Fluid Infusion Rate Research Articles

Experimental study of flow fields in an airway closure model

The liquid lining in small human airways can become unstable and form liquid plugs that close off the airways. Bench-top experiments have been performed in a glass capillary tube as a model airway to study the airway instability and the flow-induced stresses on the airway walls. A microscale particle image velocimetry system is used to visualize quantitatively the flow fields during the dynamic process of airway closure. An annular film is formed by injecting low-viscosity Si-oil into the glycerol-filled capillary tube. The viscosity ratio between these two fluids is similar to that between water and air. The thickness of the film varies with the infusion rate of the core fluid, which is controlled by a syringe pump. After a uniform film is formed, the syringe pump is shut off so that the core flow speed is close to zero during closure. Instantaneous velocity fields in the annular film at various stages of airway closure are computed from the images and analysed. The wall shear stress at the instant when a liquid plug forms is found to be approximately one order of magnitude higher than the exponential growth period before closure. Within the short time span of the closure process, there are large wall shear stress fluctuations. Furthermore, dramatic velocity changes in the film flow during closure indicate a steep normal stress gradient on the airway wall. The experimental results show that the wall shear stress during closure can be high enough to injure airway epithelial cells. An airway that experiences closure and reopening cyclically during breathing could be injured from fluid forces during both phases of the cycle (i.e. inspiration and expiration).

Pediatric Fluid and Electrolyte Therapy

Managing fluids and electrolytes in children is an important skill for pharmacists, who can play an important role in monitoring therapy. Fluid therapy is divided into maintenance, deficit, and replacement requirements. The Holliday-Segar equation remains the standard method for calculating maintenance fluid requirements. Accounting for deficits when determining the fluid infusion rate is an important factor in treating dehydrated patients; deficit fluid is generally administered over the first 24 hours of hospitalization. Maintenance electrolyte requirements must be taken into account, with particular attention paid to sodium requirements, as recent evidence suggests that sodium needs in hospitalized children are higher than originally thought. Fluid therapy can also have an impact on drug therapy. Hydration status can affect the dose needed to achieve therapeutic concentrations, and dehydrated patients may be at risk for toxicity if standard doses of drugs with high volumes of distribution are used. Monitoring fluid and electrolyte therapy is an important role of the pediatric pharmacist.

The Effect of Duration of Surgery on Fluid Balance During Abdominal Surgery: A Mathematical Model

There is controversy regarding which fluid management regimen provides the best postoperative outcome. Interstitial fluid accumulation may adversely affect postoperative outcome, but the effect of surgical duration on fluid balance is unknown. In this study, we used a mathematical model to describe fluid distribution. Previously published data from bioimpedance analysis in patients undergoing abdominal surgery were used to calculate changes to interstitial volume (DeltaV(IT), percent change relative to baseline) in uninjured and injured tissues. Ratios of DeltaV(IT) in uninjured and injured tissues at the end of surgery to total fluid volume infused during surgery (V(INF), mL/kg) were compared between surgeries of duration <3 h (n = 5) and > or = 3 h (n = 25). Critical values for change in plasma volume (DeltaV(PL), percent change relative to baseline) and DeltaV(IT), which give rise to adverse outcome, were calculated from previously published data on the physiological effects of IV fluid administration in healthy volunteers. Finally, simulated abdominal surgery in a 70 kg man for 1-8 h was used to determine the effect of crystalloid infusion rate between 2 and 30 mL x kg(-1) x h(-1) on DeltaV(PL) and DeltaV(IT). Fluid infusion rates that maintained DeltaV(PL) and DeltaV(IT) in uninjured tissue within critical values were then computationally determined as a function of duration of surgery. Bioimpedance data showed that the differences in DeltaV(IT)/V(INF) ratios between uninjured and injured tissues were significant only for surgical duration > or = 3 h (0.30 +/- 0.17% x kg/mL vs 1.55 +/- 0.73% x kg/mL, P < 0.0001). Differences of DeltaV(IT)/V(INF) ratios between surgical durations <3 and > or = 3 h were found only for injured tissue (0.45 +/- 0.35% x kg/mL vs 1.55 +/- 0.73% x kg/mL, P = 0.003). The range of fluid infusion rates required to maintain DeltaV(PL) and DeltaV(IT) within the critical values (>-15% and <20%, respectively) was wide for short-duration surgery (2-18.5 mL x kg(-1) x h(-1) for a 2 h-surgery), whereas it was narrow for long-duration surgery (5-8 mL x kg(-1) x h(-1) for a 6 h-surgery). Based on our model, it should be possible to increase the fluid infusion rate without significant interstitial edema for abdominal surgery of <3 h duration. However, our model predicts that restrictive fluid management should be used in abdominal surgery of >6 h duration to avoid excessive interstitial edema.

