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Biomedical subjects

B Chernow

Publications and source records attributed to B Chernow.

At least 19 recordsLinked to original sources
PubMed1992

Magnesium administration and dysrhythmias after cardiac surgery. A placebo-controlled, double-blind, randomized trial.

OBJECTIVE: To determine whether magnesium administration is effective in reducing postoperative morbidity and mortality after cardiac surgery. DESIGN: Randomized, double-blind, placebo-controlled trial. SETTING: A tertiary acute-care 500-bed university teaching hospital. PATIENTS: Over a 6-month period, 100 patients electively scheduled for cardiac surgery involving cardiopulmonary bypass were studied. INTERVENTIONS: Fifty patients were randomized to receive an intravenous infusion of magnesium chloride, 2 g, and 50 patients received placebo intraoperatively after the termination of cardiopulmonary bypass. RESULTS: Magnesium-treated patients had a significantly decreased frequency (P < .04) of postoperative ventricular dysrhythmias (eight [16%] of 50) compared with placebo-treated patients (17 [34%] of 50). Patients who were normomagnesemic postoperatively had new supraventricular dysrhythmias less frequently (P < .03) than patients who were hypomagnesemic postoperatively (eight [17%] of 48 vs 19 [37%] of 52). Compared with placebo-treated patients, magnesium-treated patients had significantly higher (P < .02) postoperative cardiac indices in the intensive care unit (2.8 +/- 0.1 vs 2.5 +/- 0.1 L/min per m2). Patients with postoperative total and ultrafilterable hypomagnesemia had postoperative ventricular dysrhythmias (P < .04) and required prolonged mechanical ventilatory support (P < .01) more frequently than patients without postoperative hypomagnesemia. CONCLUSIONS: Total and ultrafilterable hypomagnesemia are prevalent findings in cardiac surgery patients, and postoperative hypomagnesemia is strongly associated with clinically important morbidity. Magnesium administration decreased the frequency of postoperative ventricular dysrhythmias and increased the stroke volume and thereby cardiac index in the early postoperative period.

Adult↗
PubMed1991

Bedside diagnostic blood testing. Its accuracy, rapidity, and utility in blood conservation.

OBJECTIVE: --Bedside diagnostic testing utilizing microchemistry instruments potentially offers physicians the opportunity to evaluate urgent blood test results rapidly and reliably using only drops (250 microL) of whole blood. The use of microchemistry technology may also represent an essential component of a blood conservation program in acutely ill patients. We tested the hypothesis that a microchemistry instrument would have important advantages in the intensive care unit, including rapid turnaround time, decreased iatrogenic blood loss, and the provision of accurate analyte results. DESIGN: --One-year prospective, random-sample comparative study. SETTING: --A tertiary, acute care, 1000-bed university teaching hospital and a 450-bed university-affiliated community hospital. PATIENTS: --Blood samples from 850 patients were analyzed. RESULTS: --There were strong correlations (for pH, R2 = .97; PCO2, R2 = .97; PO2, R2 = .99; sodium, R2 = .83; potassium, R2 = .94; chloride, R2 = .90; glucose, R2 = .98; and hematocrit, R2 = .92) when paired samples were analyzed simultaneously in the laboratory comparing the microchemistry instrument and currently accepted clinical laboratory instruments. There were significant correlations (for pH, R2 = .91; PCO2, R2 = .94; PO2, R2 = .97; sodium, R2 = .91; potassium, R2 = .86; chloride, R2 = .91; ionized calcium, R2 = .82; glucose, R2 = .96; and hematocrit, R2 = .75) but increased variability occurred in some analyte results when samples were first analyzed in the intensive care unit (using the microchemistry instrument) and then transported to the laboratory in the routine fashion for "stat" determinations. CONCLUSIONS: --The multichannel microchemistry instrument provided accurate analyte determinations when compared with accepted clinical laboratory instruments. Significant savings of time and blood were also realized by the use of a microchemistry instrument in the intensive care unit. Bedside microchemistry may provide clinically important advantages in emergency departments, operating rooms, and neonatal, pediatric, coronary, adult medical and surgical, trauma, and burn intensive care units.

Blood Chemical Analysis↗
PubMed1991

Dose-dependent response to phenylpropanolamine: inhibition of orthostasis.

