Summary

Background and objective: Cardiopulmonary bypass is associated with changes of intra- and extravascular volume status often resulting in cardiopulmonary dysfunction. The purpose of this prospective double-blind study was to evaluate the influence of different priming solutions of the extracorporeal circuit on intra- and extravascular volume status and haemodynamics in patients undergoing elective mitral valve replacement. Methods: Twenty-two patients with mitral valve insufficiency were randomly allocated into two equal groups. In Group 1 cardiopulmonary bypass was primed with a nearly isooncotic solution consisting of 4% albumin. The second group received a pure crystalloid priming solution. The thermo-dye indicator dilution technique was used for the assessment of cardiac output, central and pulmonary blood volume, right ventricular end-diastolic volume and total blood volume. Results: Patients in the crystalloid group showed increased intraoperative fluid requirements. Significantly more fluid was accumulated in the extravascular space whereas total blood volume was decreased after surgery. Stroke volume index (SVI) was significantly decreased in the immediate postoperative period when compared to baseline. As indicated by the increase in extravascular fluid content after surgery, both colloid and crystalloid priming volumes were transferred to the extravascular space. Conclusion: The use of colloid priming solutions in patients with mitral valve insufficiency leads to less fluid requirements and significantly reduced fluid shift in the interstitium. However, these changes are not associated with changes in haemodynamic parameters or short term outcome.

Summary

Background and objective: To determine the minimal oxygen delivery and pump flow that can maintain systemic oxygen uptake during normothermic (37°C) pulsatile and non-pulsatile cardiopulmonary bypass in dogs. Methods: Eighteen anaesthetized dogs were randomly assigned to receive either non-pulsatile (Group C; n = 9) or pulsatile bypass flow (Group P; n = 9). Oxygen delivery was reduced by a progressive decrease in pump flow, while arterial oxygen content was maintained constant. In each animal, critical oxygen delivery was determined from plots of oxygen uptake vs. oxygen delivery and from plots of blood lactate vs. oxygen delivery using a least sum of squares technique. Critical pump flow was determined from plots of lactate vs. pump flow. Results: At the critical point, oxygen delivery obtained from oxygen uptake was 7.7 ± 1.1 mL min−1 kg−1 in Group C and 6.8 ± 1.8 mL min−1 kg−1 in Group P (n.s.). These values were similar to those obtained from lactate measurements (Group C: 7.8 ± 1.6 mL min−1 kg−1; Group P: 7.6 ± 2.0 mL min−1 kg−1). Critical pump flows determined from lactate measurements were 55.6 ± 13.8 mL min−1 kg−1 in Group C and 60.8 ± 13.9 mL min−1 kg−1 in Group P (n.s.). Conclusions: Oxygen delivery values greater than 7–8 mL min−1 kg−1 were required to maintain oxygen uptake during normothermic cardiopulmonary bypass with either pulsatile or non-pulsatile blood flow. Elevation of blood lactate levels during bypass helps to identify inadequate tissue oxygen delivery related to insufficient pump flow.

Summary

Background and objective: Acute renal failure is a serious complication of cardiac surgery. We studied the long-term survival and quality of life of patients requiring renal replacement therapy after cardiac surgery, since they represent a heavy burden on hospital resources and their outcome has never been adequately evaluated. Methods: Out of 7846 consecutive cardiac surgical patients, 126 (1.6%) required postoperative renal replacement therapy: their preoperative status and hospital course was compared with patients who had no need of postoperative renal replacement therapy. A multivariate analysis identified predictors of renal replacement therapy. Long-term survival and quality of life was collected in patients who had renal replacement therapy and in case-matched controls. Results: Hospital mortality in the study group was 84/126 (66.7%) vs. 118/7720 (1.5%) in the control population (P < 0.001). Patients who underwent renal replacement therapy and were discharged from the hospital (42 patients) had a reasonable long-term outcome: at 42 ± 23 months, 30 out of 42 patients were alive, with only 3 patients complaining of limitations in daily activities. Predictors of in-hospital renal replacement therapy were: emergency surgery, preoperative renal impairment, intra-aortic balloon pumping, reoperation for bleeding, previous cardiac surgery, female gender, low ejection fraction, bleeding >1000 mL, chronic obstructive pulmonary disease and age. Conclusions: This study confirms that the in-hospital mortality of patients requiring renal replacement therapy is high and shows a low long-term mortality with reasonable quality of life in patients discharged from hospital alive.