Furosemide does not improve renal recovery after hemofiltration for acute renal failure in critically ill patients: A double blind randomized controlled trial*

To study the potential beneficial role of furosemide in resolving renal failure after hemofiltration in mechanically ventilated critically ill patients. Single-center randomized, double blind, placebo-controlled study. A 13-bed mixed intensive care unit (ICU) in a teaching hospital. Patients who had been treated with continuous venovenous hemofiltration were included. After the end of continuous venovenous hemofiltration, the urine of the first 4 hours was collected for measuring creatinine clearance. Patients were subsequently randomized for furosemide (0.5 mg/kg/hr) or placebo by continuous infusion. To prevent hypovolemia, the rate of fluid infusion was adapted every hour and was set as the urinary production of the previous hour. End points were renal recovery (creatinine clearance more than 30 mL/min or stable serum creatinine without renal replacement therapy) in the ICU and in the hospital. Seventy-two patients were included and 71 were eligible for the analysis. The 36 furosemide-treated patients had a significantly increased urinary volume compared with the 35 placebo-treated patients (median 247 mL/hr (interquartile range [IQR] 774 mL/hr) vs. 117 mL/hr (IQR 158 mL/hr), p = 0.003) and greater sodium excretion (median 73 mmol/L (IQR 48) vs. 37 (IQR 48) mmol/L, p = 0.001). In the furosemide group 25 patients and in the placebo group 27 patients showed recovery of renal function at ICU discharge (p = 0.46). Two patients of the furosemide group needed long-term dialysis dependency (p = 0.23). Furosemide by continuous infusion in the recovery phase of hemofiltration-dependent acute kidney failure did increase urinary volume and sodium excretion but did not lead to a shorter duration of renal failure or more frequent renal recovery.

Fluid therapy for severe acute pancreatitis in acute response stage

Background Fluid therapy for severe acute pancreatitis (SAP) should not only resolve deficiency of blood volume, but also prevent fluid sequestration in acute response stage. Up to date, there has not a strategy for fluid therapy dedicated to SAP. So, this study was aimed to investigate the effects of fluid therapy treatment on prognosis of SAP. Methods Seventy-six patients were admitted prospectively according to the criteria within 72 hours of SAP onset. They were randomly assigned to a rapid fluid expansion group (Group I, n=36) and a controlled fluid expansion group (Group II, n=40). Hemodynamic disorders were either quickly (fluid infusion rate was 10-15 ml·kg-1·h-1, Group I) or gradually improved (fluid infusion rate was 5-10 ml·kg-1·h-1, Group II) through controlling the rate of fluid infusion. Parameters of fluid expansion, blood lactate concentration were obtained when meeting the criteria for fluid expansion. And APACHE II scores were obtained serially for 72 hours. Rate of mechanical ventilation, incidence of abdominal compartment syndrome (ACS), sepsis, and survival rate were obtained. Results The two groups had statistically different (P &lt;0.05) time intervals to meet fluid expansion criteria (Group I, 13.5±6.6 hours; Group II, (24.0±5.4) hours). Blood lactate concentrations were both remarkably lower as compared to the level upon admission (P &lt;0.05) and reached the normal level in both groups upon treatment. It was only at day 1 that hematocrit was significantly lower in Group I (35.6%±6.8%) than in Group II (38.5%±5.4%) (P&lt;0.01). Amount of crystalloid and colloid in group I ((4028±1980)ml and (1336±816)ml) on admission day was more than those of group II ((2472±1871)ml and (970±633)ml). No significant difference was found in the total amount of fluids within four days of admission between the two groups (P&gt;0.05). Total amount of fluid sequestration within 4 days was higher in Group I ((5378±2751)ml) than in Group II ((4215±1998)ml, P &lt;0.05). APACHE II scores were higher in Group I on days 1, 2, and 3 (P &lt;0.05). Rate of mechanical ventilation was higher in group I (94.4%) than in group II (65%, P &lt;0.05). The incidences of abdominal compartment syndrome (ACS) and sepsis were significantly lower in Group II (P &lt;0.05). Survival rate was remarkably lower in Group I (69.4%) than in Group II (90%, P &lt;0.05). Conclusions Controlled fluid resuscitation offers better prognosis in patients with severe volume deficit within 72 hours of SAP onset.

