a Comparison Between the Effects of Crystalloids and Colloids on Lung Ultrasound

Hypertensive disorders are the most common complications of pregnancy. They occur in 6-8% of pregnancies and account for approximately 15% of maternal deaths in the United States Pre-eclampsia is a pregnancy-specific syndrome of unknown etiology that is defined as systolic blood pressure (SBP) > 140 mmHg and/or diastolic blood pressure (DBP) > 90 mmHg presenting after 20 weeks of gestation with significant proteinuria (1) Because patients with pre-eclampsia may have significant intravascular volume deficit and reduced uteroplacental perfusion, it is prudent to administer fluids before any anesthetic interventions. (2) however it may increase their risk of developing pulmonary oedema (3) Colloids and crystalloids are two types of fluids that are used for fluid replacement, as volume expanders. Crystalloids are low-cost salt solutions (e.g. saline) with small molecules, which can move around easily when injected into the body. Colloids can be man-made (e.g. starches, dextrans, or gelatins), or naturally occurring (e.g. albumin or fresh frozen plasma (FFP)), and have bigger molecules, so stay in the blood for longer before passing to other parts of the body. (4) Women with pre-eclampsia lose protein through renal excretion and may also extravasate protein into the interstitial tissues, oncotic pressure falls because of this and the tendency to lose fluid from the intravascular space is partially determined by this mechanism. Filling the vascular space with fluid will lead to increasing peripheral oedema. Colloids will remain in the vascular compartment for longer periods than crystalloids although the loss of colloid into the interstitial tissues will also contribute to the development of oedema. Changes in capillary permeability will have an independent influence. (5) Ultrasound is now widely used in many medical specialties, being safe tool for both the parturient and the baby, ultrasound is basically used by the obstetricians in pregnant females for diagnosis of fetal presentation, placental position, fetal organs, amount of liquor and in some interventions amniocentesis. In the last 15 years, a new imaging application of sonography has emerged in the clinical arena: lung ultrasound (LUS), it can give valuable data in diagnosing and management of pneumothorax, pleural effusion, lung consolidation and pulmonary congestion. (6) The electrical cardiometry which can be used to measure and calculate hemodynamic parameters such as cardiac output, stroke volume, systemic vascular resistance, ICON (index of contractility), and thoracic fluid content. (7) In general, there is no epidemiological evidence to support the choice of colloidal solutions over crystalloids and it is not clear that colloidal solutions would be more effective and less likely to cause harm than crystalloids in preeclamptic patients. A meta-analysis was done to investigate crystalloid versus colloid resuscitation in critically ill patients however pregnant women and neonates were excluded. (8) Consequently, there is inadequate evidence supporting one view or another in the management of pre-eclampsia.