Overview of Anesthesia for Patients With Burns
Every year, almost half a million people seek help from medical professionals due to burns. Anesthesiologists, the doctors who manage pain and monitor critical life functions during surgery, play a crucial role in taking care of patients with severe burns. They handle many important tasks, such as managing the patient’s breathing (airway management), supporting the heart and blood vessels (hemodynamic support), gaining access to the patient’s veins for fluid or medication delivery (intravascular access), helping to control the patient’s body temperature (thermoregulation), and assisting the lungs (pulmonary support).
The airway of a person with severe burns could become compromised or limited with traditional methods of delivering anesthesia, requiring special attention to make sure the patient is able to breathe properly. Burn patients present unique challenges, given the complex changes in the body after a burn. This poses difficulties in delivering fluids during surgery (intraoperative fluid resuscitation), choosing the right anesthesia drugs (induction drugs), and deciding the best approach to help the patient breathe (ventilation strategies).
In other words, the role of an anesthesiologist is crucial in providing the best care for burn patients during their treatment process.
Anatomy and Physiology of Anesthesia for Patients With Burns
Severe burns can cause significant harm to body tissues. These injuries can complicate several medical procedures such as maintaining clear air passages, monitoring vital signs, and establishing access to veins or arteries. Furthermore, it can trigger an inflammatory response, a natural defense mechanism of the body against harm. This response can create additional problems both at the site of the burn and elsewhere in the body. The body’s response to a major burn happens in two main phases.
The first phase, known as the “burn shock” or “ebb” phase, typically happens within the first 24 to 48 hours after a severe burn. A severe burn often includes second- and third-degree burns that cover 20% or more of the body’s total surface area. This phase is characterized by decreased blood flow to the organs and diminished heart function, caused by a loss in fluid volumes within the blood vessels. This can lead to fluid building up in the burned areas as well as other parts of the body, causing swelling (edema). The swelling can make it harder for doctors to see and access some regions, such as the throat, during medical procedures. The heart may struggle to pump blood efficiently during this phase due to a decrease in the volume of blood to pump, direct impact on the heart, and increase in the pressure within blood vessels. This results in reduced blood flow and can make it hard for the body to recover, despite aggressive fluid treatments from the doctors.
The second phase, known as the “hypermetabolic” or “flow” phase, typically develops 48 to 72 hours after the burn injury. In this phase, the body’s ability to consume oxygen and produce carbon dioxide increases. The heart function improves, leading to better blood flow to the organs. The increased heart function can also lead to other complications such as difficulty with weaning off a ventilator. Additionally, the body ramp ups energy consumption to cope with the injury. This can result in muscle wasting and high blood sugar levels, due to increased levels of stress hormones and resistance to insulin.
Once the burn injury covers 25% to 30% of the body’s surface, the body’s response creates effects that alter the normal functions of the body, leading to further complications. These can vary depending on the body system:
– Cardiovascular: The severity of the burn can lead to increased leakage of fluids from blood vessels, tightening of blood vessels, weakening of the heart muscles, and metabolic acidosis (a condition where the body produces too much acid). These can result in reduced blood flow and organ damage.
– Pulmonary: The burn can lead to fluid build-up in the lungs (pulmonary edema) and increased risk of spasms in the air passages due to excess mucus secretion. These can potentially lead to a severe lung condition known as Adult Respiratory Distress Syndrome.
– Integumentary (related to the skin): The burn injury can result in fluid losses through injured skin, and swelling, especially when burns cover more than 25% of the body. Severe burns around the chest, abdomen, or limbs can lead to a condition called “compartment syndrome” where pressure within a part of the body builds up to dangerous levels. The ability of the body to regulate temperature can also be affected.
– Immunologic: The person’s immune response may get weakened, making them more vulnerable to infections.
Why do People Need Anesthesia for Patients With Burns
If someone has suffered burns, they may have also experienced damage to their lungs due to inhaling hot gases or smoke, this is known as inhalation injury. Such injuries can worsen the overall condition of a burn patient, often requiring more fluid for treatment than those who didn’t inhale harmful substances. It can take several days for the symptoms to show, and initial chest scans may not reveal any issues until later complications develop.