A teaching programme to improve compliance with guidelines about management of hypovolaemia in the emergency department

Hypovolaemia is one of the most severe clinical conditions in patients admitted to the paediatric emergency department (PED). Both absolute hypovolaemia (e.g. severe dehydration) and relative hypovolaemia (distributive shock, due for instance to sepsis (1) can cause multiple organ failure. Faster correction of hypovolaemia is associated with better outcomes (2,3). International consensus guidelines about emergent fluid resuscitation of children with sepsis and hypovolaemia were issued recently (2,4,5). In 2005, the senior physicians at our PED noticed poor compliance with these recommendations in patients who had hypovolaemia diagnosed in the PED. Colloids were overused, and fluid infusion rates were usually lower than recommended. Optimal initial resuscitation for hypovolaemia in children may lead to a significant decrease in mortality (6). We therefore designed a teaching programme (TP) to improve compliance with the recommendations. To design and to evaluate the TP, we conducted a beforeafter study. We collected data on all fluid challenges given during a 6-week period in winter. We then developed a TP taking into account the main points of the international consensus guidelines. All 12 physicians working in the PED followed the TP. Data on fluid challenges were collected during the same 6-week winter period of the following year. We prospectively identified all patients who received fluid challenges during a 6-week period in the winter of 2006 encompassing the gastroenteritis seasonal peak in incidence. To this end, each of the 12 physicians working full-time or part-time at our PED was informed of the study aim and design. Each time they prescribed a fluid challenge during the study period, they completed a dedicated anonymous form to record the patient’s age, weight and main diagnosis; the fluid, volume and infusion duration; and the vascular access. According to standard practice in our PED, a senior physician reviewed all medical charts of PED patients daily. In addition, the main investigator checked once a week that all fluid challenges prescribed by the physicians were properly recorded. At the end of the period, we evaluated compliance with guidelines and we assessed the knowledge of the physicians by asking them how they would manage a patient described in a fictional scenario. Although their answers to the fictional scenario agreed closely with international consensus guidelines (data not shown), the review of fluid challenges showed excessive colloid use and insufficient infusion rates (Table 1). We used these data to build a 1-h TP on the emergent management of hypovolaemia in infants in accordance with recent international consensus guidelines (2,3). This 1-h TP was delivered each day during one week to ensure that all 12 physicians participated, regardless of their schedule. Key points in the TP were use of 20 mL/kg per fluid challenge in infants older than 1 month, use of the highest possible infusion rate and preferential use of saline (2,3). Three recent articles and a summary of the main recommendations were given to each physician. All physicians felt the TP was adapted to their medical practice, although three would have liked a longer programme. Finally, we prospectively recorded all fluid challenges given during the same 6-week period of the following winter (2007). Quantitative (medians [minimum–maximum]) and qualitative values were compared using the Mann–Whitney and Chi-square tests, respectively. Values of p < 0.05 were considered statistically significant. Changes in the main fluid challenge parameters between the two periods are reported in the Table. The physician in charge of the study excluded one fluid challenge

Errors of intravenous fluid infusion rates in medical inpatients

Prescriptions for intravenous (i.v.) fluids in hospitals may not be closely adhered to. This study prospectively examined whether prescribed i.v. fluids are administered at the correct rate. During a four-week period, the i.v. infusion rates in patients requiring continuous i.v. fluids and cared for by a single medical team in a district hospital were studied. The periods over which i.v. crystalloid fluid bags were administered were compared with the time prescribed. Of a total 207 bags, 53 (26%) were correctly administered at the prescribed rate (percentage error 10% to -10%), 138 bags (67%) were infused too slowly and 16 bags (8%) were infused too fast. Overall, the median (interquartile range) absolute percentage error (positive or negative) for all infused bags was 23% (9.7-50). Thirty-nine per cent of bags were infused accurately when a metered pump was used, compared to 21% of bags infused accurately when a metered pump was not used (p < 0.01). Marked inaccuracies in i.v. fluid infusion rates are common, and do not seem to be perceived by staff as important. Metered pumps improve accuracy. Increased awareness of such errors, and the routine use of metered pumps should help improve the accuracy of i.v. fluid infusion rates.

