Intra-operative oxygen delivery in infusion volume-optimized patients undergoing laparoscopic colorectal surgery within an enhanced recovery programme: the effect of different analgesic modalities

Aim Patients undergoing major open surgery who have an indexed oxygen delivery (DO₂I) > 600 ml/min/m² have been shown to have a lower incidence of morbidity and mortality compared with those whose DO₂I is below this level. Laparoscopy and Trendelenburg positioning cause a reduction in DO₂I. We aimed to quantify the effect of the type of analgesia on DO₂I and to correlate the DO₂I achieved with the incidence of anastomotic leakage in patients undergoing laparoscopic surgery. Method Following ethical approval, patients were randomized to receive spinal anaesthesia (Group S), epidural analgesia (Group E) or intravenous morphine (Group P) followed by postoperative patient‐controlled analgesia (PCA). In addition to standard monitoring, oesophageal Doppler monitoring of the stroke volume allowed directed intravenous fluid therapy. The mean DO₂I was compared with the anastomotic leakage rate. Results Seventy‐five patients were recruited (Group S, 27; Group E, 23; Group P, 25). The mean (range) DO₂I for all patients was 490 (230‐750) ml/min/m². The analgesic modality had no effect on DO₂I. Of the 18 patients with a DO₂I of < 400 ml/min/m², four (22%) developed anastomotic leakage compared with one (%) of the 57 patients with a DO₂I of > 400 ml/min/m² (P = 0.01). Conclusion The analgesic modality used had no effect on the DO₂I achieved. Anastomotic leakage was significantly higher in patients with a DO₂I of < 400 ml/min/m². A further study assessing the outcome after raising the DO₂I with inotropes is required.     

Influence of dopexamine hydrochloride on haemodynamics and regulators of circulation in patients undergoing major abdominal surgery

Background: Catecholaminergic support is often used to improve haemodynamics in patients undergoing major abdominal surgery. Dopexamine is a synthetic vasoactive catecholamine with beneficial microcirculatory properties. Methods: The influence of perioperative administration of dopexamine on cardiorespiratory data and important regulators of macro- and microcirculation were studied in 30 patients undergoing Whipple pancreaticduodenectomy. The patients received randomized and blinded either 2 μg · kg^?1 · min^?1 of dopexamine (n=15) or placebo (n=15, control group). The infusion was started after induction of anaesthesia and continued until the morning of the first postoperative day. Endothelin-1 (ET-1), vasopressin, atrial natriuretic peptide (ANP), and catecholamine plasma levels were measured from arterial blood samples. Measurements were carried out after induction of anaesthesia, 2 h after onset of surgery, at the end of surgery, 2 h after surgery, and on the morning of the first postoperative day. Results: Cardiac index (CI) increased significantly in the dopexamine group (from 2.61±0.41 to 4.57±0.78 1 · min^?1 · m^?2) and remained elevated until the morning of the first postoperative day. Oxygen delivery index (DO₂I) and oxygen consumption index (VO₂I) were also significantly increased in the dopexamine group (DO₂I: from 416±91 to 717±110 ml/m² · m²; VO₂I: from 98±25 to 157±22 ml/m² · m²), being significantly higher than in the control group. pHi remained stable only in the dopexamine patients, indicating adequate splanchnic perfusion. Vasopressive regulators of circulation increased significantly only in the untreated control patients (vasopressin: from 4.37±1.1 to 35.9±12.1 pg/ml; ET-1: from 2.88±0.91 to 6.91±1.20 pg/ml). Conclusion: Patients undergoing major abdominal surgery may profit from prophylactic perioperative administration of dopexamine hydrochloride in the form of improved haemodynamics and oxygenation as well as beneficial influence on important regulators of organ blood flow.     

Global tissue oxygenation during normovolaemic haemodilution in young children

Sixteen patients (1–8 years) scheduled for major general surgery were chosen for the study. They were divided into two groups according to the replacement solution used for haemodilution (HD); whether 6% middle molecular weight hydroxyethyl starch (HES) or 6% dextran 60 (DEX). After induction of general anaesthesia and pulmonary artery catheterization, a precalculated amount of autologous blood was withdrawn while the patient's autologous blood was simultaneously replaced by either HES or DEX. Autologous blood was retransfused at a minimum haematocrit (Hct.) of 17% or at the end of surgery. The following parameters were measured and/or calculated before and after HD, every 20 min intraoperatively and hourly for 6 h postoperatively: heart rate (HR), mean arterial pressure (MAP), Cardiac index (CI), Hct., arterial and mixed venous oxygen content (CaO₂, CvO₂) and arterio-venous difference of oxygen content (avDO₂), oxygen delivery index (DO₂I), oxygen consumption index (VO₂I). The cardiovascular system remained stable. There was no significant difference as regards SvO₂, despite a significant decrease in CaO₂ to 10.8 and 10.0 ml·dl^?1 (median values) due to reduction of haemoglobin concentration in the HES and DEX groups respectively. In spite of the low hct. values during surgery DO₂I remained in normal range (median value 602 and 710 ml·min^?1·m^?2) in HEX and DEX group respectively. There was no significant change in VO₂I after haemodilution (median value 212 and 243 ml.min^?1·m^?2) in either group. No statistically significant difference was noticed between either groups regarding: CaO₂, CvO₂, DO₂I, VO₂I, and no side effects of the colloids were observed. Isovolaemic haemodilution (Hct. approx;17%) is well tolerated by young children undergoing major elective surgery; global tissue oxygenation was preserved throughout the procedure and both solutions used for haemodilution were equally effective.     

