Overview of Shock Resuscitation
Simply put, ‘shock’ refers to a situation where there isn’t enough oxygen reaching all parts of the body. This is caused by a variety of factors, including a lower amount of blood circulating in the body, a decline in heart function, a reduction in the body’s vascular resistance (which manages our blood flow), or other situations that hinder effective blood circulation to crucial organs. Shock is often partnered with a sudden decline in blood pressure, making it difficult to get sufficient blood flow to these key organs. When treating someone experiencing shock, it’s essential to consider the root cause, as it can significantly impact how the patient is successfully revived.
The most common form of shock seen in emergency treatments is ‘hemorrhagic shock’, which is directly linked to significant blood loss. Another general term for this situation is ‘hypovolemic shock’. Another type of shock, termed cardiogenic shock, occurs when the heart’s output is so low that it can’t ensure proper blood flow to the rest of the body. Neurogenic and septic shocks are associated with a decrease in the body’s ability to regulate blood flow due to lowered pressure. Adrenal insufficiency shock is a category that factors in the efficiency of the heart output, blood volume, and the body’s resistance to blood flow.
Shock treatment often involves the transfusion of blood products. In the United States alone, nearly 21 million blood products are transfused annually, with about 36,000 red blood cells, 7,000 platelets, and 10,000 fresh frozen plasma units given every day. However, the majority of these transfusions are not for treating shock but are done in preparation for surgeries (55%) or for patients with an ongoing type of anemia (30%). Emergency blood product transfusions or trauma-related transfusions account for only 15% of all transfusions. Regardless of its relative rarity, understanding the current guidelines for treating hemorrhagic shock through fluid revival is cardinal.
Anatomy and Physiology of Shock Resuscitation
Shock is a severe medical emergency which can cause changes in the body’s physiological makeup. These changes are monitored using parameters like central venous pressure (CVP, a measure of the blood pressure in the heart), pulmonary capillary wedge pressure (PCWP, a measure of the pressure in the heart’s left side), cardiac output (CO, the amount of blood the heart pumps), systemic vascular resistance (SVR, a measure of blood pressure resistance), heart rate (HR), blood pressure (BP), and oxygen saturation (O2, how much oxygen blood carries).
These measurements help doctors understand the severity of the shock and identify the reasons behind it. For example, in hemorrhagic shock, where there is major blood loss, the CVP and PCWP usually drop due to lowered blood volume. At the same time, body tries to compensate by increasing SVR and reducing CO.
In septic shock, a result of a severe infection, the CVP and PCWP decrease as well, but unlike hemorrhagic shock, SVR also decreases because of widespread blood vessel relaxation. However, CO increases as the heart works harder to make up for these changes.
In cardiogenic shock, when the heart can’t pump enough blood, the CVP and PCWP go up due to the decrease in heart function while the CO decreases. SVR increases to maintain the pressure necessary to supply blood to the body.
In cases of neurogenic shock, caused by severe stress or injury to the nervous system, all measurements – CVP, PCWP, CO, SVR – are expected to drop. This occurs because the body fails to maintain normal blood vessel constriction or compensate by increasing the heart’s output. Adrenal insufficiency, a condition where adrenal glands don’t produce enough hormones, presents similar trends as neurogenic shock.
Why do People Need Shock Resuscitation
Hemorrhagic shock is a major and potentially life-threatening condition caused by severe blood loss, and this condition is divided into four “classes” or levels of severity, depending on the amount of blood that’s been lost. The class of hemorrhagic shock also guides the best treatment approach.
Class 1 hemorrhagic shock is when a person loses up to 750mL of blood, which is about 15% of their total blood volume. At this point, the person’s heart will typically beat under 100 times per minute (a measure referred to as heart rate). They may have a normal or slightly elevated blood pressure due to anxiety and their breathing rate will remain steady at 14-20 breaths per minute. They’ll also still be capable of producing urine normally, at a rate greater than 30 mL per hour.