Crystalloid infusion rate during fluid resuscitation from acute haemorrhage

Information is lacking concerning optimal infusion rates of crystalloid during resuscitation from acute haemorrhage. In this study, a mathematical model was used to predict infusion volume of crystalloid needed to restore and maintain blood volume after acute haemorrhage. The scenario was a haemorrhage of 15 ml kg(-1) over 30 min in a 70 kg man. A bolus of crystalloid was administered at a rate of 40, 60, 80, 100, or 120 ml kg(-1) h(-1) until blood volume was restored. Fluid infusion rate needed to maintain blood volume for a further 1 h was computed. Blood volume was restored earlier at high bolus infusion rates compared with low bolus infusion rates (6 min at 120 ml kg(-1) h(-1) vs 63 min at 40 ml kg(-1) h(-1)). Fluid infusion rates for blood volume maintenance approached 33 ml kg(-1) h(-1) irrespective of bolus infusion rates. The restoration fluid volume at 40 ml kg(-1) h(-1) was 2.9 litre, three times that at 80-120 ml kg(-1) h(-1). The maintenance fluid volume at 80-120 ml kg(-1) h(-1) was 2.9 litre, 0.6 litre more than that at 40 ml kg(-1) h(-1). During the blood volume maintenance, the interstitial volume increased to 3.8 litre above normal at 40 ml kg(-1) h(-1) and to 2.5 litre at 80-120 ml kg(-1) h(-1). Bolus crystalloid infusion exceeding 80 ml kg(-1) h(-1) may not increase effectiveness of fluid resuscitation. Crystalloid resuscitation for more than 2 h may be detrimental in view of an excessive net fluid retention.

Acute hyperglycemic emergencies in children with type 2 diabetes

Acute hyperglycemic emergencies in children with type 2 diabetes

Comparison between normal saline and a polyelectrolyte solution for fluid resuscitation in severely dehydrated infants with acute diarrhoea

The optimal intravenous solution for rehydration of infants and children with severe dehydration is debated. The aim was to compare the efficacy of a polyelectrolyte solution (group PS) with sodium chloride 0.9% solution (group NS) in rapid parenteral rehydration of severely dehydrated infants with acute diarrhoea. Primary outcomes were volume and time to hydration. Secondary outcomes were urea, creatinine, electrolytes, glucose, arterial pH and bicarbonate levels. Patients were assigned randomly and openly to one of the two treatment groups. Severe dehydration was defined as one or more of the following associated with any other sign of dehydration: depressed consciousness, a weak or absent pulse or capillary refill time > 10 sec. Peripheral blood samples for chemical pathology were collected before and after rapid fluid therapy. The mean age of the 36 enrolled infants was 9.1 mths. All had depressed consciousness or severe hypotension/shock. The fluid infusion rate was 50 ml/kg/hr until haemodynamic stability was restored (absence of severe hypotension and two urine emissions). Fluid volume, time to rehydration and weight before and after rehydration were recorded. All infants recovered full pulse within 1 hr; most had a better level of consciousness or capillary refill <3 sec. Group NS (15 infants) showed (before and after treatment, respectively) a decrease of plasma potassium (3.4 to 3.1 mmol/L, p=0.07), bicarbonate (13.3 to 12.2 mmol/L, p=0.01) and glucose (8.2 to 5.8 mmol/L, p<0.01). Group PS (21 infants) showed a decrease of potassium (4.4 to 3.2 mmol/L, p<0.01) but an increase in bicarbonate (11.6 to 13.3 mmol/L, p<0.01) and glucose (11.4 to 14.8 mmol/L, p=0.08). Polyelectrolyte solution was as effective as normal saline on volume expansion and better for correcting acidosis.

Fluid resuscitation of trauma patients: how fast is the optimal rate?

