Evaluation of the binding mechanism of iodine with trypsin and pepsin: A spectroscopic and molecular docking.

In this work, the effects of I2 on the activities and conformational structures of digestive enzymes, trypsin and pepsin were studied. The results indicated that the enzyme activities were decreased to some extent in the presence of I2, especially trypsin. Upon gradual addition of I2, the intrinsic fluorescence quenching of trypsin and pepsin were observed by mainly static collision and hydrophobic forces. I2 is more likely to cause the fluorescence quenching of trypsin than that of pepsin. Compared with pepsin, trypsin has a greater ability to bind with I2. The synchronous fluorescence spectral results indicated that I2 induced the quaternary structure changes of trypsin/pepsin and changed the hydrophobicity of Tyr and Trp residues. In addition, molecular docking was used to obtain the binding mode and the various amino acid residues of trypsin and pepsin with I2. These investigations may constitute a solid work to further explain the process of migration and transformation of I2 in digestive system.

Clinical Hemodynamic Parameters Do Not Accurately Reflect Systemic Oxygen Transport in Neonates after the Norwood Procedure.

OBJECTIVES: Clinical hemodynamic parameters (heart rate, systolic arterial pressure [SAP], and arterial and venous oxygen saturation saturations [SaO2 and SvO2 ]) are commonly used to guide management to optimize oxygen transport after the Norwood procedure. The adequacy of this practice has not been demonstrated. We examined the correlations between these clinical parameters and direct measurements of oxygen transport in these patients. METHODS: Oxygen consumption (VO2 ) was measured using respiratory mass spectrometry for 72 hours in 17 neonates after the Norwood procedure. Arterial, superior vena caval, and pulmonary venous blood gases and pressures were measured at intervals of 2-4 hours to calculate cardiac output (CO), systemic and pulmonary blood flows (Qs , Qp), systemic vascular resistance (SVR), total pulmonary vascular resistance including the Blalock-Taussig shunt (tPVR), oxygen delivery (DO2), and extraction ratio (ERO2 ). Heart rate and SAP were also recorded. RESULTS: Heart rate was positively correlated with VO2 (P = .004) and ERO2 (P = .005). SAP was positively correlated with CO (P = .006), VO2 (P = .02), ERO2 (P = .01), and SVR (P = .08). SaO2 was negatively correlated with tPVR, Qs, and DO2 but positively with Qp and SVR (P < .05 for all). SvO2 was positively correlated with CO, Qs , and DO2 (P < .0001 for all) and negatively correlated with SVR, VO2, and ERO2 (P < .05 for all). CONCLUSIONS: Routine clinical hemodynamic parameters do not accurately reflect oxygen transport after the Norwood procedure, except for SvO2, which does not differentiate between VO2 and DO2. Higher heart rate and SAP are correlated with a worse balance of oxygen transport. The results of clinical hemodynamic monitoring should be interpreted with caution. Direct measurements of oxygen transport parameters are important in the care of neonates after the Norwood procedure.

The relationship between plasma concentrations of ionized calcium and magnesium with cardiac energetics and systemic oxygen transport in neonates after the Norwood procedure.

