia coli endotoxin (0.5 mg/kg bolus) via the mesenteric vein; b) laparotomy control group (n = 9), treated identically to the endotoxemic control group, except for substitution of 0.9% saline for endotoxin; and c) lidocaine-treated group (n = 9), treated identically to the endotoxemic controls and additionally, intravenous lidocaine (3 mg/kg bolus, followed by infusion at 2 mg/kg/hr) was administered immediately after endotoxin

MEASUREMENTS AND MAIN RESULTS

We compared hemodynamics, blood gases, and microscopic findings of lung tissue obtained at necropsy in each group. Laparotomy alone had a minimal effect on the parameters and findings. Endotoxin injection decreased mean systolic arterial pressure from 135 +/- 6 (SD) to 95 +/- 25 mm Hg (p < .05) and increased the mean base deficit from -1.2 +/- 1.8 to -14.4 +/- 4.2 mmol/L (p < .05), and caused the infiltration of neutrophils into the lungs. Lidocaine administration abolished the hypotension and attenuated the increase the base deficit to -9.5 +/- 2.1 mmol/L (p < .05) and the cellular infiltration in comparison with endotoxemic controls.

CONCLUSIONS

Lidocaine attenuated the hemodynamic and inflammatory responses to endotoxemia in rabbits. Findings suggest that lidocaine administration may prevent the development of hypotension and metabolic acidosis during endotoxemia.

No change in automatic function tests during uncomplicated haemodialysis

Uraemic autonomic dysfunction is reckoned to participate in dialysis hypotension, but a clear relationship has not been established. However, autonomic function is usually tested at rest, and possibly autonomic dysfunction arises or worsens during dialysis. We therefore performed easily repeatable tests of efferent sympathetic function, that is static exercise test and parasympathetic function, that is heart rate variability during Valsalva manoeuvre and deep breathing, at successive stages of a standard haemodialysis session; before dialysis, 20 min after dialysis without ultrafiltration, after 3 h of dialysis combined with ultrafiltration, and 20 min after dialysis. Studies were performed in 22 patients on chronic haemodialysis on a cuprophane dialyser. The mean ultrafiltration volume was 2.2 +/- 0.61. We found that blood pressure elevation upon static exercise, and heart rate variability during Valsalva or deep breathing test remained unaltered at the various stages of dialysis. On past performance the patients were divided into hypotension prone (n = 6) or resistant (n = 16). Hypotension prone patients showed a greater blood pressure drop during dialysis, but also showed an appropriately enhanced heart rate acceleration. The occurrence of autonomic dysfunction was not elevated in this group, nor did such dysfunction develop along dialysis. Predialysis parasympathetic function tests were abnormal in 10 patients. These patients also showed an augmented intradialytic blood pressure decrease, but no enhanced acceleration in heart rate. Their parasympathetic dysfunction did not worsen during dialysis. Based upon the predialysis exercise test, low responding patients (blood pressure increase 5 +/- 2 mmHg, n = 11) were distinguished. These subjects were not characterized by a greater blood pressure decrease or different heart rate acceleration. Generally, the responses upon exercise, whether low or high, remained unaltered during dialysis. we conclude that haemodialysis has no systematic effect on autonomic function. Hypotension-prone patients are not distinguished by a disturbed predialytic or intradialytic autonomic blood pressure control.

Endocrine stress reaction to surgery in brain-dead organ donors

We studied the course of plasma levels of the stress markers adrenocorticotropic hormone (ACTH), cortisol, human growth hormone (h-GH), beta-endorphin, and prolactin during retrieval surgery in eleven brain-dead organ donors scheduled for multiple organ explantation. Donors were divided into two groups according to hemodynamic stability. Hormones demonstrated a great variability in plasma levels and in the pattern of reaction, revealing a different degree of remaining pituitary function. Beta-Endorphin was the only stress hormone that showed a response to surgical stimuli in six patients. Only three of them developed a concomitant rise in ACTH. Cortisol, prolactin, and h-GH plasma levels did not change during the observation period. In the three cases with a slight elevation in ACTH, no subsequent change in cortisol was detectable. Beta-Endorphin showed greater variability and a tendency to higher levels in the group presenting with a higher arterial pressure, which resulted in a significant difference (P < 0.005) when distributions were compared using the Mann-Whitney U-test. No correlation was found between hypotensive episodes and deficiencies of other stress hormones. We conclude that pituitary function varies considerably in brain-dead organ donors without demonstrating a correlation to the onset of hypotension. Thus, we feel no need for a substitution treatment with any of the hormones investigated prior to organ explanation.

