Theoretical Evaluation of a Simple Cooling Pad Inducing Hypothermia in the Spinal Cord Following Traumatic Injury

Abstract

Although significant damage is caused by the mechanics of the traumatic spinal cord injury (SCI), secondary injury that follows is often times even more dangerous. It occurs within the first 12–24 hours following the injury and can last up to 5–10 days, depending on the severity of the injury [1]. Secondary injury causes physiological disturbances that disrupt the body’s homeostasis like initiating a cellular inflammatory response at the injury site and increasing the release of free radicals. An overabundance of free radicals contributes to tissue ischemia, cerebral edema, and disruption of the spine-blood barrier. The use of hypothermia (<35°C) as a therapeutic agent has been shown effective in providing neuroprotection from secondary injury [2]. Research has shown the benefits of hypothermia include decreasing oxygen consumption, free radical generation, neurotransmitter release, inflammation, and metabolic demands [3–5]. Even a temperature decrease of 1–2°C can be beneficial at the cellular level [4,6]. However, these studies use techniques that can be invasive. This research evaluates the effectiveness of using a non-invasive cooling pad on the torso to reduce the spinal cord temperature by at least 2°C.

Brain hypothermia induced by cold spinal fluid using a torso cooling pad: theoretical analyses

“…During normal and ischemic conditions, the local blood perfusion rate in each tissue structure is assumed to be proportional to the local metabolic heat generation rate. From the literature [23,24,[29][30][31], the average amount of CSF in the body is 137.5 ml and 37% (50.88 ml) of that amount fills the brain cavity when the body is in a horizontal position. Based on previous theoretical results [23,31], the volume of cold spinal fluid replacing the CSF in the brain cavity during a pulsatile cycle with a 1-s period is calculated as 4.28 ml.…”

“…From the literature [23,24,[29][30][31], the average amount of CSF in the body is 137.5 ml and 37% (50.88 ml) of that amount fills the brain cavity when the body is in a horizontal position. Based on previous theoretical results [23,31], the volume of cold spinal fluid replacing the CSF in the brain cavity during a pulsatile cycle with a 1-s period is calculated as 4.28 ml. From this, the percentage of warm CSF in the brain that is replaced by cold spinal fluid per second, p sp , in Eq.…”

“…In this study, the CSF compartment is modeled as a lumped system where the temperature is a function of time, t, only. The fluid from the spinal region enters the brain cavity during arterial diastole and exits the brain region during arterial systole [31]. Therefore, this study assumes that the total mass of the CSF in the head region is relatively unchanged.…”

“…In our previous theoretical simulation [31], the temperature reduction of the fluid surrounding the spinal cord is induced by the use of a cooling pad placed along the back of the torso. The data from that study are used in this current theoretical model to calculate the temperature of the CSF surrounding the brain hemisphere during the cooling process.…”

“…Our previous theoretical study [31], which simulates the temperature distribution in the spinal cord and its surrounding structures, illustrates the feasibility of reducing the average spinal cord temperature by approximately 2.7°C with the use of a simple cooling pad placed along the back of the human torso. Additionally, this proposed treatment reduces the average global temperature of the spinal fluid surrounding the spinal cord by approximately 3.5°C within 1800 s (30 min).…”