OBJECTIVE: We sought to determine the relationship between plasma calcium and magnesium concentrations with postoperative systemic hemodynamics and oxygen transport in neonates after the Norwood procedure. METHODS: Postoperative systemic oxygen consumption was continuously measured using respiratory mass spectrometry for 72 hours in 17 neonates. Arterial, superior vena caval and pulmonary venous blood gases and pressures, plasma calcium, and lactate levels were measured at 2- to 4-hour intervals to calculate cardiac output, rate pressure product, cardiac power output, systemic oxygen delivery, and oxygen extraction ratio. Plasma magnesium levels were measured at 2- to 8-hour intervals. RESULTS: Plasma calcium levels decreased in the first 8 hours from 1.08±0.13 mmol/L to 0.98±0.08 mmol/L, followed by an increase to 1.10±0.26 mmol/L at 72 hours (P<.0001). Mg2þ change was significantly related to time after logarithmic transformation, rapidly decreasing from 1.62±0.25 mg/L to 0.90±0.15 mg/L in the first 40 hours and further decreasing slowly thereafter to 0.64±0.13 mg/L at 72 hours (P<.0001). Plasma magnesium levels had a significant positive correlation with cardiac output (P=.008) and cardiac power output (P=.01), and a negative correlation with heart rate (P=.05). Plasma magnesium levels correlated positively with systemic oxygen delivery and negatively with systemic oxygen consumption (P=.08 for both), resulting in significant negative correlations with oxygen extraction ratio (P=.04) and lactate levels (P=.05). For a given cardiac power output, plasma magnesium showed a significantly negative correlation with rate pressure product (P=.01). Plasma calcium levels showed the opposite trend, which was statistically insignificant except for lactate (P=.007). CONCLUSIONS: Plasma magnesium may exert favorable effects on myocardial energetics and systemic oxygen transport in neonates after the Norwood procedure, whereas plasma calcium may be harmful. Maintaining a relatively high level of plasma magnesium and a low level of plasma calcium may improve myocardial work efficiency and the balance of systemic and myocardial oxygen transport.

Studies on the interaction between chromium(VI) and human serum albumin: spectroscopic approach.

The interaction between Cr(2)O(7)(2-) and human serum albumin (HSA) was investigated using fluorescence, UV/vis, FT-IR, CD spectroscopy, and molecular modeling method. The experimental results showed that the fluorescence quenching of HSA by Cr(2)O(7)(2-) is a result of the formation of HSA-chromium(VI) complex; static quenching was confirmed to result in the fluorescence quenching. The corresponding thermodynamic parameters showed that the process of binding Cr(2)O(7)(2-) on HSA was a spontaneous molecular interaction procedure. Ionic, H-bonds and van der Waals interactions play a major role in stabilizing the complex. The Cr(2)O(7)(2-) altered the environments of Trp and Tyr residues in HSA.

Hyperglycaemia is negatively associated with systemic and cerebral oxygen transport in neonates after the Norwood procedure.

OBJECTIVE: Hyperglycaemia has been identified as a risk factor for adverse outcomes in critically ill patients, including those who have undergone cardiopulmonary bypass. Tight glucose control with insulin therapy has been shown to improve outcomes, but is not common practice for children following cardiopulmonary bypass. We examined the relationship between blood glucose level and systemic and cerebral oxygen transport in a uniform group of neonates after the Norwood procedure. METHODS: Systemic oxygen consumption was measured using respiratory mass spectrometry in 17 neonates for 72 hours postoperatively. Cardiac output, systemic and total pulmonary vascular resistances - including the Blalock-Taussig shunt, systemic oxygen delivery and oxygen extraction ratio, as well as arterial lactate and glucose, were measured at 2- to 4-hour intervals. Cerebral oxygen saturation was measured by near-infrared spectroscopy. RESULTS: Blood glucose levels ranged from 2.8 to 24.6 millimoles per litre. Elevated glucose level showed a significant negative correlation with cardiac output (p = 0.02) and cerebral oxygen saturation (p = 0.03), and a positive correlation with oxygen extraction ratio (p = 0.03). It tended to correlate positively with systemic vascular resistance (p = 0.09) and negatively with oxygen delivery (p = 0.09), but did not correlate with oxygen consumption (p = 0.13). CONCLUSIONS: Hyperglycaemia is negatively associated with systemic haemodynamics, oxygen transport, and cerebral oxygenation status in neonates after the Norwood procedure. Further study is warranted to examine tight glucose control with insulin therapy on postoperative systemic and cerebral oxygen transport and functional outcomes in neonates after cardiopulmonary bypass.

Aortic atresia is associated with an inferior systemic, cerebral, and splanchnic oxygen-transport status in neonates after the Norwood procedure.

