Cooling provides crucial protection for the cells, but the application of hypothermia causes some additional damage which must be addressed. Cooling causes blood vessels to become constricted, blood viscosity to increase, and red cells to clump together. Oxygen becomes more tightly bound to the hemoglobin and less accessible to the tissues. After cooling, cardiopulmonary support (CPS) is the next step in stabilization, and it will help address the damage caused by ischemia.
Cardiopulmonary support is an artificial means for providing blood flow and tissue oxygenation following cardiac arrest. It is used during a suspension — particularly in the transport phase — to maintain cerebral and myocardial viability until cryoprotective perfusion can be initiated. CPS is always administered in conjunction with surface cooling.
As with every aspect of the stabilization protocol, multiple options exist to bolster respiration and circulation during cardiopulmonary support. The common options, their advantages and disadvantages, will be discussed later in this chapter.
Cardiopulmonary support restores some function to the respiratory and circulatory systems — which is a considerable improvement to the initial absence of heartbeat and breathing in transport patients. Mechanical devices, used to oxygenate and circulate fluids, do not compare in performance to a healthy heart and lungs. While inadequate perfusion is potentially dam-aging, there is no doubt that patients with transports including CPS later have better cryoprotective perfusions.
Restoring circulation will improve cooling rates, enable the administration of medications to slow ischemic and hypothermic injury, provide the cells with an outlet for the waste products of normal metabolism and ischemia, and improve the cryoprotective perfusion.
Closely related to CPS is the conventional clinical practice of cardiopulmonary resuscitation (CPR), which is an artificial means of preserving blood flow in an effort to maintain cerebral and myocardial viability until normal circulation can be restored using either electrical defibrillation or pharmacologic intervention. With the exception of “until normal circulation can be restored…,” the goal of the Alcor transport team’s cardiopulmonary support (CPS) is identical to that of CPR: the maintenance of neuronal structure and circulatory system viability. The implied goals of immediate resuscitation (CPR) and future resuscitation (CPS) are different. However, they are similar enough that the extensive research into CPR methods and effectiveness is applicable to the development of cryonic suspension protocols. CPS, as the term used in this manual, will refer to conventional CPR techniques as well as those specifically intended for cryonic suspension.
Nowhere else in a cryonic suspension is time so important as in the application of cardiopulmonary support. The outcome of a cryoprotective perfusion will largely be determined by the quality of CPS. Steps include establishing a patent (open) airway, through which oxygen is administered; restoring circulation through manual or mechanical means (see Chapter 7); and the administration of a medication protocol to reduce the damage caused by cardiac arrest (see Chapter 8).
This chapter will consider the impact of cardiopulmonary support on the respiratory system and methods for placing an airway.
The Respiratory System
The respiratory system consists of the organs (and associated muscles) which obtain oxygen and position it for pick-up and distribution by the circulatory system, which then delivers it to every cell in the body. Waste products (like carbon dioxide) are produced as the oxygen is consumed and removed from the body via circulation and respiration.
Air is inhaled through the nose or mouth and passes through the upper air passages and into the trachea. From the trachea, air travels through a passage called a “bronchus.” At the base of the trachea, the volume of air is forced into either the right main or the left main bronchus. The bronchi, together with their thin-walled branchings (bronchioli), eventually separate the air into thousands of tiny caverns, called “alveoli.” The alveoli hold oxygen until it can be diffused into the bloodstream or exhaled.
How much oxygen and carbon dioxide is exchanged between the lungs, the tissues, and the cells depends on many factors, including:
the amount of oxygen taken into the lungs, which during a transport is generally 100% and during normal respiration is about 21%
hemodilution — the concentration of red blood cells
cardiac output — a product of the pressure and volume of arterial blood
the quality of the distribution of blood through the vessels
pulmonary function — the efficiency of gas exchange mechanisms and
the speed of diffusion
pulmonary obstruction — pulmonary function may be impaired by edema or other obstruction
Cardiopulmonary support can be performed on almost any patient, but the efficacy of CPS may be compromised if the patient has undergone an agonal course or has a history of illnesses (like pneumonia, emphysema, cancer, or any other ailment) which affects the surface area of the lungs, and hence, oxygen exchange capacity.
