Physician anesthesiologist at Stanford at Associated Anesthesiologists Medical Group
Richard Novak, MD is a Stanford physician board certified in anesthesiology and internal medicine.Dr. Novak is an Adjunct Clinical Professor in the Department of Anesthesiology, Perioperative and Pain Medicine at Stanford University, the Medical Director at Waverley Surgery Center in Palo Alto, California, and a member of the Associated Anesthesiologists Medical Group in Palo Alto, California.

Street use of the anesthetic ketamine is on the rise. Kylie, a 28-year-old professional female, recently told me about her experience snorting recreational ketamine: “I was feeling anxious and I was feeling sad. My friend suggested I try snorting some ketamine crystals she had, and when I did . . . I had the best feeling of my life. The drug made me happier. It made the next hour a fun experience without any sadness, and when the high wore off an hour later my sadness was still gone. It was as if I’d been treated with some antidepressant drug, and the improvement in my mood was more lasting than the initial buzz. Now I see my future using ketamine as a periodic antidepressant. When you read about it on the internet, doctors are prescribing ketamine as a treatment for depression, but the whole medical clinic intravenous treatment is really expensive. It’s a lot easier to do it myself with ketamine I buy on the streets.”

Hmmm. We’re all aware of the dangers of recreational drug use with cocaine or methamphetamine or narcotics. We’re all aware of the dangers of recreational drugs laced with fentanyl, a powerful drug that can stop a person’s breathing and kill them in minutes. In this context, what kind of a threat is street ketamine?



Ketamine is a powerful general anesthetic drug in an anesthesiologist’s toolbox. In 1962 Calvin Stevens, a professor of chemistry at Wayne State University, synthesized ketamine from phencyclidine (PCP), an animal tranquilizer/anesthetic also known as angel dust, with the desired goal of discovering a safer anesthetic with fewer hallucinogenic effects than PCP.

Anesthesiologists administer ketamine intravenously to produce general anesthesia without utilizing any anesthesia gas. We call ketamine a dissociative drug, because it can distort sensory perception and impart a feeling of detachment from oneself and the environment. The drug can produce bizarre and unpleasant nightmares, so anesthesiologists are trained to pair ketamine with an intravenous benzodiazepine such as Versed to temper ketamine’s potentially frightening dream world. Anesthesiologists are also trained to pair ketamine with an anticholinergic (mouth-drying) medication such as atropine or glycopyrrolate (Robinul), because ketamine can produce excessive salivating, which can lead to a patient choking on a rising tide of saliva.

For anesthesia usage, ketamine is a clear liquid with a concentration of 100 mg/ml or 50 mg/ml.

Because ketamine is an effective general anesthetic in one syringe, it’s included on the World Health Organization’s list of essential drugs.  For medical sedation, ketamine is typically diluted and administered intravenously in small boluses of 20 to 30 mg, and titrated to obtain the desired depth of anesthesia.  To induce general anesthesia, the intravenous dose is 1 – 4.5 mg/kg, or a mean dose of 2 mg/kg = 100 mg for a 50 kg adult. If it’s not possible to insert an IV line (e.g. if a patient is uncooperative, developmentally delayed, or is a child), a combination of 2 mg/kg of ketamine, 0.2 mg/kg of midazolam, and .02 mg/kg of atropine can be administered as an intramuscular injection into the deltoid muscle of the shoulder or the quadriceps muscle of the anterior thigh. To induce general anesthesia with intramuscular ketamine alone, dosing levels are higher than for intravenous use, for example the intramuscular dose is 6.5 – 13 mg/kg, or a mean dose of 10 mg/kg = 500 mg ketamine for a 50 kilogram adult.

How does medical ketamine affect a patient’s ABCs of airway, breathing, and circulation? Patients typically maintain an adequate airway and breathing during ketamine sedation and anesthesia, which is advantageous in short surgical procedures because this often eliminates the need for a breathing tube. Ketamine causes stimulation of the cardiovascular system, with the potential side effect of increasing blood pressure.

There is no reversal agent for ketamine. If an administered ketamine dose is excessive, a patient’s airway and breathing may become compromised, resulting in inadequate oxygen delivery to the lungs, heart, and brain. Patients who are obese, or who have obstructive sleep apnea, may lose their safe airway and breathing status during ketamine sedation. Ketamine can elevate blood pressure, so vigilant monitoring of the blood pressure is required, and acute treatment for hypertension may be necessary. Because of these risks, ketamine administration is typically limited to anesthesia professionals or physicians who are experts in the emergency management of airways and acute vital sign changes.