Calculated versus measured oxygen consumption during and after cardiac surgery. Is it possible to estimate lung oxygen consumption?

Background: Lung tissue is metabolically active and consumes oxygen. The oxygen content difference between arterial and mixed venous blood does not include the effect of pulmonary tissue oxygen uptake. Thus, oxygen consumption (VO₂) of the lung should be reflected as a difference between VO₂ measured by gas exchange and VO₂ derived by the Fick principle. The purpose of this study was to measure in clinical conditions this difference (taken to represent the VO₂ of the lung), and to evaluate the sources of error in lung VO₂ estimation. Methods: Nine patients undergoing coronary artery bypass grafting were studied. VO₂ was measured by indirect calorimetry (VO₂gasex) and compared to Fick-derived VO₂ (VO₂Fick) after induction of anaesthesia, after closure of the chest, at admission to intensive care, after stabilization of haemodynamics and during weaning from mechanical ventilation. The Fick-derived VO₂ was calculated from blood samples taken at the beginning and at the end of each 20 min measurement period, and the mean of 12 consecutive thermodilution cardiac output measurements taken during each 20 min measurement period. Results: VO₂gasex was higher than VO₂Fick (P <0.01; in all except 4 of 45 measurements). The difference between the measured and the calculated VO₂ was 33 ±25 ml/min (mean±SD, range -16–100 ml/min). This difference represented 14±3% (range 11–18%) of the whole body VO₂. The VO₂-difference was highest after the induction of anaesthesia (50±19 ml/min; range 20–81 ml/min, P < 0.03) and lowest on arrival at the intensive care unit (10±16 ml/min; range -16–39 ml/min). Core temperature did not correlate with the oxygen consumption difference. Conclusions: A constant difference between measured and calculated VO₂ can be detected in carefully controlled clinical conditions. The difference between the two methods is due to both lung oxygen consumption and errors in the measurement of VO₂, thermodilution cardiac output, haemoglobin and blood oxygen contents. We suggest that the perioperative changes of the VO₂-difference are due not only to variation of the measurements but also to changes in lung metabolic activity.     

Effects ofl-arginine andN-nitro-l-arginine treatment on hemodynamics, DO2, VO2, and extravascular lung water in a dog endotoxin shock model

To verify the effect of nitric oxide pathway modification during sepsis, experiments were conducted in four groups of anesthetized dogs which received lipopolysaccharide (LPS) intravenously (group 1), 300 mg·kg⁻¹ ofl-arginine plus LPS (group 2), 20 mg·kg⁻¹ ofN-nitro-l-arginine plus LPS (l-NNA, group 3), and normal saline as the control group. Hemodynamic and oxygenation data as well as extravascular lung water (EVLW) were measured or calculated. The results showed thatl-arginine increases cardiac output index (CI) and decreased the peripheral vascular resistance index (PVRI) without a significant influence on oxygen extraction ratio (O₂ER), oxygen delivery (DO₂), or oxygen consumption (VO₂). All of the untoward hemodynamic effects of LPS were exacerbated by the addition ofl-NNA. Therefore, as DO₂ was significantlys decreased byl-NNA, and although O₂ER was increased (insufficiently), VO₂ was still decreased significantly. EVLW was markedly increased byl-NNA. These results support the hypothesis that inhibition of nitric oxide synthesis may exacerbate hemodynamic and oxygenation consequences in septic shock.     

Effects of olprinone on hepatosplanchnic circulation and mitochondrial oxidation in a porcine model of endotoxemia

Purpose This study was performed in order to assess the effects of olprinone, a phosphodiesterase III inhibitor, on hepatic oxygen delivery (DO₂H), oxygen consumption (VO₂H), and mitochondrial oxidation in the liver of a porcine endotoxemia model. Methods Fourteen pigs received continuous infusion of endotoxin via the portal vein for 240 min. From t = 150 to t = 240 min, animals were randomly divided into two groups to receive saline (control [CONT]; n = 7), or olprinone (OLP; n = 7) via the central vein. Results In the OLP group, prior to olprinone treatment at 150 min, endotoxin induced significant decreases in the cardiac index (CI; from 120 ± 31 to 65 ± 13 ml·kg⁻¹·min⁻¹; P < 0.01) and DO₂H (from 3.58 ± 0.81 to 1.55 ± 0.49 ml·kg⁻¹·min⁻¹; P < 0.01), while VO₂H was maintained. After administration of olprinone (from t = 150 to t = 240 min), CI was unchanged, while DO₂H increased from 1.55 ± 0.49 to 1.93 ± 0.38 ml·kg⁻¹·min⁻¹ (P < 0.01) and VO₂H increased from 0.42 ± 0.28 to 0.69 ± 0.38 ml·kg⁻¹·min⁻¹ (P < 0.01). At t = 240 min, the oxidation level of cytochrome aa3 was significantly higher in the OLP group than in the CONT group (OLP, 66.2 ± 19.3% vs CONT, 26.4 ± 17.3%; P < 0.01). Conclusion Our data for this porcine endotoxemia model suggest that olprinone may have beneficial therapeutic effects in restoring not only systemic and hepatic circulation but also mitochondrial oxidation in the liver.     

