"Intravenous" means that the drug is put into a vein. An extremely thin needle is put into a vein close to the surface of the skin in either the arm or the back of your hand. This needle is wrapped up with a soft plastic tube. The needle makes the entry into the vein, then is slid out leaving the soft plastic tube in place. The drugs are put in through that tube (which is correctly referred to as an "indwelling catheter", but more commonly known by the tradename of Venflon). The tube stays in place throughout the procedure.

The venflon to the right is a pinkie, which is one size bigger than the blue one that's usually used for IV sedation in dentistry.

Throughout the procedure, your pulse and oxygen levels are measured using a "pulse oximeter". This gadget clips onto a finger or an earlobe and measures pulse and oxygen saturation. It gives a useful early warning sign if you're getting dangerously low on oxygen, although if your dentist and the nurses are paying attention they should see it before the machine does =). The warning signs are unresponsiveness and slow breathing. Blood pressure before and after the procedure should be checked with a blood pressure measuring machine (a tongue-twister called "sphygmomanometer", which for obvious reasons is referred to as "sphyg").

The most commonly used drugs for IV sedation are benzodiazepines, or "benzos" for short. These are anti-anxiety sedative drugs. In the UK, a benzodiazepine is almost always the only drug used for IV sedation (although I have heard of fentanyl being used as well). However, the situation is different in the US, for reasons which I'll try and outline below. First of all, regardless of location, what are the drugs which CAN be used for IV sedation?

1) Anti-anxiety sedatives ("benzos"): Midazolam and Diazepam

Mostly the drug used for IV sedation is a short acting benzodiazepine, or "benzo" for short. This is an anti-anxiety sedative - see the Oral Sedation page for more info on benzos in general. IV administered benzos have 3 main effects: they reduce anxiety/relax you, they make you sleepy, and they produce partial or total amnesia (i. e. make you forget what happened during some or, less frequently, all of the procedure). Total amnesia is more common with midazolam compared to diazepam (see below).

By far the most commonly used drug for IV sedation is Midazolam (tradenames: Versed in the US, Hypnovel or Dormicum in the UK), but occasionally Diazepam (tradename: Valium) can be used.

Midazolam is the first choice because of its relatively short duration of action (meaning that it'll be out of your system faster). Valium is (marginally) cheaper but longer acting and a bit "harder" on the veins, so you may feel a burning sensation on your arm/hand when the drug first enters. Local anaesthetic solution can be mixed in with Diazepam to make things more comfortable. The latest IV Diazepam is an emulsion which is claimed to be easier on the veins.

The drug is put into the vein at the rate of 1mg per minute for Diazepam or 1 mg every 2 minutes (followed by an extra 2 minutes to evaluate the effect) for Midazolam (because Midazolam is stronger in terms of the dose needed to achieve sedation). Because there are differences between individuals in how much of the drug you need to be sedated, your response to the drug is monitored. Once the desired level of sedation is achieved, the drug is stopped.

The Venflon is left in place during the procedure so that the sedation can either be topped up or so that the reversal agent for benzos (Flumazenil) can be put in in the unlikely event of an emergency.

2) Barbiturates

Barbiturates (sleep-inducing drugs) are not used for conscious sedation in the UK, and have gone out of fashion in the US. The only barbiturate which is still occasionally used is called Pentobarbital Sodium (tradename: Nembutal).

In the absence of a trained anesthesiologist, barbiturates are pretty dangerous to use, for a number of reasons: it's very easy to have the patient slip into general anaesthesia by mistake, where breathing and heart rate are dangerously lowered and coma and death can follow. Worse still, unlike for benzos, there's no reversal agent. Barbiturates have only one advantage over benzos, and that is that they can be used to provide more than 1 1/2 hours of conscious sedation (which is about the max with benzos). If pentobarbital is used, it's in combination with opioids (see below), because barbiturates have the effect of lowering a person's pain threshold.

3) Opioids

Opioids (strong pain-killers) can be used as an add-on to either benzos (for procedures up to about 1 1/2 hours) or barbiturates (for procedures longer than 2 hours).

At first glance, the use of opioids seems appealing, because of the pain-killing factor. In reality, this usually only comes into play for post-treatment pain, because local anaesthesia will take care of any pain during treatment. However, should the local anesthetic effect begin to lessen, an opioid will help to alter the experience of pain. However, what is often done instead is give a long-acting local anaesthetic where post-op pain is expected. When you take opioids, even excruciating pain becomes tolerable - you can still feel the pain, but somehow you don't care (I've tried it!). Also, where barbiturates are used, an opioid must be added to counteract their pain-threshold-lowering properties.

Opioids are always used in the so-called Jorgensen technique (which in its basic form involves pentobarbital, an opioid, and an anticholinergic) sometimes used in the US for procedures taking 2 hours or more.

The addition of an opioid may also be desirable if a benzo has been administered to its maximal recommended dose yet the patient remains unsedated (which is more likely if you've been hitting the valium hard for years). In this case, adding an opioid may provide the desired sedation. Alternatively, propofol (see below) may be used.

Opioids which may be used for IV sedation include:

* Meperidine (Demerol)
* Morphine
* Butorphanol (Stadol)
* Nalbuphine (Nubain)
* Fentanyl (Sublimaze)
* Pentazocine (Talwin)

4) Propofol

Some anaesthetists use Propofol instead of benzos. The advantage of this is the very rapid recovery time, less than 5 mins. The disadvantage is the drug must be continuously administered, so the drug is pumped in using an electric infusion pump, the dose rate is set by the anaesthetist. Propofol is not a common sedative agent because it's very easy to tip over into GA with it (where reflexes such as breathing are lost). It can be useful if a person is "immune" to benzos because they've been hitting them hard for years.

There are quite a few other drugs that CAN be used for IV sedation. But in practical terms, most of the time a single benzo, usually midazolam, is used. This is especially true in the UK, where polydrug use is discouraged (even though it is not illegal). A typical IV session takes up to 1 1/2 hours. If it takes longer, it's done in multiple visits, or depending on the case, under General Anaesthesia.

In the US, the situation is slightly more complex. Polydrug use appears to be much more common, possibly because IV sedation is taught at a high level. This encourages the use of polypharmacy (multiple drugs). Also, there appears to be a liking for long IV sessions, which require the use of polypharmacy. Long IV sessions may be driven by consumer demand, or maybe it's a training issue (I don't know).

Many US IV specialists are opposed to the use of opioids for sedation, but there is a habit of using them ingrained in most practitioners. However, things appear to be changing as new dentists are coming through.