Before administering any form of medication, anesthesia providers must assess their patients, weigh the required sedation against the risks of intraoperative complications and establish the appropriate peripheral intravenous access. Here's how providers make that important first connection safely and effectively.

Fluid and infusion therapy
One major challenge for anesthesia providers is predicting how much fluid flow the patient will need during a case. In general, we replace deficits to maintain normal blood volume and oxygen delivery. We can make a few assumptions based on the co-morbidities of the patient and the type of procedure to be performed, but all patients are at risk for respiratory depression and hemodynamic instability associated with vasodilation and loss of fluid. If complications arise, the patient's fluid needs could change dramatically. For example, a low-risk, routine laparoscopy could quickly become complicated if a trochar injury causes severe hemorrhaging of a major blood vessel.

The needed fluid flow determines the bore of the catheter and tubing used to start IVs. The more fluid needed, the larger the bore required. Most short outpatient procedures need just one IV with maintenance fluid or heplock. However, longer procedures — and those with significant blood loss — often require one line for drug infusions and another for fluid boluses and replacement. Having two IV lines or a low prime-volume extension for the infusion line can decrease the risk of unintentional drug bolus associated with fluid boluses. To prevent disconnection, Luer locks are superior to simple friction-tip connections. For maximum safety, we use the three-step process for connection: insert, wiggle and screw.

Anesthesia providers generally use low-viscosity fluid, a large-bore catheter and short tubing, raising the IV pole to lift the bag above the heart if they want more fluid flow. The bag's elevation determines the hydrostatic pressure that drives the fluid flow in the absence of an infusion pump.

Therefore, a functional IV pole must have a sturdy base with wheels that roll and adjustable height capability (low altitude for changing bags and high altitude for good flow). Infusion pumps can be mounted on the IV pole below the height adjustment knob.

The flow rate (ml/hr) can be related to the drops per minute. Drop sizes vary, but generally 1ml = 10 drops = 15 macrodrops = 60 microdrops.

Choosing a vein
In most outpatient cases, the upper limbs are best suited for inserting catheters because they're closest to the anesthesia provider. Although antecubital veins tend to be larger than hand or forearm veins, there's risk of infiltration if fluids are infused distal to a "blown" proximal vein. In general, we start distally and work proximally if unsuccessful with insertion.

The patient's lower limbs are sometimes an option; however, convenient access to the legs may require longer extension tubing. When DVT prophylaxis compression boots are used, the saphenous veins at the ankle may not be accessible. Certain patient positions also limit the choice of insertion sites. For example, the lateral-prone positions used for endoscopy cases increase the risk of catheter kinking in the antecubital regions.

When choosing access sites, we look for a distended vein on the arm or hand, such as the metacarpal vein between the fourth and fifth fingers. The size and quality of veins can vary greatly among patients, depending on their age and health. For example, dehydrated patients, such as those who have had bowel prep, may have shrunken veins. Older patients can have more exposed veins because they have less subcutaneous tissue surrounding them. Their tissue, however, is more frail and friable.

IV drug users and patients who have undergone chemotherapy often have collapsed, thrombosed, phlebotic or scarred veins that can be a challenge to access. It may be more difficult to find a suitable hand or arm vein in these patients, and providers sometimes use ultrasound guidance to hunt for deep or central veins.

Veins can be inflated by using gravity, applying a tourniquet, stroking the skin or flicking a finger on planned cannulation sites. I seem to have better results with gentle stroking, but many anesthesia providers prefer vigorous flicking. It's a matter of personal preference.

Prepping the skin
To reduce risk of infection and patient pain, the cannulation site should be prepped. For peripheral IV lines, I use alcohol. For arterial lines, I use alcohol followed by chlorhexidine. For central lines, which stay in the patient longer, I prefer to use a combination of pigmented betadine as a pre-prep and then colorless chlorhexidine to remove the colored betadine. Studies show that chlorhexidine works better as an antiseptic than betadine. However, betadine's coloring highlights the prep area, helping to avoid the common mistake of not prepping a large enough area.