Summary

Background and objective: Despite the introduction of various less-invasive concepts of cardiac output measurement, pulmonary arterial thermodilution is still the most common measurement technique. Methods: This prospective controlled study was designed to compare different methods of cardiac output measurement simultaneously. Pulmonary arterial thermodilution, transpulmonary thermodilution (PiCCO™), trans-oesophageal echo-Doppler probe (HemoSonic™) and partial carbon dioxide rebreathing technique (NICO™ monitor) were evaluated against a peri-aortic transit-time flow-probe as reference method in a clinically relevant animal model. After approval from the Local Ethics Committee on Animal Research, the investigations were conducted in nine anesthetized domestic pigs. Systemic haemodynamics were modulated systematically by the application of catecholamines, caval occlusion and exsanguination. Statistical analysis was performed with Bland–Altman and linear regression. Results: A total of 366 paired cardiac output measurements were carried out at a reference cardiac output between 0.5 and 7 L min−1. The correlation coefficients for pulmonary arterial and transpulmonary thermodilution against reference were 0.93 and 0.95, for trans-oesophageal Doppler and partial rebreathing technique 0.84 and 0.77. Pulmonary arterial thermodilution and transpulmonary thermodilution showed comparable bias and limits of agreement. Where HemoSonic™ showed an overestimation of cardiac output at a higher precision, NICO™ overestimated low and underestimated higher cardiac output values. Conclusions: Our data suggest that pulmonary arterial thermodilution and PiCCO™ may be interchangeably used for cardiac output measurement even under acute haemodynamic changes. The method described by Bland and Altman demonstrated an overestimation of cardiac output for both thermodilution methods. HemoSonic™ and NICO™ offer non-invasive alternatives and complementary monitoring tools in numerous clinical situations. Trend monitoring and haemodynamic optimizing can be applied sufficiently, when absolute measures are judged critically in a clinical context. The use of the NICO™ system seems to be limited during acute circulatory changes.

Summary

Background and objectives: During partial liquid ventilation perfluorocarbons are instilled into the airways from where they subsequently evaporate via the bronchial system. This process is influenced by multiple factors, such as the vapour pressure of the perfluorocarbons, the instilled volume, intrapulmonary perfluorocarbon distribution, postural positioning and ventilatory settings. In our study we compared the effects of open and closed breathing systems, a heat-and-moisture-exchanger and a sodalime absorber on perfluorocarbon evaporation during partial liquid ventilation. Methods: Isolated rat lungs were suspended from a force transducer. After intratracheal perfluorocarbon instillation (10 mL kg−1) the lungs were either ventilated with an open breathing system (n = 6), a closed breathing system (n = 6), an open breathing system with an integrated heat-and-moisture-exchanger (n = 6), an open breathing system with an integrated sodalime absorber (n = 6), or a closed breathing system with an integrated heat-and-moisture-exchanger and a sodalime absorber (n = 6). Evaporative perfluorocarbon elimination was determined gravimetrically. Results: When compared to the elimination half-life in an open breathing system (1.2 ± 0.07 h), elimination half-life was longer with a closed system (6.4 ± 0.9 h, P < 0.01), a sodalime absorber (5.0 ± 0.6 h, P < 0.01) or a heat-and-moisture-exchanger (4.5 ± 0.8 h, P < 0.01). The combination of all three methods (7.1 ± 0.8 h) showed no significant additional effects (P > 0.05) when compared to a closed system. Conclusions: Evaporative perfluorocarbon loss can be reduced effectively with closed breathing systems, followed by the use of sodalime absorbers and heat-and-moisture-exchangers.

