Large Fluid Load Research Articles

Numerical investigation on the flow characteristics of liquid oxygen and water in the structured packing

The distillation efficiency of the cryogenic air separation unit is significantly affected by the inside flow performance of the cryogenic oxygen and nitrogen mixture in the structured packing. Owing to the difficulties in cryogenic experiments, the development of structured packings in cryogenic distillation often relies on the hydraulic experiments at room temperatures, while the real flow characteristics of the cryogenic fluids in the structured packing are hardly known. In this work, with the help of CFD simulation, a 3-D model combining VOF method was built to study the flow characteristics of liquid oxygen (LOX) in the structured packing, and comparisons with water were also carried out. Effects of liquid load and equivalent contact angle on the flow patterns, the liquid hold-up, the interfacial area and the average film thickness were analyzed. Results show that the flow of water is mainly rivulets, while LOX can form film flow on the packing surface in a large fluid load range due to its small contact angle and surface tension. Because the interfacial area of LOX isn’t strongly affected by liquid load, its liquid film thickness could be the main consideration for heat transfer, mass transfer and load selection. Since the variation of contact angle has slight effect on the flow parameters of LOX, the optimization of structured packings for cryogenic distillation may not be expected by the surface micro texture improvements.

Abstract 16580: Safety and Efficacy of Cryoballoon Ablation in Patients With Congestive Heart Failure

Background: Irrigated radiofrequency ablation of atrial fibrillation (AF) is challenging in patient with severe systolic congestive heart failure due to large fluid load. The use of cryoballoon ablation in patients with low ejection fraction (EF) and NYHA class II-IV congestive heart failure has not been well described, and may benefit from the lack of fluid bolus and restoration of sinus rhythm. Method: To evaluate the efficacy and safety of cryoballoon ablation for systolic heart failure patients with atrial fibrillation (AF). Single center retrospective review of 832 patients with AF ablation using Arctic Front Advance Cryoballoon (Medtronic, Minneapolis, MN) was performed, and 188 patients has EF less than 35% (24 paroxysmal, 122 persistent, and 42 long-standing persistent, average EF 28%) was analyzed. Procedural tolerance, complications, and impact on congestive heart failure were reviewed over a 12 months follow up. Results: All 188 patients (Average age 68, LA size 5.8 cm) with systolic CHF and atrial fibrillation underwent successful pulmonary vein (PV) isolation and extra-pulmonary vein lesions sets applied using cryoballoon. Non-irrigated radiofrequency ablation was used in (22%) for cavo-tricuspid isthmus flutter ablation. Acute procedural success rate was 100% with length of hospitalization of 1.1 days. Average procedural time was 2.6 hours, and fluid infusion of 0.3 liters, no significant complications was noted. Atrial fibrillation burden was monitored by implantable pacemaker or defibrillator in 118 of 188 patients (63%), and others were monitoring via wearable looping recorders every 3 months. Significant AF burden (<10% atrial high rate burden) was observed in over 67% of the patients, and improvement CHF symptoms were reported in all of the patients with reduction of atrial fibrillation burden. Conclusions: Cryoballoon of AF in systolic CHF population is well tolerated with high procedural success rate and low complication rate. Significant clinical improvement of CHF class was observed in patient with reduction of atrial fibrillation burden. Ongoing collection of data is needed to quantify long-term benefit.