Local anesthesia makes the initial cannulation less painful for the patient and tends to dilate the veins. I inject 1% or 2% lidocaine with or without sodium bicarbonate using a 25-gauge needle. If the lidocaine is injected next to the vein rather than on top of it, there is less chance of unintentional vein injury or swelling, which interferes with palpation.

Some anesthesia providers use a jet injection gun for children and other patients who are not comfortable with needles. Likewise, EMLA cream — a topical emulsion of lidocaine and prilocaine — can be applied on the injection site. One drawback with EMLA is that the cream should be applied at least one hour before the cannulation, making it unsuitable for most outpatient settings. If a patient is extremely uncomfortable with needles, I sometimes use inhaled anesthetics to sedate the patient and dilate the veins. Although commonly used in children, inhalational inductions present a set of challenges that are best avoided in most cases.

Choose your method
The direct cannulation technique (also known as the catheter-over-needle technique) is the most commonly used in peripheral venous access. In patients with difficult veins, the guidewire technique can be used with ultrasound guidance to find larger, deeper veins. The through-and-through technique can be used to salvage an unintentional back wall perforation during IV insertion. Here are detailed directives for each method, presented for your front-line staff to follow.

• Direct cannulation technique. To begin, extend the patient's arm on an armboard with the palm of the hand facing down. Hold the catheter with the needle extended in your dominant hand with thumb and index finger on the catheter and your palm down. This allows the catheter to be lowered to the skin without your hand acting as a wedge.

With the other hand, use the index finger to apply pressure on the vein downstream from the injection site. This obstruction slows the blood flow returning to the heart and causes the vein to inflate. Use the thumb to apply traction on the skin and slight pressure on the side of the vein in order to hold it in place while maintaining venous inflow.

Now, pierce the skin and the vein with the bevel of the needle facing up. In most peripheral IV insertions, maintain a 10- to 30-degree angle to the skin and make sure that the end of the needle faces the oncoming blood in the vein.

Once you see a flash of blood in the catheter, push the catheter into the vein over the needle, decreasing your angle to the skin. When the catheter is in, use the thumb and index finger of your non-dominant hand to stabilize the catheter. Remove the needle with the dominant hand and connect the extension to the catheter. Verify fluid flow by opening the stopcocks and clamps.

A common cause of unsuccessful catheter insertion after seeing a blood return is the premature release of skin tension prior to the advancement of the catheter. In this case, elastic recoil pulls the vein off of the catheter, which tends to bend and buckle when it's pushed into the vessel wall exterior.

• Through-and-through technique. The needle may occasionally and unintentionally penetrate the back wall of the vein. In these cases, you can use the through-and-through technique, which is more commonly used during arterial line insertion with guidewire assistance.

Before declaring the access attempt unsuccessful, gradually pull back the needle and catheter to maximize blood return. Then quickly insert the catheter into the vein with the tip above the point of perforation. If the catheter slides into the vein and is advanced beyond the point of penetration, the venous access can be salvaged. Watch for the infiltration of fluid in the surrounding tissue. If you see blood return in the tubing, you can assume the IV is in place. The IV may still be in place if you don't see blood as long as good fluid flow is observed without signs of soft-tissue swelling.

• Guidewire (Seldinger) technique. When direct cannulation of a superficial vein is not successful, the guidewire technique can be used to access deep peripheral or central veins. First, insert a needle or angiocath into the vein, using ultrasound guidance if needed. A flash of blood confirms that you've entered the vein. Then slide a guidewire through the needle while holding back slightly on the needle. When the wire is in the vein beyond the end of the needle, remove the needle. If you plan to insert a larger diameter catheter, make a small incision away from the guidewire. Make sure that the incision is continuous (meaning there is no "skin bridge"). Now the catheter can be placed over the guidewire and inserted into the vein. Remove the guidewire and attach the IV extension.

Plan for success
IV therapy is an integral part of nearly every surgical procedure and requires monitoring from pre-op through the PACU. With proper planning and attention to detail, anesthesia providers can protect patients during the procedure and help the surgical team achieve better outcomes.