What is Ketamine? Ketamine as an Anesthetic

Ketamine is a Useful Human Anesthetic

Ketamine is supplied as a liquid, often at 100mg/ml solution.
Ketamine is supplied as a liquid, often at 100mg/ml solution. | Source

What is Ketamine?

Ketamine is classified as a "dissociative anesthetic". It causes profound distortion of the perception of sensory input. In other words, it causes the recipient to have an "out of body" feeling, can cause hallucinations, causes significant pain relief, and makes purposeful movement difficult or unlikely. It is related to PCP, a hallucinogenic drug of abuse.

Most people associate the anesthetic use of ketamine with veterinary practice, but it is used fairly commonly in humans. Sometimes, it is the drug of choice in certain circumstances. Because ketamine produces many of the effects of general anesthesia without causing dangerous changes in breathing, it is often used by emergency medicine doctors. The impressive pain blockade produced by ketamine is very useful in children and adults during emergency procedures that would otherwise not be able to be performed in the ER setting. It is used more often in children for this purpose, as adults are more prone to emergence delirium and disturbing hallucinations than are children.

KETAMINE

Chemical structure of ketamine
Chemical structure of ketamine | Source
Ketamine is useful as an anesthetic, being used most frequently for painful, short procedures on children.
Ketamine is useful as an anesthetic, being used most frequently for painful, short procedures on children. | Source

Ketamine Effects

Ketamine acts in the brain at a specific site called the NMDA receptor. Blocking this receptor causes the characteristic effects of ketamine.

A patient who has received ketamine may have the following effects, dependent on the dose, the situation and other drugs administered at the same time. Not all of these effects occur in every person, every time.

  • Eyes open, staring or with repetitive motion of eyeballs (nystagmus)
  • Conscious-appearing, but not responding meaningfully to the environment
  • Tense muscles with random movements that may seem purposeful, but likely are not
  • Reflexes (cough, swallow, etc) intact, or at least mostly so
  • Salivation or drooling
  • Some pupil dilation
  • No response to stimuli that would otherwise be painful (profound analgesia)
  • Amnesia after the fact. Some memories are possible, but are usually incomplete and may not be specific
  • Watery eyes, decreased blinking
  • Potential emergence delirium, to be discussed below

From Clinical Practice

CASE #1

A 28 year old woman delivers a healthy newborn, vaginally. She is doing well, but needs to have a short procedure after the birth (sewing a tear and removal of retained placenta). The local anesthetic numbing medicine isn't working well, so the anesthesiologist gives ketamine to help her through.

The ketamine works well and she is unresponsive and seems comfortable during the procedure. Upon emergence, she is noted to be combative with elevated heart rate and blood pressure. During the short time it takes her to wake up, she appears to be frightened and does not respond to verbal reassurance. Another medication (midazolam, a benzodiazepine) is given to help her calm down.

Once fully awake, she acknowledged that she had no memory of the procedure and recalls no pain. However, she describes her emergence experience as "terrifying", "felt like she would die" and would never ever consent to the drug again.

CASE #2

A 60 year old man was having a spinal cord stimulator placed for relief of chronic pain. He would need to be comfortable during placement of the device, but fully awake and interactive during testing of the new stimulator. Midazolam was given for initial sedation, along with fentanyl. Because of his chronic lung disease, no further agents were deemed acceptable risk. Ketamine was used to relieve pain and maintain his spontaneous breathing. He had no significant changes in blood pressure, heart rate or oxygen level.

When the ketamine wore off, he reported no memory of the preceding 25 minutes. He had no pain and had no emergence delirium.

It is the practice of many anesthesiologists (this one included) to administer a benzodiazepine before ketamine to prevent emergence delirium.

He was thrilled with the anesthesia, as was the pain doctor placing and testing the device, and wondered if he could "always have that drug".

Ketamine Side Effects

Emergence delirium is the most common, unpleasant side effect of ketamine. Adults more than children, can have illusions/hallucinations, vivid and frightening dreams, excitability, combativeness and out-of-body experiences upon awakening from ketamine sedation or anesthesia.

The reaction can occur during the first hour of emergence from ketamine and vivid, unusual dreams can persist for several hours. Flashback phenomena have also been reported.

These reactions may be of little consequence or they may be quite frightening and unpleasant. Administration of a benzodiazepine medicine (like midazolam- in the same family as Ativan and Valium) has been shown to help prevent emergence delirium in adults.

Adults, women, those receiving higher doses and patients with pre-existing psychiatric disease are more prone to experience unpleasant emergence.

