where
Q = Flow in L/s
μ = Viscosity in Pa s
P = Pressure in Pascals
r = Radius of the tube in meters
L = Length of the tube in question in meters
Essentially, large bore size and short length are needed to maximize flow. Tables 17.1 and 17.2 outline typical flows seen with catheters.
Table 17.1
Flow characteristics in peripheral vascular catheters
Gauge size | Inside diameter (mm) | Length (mm) | Flow rate (mL/min) |
---|---|---|---|
16 (grey) | 1.3 | 30 | 220 |
18 (green) | 1.0 | 30 | 105 |
50 | 60 | ||
20 (pink) | 0.8 | 30 | 60 |
Table 17.2
Selected characteristics of triple-lumen central venous catheters and intraosseous access
Size (Fr) | Length (cm) | Lumens | Lumen size (Ga) | Flow rate (mL/min) |
---|---|---|---|---|
7 | 16 | Distal | 16 | 57 |
Medial | 18 | 30 | ||
Proximal | 18 | 32 | ||
7 | 20 | Distal | 16 | 52 |
Medial | 18 | 25 | ||
Proximal | 18 | 27 | ||
7 | 30 | Distal | 16 | 38 |
Medial | 18 | 17 | ||
Proximal | 18 | 18 | ||
8.5 (Cordis) | 10 | Single | 8.5 Fr | 333 |
Intraosseous [24] | 5 | Single | 15 | 165 |
Peripheral Intravenous Access
Peripheral intravenous access is the mainstay of early fluid resuscitation of critically ill patients. Indications for peripheral intravenous access include venous blood sampling, intravenous fluid and medication infusion, blood transfusion, and intravenous contrast administration. Access points include both upper and lower limbs including the long saphenous, cephalic, basilic, and median cubital veins. Contraindications to intravenous access include extremity with significant edema, burns, sclerosis, phlebitis, or thrombosis, and ipsilateral radical mastectomy. Early complications include bruising infiltration, interstitial fluid/medication delivery, thrombophlebitis, infection, nerve damage, and thrombosis [24].
Central Intravenous Access
Central venous catheterization is used to access central veins for medication and fluid delivery and patient monitoring of central venous pressures and right-heart catheterization. A variety of sites can be used including femoral, subclavian, and internal/external jugular veins. Each site has its own set of advantages, disadvantages, and risk of complications outlined in Table 17.3.
Table 17.3
Central line placement
Site | Advantages | Disadvantages | Complications |
---|---|---|---|
Internal jugular | Anatomic landmarks are easy to identify with ultrasound | Difficult to access during emergency airway management | Pneumothorax |
Hemothorax | |||
Head-of-table access | Risk of carotid artery puncture | Chylothorax | |
Can recognize and control bleeding with direct pressure | Patient discomfort | Neck hematoma and tracheal obstruction | |
Minimal risk of pneumothorax | Vein prone to collapse with hypovolemia | Endotracheal cuff perforation | |
Malposition of catheter placement is rare | Avoid if concern about cerebral perfusion | Tracheal perforation | |
Avoid in cervical trauma patients | Brachial plexus injury | ||
Air embolism | |||
Cardiac dysrhythmia | |||
Thrombosis | |||
Subclavian | Good external landmarks | Unable to compress bleeding vessels | Pneumothorax |
Improved patient comfort | Blind procedure | Hemothorax | |
Easier to maintain dressings | Experience related success rate | Brachial plexus injury | |
Accessible during airway management or patients with C-spine collars | Longer path from skin to vessel | Hematoma | |
Catheter malposition | Air embolism | ||
Cardiac dysrhythmia | |||
Thrombosis | |||
Femoral | Good external landmarks allowing for rapid access | Limits patient mobilization | Arterial puncture |
Technically easy | Delayed circulation of drugs during CPR | Bowel injury | |
Does not interfere with CPR | Difficult to keep site sterile | Retroperitoneal hematoma | |
Useful alternative with coagulopathy | Increased risk of iliofemoral thrombosis | Psoas abscess | |
Trendelenburg position not required | Not reliable for CVP or central venous gas measurements | Bladder injury | |
Air embolism |
Indications for central venous access include emergency venous access; high-volume/flow resuscitation; central venous pressure monitoring; inability to obtain peripheral venous access and repetitive blood sampling; administration of hyperalimentation, caustic agents, or concentrated fluids; hemodialysis or plasmapheresis; and placement of transvenous cardiac pacemakers or pulmonary artery catheters. Contraindications for central venous access include infection over the placement site; distortion of landmarks by trauma or congenital anomalies; coagulopathies, including anticoagulation and thrombolytic therapy; pathologic conditions, including superior vena cava syndrome; current venous thrombosis in the target vessel; prior vessel injury or procedures; morbid obesity; and uncooperative patients. Complications for central venous access are outlined in Table 17.3. Infection rates for internal jugular, subclavian, and femoral central lines are reported as 8.6, 4.0, and 15.3 rate per 1,000 catheter-days, respectively [24]. Thrombosis of internal jugular, subclavian, and femoral central lines are reported as 1.2–3, 0–13, and 8–34 rate per 1,000 catheter-days, respectively [24].
