Which of the following factors directly affects stroke volume?

Choice A Reason:
Urine output is one of the most reliable indicators of adequate fluid resuscitation in burn patients. The goal is to maintain a urine output of 0.5 to 1 mL/kg/hour in adults³. This parameter is crucial because it directly reflects renal perfusion and, by extension, overall circulatory volume status. When fluid resuscitation is adequate, the kidneys receive enough blood flow to produce urine at this rate, indicating that the body's tissues are being adequately perfused. Monitoring urine output is a non-invasive and straightforward method, making it a preferred choice in clinical settings.

Choice B Reason:
Heart rate can be an indicator of fluid status, but it is less reliable than urine output. Tachycardia (an increased heart rate) can occur due to pain, anxiety, or other stressors, not just fluid deficit. While a decreasing heart rate might suggest improving fluid status, it is not a definitive indicator on its own. Other factors must be considered in conjunction with heart rate to assess fluid resuscitation adequacy.

Choice C Reason:
Blood pressure is another parameter used to assess fluid status, but it can be influenced by many factors, including the patient's baseline blood pressure, medications, and the presence of other medical conditions. While maintaining adequate blood pressure is important, it is not as sensitive or specific as urine output for assessing fluid resuscitation in burn patients. Blood pressure can remain within normal ranges even when fluid resuscitation is inadequate, especially in the early stages.

Choice D Reason:
Mental status can be affected by fluid status, but it is a late indicator of inadequate perfusion. Changes in mental status, such as confusion or decreased level of consciousness, can occur when there is significant hypoperfusion and shock. By the time mental status changes are observed, the patient may already be in a critical state. Therefore, it is not a primary indicator for assessing fluid resuscitation adequacy.

Choice E Reason:
Capillary refill time is a quick and simple test to assess peripheral perfusion. However, it is not as reliable as urine output for evaluating overall fluid status. Capillary refill can be affected by ambient temperature, lighting conditions, and the examiner's technique. While a prolonged capillary refill time can indicate poor perfusion, it is not as specific or sensitive as urine output for assessing fluid resuscitation adequacy.

Step-by-Step Calculation:

Step 1: Convert 2 gm to mg.

2 gm × 1000 = 2000 mg

Step 2: Determine the concentration of Lidocaine in mg/mL.

2000 mg ÷ 500 mL = 4 mg/mL

Step 3: Calculate the infusion rate in mL/min.

2 mg/min ÷ 4 mg/mL = 0.5 mL/min

Step 4: Convert the infusion rate to mL/hr.

0.5 mL/min × 60 min/hr = 30 mL/hr

Result: The Lidocaine drip should be infused at 30 mL/hr.