OBJECTIVE: Aortic atresia (AA) is a risk factor for mortality after the Norwood procedure. The mechanisms remain unknown. We compared the profiles of systemic, cerebral, and splanchnic oxygen transport in neonates with hypoplastic left-heart syndrome with AA or aortic stenosis (AS) after the Norwood procedure. METHODS: Systemic oxygen consumption (VO(2)) was measured using respiratory mass spectrometry for 72 h in 17 neonates (nine in the AA group, eight in the AS group). Cardiac output (CO), systemic vascular resistance (SVR), oxygen delivery (DO(2)), and oxygen extraction ratio (ERO(2)) were calculated combining with blood gases and pressures at 2-4-h intervals. Cerebral (ScO(2)) and splanchnic (SsO(2)) oxygen saturations were measured by near-infrared spectroscopy. The doses of dopamine, milrinone, phenoxybenzamine, and vasopressin were recorded. Preoperative echocardiographic left-ventricular morphology and ejection fraction ratio were measured. RESULTS: Compared with the AS group, the AA group had lower CO (p = 0.03), higher SVR (p = 0.002), lower DO(2) (p = 0.07), VO(2) (p = 0.003), and ScO(2) (p = 0.07) during the first 40 h. SsO(2) was insignificantly lower. Despite a similar ERO(2), the AA group had higher lactate (p = 0.01). The AA group received higher doses of milrinone (p < 0.0001), vasopressin (p = 0.005), and phenoxybenzamine (p = 0.02), and lower higher doses of dopamine (p = 0.07). Vasopressin adversely correlated with systemic oxygen-transport variables and SsO(2) (p < 0.05). The AA group had thicker left-ventricular posterior wall (p = 0.05) that was negatively correlated with CO (p = 0.02). CONCLUSIONS: AA is associated with an inferior status of systemic, cerebral, and splanchnic oxygen transport after the Norwood procedure. Aggressive use of vasopressin may worsen systemic oxygen transport and decrease splanchnic perfusion.

The interaction of chromium(VI) with urease in solution.

The interaction between K(2)Cr(2)O(7) and urease was investigated using fluorescence, UV-vis absorption, and circular dichroism (CD) spectroscopy. The experimental results showed that the fluorescence quenching of urease by K(2)Cr(2)O(7) was a result of the formation of K(2)Cr(2)O(7)-urease complex. The apparent binding constant K (A) between K(2)Cr(2)O(7) and urease at 295, 302, and 309 K were obtained to be 2.14 × 10(4), 1.96 × 10(4), and 1.92 × 10(4) L mol(-1), respectively. The thermodynamic parameters, ΔH° and ΔS° were estimated to be -5.90 kJ mol(-1), 43.67 J mol(-1) K(-1) according to the Van't Hoff equation. The electrostatic interaction played a major role in stabilizing the complex. The distance r between donor (urease) and acceptor (K(2)Cr(2)O(7)) was 5.08 nm. The effect of K(2)Cr(2)O(7) on the conformation of urease was analyzed using UV-vis absorption, CD, synchronous fluorescence spectroscopy, and three-dimensional fluorescence spectra, the environment around Trp and Tyr residues were altered.

Studies on the interaction between imidacloprid and human serum albumin: spectroscopic approach.

The interaction between imidacloprid (IMI) and human serum albumin (HSA) was investigated using fluorescence and UV/vis absorption spectroscopy. The experimental results showed that the fluorescence quenching of HSA by IMI was a result of the formation of IMI-HSA complex; static quenching was confirmed to result in the fluorescence quenching. The apparent binding constant K(A) between IMI and HSA at three differences were obtained to be 1.51 x 10(4), 1.58 x 10(4), and 2.19 x 10(4) L mol(-1), respectively. The thermodynamic parameters, DeltaH degrees and DeltaS degrees were estimated to be 28.44 kJ mol(-1), 174.76 J mol(-1) K(-1) according to the van't Hoff equation. Hydrophobic interactions played a major role in stabilizing the complex. The distance r between donor (HSA) and acceptor (IMI) was obtained according to fluorescence resonance energy transfer. The effect of IMI on the conformation of HSA was analyzed using synchronous fluorescence spectroscopy CD and three-dimensional fluorescence spectra, the environment around Trp and Tyr residues were altered.