In Reply

We thank Drs. Youngblood and Sondergaard for their letters regarding our recently published article.1We agree with Dr. Youngblood1 that standard monitoring already provides substantial information about our patients’ hemodynamic status. Today, pulse pressure variation (PPV) and its corresponding noninvasive parameters are easily available and used in clinical practice.2 In recent years, PPV analysis algorithms have been integrated into different standard monitoring systems,3 and PPV can be reliably assessed on a noninvasive basis by plethysmography.4 Thus, standard monitoring evolves, and today PPV can be considered a standard hemodynamic parameter for a larger population of patients who require perioperative invasive blood pressure monitoring with an arterial line. When no arterial line is required, pulse oximetry devices, which provide the respective functional hemodynamic parameters, can be applied to assess and predict fluid responsiveness. Clearly, continuous end-tidal carbon dioxide monitoring may further support clinical decision making—but still this requires validation in large perioperative clinical studies. In addition, one has to keep in mind that the changes in end-tidal carbon dioxide, induced by a passive leg raising, cannot always be assessed during surgery.We read with interest Dr. Sondergaard’s acerbic letter regarding our article; we thank him for the querulous interest he has shown in our work. Neither our results nor our discussion demonstrate that the PPV should replace cardiac output (CO) measurements. Dr. Sondergaard’s reference of our work when making this claim suggests that he is less familiar with our results.We do demonstrate that when estimating CO trends, volume expansion-induced changes in PPV is superior to standard measures of arterial pressure.1,5 PPV is interesting because it identifies patients who will benefit from fluid loading and volume expansion-induced changes in PPV allows for ongoing assessment of fluid-loading efficacy. This provides the clinician with important information which then allows for CO optimization.Does an increased CO, as a result of fluid loading, result in improved postoperative outcomes? Dr. Sondergaard will be disappointed when we affirm that we do not have the answer to this question. He may be even more disappointed when we affirm that the answer to this question can probably not be framed in his favored “YES/NO” format.CO is only one of the components of oxygen delivery, and maximizing CO, through fluid administration, does not equate to optimization of oxygen delivery. Fluid loading always causes hemodilution, and hemoglobin concentration plays a key role in oxygen delivery. It is therefore possible that increasing CO, by administering a large fluid load, may actually decrease oxygen delivery. Oxygen delivery is the true parameter to optimize, but it remains difficult to measure and several parameters should be simultaneously optimized to achieve ideal oxygen delivery. PPV and volume expansion-induced changes in PPV are only two of the tools, which may be used to achieve this goal. Using them in isolation may be appropriate in some clinical settings, but it will always remain suboptimal.Our aim in conducting this study was to explore the predictive performance of PPV under ideal conditions. As a result, we did not record the number of patients who were not selected because of atrial fibrillation.May we offer a more balanced and less jejune set of conclusions than those purportedly “obvious” conclusions drawn by Dr. Sondergaard?NO; CO measurements alone is not sufficient for optimization of oxygen delivery. Fluid loading impacts hemoglobin concentration, and neither volume expansion-induced changes in PPV nor direct CO measurements reliably reflect this.NO; because there is no strong and definitive evidence to suggest that “validated” and calibrated dilution methods with continuous, updated arterial curve–based calculation of CO impact on postoperative outcomes, we do not have to use them (“…no monitoring tool, no matter how accurate, by itself has improved patient outcome.”)6NO; we do not find ourselves compelled to adopt cardiovascular models from giants such as Guyton or Dr. Sondergaard. Eminence is rarely, if ever, a substitute for evidence.YES, key opinion holders in the European intensive care community should be very cautious about promoting any device or system that has not clearly demonstrated its ability to improve postoperative outcomes.Having matured beyond Dr. Sondergaard’s preoccupation with dreams of the conceptualization and intellectualization of endeavors past explored, we have actually evaluated PVV to understand its abilities and limitations. Although PPV informs clinicians on how fluid loading impacts on CO, there is a common misconception that fluid loading is required when PPV is high—this requires correcting.PPV requires engagement, interpretation, and judgment. For this reason, we have developed the grey zone concept, which we offer to Dr. Sondergaard in the hope that he would evaluate it empirically in a clinical study.

What Factors Should We Consider in Deciding When to Transfuse Patients Undergoing Elective Cardiac Surgery?

Blood transfusion remains one of the commonest interventions carried out upon individuals undergoing cardiac surgery. Despite this, the scientific rationale on which to base this decision is limited. Currently, hemoglobin concentration is often used as the sole guide as to when a transfusion may be required. A fall in hemoglobin concentration is often assumed to be associated with a similar drop in red cell volume. A review was undertaken of all the relevant peer-reviewed literature to determine what factors we should consider when deciding to transfuse elective cardiac surgery patients. The large fluid load associated with cardiac surgery, primarily from the cardiopulmonary bypass circuit, may have a significant dilutional effect. In such a scenario, several interlinked protective mechanisms may ensure that tissue oxygenation is maintained, including a reduction in blood viscosity, a decrease in systemic afterload, and an increase in cardiac output. Furthermore, oxygen requirements during the initial perioperative phase are reduced because of the effect of general anesthesia and hypothermia during cardiopulmonary bypass. When deciding to transfuse, consideration should be given to red cell volume, circulatory status, and oxygen requirement. It is possible that such an all-encompassing approach would reduce the incidence of unnecessary, and potentially counterproductive, red cell transfusion in cardiac surgery.

Response to a fluid load in athletes with a history of exercise induced hyponatremia.