Correlation between central venous oxygen saturation and oxygen delivery changes following fluid therapy

Background: The rationale for using central venous oxygen saturation (ScvO₂) in various clinical scenarios is that it reflects the balance between oxygen delivery (DO₂) and demands. In this study, we evaluated the correlation between ScvO₂ and DO₂ changes (ΔDo₂, ΔScvO₂) in patients receiving fluid therapy following coronary surgery. We also correlated the changes of mean arterial pressure (ΔMAP) and central venous pressure (ΔCVP), with ΔDO₂. Methods: Sixty consecutive sedated and mechanically ventilated adult patients, with cardiac index ≤2.3 L/min/m² and a pulmonary artery occlusion pressure ≤12 mmHg following coronary surgery, were included. Concomitant hemodynamic parameters, arterial and venous blood gases were measured before (T0) and after (T1) administration of a 500 ml bolus of an isotonic crystalloid solution over 30 min. The correlations between ΔDO₂ and ΔScvO₂, ΔMAP or ΔCVP were evaluated by linear regression analysis and Pearson test. Results: Cardiac index (1.9±0.2 vs 2.3±0.5 ml/min/m²), MAP (83±11 vs 94±13mmHg) and CVP (5.7±3 vs 7.1±3 mmHg) were significantly higher at T1 compared with T0. The correlation of ΔDO₂ with ΔScvO₂ was positive, significant (r=0.41; P=0.004) and superior to its correlation with ΔMAP (r=0.30; P=0.01) or ΔCVP (r=0.03; P=0.78). Conclusion: A significant correlation between ScvO₂ and DO₂ changes was found in patients receiving fluid therapy following coronary surgery. ScvO₂ could be used as an indicator to track DO₂ and to guide volume loading.     

The effect of pump flow on cerebral oxygen metabolism during cardiopulmonary bypass

We evaluated effects of pump flow on cerebral metabolism using transcranial Doppler (TCD) during cardiopulmonary bypass (CPB) in 22 adult patients undergoing coronary artery bypass grafting. All the patients were anesthetized with high dose fentanyl. The pump flow was controlled with non-pulsatile roller pump at 2.2–2.5 L/min/m² in group L and 2.7–3.0 L/min/m² in group H under α-stat acid-base regulation. Pharyngeal temperature was kept at 31°C in steady CPB state. Mean velocity of middle cerebral artery (MCAV) was monitored with TCD fixed on the temple continuously. Cerebral oxygen consumption was estimated by relating the difference in oxygen content between arterial and venous (jugular bulb) blood (AVDO₂) to flow velocity. In group L, blood oxygen saturation of jugular bulb (SjO₂) was stable during hypothermic period, but decreased significantly during rewarming period. In group H, SjO₂ was significantly increased with cooling, but went down to preoperative level during rewarming period. Significant difference of SjO₂ between two groups was noticed in rewarming period (52.9 ± 10.0% in group L and 65.6 ± 11.8% in group H, p=0.0133). MCAV tended to decrease with cooling and increase with rewarming, but which was not significant change respectively. Relative cerebral metabolic rate for oxygen (rCMRO₂) was defined as the percent change of the product AVDO₂ and MCAV. In each group, rCMRO₂ was decreased with cooling and increased with rewarming significantly. Especially, rCMRO₂ right after CPB discontinued was increased 1.7 times in L group and 2.0 times in group H as much as that of steady state of CPB. It is suggested that cerebral metabolism should be decreased during cooling to 31°C of pharyngeal temperature, 2.2–2.5 l/min/m² of pump flow was adequate to keep SjO₂ stable. On the other hand, it is necessary to increase pump flow to 2.7–3.0 l/min/m² during rewarming period as cerebral oxygen metabolic demand becomes greater.     

Cystatin C: influence of perfusion and myocardial injury on early (<24 h) renal function after pediatric cardiac surgery

