chapter 22 Armamentarium
In direct IV administration, a tourniquet is placed on the patient’s arm, engorging the veins, the injection site is prepared, and the needle of the syringe containing the drug(s) is placed into the lumen of the vein, in effect doing the venipuncture with the drug-containing syringe. After ensuring that the needle tip lies within the lumen of the vein (aspiration of blood back into the syringe), the dentist or assistant removes the tourniquet, and the drug is slowly administered into the vein. Following drug administration, the needle is removed from the vein, pressure is applied to the site to stop bleeding, and the planned treatment begun. No access to the vein is maintained during the procedure (Figure 22-1).
When the needle is maintained in the vein without an infusion, the tourniquet is placed, the veins are engorged, and the tissues are prepared in the usual manner. A winged infusion set or a hollow metal needle is used for venipuncture. Following successful venipuncture, the tourniquet is removed, and the syringe (without a needle attached) is connected to the needle that has been left in the vein and taped into place. After the drug is titrated to effect, the syringe is detached from the needle, and a second syringe containing a solution such as sterile water for injection is attached to the needle. The dental procedure is begun, with the dentist or assistant periodically flushing the needle with 1 ml of solution to keep the vein patent (Figure 22-2).
With a continuous IV infusion, an indwelling needle or catheter is attached to a length of tubing that in turn is connected to a bag of IV infusate. The same venipuncture procedure is carried out that was described for the first two techniques. Following removal of the tourniquet, the flow of IV solution is started, and the needle or catheter is secured. The IV drugs are administered through an injection port on the tubing, and the drug syringe is then removed. The rate of the IV infusion is adjusted to maintain a slow flow that will prevent needle occlusion during the dental procedure, which is then begun (Figure 22-3).
The first technique, direct IV administration, in which the syringe is removed from the vein after drug administration, cannot be recommended for routine use in IV sedation. The only reasons for considering use of this technique, in my opinion, are:
Why do I believe this technique should not be used? As is evident in later chapters and during training in IV sedation, the most exacting part of learning to use IV sedation is becoming technically proficient at venipuncture. Although not a hard technique to master, venipuncture can be difficult on some occasions in even the most experienced of hands. Why then, if placing a needle into the vein is the most difficult task in IV sedation, should the needle be removed from the patient’s vein after a successful venipuncture? Adherents of the needle-removal technique claim that the patient is bothered by the needle remaining in the vein and that the presence of the needle in the vein throughout the procedure reminds the patient of a hospital. However, once the needle is placed into a vein, the patient has little, if any, awareness of its presence, whether it is in for 1 minute or several hours. In response to the belief about the hospital setting, I can only state that the presence of a needle within the vein throughout the procedure is routine in hospital practice simply because it increases safety. Patients will accept as normal most practices within the dental office. A valid argument in favor of the needle-removal technique is that removal of the needle from the vein makes it difficult for additional drugs to be administered following the initial titration, reducing the chance of a drug overdose.
Removal of the needle from the vein is illogical because, on occasion, additional IV sedative drugs may be required later in the procedure or a reversal agent may be needed later during the treatment period. Drugs, such as flumazenil, naloxone, or physostigmine, may be required during or at the end of the IV sedation procedure. In both of these situations, a venipuncture would need to be redone. Because venipuncture is the only part of the IV sedation procedure that might be considered difficult, is it not logical to leave the needle in situ during the entire procedure? In addition, should a situation arise in which the patient’s blood pressure decrease significantly, superficial veins will become more difficult to visualize and cannulate.
The second technique, in which the needle remains in the vein throughout the procedure, its patency maintained by periodic flushing with some solution, is an improvement on the previous technique. The only drawback to this technique is that periodic flushing of the needle is required to prevent clotting of the lumen from occurring. During a busy dental procedure, it is not uncommon for the dentist and the assistant to become deeply engrossed in the oral cavity and to neglect to flush the needle, in which case the lumen of the needle becomes clotted with blood and a vein must be recannulated.
