Auswirkungen von Dopexamin Transpulmonales Shuntvolumen bei thorax- chirurgischen Eingriffen mit Ein-Lungen-Beatmung

Objective: To study the influence of dopexamine on pulmonary shunt and hypoxic pulmonary vasoconstriction during major thoracic surgery with one-lung ventilation (OLV). Design: Prospective, randomised, placebo-controlled study. Setting: University hospital. Patients: Twenty adult patients undergoing elective pulmonary resection. Anaesthesia: General anaesthesia was performed using propofol, fentanyl, N₂O and vecuronium.Volume-controlled ventilation was performed to maintain normocapnia over the whole investigation period. During OLV, the tidal volume was reduced and the respiratory rate was increased to avoid a peak airway pressure exceeding 40 cm H₂O. Furthermore the FiO₂ was increased to 1,0 and the external PEEP was removed during OLV. Interventions: The patients received either dopexamine at 2 µg/kg/min (group A, n=10) or 0,9% saline as control (group B, n=10) after assessing the baseline values. Measurement and results: The following cardiorespiratory variables were recorded: Heart rate, mean arterial pressure and mean pulmonary arterial pressure. Cardiac output was measured by thermodilution using a continuous cardiac output thermodilution catheter. Arterial and mixed venous blood gas analysis were measured from simultaneously drawn samples. Cardiac index (CI), systemic vascular resistance index, pulmonary vascular resistance index, oxygen delivery index (DO₂I), oxygen consumption index and the venous admixture were calculated using standard formula. Furthermore, pressure-flow-curves were constructed to analyse flow independent changes in the pulmonary vascular resistance. Data were recorded at the following times: After induction of anaesthesia in stable haemodynamics during two-lung ventilation (baseline values, T0), intraoperatively during one-lung ventilation (T1) and postoperatively after re-establishing two-lung ventilation (T2). Patients characteristics, data from the preoperative lung function testing and surgical procedures did not differ significantly between the groups. CI increased in the dopexamine group from 2,5±1,2 l·min^?1·m^?2 (T0) to 3,6±0,9 l·min^?1·m^?2 (T1) and 4,0±1,3 l·min^?1· m^?2 (T2). The course of the intrapulmonary right-to-left shunting did not differ between the groups. In the dopexamine-treated group the DO₂I increased from 430±143 ml·min·m^?2 (T0) to 652±255 ml·min·m^?2 (T1) and 653±207 ml·min·m^?2 (T2). Regarding the pressure-flow-curves there was no difference during OLV between the two groups indicating no major blocking effect of dopexamine on hypoxic pulmonary vasoconstriction. Conclusion: It is concluded that dopexamine can be used to improve haemodynamics and oxygen delivery during thoracic surgery without increasing venous admixture during one-lung ventilation.     

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.     

Hemodynamic effects of dobutamine and dopexamine after cardiopulmonary bypass in pediatric cardiac surgery*

Background: After surgical repair of congenital heart disease, inotropic support is sometimes necessary to wean from cardiopulmonary bypass. In pediatric cardiac surgery, dobutamine and dopamine are often used as inotropic support. Dopexamine is a synthetic catecholamine, which has positive inotropic and vasodilating properties. Because the hemodynamic effects of catecholamines are modified after cardiopulmonary bypass, the aim of this study was to investigate the effects of dobutamine and dopexamine on cardiac index and systemic vascular resistance index after cardiopulmonary bypass in pediatric cardiac surgery. Methods: The study was performed in a prospective, randomized, and double‐blinded cross‐over design. The investigation included 11 children for elective, noncomplex congenital heart surgery. After weaning from cardiopulmonary bypass and a 20‐min period of steady state, children received either 2.5 μg·kg^?1·min^?1 dobutamine or 1 μg·kg^?1·min^?1 dopexamine for 20 min. Cardiac index (transpulmonary thermodilution), mean arterial pressure, central venous pressure, stroke volume, systemic vascular resistance, and central venous oxygen saturation were determined. The primary outcome variable was cardiac index. Results: No difference in cardiac index was observed between the two groups (P = 0.594). Both drugs increased cardiac index, dopexamine from 3.9 ± 0.6 to 4.7 ± 0.8 l·min^?1·m^?2 (P = 0.003) and dobutamine from 4.1 ± 0.7 to 4.8 ± 0.7 l·min^?1·m^?2 (P = 0.004). During treatment with dobutamine, children presented with significantly higher mean arterial pressure (P = 0.003) and systemic vascular resistance index (P = 0.026). Conclusions: This trial demonstrates that low‐dose dobutamine and dopexamine both increase cardiac index during pediatric cardiac surgery but with different hemodynamic effects.     