Carbon dioxide--a complex gas in a complex circulation: its effects on systemic hemodynamics and oxygen transport, cerebral, and splanchnic circulation in neonates after the Norwood procedure.

OBJECTIVE: Carbon dioxide is suggested to increase oxygen delivery after the Norwood procedure. We sought to quantitatively define the effects of stepwise increases in arterial carbon dioxide tension on systemic oxygen transport and cerebral and splanchnic circulation after the Norwood procedure. METHODS: Seven sedated, paralyzed, and mechanically ventilated neonates were studied after the Norwood procedure. Arterial carbon dioxide tension increased from 40-50-60 mm Hg using inspired carbon dioxide. Each step was 30 minutes. Pulmonary and systemic blood flow, vascular resistance, and oxygen delivery were calculated with the measurement of oxygen consumption and blood gases and pressures from the aorta, superior vena cava, and pulmonary vein. Plasma epinephrine and norepinephrine were measured. Cerebral and splanchnic oxygen saturations were measured by near-infrared spectroscopy, and cerebral blood flow velocity was measured by transcranial Doppler. RESULTS: Stepwise increase in arterial carbon dioxide tension was associated with a decrease in systemic vascular resistance (P < .001) and an increase in systemic blood flow (P < .01) and oxygen delivery (P < .0001), but not with significant changes in total pulmonary vascular resistance and pulmonary blood flow. Cerebral oxygen saturation increased (P < .0001), and splanchnic oxygen saturation decreased (P < .01). Oxygen consumption decreased (P < .01), and epinephrine and norepinephrine increased (P < .01 and .05). CONCLUSION: Moderate hypercapnia increases systemic blood flow because of its effect on systemic vascular resistance after the Norwood procedure. The increase in systemic blood flow is primarily a consequence of increased cerebral blood flow that compromises splanchnic circulation. The decrease in oxygen consumption improves oxygen transport, but the increase in catecholamines may be undesirable. Clinical use of carbon dioxide aiming to improve oxygen delivery should be with caution.

Significant correlation of comprehensive Aristotle score with total cardiac output during the early postoperative period after the Norwood procedure.

BACKGROUND: The comprehensive Aristotle score has been proposed as an individualized measure of the complexity of a given surgical procedure and has been reported to significantly correlate with postoperative morbidity and mortality after the Norwood procedure. An important factor leading to postoperative morbidity and mortality is low cardiac output. We studied the correlation between the comprehensive Aristotle score and cardiac output (CO) in infants after the Norwood procedure. METHODS AND RESULTS: Respiratory mass spectrometry was used to continuously measure systemic oxygen consumption (VO(2)) in 22 infants for 72 hours postoperatively. Arterial, superior vena caval and pulmonary venous blood gases were measured at 2 to 4 hour intervals to calculate CO. The comprehensive Aristotle score was collected. Hospital mortality was 4.5%. The comprehensive Aristotle score ranged from 14.5 to 23.5 and negatively correlated with CO (P = 0.027). Among the patient-adjusted factors, myocardial dysfunction (n = 10), mechanical ventilation to treat cardiorespiratory failure (n = 9) and atrioventricular valve regurgitation (n = 4) (P = 0.01) negatively correlated with CO (P = 0.06 to 0.07). Aortic atresia (n = 9) was associated with a lower CO (P = 0.01) for the first 24 hours which linearly increased overtime (P = 0.0001). No correlation was found between CO and other factors (P > 0.3 for all). CONCLUSIONS: Comprehensive Aristotle score significantly negatively correlates with CO after the Norwood procedure. A preoperative estimation of the comprehensive Aristotle score, particularly in association with myocardial dysfunction, mechanical ventilation to treat cardiorespiratory failure, atrioventricular valve regurgitation and aortic atresia may help to anticipate a high postoperative morbidity with low cardiac output syndrome.

Energy expenditure and caloric and protein intake in infants following the Norwood procedure.