Once circulation has been reinitiated, large amounts of oxygen will be needed to fuel cell repairs. Oxygen must be available to the lungs, which then deliver oxygen to the circulatory system. For this, a patent airway is required.
Primary Airway Access
Inhaled air quickly moves from the nose or mouth into the trachea. The trachea is a tube, measuring about 4½” in length, which extends to the lungs. There are no muscles or bones surrounding the trachea, but it is protected by bands of tough cartilage. One of the quickest methods for enabling the delivery of oxygen to the patient’s lungs during a transport is to place an airway directly into the trachea. The technique used to place this tube is called a “tracheotomy” (or “tracheostomy”). Additional methods may be used to provide a functional airway for the transport patient, and descriptions of these will follow.
Tracheotomies provide the fastest and most certain access to the respiratory system of a patient. Using this method, an airway may be placed securely and with little chance of becoming dislodged, if the steps below are followed.
Tracheotomy tubes must be correctly placed to seal the airway. One of the less pleasant side-effects of CPS is that the patient may vomit. By sealing the trachea, the lungs are protected from aspiration — the intake of foreign material into the lungs during breathing. The aspiration of the stomach contents (hydrochloric acid is one substance used in digestion) would block the airway and damage the delicate tissue, and as a result, reduce the quality of gas-exchange.
Placing this airway will require an incision. This means that a potential biohazard exists if the transport team member comes into direct contact with the patient’s body fluids or contaminated cutting utensils. Wear gloves when performing a tracheotomy — highly recommended are latex gloves worn over puncture-resistant ones.
Performing a tracheotomy
All equipment needed to perform a tracheotomy should be assembled in advance and placed where it is immediately accessible and within reach when the airway is required.
Locate the thyroid cartilage (the “Adam’s apple”) by tilting the patient’s head back and palpating below it for the “V” notch of the cricoid cartilage. Use the thumb and forefinger of one hand to stabilize during palpation, placing the palm above the thyroid cartilage if needed. When you have located the “V” notch, slide your index finger into the depression between the thyroid and cricoid cartilages. At the base of this depression is the cricothyroid membrane, and where you will ultimately place the airway. Swab the area with either Betadine or alcohol to cleanse.
Still stabilizing the trachea with one hand, make an incision (see illustration) through the cricothyroid membrane using the scalpel. There are several large blood vessels on either side of the trachea, and these must not be cut. The scalpel should be applied with sufficient pressure to pass through the soft tissues of the neck and open the trachea. Use the gauze to wipe up any blood which might reduce visibility.
Performing a tracheotomy requires practice. During training sessions, corrugated plastic tubing provides a fairly realistic simulation of the trachea.
Once the incision is large enough to pass the tracheotomy tube into the trachea — still immobilizing the trachea with one hand — insert the tube with the cuff end pointing toward the patient’s feet. Use the syringe to inflate the cuff (with about 20cc of air) until a seal is formed around the edges of the trachea. An ineffective seal will result in oxygen audibly leaking around the edges, and little air will reach the patient’s lungs.
The tiny balloon at the air-inlet of the cuff will have pressures similar to that of the cuff itself. Squeezing it gently between thumb and forefinger will tell you if the cuff at the end of the tube is inflated to capacity. The balloon should not be completely inflexible. Be careful not to overinflate the cuff, as this will burst the seal and make it impossible to seal the airway.
Connect the oxygen source to the tracheotomy tube (usually the HLR), and then secure the tube to the patient’s neck using the cloth strings (wrap the ties around the neck and knot in place). If an oxygen source isn’t yet available, use air and an Ambu bag to provide ventilation at the rate of 16-20 breaths per minute.
Cooling may affect the airway seal, since the air in the cuff may contract as the patient’s temperature decreases. The seal should be examined occasionally to ensure that it is intact — hissing sounds are an indication of loss of patency. If the seal has been compromised during cooling, simply reinflating the cuff should reestablish it.
Additional Airway Access Methods
If the equipment or skilled personnel to perform a tracheotomy are unavailable, an airway may be achieved using other methods. The correct placement of an airway via “intubation” is more difficult, but still feasible.
