Lung volumes, respiratory mechanics and dynamic strain during general anaesthesia.

BACKGROUND: Driving pressure (ΔP) represents tidal volume normalised to respiratory system compliance (CRS) and is a novel parameter to target ventilator settings. We conducted a study to determine whether CRS and ΔP reflect aerated lung volume and dynamic strain during general anaesthesia. METHODS: Twenty non-obese patients undergoing open abdominal surgery received three PEEP levels (2, 7, or 12 cm H2O) in random order with constant tidal volume ventilation. Respiratory mechanics, lung volumes, and alveolar recruitment were measured to assess end-expiratory aerated volume, which was compared with the patient's individual predicted functional residual capacity in supine position (FRCp). RESULTS: CRS was linearly related to aerated volume and ΔP to dynamic strain at PEEP of 2 cm H2O (intraoperative FRC) (r=0.72 and r=0.73, both P<0.001). These relationships were maintained with higher PEEP only when aerated volume did not overcome FRCp (r=0.73, P<0.001; r=0.54, P=0.004), with 100 ml lung volume increases accompanied by 1.8 ml cm H2O-1 (95% confidence interval [1.1-2.5]) increases in CRS. When aerated volume was greater or equal to FRCp (35% of patients at PEEP 2 cm H2O, 55% at PEEP 7 cm H2O, and 75% at PEEP 12 cm H2O), CRS and ΔP were independent from aerated volume and dynamic strain, with CRS weakly but significantly inversely related to alveolar dead space fraction (r=-0.47, P=0.001). PEEP-induced alveolar recruitment yielded higher CRS and reduced ΔP only at aerated volumes below FRCp (P=0.015 and 0.008, respectively). CONCLUSIONS: During general anaesthesia, respiratory system compliance and driving pressure reflect aerated lung volume and dynamic strain, respectively, only if aerated volume does not exceed functional residual capacity in supine position, which is a frequent event when PEEP is used in this setting.

Anaesthesiological strategies to improve outcome in liver transplantation recipients.

Graft and patients survival are the main goal of anesthesiological management in patients undergoing liver transplantation (LT). Even if anesthesiological practice sustained major developments over time, some evidence-based intraoperative strategies have not yet been widely applied. The aim of this review was to summarize intraoperative anesthesiological strategies which could have the potential to improve LT graft and/or recipient survival. Monitoring must be as accurate as possible in order to manage intraoperative hemodynamic changes. The pulmonary artery catheter still represents the more reliable method to monitor cardiac output by using the intermittent bolus thermodilution technique. Minimally invasive hemodynamic monitoring devices may be considered only in stable cirrhotic patients. Goal-directed fluid-therapy has not yet defined for LT, but it could have a role in optimizing the long-term sequelae associated with volume depletion or overload. The use of vasopressor may affect LT recipient's outcome, by preventing prolonged hypotension, decreasing blood products transfusion and counteracting hepato-renal syndrome. The use of viscoelastic point of care is also warranted in order to reduce blood products requirements. Decreasing mechanical ventilation time, when it is feasible, may considerably improve survival. Finally, monitoring the depth of anesthesia when integrated into an early extubation protocol might have a positive effect on graft function.

Low values of left ventricular ejection time in the post-anhepatic phase may be associated with occurrence of primary graft dysfunction after orthotopic liver transplantation: results of a single-centre case-control study.

BACKGROUND: Previous investigations on risk factors for orthotopic liver transplantation (OLT) surgery have not analyzed hemodynamic aberrations in great detail. Moreover, the usefulness of esophageal Doppler monitoring has not been extensively studied in this clinical setting. The aim of this study was to evaluate if the occurrence of primary graft dysfunction (PGD) may be anticipated by hemodynamic indexes measured by esophageal Doppler (ED) monitoring system as well as by pulmonary artery catheter (PAC) in patients undergoing OLT. MATERIALS AND METHODS: 38 OLT recipients were studied. Patients with acute liver failure or having non treated esophageal varices and those transplanted with marginal donors were excluded from the study. The haemodynamic data - measured by ED monitoring system (HemosonicTM 100, Arrow, OK, USA) and PAC - collected at the following 3 time points were considered for statistical analysis: 30 minutes after the induction of anesthesia but before skin incision, T0; 20 minutes after liver dissection, T1; at the beginning of biliary reconstruction, T2. On the basis of early outcome (72 hours after OLT), patients were distinguished into two groups: those with PGD (grade III-IV of Toronto classification) and those without PGD (grade I-II). RESULTS: LVETc (left ventricular ejection time) values, registered at the beginning of biliary reconstruction (T2), were lower in patients with PGD compared to those without PGD (p < 0.000), while there were no differences in hemodynamic parameters derived from PAC between the two groups. CONCLUSIONS: Since LVETc is related to preload, the results of this study would suggest that normovolemia could be the end point of a fluid replacement strategy in OLT setting.

Suspect carbon dioxide embolism during retroperitoneoscopic adrenalectomy.

During a retroperitoneoscopic adrenalectomy in the prone position, a sudden increase in end-Tidal CO2 (EtCO2) (from 42 to 68 mmHg) followed by an abrupt decrease (from 68 to 35 mmHg) was observed, concomitantly with a right adrenal vein laceration. Heart rate decreased to 30 bpm, and the systolic blood pressure decreased to 40 mmHg. The patient was slightly turned in the left lateral and Trendelenburg position and vasoactive drugs were administered. The systemic blood pressure, EtCO2, CO2 elimination (VCO2) and pulse oximetry (SpO2) progressively improved within 10 minutes and, at the end of the surgery, the blood pressure recovered from hypotension. ECG returned to normal, with sinusal rhythm and heart rate approximately 70 bpm. The patient was extubated and moved to the Intensive Care Unit (ICU). This case suggests that gas embolisms may occur during retroperitoneoscopic adrenalectomy, and acute changes in EtCO2 should alert the clinicians to these rare but potentially lethal complication. EtCO2 monitoring is essential during laparoscopy, as it may help an early detection of CO2 embolism, characterized by a transient and rapid increase in EtCO2, followed by an abrupt decrease.

Balanced anestesia versus total intravenous anestesia for kidney transplantation.

AIM: An ideal anesthetic regimen for kidney transplantation should be able to assure haemodynamic stability to obtain an optimal graft reperfusion. The aim of this study was to compare 2 regimens of anesthesia for patients submitted to kidney transplantation. METHODS: We studied 40 patients: 20 subjects (Group A) received balanced anesthesia with thiopental, fentanyl and isoflurane, to the others 20 (Group B), a total intravenous anesthesia (TIVA) with propofol and remifentanyl was given. In both groups muscle relaxation was obtained with a bolus of cisatracurium followed by a continuous infusion. We performed standard clinical, invasive blood pressure and central venous pressure monitoring. Hemodyna-mic data have been collected at standard times. During the postoperative period we evaluated the recovery (Aldrete Score) in the recovery room and the analgesia (VAS) at 1, 6, 24 h after the end of surgery. RESULTS: The trend of hemodynamic parameters did not show statistically significant differences between the 2 groups. We observed statistically significant differences concerning the quality of the recovery and the postoperative analgesia. The recovery in group B was faster than in group A, but in group A the pain control was better than in group B at least during the first postoperative hour. CONCLUSIONS: For their pharmacokinetic properties, propofol, remifentanyl and cisatracurium allow to obtain a good control of the hemodynamic parameters and a fast and safe recovery of consciousness. Total intravenous anesthesia regimen seems to be an alternative to the balanced anesthesia for patients undergoing kidney transplantation.