Hypertonic-hyperoncotic solutions in open-heart surgery

Management of Congestion and Diuretic Resistance in Heart Failure

We present the case of a patient with heart failure and severe congestion who was responding poorly to diuretic therapy. We discuss the key problems concerning the pathophysiology and bedside therapeutic approach to congestion and fluid overload in this clinical setting, and we give practical suggestions to overcome congestion, especially in the setting of diuretic resistance and worsening renal function. We conclude that the application of key pharmacokinetic and pharmacodynamic principles of diuretic therapy, along with in-depth knowledge of the pathophysiology of heart failure, still represent the cornerstones for a correct approach to decongestive therapy in these patients.

Noradrenaline and dobutamine effects on the volume expansion with normal saline in rabbits subjected to hemorrhage

PURPOSE:

To evaluate the effects of dobutamine (DB), noradrenaline (NA), and their combination (NADB), on volume retention in rabbits submitted to hemorrhage.

METHODS:

Thirty six rabbits were randomly divided into 6 groups: SHAM, Control, Saline, DB, NA, DB+NA. All the animals, except for SHAM, were subjected to hemorrhage of 25% of the calculated blood volume. Control animals were replaced with their own blood. The other groups received NSS 3 times the volume withdrawn. The intravascular retention, hematocrit, diuresis, central venous pressure, mean arterial pressure, NGAL, dry-to-wet lung weight ratio (DTWR) and the lung and kidney histology were analyzed.

RESULTS:

Replacement with NSS and NA, DB or NA+DB did not produce differences in the intravascular retention. After hemorrhage, the animals presented a significant decrease in the MAP and CVP, which were maintained until volume replacement. Regarding NGAL, dry-to-wet-lung-weight ratio, lung and kidney histology, there were no statistical differences between the groups.

CONCLUSION:

The use of noradrenaline, dobutamine or their combination did not increase the intravascular retention of volume after normal saline infusion.

Effects of catecholamines on volemic replacement with saline solution and the impact on heart rate variability in rabbits subjected to hemorrhage. A study by spectral analysis

PURPOSE

To verify the effects of different catecholamines on volemic expansion and on the autonomic nervous system in rabbits that were subjected to hemorrhage.

METHODS

Twenty four rabbits subjected to hemorrhage (with a 25% loss of blood volume) and were randomly divided into four experimental groups: 1) HEMO Group underwent replacement with their own blood in an equal volume; 2) SS Group underwent replacement with saline solution (SS) in a volume that corresponded to three times the removed blood volume; 3) ISP Group underwent replacement with SS and isoprenaline; 4) FNL Group underwent replacement with SS and phenylephrine. Spectral Analysis of the heart rate and heart rate variability were performed from the recorded data. Hematocrit was measured throughout the experiment.

RESULTS

Replacement with SS and an α- or β-agonist did not produce differences in the intravascular retention compared to replacement with SS alone. An analysis of HRV showed that the FNL group maintained the LF/HF ratio better than ISP and SS.

CONCLUSIONS

No difference in vascular retention when α- or β- agonists were added to SS during post-hemorrhagic recovery. The animals in the FNL group maintained the integrity of the autonomic response within normal physiological standards during hemorrhagic stress.

Short-term effects of hypertonic saline solution in acute heart failure and long-term effects of a moderate sodium restriction in patients with compensated heart failure with New York Heart Association class III (Class C) (SMAC-HF Study)

INTRODUCTION

Hypertonic saline solution (HSS) and a moderate Na restriction plus high furosemide dose showed beneficial effects in compensated heart failure (HF), in short and long terms. The study was aimed to verify the effects of this combination on hospitalization time, readmissions and mortality in patients in New York Heart Association (NYHA) class III.

METHOD

Chronic ischemic or nonischemic cardiomyopathy uncompensated patients with HF in NYHA III functional class with ejection fraction <40%, serum creatinine <2.5 mg/dL, blood urea nitrogen <60 mg/dL and reduced urinary volume were single-blind randomized in 2 groups: the first group received a 30-minute intravenous infusion of furosemide (250 mg) plus HSS (150 mL) twice daily and a moderate Na restriction (120 mmol); the second group received furosemide intravenous bolus (250 mg) twice a day, without HSS and a low Na diet (80 mmol); both groups received a fluid intake of 1000 mL/d. After discharge, the HSS group continued with 120 mmol Na/d; the second group continued with 80 mmol Na/d.

RESULTS

A total of 1771 patients (881 HSS group and 890 without HSS group) met inclusion criteria: the first group (881 patients), compared with the second (890 patients), showed an increase in diuresis and serum Na levels, a reduction in hospitalization time (3.5 + 1 versus 5.5 + 1 days, P < 0.0001) and, during follow-up (57 + 15 months), a lower rate in readmissions (18.5% versus 34.2%, P < 0.0001) and mortality (12.9% versus 23.8%, P < 0.0001); the second group also showed a significant increase in blood urea nitrogen and serum creatinine.