Phenylpropanolamine, a widely consumed over-the-counter drug, is known to elevate blood pressure, but the mechanism is unknown; it may be both a direct and indirect sympathomimetic. This study investigated the effects of 75-mg sustained-release phenylpropanolamine, 75-mg phenylpropanolamine plus 400-mg caffeine, and 150-mg phenylpropanolamine on blood pressure, plasma norepinephrine, and epinephrine levels in 16 normotensive subjects in a double-blind, placebo-controlled crossover design. Mean peak phenylpropanolamine levels of 317 +/- 26, 152 +/- 17, and 157 +/- 17 ng/mL for 150-mg phenylpropanolamine, 75-mg phenylpropanolamine, and 75-mg phenylpropanolamine plus 400-mg caffeine, respectively, were reached at about 3.6 hours after dosing. The maximal increases in supine diastolic blood pressures after all three phenylpropanolamine-containing drugs were almost three times that after placebo (P less than .05), but peak blood pressures occurred at about 2.3 hours earlier than peak phenylpropanolamine levels. Blood pressure increases correlated with phenylpropanolamine plasma levels (r = .49 for systolic blood pressure and r = .34 for diastolic blood pressure; P less than .0001 for both). Norepinephrine levels increased after the administration of 150-mg phenylpropanolamine and 75-mg phenylpropanolamine plus 400-mg caffeine; norepinephrine increases correlated with phenylpropanolamine levels (r = .34, P less than .0001). The expected increment in norepinephrine induced by standing was significantly decreased by phenylpropanolamine in a dose-dependent mode. The study supports the idea that phenylpropanolamine as both a direct (at alpha -1 and alpha-2 receptors) and an indirect sympathomimetic agent.

Blood Pressure↗
PubMed1991

Hypomagnesemia is common following cardiac surgery.

Hypomagnesemia is a common disorder in noncardiac surgical patients in the postoperative period, but the effect of cardiac surgery on serum magnesium concentrations remains unclear. The authors hypothesized that cardiac surgery is associated with hypomagnesemia, and prospectively studied 101 subjects (60 +/- 13.1 years of age) undergoing coronary artery revascularization (n = 70), valve replacement (n = 24), or both simultaneously (n = 7). Blood samples and clinical biochemical data were collected before induction of anesthesia, prior to cardiopulmonary bypass (CPB), immediately after CPB, and on postoperative day 1. Blood samples were analyzed for ultrafilterable magnesium, total magnesium, ionized calcium, parathyroid hormone, and free fatty acid concentrations. Outcome variables were also determined. Eighteen of 99 (18.2%) subjects had hypomagnesemia preinduction and this number increased to 71 of 100 (71.0%) following cessation of CPB (P less than 0.05). Patients with postoperative hypomagnesemia had a higher frequency of atrial dysrhythmias (22 of 71 [31.0%] v 3 of 29 [10.3%], P less than 0.05) and required prolonged mechanical ventilatory support (22 of 63 [34.9%] v 4 of 33 [12.1%], P less than 0.05). Hypomagnesemia is common following cardiac surgical procedures with CPB and is associated with clinically important postoperative morbidity.

Adult↗
PubMed1991

Adverse effect of therapeutic vasoconstrictors in experimental acute pancreatitis.

Alpha-adrenergic drugs commonly are used to treat hypotension resulting from severe acute pancreatitis. It was shown previously that although systemic arterial pressure is increased by phenylephrine, pancreatic microcirculatory perfusion is decreased. Because inadequate tissue perfusion may be critical in the progression of edematous pancreatitis to parenchymal necrosis, it was hypothesized that vasoconstrictors might be harmful in pancreatitis. Therefore the effect of phenylephrine on cerulein-induced mild pancreatitis were studied. Sprague-Dawley rats (n = 54) were randomly allocated to 6 experimental groups and subjected to the following infusion regimens: (1) cerulein (cae) + phenylephrine (phe), (2) cae + saline (NS), (3) NS + phe, (4) cae + phenoxybenzamine (pbz) + phe, (5) NS + pbz + phe, and (6) NS. Initial and terminal hematocrit, serum amylase activity, and blood ionized calcium concentration were determined. The animals were killed 9 hours after starting the infusion. Macroscopic and histologic changes were scored by a 'blinded' pathologist. Phenylephrine increased the severity of cerulein-induced pancreatitis as manifested by statistically significant adverse changes in serum amylase, hematocrit, ionized calcium, peripancreatitic soap formation, and acinar cell vacuolization. These changes were antagonized by alpha-adrenergic receptor blockade with phenoxybenzamine. It is concluded that phenylephrine is deleterious in acute experimental pancreatitis, the first demonstration of such an effect by a pharmacologic vasoconstrictor, and suggested that microcirculatory changes may be important in the transition of mild to severe pancreatitis. Caution in the use of vasoconstrictor drugs in patients with acute pancreatitis is recommended.

Acute Disease↗
PubMed1991

Hypomagnesemia is a frequent finding in the emergency department in patients with chest pain.