During trauma resuscitation the choice of access site however may be practically more limited. Internal jugular line placement is often the least desirable due to cervical spine collars and spinal precautions. While subclavian access may be attractive, the real estate at the head and torso is often in high demand during resuscitation as often there are five or more team members already trying to access this area for airway management, chest examination, chest tube placement, etc. Therefore often the femoral vein is the first choice for emergent/urgent central access despite the higher long-term infection rates [24]. Added advantages for emergency femoral access include lower short-term complications including zero risk of hemothorax, pneumothorax, and airway compromise from neck hematoma, which could potentially complicate an already unstable patient. This line can be converted to an upper extremity line once the patient is stabilized. Femoral access should be avoided in patients with pelvic or lower extremity injury and patients with known vascular pathology.
An obvious but often forgotten practical consideration when choosing a site for upper extremity lines is in the presence of a known pneumothorax, hemothorax, or chest tube, any upper extremity central line should ideally be placed on the ipsilateral side to avoid creating bilateral chest complications. Utilization of dynamic ultrasound guidance allows access to brachial and basilic veins in the upper extremity. The basilic is not just capable of accepting the largest peripheral lines but also longer central lines which may then terminate in the proximal subclavian vein (peripherally inserted central venous catheters). The utility of such peripherally placed lines is obvious.
A common misconception is the absolute necessity of central venous access for vasopressor infusions. Certainly in the long term a central venous line is a safer mode of delivery for these drugs; however, in the trauma bay or code situation any vasopressor can be run through either a large-bore peripheral line or intraosseous line until central venous access can be established. The main risk is tissue necrosis with extravasation and therefore care should be taken to ensure there is good flow and the peripheral line does not become dislodged. Policies and procedures may vary by institution and care location (trauma bay versus intensive care unit), and we therefore suggest reviewing your local policies and drug monographs.
Intraosseous Access
Intraosseous (IO) access is a technique where a needle is advanced into the bone marrow to achieve an entry point into the systemic venous system. IO route provides a rapid and effective means of administering drugs, fluid, and blood. Blood can also be drawn from an IO device and used for blood gases, electrolyte and hematologic evaluation, and blood cultures [25–27]. This technique is indicated for adult patients in whom attempts at peripheral or central venous access have been unsuccessful. This may include adult patients with burns, trauma, shock, dehydration, or status epilepticus [28]. Multiple sites, including the iliac crest, femur, proximal and distal end of the tibia, radius, clavicle, and calcaneus may be used [29–32]. A wide variety of commercial IO devices are currently available, making the insertion very user friendly. It is important the provider is familiar with local hospital practice and equipment. Detailed description of IO placement is provided elsewhere [33]. IO devices should be avoided in those sites where there is orthopedic or vascular trauma because of the risk of extravasation. Other relative contraindications include cellulitis or burns over the insertion site, patients with known underlying bone disease such as osteogenesis imperfecta, and previous IO attempts on the ipsilateral side. Technical difficulties are the most common complications and are associated with equipment unfamiliarity. Complications of IO devices include malposition resulting in skin and bone trauma, compartment syndrome from unrecognized extravasation, epiphyseal injuries, and fat embolism. Prior to using an IO site 10 cm3 of normal saline should be flushed through the line. Infusion of fluids through the needle at high rates is sometimes associated with patient discomfort; therefore in awake patients infusing 20–40 mg of 2 % lidocaine without epinephrine will dramatically reduce this discomfort. IO access is meant only for temporary access and should be removed within the first 24 h.
