Influence of open chest conditions on pulse pressure variations

Objectives

Pulse pressure variations are used to assess fluid responsiveness in mechanically ventilated patients. The accuracy of this index in open chest conditions remained unclear. The aim of the study was to evaluate the effect of open chest conditions on pulse pressure variations.

Study design

Non-interventional prospective study.

Methods and patients

Twenty-eight mechanically ventilated patients scheduled for open-heart surgery were included. Pulse pressure variations, peak aortic velocity, and stroke volume were measured before and after thoracotomy with pericardotomy. Measurements were made at each step and compared.

Results

Neither pulse pressure variation nor peak aortic velocity and nor stroke volume variation were modified by open chest conditions (median = 5% [interquartile range = 6] vs 4% [6], p = NS), (20% [11] vs 17% [12], p = NS and 11% [7] vs 10% [3], p = NS) respectively. Pulse pressure variations were correlated to stroke volume before thoracotomy (r’ = −0.432; p = 0.02) and after thorocatomy (r’ = −0.433, p = 0.02).

Conclusion

In these studied patients, preload dependancy indices were not modified by open chest conditions. Pulse pressure variations remained correlated to stroke volume even after thoracotomy.     

Influence of the analgesic strategy on the respiratory function after thoracic surgery for lobectomy

Objective

To compare the influence of thoracic epidural analgesia (TEA) with intravenous patient-controlled analgesia with morphine (PCA) on the early postoperative respiratory function after lobectomy.

Study design

Prospective and comparative observational study.

Patients and methods

Fourty-four patients scheduled for lobectomy (n = 22 per group) were studied on the evolution of the postoperative respiratory function assessed by the forced vital capacity (FVC) and the forced expired volume (FEV₁) during the first two postoperative days and the analysis of noctural arterial desaturation during the three first postoperative nights.

Results

The use of TEA resulted in fewer decrease both in FEV₁ (1.01 ± 0.34 versus 1.31 ± 0.51 l/s for Day 1, P = 0.03; 1.13 ± 0.37 versus 1.53 ± 0.59 l/s for Day 2, P = 0.01) and in FVC (1.23 [1.05-1.51] versus 1.57 [1.38–2.53] l for day 1, P = 0.008; 1.33 ± 0.43 versus 2.24 ± 0.87 l for day 2, P < 0.001). Moreover, the duration of arterial desaturation < 90% were longer in the PCA group during the first (8.6 [0.8–28.2] versus 1.3 [0–2.6] min, P = 0.02) and the second postoperative night (13.5 [3.5–54] versus 0.4 [0–2.6] min, P = 0.025).

Conclusion

The results of this study suggest that the use of TEA is associated with a better preservation of respiratory function assessed by spirometric data and noctural arterial desaturation recording after thoracic surgery for lobectomy.     

Effect of epinephrine on epidural, intrathecal, and plasma pharmacokinetics of ropivacaine and bupivacaine in sheep

BACKGROUND: Local vasoconstriction induced by epinephrine added to epidural local anaesthetics has been shown to improve their quality and duration of action in several clinical reports. There are several assumptions on the mechanisms. This study was designed to evaluate the influence of epinephrine on transmeningeal uptake of epidurally administered ropivacaine and bupivacaine by measuring local anaesthetic concentrations in the epidural and intrathecal spaces and in plasma. METHODS: Ropivacaine (50 mg) and bupivacaine (30 mg) were administered epidurally in sheep with and without epinephrine (75 microg). A microdialysis technique was used to simultaneously measure epidural and intrathecal drug concentrations. Resulting dialysate and plasma concentrations were used to calculate pharmacokinetic parameters for ropivacaine and bupivacaine. RESULTS: Co-administration of epinephrine decreased epidural clearance for ropivacaine [0.6 (sd 0.1) vs 0.4 (0.1) ml min(-1)] but not significantly for bupivacaine [1.2 (0.4) vs 0.8 (0.3) ml min(-1)]. The resultant increase in epidural area under the concentration-time curves (31% for ropivacaine and 52% for bupivacaine) was also observed in the intrathecal space (21% increase for ropivacaine and 37% for bupivacaine). There was no significant influence of epinephrine on ropivacaine plasma pharmacokinetics. Plasma Cmax for bupivacaine was decreased. CONCLUSIONS: These results show that epinephrine decreases the clearance and distribution processes involved in epidural disposition of ropivacaine and bupivacaine, leading to an increased uptake into the intrathecal space with an apparent more pronounced effect for bupivacaine.     

