Overview of Parkland Formula
Burns that cover a large portion of the body can cause significant local damage, tissue injury, and trigger a widespread inflammation that affects several organ systems. Patients with severe burns are considered trauma patients and therefore, their treatment should always start with focusing on the ABCs: airway (making sure the patient can breathe), breathing (checking the breathing rate and quality), and circulation (ensuring the blood is circulating properly). Once these initial assessments are done, the following step is to start a fluid replacement therapy promptly.
The principles of fluid replacement after a burn have been improved and refined over the years, thanks to decades of research. Over time, many formulas have been developed that help calculate the amount of fluid a patient needs based on factors like body weight and the severity of the burn.
For example, in the 1930s, Frank Pell Underhill discovered that the fluid within a blister from a burn was similar to blood plasma. This led to fluid replacement strategies based on patient weight and either blood protein levels or the concentration of red blood cells. During the 1940s, Cope and Moore discovered that the amount of fluid a patient needs depends on the size of the burn.
Initially, doctors used plasma as the main fluid for replacement. They used a formula called the Evans formula, which suggests giving 2 milliliters of fluid per patient weight in kilograms per percentage of total body surface area burned, plus 2 liters of maintenance fluids. Half of these fluids was plasma and the other half was a normal saline solution. Over time, guidelines shifted towards using less plasma and more of a salt solution called Lactated Ringer’s solution.
Today, the Parkland formula is used most often for fluid replacement after a burn. However, it’s still a topic of conversation in the medical community because even though the Parkland formula is well-accepted, there’s ongoing research to determine its accurateness and appropriateness in various cases. This formula suggests giving 4 milliliters of Lactated Ringer’s solution per patient weight in kilograms per percentage of total body surface area burned.
Anatomy and Physiology of Parkland Formula
Severe burn injuries can cause your body to go into a state of high alert, leading to a “hypermetabolic” response. This basically means that your body speeds up its normal processes, activating your immune system and releasing immune system molecules and chemicals that affect your blood vessels. These chemicals open up your small blood vessels, letting fluids, electrolytes (like sodium, potassium, and calcium, which help your cells do their jobs), and important proteins leak out into the space between your cells.
This leaking makes fluid start shifting in your body, pulling it out of your blood vessels and into your tissues, causing them to swell up. This can happen very quickly, starting within minutes of the injury and happening very fast over the first 24 hours after the injury. The biggest fluid shifts, blood vessel fluid loss, and swelling usually happen between about 8 to 12 hours after the injury.
Huge fluid losses throughout your body, paired with a decrease in how much blood your heart is pumping out and an increase in resistance within your blood vessels, can limit blood flow to your tissues and cause further injury. This state, known as “burn shock,” is a mix of different types of shock related to blood and fluid distribution, fluid loss, and heart function, and requires speedy treatment with fluids. Giving fluids to severe burn victims helps keep blood flowing to their tissues and prevents further injury to vital organs during the early phases of burn shock. Prompt and adequate fluid treatment has consistently improved the health and survival of severe burn victims. Because of these improvements, many medical protocols have been developed to help doctors figure out initial fluid needs following severe burn injuries.
Why do People Need Parkland Formula
The Parkland formula is a vital method that doctors use to figure out how much fluid to give patients who have serious burns. This calculation is necessary for people who have deep, severe burns that cover more than 20% of their total body surface area (TBSA) in adults, and more than 10% in children. Basically, TBSA refers to the percentage of your body that’s been burned.
This formula was initially tested on large animals before it was used for people. The original version of the formula suggested giving 3.8 mL of fluid per kilogram of the patient’s body weight for each percent of TBSA burned. Only about 12% of patients needed extra fluids. However, eventually, the formula was simplified to 4 mL, and the use of a substance called colloid (a type of fluid used in medicine) was suggested for use only 24 to 48 hours after initial fluid replacement.
When a Person Should Avoid Parkland Formula
The Parkland formula is a commonly used process for treating severe burns by giving the right amount of fluids to the body. Although there are no specific conditions where this method should not be used, it’s especially important to closely watch patients who have other health problems like heart failure or serious kidney disease, to make sure they’re not getting too much or too little fluid. Patients with minor burns who are still able to eat normally, usually don’t need to receive this special fluid treatment.
Preparing for Parkland Formula
When somebody suffers a trauma or is critically unwell, one of the first things doctors do is to install two large tubes–like small straws–into the veins, usually in unburned skin. These tubes are called “peripheral intravenous catheters” and they’re used to quickly and softly give patients a lot of liquids needed during their time in the emergency room.
Sometimes, if veins can’t easily be reached because of severe injuries or burns, doctors might put in a ‘central venous catheter’ (a tube inserted into a large vein near the heart) or an ‘interosseous line’ (a needle placed into the bone marrow to give fluids).