To determine whether athletes who had previously developed hyponatremia during an ultradistance triathlon show an impaired ability to excrete a large fluid load compared with athletes who had completed the same race without developing hyponatremia. Six athletes who had developed hyponatremia ([Na] < 135 mmol x L(-1)) in the 1997 Ironman Triathlon (study cases) were compared with six athletes who completed the same race without hyponatremia (controls). All participants consumed 3.4 L of water over 2 h at rest. Weight, urine output, urine electrolytes, serum [Na(+)], hemoglobin, and hematocrit were measured every 30 min. Changes in plasma volume and residual fluid volume in the gut were estimated from these data. There were no significant differences between cases and controls in any parameters measured. Maximal rates of urine production (+/- SD) (1043 +/- 331 mL x h(-1) for cases, 878 +/- 168 mL x h(-1) for controls) were substantially behind the rate of fluid intake (1500 mL x h(-1)). Consequent to fluid retention, serum [Na(+)] fell progressively in both groups. Five cases and four controls developed hyponatremia. There was an inverse correlation between change in body weight and change in [Na(+)] (r = -0.67). Estimated changes in the intra- and extra-cellular fluid volumes could account for all the retained fluid, and there was little evidence for fluid accumulation in the bowel. When evaluated at rest, there does not appear to be any unique pathophysiological characteristic that explains why some athletes develop hyponatremia in response to fluid overload during prolonged exercise. Rather, hyponatremia was induced with equal effect in both cases and controls, consequent to progressive fluid overload of all the body fluid compartments and without evidence for fluid retention in the small bowel.

Colonic cleansing, fluid absorption, and discomfort following tap water and soapsuds enemas

Tap water and soapsuds are common enema solutions, but little is known about their effectiveness. Consequently, nurses have no guidance when choosing the best enema for a given patient. In this study, liver transplant patients were given either a tap water or soapsuds enema preoperatively. Amount of enema instilled into the colon and output were measured. Soapsuds enemas produced significantly greater output than tap water and were equally well tolerated. Most subjects who received tap water enemas retained more fluid than was eliminated. Based on these findings, nurses should use caution when giving repeated enemas to patients sensitive to large fluid loads. Copyright © 2000 by W.B. Saunders Company

Etoposide phosphate or etoposide with cisplatin in the treatment of small cell lung cancer: Randomized Phase II trial

Etoposide phosphate, a water soluble prodrug of etoposide, has several potential advantages including easier and more rapid administration, avoidance of large fluid loads, and elimination of hypersensitivity reactions and other problems related to the solubilizer. This randomized Phase II study was done to evaluate the efficacy and toxicity of etoposide phosphate and etoposide, when used in combination with cisplatin in the treatment of patients with small cell lung cancer. Previously untreated small cell lung cancer patients were randomized to receive cisplatin in combination with molar equivalent doses of either etoposide or etoposide phosphate. The patients were evaluated with respect to response rate, time to progression, survival, and toxicity. Response rates with etoposide phosphate and etoposide were 61% (95% confidence interval 55–67%) and 58% (95% confidence interval 52–64%), respectively (P = 0.85). Median time to progression was 6.9 months for patients who received etoposide phosphate and 7.0 months for those with etoposide (P = 0.50). For extensive stage disease patients, median survival with etoposide phosphate was 9.5 months versus 10 months for etoposide (P = 0.93). The corresponding median survivals for patients with limited stage disease were > 16 months and 17 months, respectively (P = 0.62). Myelosuppression was the most common toxicity; Grade 3 and 4 leukopenia occurred in 63% of patients receiving etoposide phosphate compared with 77% receiving etoposide (P = 0.16). The combination of etoposide phosphate and cisplatin is effective in the treatment of small cell lung cancer, and can be administered with acceptable toxicity. This study was not designed to be a formal Phase III comparative trial, but the efficacy and toxicity observed with this regimen were found to be similar to a standard etoposide/cisplatin regimen, using

Whole-gut irrigation in infants and young children.

In the search for a superior alternative to conventional bowel preparation which often gives unsatisfactory results in children, we have introduced whole-gut irrigation for pediatric use. After a pilot study on 15 children during which adjustments on the technique were made, we settled on an intensive regimen with some notable modifications from conventional adult practice: the use of warm Hartmann's solution, a relatively large fluid load (mean volume 5.3 l/kg body weight, range 3.0 - 12.0 l/kg) and a rapid infusion rate (1.5 ml/kg/min). We then evaluated its safety, effectiveness, and acceptability prospectively on 45 patients undergoing colonoscopy or colorectal surgery, age ranging from 4 months to 11 years, with a mean of 3.9 years. Subjective complaints were mild and included nausea/vomiting, 12 cases (26.7 percent); abdominal colic, two (4.4 percent); and distending discomfort, three (6.7 percent). There was a mean weight gain of 4.0 percent but no gross electrolyte disturbances. Results of bowel preparation were satisfactory in 33 (73.3 percent), adequate in ten (22.2 percent) and poor in two (4.4 percent). Compared with our previous method, in which inadequate preparation occurred in 4/20 patients, (20 percent) by conventional measures, whole-gut irrigation represents a statistically significant improvement (P less than 0.05). In addition, whole-gut irrigation shortened hospital stay and obviated the traditional need of two to three days' dietary restrictions.