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.     

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.     

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.     

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.     

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.     

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.     

Arrhythmogenic potential of dopexamine hydrochloride during halothane anaesthesia in dogs

Dopexamine hydrochloride (Dopacard®) is the novel synthetic catecholamine designed for use in the acute management of a low cardiac output status. In addition to dopaminergic receptor stimulation, dopexamine hydrochloride is a potent β₂ adrenoreceptor agonist with negligible direct β₁ and no alpha adrenergic effect. The objective of this study was to compare the arrhythmogenic effects of dopexamine hydrochloride and dopamine in dogs anaesthetized with halothane (1.2 MAC). The starting dose for dopexamine hydrochloride was 3.5 μg · kg^?1 min^?1 and for dopamine was 5 μg · kg^?1 min^?1. Concentrations of the drugs were increased until four or more premature ventricular contractions within 15 seconds were produced. All dogs developed ventricular tachycardia when dopamine was administered in concentrations ranging between 18–20 μg · kg^?1 · min^?1. Unlike dopamine, dopexamine hydrochloride even at concentrations as high as 50 μg · kg^?1· min^?1 did not induce any atrial or ventricular ectopic beats. Lack of β_-1 and alpha adrenergic agonist effects is a likely explanation for low arrhythmogenicity of dopexamine hydrochloride. Both drugs increase cardiac output; dopexamine hydrochloride primarily by a dose-related increase in heart rate and increased aflerload. At the maximal concentration dopexamine hydrochloride increased heart rate from 114 to 150 beat · min^?1, mean arterial pressure decreased from 81 mmHg to 45 mmHg and SVR decreased from 2418 to 962 dyne · sec^?1cm^?5. Myocardial contractility increased only moderately, as evaluated by dP/dt, which increased from 1290 to 1696 mmHg · sec^?1. Dopamine had a more marked inotropic effect: the dP/dt increased, at the maximal concentration, from 1480 to 2570 mmHg · sec^?1. Dopamine also produced vasoconstriction: SVR increased from 2325 to 2683 dyne · sec · cm^?5 and mean arterial pressure from 86 mmHg to 110 mmHg. In conclusion, dopexamine hydrochloride is less arrhythmogenic than dopamine, has less of an inotropic effect, and a greater effect on aflerload.     

Clinical evaluation of low-flow sevoflurane anaesthesia for paediatric patients

Background: Sevoflurane expenditure, inspired gas humidity, temperature, soda lime temperature, and compounds A and B were measured during high and low fresh gas flow anaesthesia in paediatric patients. Methods: Sixty ASA 1 or 2 paediatric patients were randomly allocated to two groups: low-flow circle anaesthesia (LFA) patient group (n=30) and high-flow circle anaesthesia (HFA) patient group (n=30). Initial fresh gas flow (FGF) was 4 l · min^?1 of nitrous oxide and 2 l · min^?1 of oxygen in both groups. This FGF of 6 l · min^?1 was maintained in the HFA group. After 10 min of HFA, the FGF was reduced to 600 ml · min^?1 (nitrous oxide and oxygen 300 ml · min^?1 each) in the LFA group. Results: Sevoflurane expenditure during LFA was about 1/7 of that during HFA (3.3±0.2 ml · h^?1 · vol.%^?1 compared to 22.8±0.6 ml · h^?1 · vol.%^?1, mean±SEM, respectively). Absolute humidity in the LFA patients was 4 times higher than that in the HFA patients (22.8±2.4 g · m^?3, 5.6±3.4 g · m^?3 respectively). There was no significant difference in the inspiratory gas temperature between the LFA (28.5±0.6°C) and HFA (26.9±1.3°C) groups. There was significant difference in the mean highest soda lime temperature between the LFA (35.5±1.2°C) and HFA (28.7±1.2°C) groups. The mean highest concentration of compound A was 12.2±3.8 ppm in the LFA group. The mean highest concentration of compound B was less than 1 ppm. Compounds A and B were below detectable level in the HFA group. Conclusion: In conclusion, sevoflurane used for paediatric patients in a circle system with a fresh gas flow of 0.6 l · min^?1 resulted in a significantly reduced sevoflurane expenditure, higher inspired absolute humidity, but not temperature, compared to a fresh gas flow of 6 l · min^?1. Low levels of compounds A and B were detected.     