Ultrasound
The use of ultrasound-guided central line placement has become a standard of care. Ultrasound provides a real-time window of a patient’s vascular anatomy with the ability to directly visualize placement of central lines into a vessel. Traditional use of anatomical based landmarking for central venous access has resulted in failure and complication rates as high as 19 % and 30 %, respectively [32]. Ultrasound-guided central venous line placement has been demonstrated to significantly decrease the failure rate, complication rate, and number of attempts required for successful access [34–36]. Similarly, ultrasound guidance for peripheral venous line placement has shown marked increase in total and first-pass success in a variety of clinical settings.
A recent randomized, multicenter trial using ultrasound-guided central venous cannulation reported that sonographic guidance had an odds improvement of 53.5 (6.6–440) times higher than landmark-based technique for success of cannulation [37]. The average number of cannulation attempts was also significantly lower in the ultrasound-guided group. The frequency of complications related to line placement is reduced with the use of ultrasound. For internal jugular line placement arterial punctures are reduced from 9.4 to 1.8 %, hematomas 2.2 to 0.4 %, and pneumothorax 0.2 to 0 % [38–40].
In the emergency situation, however (especially when no other access is available), the risk of potential increased complications from landmark-based central line insertion should be weighed against potential time delay from setup for an ultrasound-guided procedure and or lack of an ultrasound being available.
Resuscitative Thoracotomy
A resuscitative thoracotomy (RT) is an emergency procedure used to gain access to the chest in severely injured patients. The decision to perform an RT should be guided by consideration of mechanism of injury and signs of life. The rationale for performing an RT is (1) release of cardiac tamponade, (2) control of intrathoracic hemorrhage, (3) evacuation of air embolism, (4) performance of open cardiac massage, and (5) cross-clamping of the descending thoracic aorta [41, 42]. Given the potential risk involved to healthcare workers the decision to undertake an RT must be made in the context of an anticipated successful clinical outcome, and familiarity of performing the procedure. Trauma patients arriving to the emergency department (ED) pulseless should be assessed for clinical history, cardiac rhythm, and a brief neurologic examination prior to commencement of an RT. Patient management is guided initially by mechanism of injury and downtime. Victims of blunt trauma with no signs of life upon arrival to the ED universally have poor survival rates (<1 %) [42, 43]. RT should not be performed in this population. Patients with penetrating thoracic injury with previously witnessed cardiac activity within 15 min of presenting to a trauma center or unresponsive with hypotension (SBP < 70 mmHg) despite ongoing resuscitation should be considered for an RT. Relative indications for RT include penetrating thoracic injury with traumatic arrest with previously witnessed cardiac activity, and penetrating non-thoracic injury with traumatic arrest with previously witnessed cardiac activity (pre-hospital or in-hospital). Other indications for urgent thoracotomy include (1) chest tube output >1,000 mL, (2) evidence of ongoing bleeding following placement of a tube thoracostomy at a rate of 200–300 mL/h for 4 h, (3) massive chest tube air leak, (4) cardiac tamponade, and (5) air embolism [41–43]. Despite these indications, providers must also consider the patient disposition for definitive surgical repair following a successful RT. Limitations in hospital infrastructure and personnel may prevent successful outcomes. An RT is conducted through anterolateral thoracotomy along the fifth intercostal space on the side of the injury. Although the procedure is not technically difficult, once inside the thoracic cavity, it is imperative that there be a surgical expert present or close by to deal with the next steps of definitive management. Detailed surgical steps of an RT are detailed in Table 17.4 [44].
Table 17.4
Operative technique for resuscitative thoracotomy