chapter 27 Intravenous Sedation: Complications
A number of complications may occur when the intravenous (IV) route of drug administration is used. Fortunately, most are relatively benign and easily managed. Others, however, are more significant and can lead to serious morbidity or death.
The complications associated with IV drug administration are divided into four groups: (1) those associated with venipuncture, (2) localized complications related to drug administration, (3) general drug-related problems, and (4) drug-specific complications. These are outlined in Box 27-1.
Complications Associated With IV Drug Administration
One of the most common and vexing complications of venipuncture and IV drug administration is the nonrunning or very slowly running IV infusion. Once venipuncture has been successfully completed (e.g., blood returning into the tubing), the tourniquet is removed and the IV drip started. During drug administration, the drip rate should be increased; at other times, the rate should be slowed. The causes of a nonrunning or slowly running IV infusion follow.
Gravity forces the IV infusate from the bag down into the patient. The greater the difference in height between the bag and the patient’s heart is, the more rapid the flow of solution can be. A simple experiment demonstrates this: The IV bag is held high above the patient’s heart level, and the rate of flow is checked. With the rate-adjusting knob opened fully, the drip should be rapid. As the bag is gradually lowered toward the level of the patient’s heart, the rate of flow of the drip decreases until, when held at the patient’s heart level, the flow ceases entirely. When the bag is lowered below the level of the patient’s heart, blood returns into the tubing (Figure 27-1).
Figure 27-1 A, Bag of IV solution held above level of patient’s heart (vein) allows fluid to run into patient. B, Lowering bag of IV solution below level of patient’s heart (vein) allows blood to return into tubing from patient.
This is a situation that might arise when the dental chair is placed low to the floor at the start of a procedure and is elevated at a later time. Increasing the distance between the bag of IV infusion solution and the patient’s heart will correct the situation.
It was recommended that the bevel of the needle be facing upward during venipuncture to allow entry through the skin to be as atraumatic as possible. Following entry into the skin, the needle is advanced into the vein with blood returning into the tubing a sign of a successful venipuncture. At this point, the tourniquet is removed and the infusion started. If the IV drip rate that is flowing rapidly until the scalp vein or metal needle is taped into position is noted to slow considerably, it is quite possible that in taping the needle into position, the bevel of the needle was lifted and now lies against the wall of the vein. This will restrict or prevent the flow of fluid from the IV drip into the patient.
To determine whether this is the cause of a slow or nonrunning drip, the needle is carefully untaped and the wings of the butterfly needle gently lifted. This lowers the bevel of the needle off the wall of the vein. If the drip rate increases, the protective cap from the scalp vein needle (Figure 27-2) or a 2 × 2-inch gauze square is carefully placed under the wings of the needle and the needle retaped.
This is not likely to occur when an indwelling catheter is used for venipuncture because there is no bevel on the catheter. However, when a catheter is positioned in either the dorsum of the hand or antecubital fossa, it is possible for the tip of the catheter to lie in a bend in the vein, creating a slow flow of IV solution (Figure 27-3). Determine this by straightening the patient’s wrist or elbow and looking for an increase in the rate of flow of the IV drip. This may be minimized by preventing the patient from bending the joint through the use of an elbow immobilizer or wrist board.
An embarrassing but not uncommon cause of a nonrunning IV drip following successful venipuncture may simply be that the tourniquet has been left on the patient because it has become hidden by a sleeve of a garment that has inched down. Following the return of blood into the IV tubing, the dentist or assistant opens up the control knob to start the IV drip. It is noted that the drip is not flowing and that blood does not leave the IV tubing as normally occurs. It is usually noted that more blood appears to be entering the IV tubing (as it is forced from the vein into the tubing) (Figure 27-4). Once excessive blood is noticed in the tubing, simple removal of the tourniquet will alleviate this embarrassing situation.
Following successful entry into the vein, the metal needle somehow becomes dislodged while being secured. The dentist or assistant, unaware of this, opens the rate knob, but little or no solution flows. If no solution is flowing, the three causes of nonrunning IVs previously discussed should be considered. If the drip rate is extremely slow and cannot be increased, one should first look at the site where the needle tip is located beneath the patient’s skin. If the needle tip has left the vein and fluid is still flowing, a small colorless swelling will develop at this site. This is termed an infiltration.