Postoperative patientcontrolled epidural analgesia with opioid bupivacaine mixtures

Purpose

To determine the efficacy and safety of patient-controlled epidural analgesia of morphine or fentanyl in combination with bupivacaine for postoperative pain relief.

Methods p]Forty ASA 1–11 patients scheduled for major abdominal surgery were studied. After insertion of a lumbar epidural catheter, patients were given a non-opioid general anaesthetic. After surgery patients complaining of pain, received a loading dose of 2 mg morphine (Group I) or 50 μg fentanyl (Group II). For continuing pain, 1 mg morphine in 4 ml bupivacaine 0.125% (0.25 mg·ml^?1 morphine and 1 mg·ml^?1 bupivacaine, Group I) or 20 μg fentanyl in 4 ml bupivacaine 0.125% (5 μg·ml^?1 fentanyl and 1 mg·ml^?1 bupivacaine Group II) were administered. Blood pressure, heart rate, respiratory rate and SpO₂ were monitored. Assessments of pain (VAS), nausea-vomiting, motor block, pruritus and sedation were recorded for 24 hr.

Results

No difference in pain or sedation was observed between groups, The 24 hr postoperative opioid consumption was 15.50 ± 7.53 mg morphine and 555.10 ± 183.85μg fentanyl. Total bupivacaine 0.125% consumption was 58.00 ± 30.14 ml in Group I and 101.05 ± 36.77 ml in Group II. One patient in Group II complained of motor weakness in one leg. The incidence of nausea (Group I 45%, Group II 10%P < 0.05) and pruritus (Group I 30%, Group II 5%P < 0.05) was less in patients receiving fentanyl. Conclusion: Both methods were effective in the prevention of pain but, because of fewer side effects, fentanyl may be preferable to morphine.     

The effects of cardiopulmonary bypass on postoperative oxygen metabolism

The relationships between oxygen delivery (DO₂), oxygen consumption (VO₂), and the extraction rate (ER=VO₂/DO₂x100) in patients undergoing cardiopulmonary bypass (CPB) may differ from the normal physiologic state due to the oxygen debt acquired during CPB. Blood gas analysis and hemodynamic parameters were repeatedly measured for the determination of DO₂ and VO₂ in 40 patients undergoing CPB, every 8h during the first 48h postoperatively. As a control, 20 patients who had suffered acute myocardial infarction (AMI) were also studied using the same protocol. In the CPB group, a regression analysis showed that VO₂ was significantly dependent on DO₂, even within the physiologic range of DO₂ (>500 ml/min per m²); VO₂=121.4+0.0844×DO₂ (r=0.254,P=0.023). Conversely, in the AMI group, no such supply-dependent consumption was observed within the same range of DO₂. At an ER of 30%, which is the optimal value in general, the DO₂ of the CPB group was 575 ml/min per m² and that of the AMI group was 493 ml/min per m². All these results suggest that patients undergoing CPB need a much higher oxygen supply to recover from the oxygen debt acquired during open heart surgery.     

Epidural and intravenous bolus morphine for postoperative analgesia in infants

Purpose

To compare two doses of bolus epidural morphine with bolus iv morphine for postoperative pain after abdominal or genitourinary surgery in infants.

Methods

Eighteen infants were randomly assigned to bolus epidural morphine (0.025 mg · kg^?1 or 0.050 mg · kg^?1) or bolus iv morphine (0.050–0.150 mg · kg^?1). Postoperative pain was assessed and analgesia provided, using a modified infant pain scale. Monitoring included continuous ECG, pulse oximetry, impedance and nasal thermistor pneumography. The CO₂ response curves and serum morphine concentrations were measured postoperatively.

