Hypovolemic Shock

Hypovolemic shock-Heart rate and respiratory rate

-May be increased. -Heart rate may be increased because body is trying to compensate by increasing cardiac output.

Describe adverse effects associated with colloid solutions:

1. AKI 2. Bleeding 3. Increased Na/Cl in some

Discuss the pathophysiology of hypovolemic shock:

1. Blood volume decrease --> O2 delivery decreases --> cellular death + increased cytokines (inflammatory response). 2. Lethal triad --> acidosis (pH decreases) + hypothermia (temp drops) + coagulopathy (clot formation decreases). 3. Body tries to compensate for the 02 lack of delivery by releasing: -Vasopressin --> kidneys retain more water -Catecholamines --> increases HR--> vasoconstriction--> increases systemic peripheral resistance-->increase blood pressure.

What is the clinical presentation of hypovolemic shock?

1. Can vary based on age of the patient, comorbidities, medications, and extent of volume depletion. -->Ex. if a patient lost < 10 ml/kg of total body weight. If 80 kg then 800 ml loss. If someone has lost 800 ml of fluid then the sx are relatively minor. -->If lost > 30 ml/kg, 80 kg so about 2.4 L. Now you will have sx, laboratory abnormalities, vital signs changes Presentation 1. Look at mental status. Unconsciousness, confusion, etc. Sign of low perfusion to the brain 2. Could have highly concentrated urine (darker urine) or not be making any urine so always look at urine output. -->Most adults should put out 1 ml/kg/hr. -->Catheter is placed in bladder to measure urine output.

Discuss the pathophysiology of hypovolemic shock

1. Decrease in blood volume, so decreased oxygen delivery to tissues leading to cellular death. This leads to inflammatory cytokines and other intracellular processes that leads to cell death. 2. Leads to triad -->Acidosis - Decreased pH -->Hypothermia - Decreased body temperature -->Coagulopathy - Lower amounts of clotting factor. Predisposed to bleeding -->Especially in trauma patients where a lot of blood has been lost. 3. Body tries to compensate in decreased blood volume 1. *Transcapillary shift* -->Fluid move from inside the cell to interstitial space to intravascular fluid. To maintain blood pressure. 2. *Hormone release* Vasopressin - Help the kidney retain more fluid Catecholamines - Will try to increase HR and cause vasoconstriction. Causes systemic vascular resistance which leads to increased BP. The responses can also be damaging. Vasoconstriction can lead to decrease delivery of oxygen If the heart is now pumping faster, then its oxygen demand also goes up. So if vasoconstriction then lack of oxygen to heart which can lead to MI. 3. *Body compensates by prioritizing blood flow to the most important organs.* Heart and brain Happens at expense of other organs. For example decreased blood flow to the bowel causing bowel injury (infarcted bowel)

What are appropriate fluids for hypovolemic shock?

1. First line is *isotonic crystalloids* → 09% NaCl (normal saline) Patients usually give 1-2 L as rapidly as possible to increase blood volume. *NS is used for resuscitation* 2. Why not D5%W Because a lot of it goes into the intracellular space compared to normal saline which stays in the extracellular fluid (100%) If you give someone 1 L of normal saline, about 250 ml will be in the intravascular space and 750 ml in the interstitial space. This is why NS is used or resuscitation because we want fluids to go the extracellular space to increase the blood that's in the vascular. D5%W is better for someone who is dehydrated. What about D5% 1/2NS Instead of 0.9% NS, it's 0.45% NS. Think of this as in between D5 and NS Also not used for resuscitation! Mainly used as a maintenance fluid. 3. Lactated ringers Another crystalloids. Has less sodium than normal saline. For NS → there is 154 mEq/L LR → there is 130 mEq/L Blood NaCl is about 140 mEq/L (normal) so when we give someone NS (154 mEq/L) that's slightly higher than body's NaCl. That's why when someone is given really large amounts of NS they could develop hypernatremia or hyperchlorimic metabolic acidosis. Lactated ringers contain lactate. Lactate is also used as an indicator of perfusion. So if you give someone lactate, perhaps that could throw off the monolactate that you are measuring. But it has been shown that the lactate that's given with LR is not that clinically significant. 4. Proposed alternatives to isotonic crystalloids Albumin, hetastarch, dextran and hypertonic saline.