In all cases in which an IV drip that was previously running well has either slowed or stopped entirely, the needle should not be removed from the vein until it has been determined definitively that the needle tip is no longer within the vein. The following procedure should be followed to determine the cause of the slow or nonrunning IV drip:
Venospasm is a protective mechanism in which the vein wall reacts to stimulation from the needle by going into spasm. As the needle approaches, the vein appears to disappear or “collapse.” Venospasm is occasionally accompanied by a burning sensation in the immediate area. This burning sensation ends without treatment as venospasm resolves. Venospasm may occur before or after entry of the needle into the vein, securing of the catheter or needle, or starting of the IV drip.
The needle should not be removed from the site because the vein has not been entered or damaged. The needle is pulled back slightly (1 to 2 mm), and heat applied to the site in an attempt to dilate the vessel. If and when the vein reappears, the venipuncture attempt is continued.
A sensation of burning during venipuncture and IV drug administration is associated with several other complications and with one cause that is not a complication. The IV administration of diazepam is occasionally associated with the sensation of warmth or burning; however, this sensation travels up the patient’s arm (centrally) as the drug travels through the veins. Intraarterial (IA) injection of a drug will produce a burning sensation or pain traveling down (peripherally) the arm toward the fingers. Extravascular injection of a drug produces a burning sensation at the site of injection that remains at the site of administration. The injection of meperidine may cause the release of histamine and a burning or itching sensation along the path of the vein. Venospasm occurs more frequently in apprehensive patients, presumably as a result of their higher levels of circulating catecholamines (predisposing them to peripheral vasoconstriction).
Hematoma is the most common complication associated with venipuncture. It represents the extravasation of blood into interstitial spaces surrounding a blood vessel. The presence of blood in this space leads to localized swelling and discoloration.
When venipuncture is successful, the needle itself acts as an obturator, sealing the hole in the vein wall made during entry of the needle. In some patients, particularly older patients in whom vein walls are less elastic, leakage of blood around the needle may occur during the IV procedure even though the needle tip still lies within the lumen of the vein.
Hematoma may occur at two distinct times during the IV procedure. First, it may develop during attempted venipuncture if the vessel wall is damaged. This is not always preventable. The second cause of hematoma is usually preventable. In this situation, the IV procedure has been completed and the catheter or needle removed from the vein. Improper application of pressure or inadequate duration of pressure at the venipuncture site can result in a hematoma.
It is not always possible to prevent hematoma during venipuncture, although careful adherence to recommended technique minimizes its likelihood. Hematoma developing after the procedure may be prevented by application of firm pressure for a minimum of 5 to 6 minutes. The commonly used technique of placing gauze over the venipuncture site in the antecubital fossa and having the patient flex his or her arm (illustrated in Figure 27-5) does not always provide pressure adequate to prevent hematoma.
Hematoma is a painless, bluish discoloration, frequently with swelling, noted under the skin at the site of needle puncture. It develops during attempted venipuncture or at the conclusion of the IV procedure on removal of the catheter or needle.
When hematoma develops during attempted venipuncture, swelling increases rapidly because the tourniquet is still on the patient’s arm (significantly increasing blood pressure within the vein). Immediate management consists of the following:
Subsequent management of either form of hematoma can best be described as “tincture of time.” It will require approximately 10 to 14 days for the subcutaneous blood to be resorbed by the body. Nothing can be done to speed this process. Should the patient experience discomfort or soreness (more likely if the hematoma is located in a joint [wrist, antecubital fossa]), he or she can be advised to use moist heat on the area for 20 minutes every hour. Heat should not be used within the first 4 hours after the onset of the hematoma because it acts as a vasodilator and might induce further bleeding.
Infiltration is similar to a hematoma in that a fluid is deposited into the tissues surrounding the blood vessel. A hematoma is the infiltration of blood outside of a blood vessel. Extravascular injection of a drug is the infiltration of drug outside of the blood vessel. Infiltration is defined as a painless, colorless swelling that develops at the site of the needle (cannula) tip when the IV infusion is started.