Before attempting to place the airway, make certain that the patient’s mouth is free of any obstructions. Remove any loose dental work, like dentures or plates, and any pieces which might break off during intubation.
Intubation requires familiarity with the anatomical structure of the airway and good visualization skills. There are two passages leading from the mouth: the pharynx, which terminates near the esophagus (which leads to the stomach) and the larynx (which leads to the trachea).
An endotracheal intubation can be attempted, and it requires an endotracheal tube, a laryngoscope blade and handle, and a 20cc syringe. Correctly placing this type of airway requires skill and practice. It should only be attempted by transport team members who possess both.
The patient’s head must be hyperextended (flex the neck upward and pull the head backward) prior to attempting an endotracheal intubation. Hold the laryngoscope blade with the left hand, and insert it into the mouth. Do not use the teeth to lever the laryngoscope during intubation, as they may break. Dislodged teeth can fall into the airway and become an obstruction to air flow.
Gently pulling the handle should displace the tongue and reveal the glottic opening. The light at the tip of the laryngoscope blade should highlight the epiglottis and the vocal cords. Inserting the blade too far will obscure the glottis. If this happens, pull it back until the epiglottis is seen.
The first opening you are likely to see is the esophagus. The opening to the trachea is above the esophagus and is difficult to see. Once you can see the opening to the trachea, insert the endotracheal tube, working it in from the right side of the mouth. Use the laryngoscope blade to guide the tip.
Once the tube is positioned with the cuff beyond the vocal cords, the cuff can be inflated. Then, connect the oxygen hose and administer 100% oxygen. If oxygen is not yet available, use an Ambu bag to ventilate the patient.
Once oxygen flow has begun, it is important to listen to the lungs to make certain the endotracheal tube has been placed correctly. Watch the chest for the rising and falling and respiration. Listen to the chest, using a stethoscope, for the sounds of air entering and exiting the lungs. This is known as “auscultation”. Listen to each lung individually, as it is possible to pass the endotracheal tube into one of the bronchi, which would result in only one lung receiving oxygen. (If this happens, deflate the cuff and withdraw the tube slightly. Then, reinflate the cuff and auscultate again.)
Gurgling and abdominal distention are also signs that the endotracheal tube has been positioned improperly. If the esophagus has been intubated, it is necessary to remove the tube and try again. Administer a few ventilations to the patient using a mask and Ambu bag before beginning again.
Once the endotracheal tube is placed, secure the end to the patient with tape.
Esophageal Gastric Tube Airway
An alternative to endotracheal intubation is the use of an esophageal gastric tube airway (EGTA). An EGTA consists of an inflatable mask and an esophageal tube. The face mask has two ports: one for ventilation and one for the introduction of medications and stomach-suctioning tubes. The EGTA requires no special equipment to place, save the tube itself. The EGTA will be placed into the esophagus, its cuff inflated, and the mask secured to the patient’s face.
Position the patient’s head as you would for the endotracheal intubation. In order to insert the EGTA you must grasp the patient’s lower jaw and tongue between the thumb and forefinger of one hand, and lift the jaw slightly. With the EGTA in the other hand, insert the tube into the mouth. Push the tube forward. The EGTA will follow the natural curvature of the region and should slide directly into the esophagus. Advance the tube until the mask sits firmly on the patient’s face.
Once the EGTA is positioned, ventilate the patient (using the correct port) and check for signs that the tube is properly placed (see the discussion above). If you see the chest rise and hear breath sounds, inflate the cuff. If you do not, withdraw the EGTA and reposition the tube. As with the endotracheal intubation, you should administer a few ventilations to the patient using a mask and Ambu bag before beginning again. Tape the tube into place once it is correctly positioned.
The oxygen hose should be connected to the airway port as quickly as possible; ventilate with the Ambu bag until oxygen is available.
A suction tube may be passed through the esophageal port, should the patient vomit or if there is gastric bleeding. Any attempts to suction secretions should be limited to 15 seconds, to avoid lengthy interruptions in ventilation.
The esophageal gastric tube airway consists of an inflatable face mask and an esophageal tube. The transparent face mask has two ports: a lower port for insertion of an esophageal tube, and an upper port for ventilation. The inside of the mask is soft and pliable; it molds to the patient’s face and makes a tight seal, preventing air loss.