When a patient is suffering from burns, it’s really important to remember that they may have other additional injuries too. Low blood pressure (hypotension) can be caused by many different things and often doesn’t show up until late into ‘burn shock’ (a severe reaction your body can have to major burns). If a burn patient arranges in the ER with low blood pressure, doctors will investigate other potential causes of this, like bleeding inside the chest (hemothorax), pressure on the heart (cardiac tamponade), shock caused by a serious injury to the nervous system (neurogenic shock), or unseen bleeding in the belly or pelvis.
How is Parkland Formula performed
When treating a burn patient, the first step is to understand how serious the injury is. This is done by figuring out the Total Body Surface Area (TBSA) that the burn covers – but we only count the areas with partial-thickness burns (these are burns that go through the second layer of skin) and full-thickness burns (the most severe type of burn, that goes through all layers of skin).
A common method doctors use to estimate TBSA is the “rule of nines,” which splits the body into sections that represent 9% or 18% of the total body. For children with burns, doctors use a different method called the Lund and Browder Chart that takes into account how a child’s body shape changes as they age. If the burn only covers a small area, doctors might use the “rule of palms,” which considers the size of the patient’s palm – with fingers stretched out – as 1% of their TBSA.
After the doctors figured out the TBSA, they weigh the patient and use a formula known as the Parkland formula. This gives them the total amount of fluids that the patient needs in the first 24 hours after the burn happened. Adults and children need different amounts of fluid per kilogram of body weight. Half of these fluids should be given within the first 8 hours after the burn, and the rest is given over the following 16 hours. Extra fluids are usually given to children because they are more at risk of low blood sugar from the burn due to their smaller energy stores.
Doctors typically use a fluid called Lactated Ringer solution for burn patients because it helps replace lost fluids and salts effectively and is cheap and readily available. They usually avoid using another solution called normal saline in large amounts, as it can lead to an unhealthy acid buildup in the blood. Any fluids that the patient received before getting to the hospital will be taken into account when deciding how much more fluid to give in the first 8 hours.
Doctors monitor the patient’s urine output to ensure the body is receiving enough fluid. They will insert a urinary catheter (a tube) to provide an accurate measurement. If the urine production is too low, it means the patient needs more fluids. Other signs, such as heart rate, blood pressure, speed of blood returning to the skin after being pushed away (capillary refill time), and how alert the patient is, are also used to determine if enough blood is being distributed to the body’s organs.
Even after the initial 24 hours, doctors must ensure the burn patient stays well-hydrated throughout their recovery. The type of fluid given may be changed to Dextrose 5% in half Normal Saline (D5½NS) and should be administered at a maintenance level. Some guidelines suggest adding colloid-containing fluids, which contain larger molecules to help keep more fluid in the bloodstream, can reduce overall fluid requirements during the first day after a burn.
Possible Complications of Parkland Formula
Formulas used for fluid resuscitation in burn patients are meant to act as a guide to give the right amount of fluids. It’s important to get the balance right because giving too little can worsen the burn, and increase the risk of multiple organ failures, which can be fatal. On the other hand, giving too much fluid can also be harmful, leading to other serious conditions such as compartment syndrome (pressure buildup from internal bleeding or swelling of tissues), difficulty in breathing (acute respiratory distress syndrome), and malfunction of multiple organs.
Recently there’s been some discussion concerning the efficacy of the Parkland formula, a commonly used method for calculating fluid requirements. A study conducted in 2021 found that patients who received fluid according to this formula had higher death rates in the initial week. Those who received lesser fluid than calculated had a higher death rate and an increased risk of acute kidney injury (sudden damage to your kidneys). These patients were also more likely to be obese. It was found that patients who got more fluid in the first day after being burned also received more fluid in the next day and had higher death rates.
Other studies found that the actual amount of fluid given to patients often exceeded the amount calculated by the Parkland formula, even when patients were adequately hydrated. Comparing the Parkland formula with another formula, the modified Brooke formula which calculates a lower amount of fluid, it was found that patients under the Parkland formula had fewer ventilator days (days spent on breathing machines). A future study in 2023 found more successful fluid resuscitation using the Parkland formula also.
One other factor to consider is that the accuracy of fluid calculations depends on the assessment of burn size and depth. A wrong estimation could result in not giving enough fluids. Moreover, patients who come to the hospital by car may be at risk of getting lesser fluid than required compared to those transported immediately by air.
What Else Should I Know About Parkland Formula?
Managing fluids in patients with burns or injuries can be a tough job. When a patient suffers from a burn or injury, their body needs more fluids to help them recover. However, figuring out the correct amount of fluids is not easy; it depends on many things that are unique to each patient. Because of this, doctors have guidelines they can start with but they must adjust according to each patient’s needs.
No guide is perfect, especially when it comes to more complex cases like electrical burns, chemical burns, or patients with multiple injuries; these people often need even more fluids.
Despite its limitations, one commonly used guide is the Parkland formula. Although this guide can’t account for every possible situation, it’s generally a good starting point for making sure a patient gets the fluids they need following a burn or other trauma.