In this situation, we are discussing the deposition of the IV infusate into the tissues surrounding the blood vessel. The infiltration discussed here differs from hematoma in that the swelling that develops does not occur until the IV drip is turned on, whereas the hematoma occurs as soon as the vein wall is damaged.
In the continuous IV infusion technique, when infiltration does occur, it only consists of a solution, such as 5% dextrose and water or normal saline, that does not produce any degree of tissue irritation or damage. In contrast, in IV techniques in which the drug is injected directly into a blood vessel, it is much more likely that the drug will produce tissue damage and/or a delayed onset of sedation if deposited outside the blood vessel.
Infiltration can be prevented by careful venipuncture technique and by not starting the IV drip or injecting drugs until it has been confirmed that the needle tip or catheter still lies within the lumen of the vein. Checking for this is quite easy. The rubber flash bulb on the IV tubing may be squeezed with blood returning into the tubing when the pressure is released, or the IV bag may be held below the level of the patient’s heart (Figure 27-6).
Movement of the metal needle either while it is being secured or through movement of the patient’s arm during the sedation procedure may cause the rigid metal needle to perforate the vein wall producing an infiltration or hematoma. Common causes of a needle becoming dislodged are (1) attempting to thread (insert) a rigid metal needle too far into the vein and (2) carelessness during taping of the needle. Infiltration is much less likely to occur when a plastic catheter is used for venipuncture.
Infiltration is a painless, colorless swelling that occurs around the tip of the needle when the IV drip is started. The tissue around the needle tip is raised, and the skin at this site feels cooler than skin at a distance from this site. This is because the infusate is at room temperature (22° C/72° F), not body temperature.
The IV infusion is stopped immediately and the needle removed. Sterile gauze is placed at the site and pressure applied for 5 to 6 minutes. Pressure will stop any bleeding and also spread out any fluid within the tissue. The fluid will be resorbed into the cardiovascular system. Little or no residual soreness will be noted.
Localized venous complications can develop after IV sedation procedures. Many factors are responsible for their development, and there are a number of different clinical expressions that venous complications take. Trauma to the vein wall produced by the needle or cannula is a possible cause of this problem. In the dental outpatient environment, the most likely cause of venous complications is chemical irritation of the vein wall produced by the drug administered, usually diazepam. Localized venous complications are discussed later in this chapter (see Local Complications of Drug Administration).
Air embolism is a possible, although extremely unlikely, complication of IV sedation. It is best prevented by using a technique that is free of air: eliminating air bubbles from syringes and from the IV tubing before the procedure and periodically observing the IV infusion bag to prevent it from emptying.
In the highly likely event that one or more small bubbles of air enter into the venous circulation, they will be absorbed by the blood quite rapidly with no clinical sequelae. It is not always possible for all air bubbles to be removed from the IV tubing or syringes, and it is quite probable that small bubbles may enter into the venous circulation of the patient. The patient, noticing the air bubble moving slowly down the IV tubing toward his or her arm, may become quite anxious, believing (from television or movies) that as little as one bubble of air is lethal. Fortunately, this is not so. A rule of thumb in a hospital environment is that a patient can tolerate up to 1 ml/kg of body weight of air in the peripheral venous circulation without adverse effect.1
The typical IV administration set can hold approximately 13 ml of air.2 Because 10 drops of solution (or air) equals 1 ml (adult infusion set), the chances of introducing large volumes of air into the patient’s circulation are extraordinarily low. A 50-kg (110-lb) patient can tolerate 50 ml of air. This is equivalent to 500 to 750 drops of air from an adult IV administration set (10 or 15 drops/ml).
In small children, air embolism is a more significant problem because their bodies cannot tolerate large volumes of air. A 13 kg (30-lb) child is at greater risk of this complication than is a larger patient.
Should air embolism occur, management is based on the attempt to prevent this air from entering into the cerebral and pulmonary circulations. This is accomplished by positioning the patient in the dental chair lying on his or her left side (preventing entry into the pulmonary circulation) and in a head-down position (preventing entry into the cerebral circulation).
Overhydration of the patient is another not very common problem associated with IV procedures in the dental office. The two most likely candidates for overhydration, however, are children and patients with heart failure. Signs of overhydration include pulmonary edema, respiratory distress, and an increase in heart rate and blood pressure. These are also the signs and symptoms occasionally noted in a patient with acute pulmonary edema.
