Intercompartmental fluid volume shifts during cardiopulmonary bypass measured by A-mode ultrasonography

The Role of Tolvaptan Administration After Cardiac Surgery: A Meta-Analysis

OBJECTIVE

To evaluate the efficacy and safety of tolvaptan in fluid management after cardiac surgery compared with conventional diuretic treatment.

DESIGN

Systematic review of the literature with meta-analyses.

SETTING

The Medline, Scopus, Cochrane Central Register of Controlled Trials, Clinicaltrials.gov, and Google Scholar databases were searched from inception to July 30, 2018.

PARTICIPANTS

The study comprised 759 patients undergoing cardiac surgery.

INTERVENTIONS

Tolvaptan administration (n = 397) or standard diuretic therapy (n = 398).

MEASUREMENTS AND MAIN RESULTS

Ten studies were included in the present meta-analysis. Tolvaptan administration was associated with a significantly faster return to preoperative body weight (mean difference [MD)] -1.48 d, 95% confidence interval [CI] -1.92 to 1.03), shorter duration of hospital stay (MD -2.58 d, 95% CI -5.09 to -0.07), lower incidence of acute kidney injury (odds ratio 0.34, 95% CI 0.16-0.69), and greater urine output (MD 0.47 L/d, 95% CI 0.25-0.69) and sodium levels (MD 2.85 mEq/L, 95% CI 1.90-3.80). No significant differences were present regarding duration of intensive care unit stay (MD -0.09 d, 95% CI -0.33 to 0.15), arrhythmia incidence (odds ratio 0.58, 95% CI 0.33-1.02), and serum creatinine values (MD -0.08 mg/dL, 95% CI -0.20 to 0.04).

CONCLUSIONS

The outcomes of the present meta-analysis suggest the promising role of tolvaptan administration in the management of fluid retention in patients after cardiac surgery. Future large-scale clinical trials should be conducted to fully elucidate its efficacy and to assess the optimal treatment protocol to be applied in the clinical setting.

Fluid distribution kinetics during cardiopulmonary bypass

OBJECTIVE

The purpose of this study was to examine the isovolumetric distribution kinetics of crystalloid fluid during cardiopulmonary bypass.

METHODS

Ten patients undergoing coronary artery bypass grafting participated in this prospective observational study. The blood hemoglobin and the serum albumin and sodium concentrations were measured repeatedly during the distribution of priming solution (Ringer's acetate 1470 ml and mannitol 15% 200 ml) and initial cardioplegia. The rate of crystalloid fluid distribution was calculated based on 3-min Hb changes. The preoperative blood volume was extrapolated from the marked hemodilution occurring during the onset of cardiopulmonary bypass. Clinicaltrials.gov: NCT01115166.

RESULTS

The distribution half-time of Ringer's acetate averaged 8 minutes, corresponding to a transcapillary escape rate of 0.38 ml/kg/min. The intravascular albumin mass increased by 5.4% according to mass balance calculations. The preoperative blood volume, as extrapolated from the drop in hemoglobin concentration by 32% (mean) at the beginning of cardiopulmonary bypass, was 0.6-1.2 L less than that estimated by anthropometric methods (p<0.02). The mass balance of sodium indicated a translocation from the intracellular to the extracellular fluid space in 8 of the 10 patients, with a median volume of 236 ml.

CONCLUSIONS

The distribution half-time of Ringer's solution during isovolumetric cardiopulmonary bypass was 8 minutes, which is the same as for crystalloid fluid infusions in healthy subjects. The intravascular albumin mass increased. Most patients were hypovolemic prior to the start of anesthesia. Intracellular edema did not occur.

Effects of epidural anesthesia on intrathoracic blood volume and extravascular lung water during on-pump cardiac surgery

Background: The most important side effect of epidural anesthesia is hypotension with functional hypovolemia. Aggressive infusion therapy can reduce the hypotension effect. However, in conjunction with cardiopulmonary bypass, it can increase acute lung injury. We hypothesized that epidural anesthesia, by reducing cardiac sympathetic tonus, with subsequent better pulmonary flow, does not increase lung interstitial fluids.

Methods: Sixty patients undergoing coronary artery bypass graft (CABG) surgery with cardiopulmonary bypass (CPB) were randomized to combined general anesthesia with epidural anesthesia / analgesia, (EA) group, and to general anesthesia with i/v opiate analgesia, (GA) group. Patients in the EA group received a high thoracic epidural, preoperatively. Intraoperatively, 0.25% bupivacaine 8 mL/h was infused and general anesthesia with sevoflurane was followed by bupivacaine infusion for 48 hours postoperatively. General anesthesia in the GA group was with sevoflurane and fentanyl 10 - 12 µg/kg and analgesia with pethidinum 0.1 - 0.4 mg/kg i.v. postoperatively. Global end-diastolic volume index (GEDI), intrathoracic blood volume index (ITBI) and extravascular lung water index (ELWI) were measured before anesthesia, before CPB and 15, 60, 180, 600 min. and 24 hr after CPB. Duration of mechanical lung ventilation was registered in both groups.