There are three types of inhalation injuries:
1. Supraglottic: These injuries affect the upper part of the airway (the area above the voice box). This is mostly caused by breathing in heat or steam, which can cause swelling in the face, tongue, and other upper airway structures, making it hard to breathe or to use a ventilator. This kind of injury can be found by physical examination or by using a special camera (fiberoptic bronchoscopy) to take a good look at the throat and vocal cords. If one shows symptoms like a changing mental state, noisy breathing, hoarseness, or a swollen throat, they may need to be put on a ventilator early to avoid severe breathing problems. Swelling from this type of injury usually goes away in 3-6 days.
2. Subglottic: This type of injury affects the part of the airway below the voice box and happens when harmful chemicals or irritants are breathed in. This can cause swelling, bronchospasm (a sudden constriction of the muscles in the walls of the bronchioles), and peeling of the mucus membrane that lines the airway. The result is a build-up of bacteria and mucus in the airway, which can cause pneumonia. Inflammation may also interfere with the decrease in blood flow to the lungs that normally occurs when oxygen levels drop in certain parts of your lungs, which can lead to a lack of oxygen in one’s blood. If severe, it can lead to dangerous conditions like acute respiratory distress syndrome (ARDS) or a collapsed lung (pneumothorax).
3. Systemic: When harmful gases like carbon monoxide or cyanide are inhaled, they can affect the whole body, not just the airway. Carbon monoxide interferes with the ability of your blood to carry oxygen, while cyanide can prevent cells from using oxygen. This can be detected through blood tests. Symptoms of carbon monoxide poisoning include mental confusion, restlessness, nausea, dizziness, and headaches. In such cases, one must receive 100% oxygen as quickly as possible. If carbon monoxide levels remain high, additional measures like mechanical ventilation or hyperbaric oxygen therapy, which involves breathing pure oxygen in a pressurized room or tube, might be necessary.
Preparing for Anesthesia for Patients With Burns
When a patient with burns needs anesthesia urgently, it’s very important to check their airways properly. This is because swelling in the airway can sometimes make it harder for patients to breathe. If there is stiffness in the lower jaw from burn scars or swelling in the voice box, this can make it harder for doctors to view the airway with a tool called a laryngoscope. In cases where the airway has been burnt, the safest and most accepted way to ensure a clear airway is to use a fibreoptic intubation. This method involves numbing the area and using a tiny amount of general anesthetics.
If fiberoptic intubation is chosen, sedation can be induced with a drug called ketamine. Ketamine helps to keep the muscle tone in the throat steady, which makes intubation easier. Ketamine can also help ensure the patient maintains stable blood circulation and lower resistance in the airway, making it a good choice for patients with swollen airways. Some anesthetic drugs that weaken the airway muscles might make the airway more blocked and difficult during intubation.
Patients with severe burns might face difficulties when receiving intravenous treatment due to the burns on common sites like the neck, limbs, and groin. Swelling resulting from the burn or excess fluid from trying to replenish lost fluid in the body can make it hard to gain intravenous access. Delaying fluid replacement therapy for more than 2 hours after the burn occurs increases the risk of death, so getting access to the bloodstream quickly is crucial. If it’s too difficult to gain access through the usual means, injecting the treatment into the bone marrow can be extremely helpful. Injecting into the bone marrow is faster and more likely to be successful at the first attempt compared to the usual methods.
However, injections into the marrow can cause more pain during insertion and infusion than the usual methods. Despite it being faster and easier, it’s still not commonly used. To make sure the injection into the bone is successful, it’s important to understand the device properly, as incorrect placement is the common reason for failure. The top part of the tibia (the bone in the front of the leg) is the usual place to inject the needle, but the upper part of the upper arm bone (humerus) can be equally effective. The tibia is often chosen because it doesn’t get in the way of chest compressions during CPR.
Patients with severe burns lose their main barrier against heat loss. Hence, they are very likely to become hypothermic (extremely cold). Excessive sweat and water loss from the burn wounds create a direct path for heat loss. The brain mechanisms that regulate body temperature can become dysfunctional in severe burns. When the body temperature drops below a certain level, the body reacts by shivering, chattering teeth, constricting blood vessels, and generating heat without shivering. With severe burns, this temperature is lower.