A rule of thumb for replacement of fluid in a patient is that the initial dose of IV solution administered is equal to 1.5 times the number of hours a patient has gone without food times the patient’s weight in kilograms.3 This is the volume of fluid in milliliters required to replace the fluid deficit created by the patient’s taking nothing by mouth (NPO) before the procedure. If a patient has been NPO for 6 hours before coming to the office, the initial volume of IV solution administered is nine times the patient’s body weight in kilograms. The maintenance dose of IV solution is 3 ml/kg. The problem of underhydration is not significant in the usual outpatient environment.
When IV drugs are administered to pediatric patients, it is recommended that a pediatric infusion set be used. This set, which permits 60 drops/ml instead of the usual 10 or 15, allows for the more precise administration of fluids to the younger, smaller patient or to the adult with more serious heart failure. In many instances, these two classes of patients are not candidates for elective IV moderate sedation in the outpatient dental setting.
Pain associated with extravascular drug administration occurs at the site of the needle tip under the skin and tends to remain localized to that area. This distinguishes extravascular injection from IA and IV injections, where a burning sensation radiates either peripherally or centrally. The patient will complain of discomfort as the drug is injected in all three situations.
A potentially greater problem (depending upon the drug and the dosage) is delayed absorption of the drug into the cardiovascular system, especially if larger volumes have been deposited into the tissues. In essence, the drug has been administered subcutaneously instead of intravenously. Uptake of the drug is slow, with an onset of clinical activity occurring anywhere from about 10 to 30 minutes later.
A third problem that might arise is damage to the tissues into which the drug has been deposited. Some drugs used intravenously are potentially irritating to tissues. This is especially true for diazepam and, when it was more commonly used, pentobarbital. The initial response of the tissues is arteriolar and capillary constriction, which decrease the blood supply to the area. If vascular constriction is prolonged or if the chemical is irritating enough, necrosis and sloughing of tissue may occur.
There are two causes of extravascular drug administration. The first is the needle or cannula slipping out of the vein. This usually leads to an immediate formation of a hematoma that is quickly recognized. No drug is usually injected at this time. The second cause is the needle entering the vein and then being pushed through the other side as the dentist attempts to advance it farther into the vein. Blood will have returned into the tubing as the needle entered the vein originally, thereby giving the (false) impression that the needle or catheter tip remains in the vein. However, with removal of the tourniquet, it is unlikely that the blood will leave the tubing, as normally occurs, because the tip of the needle no longer lies in the vein but in subcutaneous tissue. On very rare occasions, the blood will leave the IV tubing and reenter the patient allowing the IV infusion to run even though the needle tip is no longer in the vein. This will occur when the bag of IV solution is quite high above the patient’s heart or if the patient’s skin and underlying soft tissues are not “firm,” allowing gravity to force the solution into the tissues. The latter is seen more often in older, more frail patients.
Use of a continuous IV drip technique really minimizes the possibility of extravascular injection of the drug because an infiltration of infusate produces an immediate swelling. Second, before administration of any drug, it is recommended that patency of the vein be reconfirmed by squeezing the flash bulb or holding the IV bag below the level of the patient’s heart. Despite these precautions, a subtle movement of a patient’s wrist or elbow just after this check but just before drug administration can produce this complication if a rigid metal needle is used. The administration of a 0.2-ml test dose of a drug is a means of detecting this complication before a larger, potentially more damaging bolus of drug is deposited.
As the irritating drug, especially diazepam, is injected extravascularly, the patient will complain of an intense pain occurring at the site of the needle tip, but does not migrate up or down the arm. In addition, as an increasing volume of drug is injected, the tissue at the site of the needle tip will become raised as the solution is forced into the subcutaneous tissues. If the chemical is irritating, the skin overlying the raised tissue will become ischemic as blood vessels in the area constrict in response to the irritation. A second possible reaction is for the tissues to become erythematous as a result of inflammation.
The two major problems to be managed are possible delayed absorption of the drug and its effect on the patient and potential damage to the tissues at the site of deposition. Management initially consists of removing the needle and applyin/>