The proximal end of the esophageal tube has a one-way, nonrefluxing valve that blocks the esophagus. This valve prevents air from entering the stomach, thus reducing the risk of abdominal distention and aspiration. The distal end of the tube has an inflatable cuff which rests in the esophagus just below the tracheal bifurcation, preventing pressure on the non-cartilagenous back of the tracheal wall.
During ventilation, air is blown into the upper port of the mask, and, with the esophagus blocked, enters the trachea and lungs. (See left illustration below.)
A gastric tube can be used to suction stomach contents before extubation. It is inserted through the masks lower port into the esophageal tube, then through a small hole in the end of the tube.
The esophageal obdurator airway consists of an adjustable, inflatable face mask with a single port, attached by a snap lock to a blind esophageal tube.
When properly inflated, the transparent mask prevents air from escaping through the nose and mouth. (See right illustration below.)
The esophageal tube has sixteen holes at its proximal end through which air or oxygen, blown into the port of the mask, is transferred to the trachea. The tubes distal end is closed and circled by an inflatable cuff. When the cuff is inflated, it occludes the esophagus, preventing air from entering the stomach and acting as a barrier against vomitus and involuntary aspiration.
The Oropharyngeal Airway
An oropharyngeal airway is very similar to a esophageal gastric tube airway. The significant difference is that there is only one port in the mask. Instead of individual ports for the tube and the airway, the oropharyngeal airway has holes in the esophageal tube.
The process for insertion is identical to that for the EGTA. As with all airways, auscultate the chest to make certain that you have placed the airway correctly before you secure it to the patient.
The FEF End-Tidal CO2 Detector
An end-tidal CO2 detector measures the carbon dioxide concentration of exhaled air during resuscitative measures. It is a simple and inexpensive way to evaluate the effectiveness of CPS. The detector uses a responsive chemical membrane that indicates the carbon dioxide concentrations through color changes.
After the detector is removed from its mylar package, it must be checked to verify that it hasn’t become damaged during transport. Match the initial color of the membrane to the purple color on the dome (labeled “check”). If the colors are not identical, do not use the detector.
If it checks out, remove the end caps and place the detector between the airway and the oxygen hose before CPS is started.
Once the patient has exhaled six times, the membrane color may be compared to the dome labels. The color of the membrane (ranging from purple (room air at 0.03%) to yellow (4% or greater) will change with the ventilations. Readings of 2% or better are good for transport patients. (5% is normal.)
In some cases, the detector may register no color changes. It will not work if it’s wet! In patients with endotracheal airways or EGTAs in place, a lack of color changes could indicate that the patient was improperly intubated. Lowered patient temperatures can also affect the detector’s operation. According to the manufacturer, the end-tidal CO2 detector has a useful life of about two hours.
Administering CPS to a patient is another area of a transport where the transport team member risks infection from exposure to the patient’s body fluids (including blood, sputum, mucous, and vomitus). Infectious diseases pose a serious health risk for transport team members if suitable precautions are not taken during the stabilization. Basic precautions, like those below, are very effective and easily implemented, and indeed, must be implemented by transport team members.
Any transport team member coming into contact with a patient’s bodily fluids must wear latex exam gloves. Face masks and hair covers are also required. For individuals handling sharp objects, like needles or scalpels, puncture-resistant nitrile gloves should be donned underneath the exam gloves. For the surgeon and perfusionist, or anyone assisting them, face shields or goggles are also required to protect the eyes. Water-resistant suits are also recommended.
Caution: Wear gloves, face masks, and hair covers! Anyone placing or managing an airway will invariably come into contact with the patient’s body fluids. Care must be taken to avoid accidental infection.
An airway should be placed as quickly as possible. Ventilation should always occur in conjunction with the restoration of circulation.
Airway management notes should be recorded. When oxygen flow is reestablished; when medications are administered through the gastric tube; and when and where secretions are suctioned is all important, and should be recorded by the transport team member who has been assigned scribe duties. But it is incumbent upon the individual managing the air-way placement and care to inform the scribe when important events occur.