The management of interstitial pulmonary edema

The end of the crystalloid era? A new approach to peri-operative fluid administration

The metabolic response to surgery causes sodium and water retention. It does not seem logical to pour crystalloid solutions into patients in the peri-operative period, particularly when these solutions can cause deterioration in lung function. Plasma volume must be maintained to prevent a decreased blood flow to vital organs such as the kidneys. Blood or colloid solutions, not crystalloid solutions, should be used for this purpose, since the latter are distributed throughout the whole extracellular space and are less effective in maintaining plasma volume. Water given as 5% dextrose should be given in minimal quantities to maintain intracellular hydration. Patients undergoing minor to moderate surgery when they are likely to be drinking within 24 hours do not usually require any intravenous infusion. Moreover, to administer intravenous fluids to these patients may cause harm. No fluid regimens should be inflexible and the patient's size, age and fluid losses should be taken into account.

Another look at ARDS

ARDA is a common clinical problem resulting in acute respiratory failure in many and death in the majority of patients with a wide variety of direct and indirect pulmonary insults. ARDS is widely recognized and appropriately treated by empiric supportive care. Pharmacologic approaches to support the circulation are established. The use of corticosteroids remains controversial. The future depends upon unraveling the biologic mysteries which lead to the cascade of events which result in ARDA. This will establish a basis for further improvements in management.

Albumin treatment following major surgery. I. Effects on plasma oncotic pressure, renal function and peripheral oedema

The effect of a 20% albumin solution on plasma oncotic pressure, renal function and peripheral oedema was investigated in 30 adult patients undergoing elective major abdominal surgery. Half of them received an average of 173 g of albumin between the end of the operation and the 5th postoperative day, in accordance with a standardized scheme. Otherwise the same schedules for fluid therapy and blood replacement were followed in all patients. Postoperatively, serum albumin and plasma oncotic pressure were fairly normal in the albumin group, but decreased by 28% and 24% in the control group. The difference between the groups was statistically significant during the first week, but disappeared during the second week. Arm and thigh circumferences increased postoperatively to a similar extent in both groups. There were no apparent differences in circulatory variables, alveolo-arterial oxygen tension difference, incidence of wound infection or postoperative restoration of intestinal activity between the groups. Although renal and thromboembolic complications occurred only in the control group, the material is too small to permit any conclusions to be drawn from the possible difference in renal function and morbidity between the groups. The limited availability and high cost of albumin require strict indications for its use. Our results so far have failed to justify routine administration of concentrated albumin postoperatively.

Plasma oncotic pressure and plasma protein concentration in patients following thermal injury

Plasma oncotic pressure (POP), albumin and total protein were measured in 14 patients with thermal injuries varying extent from 16 to 90% of the body surface. The patients were treated with large amounts of balanced salt solutions in the initial phase. There was an abrupt, pronounced decrease in POP to about 51% of the normal during the first 24 h. Despite the low POP values (minimum 0.78 kPa) and marked peripheral oedema, no patient had overt pulmonary oedema. Clinical and roentgenological evidence of pulmonary dysfunction during the initial period was only seen in conjunction with lung burn or aspiration pneumonitis. Oedema-preventing mechanism and inability to detect interstitial pulmonary oedema are discussed as possible explanations. There was no significant correlation between decrease in POP and mortality, but low POP values seemed to persist longer in the patients who died.

Relationship between colloid osmotic pressure and pulmonary artery wedge pressure in patients with acute cardiorespiratory failure

Close relationships between progressive respiratory failure, roentgenographic signs of pulmonary opacification and decreases in the difference between colloid osmotic pressure of plasma and the pulmonary artery wedge pressure (colloid-hydrosatic pressure gradient) were demonstrated in 49 critically ill patients with multisystem failure, in patients in shock. The potential importance of this relationship is underscored by the observation that fatal progression of pulmonary edema was related to a critical reduction in the colloid-hydrostatic pressure gradient to levels of less than 0 mm Hg. More often, reduction in colloid osmotic pressure rather than increases in left ventricular filling pressure (pulmonary artery wedge pressure) accounted for the decline in colloid-hydrostatic pressure gradient. Routine measurement of colloid osmotic pressure, preferably in conjunction with pulmonary artery wedge pressure, is likely to improve understanding of the mechanisms of acute pulmonary edema.

Acute hypoproteinemic fluid overload: its determinants, distribution, and treatment with concentrated albumin and diuretics

We simulated the use of massive volumes of crystalloid fluids as a treatment of acute plasma loss in a standardized experimental model and studied the factors determining the retention or excretion of the resulting acute hypoproteinemic fluid overload, its distribution within the body, and its treatment with concentrated albumin and diuretics. In accordance with the classic Starling concept, the serum protein level, i.e. the serum colloid osmotic pressure, determined the excretion/retention ratio of a given water and sodium load. Of the total fluid retention, fat and muscle each accommodated 25%, whereas the skin, which contributes only 7% to the total body weight, accounted for 37% and increased its volume by roughly one third. Concentrated albumin promoted fluid excretion in direct proportion to the achieved increment of the serum protein level and abolished the edema of fat, muscle and skin. Furosemide was virtually ineffective. The implications of these results for the 'adult respiratory distress syndrome' and disturbed wound healing are discussed and related to the concept of a critical threshold of the serum protein level.

Review: artifical ventilation with positive end-expiratory pressure (PEEP). Historical background, terminology and patho-physiology

CPPV (continuous positive pressure ventilation) is obviously superior to IPPV (intermittent positive pressure ventilation) for the treatment of patients with acute respiratory insufficiency (ARI) and results within a few minutes in a considerable increase in the oxygen transport. The principle is to add a positive end-expiratory plateau (PEEP) to IPPV, with a subsequent increase in FRC (functional residual capacity) resulting in re-opening in first and foremost the declive alveolae, which can then once again take part in the gas exchange and possibly re-commence the disrupted surfactant production. In this manner the ventilation/perfusion ratio in the diseases lungs is normalized and the intrapulmonary shunting of venous blood (Qs/Qt) will decrease. At the same time the dead space ventilation fraction (VD/VT) normalizes and the compliance of the lungs (CL) increases. The PEEP value, which results in a maximum oxygen transport, and the lowest dead space fraction, also appears to result in the greatest total static compliance (CT) and the greatest increase in mixed venous oxygen tension (PVO2); this value can be termed "optimal PEEP". The greater the FRC is, with an airway pressure = atmospheric pressure, the lower the PEEP value required in order to obtain maximum oxygen transport. If the optimal PEEP value is exceeded the oxygen transport will fall because of a falling Qt (cardiac output) due to a reduction in venous return. CT and PVO2 will fall and VD/VT will increase. Increasing hyperinflation of the alveolae will result in a rising danger of alveolar rupture. The critical use of CPPV treatment means that the lungs may be safeguarded against high oxygen percents. The mortality of newborn infants with RDS (respiratory distress syndrome) has fallen considerably after the general introduction of CPPV and CPAP (continuous positive airway pressures). The same appears to be the case with adults suffering from ARI (acute respiratory insufficiency).