Midodrine hydrochloride in patients on hemodialysis with chronic hypotension

Chronic hypotension, volume nonresponsive, is not rare in hemodialysis patients and is usually refractory to various therapies. Midodrine hydrochloride is an alpha-mimetic drug acting directly on the peripheral alpha-receptor and increases blood pressure. We studied 10 uremic patients on hemodialysis with chronic hypotension to evaluate efficacy and safety of midodrine. Midodrine hydrochloride was administered at a dose of 2.5 mg twice on the dialytic day, 1.25 mg twice on the nondialytic day. Subjective symptoms and objective parameters were evaluated and compared before and after midodrine treatment. Midodrine significantly increased systolic pressure from 73.0 +/- 10.5 mm Hg to 90.5 +/- 12.3 mm Hg (p < 0.01); and diastolic blood pressure from 44.0 +/- 8.4 mm Hg to 55.4 +/- 7.9 mm Hg (p < 0.01) before dialysis. Orthostasis, dizziness, fatigue, blurred vision, dullness, headache, and depression improved an average of 62%. All patients tolerated midodrine treatment well. Only mild side effects were noted, including flush sensation, neck soreness, and headache. We conclude that midodrine may be another choice for uremic patients on hemodialysis with chronic hypotension which responds poorly to other conventional management.

Plasma neurotransmitters and functional illness

Although the concept of functional illness has blurred boundaries, some consensus exists on its understanding among clinicians. In short, it is easier to conceive than to define functional illness. Semantic and conceptual discussion concerning this issue have been endless. Many links exist that connect brain and body (mind and organs, psyche and soma). Amongst them, neurotransmitters, released by peripheral neurons and some glandular cells (adrenal, enterochromaffin cells, mast cells), are diverted into the bloodstream. Although neurotransmitters cannot cross the blood-brain barrier, basic and clinical research has progressively established the relationship between central and peripheral neurochemical activities. Hence, it is possible to obtain some approach to the central profile through the measurement of circulating neurotransmitters. However, this approach is more reliable if we can measure all circulating factors and, in addition, test the responses to different kinds of challenges (stressors, drugs, etc.). All diseases (somatic, psychiatric and psychosomatic) present some kind of plasma neurotransmitter disturbance; however, only in some has the whole abnormal profile been established. Technical difficulties as well as expensive procedures have interfered with the generalization of this research area. In the present review article, we summarize data quoted from current scientific literature reporting exhaustive research in this area.

Plasma concentration of human adrenomedullin in patients on hemodialysis

To investigate a possible pathophysiological role of human adrenomedullin (AM), we measured the plasma concentration of immunoreactive-AM (ir-AM) in 38 patients with end-stage renal disease (ESRD) on hemodialysis (HD) and 38 healthy subjects (age and sex matched). In addition, plasma ir-AM was characterized by a reverse-phase high performance liquid chromatography. The mean value (+/- SEM) of plasma AM in the patients before HD (10.1 +/- 0.67 fmol/ml) was markedly higher than that in the control group (2.9 +/- 0.13 fmol/ml, p < 0.001), but plasma AM levels were not altered by HD. There was a significant correlation between plasma AM levels and mean blood pressure (MBP) in a group of subjects including both patients before HD and healthy subjects (p < 0.01). In chromatographic study, the major peak of ir-AM in the plasma from patients on HD, as well as healthy subjects, emerged at an elution time identical to that of synthetic AM, indicating that the active form of AM was present in the circulating blood. The secretion of AM seemed to be increased in response to the conditions elicited by ESRD such as hypervolemia and/or hypertension, and reduced renal excretion of the peptide may also contribute to its high plasma level.

Effect of baroreceptor activation and systemic hypotension on plasma endothelin 1 and neuropeptide Y

To determine whether endothelin (ET-1) and neuropeptide Y (NPY) release are controlled by the carotid sinus (CS) baroreceptor or local endothelial mechanisms, we isolated and pump perfused the CS in eight chloralose-anesthetized dogs and controlled systemic arterial pressure (SAP) with an elevated reservoir connected to both femoral arteries. This allowed the SAP to be kept constant while CS pressure was varied from 55.8 +/- 2.0 (low CS) to 192 +/- 1.9 (high CS) mmHg (1 mmHg = 133.3 Pa) or CS pressure to be kept constant while SAP was lowered to 53.9 +/- 1.8 mmHg (low SAP). There was no significant change in ET-1 when CS pressure was varied (control, 2.08 +/- 0.50; low CS, 2.18 +/- 0.51; high CS, 2.11 +/- 0.38 pg/mL), but ET-1 was significantly higher during low SAP (2.93 +/- 0.49 pg/mL, p < 0.05). This increase was not observed with vagi and CS intact in six dogs or with vagi intact and CS constant in four dogs. In contrast, plasma NPY was significantly higher in the low CS condition (619.13 +/- 66.87 pg/mL) versus high CS condition (528.88 +/- 45.19 pg/mL, p < 0.05) and did not change during hypotension. In conclusion, NPY, but not ET-1, is affected by CS baroreceptor manipulation, and plasma ET-1 increases in response to hemorrhagic hypotension when modulating reflexes are abolished.