When patients with severe burns are under general anesthesia, they are at a greater risk of hypothermia. This is because anesthesia moves heat from the core of the body to the surrounding areas and blocks the body’s ability to maintain its temperature. This can even make healthy patients prone to hypothermia due to the subsequent widening of the blood vessels. The best way to maintain body temperature is by warming the air, warming the fluids that are being given, and keeping the temperature of the operating room high. Monitoring body temperature using a probe placed in the lower part of the food pipe or rectum is essential for managing patients with severe burns.
How is Anesthesia for Patients With Burns performed
If you have burns that cover more than 15% of your total body surface area (TBSA), you will need fluid resuscitation – this is where extra fluids are pumped into your body. The fluids help tackle potential complications that often occur after a severe burn, like a decrease in your body’s blood volume due to fluid loss and damage to blood vessels. If fluid resuscitation isn’t done as soon as possible (within 2 hours of the initial severe burn), it can increase the risk of death. It’s also important to note that first-degree burns (more superficial burns) are not included when calculating TBSA for fluid resuscitation. Instead, only second- and third-degree burns (those that go deeper into the skin) are taken into account. For burns less severe than 15% TBSA, drinking oral fluids or getting fluids through an IV at a rate of 1.5 times normal should be enough to keep you hydrated.
For fluid resuscitation, the preferred type of fluid is lactated Ringer solution. This is because people with severe burns are prone to a condition called metabolic acidosis, where there’s too much acid in your body fluids. Metabolic acidosis can get worse if a large amount of normal saline solution (0.9%) is used for fluid resuscication due to decreased blood supply to the kidneys during burn shock. There are many ways to calculate the amount of fluid needed for fluid resuscitation, but healthcare providers must still focus on your overall clinical condition to avoid giving too much or too little fluid.
Some indicators to guide the amount of fluid given can include:
– Keeping your urine output between 0.5 to 0.1 mL per kg of your body weight per hour.
– A fractional excretion of sodium (the amount of filtered sodium that your body gets rid of through your urine) of less than 1% suggests not enough blood in the body.
– A blood urea nitrogen (BUN)-to-creatinine ratio (these are waste products that your body gets rid of through urine) of more than 20 suggests not enough blood in the body.
– An echocardiogram that checks your stroke volume (how much blood your left ventricle pumps out with each contraction) and ejection fraction (how much blood is pumped out of the left ventricle when it contracts).
– An arterial blood gas test showing a base deficit of less than 5 (which might point to poor blood circulation) unless you have carbon monoxide poisoning.
Overdoing fluid resuscitation can cause harmful issues like tissue and lung swelling, which might make the patient’s condition worse, require breathing assistance, or lead to a lung infection. The swelling can also increase narrowing of your air passage, which may require intubation (insertion of a tube into the throat to aid breathing). This issue, known as “fluid creep,” is often due to the calculation of how much fluid resuscitation is needed in the first 24 hours after an initial burn.
Healthcare providers need to remember that any IV medications a patient may be getting, like antibiotics, painkillers, and sedatives, should also be included when figuring out the total fluid intake. A crucial objective finding to cut back on fluid replacement is urine output, which can lead to fluid creep when not taken into account. The role of colloids (solutions with tiny particles) is currently not clear but might be considered as additional therapy to prevent high blood volume.
The commonly used method to estimate the amount of fluid resuscitation needed for a patient is the Parkland formula. The Parkland formula is a guide to the amount of fluid to be given in the first 24 hours, with half of the calculated amount advised to be given in the first 8 hours.
Parkland Formula: 4 mL x your weight in kg x % of TBSA burned
For example: If a 75 kg male has a burn covering 30% TBSA:
– Calculate the total amount of lactated Ringer solution to give in the first 24 hours
4 mL x 75 kg x 30 = 9,000 mL for the first 24 hours
– Calculate the amount of fluid to give in the first 8 hours
Half of the total volume should be given in the first 8 hours
9,000 mL /2 = 4,500 mL of lactated Ringer solution in the first 8 hours
– Give the remaining amount of fluid in the last 16 hours
* 4,500 mL in the last 16 hours
The Wallace Rule of Nines is a standard method used to estimate the TBSA of the burn. The rule is quite simple and practical to use in clinical scenarios. For more minor burns, healthcare providers may use the Rule of Palms, that considers the size of the patient’s palm to represent about 1% of TBSA.
