by Anushri Bhattacharya
Traumatic brain injury (TBI ) is one of the most common public health problems, around 10% of global burden of disease, which is usually caused by an outside force, experienced during an accident or severe sports injury. Usually during a TBI which is commonly accompanied by haemorrhagic shock (HS), the neurovascular unit of the brain which is known as the ‘blood-brain barrier’ (BBB) gets impaired which in turn causes the water, protein serums and osmoles (CO2, O2 etc) distribution in the brain to get disrupted which may further cause vasogenic cerebral edema and increased intracranial pressure (ICP). The BBB prevents substances from the blood from entering the brain. The BBB disruption may cause clear fluids draining out from the patient's nose and ears which is one of the clear symptoms of severe TBI, this may be due to the fluid maldistribution in the brain which becomes a critical issue in TBI. In many TBI cases, albumin fluid is seen to leak through capillary walls which can be dangerous and cause uncontrolled fluid distribution. As treatment, intravenous fluid therapy is used to manage the critical fluid condition of the patient and manage adequate tissue perfusion and oxygenation.
In fluid resuscitation or fluid therapy (FT) , fluids such as colloids and crystalloids are used to enhance the working of the circulatory system for efficient oxygenation of organs. Fluid resuscitation is used to maintain normal homeostasis and to treat sequestration of fluid which is the loss of fluid/blood lost into the spaces of our body. Fluid resuscitation after TBI runs on the fact that hypertonic solutions may restore cerebral perfusion (blood flow at the capillary level). The modern Intravenous Fluid Therapy traces back its origin from the 1830’s when it was widely used to treat cholera and manage the fluid levels in the patients. Previous studies have suggested that various hypertonic concentrations such as 1.6% - 23.4% saline show a reduction in intracranial pressure and better cerebral perfusion , thus aiding to treat the consequences of traumatic brain injury . So how exactly does the FT aid in TBI ? The immediate rapid infusion of intravenous fluids (hypotonic crystalloids in the case of cerebral injury) helps to restore the fluid (blood) pressure and fluid volume.
In fluid resuscitation, typically isotonic and hypertonic crystalloid solutions are used. Normal Saline (NS) or Lactated Ringer’s (LR) are the primary fluids in FT. These fluids can further be grouped as protein colloids (Albumin and gelatin) and non-protein colloids (Starches and Dextrans). According to the ‘Saline Versus Albumin Fluid Evaluation’ study , infusion of sole crystalloid in patients suffering from TBI is more beneficial than infusion of colloidal solutions which may be harmful instead. Mannitol, which is a crystalloid fluid that is hypertonic, is usually used in fluid resuscitation in patients after they have suffered from traumatic brain injury. Large amounts of hypotonic fluids reduce plasma osmolality (electrolyte-water balance) , thus increasing cerebral water content hence making less use as a resuscitative fluid. For this reason, hypo-osmolar or hypotonic fluids are usually avoided in neurosurgeries and instead hypertonic crystalloids are used.
Fluid resuscitation is a less invasive method than surgery to treat traumatic brain injury which is commonly an emergency case and the primary objective of fluid resuscitation is to avoid formation of cerebral edema due to the traumatic brain injury. Advanced endpoint monitoring may guide clinicians in when to 'turn off' aggressive fluid therapy and therefore avoid the problems of over-resuscitation.
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