Results: ITBI and GEDI were significantly higher in the EA group at all time points of measurement (ITBI 945.6±146.4 ml/m2 and 870.6±146.5 ml/m 2 vs. 1118±153.2 ml/m2 and 1020±174.9 ml/m 2; GEDI 720±96.19 ml/m2 and 775.0±159.5 ml/m 2 vs. 805.4±97.59 ml/m2 and 888±117.3 ml/m 2). GEDI was significantly lower in the GA group compared with baseline (801.9±132.4 ml/m2 vs. 695±169.2 mL/m2). ELWI was significantly higher in the GA group (7.233±1.35 ml/kg and 7.333±1.32 ml/kg vs. 8.533±1.45 ml/kg and 8.633±1.71 ml/kg), but without significant changes in the EA group. Duration of mechanical lung ventilation was shorter in the EA group (663.7±98.39 min. vs. 362.2±33.72 min.).

Conclusions: Epidural anesthesia / analgesia does not increase interstitial lung fluids by increasing intrathoracic blood volume or the amount of infusion fluids in patients undergoing cardiac surgery under cardiopulmonary bypass. There is, also, a decreased duration of mechanical lung ventilation.

Cardiopulmonary bypass and edema: physiology and pathophysiology

Edema is a common morbidity following cardiopulmonary bypass (CPB) and can result in injury to many organs, including the heart, lungs, and brain. Generalized edema is also common and can lead to increased post-operative hospital stay and other morbidities. Pediatric patients are more susceptible to post-CPB edema and the consequences are more severe for this population. Hemodilution and systemic inflammatory responses are two suspected causes of CPB-related edema; however, the mechanisms involved are far from understood. Also, the common strategies to improve edema have not been completely successful and there is a need for new strategies at maintaining a fluid balance of patients as close to physiological as possible, especially for pediatric patients. An integrative approach to understanding edema is necessary as the forces involved in fluid homeostasis are dynamic and interdependent. Therefore, this review will focus on the physiology of fluid homeostasis and the pathologies of fluid shifts during CPB which lead to general edema as well as tissue-specific edema.

Neonatal Aortic Arch Hemodynamics and Perfusion During Cardiopulmonary Bypass

The objective of this study is to quantify the detailed three-dimensional (3D) pulsatile hemodynamics, mechanical loading, and perfusion characteristics of a patient-specific neonatal aortic arch during cardiopulmonary bypass (CPB). The 3D cardiac magnetic resonance imaging (MRI) reconstruction of a pediatric patient with a normal aortic arch is modified based on clinical literature to represent the neonatal morphology and flow conditions. The anatomical dimensions are verified from several literature sources. The CPB is created virtually in the computer by clamping the ascending aorta and inserting the computer-aided design model of the 10 Fr tapered generic cannula. Pulsatile (130 bpm) 3D blood flow velocities and pressures are computed using the commercial computational fluid dynamics (CFD) software. Second order accurate CFD settings are validated against particle image velocimetry experiments in an earlier study with a complex cardiovascular unsteady benchmark. CFD results in this manuscript are further compared with the in vivo physiological CPB pressure waveforms and demonstrated excellent agreement. Cannula inlet flow waveforms are measured from in vivo PC-MRI and 3 kg piglet neonatal animal model physiological experiments, distributed equally between the head-neck vessels and the descending aorta. Neonatal 3D aortic hemodynamics is also compared with that of the pediatric and fetal aortic stages. Detailed 3D flow fields, blood damage, wall shear stress (WSS), pressure drop, perfusion, and hemodynamic parameters describing the pulsatile energetics are calculated for both the physiological neonatal aorta and for the CPB aorta assembly. The primary flow structure is the high-speed canulla jet flow (∼3.0 m/s at peak flow), which eventually stagnates at the anterior aortic arch wall and low velocity flow in the cross-clamp pouch. These structures contributed to the reduced flow pulsatility (85%), increased WSS (50%), power loss (28%), and blood damage (288%), compared with normal neonatal aortic physiology. These drastic hemodynamic differences and associated intense biophysical loading of the pathological CPB configuration necessitate urgent bioengineering improvements—in hardware design, perfusion flow waveform, and configuration. This study serves to document the baseline condition, while the methodology presented can be utilized in preliminary CPB cannula design and in optimization studies reducing animal experiments. Coupled to a lumped-parameter model the 3D hemodynamic characteristics will aid the surgical decision making process of the perfusion strategies in complex congenital heart surgeries.

Thoughts and Progress. Protracted Bleeding After Hirudin Anticoagulation for Cardiac Surgery in a Patient With HIT II and Chronic Renal Failure

Heparin-induced thrombocytopenia type II (HIT II) requires alternative anticoagulation. Hirudin has been effectively used in patients with HIT II scheduled for cardiac surgery. However, bleeding complications were observed in patients with renal impairment. In vitro hemodialysis (HD) has been questioned over its efficacy in eliminating hirudin. Another approach to stop bleeding is the application of recombinant factor VIIa (rFVIIa). We report on a patient with HIT II and chronic renal failure who suffered from severe hirudin-induced bleeding after cardiac surgery who was safely treated with a combined approach of surgical hemostasis, substitution of blood products, HD, and rFVIIa to stop finally bleeding.