Results

Postoperative analgesia was provided within five minutes by all treatment methods. Epidural groups required fewer morphine doses (3.8 ± 0.8 for low dose [LE], 3.5 ± 0.8 for high dose epidural [HE] vs. 6.7 ± 1.6 for iv, P < 0.05) and less total morphine (0.11 ± 0.04 mg · kg^?1 for LE, 0.16 ± 0.04 for HE vs 0.67 ± 0.34 for iv, P < 0.05) on POD1 Dose changes were necessary in all groups for satisfactory pain scores. Pruritus, apnoea, and haemoglobin desaturation occurred in all groups. CO₂ response curve slopes, similar preoperatively (range 36–41 ml · min^?1 · mmHg ETco ₂ ^?1 · kg^?1) were generally depressed (range, 16–27 ml · min^?1 · mmHg ETco ₂ ^?1 · kg^?1) on POD1. Serum morphine concentrations, negligible in LE (<2 ng · ml^?1), were similar in the HE and iv groups (peak 8.5 ± 12.5 and 8.6 ± 2.4 ng · ml^?1, respectively).

Conclusion

Epidural and iv morphine provide infants effective postoperative analgesia, although side effects are common. Epidural morphine gives satisfactory analgesia with fewer doses (less total morphine); epidural morphine 0.025 mg · kg^?1 is appropriate initially. Infants receiving epidural or iv morphine analgesia postoperatively need close observation in hospital with continuous pulse oximetry.     

Optimizing sedation following major vascular surgery: a double-blind study of midazolam administered by continuous infusion

A randomized, double-blind study was undertaken to determine the dose requirements, recovery characteristics, and pharmacokinetic variables of midazolam given by continuous infusion for sedation in patients following abdominal aortic surgery. Thirty subjects, 50–75 yr, scheduled to undergo aortic reconstructive surgery, entered the study. Following a nitrous oxide-isoflurane-opioid anaesthetic technique, patients were randomly allocated to receive one of three loading doses (0.03, 0.06 or 0.1 mg · kg^?1) and initial infusion rates (0.5, 1.0 or 1.5 μg · kg^?1 · min^?1) of midazolam, corresponding to groups low (L), moderate (M) and high (H). The infusion of midazolam was adjusted to maintain sedation levels of “3, 4 or 5,“ which permitted eye opening in response to either verbal command or a light shoulder tap, using a seven-point scale ranging from “0” (awake, agitated) to “6” (asleep, non-responsive). Additionally, morphine was given in increments of 2.0 mg iv prn for analgesia. On the morning after surgery, midazolam was discontinued, and the tracheas were extubated when patients were awake. Blood samples were taken during, and at increasing intervals for 48 hr following discontinuation of the infusion, and analyzed by gas chromatography. The desired level of sedation was maintained during more than 94% of the infusion period in all three groups, with a maximum of three dose adjustments per patient, for treatment which lasted 16.3 ± 0.6 hr. There was, however, an increase in both the infusion rates and mean plasma concentrations from Group L to Group H (P < 0.05), which corresponded to an inverse relationship of morphine requirements during the period of sedation (P < 0.05, Group H vs Group L). Optimal midazolam infusion rates and resulting plasma concentrations at the times the infusions were discontinued (in parentheses) were as follows — Group L: 0.60 ± 0.18 μg · kg^?1 min^?1 (76 ± 32 ng · mL^?1), Group M: 0.90 ± 0.52 μg · kg^?1 · min^?1 (133 ± 71 ng · mL^?1), and Group H: 1.34 ± 0.69 μg · kg^?1 · min^?1 (206 ± 106 ng · mL^?1). Times to awakening were longer in Group H: 3.1 ± 3.4 hr, than in Group L: 1.1 ± 0.8 h, P < 0.05. Pharmacokinetic variables were found to be dose- independent over the range of infusion rates. Mean values were t_1/2β = 4.4 ± 1.5 hr, CL = 5.94 ± 1.69 mL · min^?1 · kg^?1, Vd = 3.13 ± 1.07 L · kg^?1. It is concluded that midazolam, infused between 0.6–0.9 μg · kg^?1 · min^?1, provides a stable level of sedation, when administered in conjunction with intermittent iv morphine following AAS. This sedation technique, which costs $1.65 ± 0.73 hr^?1 ($Can), is associated with rapid recovery and minimal side effects.     