However, it can be challenging to figure out actual TBSA due to variations in body surface area resulting from differences in gender, age, and body mass index. Patients with larger body mass index often have overestimated calculation of their burn TBSA. In the future, 3D body scanning might be used to more accurately determine the TBSA of burns. Accurately figuring out the TBSA is important for deciding whether a patient needs to be referred to appropriate burn centers and to help set fluid resuscitation goals. It’s crucial that healthcare professionals communicate effectively when taking care of a severely burned patient to better understand their fluid needs.
A major concern with burn patients is the fact that burns can result in an increase in acetylcholine receptors (parts of nerve cells that respond to acetylcholine, a chemical messenger) in a person’s body. This increase can lead to high levels of potassium in the blood, a condition known as hyperkalemia, when a common muscle relaxant called succinylcholine is used. This is dangerous because severe hyperkalemia can cause heart problems and can be life threatening. However, it’s important to know this increase in acetylcholine receptors takes 24 to 48 hours after the initial burn to happen and thus, doesn’t cause significant hyperkalemia immediately.
Resistance to non-depolarizing neuromuscular blockade (a type of muscle relaxant that blocks nerve impulses from reaching the muscle) can happen a lot quicker than sensitivity to succinylcholine (within 24-48 hours). So, a burn patient might need higher doses of a non-depolarizing neuromuscular blockade than expected. By using a higher dose, healthcare professionals can partially overcome resistance to this neuromuscular blockade with rocuronium, a muscle relaxant medication. With a significant burn injury, rocuronium can provide reasonably good conditions for inserting a tube into the throat with a 1.2 mg/kg dose.
Possible Complications of Anesthesia for Patients With Burns
Severe burn injuries can weaken your body’s defense system because they raise the level of inflammation markers in your body, making you more susceptible to infections. Soon after a burn, bacteria like Staphylococcus aureus and Staphylococcus epidermis, which are commonly found on the skin, can start to gather in the burn wound. After a few days, other bacteria, like Pseudomonas aeruginosa and Escherichia coli which are usually found in the gut, can also start to appear in the burn wound.
Even though these bacteria might be present, taking antibiotics to fight a body-wide infection is not always necessary right around the time of your burn surgery. What’s more important in this period is to keep the wound very clean. This can be done by carefully washing it with soap, water, a solution called ‘normal saline’, or a disinfectant called ‘chlorhexidine’. Instead of body-wide antibiotics, a type of antibiotic cream or ointment can be applied directly on the burn area before and after your burn surgery in the early stages of the healing process.
Also, it’s important for the burn surgeon and the anesthesiologist, the doctor who’s responsible for your pain control and sedation during your surgery, to communicate well. They can make sure that antibiotics are used effectively and only when necessary, to avoid overuse in burn patients.
What Else Should I Know About Anesthesia for Patients With Burns?
Providing anesthesia care to patients with burns is a complex task that demands special skills and knowledge. The burns cause changes in the body’s normal functioning, which makes the anesthesia procedure more complicated. One of the biggest challenges is safely putting a breathing tube into the patient’s windpipe, especially in severe cases of burns around the head and neck area. This is done to ensure the patient can breathe easily during surgery. To manage this, a careful balance is created where the patient is relaxed and comfortable but awake enough to breathe on their own during the procedure.
Another aspect that requires understanding is how the circulation of body fluids changes after a burn. This knowledge helps in correctly giving the necessary fluids to the patient during surgery before moving them to intense care. Patients with burns also have trouble regulating body temperature, and this can affect healing, blood clotting, and also cause shaking after surgery. To avoid these complications, doctors can take appropriate measures during surgery.
Anesthesiologists, who are doctors specializing in pain relief during surgeries, play a vital role in caring for burn patients during and after surgery. By understanding the specific needs of these patients and how to best address them, the risks associated with surgery can be minimized, promoting healthier and speedy recovery.