Summary

Introduction: We decided to investigate the pathogenesis of pulmonary ventilatory and radiographic abnormalities in patients after major vascular surgery. Patients and methods: Sixteen mechanically ventilated patients without heart failure were studied, within 3 h after major abdominal surgery. We measured extravascular lung water, intrathoracic, global end-diastolic and pulmonary blood volumes, 67Ga-transferrin pulmonary leak index and ventilatory and radiographic variables. The latter allowed computation of the lung injury score as a measure of lung injury. Results: The extravascular lung water was elevated (>7 mL kg−1) in 5 of 16 patients, while the pulmonary leak index was elevated in 11 patients and a supranormal extravascular lung water was associated with a high pulmonary leak index and higher extravascular lung water relative to intrathoracic blood volume or pulmonary blood volume. Patients were arbitrarily divided into those with a lung injury score >1 and ≤1, and only differed in the factors composing the score as well as in extravascular lung water divided by pulmonary blood volume. A lung injury score >1 was associated with a longer duration of mechanical ventilation. Conclusion: Our data suggest that mild, subclinical, pulmonary oedema is relatively common after major vascular surgery, mainly caused by increased pulmonary capillary permeability in the absence of overt heart failure. However, permeability oedema only partially contributes to postoperative lung injury score and need for mechanical ventilation, suggesting a major contribution by atelectasis.

Summary

Background and objective: The optimal depth of insertion of left-sided double-lumen endobronchial tubes is strongly correlated with body height in average-sized adults. However, this relationship has not been studied in below average-sized adult patients. We investigated whether or not there is a clinically useful relationship in below average-sized adult patients. Methods: One hundred and ninety six consecutive adult patients undergoing thoracic surgery under one-lung anaesthesia (body height ≤ 155 cm) were included in this study. Left-sided double-lumen tubes were inserted under the guidance of a fibre-optic bronchoscope. Optimal depth was defined as the proximal surface of the bronchial cuff positioned just below the carina. Results: There was a statistically significant positive correlation between body height and the optimal depth of insertion (r = 0.61, P < 0.0001); however, the correlation coefficient was low. The actual optimal depth of insertion of one patient was even 4.5 cm shorter than that obtained from the equation. Conclusion: Although there was a statistically significant correlation between body height and the optimal depth of insertion of left sided double lumen tubes in adult patients of short stature (≤ 155 cm), clinical application of the equation is not warranted and these tubes should be inserted under direct vision with a fibre-optic bronchoscope.

Summary

Background and objective: Different types of polymer surfaces affect the activation of platelets and coagulation pathway containers depending on their surface qualities. Importantly, this could produce variability of coagulation results obtained with thrombelastographical analysis. We assessed the effects of blood storage on thrombelastograph, TEG®, variables using polypropylene and polycarbonate containers. Methods: An in vitro experiment was performed, with eight volunteers in each limb. Fresh whole blood was stored in polypropylene or polycarbonate tubes prior to TEG® analysis, to assess the role of these plastics in the TEG® results obtained. Results: The polycarbonate tubes displayed slower onset of coagulation and greater variability of data for all four basic TEG variables (r-time, k-time, α-angle and maximum amplitude, P < 0.05). Polycarbonate results fell outside manufacturer reference ranges. Conclusions: It is likely that this is due to the altered surface properties and charge effects of the containers affecting proteins and platelets differently. Caution should be used in choosing which containers are used for storage of fresh blood prior to coagulation assessment, as variable results will follow where different types of plastic containers are employed.

Summary

Background and objective: The reasons for coagulopathy may be multiple and the identification of the underlying cause is often difficult. Recently, we identified two patients showing characteristics of heparin overdose during surgery. We hypothesised that filling a Shaldon dialysis catheter with heparin prior to closure, so-called heparin lock, might have triggered this coagulation disorder. Therefore, the aim of this in vitro study was to show whether this procedure can lead to an iatrogenic administration of heparin. Methods: A Shaldon catheter (GamCath®; Joka Kathetertechnik, Hechingen, Germany) was hung up in a container filled with NaCl solution 0.9% 5 mL and a heparin lock was simulated. Instead of using heparin solution we injected 1 mL of a KCl solution (1 mol L−1) into the Shaldon catheter, because the measurement of the potassium concentration is faster and more reliable than that of heparin. Ten measurements were taken after fast (0.5 s) and slow (3 s) injection speeds. Results: Although the catheter volume is specified as 1.07 mL, an amount up to 0.51 mL KCl solution on average was detectable in the solution after locking the catheter with 1 mL KCl solution. Conclusions: Following a heparin lock a considerable amount of the injected solution is accidentally administered to the patient. Only 49.1% of the injected volume may remain in the Shaldon catheter. This could lead to an increased risk of coagulopathy.