The evaporative water loss from burns and the water-vapour permeability of grafts and artificial membranes used in the treatment of burns

The evaporative water loss from burns, granulating wounds and donor sites was calculated from measurements of the vapour-pressure gradient of the air layer close to the skin. Soon after burning the mean value and s.e. mean for the rate of evaporation from partial- and full-thickness burns was 178·1 ± 5·5 g m^?2 h^?1 and 143·2 ± 4·5 g m^?2 h^?1 respectively. Uncovered granulating wounds lost water at 214·1 ± 8·4 g m^?2 h^?1, while fresh donor sites during the first postoperative day lost water at 176·0 ± 14·5 g m^?2h^?1, which gradually decreased during the following week to 73·2 ± 12·0 g m^?2 h^?1 as the wound healed.When burned skin was covered with grafts or artificial membranes the evaporative water loss was reduced by a degree depending on the vapour permeability of the cover applied. Compared with the rate of evaporation of water from uncovered tissue, fresh biological dressings reduced the rate of loss by 90 per cent and frozen porcine heterograft skin (Skintec) by 63 per cent. An artificial dressing (Op-Site) reduced the rate of evaporation by 73 per cent while collagen film (Cutycol) and microporous polypropylene film (Epigard) were almost completely permeable to water vapour.     

Methylprednisolone inhibits increase of interleukin 8 and 6 during open heart surgery

It has been reported that interleukin 8 (IL-8) and interleukin 6 (IL-6) are two of the chemical mediators causing myocardial injury. It is not clear whether treatment with corticosteroids in vitro in these patients can prevent the production of interleukin 8 and 6. This prospective study was conducted to investigate whether methylprednisolone (MP) pretreatment (30 mg · kg^?1 before CPB and before declamping of aorta) influenced the production of IL-8 and 6 in the peripheral circulation in 27 patients undergoing elective coronary artery bypass surgery. The IL-8 and IL-6 concentrations were measured by ELISA kit. We also studied the effect of MP pretreatment on postoperative cardiac Junction. Serum concentration of IL-8 in non-MP-treated patients (37 ± 44 pg · ml^?1 preoperatively) increased to 169 ± 86 pg · ml^?1 60 min after declamping of the aorta (P < 0.001). The increase was greater than the increase from 22 ± 8.9 pg · ml^?1 to 52 ± 35 pg · ml^?1 in the MP-treated patients (P < 0.01). Serum IL-6 concentration in non-MP-treated patients increased from the preoperative value of 59 ± 30 pg · ml^?1 to 436 ± 143 pg · ml^?1 60 min after declamping of the aorta (P < 0.001). The increase was greater than the increase from 36 ± 15 pg · ml^?1 to 135 ± 55 pg · ml^?1 in the MP-treated patients (P < 0.01). Furthermore, postoperative cardiac index in MP-treated patients (3.6 ± 1.1 L · min^?1· m^?2) was higher than 2.3 ± 0.8 L · min^?1 · m^?2 of non MP-treated patients (P < 0.05). The levels of IL-8 max during surgery correlated negatively with postoperative cardiac index (γ = ?0.67). These results suggest that methylprednisolone suppresses production of IL-8 and 6.     

Cerebral oxygénation during prostaglandin E1 induced hypotension

Purpose

To evaluate the cerebral oxygenation effects of hypotension induced by prostaglandin E₁(PGE₁) during fentanyl-oxygen anaesthesia.

Methods

Ten patients who underwent elective cardiac surgery received infusion of PGE₁. After measuring the baseline arterial, mixed venous and internal jugular vein blood gases, systemic haemodynamics, and regional cerebral oxygen saturation (rSO₂) estimated by INVOS 3l00^R, PGE₁ was continuously infused at 0.25-0.65 μg·kg^?1·min^?1 (mean dosage: 410 ± 41.4 mg·kg^?1·min^?1) intravenously. Ten, 20 and 30 minutes after the start of drug infusions, blood gases described above were obtained simultaneously with the measurement of systemic haemodynamics and rSO₂. Thirty minutes from the start of drug infusions, administration of PGE₁ was stopped. The same parameters were measured again 10, 30 minutes after the stop of drug infusion.