CONCLUSION

This study suggests that in-hospital HSS administration, combined with moderate Na restriction, reduces hospitalization time and that a moderate sodium diet restriction determines long-term benefit in patients with NYHA class III HF.

Rubbing salt into wounds: hypertonic saline to assist with volume removal in heart failure

Traditionally accepted management strategies for patients with heart failure include sodium and fluid restriction, neurohormonal blockade, and the use of loop diuretics to achieve and maintain euvolemia. Despite continued advances in medical and device therapy, fluid management remains a significant problem in patients with the cardiorenal syndrome (manifested as diuretic resistance and worsening renal function with more aggressive attempts at volume removal). This article examines the counterintuitive use of hypertonic saline as a potential therapy to facilitate diuresis in patients with decompensated heart failure and diuretic resistance. Low-volume hypertonic saline administration offsets counterproductive neurohormonal upregulation, transiently improves hemodynamics, and promotes renal sodium excretion with accompanied net water loss and preservation of renal function. This "new" therapeutic tool should be explored further as an adjunct to current medical therapies in the management of patients with refractory volume overload.

Changes in muscle compartment pressure after cardiopulmonary bypass

PURPOSE

Hemodilution and inflammation lead to edema and increased muscle compartment pressure after cardiac surgery. The aim of this study was to find whether muscle compartment pressure was affected by the addition of albumin and mannitol to the pump prime, heparin coating or leukocyte depletion. Additionally, we studied the relationship between intraocular pressure and lower leg muscle compartment pressure. Edema during and following cardiac surgery is due to hemodynamic, osmotic and inflammatory changes, according to Starling's Law. We attempted to influence the osmotic balance and reduce the inflammatory response in order to reduce the edema.

METHODS

Thirty-six patients who underwent cardiac surgery were randomly allocated into four groups. Group A received albumin and mannitol into the pump prime. Group B had an, heparin-coated perfusion system, Group C had a leukocyte-depletion arterial line filter and Group D was the control group, where intraocular pressure was also measured.

RESULTS

Lower leg muscle compartment pressure increased significantly during and after cardiac surgery in all groups, but this increase was significantly less in Group A than in the control group 24 h after surgery. No correlation was found between muscular compartment pressure and intraocular pressure. The intraocular pressure profile is different from the muscular compartment pressure and recovers much faster.

CONCLUSION

Lower leg muscle compartment pressure and intraocular pressure behave differently during and after cardiac surgery. Albumin and mannitol added to the pump prime decreases muscle compartment pressure after cardiac surgery.

Hyperosmolarity enhances the lung capillary barrier

Although capillary barrier deterioration underlies major inflammatory lung pathology, barrier-enhancing strategies are not available. To consider hyperosmolar therapy as a possible strategy, we gave 15-minute infusions of hyperosmolar sucrose in lung venular capillaries imaged in real time. Surprisingly, this treatment enhanced the capillary barrier, as indicated by quantification of the capillary hydraulic conductivity. The barrier enhancement was sufficient to block the injurious effects of thrombin, TNF-alpha, and H2O2 in single capillaries, and of intratracheal acid instillation in the whole lung. Capillary immunofluorescence indicated that the hyperosmolar infusion markedly augmented actin filament formation and E-cadherin expression at the endothelial cell periphery. The actin-depolymerizing agent latrunculin B abrogated the hyperosmolar barrier enhancement as well as the actin filament formation, suggesting a role for actin in the barrier response. Furthermore, hyperosmolar infusion blocked TNF-alpha-induced P-selectin expression in an actin-dependent manner. Our results provide the first evidence to our knowledge that in lung capillaries, hyperosmolarity remodels the endothelial barrier and the actin cytoskeleton to enhance barrier properties and block proinflammatory secretory processes. Hyperosmolar therapy may be beneficial in lung inflammatory disease.

Hypertonic resuscitation: physiologic mechanisms and recommendations for trauma care

Hypertonic saline solutions, with or without added colloid, have received extensive evaluation as volume expanders in both animal studies and clinical trials. Most studies have used 7.5% NaCl/6% dextran 70 (HSD). HSD's primary mechanism of action is rapid osmotic mobilization of cellular water into the blood volume. The measured volume expansion efficiency of HSD is equal to 10 times that of lactated Ringer's solution. Part of HSD's effectiveness is because of the hyperosmotic vasodilation of both systemic and pulmonary vessels. Increased cardiac effectiveness occurs because of the combination of increased preload (venous return) and reduced afterload (vasodilation). Increased cardiac contractility also has been reported in several studies and may play a role, but other studies refute a direct effect on contractility. HSD has been shown to be effective and safe with preexisting dehydration. Animal studies of immune function suggest that increased osmolarity prevents T-cell depression and decreases neutrophil activation. Several perioperative and eight randomized, blinded trauma trials have shown safety and reduced volume needs and suggest increased survival, particularly in head- and penetrating-injury patients. Infusion rates for HSD of 10 to 20 minutes may be recommended for the initial resuscitation of hypotensive trauma.