Fatigue responses in exercise under control of VO2

To examine the fatigue response during an exhaustive heavy exercise performed under control of oxygen uptake (SS@V.O (2)Delta50) or power output (SS@pDelta50), eleven trained male subjects performed an incremental test to determine the peak of the oxygen uptake value (V.O (2peak)) and lactate threshold and two exhaustive steady-state cycling exercises at the intermediate value between the lactate threshold and V.O (2peak) (SS@V.O (2)Delta50 and SS@pDelta50). The control of V.O (2) induced an oscillation of the power output, which lowered the average power output (276 +/- 47 vs. 315 +/- 40 W, p = 0.004) and cancelled the slow component of oxygen kinetics. However, all subjects reached maximal cardiac output (CO) and heart rate (HR) values which were sustained almost two times longer in SS@V.O (2)Delta50 compared to SS@pDelta50 (979 +/- 854 vs. 475 +/- 236 s, p = 0.046 for CO and 1050 +/- 890 vs. 513 +/- 288 s, p = 0.037 for HR). Furthermore, SS@pDelta50 elicited V.O (2peak) but not SS@V.O (2)Delta50 (4963 +/- 434 vs. 4723 +/- 460 mL . min (-1), p = 0.026). Finally, the time spent at the maximal CO and HR values is correlated with time to exhaustion at V.O (2)Delta50. In conclusion, the cause of fatigue does not seem to have the same origin during exhaustive supra-lactate threshold exercise under control of V.O (2) (V.O (2)Delta50) compared to constant power output (pDelta50), while both elicit the maximal HR and CO values.     

Influence of CBCT parameters on the output of an automatic edge-detection-based endodontic segmentation

Objectives:

To determine the optimal CBCT settings for an automatic edge-detection-based endodontic segmentation procedure by assessing the accuracy of the root canal measurements.

Methods:

12 intact teeth with closed apexes were cut perpendicular to the root axis, at pre-determined levels to the reference plane (the first section made before acquisition). Acquisitions of each specimen were performed with Kodak 9000^® 3D (76 µm, 14 bits; Kodak Carestream Health, Trophy, France) by using different combinations of milliamperes and kilovolts. Three-dimensional images were displayed and root canals were segmented with the MeVisLab software (edge-detection-based method; MeVis Research, Bremen, Germany). Histological root canal sections were then digitized with a 0.5- to 1.0-µm resolution and compared with equivalent two-dimensional cone-beam reconstructions for each pair of settings using the Pearson correlation coefficient, regression analysis and Bland–Altman method for the canal area and Feret''s diameter. After a ranking process, a Wilcoxon paired test was carried out to compare the pair of settings.

Results:

The best pair of acquisition settings was 3.2 mA/60 kV. Significant differences were found between 3.2 mA/60 kV and other settings (p < 0.05) for the root canal area and for Feret''s diameter.

Conclusions:

The quantitative analyses of the root canal system with the edge-detection-based method could depend on acquisition parameters. Improvements in segmentation still need to be carried out to ensure the quality of the reconstructions when we have to deal with closer outlines and because of the low spatial resolution.     

Postoperative complications after breast implantation

Augmentation mammoplasty is one of the most popular and frequently performed aesthetic operations. The implants are not, however, without complications; and many have been reported in order to this surgical procedure: hematoma, infection, seroma, capsular contracture, rupture ... Current surgical practices and modern implants used for breast augmentation produce fewer complications than procedures and devices of the past. The aim of this work is to index most common post operative breast complications. The prevention and the treatment procedure of these complications are also reported. A good knowledge of all these points seems to be essential to improve the quality of the final results and patients satisfaction.     