Background: Cardiopulmonary bypass (CPB)‐associated renal dysfunction following cardiac surgery is well recognized. In patients with renal disease, cystatin C has emerged as a new biomarker which in contrast to creatinine (Cr) is sensitive to minor changes in glomerular filtration rate (GFR). Aim: We utilized cystatin C to investigate the association of CPB perfusion parameters with acute renal injury after pediatric cardiac surgery. Methods: Twenty children, aged 4–58 months (AVSD, n = 7; VSD, n = 9; and ASD, n = 4), were prospectively studied. Glomerular filtration rate was quantified postoperatively by creatinine clearance (first and second 12‐h periods; CrCl_0–12 and CrCl_12–24). Serum cystatin C and Cr were measured preoperatively and on days 0–3. Recorded CPB parameters included bypass duration (BP), perfusion pressure (PP), lowest pump flow (Q_min), lowest hematocrit, and corresponding lowest oxygen delivery (DO_{2 min}). Myocardial injury was determined by troponin‐I. Results: Postoperatively, GFR remained unchanged (CrCl_0–12 63.6 ± 37.0 vs CrCl_12–24 65.1 ± 27.5; P = 0.51) and only correlated with cystatin C (CrCl_0–12 vs cystatin C_Day0 [r = 0.58, P = 0.018] and Cr_Day0 [r = 0.09, P = 0.735]). Cr and cystatin C increased postoperatively to peak on days 2 and 3, respectively (Cr_PreOp 31 ± 6.9 vs Cr_Day2 36.9 ± 12.2, P = 0.03; cystatin C_Day0 0.83 ± 0.27 vs cystatin C_Day3 1.45 ± 0.53, P = 0.02). Increased cystatin C was significantly associated with BP (P = 0.001), mean PP (P = 0.029), Q_min (P = 0.005), troponin‐I (P < 0.001), and DO_2min <300 ml·min^?1·m^?2 (P = 0.007). Receiver–operator cutoff >1.044 mg·l^?1 for cystatin C exhibited 100% sensitivity and 67% specificity for detecting renal dysfunction, defined as GFR <55 ml·min^?1·1.73 m^?2. Conclusions: Cystatin C is a sensitive marker of early renal dysfunction following pediatric heart surgery. Variations in bypass parameters, myocardial injury, and ultimately critical oxygen delivery are significantly associated with the degree of renal impairment.     

Continuous Metabolic Monitoring in Infant Cardiac Surgery: Toward an Individualized Cardiopulmonary Bypass Strategy

Cardiopulmonary bypass (CPB) in infants is associated with morbidity due to systemic inflammatory response syndrome (SIRS). Strategies to mitigate SIRS include management of perfusion temperature, hemodilution, circuit miniaturization, and biocompatibility. Traditionally, perfusion parameters have been based on body weight. However, intraoperative monitoring of systemic and cerebral metabolic parameters suggest that often, nominal CPB flows may be overestimated. The aim of the study was to assess the safety and efficacy of continuous metabolic monitoring to manage CPB in infants during open‐heart repair. Between December 2013 and October 2014, 31 consecutive neonates, infants, and young children undergoing surgery using normothermic CPB were enrolled. There were 18 male and 13 female infants, aged 1.4 ± 1.7 years, with a mean body weight of 7.8 ± 3.8 kg and body surface area of 0.39 m². The study was divided into two phases: (i) safety assessment; the first 20 patients were managed according to conventional CPB flows (150 mL/min/kg), except for a 20‐min test during which CPB was adjusted to the minimum flow to maintain MVO₂ >70% and rSO₂ >45% (group A); (ii) efficacy assessment; the following 11 patients were exclusively managed adjusting flows to maintain MVO2 >70% and rSO2 >45% for the entire duration of CPB (group B). Hemodynamic, metabolic, and clinical variables were compared within and between patient groups. Demographic variables were comparable in the two groups. In group A, the 20‐min test allowed reduction of CPB flows greater than 10%, with no impact on pH, blood gas exchange, and lactate. In group B, metabolic monitoring resulted in no significant variation of endpoint parameters, when compared with group A patients (standard CPB), except for a 10% reduction of nominal flows. There was no mortality and no neurologic morbidity in either group. Morbidity was comparable in the two groups, including: inotropic and/or mechanical circulatory support (8 vs. 1, group A vs. B, P = 0.07), reexploration for bleeding (1 vs. none, P = not significant [NS]), renal failure requiring dialysis (none vs. 1, P = NS), prolonged ventilation (9 vs. 4, P = NS), and sepsis (2 vs. 1, P = NS). The present study shows that normothermic CPB in neonates, infants, and young children can be safely managed exclusively by systemic and cerebral metabolic monitoring. This strategy allows reduction of at least 10% of predicted CPB flows under normothermia and may lay the ground for further tailoring of CPB parameters to individual patient needs.     

Einfluß der prophylaktischen Gabe von N-Azetylzystein auf klinische Indikatoren der Gewebeoxygenierung unter Hyperoxie bei kardialen Risikopatienten

