TRANSITION SERIES Topics for the Advanced EMT CHAPTER Blood, Cardiac Function, and Vascular System 9 9

Objectives Identify the components of blood volume. Identify the roles of hydrostatic pressure and plasma oncotic pressure. Determine the variables that play into cardiac output.

Objectives (cont’d) Identify the variables that affect systemic vascular resistance. Discuss roles of the autonomic nervous system in perfusion.

Introduction Multiple variables must interact in just a certain way for normal perfusion: –Oxygen –Alveoli –Cardiac function –Systemic vascular resistance –Blood volume and its components

Blood Volume Composition of blood –Formed elements (45%)  RBC  WBC  Platelets –Plasma (55%)  91% water  Albumin, antibodies, clotting factors

Blood Volume (cont’d) Distribution of blood –Arteries –Veins –Organs

Distribution of Blood in the Cardiovascular System

Blood Volume (cont’d) Hydrostatic pressure –Created by myocardial contraction and vasoconstriction. –Forces fluid out of the vascular space. –Disturbances can create emergencies.

Blood Volume (cont’d) Plasma oncotic pressure –The force exerted by large plasma proteins in blood vessels. –Helps to keep fluid in the vascular space.

Blood Volume (cont’d) Effects of hydrostatic or oncotic pressure changes –High hydrostatic pressure –Low hydrostatic pressure –High oncotic pressure –Low oncotic pressure

Hydrostatic pressure pushes water out of the capillary. Plasma oncotic pressure pulls water into the capillary.

Pump Function of the Myocardium Heart must work effectively –Cardiac output  Heart rate and stroke volume –Stroke volume  Preload  Contractility  Afterload

Pump Function of the Myocardium (cont’d) Disturbances can cause emergencies –Decrease/Increase in heart rate –Decrease/Increase in blood volume –Decrease/Increase in ventricular contractility –Decrease/Increase in sympathetic tone –Decrease/Increase in parasympathetic tone

Systemic Vascular Resistance Systemic vascular resistance (SVR) –Resistance offered to the flow of blood through a vessel  Vasoconstriction  Vasodilation –Effects of changes in autonomic tone  Sympathetic  Parasympathetic

Systemic Vascular Resistance (cont’d) SVR and pulse pressure –Effects of vasoconstriction –Effects of vasodilation –Pulse pressure changes  Normal pulse pressures  Abnormal pulse pressures

Microcirculation Microcirculation –Flow of blood through the smallest of blood vessels  Arterioles  Venules  Capillary beds –Regulatory influences

Microcirculation is the flow of blood through the smallest blood vessels: arterioles, capillaries, and venules. Precapillary sphincters control the flow of blood through the capillaries.

Blood Pressure Blood pressure –Measure of cardiac output  B/P = CO x SVR –Both cardiac output and systemic vascular resistance have direct effect on blood pressure

Blood Pressure (cont’d) Effect of baroreceptors and chemoreceptors –Baroreceptors  Detect blood pressure –Chemoreceptors  Detect blood chemistry (O 2, CO 2, H+)

Case Study You are dispatched for a patient with a “chest injury” at 0230 hrs. Dispatch information was lacking due to the caller being hysterical and difficult to understand. As a precaution, PD and FD are also dispatched to the same residence. When you roll up on scene, 8-10 people are crowded around the front door of the home.

Case Study (cont’d) Scene Size-Up –Standard precautions taken –PD not on scene yet, entry blocked due to crowd of people –Unknown age of the patient –MOI is a suspected chest injury –An ALS FD is responding behind you

Case Study (cont’d) What are your immediate concerns at this time? Given the presence of EMS and FD, should the house be approached?

Case Study (cont’d) PD arrives on scene and quickly disperses the crowd of people on the porch. They wave you inside and as you approach an officer tells you that the patient is unresponsive inside. The “story” they get is that the male was cleaning his guns when one accidently discharged, resulting in the patient shooting himself.

Case Study (cont’d) Primary Assessment Findings –Mid-20s age, male patient –Patient unresponsive, blood-soaked shirt –Pupils slow to respond to light –Slight inspiratory snoring noted with breathing

Case Study (cont’d) Primary Assessment Findings –Respirations rapid and shallow –Carotid pulse 120/min, peripheral pulse absent –Peripheral skin cool and clammy

Case Study (cont’d) How would you prioritize this patient? What are the patient's life threats, if any? What care should be administered immediately?

Case Study (cont’d) Medical History –Unknown Medications –Unknown Allergies –Unknown

Case Study (cont’d) Pertinent Secondary Assessment Findings (continued) –Pupils sluggish to respond, membranes dry –Airway patent with manual technique –Breathing shallow, no right side breath sounds –Central pulse present, peripheral absent

Case Study (cont’d) Pertinent Secondary Assessment Findings (continued) –Skin is pale, cool, and clammy –Open GSW injury to right chest –B/P 108/86, HR 110, Resp 24 and shallow –No other indications of trauma noted

Case Study (cont’d) What are the reasons for the following findings? –Altered mental status –Disturbance to breath sounds –Tachycardia –Pulse pressure –Skin characteristics

Case Study (cont’d) Care provided: –Patient immobilized as a precaution –High-flow oxygen with PPV –Occlusive dressing applied to GSW site –Initiate intravenous access –Emergent transport to the hospital

Summary Along with the body maintaining oxygenation, it must also provide for adequate peripheral perfusion. In situations of poor peripheral perfusion, blood will be shunted to the core organs. Early identification of a failing cardio- vascular system underscores the need for rapid transport to the hospital.