The Advanced Trauma Life Support guidelines recommend an initial rapid infusion of fluid (1-2 L) in trauma and hemorrhage victims as a diagnostic procedure to aid treatment decisions. Although patient response to initial fluid resuscitation is the key to determining therapeutic strategies, the appropriate rate of infusion is not clearly defined. Ninety-nine adult (age >16 years) blunt trauma victims with hypotension were enrolled. Patients were classified into 3 groups according to hemodynamic state after initial fluid resuscitation and requirement of surgical intervention. Total volume and rate of infusion differed significantly between the groups ( P < .05). Patients requiring fluid administration at higher rate were all hemodynamically unstable and required immediate surgical intervention. Moreover, rate of infusion was the best predictor of the patients who required immediate surgical intervention. Moderate fluid infusion rate should be considered to allow identification of the patient's response to initial fluid resuscitation.

Index of Suspicion in the Nursery

Index of Suspicion in the Nursery

Neonatal Hemodialysis and Continuous Renal Replacement Therapy

After completing this article, readers should be able to: 1. Describe catheters, dialyzers, and blood lines in hemodialysis for neonates. 2. Explain the blood prime and hemodialysis prescription in hemodialysis for neonates. 3. List potential complications of hemodialysis for neonates. 4. Identify the types of continuous renal replacement therapy (CRRT) in neonates. 5. Explain the dialysis prescription and anticoagulation options for CRRT in neonates. 6. List potential complications of CRRT in neonates. Since the mid-1980s, when dialysis manufacturers began making dialyzers and blood circuit paths that required smaller extracorporeal volumes, hemodialysis has been used successfully to manage renal failure in neonates and infants. Compared with peritoneal dialysis (PD), which is analogous to the “family sedan” in the world of dialysis (slower, more predictable, easier to operate), hemodialysis is the “race car.” Hemodialysis is capable of removing fluids and solutes much more rapidly than is PD. Unlike PD, hemodialysis uses catheters that access the intravascular space directly. Despite the advantages of hemodialysis, the process in neonates is technically more challenging than PD due to the very attributes that make it so effective. Rapid removal of intravascular fluids, exceeding the rate of refill from the extravascular space, causes problems with hypotension due to direct reduction in intravascular volume. Similarly, rapid rates of solute clearance can cause problems with increased intracranial pressure. Catheter placement and maintenance of catheter function can constitute a significant obstacle to hemodialysis. Hemofiltration is very similar to hemodialysis in that patient blood is circulated through an artificial kidney. However, hemofiltration differs from hemodialysis in three significant aspects. First, the hemofilter has larger pore sizes than the standard dialyzer, which allows for excellent fluid removal, even with low blood flow rates, and better larger molecule clearance. Second, hemofiltration runs continuously without the continuous presence of a dialysis nurse. Third, typical hemofiltration uses a pre- or postdilution …

Magnesium sulfate tocolysis and pulmonary edema: The drug or the vehicle?

This study was undertaken to determine the: (1) risk factors for developing pulmonary edema associated with magnesium sulfate (MgSO4) tocolysis; (2) mean latency period to diagnosis; (3) role of maternal transport; and (4) safety of continued therapy. A total of 150 antenatal patients treated for preterm labor with MgSO4 were identified for this retrospective, case-control study. Cases were compared 1:2 with controls in regard to maternal demographics, MgSO4 concentration and infusion rates, maternal transport status, and maternal net fluid balance. Risk factors for developing pulmonary edema include: greater MgSO4 and intravenous fluid infusion rates, less concentrated MgSO4, infection, multiple gestations, concomitant tocolytics, large positive net fluid balances, and maternal transport. The mean latency period to diagnosis was 1.96 days. Six percent of patients had recurrence if MgSO4 tocolysis was continued. MgSO4 and intravenous fluid rates are both associated with the development of pulmonary edema. Once appropriately treated, MgSO4 tocolysis can be continued with little risk of recurrence.