Results

PGE₁ decreased mean arterial pressure (MAP) to approximately 70% of the baseline value (P < 0.05). PGE₁ increased mixed venous saturation, but in contrast did not effect internal jugular pressure, internal jugular oxygen saturation and rSO₂.

Conclusions

These results suggest that PGE₁ is a suitable drug for induced hypotension because flow/metabolism coupling of brain and regional cerebral oxygenation were well maintained during hypotension.     

Dose-response relationships for edrophonium antagonism of mivacurium-induced neuromuscular block during N2O-enflurane-alfentanil anaesthesia

The purpose of this study was to determine the dose-response relationships for edrophonium antagonism of mivacuriuminduced neuromuscular block. Seventy-five ASA I or II adults were given mivacurium 0.15 mg · kg^{? 1} followed by an infusion (7 μg · kg^{? 1} · min^{? 1}) during alfentanil-propofol-N₂O-enflurane anaesthesia. Train-of-four stimulation (TOF) was applied to the ulnar nerve every 20 sec and the response of the adductor pollicis was recorded (Relaxograph NMT-100. Datex, Helsinki, Finland). Mivacurium infusion was modified at five-minute intervals in order to keep the height of the first twitch in TOF (T₁) at 5% of its control value. At the end of surgery, edrophonium (0.0. 0.125, 0.25, 0.5. or 1.0 mg · kg^{? 1}) combined with glycopyrrolate (0.0, 0.0012, 0.0025, 0.005, or 0.01 mg · kg^{? 1}) were administered by random allocation. Edrophonium doses of 0.25, 0.5 and 1.0 mg · kg^{? 1} were different from placebo with regard to time to attain a TOF ratio (fourth twitch in TOF/ T,) = 0.7 (13.8 ± 4.5, 11.1 ± 3.5, 11.4 ± 3.0 vs 19.7 ± 4.7 min P < 0.05). Doses of 0.5 and 1.0 mg · kg^{? 1} permitted faster recovery time of T₁ from 10 to 95% (T_{10– 95}) than did placebo (7.5 ± 3.8,8.9 ± 3.5 vs 14.5 ± 5.0 min P < 0.05). Edrophonium 0.5 mg · kg^{? 1} was different from placebo with regard to recovery time of T₁ from 25 to 75% (T_{25– 75}) (3.3 ± 2.0 vs 6.7 ± 2.0 min P < 0.05). Only edrophonium 0.5 mg · kg^{? 1} provided faster recovery than placebo with regard to all three indices. It is concluded that edrophonium 0.5 + glycopyrrolate 0.005 mg · kg^{? 1} allow the fastest recovery from a mivacurium-induced block during enflurane-N₂O anaesthesia.     

Pulmonary gas exchange effects by nitroglycerin,dopamine and dobutamine during one-lung ventilation in man

The effects of nitroglycerin, dopamine and dobutamine on pulmonary gas exchange were determined in 21 adult patients during two-lung and one-lung ventilation. Nitroglycerin, in I μg·kg^?1·min^?1, decreased cardiac index (CI) andPaO₂ during both two-and one-lung ventilation, and increased in Qs/Qt during one-lung ventilation. There were no significant changes in the measured variables during infusion of dopamine, 5 μg·kg^?1·min^?1. Dobutamine, 5μg·kg^?1·min^?1, increased Cl and PaO₂ did not change during two-lung ventilation. During one-lung ventilation, PaO₂ increased from (mean value ±SD) 168 ± 46 to 201 ± 52 mmHg (P < 0.01) with dobutamine infusion. Qs/Qt decreased from 29.2 ± 7.0 to 26.0 ± 6.2 per cent (P < 0.05) without any change in pulmonary vascular resistance index during one-lung ventilation. We conclude that dobutamine has advantages over dopamine and nitroglycerin during one-lung ventilation.