Class 2 hemorrhagic shock happens when a person loses between 750 mL to 1500 mL of blood (15% to 30% of their total blood volume). Now, the person might start to look paler, sweat more and their heart may beat slightly faster – between 100 to 120 times a minute. They might also breathe faster than normal (20-30 breaths per minute) and produce slightly less urine (20-30 mL per hour). At this point, urine production is an important indicator of how much fluid is in their body. You should also know that the only reliable early sign of this type of shock might be a slight drop in the difference between the systolic and diastolic blood pressure (referred to as pulse pressure).
Class 3 hemorrhagic shock is when a person has lost between 1500-2000 mL of blood, which is 30-40% of their total blood volume. They’ll be visibly distressed, confused, their heart will beat between 120-140 times a minute, and they will breathe rapidly (30-40 breaths/minute). Their blood pressure will decrease, which will lead to a reduction in urine production (5-15 mL/hr).
Class 4 hemorrhagic shock, the most severe kind, is when there’s a loss of more than 2000 mL of blood (over 40% of total blood volume). The person’s heart rate will be over 140 beats per minute and their pulse might be hard to feel or disappear completely (known as a thready pulse). They will breathe more than 35 times per minute and their blood pressure will drop severely. Urine production will almost stop and they might be extremely tired and have a hard time keeping clear thoughts.
Equipment used for Shock Resuscitation
The blood components given during a transfusion are usually packed red blood cells, fresh frozen plasma, platelets, and something called cryoprecipitate. Here’s what each does and why it’s used:
Packed red blood cells (pRBCs) come in servings of about 350cc and are more concentrated than whole blood. They’re ‘packed’ because most of the plasma (the liquid part of blood) and platelets (small cells that help stop bleeding) are removed, leaving just the red blood cells. These cells are preserved in a special saline solution to extend their usable time and can be stored for up to 35 days at fridge temperature. These cells help to increase a patient’s hemoglobin levels. Hemoglobin is a protein in red blood cells that carries oxygen. The blood groups of both the donor and the recipient have to match to ensure compatibility.
Fresh frozen plasma (FFP) is provided in servings of 200-250cc. It contains all the clotting factors, which are proteins in our blood that work together to stop bleeding, but no red blood cells or platelets. To be effective, it needs to be given according to the patient’s weight. It helps increase clotting factor levels in the body by 20-30%. The plasma is frozen and stored at very low temperature, increasing the shelf life to up to two years. It should be used immediately after thawing as its effectiveness decreases over five days. FFP is used for specific blood clotting disorders or shortages of specific clotting factors.
Platelets are often given in concentrated “6 packs”. One “6-pack” is generally 250cc, is kept in a small amount of plasma, and can only stay fresh for around five days at room temperature. They can’t be frozen, as this significantly reduces their shelf life. Platelets help to increase the patient’s platelet count and thus help the blood clot. Note that some patients can develop antibodies against the platelets after multiple transfusions, which can make future transfusions less effective.
Cryoprecipitate, often known as Cryo, is another blood product often used. It’s collected by spinning plasma and catching the particles that form from the cooling off, which contain specific blood components. These can be stored for up to two years at cold temperatures and are given in small quantities. Like FFP, it helps with clotting.
How is Shock Resuscitation performed
If someone is experiencing severe blood loss, the first steps a doctor will take include setting up a rapid way to give fluids. This is usually done by inserting two large intravenous lines (IVs), which carry fluids directly into the blood. The IV lines are often put in both arms, and they are wide (about 16-18 gauge) so fluids can be given quickly. If necessary, a tube may be inserted into a larger vein in the chest or neck; this is called a central venous catheter (CVC).
The reason large IVs in the arms work so well is due to a scientific principle called Poiseuille’s law. In simple terms, this law states that fluids can move faster through a wider, shorter tube. Since IV lines in the arm are shorter than a CVC, two of them can give fluids faster than one CVC in the chest or neck.
When helping someone with severe blood loss, the first step is to give a large amount of fluids through the IVs. This is followed by giving blood and other blood products. The fluid given at the start is usually a salt solution, which is like the body’s natural fluids. The amount of fluids given depends on the patient’s weight.
The doctor will then monitor the response to the fluids. Some patients may only require fluids at the start. Others, particularly those with major blood loss, will need blood products quickly. The goal is to maintain enough blood pressure for the body’s vital functions. Initially, the target blood pressure might be lower than usual – this is called “permissive hypotension”. Once the bleeding is controlled, the doctor will aim for a higher blood pressure.