The Parkland formula in patients with burns and inhalation injury.

Clinical concern over the fluid status of patients with burns and inhalation injury led us to review the course of 101 consecutive adult patients with large (20%-60% BSA) burns, all resuscitated with the Parkland formula. The results indicate that this regimen may have resulted in unnecessarily large fluid loads in patients with inhalation injury. In order to avoid the highly significant excess amount of fluid over the calculated estimate, patients with burns and inhalation injury should be resuscitated with substantially less than formula predictions, with acceptance of urine output in the range of 0.3-0.5 ml/kg/hr.

Pulmonary Atelectasis and Other Respiratory Complications after Cardiopulmonary Bypass and Investigation of Aetiological Factors

Radiological evidence of pulmonary complications and possible aetiological factors were investigated in 50 consecutive patients after heart operations with cardiopulmonary bypass. Atelectasis was the most frequent pulmonary complication except for small pleural effusions, with an incidence of 64 per cent. Several types of atelectasis frequently co-existed, with a predominance of the less extensive plate and subsegmental forms. The incidence of atelectasis was the same on each side and the site of atelectasis was basal in three quarters of the patients. Preoperative clinical and catheter data were unrelated to the incidence of atelectasis. There was a significant positive correlation between a short cardiopulmonary bypass time and plate atelectasis, between a large fluid load after bypass and segmental atelectasis, between re-operation for bleeding and subsegmental atelectasis and between post-operative gastric dilation and atelectasis. The type of operation, the use of the intra-aortic balloon and the length of postoperative respiratory ventilation were unrelated to the incidence of atelectasis. The mechanism of development of atelectasis is discussed.

Pulmonary atelectasis and other respiratory complications after cardiopulmonary bypass and investigation of aetiological factors.

Radiological evidence of pulmonary complications and possible aetiological factors were investigated in 50 consecutive patients after heart operations with cardiopulmonary bypass. Atelectasis was the most frequent pulmonary complication except for small pleural effusions, with an incidence of 64 per cent. Several types of atelectasis frequently co-existed, with a predominance of the less extensive plate and subsegmental forms. The incidence of atelectasis was the same on each side and the site of atelectasis was basal in three quarters of the patients. Preoperative clinical and catheter data were unrelated to the incidence of atelectasis. There was a significant positive correlation between a short cardiopulmonary bypass time and plate atelectasis, between a large fluid load after bypass and segmental atelectasis, between re-operation for bleeding and subsegmental atelectasis and between post-operative gastric dilation and atelectasis. The type of operation, the use of the intra-aortic balloon and the length of postoperative respiratory ventilation were unrelated to the incidence of atelectasis. The mechanism of development of atelectasis is discussed.

The effects of large volume intravenous fluid infusion on neonatal renal function

Twenty healthy infants weighing less than 2,000 gm were studied at low (3.6 ml/kg/hr) or high (10.3 ml/kg/hr) rates of intravenous infusion. Inulin clearance determined by the constant infusion method was greater at the high rate of infusion (p = less than 0.05). Inulin clearance in two groups of infants over 2,000 gm studies at the same low or high rates of infusion did not increase at the higher rate of infusion. Since the GFR in infants less than 2,000 gm depends partially on the rate of intravenous infusion, small, healthy preterm infants may benefit from a rate of fluid administration greater than the low rate. When studies at low and high rates of infusion were compared in the 20 infants less than 2,000 gm, the fractional urinary sodium excretion increased with the increased fluid load. Delivery of fluid from the proximal tubule (CH2O =Na per dl GFR) increased (p less than 0.005). Free-water clearance and the absolute volume of urine increased at the high rate of infusion. These data indicate that the healthy preterm infant less than 2,000 gm, like the adult, compensates by increasing free-water clearance and urine volume when challenged with a large fluid load. Although fluid changes of short duration are appropriately handled, the effect of continuous rapid infusion on water and sodium balance in infants of this size remains to be determined.

Duration and significance of large fluid loads administered for circulatory support

Duration and significance of large fluid loads administered for circulatory support

Pulmonary Congestion Following Infusion of Large Fluid Loads in Thoracic Surgical Patients

Pulmonary Congestion Following Infusion of Large Fluid Loads in Thoracic Surgical Patients

The Effect of Large Fluid Loads on Lung Mechanics and Work

The Effect of Large Fluid Loads on Lung Mechanics and Work