Volume Shock (HB)

If we have a history of trauma for this event, and that mechanism is significant, you should consider internal and external bleeding. But the most common mechanism for volume shock is dehydration, which can occur from sweating, vomiting, or diarrhea.

As a person loses volume, several vital signs change. The skin is one of the first indicators. It will start becoming cool and pale as fluid is shifted from the periphery to the core. Next to change is the mental status–the patient may exhibit signs of anxiety or lethargy. The pulse and respiratory rate also start increasing.

If you measured the blood pressure, it would remain relatively normal for that patient.

Over the long term (especially with dehydration), you will see a reduction in urine output–in fact, this might be a useful sign when you are assessing your patient when combined with the last intake of water/fluids.

All of the above will continue as long as the volume is decreasing. The blood pressure is tightly coupled with mental status as the body is working to keep the brain perfused as normally as possible. The body is compensating for the loss of fluid and the associated reduction in perfusion pressure by pulling fluid from other parts of the body and then circulating it at a higher rate. There will be very few changes to the patient’s mental status since the brain is being perfused close to normal.

Once that process begins to fail, the patient is now decompensating. At this point, you will start noticing significant changes to the mental status.

You have to stop the source of volume loss and restore the volume. If the source is an external bleed, you should correct that using one of the methods we discussed in MARCH–tourniquet, wound packing, pressure bandage, etc. If the source of the loss is internal bleeding, there is not much you can do in the field–this patient needs surgical intervention, and they need it rapidly. If the volume loss is via dehydration, you must identify the reason. If they are sweating, cool them down. If they are vomiting, Benadryl can help as an antiemetic. Imodium can be used for diarrhea. For the last two, the underlying reason will eventually need to be addressed (be it from a toxin or whatever)–the immediate threat is from volume shock, so we must resolve that.

The best way to restore volume, assuming you have corrected the reason for the loss, is via the oral route. The body is designed to utilize water and nutrients via the digestive tract efficiently. If the patient can tolerate it, they should drink water and consume electrolytes. You can also rectally rehydrate the patient by introducing fluid into the colon.

As with all patients, you should take particular care to manage hypothermia in these patients.