Effects of PEEP on oxygenation and respiratory mechanics during one-lung ventilation

Background. One-lung ventilation-related hypoxaemia (OLV-RH)can occur in patients with healthy lungs. In this case, PEEPfrequently improves oxygenation. The aim of this study was todetermine, in a healthy lung model of OLV, whether the increasein PEEP improved oxygenation and whether the mechanisms involvedinclude both inspiratory lung recruitment and an end-expiratorylung volume increase. Since inhaled nitric oxide (iNO) may havea synergistic effect on oxygenation in the case of PEEP-inducedrecruitment, their association was also tested. Methods. Twenty pigs were studied during open-chest, left OLV.Arterial blood gases and haemodynamic variables were measuredat different levels of PEEP (0, 5, 10 and 15 cm H₂O) appliedin random order with or without iNO 4 p.p.m. Pressure–volumecurves were measured at each level of PEEP. Results. PEEP₅ and PEEP₁₀ improved / ratio (P<0.005) and shunt (P<0.005) regardlessof the presence of iNO. PEEP₁₅ improved oxygenation and shuntonly when it was associated with iNO (P<0.001). Whereas PEEP₅,PEEP₁₀ and PEEP₁₅ were associated with a significant increasein end-expiratory volume (P<0.001), only PEEP₅ and PEEP₁₀were associated with continuous lung volume recruitment (P<0.01).Moreover, PEEP₁₅ induced a significant decrease in linear compliance(P<0.001). Conclusions. In a healthy porcine lung model of OLV-RH, moderatePEEP can improve oxygenation. This effect implies both expiratoryand inspiratory pulmonary recruitment. Co-administration of4 p.p.m. iNO was ineffective.     

Subchondral and trabecular bone metabolism regulation in canine experimental knee osteoarthritis

OBJECTIVE: To determine trabecular and subchondral bone metabolic changes in experimental canine osteoarthritis (OA). METHODS: OA was induced in 19 dogs by transection of the anterior cruciate ligament (ACL) of the right knee through a stab wound. Dogs were sacrificed at 8 (n=7) and 12 weeks (n=12) after surgery. Non-operated normal dogs (n=6) were used as controls. After sacrifice, samples were obtained from the weight-bearing area of medial tibial plateaus. Explants and cell cultures were prepared from subchondral and trabecular bone. Osteocalcin (Oc), cellular alkaline phosphatase (ALPase), urokinase plasminogen-activator (uPA), prostaglandin E2 (PGE2), metalloproteinase (MMP) and nitric oxide (NO) were measured using standard procedures. RESULTS: ALPase production was significantly increased only at week 12 in subchondral and trabecular bone, while an increase in Oc was noted at week 8. uPA and MMP activity were increased significantly at week 12 in subchondral bone, while PGE2 levels were significantly higher in subchondral and trabecular bone at week 12 compared to normal. A decrease in NO production appeared late at week 12 in trabecular bone, whereas NO levels from subchondral bone were significantly increased compared to normal at week 8. DISCUSSION: Intense bone remodeling takes place in both subchondral and trabecular bone in the knee following ACL transection. This process seems to occur around week 12, although Oc and NO appeared to be involved earlier at 8 weeks. These results suggest that not only subchondral but also trabecular bone metabolism is altered in this OA model.     

Prevention of venous thromboembolism following cardiac, vascular or thoracic surgery

In the absence of thromboprophylaxis, coronary artery bypass graft surgery (CABG), intrathoracic surgery (thoracotomy or video-assisted thoracoscopy), abdominal aortic surgery and infrainguinal vascular surgery are high-risk surgeries for the development of venous thromboembolic events (VTE). The incidence of VTE following surgery of the intrathoracic aorta, carotid endarterectomy or mediastinoscopy is unknown. Data from the litterature are lacking to draw evidence-based recommandations for venous thromboprophylaxis after these three types of surgeries, and the following guidelines are but experts'opinions (Grade D recommendations). Thromboprophylaxis is recommended after CABG (Grade D), with either subcutaneous (SC) low molecular weight heparin (LMWH) or SC or intravenous (i.v.) unfractioned heparin (UH) (PTT target = 1.1-1.5 time control value) (both grade D). This may be combined with the use of intermittent pneumatic compression device (Grade B). After valve surgery. The anticoagulation recommended to prevent valve thrombosis is sufficient in order to prevent VTE. We recommend thromboprophylaxis with either LMWH or low dose UH to prevent VTE after aortic or lower limbs infrainguinal vascular surgery (both grade B and D). Vitamine K antagonists (VKA) are not recommended in this indication (Grade D). We recommend thromprophylaxis following intrathoracic surgery via thoracotomy or videoassisted thoracoscopy (grade C). Either subcutaneous LMWH or subcutaneous or i.v. low dose UH may be used (Grade C). Efficacy of intermittent pneumatic compression device has been demonstrated in a study (grade C). VKA are not recommended (grade D). No further recommendation regarding the duration of thromboprophylaxis after these three types of surgeries can be made.