Continuous IV infusion is the most highly recommended technique in all situations in which a patent vein is to be maintained for a period of time exceeding but a few minutes. In this technique, patency of the needle and vein are maintained by the constant infusion of IV solution from the bag into the needle and the patient’s vein. The only drawback to this procedure is the possibility that (1) the infusate might become contaminated (an extremely unlikely occurrence) and (2) the drip rate might be too rapid, causing the bag of solution to be emptied during the procedure.
Readministration of sedative or administration of emergency drugs is easily carried out by simply inserting the syringe needle into the injection site on the IV tubing. The ease of maintaining a patent vein and the increased safety afforded the patient by the continuous IV infusion are the primary reasons for considering this technique as the ideal for IV drug administration. The equipment and techniques discussed in this section relate to continuous IV infusion.
A number of fluids are available for IV therapy. Although the type of solution chosen is of potential significance in the hospitalized patient receiving prolonged IV therapy, for a short-duration IV procedure (less than 1 hour to several hours’ duration) on a relatively healthy patient (ASA 1 or 2), the choice of infusate becomes academic. Solutions available for IV administration include the following:
|Sterile water for injection||SW|
|5% dextrose in water||D5W|
|Sodium chloride injection||NS|
In the ambulatory American Society of Anesthesiologists (ASA) 1, 2, or 3 patient considered as a candidate for IV moderate sedation on an outpatient basis, there will be no contraindication to the use of any of these solutions. The question of whether a patient with insulin-dependent diabetes mellitus (type 1, or IDDM) should receive 5% dextrose in water often arises—will this solution elevate the patient’s blood sugar level?
The answer is that a 5% dextrose and water solution is not contraindicated in the diabetic patient. First, the concentration of dextrose (5%) is not great enough to produce any significant change in the blood sugar level of this patient.1 Second, as stressed in Chapter 26, the patient receiving IV moderate sedation will be requested to fast (be NPO) for approximately 4 hours before the planned procedure. The patient arrives at the dental office with a decreased blood sugar level, perhaps not quite hypoglycemic but definitely not hyperglycemic. The addition of approximately 250 to 500 ml of 5% dextrose and water will produce a slight elevation in blood sugar level, a desirable effect at this time. It must be remembered that when a person with diabetes becomes clinically hypoglycemic, treatment of choice is the administration of 50% dextrose, a solution 10 times that which is infused during IV sedation.
IV fluids are available in a variety of sizes. Most commonly used sizes include 1000, 500, and 250 ml. The 1000-ml (1-L [liter]) size is common in the hospital setting when a patient is receiving long-term IV therapy. The patient usually receives 3 L of IV fluid daily. Under a general anesthetic, during which time the patient must be kept hydrated throughout the surgery, 1-L bags are also commonly used. Use of the 1-L bag for dental outpatient procedures is not the most highly recommended, although there is no significant reason why it should not be used. However, for the typical IV procedure in the dental office, the 1-L bag is simply too large. For example, during a 1-hour procedure, the typical patient may receive 125 to 200 ml of infusion fluid. At the conclusion of the procedure, the infusion bag represents one of the three items in the IV armamentarium that must be discarded. It is a single-use item, and must never be reused despite the fact that, in this example, approximately 800 ml of infusate remains unused.
The 250-ml or 500-ml bags of IV fluid represent the most nearly ideal sizes for the typical 1- to 4-hour dental IV moderate sedation procedure. With proper management of the flow rate (as discussed in Chapter 26), a 250-ml or 500-ml bag can be made to last for 3 to 4 hours.
The solution found within the IV bag is sterile. However, problems with contaminated fluids have developed in the past.2 Care must be exercised by the user of such fluids to try to ensure their continued sterility. Administration of contaminated fluids directly into the cardiovascular system of the patient can produce bacteremia or septicemia and has led to deaths and significant morbidity.3