What are common fluid ADEs?

1. Hypervolemia 2. Pulmonary edema 3. Kidney injury and bleeding (this is not as common and mainly associated with HES and Dextran).

Describe the major fluid compartments within the body in terms of fluid distribution:

1. Intracellular: 2/3 2. Extracellular: 1/3 ---> 25% intravascular ---> 75% interstitial

Given a specific volume of a crystalloid or colloid solution determine the approximate distribution within the different fluid compartments:

1. NS → 100% ECF 2. D5 → most ICF → hence preferred for dehydration 3. Lactated ringers → like NS???? Slightly more hypotonic 4. Albumin → IVF benefit increases pressure/fluid without giving liters of NS - small amount (but not improving the outcome compare to NS) 5. Hypertonic saline → stays in vascular (less volume is given but increases Na/Cl) → no benefit over NS 6. Hydroxyethyl starch → stay within vasculature → lower MW causes renal dysfunction can cause acute kidney failure bleeding 450/0.7 (MW/substrate of glucose) → variable MW 7. Dextran → not used - SE like hydroxyethyl starch (hetastarch )

Hypovolemic shock-Lab parameters:

1. Sodium and Chloride Most important for fluid status. If these are low? (I think high!) could be sign of volume depletion but it could be normal if someone has acute blood loss. 2. BUN/Scr Will increase. However overtime as the Scr goes up, the ratio will come down. 3. Lactate If increased then sign of poor oxygen delivery. In the absence of oxygen there is a lot of production of lactate. Patients may have acidosis. Decrease in pH, elevated base deficit 4. Liver Increased in liver enzymes (AST/ALT) due to poor perfusion to the liver resulting is death which release these enzymes?. Sometimes called a shocked liver.

Explain the difference between dehydration and hypovolemia:

Dehydration: means loss of water (intracellular fluid). Hypovolemia: means low blood volume-which is not identical to dehydration because blood is not pure water (extracellular fluid).

Select an appropriate fluid for use in hypovolemic shock:

First line: 0.9% NS--> 100% goes into the ECF (154 mEq) -Lactate ringers--> 130 mEq= less tonicity than NS but more than D5.

Hypovolemic shock-Blood pressure

Likely hypotensive. --> <90 mmHg --> Be sure to look at the BP relative to the patient's normal BP.

Identify signs, symptoms, and laboratory abnormalities that may be associated with hypovolemic shock:

Loss of >30 mg/kg of total body weight--> severe. Lab abnormalities include; 1. BUN/SCr --> initially increased. 2. HR and RR --> increase because body is trying to compensate by increasing cardiac output. 3. Lactate --> increases due to poor oxygen delivery = anaerobic 4. Acidosis 5. Liver function test --> increased AST/ALT --> shock liver =dysfunction 6. Blood pressure <90 mmHg or reduction of 40 mmHg from baseline.

Explain the problem with compounding albumin 5% from 25% by adding sterile water for injection:

Na will be low in that solution → hypotonic! No benefit of doing it this way!

Discuss major differences between available crystalloid and colloid solution:

See #4 and #7

Describe the use of permissive hypotension as a goal for fluid resuscitation:

Since there are complications associated with increasing blood pressure in trauma patient It is OK to have their blood pressure around 90 mmHG and MAP around 60 We give fluid but do not want to give too much since you can dilute out coagulation factors → decrease plasma and clotting factor and de-stabilizing existing clots and worsening bleeding

Hypovolemic shock-Body temperature

This won't really change.