Hyperoxic ventilation, used to prevent hypoxia during potential periods of hypoventilation, has been reported to paradoxically decrease whole-body oxygen consumption (VO₂). Reduction in nutritive blood flow due to oxygen radical production is one possible mechanism. We investigated whether pretreatment with the sulfhydryl group donor and O₂ radical scavenger N-acetylcysteine (NAC) would preserve VO₂ and other clinical indicators of tissue oxygenation in cardiac risk patients. Methods. Thirty patients, requiring hemodynamic monitoring (radial and pulmonary artery catheters) because of cardiac risk factors, were included in this randomized investigation. All patients exhibited stable clinical conditions (hemodynamics, body temperature, hemoglobin, F_IO₂<0.5). Cardiac output was determined by thermodilution and VO₂ by cardiovascular Fick. After baseline measurements, patients randomly received either 150 mg kg^?1 NAC (n=15) or placebo (n=15) in 250 ml 5% dextrose i.v. over a period of 30 min. Measurements were repeated 30 min after starting NAC or placebo infusion, 30 min after starting hyperoxia (F_IO₂=1.0), and 30 min after resetting the original F_IO₂. Results. There were no significant differences between groups in any of the measurements before treatment and after the return to baseline F_IO₂ at the end of the study, respectively. NAC, but not placebo infusion, caused a slight but not significant increase in cardiac index (CI), left ventricular stroke work index (LVSWI) and a decrease in systemic vascular resistance. Significant differences between groups during hyperoxia were: VO₂ (NAC: 108±38 ml min^?1m^?2 vs placebo: 79±22 ml min^?1m^?2; P≤0.05), CI (NAC: 4.6±1.0 vs placebo: 3.7±1.11 min^?1m^?2; P≤0.05) and LVSWI (NAC: 47±12 vs placebo: 38±9; P≤0.05). The mean decrease of VO₂ was 22% in the NAC group vs 47% in the placebo group (P≤0.05) and the mean difference between groups in venoarterial carbon dioxide gradient (PvaCO₂) was 14% (P≤0.05). ST segment depression (>0.2 mV) was significantly less marked in the NAC group (NAC: ?0.02±0.17 vs placebo: ?0.23±0.15; P≤0.05). Conclusions. NAC helped preserve VO₂, oxygen delivery, CI, LVSWI and PvaCO₂ during brief hyperoxia in cardiac risk patients. Clinical signs of myocardial ischemia did not occur such as ST-depression if patients were prophylactically treated with NAC. This suggests that pretreatment with NAC could be considered to attenuate impaired tissue oxygenation and to preserve myocardial performance better in cardiac risk patients during hyperoxia.     

An analysis of oxygen consumption and oxygen delivery in euthermic infants after cardiopulmonary bypass with modified ultrafiltration

Background

The balance between systemic oxygen consumption (V?O₂) and delivery (DO₂) is impaired after cardiopulmonary bypass (CPB) and is related to systemic inflammatory response syndrome. We sought to assess V?O₂ and DO₂ and their relationship with proinflammatory cytokines after CPB with the use of modified ultrafiltration (MUF) in infants.

Methods

Sixteen infants, aged 1-11.5 months (median, 6.3 months), undergoing hypothermic CPB with MUF were studied during the first 12 hours after arrival in the intensive care unit (ICU). The central temperature was maintained at 36.8-37.1°C using external cooling or warming. V?O₂ was continuously measured using respiratory mass spectrometry. Arterial blood samples for the tumor necrosis factor (TNF), interleukin-6 (IL-6), and interleukin-8 (IL-8) were taken and DO₂ was calculated using the Fick principle on arrival at the ICU, and 2, 4, 8, and 12 hours postoperatively. Cytokines were additionally measured after induction of anesthesia and at the end of MUF.

Results

V?O₂ significantly decreased by 18.8% during the study period. DO₂ was depressed throughout this period and reached a nadir at 8 hours (357.1 ± 136.2 ml · min⁻¹ · m⁻²). The decrease in cytokines was accompanied with the decrease in V?O₂ despite varied relationships between the levels of each of the cytokines and V?O₂ measurements.

Conclusions

Our data indicate an unusual continuous decrease in V?O₂ during the first 12 hours after CPB in infants. Control of body temperature to maintain euthermia in addition to the use of MUF may be beneficial to the balance between V?O₂ and DO₂ in the early postoperative period.     

Effects of pulsatile and nonpulsatile perfusion on cerebral regional oxygen saturation and endothelin-1 in tetralogy of fallot infants

Although benefits of pulsatile flow during cardiopulmonary bypass (CPB) in pediatric heart surgery remain controversial and nonpulsatile CPB is still widely used in clinical cardiac surgery, pulsatile CPB must be reconsidered due to its physiologic features. In this study, we aimed to evaluate the effects of pulsatile perfusion (PP) and nonpulsatile perfusion (NP) on cerebral regional oxygen saturation (rSO₂) and endothelin‐1 (ET‐1) in pediatric tetralogy of Fallot (TOF) patients undergoing open heart surgery with CPB. Forty pediatric patients were randomly divided into the PP group (n = 20) and the NP group (n = 20). Pulsatile patients used a modified roller pump during the cross‐clamp period in CPB, while NP patients used a roller pump with continuous flat flow perfusion. The subjects were monitored for rSO₂ from the beginning of the operation until 6 h after returning to the intensive care unit (ICU). We also monitored the hemodynamic status and ET‐1 concentration and plasma free hemoglobin (PFH) in blood samples of all patients over time. Effective PP was monitored in PP patients, and pulse pressure was significantly higher in the PP group than in the NP group (P < 0.01). rSO₂ of the PP group was higher than that of the NP group (P < 0.01) during the cross‐clamp period, and this advantage of PP would be maintained until 2 h after patients returned to the ICU (P < 0.05). ET‐1 level in blood samples was lower at clamping off and CPB weaning and early ICU period in the PP group than in the NP group (P < 0.01), and ET‐1 concentration remained at a normal level after patients were transferred to the ICU 24 h in all patients. PFH levels in the PP group at pre‐clamp off and CPB weaned off were higher than those of the NP group (P < 0.05) in these cyanotic patients. PP can increase rSO₂ and improve microcirculation during cross‐clamping period in TOF pediatric patients, while PP resulted in more severe hemolysis in these cyanotic patients than NP.     