OBJECTIVES: Cardiopulmonary bypass in infants results in a hypermetabolic response. Energy requirements of these patients have not been well studied. We assessed energy expenditure and caloric and protein intake during the first 3 days following the Norwood procedure. DESIGN: Clinical investigation. SETTING: Children's hospital. PATIENTS: Seventeen infants (15 boys, age 4-92 days, median 7 days). INTERVENTIONS: VO2 and VCO2 were continuously measured using respiratory mass spectrometry in 17 infants for the first 72 hrs following the Norwood procedure. The respiratory quotient was determined as VCO2/VO2. Energy expenditure was calculated using the modified Weir equation. Measurements were collected at 2- to 4-hr intervals. The mean values in the first 8 hrs, hours 8-32, hours 32-56, and the last 16 hrs were used as representative values for postoperative days 0, 1, 2, and 3. Total caloric and protein intakes were recorded for each day. MEASUREMENTS AND MAIN RESULTS: Energy expenditure, VO2, and VCO2 were initially high; declined rapidly during the first 8 hrs; and were maintained relatively stable in the following hours (p < .0001). Respiratory quotient showed a significant linear increase over the 72 hrs (p = .002). Energy expenditure on days 0, 1, 2, and 3 was 43 +/- 11, 39 +/- 8, 39 +/- 8, and 41 +/- 6 kcal/kg/day, respectively. Total caloric intake was 3 +/- 1, 14 +/- 5, 31 +/- 16, and 51 +/- 16 kcal/kg/day. Protein intake was 0, 0.2 +/- 0.2, 0.6 +/- 0.5, and 0.9 +/- 0.5 g/kg/day on days 0, 1, 2, and 3, respectively. CONCLUSIONS: Infants exhibit a hypermetabolic response immediately following the Norwood procedure. Caloric and protein intake was inadequate to meet energy expenditure during the first 2 days after surgery. Further studies are warranted to examine the effects of caloric and protein supplementation on postoperative outcomes in infants after cardiopulmonary bypass.

Effect of inhaled hydrogen sulfide on metabolic responses in anesthetized, paralyzed, and mechanically ventilated piglets.

OBJECTIVE: Induced hypometabolism may improve the balance between oxygen delivery and consumption and may help sustain tissue viability in critically ill patients with low cardiac output state. Inhaled hydrogen sulfide (H2S) has been shown to induce a suspended animation-like state in mice with a 90% decrease in oxygen consumption. We conducted a preclinical study to explore the potential effect of H2S on metabolic rate in large mammals. DESIGN: Prospective study. SETTING: Animal laboratory in a university hospital. SUBJECTS: Eleven anesthetized, paralyzed, and mechanical ventilated piglets (5.8 +/- 0.7 kg). INTERVENTIONS: The right carotid artery and superior vena cava were cannulated for arterial pressure monitoring and blood gas sampling. Seven piglets were sequentially exposed to 20, 40, 60, and 80 ppm of H2S over a period of 6 hrs (each level for 1.5 hrs) (H2S group), and additionally four piglets were exposed to air over the same period (control group). MEASUREMENTS AND MAIN RESULTS: Ambient temperature was fixed at 22 degrees C throughout. Central body temperature, arterial pressure, and heart rate were continuously monitored. Oxygen consumption and carbon dioxide production were continuously measured using respiratory mass spectrometry. Cardiac output was calculated using the Fick principle. Central temperature and oxygen consumption significantly and linearly decreased over the H2S exposures (p < .0001 for both), the rates of which were significantly less compared with those in the control group (p < .01 for both). Mean arterial pressure increased significantly (p = .007), whereas heart rate (p = .14), cardiac output (p = .89), and lactate (p = .67) did not change significantly during H2S exposures in H2S group; all the variables decreased significantly in the control group (p < .01 for all), and p < .01 by comparison with H2S group except for lactate (p = .05). CONCLUSIONS: H2S does not appear to have hypometabolic effects in ambiently cooled large mammals and conversely appears to act as a hemodynamic and metabolic stimulant.

The influence of systemic hemodynamics and oxygen transport on cerebral oxygen saturation in neonates after the Norwood procedure.