STUDY OBJECTIVE: To evaluate the frequency of low blood levels of total and ultrafilterable magnesium (total and ultrafilterable hypomagnesemia) in patients with chest pain in the emergency department, and to determine if hypomagnesemia is associated with other clinically important diagnostic and outcome variables in cardiac care. SETTING: An emergency department of a university teaching hospital. DESIGN: Prospective study of extracellular magnesium homeostasis in patients with chest pain in the emergency department and a cohort of patients without chest pain with a clinical indication for blood sampling. PATIENTS: During a 4-month period, 147 patients presenting to the emergency department were studied: 67 patients (mean +/- SD age, 61.4 +/- 13 years) with a chief complaint of chest pain (study group) and 80 patients (55.6 +/- 19 years) with other diagnoses (control group). RESULTS: Total and ultrafilterable hypomagnesemia occurred more frequently in patients with chest pain (20/67 [30%] and 9/67 [13%]) than in the control group (12/80 [15%] and 3/80 [4%]). Patients with a chief complaint of chest pain who were receiving diuretic medications were hypomagnesemic more frequently (9/16 [56%]) than patients not receiving diuretics (12/51 [23%]). In patients with chest pain admitted to the hospital with a diagnosis of "rule out" myocardial infarction, the frequency of hypokalemia was greater among hypomagnesemic patients (6/14 [43%]) than normomagnesemic patients (3/31 [10%]). A similar frequency of hypomagnesemia was noted in patients with a final diagnosis of myocardial infarction (4/15 [27%]) when compared with other patients admitted with chest pain (10/31 [32%]) in whom myocardial infarction was excluded. No association was noted among hypomagnesemia and length of hospital stay or the occurrence of hypotension or dysrhythmias. CONCLUSIONS: Total and ultrafilterable hypomagnesemia are frequent occurrences in patients with and without chest pain in the emergency department. Diuretic use is associated with hypomagnesemia in patients presenting with chest pain in the emergency department. These results support the concept that hypomagnesemia is common in patients with chest pain in the emergency department and is associated with hypokalemia but is not predictive of whether the patient with chest pain has had an acute myocardial infarction.

Chest Pain↗
PubMed1990

Hypocalcemia in experimental pancreatitis occurs independently of changes in serum nonesterified fatty acid levels.

Hypocalcemia and lipid abnormalities commonly occur in acute pancreatitis. Experimentally, increased plasma concentrations of free fatty acids (NEFA) can lower the serum calcium (Ca). We hypothesized that changes in blood-ionized calcium might parallel changes in NEFA concentration in pancreatitis. This hypothesis was tested in a model of severe necrotizing pancreatitis and a model of mild edematous pancreatitis. Adult male Sprague-Dawley rats (300-400 g) were randomized to receive: 100 microL sodium glycodeoxycholic acid (GDOC 34 mmol/L) infused into the pancreatic duct to produce severe necrotizing pancreatitis (Group 1); 100 microL 0.9% NaCl (NS) infused into the pancreatic duct (Group 2); Sham laparotomy (Group 3); A 6 h IV infusion of cerulein (5 mucg/kg/h) to produce mild edematous pancreatitis (Group 4); and a 6 h IV infusion of NS (Group 5). A significant time dependent decrease in blood-ionized Ca concentration, compared to normal rats, was observed in both GDOC-pancreatitis (0.836 +/- .057 vs 1.069 +/- .038 mmol/L p less than 0.001) and cerulein pancreatitis (0.988 +/- .028 vs 1.069 +/- .038 p less than 0.05), which was maximal 24 h after induction of pancreatitis. The degree of hypocalcemia correlated with the severity of pancreatitis (GDOC 0.836 +/- .057 vs cerulein 0.988 +/- .028 p less than .001). Hypocalcemia was not observed in any of the control groups. All experimental and control groups had significantly increased baseline NEFA concentrations compared with normal rats (p less than 0.001); however, no further increase in NEFA concentration occurred in conjunction with the observed time-dependent decline in ionized calcium concentrations. Although the NEFA concentrations observed in these experiments were comparable to those measured in human acute pancreatitis (exclusive of hyperlipemic pancreatitis), the time course of the changes suggests that increases in serum NEFA concentrations in experimental pancreatitis are not the primary factor mediating hypocalcemia.

Acute Disease↗
PubMed1990

Phenylpropanolamine increases plasma caffeine levels.

The effects of the widely consumed drugs caffeine and phenylpropanolamine are mediated through activation of the central and sympathetic nervous systems. Severe, life-threatening, and occasionally fatal hypertensive reactions have been reported after their combined use. This study examined the possible pharmacokinetic interaction of phenylpropanolamine and caffeine. Sixteen normal subjects received combinations of caffeine, phenylpropanolamine, and placebo. In subjects receiving 400 mg caffeine plus 75 mg phenylpropanolamine, the mean (+/- SEM) peak plasma caffeine concentration of 8.0 +/- 2.2 micrograms/ml was significantly greater than after 400 mg caffeine alone (2.1 +/- 0.3 micrograms/ml; t[24] = 2.4; p less than 0.01). Physical side effects were more frequent after the phenylpropanolamine-caffeine combination than after either drug alone or after placebo. Greater increases in both systolic and diastolic blood pressures occurred after the combination than after either drug alone. Because caffeine levels can be increased greatly when certain other drugs are coconsumed, these data indicate that phenylpropanolamine may enhance absorption or inhibit elimination of caffeine and may explain increased side effects reported after their combined use.