For the health care provider, there are several situations when ketamine should not be given. Ketamine increases pressure in both the eyeball and the brain, so should often be avoided if patients have severe glaucoma, an open-globe injury or brain swelling.

It may also be wise to avoid ketamine in patients where avoidance of increased heart rate or blood pressure is essential.

Ketamine as an Anesthetic

On the other hand, ketamine can (and probably should) be used in some of the sickest, most tenuous patients where use of other medications would worsen a life-threatening situation.

Ketamine stimulates the central nervous system and cardiovascular system. This allows heart rate and blood pressure to be maintained; this is the opposite effect of many other anesthesia drugs. In patients with certain types of heart disease, trauma with blood loss, shock and other situations where standard anesthesia drugs would cause further deterioration by depressing the cardiovascular system, ketamine is invaluable.

In addition, ketamine is often used in emergency rooms, especially for children. Ketamine can be given by intramuscular, intravenous and increasingly by oral or nasal routes. Because ketamine allows spontaneous breathing to be maintained and has a predictable duration of action, it's safety profile is very good in these situations.

Patients who are victims of burn injuries have to have frequent changing of their bandages. Ketamine provides excellent pain relief, without long-lasting effects or side-effects for this type of procedure.

PROCEDURAL SEDATION WITH KETAMINE ON A CHILD

You can see the child's eyes are open, but he is not responding at about the 3:30 mark. At about 4:50, the sewing starts. The medicine is redosed at 5:30. Don't watch the sewing if you are squeamish.

Ketamine Abuse

As used in the clinical setting, patients will not become addicted to ketamine. Unfortunately, ketamine has become a "club drug", especially when used with other drugs. Usually, the ketamine abuses is addicted to several recreational, illegal substances.

Special K, as it is known, has also been used as a rave and date-rape drug. Usually, the drug is obtained through theft of veterinary offices and sold illegally to distributers and users.

In the last few years as abuse has become even more common, more cases of urinary dysfunction have been reported from repeated ketamine use. Most patients report painful urination, bloody urine, frequent need to urinate and other symptoms. These symptoms all result from what seems like a dose-dependent bladder dysfunction.

Memory and psychiatric disorders also occur after repeated abuse of ketamine.

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Comments 6 comments

Marcy Goodfleisch profile image

Marcy Goodfleisch 4 years ago from Planet Earth

This is amazing information! I had no idea there were so many variations in anesthetics - your hubs are always so full of great facts. Thanks for enlightening us - many votes up here!


Nettlemere profile image

Nettlemere 4 years ago from Burnley, Lancashire, UK

Very interesting - I'd come across it in animals but not humans (except in a murder mystery on TV where the murderer stole ketamine from the vet and used it to immobilise his victims before killing them!)


ScribeRight profile image

ScribeRight 4 years ago from Reading, PA

Thanks for posting. It's nice to see legitimate scientific information being posted here. I had only a couple of comments or suggestions. Although I know you can't include everything, kappa versus mu selectivity might help people better understand the seeming wide range of effects and the abusive properties of special K compared with other analgesics. Perhaps a follow up to this post? Universities should certainly make the list for sources of theft since ketamine is commonly used in small animal research in laboratories lacking the oversight and security available at other sources. As an MD, you may be aware that special K has been known to make its way to more than a few med students via these laboratories over the years.


TahoeDoc profile image

TahoeDoc 4 years ago from Lake Tahoe, California Author

Thanks for reading Scribe! You are correct that University stock is often 'tapped' into for recreational purposes.

For this article of general information, I didn't want to get too much into the chemistry of ketamine or its actions on opioid receptors, discussion of the enantiomers and so on. You are right, it may make a good follow-up hub at some point, especially if the focus of it is on the abuse, rather than an overview of its anesthetic use.

Thanks everyone for reading!


Dolphan5 profile image

Dolphan5 4 years ago from Warwick R.I

Well written an informative. It seems to be an option when other drugs

can't be used or won't function effectively.

Thanks for the enlightenment!

Voted thumbs up ! etc.etc.

Thank you!


Bishopdown profile image

Bishopdown 4 years ago from Tampa, Florida

A very nice hub and interesting. I am familiar with Ketamine from its use in pharmaceutical compounding. We used the powder form to make various pain creams for patience with muscle spasm, back pains and similar related injuries. This was very interesting because I believe that we should have been more protected against using this chemical and I know that after long term use, the Ketamine will have some profound effects on patients as well as the technicians that made the medications.

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