Broken bones, especially in the legs or pelvis, can cause significant blood loss. For example, a broken thigh bone can cause a loss of one liter of blood, and a broken pelvis can cause even more blood loss. Therefore, it’s important to control bleeding, especially from fractures, as soon as possible. The saying “blood on the floor, plus four more” means that a dangerous amount of blood can be lost inside the body and may not be immediately visible. This phrase is typically used when considering blood loss due to injuries or broken bones.
It’s important to note, transfusions are not a substitute for stopping bleeding. The best treatment for severe blood loss is to control the source of the bleeding as soon as possible.
Possible Complications of Shock Resuscitation
During treatment for severe blood loss, known as hemorrhagic shock, it’s often necessary to give the patient more blood than initially anticipated. Most hospitals are prepared for these situations with a “massive transfusion protocol.” A “massive transfusion” means the patient has received enough blood to replace their entire blood volume within 24 hours.
To help ensure the new blood clots properly, a rapid infuser can be used. This device warms the blood products before they’re given to the patient. The rate at which the blood is transfused depends on the patient’s condition and vital signs. As the process continues, the patient’s complete blood count (CBC), prothrombin time (PT), partial thromboplastin time (PTT), international normalized ratio (INR), fibrinogen level, and ionized calcium levels are checked every time they’ve received 5-10 units of packed red blood cells (pRBCs).
These checks are critical because, during a massive transfusion, a patient’s platelet count can drop dangerously low, and blood clotting can be affected. These problems can happen because of the large volume of added blood diluting and affecting the normal balance of cells and proteins in the blood.
Also, ionized calcium levels can decrease quickly during a massive transfusion. This is due to an additive called citrate, contained in the transfused blood, which can bind with the calcium and makes it inactive. Under normal conditions, the liver can clear out the citrate within 5 minutes, but citrate can accumulate during massive transfusions – this results in less calcium available for body’s normal functions.
To help prevent complications, for every 500 cc of blood products given, healthcare providers may add 10-20 cc of calcium gluconate or 2-5 cc of calcium chloride via intravenous injection. This helps bring the calcium levels back up to normal, reducing potential risks.
What Else Should I Know About Shock Resuscitation?
Shock resuscitation involves treating a serious condition called shock, which can occur due to significant blood loss. This blood loss can be hidden in different parts of the body like the chest, belly, pelvis, or thighs, so the first signs of shock due to bleeding may not be immediately obvious. Besides injuries, blood loss can also occur due to medical conditions like an internal bleed in the gastrointestinal system or issues with blood clotting. Therefore, doctors must be alert to changes in things like heart rate or blood pressure to catch shock early. A patient’s overall appearance can also sometimes give clues about their condition. For example, if the patient appears sweaty and noticeably uncomfortable, the doctor may suspect shock, especially if other symptoms are also present.
Shock often brings observable changes like a decrease in the gap between the systolic and diastolic blood pressure (pulse pressure), increased heart rate, or slight increase in breathing rate. One of the most telling signs could be a decrease in urine output because the kidneys start getting lesser blood supply than they need (a condition known as hypoperfusion). If urine output falls below 30 ccs/hr or less than 0.5 ccs per kg of body weight per hour, it suggests that the kidneys are not getting enough blood, which can be an early sign of shock. However, there could be other reasons for this reduced blood supply to kidneys, and the patient’s complete health history and physical examination results need to be considered.
For instance, patients on certain medicines like beta-blockers may have reduced blood pressure and kidney blood supply not related to blood loss. Therefore, a thorough physical examination is necessary to check for evidence of blood loss like lesser lung sounds due to blood in the chest cavity, or increased belly size or pain due to blood in the belly. People with blood clotting problems might also develop blood-filled swellings in the psoas muscle, which lies in the lower back area. This can be hard to catch just by examination. If there is unexplained pain in lower limb movements, it should raise suspicion. A CT scan of the belly and pelvis with a special dye can be useful in diagnosing bleeding in the psoas muscle or other areas in the back of the abdomen.