Asymptomatic carotid artery stenosis and cognitive outcomes after coronary artery bypass grafting

Objectives. Heart failure (HF) and atrial fibrillation (AF) are common comorbid conditions in hospitalised patients. AF may occur when left ventricular (LV) systolic function deteriorates. The aim was to compare HF patients with AF to patients in sinus rhythm (SR). Design. Echocardiography and a cardiopulmonary exercise test were performed in 67 patients with HF. Peak VO₂ was determined, as were LV-mass, enddiastolic, endsystolic volume indices (EDVI, ESVI), and ejection fraction (EF). Results. EF tended to be higher in AF compared to SR patients (39±10 vs. 31±10%), LV volume indices were smaller (ESVI:35±19 vs. 59±25 ml/m², p<0.0001, EDVI:56±24 vs. 83±29 ml/m², p<0.001). LV hypertrophy was prevalent (59% vs. 63%) and concentric hypertrophy tended to be more common with AF (50% vs. 21%). Peak VO₂ was similarly reduced in AF and SR (11.4±3.2 vs. 12.1±4.3 ml/kg*min). Conclusions. HF patients with AF compared to SR tend to have smaller LV volumes, less compromised systolic function and more frequent LV concentric hypertrophy. Our study supports the concept that AF in HF indicates a different patient population rather than an effect of progressive LV systolic dysfunction.     

Nitric oxide inhalation increases oxygen delivery after cardiovascular surgery in adult patients whether or not they have pulmonary hypertension

Purpose The purpose of this study was to quantify the increase in oxygen delivery (DO₂) produced by nitric oxide (NO) inhalation, and to clarify whether NO inhalation might be effective in adult patients after cardiovascular surgery whether or not they have pulmonary hypertension (PH). Methods The study was done on 26 adult patients after cardiovascular surgery. The indications for NO inhalation were postoperative hypoxic respiratory failure (POHRF) with or without PH. NO was administered via a premixing system or via a side-stream system. The dose was adjusted to between 1 and 10 (5.7±2.0) (mean±SD) ppm. Data were obtained just before and within 120 min after the initiation of NO inhalation. We initially analyzed the data from all the patients together and then compared data from two groups made up from just 22 of the 26 patients: 14 patients without PH whose PaO₂/FiO₂ before NO inhalation was less than 200 mmHg (simple POHRF group), and 8 patients who had both POHRF and PH (systolic pulmonary arterial pressure higher than 40 mmHg) (POHRF with PH group). Results In the original group of 26 patients, significant improvements were observed in PaO₂, PaO₂/FiO₂, CI, SPAP, CaO₂, DO₂I, and SvO₂ during NO inhalation. The increase in DO₂I was 68 ml·min⁻¹·m⁻² (+19.5%). PaO₂, PaO₂/FiO₂, CaO₂, DO₂I, and SvO₂ increased significantly in both groups. The increase in DO₂I was 60 ml·min⁻¹·m⁻² (+18.9%) in the simple POPHRF group and 79ml·min⁻¹·m⁻² (+18.0%) in the POHRF with PH group. Conclusion NO inhalation increases DO₂ by approximately 20% in adult patients after cardiovascular surgery, irrespective of whether or not they have pulmonary hypertension.     

Analysis of the Factors Related to a Decrease in Jugular Venous Oxygen Saturation in Patients with Diabetes Mellitus During Normothermic Cardiopulmonary Bypass

Purpose We sought to examine what factors, including cerebrovascular carbon dioxide (CO₂) reactivity, are related to a decrease in internal jugular venous oxygen saturation (SjvO₂) during normothermic cardiopulmonary bypass (CPB) in patients with diabetes mellitus.Methods Twenty-three diabetic patients scheduled to undergo elective coronary artery bypass grafting were studied. As a control, 27 age-matched control patients without diabetes mellitus were also examined. After the induction of anesthesia, a fiberoptic oximetry oxygen saturation catheter was inserted into the right jugular bulb to continuously monitor SjvO₂. Arterial and jugular venous blood gases were measured during CPB. The cerebrovascular CO₂ reactivity was measured after the induction of anesthesia and before the start of surgery using a 2.5-MHz pulsed transcranial Doppler probe.Results The SjvO₂ values in the diabetic group were lower than those in the control group at the initiation of CPB and at 20, 40, and 60 min after the start of CPB. The values for pre- and post-CO₂ reactivity in the control group did not significantly differ (pre-CPB: 4.8% ± 2.3% mmHg⁻¹; post-CPB: 5.9% ± 4.4% mmHg⁻¹). In contrast, the values for CO₂ reactivity were lower post CPB than pre-CPB in the diabetic group (Pre-CPB: 6.3% ± 2.9% mmHg⁻¹; post-CPB: 4.7% ± 2.6% mmHg⁻¹; P < 0.05). In the diabetic group, glycosylated hemoglobin A1c (HbA1c) is considered to be a factor related to a decrease in SjvO₂ during CPB.Conclusions Cerebrovascular CO₂ reactivity in diabetic patients decreased after the cessation of CPB but not in the control patients. In addition, HbA1c is also thought to be a factor related to a decrease in SjvO₂ in diabetic patients.     

