Phlebotomy is defined as the act of entering the vein for the purpose of drawing blood. The testing of blood samples can yield a vast amount of information as to the myriad of physiologic processes of the body, genetics, immunologic response, and the presence of bacteremia. As an alternative, blood can be obtained via pinprick for certain basic tests (i.e. blood glucose), but is limited in usefulness for most tests due to cell hemolysis and contamination with interstitial fluid, surface substances and organisms. Furthermore, most blood tests require 3–10 mls of blood per tube (possibly less if using a pediatric laboratory). While frequent reference to phlebotomy is made in this chapter, the technique is covered in detail in a separate chapter.
Contrast-Enhanced Imaging
Intravenous contrast imaging allows clear and specific enhancement of vessels and organs based on perfusion. Imaging studies such computed tomography (CT scans), magnetic resonance imaging (MRI), nuclear studies and x-ray intravenous imaging such as intravenous pyelography can provide extensive information as to the presence of active bleeding, infection, and structural or functional compromise.
The timing of contrast injection in relation to image capture can allow selective enhancement of the arterial or venous circulation. Arterial-phase imaging allows identification of brain aneurysms, aortic dissection, and other arterial compromise.
Crystalloid fluids used in resuscitation include normal saline, lactated ringers, or dextrose-containing fluids. In critical situations such as extensive blood loss, shock or trauma, a minimum of 2 large bore IVs (at least 18 guage) should be placed. If sufficient peripheral access cannot be obtained in a timely fashion, central venous access should be secured without hesitation.
Medication Administration
Intravenous medications are often superior to oral medications in speed of action, absorption and systemic penetration (due to independence from GI absorption and bypassing first-pass metabolism in the liver).
When administering intravenous medications however, care must be taken that medications administered simultaneously are compatible (certain substances interact and can precipitate out of solution). Rate of administration must also be monitored to minimize vascular irritation and possible precipitous effects of potent medications.
Blood Product Transfusion
Peripheral IVs can be used for the transfusion of packed red blood cells, platelets, plasma, and other blood products. When large volume or rapid infusion is required due to shock or acute blood loss, however, large bore central access is preferred (e.g. internal jugular sheath introducer).
Short-term Parenteral Nutrition
Peripheral intravenous access can be used for the short-term provision of parenteral nutrition. Long-term parenteral nutrition requires a central venous catheter placed under sterile conditions.
Contraindications
Pre-existing Vascular Compromise
Lymphatic or venous drainage has been compromised, i.e. lymph node dissection accompanying mastectomy, A-V fistulas, injured extremities, thrombosis.
Peripheral intravenous access is virtually ubiquitous in daily medical practice, for both diagnostic and therapeutic purposes. 
Phlebotomy is defined as the act of entering the vein for the purpose of drawing blood. The testing of blood samples can yield a vast amount of information as to the myriad of physiologic processes of the body, genetics, immunologic response, and the presence of bacteremia. As an alternative, blood can be obtained via pinprick for certain basic tests (i.e. blood glucose), but is limited in usefulness for most tests due to cell hemolysis and contamination with interstitial fluid, surface substances and organisms. Furthermore, most blood tests require 3–10 mls of blood per tube (possibly less if using a pediatric laboratory). While frequent reference to phlebotomy is made in this chapter, the technique is covered in detail in a 
Crystalloid fluids used in resuscitation include normal saline, lactated ringers, or dextrose-containing fluids. In critical situations such as extensive blood loss, shock or trauma, a minimum of 2 large bore IVs (at least 18 guage) should be placed. If sufficient peripheral access cannot be obtained in a timely fashion, central venous access should be secured without hesitation.