Summary

Background and objective: Magnesium administered before anaesthesia induction results in a significant reduction in intravenous anaesthetic consumption. The purpose of this study was to evaluate whether the dose of intravenous magnesium sulphate reduces the minimum alveolar anaesthetic concentration of sevoflurane for endotracheal intubation (MACEI) and skin incision (MAC), and attenuates haemodynamic responses. Methods: We studied 60 patients who were scheduled for elective surgery. Patients were not premedicated before induction of anaesthesia and were randomly assigned to receive intravenous saline 0.9% (Group I, n = 20) or magnesium sulphate 30 mg kg−1 bolus + 10 mg kg−1 h−1 continuous infusion (Group II, n = 20) or 50 mg kg−1 bolus + 10 mg kg−1 h−1 continuous infusion (Group III, n = 20). Results: Median and 95% confidence limits for sevoflurane MACEI were 2.68 (2.48–2.85), 2.88 (2.70–3.06) and 2.96 (2.70–3.16), and for sevoflurane MAC were 2.08 (1.76–2.40), 2.26 (2.08–2.47) and 2.40 (2.19–2.68) in Groups I, II and III, respectively. The differences in MACEI and MAC among groups were not statistically significant, except Group III in MAC study (P < 0.05). Mean arterial pressures and heart rate did not increase in Groups II and III after endotracheal intubation and skin incision. Conclusions: Magnesium sulphate administered before induction of anaesthesia increases MAC of sevoflurane and reduces cardiovascular responses to intubation.

Summary

Background and objective: Low flow desflurane and sevoflurane anaesthesia were administered to children and compared for haemodynamic response, renal and hepatic function, recovery time and postoperative nausea and vomiting. Methods: Eighty ASA I–II patients aged 5–15 yr were included in the study. Midazolam was given for premedication. Anaesthesia induction was performed with fentanyl, propofol and atracurium. After intubation, the first group received desflurane, oxygen and nitrous oxide at 6 L min−1 and the second sevoflurane, oxygen and nitrous oxide at 6L min−1. Ten minutes after induction the flow was decreased to 1L min−1 in both groups. Haemodynamic parameters, preoperative and postoperative renal and hepatic function, the times of operation and anaesthesia, and early recovery data were recorded. Modified Aldrete scores were noted at the 10th and 30th minutes postoperatively and postoperative nausea, and vomiting were assessed. Results: There were no significant differences in haemodynamic parameters, renal and hepatic functions, postoperative recovery and postoperative nausea and vomiting between groups. The recovery time was shorter in the desflurane group compared to the sevoflurane group. Conclusion: Low flow desflurane and sevoflurane anaesthesia do not adversely affect haemodynamic parameters, hepatic and renal function in children. Desflurane may be preferred when early recovery from anaesthesia is warranted.