O2-Utilisation während und nach hyperthermer Extremitätenperfusion mit rhTNFα und Melphalan

During isolated limb perfusion (ILP) severe metabolic impairment with a subsequent alteration in oxygen consumption can be observed. The mechanisms responsible for this may be extracorporeal circulation, hyperthermia, and appliation of cytostatic drugs and cytokines. Thirty-three patients underwent ILP with rhTNFα and melphalan for melanoma or soft-tissue sarcoma. Cardiopulmonary monotoring consisted of arterial and mixed venous blood-gas analysis and a Swan-Ganz catheter was inserted after induction of general anesthesia prior to any surgical intervention. Arterial (SaO₂) and mixed venous (SvO₂) oxygen saturation, serum lactate and end-expiratory CO₂ concentration were determined peri-and postoperatively for 72 h. Oxygen supply and consumption rates were measured systemically (DO₂I, VO₂I) and in the extracorporeal circuit (‘DO₂I, ‘VO₂I). For statistical analysis we used thet-test. During extracorporal circulation an increase of DO₂I and VO₂I was observed. A slight increase of lactate values began during the wash-out phase. Immediately after reperfusion, DO₂I, VO₂I and lactate increased significantly with normalization until the 2nd postoperative day. SaO₂ and SvO₂ remained unchanged. A significant correlation between regional toxicity and the postoperative maximum of serum lactate values was found. The increase of DO₂I and VO₂I in the tissues during ILP and after reperfusion was achieved by a significant increase in cardiac output while the oxygen extraction rate was not altered. Elevation of lactate values after reperfusion and the increase in oxygen utilization might be due to oxygen depletion in the perfused limb. This could contribute to the development of lactacidosis or rhabdomyolysis. There-fore, to minimize toxicity it seems to be mandatory to measure adequate tissue oxygen supply during ILP.     

Nitrous oxide reduces inspired oxygen fraction but does not compromise circulation and oxygenation during hemodilution in pigs

Background: The use of nitrous oxide (N₂O) during hemodilution has been questioned. Nitrous oxide reduces the inspired oxygen fraction (F₁O₂), depresses myocardial function and may reduce cardiac output (CO) and systemic oxygen delivery (DO_2SY). The aim of this study was to evaluate the importance of the effects of nitrous oxide on systemic and myocardial circulation and oxygenation during extreme, acute, normovolemic hemodilution. Methods: Ten midazolam-fentanyl-pancuronium anesthetized pigs were exposed to 65% N₂O before and after extreme isovole-mic hemodilution (hematocrit 33±1% and 10±1%, respectively). Systemic and myocardial hemodynamics, oxygen delivery and consumption and blood lactate were measured before (at FrO₂ 1.0 and 0.35) and during N₂O exposure. Results: Hemodilution caused an increase in CO from 137±43 to 229±32 ml kg^-1 min^-1 (P< 0.01), a decrease in systemic vascular resistance (from 42±14 to 20±4 mmHg L^-1 min^-1, P < 0.05), a decrease in mean arterial blood pressure (from 119±19 to 100±26 mmHg, P<0.05) and a decrease in DO_2SY from 21.1 ±6.9 to 13.7±2.1 ml kg^-1 min^-1 (P < 0.01). Cardiac venous blood flow increased by 135% (P < 0.01) and cardiac venous saturation from 25±6 to 41±5% (P < 0.05). After hemodilution, changing F_IO₂ from 1.0 to 0.35 reduced arterial blood oxygen content from 59.4±3.7 to 52.3±5.1 ml L^-1 (P < 0.01), mixed venous saturation (SvO₂) from 75±9 to 47±7% (P < 0.05) and DO_2SY from 13.7±2.1 to 11.9+2.3 ml kg^-1 - min^-1 (P < 0.05). Dissolved oxygen at F₁O₂=1.0 and F₁O₂=0.35 constituted 25.4±3.1% and 10.1 ±1.5%, respectively, of systemic oxygen delivery after hemodilution, compared with 10.7±1.2% and 3.9±0.5% before hemodilution (P < 0.01). Left ventricular oxygen delivery and consumption were unchanged. Exposure to N₂O did not affect mean arterial blood pressure or systemic vascular resistance before or after hemodilution. After hemodilution during N₂O-exposure, CO and DO_2SY decreased by 9% (P < 0.01 and P < 0.05, respectively), but no changes in SvO₂, systemic oxygen uptake or arterial lactate were observed. The effect of N₂O on myocardial oxygenation was similar before and after hemodilution; cardiac venous blood flow, left ventricular oxygen delivery and uptake decreased, but no animals showed left ventricular lactate production. Conclusion: Nitrous oxide did not compromise systemic and myocardial circulation and oxygenation during acute normovolemic hemodilution in pigs. Possible adverse effects from the use of nitrous oxide during hemodilution seem to be related to a reduced F_IO₂, reducing the safety margin for systemic oxygen delivery.     