Adult↗
PubMed1990

Circulating interleukin-1 and tumor necrosis factor in septic shock and experimental endotoxin fever.

Interleukins (IL) -1 beta and -1 alpha and tumor necrosis factor (TNF-alpha) were measured by radioimmunoassay in plasma samples from 44 healthy individuals, 15 patients in septic shock, and 6 volunteers infused with endotoxin. Plasma IL-1 alpha levels were low (40 pg/ml) or undetectable in all situations. In 67% of the healthy subjects, plasma IL-1 beta levels were less than 70 pg/ml. Septic patients had higher plasma IL-1 beta levels (120 +/- 17 pg/ml, P = .001); those of surviving patients were higher than those of patients who died (P = .05). Plasma TNF-alpha concentrations in septic individuals were elevated (119 +/- 30 pg/ml) and correlated with severity of illness (r = .73, P = .003), but no correlation was observed between plasma IL-1 beta and TNF-alpha concentrations in individual samples. Infusion of endotoxin caused a twofold elevation of IL-1 beta, from a baseline of 35 +/- 5 pg/ml to a maximum of 69 +/- 27 pg/ml at 180 min (P less than .05). Peak TNF-alpha levels after endotoxin infusion were 15 times higher than IL-1 beta levels, were attained more rapidly (90 min), and as with the septic patients, did not correlate with IL-1 beta levels. These data support the concept that plasma IL-1 beta and TNF-alpha concentrations are regulated independently and are associated with different clinical outcomes.

Adolescent↗
PubMed1990

Renal hemodynamics and prostaglandin E2 excretion in a nonhuman primate model of septic shock.

The mechanisms responsible for renal insufficiency in septic shock (SS) have not been well characterized. We therefore investigated renal hemodynamics and the renal excretion of prostaglandin E2 (PGE2) in a nonhuman primate model of severe, low systemic vascular resistance (SVR) SS. In 18 cynomolgus monkeys, SS was induced by an infusion of 3 x 10(10) live Escherichia coli per kg; five saline-treated animals served as nonseptic controls. Systemic and renal hemodynamics, and urine PGE2 concentrations were determined over the 3 h after the induction of sepsis. The septic group demonstrated a significant (p less than .001) and sustained depression in both mean arterial pressure and SVR. Septic animals also had significantly lower effective renal plasma flow (ERPF) (p less than .01) and glomerular filtration rate (GFR) (p less than .01) compared to controls. Furthermore, the renal hemodynamic response to SS was biphasic, with significant increases in ERPF and GFR in the second hour postsepsis, followed by a pronounced decrease in the third postseptic hour. The septic group also demonstrated an increase in the renal excretion of PGE2 (p less than .001) that was temporally associated with the transient recovery in renal hemodynamics during the second postseptic hour. These sepsis-induced renal alterations may be important in the pathogenesis of renal insufficiency complicating clinical SS.

Acute Kidney Injury↗
PubMed1990

Plasma cortisol levels in patients with septic shock.

To investigate the endogenous adrenocortical response to sepsis, plasma cortisol concentrations were measured in 37 patients (53 +/- 3 yr of age) with septic shock. Patients were studied 11 +/- 2 h after shock commenced. Vasopressor therapy was required in 35 of 37 patients (median dopamine infusion rate of 11 micrograms/kg.min, range 3 to 74). Plasma cortisol concentrations were increased markedly (median 50.7 micrograms/dl, range 15.6 to 400) above normal values (10 to 20 micrograms/dl) in patients with septic shock. Neither patients who reversed their shock nor those who survived to hospital discharge had significantly different plasma cortisol concentrations from those who did not. Patients with Gram-positive infections had increased cortisol levels compared with those who had Gram-negative infections (median 83 micrograms/dl, range 32 to 400 vs. median 44 micrograms/dl, range 16 to 81, respectively; p less than .05). The source of infection, amount of vasopressors infused, and severity of shock were not associated with differences in cortisol concentrations. The length of time in shock before collection of the blood sample for measurements of cortisol and mean arterial pressure at the time of blood collection had significant but weak negative correlations with cortisol concentrations (p less than .05, rs = .37 and p less than .05, rs = -.40, respectively). We conclude that plasma cortisol concentrations are increased in patients with septic shock, but that the degree of increase is variable. This variability may, in part, be related to type of infection, length of time in shock, and BP at the time of blood sampling.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Insufficiency↗