Summary

Background and objective: The cyclic guanosine monophosphate level, which causes an antinociception, is increased in cells as a direct result of phosphodiesterase inhibition. This study used a nociceptive test to examine the nature of the pharmacological interaction between intrathecal zaprinast, a phosphodiesterase inhibitor, and morphine. Methods: Catheters were inserted into the intrathecal space through an incision in the atlantooccipital membrane of male Sprague–Dawley rats. As a nociceptive model, 50 μL of a 5% formalin solution was injected into the hind paw. After observing the effect of zaprinast (37, 111, 369 nmol) and morphine (1, 4, 10, 40 nmol) alone, the interactions of their combination were examined by an isobolographic analysis. Results: Intrathecal zaprinast (P < 0.05) and morphine (P < 0.05) dose-dependently suppressed the flinching observed during phase 1 and phase 2 in the formalin test. The ED50 values (95% confidence intervals) of zaprinast and morphine in phase 1 were 161.9 (87.9–298.3) and 11.6 nmol (4.8–27.9 nmol), respectively. The phase 2 ED50 values (95% confidence intervals) of zaprinast and morphine were 229.9 (142.5–370.9) and 3.9 nmol (1.9–7.6 nmol), respectively. Isobolographic analysis revealed a synergistic interaction after intrathecal delivery a zaprinast–morphine mixture in both phases. The ED50 values of (95% confidence intervals) zaprinast in the combination of zaprinast with morphine in phase 1 and phase 2 were 14.2 (4.9–40.6) and 10.4 nmol (3–35.9 nmol), respectively. Conclusions: Intrathecal zaprinast and morphine are effective against acute pain and facilitated pain state. Zaprinast interacts synergistically with morphine.

Summary

Background and objective: The modified Airway Management Device (AMD) and the Proseal laryngeal mask airway (PLMA) are both supraglottic airway devices designed to maintain airway patency and allow ventilation during anaesthesia. In this prospective, randomized trial, we compared the two devices in patients undergoing major gynaecological procedures. Methods: Eighty-two patients undergoing elective gynaecological surgery were randomized to two groups. Group A (n = 41) had the AMD and Group P (n = 41) the PLMA inserted after induction of anaesthesia. We compared the success of airway placement, time to achieve an airway, oropharyngeal leak pressure and complications associated during anaesthesia. Results: There were no differences in patient characteristic profile for both groups. First time insertion success rates were significantly higher in Group P than in Group A (100% vs. 83%, P < 0.012). Time taken to achieve airway was also significantly shorter in Group P than in Group A (mean 21.9 ± 7.8 s vs. 40.2 ± 48.0 s, P < 0.001). The oropharyngeal leak pressure was significantly higher for Group P than Group A (mean 31.2 ± 5.7 cmH2O vs. 24.2 ± 8.3 cmH2O, P < 0.001). Ten patients in Group A had transient loss of airway during anaesthesia and needed manipulation of the airway device and four patients needed to have the airway switched to PLMA for the rest of the procedure. Conclusions: The modified AMD has a significant lower first time successful placement rate, required a longer insertion time and has a lower oropharyngeal leak pressure than the PLMA. It also demonstrated an increased loss of airway during anaesthesia. The modified AMD needs further evaluation on its efficacy and safety before its further use can be recommended.

Summary

Background and objective: We tested the feasibility of using the intubating laryngeal mask airway Fastrach™ (ILMA) as a ventilatory device and for flexible lightwand-guided tracheal intubation for out-of-hospital cardiopulmonary resuscitation by an emergency physician. Methods: After completion of a training programme, a single experienced emergency physician used the technique for all patients requiring out-of-hospital tracheal intubation over a 10-month period. If access to the head and neck was limited, the intubating laryngeal mask airway was inserted from below and to the side, otherwise it was inserted from above the head. Data about the time for the ambulance to reach the patient, whether or not access to the head and neck was limited, whether or not circulation was successfully restored, and the insertion and intubation success rates were noted. Results: The mean (range) time for the ambulance to reach the patient was 12 (10–20) min. Access to the head and neck was limited in 8/37 (22%). Circulation was successfully restored in 10/37 (27%). The intubating laryngeal mask airway was successfully inserted at the first attempt in 35/37 (95%) and at the second attempt in 2/37 (5%). The tracheal tube was successfully inserted in 25/37 (67.5%) at the first attempt, 7/37 (19%) at the second attempt and 5/37 (13.5%) at the third attempt. There were no overall failures for intubating laryngeal mask airway insertion or tracheal intubation. There were no differences in success rate between positions. Oesophageal intubation was detected and corrected in 2/37 (5%). Conclusion: The intubating laryngeal mask airway has a high success rate as a ventilatory device and as a flexible lightwand-guided airway intubator during out-of-hospital cardiopulmonary resuscitation by a well-trained emergency physician. This technique may be particularly useful when there is limited access to the head and neck.