OBJECTIVES: Ischemic brain injury is an important morbidity in neonates after the Norwood procedure. Its relationship to systemic hemodynamic oxygen transport is poorly understood. METHODS: Sixteen neonates undergoing the Norwood procedure were studied. Continuous cerebral oxygen saturation was measured by near-infrared spectroscopy. Continuous oxygen consumption was measured by respiratory mass spectrometry. Pulmonary and systemic blood flow, systemic vascular resistance, oxygen delivery, and oxygen extraction ratio were derived with measurements of arterial, and superior vena cava and pulmonary venous gases and pressures at 2- to 4-hour intervals during the first 72 hours in the intensive care unit. RESULTS: Mean cerebral oxygen saturation was 66% +/- 12% before the operation, reduced to 51% +/- 13% on arrival in the intensive care unit, and remained low during the first 8 hours; it increased to 56% +/- 9% at 72 hours, still significantly lower than the preoperative level (P < .05). Postoperatively, cerebral oxygen saturation was closely and positively correlated with systemic arterial pressure, arterial oxygen saturation, and arterial oxygen tension and negatively with oxygen extraction ratio (P < .0001 for all). Cerebral oxygen saturation was moderately and positively correlated with systemic blood flow and oxygen delivery (P < .0001 for both). It was weakly and positively correlated with pulmonary blood flow (P = .001) and hemoglobin (P = .02) and negatively correlated with systemic vascular resistance (P = .003). It was not correlated with oxygen consumption (P > .05). CONCLUSIONS: Cerebral oxygen saturation decreased significantly in neonates during the early postoperative period after the Norwood procedure and was significantly influenced by systemic hemodynamic and metabolic events. As such, hemodynamic interventions to modify systemic oxygen transport may provide further opportunities to reduce the risk of cerebral ischemia and improve neurodevelopmental outcomes.

Comparison of the profiles of postoperative systemic hemodynamics and oxygen transport in neonates after the hybrid or the Norwood procedure: a pilot study.

BACKGROUND: After the Norwood procedure, early postoperative neonatal physiology is characterized by hemodynamic instability and imbalance of oxygen transport that is commonly attributed to surgical myocardial injury and a systemic inflammatory response to cardiopulmonary bypass (CPB). Because the Hybrid procedure (arterial duct stenting and bilateral pulmonary artery banding) avoids CPB, cardioplegic arrest, and circulatory arrest, we hypothesized that the Hybrid procedure is associated with superior postoperative hemodynamics and oxygen transport. METHODS AND RESULTS: Oxygen consumption (VO2) was continuously measured using respiratory mass spectrometry for 72 hours after Hybrid (n=6) and Norwood (n=13) procedures. Arterial, superior vena cava, and pulmonary venous blood gases and pressures were measured at 2- to 4-hour intervals to calculate systemic and pulmonary blood flows (Qs, Qp), and systemic vascular resistance (SVR), total pulmonary vascular resistance including pulmonary arterial band or B-T shunt (tPVR), cardiac output (CO), oxygen delivery (DO2), and oxygen extraction ratio (ERO2). Rate-pressure product was calculated as heart rate x systolic arterial pressure. When compared with the Norwood procedure, the early postoperative Hybrid patients had lower CO, higher SVR, and higher Qp:Qs ratios. In addition, the DO2 and VO2 were both lower in the Hybrids with higher ERO2 and lactate levels. This early postoperative pattern reversed after 48 hours. CONCLUSIONS: Although Hybrid procedure avoids CPB and cardioplegic arrest, the early hemodynamic profile is not superior to the Norwood in terms of cardiac output and control of pulmonary blood flow. These data strongly suggest that a "hands off" approach to postoperative care in Hybrid patients may not be appropriate in patients with preoperative diminished myocardial function; and in such patients a Norwood-derived management strategy (afterload reduction and inotropic support) should be considered.

Studies of the interaction between paraquat and bovine hemoglobin.