Blunt Splenic Injury: Usefulness of Transcatheter Arterial Embolization in Patients with a Transient Response to Fluid Resuscitation

To evaluate the use of transcatheter arterial embolization (TAE) in hemodynamically unstable patients with blunt splenic injury in whom there is a transient response to initial fluid resuscitation. Human subject committee approval and informed consent were obtained. Angiography was performed in patients with contrast material extravasation and/or splenic injury of grade III or higher (American Association for the Surgery of Trauma criteria) at computed tomography (CT). TAE was performed when angiograms showed disruption of terminal splenic branches or arterial extravasation. Among 104 patients with splenic injury, the 15 patients (10 male, five female; mean age, 36.2 years) with a transient response to fluid resuscitation were the subjects of this study. A post hoc analysis was performed for CT grades, angiographic findings, associated injuries, and hemodynamic status in the subjects. Among 15 patients with a transient response, two had grade III, 11 had grade IV, and two had grade V injuries at CT. Six patients had associated injuries that required TAE. TAE of the spleen and associated injuries was successfully performed in all patients. The mean systolic blood pressure and shock index at the start of TAE were 84.2 mm Hg +/- 9.2 (standard deviation) and 1.46 +/- 0.30, respectively, and those at the completion of TAE were 132.1 mm Hg +/- 18.7 and 0.77 +/- 0.21, respectively (P < .001). The fluid infusion rate within 24 hours after the completion of TAE (132.1 mL/h +/- 71.1) was lower than that from the completion of the initial fluid resuscitation until the completion of TAE (1230.6 mL/h +/- 264.8) (P < .001). TAE for blunt splenic injury can be performed successfully even in hemodynamically unstable patients with a transient response to initial fluid resuscitation.

Effects of high volume veno-venous hemofiltration on MODS with cerebral edema

目的 探讨高容量静脉静脉血液滤过(HV-CVVH)治疗合并严重脑水肿的多器官功能障碍(MODS)的临床效果.方法2 3例严重脑水肿(GCS评分5～6分)同时存在MODS但无合并肾功能衰竭患者(APACHE II评分19～26)分为两组:HV-CVVH组(12例),血流量为250～300ml,置换液为3.0～4.0L/h;对照组(1 3例)按常规治疗.持续监测生命体征,检测血气分析和细胞因子.结果HV-CVVH组治疗期间无死亡,与对照组比较,治疗后4～6 小时平均动脉压开始显著上升,多巴胺输注速度减少,电解质和酸碱平衡维持在正常水平,氧合指数(PO2/FiO2)显著上升,血浆乳酸、IL-1 β、IL-6、TNF-α水平较对照组显著下降(P＜0.05～0.01),GCS和APACHE II评分显著改善.三周后生存率比较,HV-CVVH组10例(10/12,83.3%),对照组5例(5/13,38.5%).结论高容量静脉静脉血液滤过(HV-CVVH)治疗MODS合并严重脑水肿有良好效果,这与其能较好地调节内环境、清除体内细胞因子和乳酸等炎性介质,改善的血流动力学、氧合功能有关。

Life span of peripheral intravenous cannula in a neonatal intensive care unit of a developing country

The use of peripheral intravenous cannulas (IVCs) in the care of sick newborns is a common practice. IVCs, priced five times higher than conventional steel needles, can be more cost effective if insight is available on the variables affecting their life span in situ. The present report summarizes the efforts made to ascertain these factors in a neonatal intensive care unit (NICU) of a developing country. A total of 186 peripheral IVCs (24-gauge teflon) were used in 78 newborns amounting to 7,583 hours of IV therapy (mean, 40.8 hr per cannula; range, 1–136 hr). Of these, 25 cannulas were removed selectively and 84, 50, 17, and 10 were removed for swelling, dislodgement/leakage, blockage, and local erythema, respectively. The median survival time of IVC as expressed by Kaplan-Meir survival analysis was 40 hours (SE, 2.49; 95% confidence interval, 35.12–44.88). Birth weight, gestation, application of splint, fluid and glucose infusion rate, site of cannulation, and administration of ampicillin, gentamicin, amikacin, vancomycin, phenobarbitone, blood products, or calcium gluconate did not influence the median life span of IVCs. Children receiving cefotaxime had a significantly lower median survival time as compared with those not receiving it (36 vs 47 hours, p = .007). Median survival time of IVCs in our set-up was comparable with those in developed countries and was not governed by the cannula or patient variables. Cefotaxime use led to decreased survival of IVCs; though this effect appeared to be related to the mode of administration rather than to the drug per se.

Influence of the type and rate of subarachnoid fluid infusion on lethal neurogenic pulmonary edema in rats.