Central venous oxygen saturation, arterial base deficit, and lactate concentration in trauma patients

Our object was to explore the usefulness of central venous oxygen saturation, arterial base deficit, and lactate concentration in the evaluation of trauma patients. In busy urban trauma centers, limited operating room availability may necessitate that certain hemodynamically stable patients experience some delay between diagnosis of injury and surgery. Because hemodynamic compromise may occur before operation is undertaken, some means of identifying those patients who have the most severe injuries or who are at greatest risk for hemodynamic instability would be useful. We prospectively studied 40 patients with operative truncal injuries admitted to the Cook County Trauma Unit, Chicago, to examine the usefulness of postresuscitation central venous oxygen saturation (ScvO2), arterial lactate concentration, and arterial base deficit in this regard. Preoperative hypotension occurred in 12.5 per cent of these initially stable patients. ScvO2 did not significantly correlate with any of the parameters of blood loss and severity of injury examined. However, both base deficit and lactate concentration correlated with transfusion requirements; in addition, base deficit correlated with trauma score, and lactate correlated with peritoneal shed blood volume. Our data suggest that, after resuscitation, arterial base deficit and lactate concentration may be better indicators of blood loss than is ScvO2.

Increased serum nitrite and nitrate concentrations in children with the sepsis syndrome

OBJECTIVES

To measure total serum nitrite and nitrate concentrations in children with the sepsis syndrome as an indicator of endogenous nitric oxide production. To determine if there is an association between total serum nitrite and nitrate concentrations and vascular responsiveness to norepinephrine.

DESIGN

A prospective, clinical study.

SETTING

Tertiary, multidisciplinary, pediatric intensive care unit.

PATIENTS

Thirty-one children with the sepsis syndrome, 18 of whom were also hypotensive. Sixteen critically ill children without signs of the sepsis syndrome served as controls.

INTERVENTIONS

Blood samples were obtained from indwelling catheters. The norepinephrine dose to reach the age appropriate, 50th percentile mean arterial blood pressure was determined in patients receiving norepinephrine.

MEASUREMENTS AND MAIN RESULTS

Total serum nitrite and nitrate concentrations were measured on the first three days after the recognition of the sepsis syndrome. Patients with the sepsis syndrome had increased mean total serum nitrite and nitrate concentrations (day 1, 118 +/- 93 microM; day 2, 112 +/- 94 microM; day 3, 112 +/- 93 microM) vs. controls (43 +/- 24 microM, p < .05) on all 3 days. When sepsis syndrome patients were separated into nonhypotensive and hypotensive groups, only the patients with hypotension had increased concentrations vs. controls on all three days (p < .05). Sepsis syndrome patients with hypotension also had higher total serum nitrite and nitrate concentrations (145 +/- 97 microM) than sepsis syndrome patients without hypotension (82 +/- 76 microM, p < .05) on day 1. In five patients receiving norepinephrine infusions, increased total serum nitrite and nitrate concentrations were associated with higher norepinephrine requirements to maintain an age-appropriate, 50th percentile mean arterial blood pressure on each of the three study days (day 1, rs = 0.821, p < .05; day 2, rs = 0.900, p < .05; day 3, rs = 0.872, p < .05).

CONCLUSIONS

Children with the sepsis syndrome, particularly those patients with hypotension, have increased total serum nitrite and nitrate concentrations that likely reflect increased endogenous production of nitric oxide. Vascular hyporesponsiveness to norepinephrine during the sepsis syndrome may be, in part, a nitric oxide-mediated process.

Aspirin idiosyncrasy in systemic mast cell disease: a new look at mediator release during aspirin desensitization

OBJECTIVE

To report the clinical responses and mediator-release profiles of an aspirin-sensitive man with systemic mast cell disease during aspirin desensitization.

MATERIAL AND METHODS

We quantified the release of six mediators during aspirin desensitization.

RESULTS

Although aspirin was administered cautiously with an initial dose of 20 mg, successful aspirin desensitization necessitated complete monitoring and resuscitation capabilities of a medical intensive-care unit for 4.5 days because of frequent, severe anaphylactoid responses. To our knowledge, this is the first report of a pronounced increase in plasma levels of the vasodilator peptide calcitonin gene-related peptide during episodes of aspirin-induced hypotension. Increases in plasma levels of calcitonin and serum levels of tryptase paralleled those of calcitonin gene-related peptide, but plasma levels of calcitonin remained increased for up to 18 hours. Urinary excretion of histamine and 1-methyl-4-imidazoleacetic acid also showed precipitous, although delayed, increases. Excretion of the prostaglandin D2 metabolite 11 beta-prostaglandin F2 alpha followed a bimodal pattern during aspirin desensitization; after severe hypotensive responses, the maximal value was more than 490,000 pg/mL, but the level decreased to less than 100 pg/mL after therapeutic serum levels of salicylate were attained.

CONCLUSION

These data suggest that the hypotensive responses to aspirin in some patients with systemic mast cell disease may result from the combined effects of several mediators.