The interaction between paraquat (PQ) and bovine hemoglobin (BHb) was investigated using fluorescence and UV/vis absorption spectroscopy. The reactivity of the heme centers with superoxide anions formed by PQ was judged on the basis of the decrease of the Soret band. The experimental results showed that the fluorescence quenching of BHb by PQ was a result of the formation of PQ-BHb complex; static quenching was confirmed to result in the fluorescence quenching. The binding site number n, apparent binding constant K(A) and corresponding thermodynamic parameters were measured at different temperatures. The process of binding PQ molecule on BHb was a spontaneous molecular interaction procedure in which entropy increased and Gibbs free energy decreased. Hydrophobic and electrostatic interactions played a major role in stabilizing the complex. The effect of PQ on the conformation of BHb was analyzed using synchronous fluorescence spectroscopy.

Spectroscopic studies on the interaction between silicotungstic acid and bovine serum albumin.

The interaction between silicotungstic acid and bovine serum albumin (BSA) was investigated using fluorescence and UV/vis. The experimental results showed that the fluorescence quenching of BSA by silicotungstic acid is a result of the formation of SiW-BSA complex; static quenching and non-radiative energy transferring were confirmed to result in the fluorescence quenching. The binding site number n, apparent binding constant K(A) and corresponding thermodynamic parameters were measured at different temperatures. The process of binding SiW molecule on BSA was a spontaneous molecular interaction procedure in which entropy increased and Gibbs free energy decreased. Hydrophobic interaction force plays a major role in stabilizing the complex. The effect of silicotungstic acid on the conformation of BSA was analyzed using synchronous fluorescence spectroscopy.

Profiles of hemodynamics and oxygen transport derived by using continuous measured oxygen consumption after the Norwood procedure.

OBJECTIVES: The lack of accurate measurement of hemodynamics and oxygen transport has limited our understanding of Norwood physiology and postoperative management. We used measured oxygen consumption to characterize hemodynamics and oxygen transport after the classic Norwood procedure. METHODS: Fourteen neonates had continuous respiratory mass spectrometry to measure oxygen consumption (VO2). Arterial, superior vena caval, and pulmonary venous saturations were measured at 2- to 4-hour intervals for 72 hours postoperatively. Systemic (Qs) and pulmonary (Qp) blood flows, systemic vascular resistance (SVR) and pulmonary vascular resistance inclusive of the Blalock-Taussig shunt (BT-PVR), systemic oxygen delivery (DO2), and the oxygen extraction ratio (ERO2) were calculated. RESULTS: Qs and DO2 were low during the first 12 hours (1.8 +/- 0.6 L x min(-1) x m(-2) and 281 +/- 86 mL x min(-1) x m(-2) at the 12th hour, respectively) and increased over the study period (P < .05 for both). VO2 decreased markedly during the first 24 hours (101 +/- 26 to 86 +/- 16 mL x min(-1) x m(-2), P < .0001). Consequently, ERO2 decreased significantly over the study, most rapidly during the first 24 hours (0.44 +/- 0.11 to 0.28 +/- 0.09, P < .0001). There was a close correlation of DO2 to SVR and to Qs (P < .0001 for both). There was no correlation of DO2 to BT-PVR (P = .14) or to Qp (P = .67). DO2 was closely correlated with hemoglobin value (P < .0001), weakly correlated with PaO2 (P = .0002), and not correlated with arterial oxygen saturation (P = .32). CONCLUSIONS: There is wide variability of hemodynamics and oxygen transport after the Norwood procedure. The decrease in VO2 during the first 24 hours is the main contributor to improving the balance of oxygen transport. DO2 is most closely correlated to SVR and hemoglobin and weakly correlated to PaO2. It is not correlated to Qp. Postoperative management strategies to decrease VO2 and maintain a high hemoglobin level and a low SVR appear to be rational.

Adverse effects of dopamine on systemic hemodynamic status and oxygen transport in neonates after the Norwood procedure.