In patients who experience sudden death from spontaneous subarachnoid hemorrhage, more than 90% present with acute pulmonary edema. The underlying pathogenesis of this complication is poorly understood. In addition, the specific role of the extravasated blood products and the associated elevation in intracranial pressure leading to the systemic and pulmonary effects during subarachnoid hemorrhage are not well established. The authors tested a new model of acute and severe subarachnoid hemorrhage comparing fresh whole autologous blood (n = 20) with 5% albumin (n = 19) injected at two different rates (35 seconds versus 24 minutes) into the cisterna magna of anesthetized, mechanically ventilated rats. Cerebral and systemic hemodynamics and the corresponding pulmonary function were evaluated. The type of fluid injected had no influence on survival or hemodynamic and respiratory parameters. Rapid infusion of either blood or albumin (n = 14) produced an acute and transient rise in intracranial pressure (37.9 +/- 3.5 mm Hg) associated with systemic hypertension and increased cerebral perfusion pressure that was sustained in survivors but not in nonsurvivors. Slow infusion (n = 23) produced a more progressive increase in intracranial pressure to 31.2 +/- 7.1 mm Hg with a parallel and sustained increase of systemic blood pressure and preserved cerebral perfusion pressure in survivors, but produced a pattern of more severe hypertension followed by hypotension in nonsurvivors. Sixty-four percent of animals (rapid infusion) and 48% of animals (slow infusion) survived the challenge and presented no pulmonary alterations. In contrast, nonsurviving rats developed reduced lung compliance and gas exchange, an increased alveolar-arterial protein concentration ratio (0.36 +/- 0.02 versus 0.17 +/- 0.03 in survivors; P <.0001), and increased lung weight (5.7 +/- 0.3 g versus 2.0 +/- 0.1 g; P <.0001), demonstrating a fulminant increased permeability pulmonary edema, leading to death within one hour. These results indicate that the chosen rapid- and slow-injection rates resulted in a similar death rate of 50%. Mortality was similar for blood and albumin administration, pulmonary edema occurred in nonsurvivors in both the rapid- and slow-injection groups, and pulmonary edema is associated with more severe hypertension in the slow-injection group. Furthermore, these results suggest that the development of neurogenic pulmonary edema that is characterized by an acutely increased capillary permeability to proteins is independent of the degree of intracranial pressure increase or the type of fluid administrated.

Simulation of potassium extraction by continuous haemodiafiltration.

Prediction of potassium extraction rates by continuous haemodiafiltration (CHDF) is useful for safe management of potassium levels in patients with hyperkalaemia. For this purpose, we developed a formula to predict the quantity of potassium extracted by CHDF. We hypothesized that potassium concentration in efflux dialysate was completely saturated by the influx blood, and potassium concentration in efflux blood was calculated based on this hypothesis. To check the accuracy of the calculation, potassium concentration was measured in efflux blood, and values were compared to predicted concentrations. Predicted potassium concentrations demonstrated good correlation to the measured values (95% confidence range, -0.32 to 0.58 mmol/l). These results confirmed that our hypothesis is applicable to clinical use of CHDF. Based on our observations, we created a formula to accurately predict the amount of potassium (dK) extracted by CHDF: dK=(Cb-Cd)xQd+CbxQf-CsxQs (Cb: plasma potassium concentration; Cd: potassium concentration in a dialysate; Cs: potassium concentration in the replacement fluid; Qd: dialysis rate; Qf: filtration rate and Qs: infusion rate of replacement fluid).

Prognosis of Body Fluid Level by Fuzzy Logic Technique

Surgical fluid replacement is a critical issue in medicine as the fluid volume excess or deficit can both complicate the patient's condition. Currently, the administration of fluid volume is carried out primarily based on the experience and expertise of the anaesthetist as there is no analytical method available to estimate the patient's fluid level. The development of a decision support system (DSS) to assist the anaesthetist in estimating the required fluid infusion rate for a particular patient has been the focus of this research paper. The DSS is developed based on Fuzzy Logic Control (FLC) technique which is ideal for developing input/output models in an unstructured and/or complex environment. The fuzzy rules used in the DSS are derived automatically from the clinical data produced in surgical operations. The DSS employs a Multi Rule Base (MRB) learning scheme to adapt its model according to the significant variation in the physiological parameters of a patient. The performance of the developed algorithms is validated through experimental work using clinical data. The results obtained so far are encouraging.