Cerebral oxygen metabolism during total body flow and antegrade cerebral perfusion at deep and moderate hypothermia

The aim of this study is to evaluate the effect of temperature on cerebral oxygen metabolism at total body flow bypass and antegrade cerebral perfusion (ACP). Neonatal piglets were put on cardiopulmonary bypass (CPB) with the initial flow rate of 200 mL/kg/min. After cooling to 18°C (n = 6) or 25°C (n = 7), flow was reduced to 100 mL/kg/min (half‐flow, HF) for 15 min and ACP was initiated at 40 mL/kg/min for 45 min. Following rewarming, animals were weaned from bypass and survived for 4 h. At baseline, HF, ACP, and 4 h post‐CPB, cerebral blood flow (CBF) was measured using fluorescent microspheres. Cerebral oxygen extraction (CEO₂) and cerebral metabolic rate of oxygen (CMRO₂) were monitored. Regional cranial oxygen saturation (rSO₂) was continuously recorded throughout the procedure using near‐infrared spectroscopy. At 18°C, CBF trended lower at HF and ACP and matched baseline after CPB. CEO₂ trended lower at HF and ACP, and trended higher after CPB compared with baseline. CMRO₂ at ACP matched that at HF. Cranial rSO₂ was significantly greater at HF and ACP (P < 0.001, P < 0.001) and matched baseline after CPB. At 25°C, CBF trended lower at HF, rebounded and trended higher at ACP, and matched baseline after CPB. CEO₂ was equal at HF and ACP and trended higher after CPB compared with baseline. CMRO₂ at ACP was greater than that at HF (P = 0.001). Cranial rSO₂ was significantly greater at HF (P = 0.01), equal at ACP, and lower after CPB (P = 0.03). Lactate was significantly higher at all time points (P = 0.036, P < 0.001, and P < 0.001). ACP provided sufficient oxygen to the brain at a total body flow rate of 100 mL/kg/min at deep hypothermia. Although ACP provided minimum oxygenation to the brain which met the oxygen requirement, oxygen metabolism was altered during ACP at moderate hypothermia. ACP strategy at moderate hypothermia needs further investigation.     

Validation of the Center for Medicare and Medicaid Services algorithm for eligibility for dialysis

The Center for Medicaid and Medicare Services (CMS) has recently revised their end-stage renal disease (ESRD) Medical Evidence Report, Medicare Entitlement, and Patient Registration CMS 2728 Form. The modified algorithm calls for the use of formulae to estimate glomerular filtration rate (GFR). The new criterion is defined as estimated GFR of less than 20 ml/min per 1.73 m². GFR is either estimated by Schwartz formula (C_SCH) in children or Modification of Diet in Renal Disease formula (C_MDRD) in adults. The purpose of this communication is to test the validity of the new CMS GFR algorithm in detecting children who need renal replacement therapy. We evaluated two cohorts of children. Group I included single-center data from 626 ¹²⁵I-iothalamate clearance studies (C_IO) that were compared with the simultaneous estimation of GFR by C_SCH. Group II included data on 659 children from the patient incidence registry obtained from the ESRD Network of Texas between February 1996 and October 2003. In group I there were 76 children (76 C_IO) with C_SCH less than 20 ml/min per 1.73 m² of whom 50 (67%) had C_IO less than 15 ml/min per 1.73 m². Of children with C_IO less than 15 ml/min per 1.73 m², 62% had a C_SCH less than 20 ml/min per 1.73 m². The ability of C_SCH greater than 20 ml/min per 1.73m² to predict C_IO greater than 15 ml/min per 1.73 m² (negative predictive value) is 0.95. The number of children who were started on dialysis in Texas within the study period was 659 (group II). The mean C_SCH±SD was 10.8±7.7 ml/min per 1.73 m². Of the patients who were initiated on dialysis, 94% had C_SCH less than 20 ml/min per 1.73 m². The results were sustained when race, gender, age range, and type of diagnosis were considered. The new CMS algorithm provides a good negative predictive estimate of GFR less than 15 ml/min per 1.73 m². Disclaimer The analyses upon which this publication is based were performed under contract number 500–03-NW14 entitled End-Stage Renal Disease Networks Organization for the State Texas, sponsored by the Centers for Medicare and Medicaid Services, Department of Health and Human Services. The content of this publication does not necessarily reflect the views or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government. The authors assume full responsibility for the accuracy and completeness of the ideas presented. This article is a direct result of the Health Care Quality Improvement Program initiated by the Centers for Medicare and Medicaid Services, which has encouraged identification of quality improvement projects derived from analysis of patterns of care, and therefore required no special funding on the part of this contractor. Ideas and contributions to the author concerning experience in engaging with issues presented are welcomed.