OBJECTIVES: The purpose of this study was to evaluate the effects of dopamine on hemodynamic status and oxygen transport in neonates after the Norwood procedure. BACKGROUND: Dopamine is widely used to augment cardiac performance and increase oxygen delivery (DO2) in patients after cardiopulmonary bypass (CPB). This might be at the expense of increased myocardial and systemic oxygen consumption (VO2), thus offsetting the improved DO2. This balance is particularly fragile in critically ill neonates. METHODS: Systemic oxygen consumption was continuously measured with respiratory mass spectrometry in 13 sedated, paralyzed, and mechanically ventilated neonates for 72 h after the Norwood procedure. Arterial, superior vena caval, and pulmonary venous blood gases were measured to calculate pulmonary blood flow (Q(p)) and systemic blood flow (Q(s)), DO2, and oxygen extraction ratio (ERO2). Rate-pressure product was calculated. Dopamine at a dose of 5 microg/kg/min was routinely administered at cessation of CPB and terminated within the first 48 h. Hemodynamic and oxygen transport measures were obtained before and at 100 min after the termination of dopamine. RESULTS: Terminating dopamine was not associated with significant changes in arterial pressure, Q(p), Q(s), or DO2 but was associated with a significant decrease in heart rate (p = 0.003), rate-pressure product (p = 0.03), and VO2 (-20 +/- 11%, p < 0.0001), resulting in a significant decrease in ERO2 (p = 0.01). CONCLUSIONS: Dopamine induces a significant increase in VO2 in neonates after the Norwood procedure, and termination is associated with an improved balance of VO2-DO2. These data further emphasize the importance of understanding changes in VO2 as well as DO2 in infants after cardiac surgery.

Inclusion of oxygen consumption improves the accuracy of arterial and venous oxygen saturation interpretation after the Norwood procedure.

OBJECTIVE: Management strategy for the postoperative Norwood neonate has been formulated from models that have estimated oxygen consumption (VO2). Superior vena caval oxygen saturation (SVO2), systemic arterial and superior vena caval oxygen saturation difference (Sa-VO2), and oxygen excess factor (Omega = arterial oxygen saturation/Sa-VO2) have been used as indirect indicators to estimate systemic blood flow (Qs) and oxygen delivery (DO2). We sought to examine the correlation of the indirect indicators to VO2-derived measures of oxygen transport. METHODS: Respiratory mass spectrometry was used to continuously measure VO2 after the Norwood procedure (n = 13). Measured saturations and the direct Fick equation were used to obtain pulmonary blood flow, Qs, DO2, and oxygen extraction ratio (ERO2) values. Correlations to SVO2, Sa-VO2, and Omega were sought. RESULTS: There was a close correlation of SVO2, Sa-VO2, and Omega to ERO2 (r = 0.92, 0.96, and 0.97, respectively; P < .0001). Correlation to Qs and DO2 was variable (r = 0.39 to 0.78, respectively; P < .0001). Correlation to VO2 was poor but significant (r = 0.24 to 0.40, P < .0001). Inclusion of VO2 improved the correlation to Qs and DO2 (r = 0.66 to 0.97, P < .0001). CONCLUSIONS: The close correlation of SVO2, Sa-VO2, and Omega to ERO2 indicates that each is a measure of the balance of DO2 and extraction. The significant but less reliable correlation to DO2 and VO2 indicates the values for SVO2, Sa-VO2, and Omega do not discriminate between the contribution of DO2 and VO2. Measured VO2 and hemodynamics may improve the optimization of postoperative management strategy in the individual neonate.

Studies of the interaction between palmatine hydrochloride and human serum albumin by fluorescence quenching method.

The interaction between palmatine hydrochloride with human serum albumin (HSA) was investigated by fluorescence quenching technique and UV/vis absorption spectroscopy. The results of fluorescence titration revealed that palmatine hydrochloride could strongly quench the intrinsic fluorescence of HSA by static quenching and nonradiative energy transferring. The electrostatic interaction plays a major role in stabilizing the complex. The binding site number n and apparent binding constant KA, corresponding thermodynamic parameters DeltaG, DeltaH and DeltaS at different temperatures were calculated. The distance r between donor (HSA) and acceptor (palmatine hydrochloride) was obtained according to fluorescence resonance energy transfer. The effect of palmatine hydrochloride on the conformation of HSA was analyzed using synchronous fluorescence spectroscopy.