Multiple meta-analyses have concluded that IV ketamine is an effective rapid-acting antidepressant for major depressive disorders.  Ketamine was first reported to have antidepressant properties in the year 2000, when published data showed that an intravenous administration of a sub-anesthetic ketamine dose resulted in a reduction of symptoms in major depressive disorder (MDD). MDD is a common disorder with significant consequences. A 2012 epidemiological study of mental health in Canada showed the lifetime prevalence of major depressive disorder was 3.9%. The prevalence was higher in women and in younger age groups. Ketamine is a treatment option for patients suffering from treatment-resistant depression (TRD). IV ketamine can exert rapid antidepressant effects as early as several hours after administration. In contrast, traditional oral antidepressant pills usually require several weeks of therapy for a clinical response. Ketamine has a unique mechanism of action on the central nervous system, at the NMDA (N-methyl-D-aspartate) and AMPA (𝛼-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) receptors, rather than at the serotonin and/or noradrenaline neurotransmitters that are the sites of action for traditional antidepressant pills such as Prozac, Paxil, or Zoloft.

Intravenous ketamine clinics are typically supervised by an attending anesthesiologist whose is present is to ensure the safe management of airway, breathing, and circulation during these brief sedation anesthetics. Intravenous ketamine administered in a clinic setting can result in adverse effects during the infusion period and immediately afterward, including nausea, vomiting, drowsiness, dizziness, confusion, dissociation, or an increase in blood pressure.Typically an infusion of 0.5 mg/kg of ketamine (e.g. 40 mg for an 80 kg patient) is administered slowly over 40 – 60 minutes. The patient will remain onsite in a recovery room until the sedative effects have cleared. Patients report positive antidepressant effects within two hours, and these effects last for one to two weeks. Data demonstrate a positive response rate of 44% after six intravenous ketamine treatments in patients with treatment-resistant depression.  A series of anesthetics will cost significantly more than one Prozac pill per day, so the use of ketamine as an antidepressant is directed at treatment-resistant depression.



In 2019 the FDA approved a nasal spray called Spravato (active ingredient esketamine) for major depression that failed treatment with two or more oral antidepressants.

Per the Spravato website:

SPRAVATO® is a non-competitive N-methyl D-aspartate (NMDA) receptor antagonist indicated, in conjunction with oral antidepressant, for the treatment of:  treatment-resistant depression in adults, depressive symptoms in adults with major depressive disorder (MDD) with acute suicidal ideation or behavior.

SPRAVATO® is intended for use only in a certified healthcare setting.

SPRAVATO® is intended for patient administration under the direct observation of a healthcare provider, and patients are required to be monitored by a healthcare provider for at least 2 hours. SPRAVATO® must never be dispensed directly to a patient for home use. 



The advantage of intranasal ketamine is that it does not require an IV, and it requires monitoring by a healthcare provider but does not require an anesthesiologist to supervise its administration.



To supply the illicit street market, diverted pharmaceutical liquid ketamine is evaporated from its liquid solution into a powdered form.

How popular is recreational ketamine? The number of ketamine seizures by federal, state and local law enforcement in the United States increased from 55 in 2017 to 247 in 2022. The total weight of ketamine confiscated increased by more than 1,000 percent over the five years. The majority of the confiscated ketamine was in powder form. According to the DEA (Drug Enforcement Agency), powdered ketamine is typically packaged in “small glass vials, small plastic bags, and capsules as well as paper, glassine, or aluminum foil folds. . . . powdered ketamine is cut into lines known as bumps and snorted, or it is smoked, typically in marijuana or tobacco cigarettes. . . . Ketamine is found by itself or often in combination with MDMA, amphetamine, methamphetamine, or cocaine. . . . Ketamine produces hallucinations. It distorts perceptions of sight and sound and makes the user feel disconnected and not in control. A ‘Special K’ trip is touted as better than that of LSD or PCP because its hallucinatory effects are relatively short in duration, lasting approximately 30 to 60 minutes as opposed to several hours. . . . An overdose can cause unconsciousness and dangerously slowed breathing.” (bold lettering mine.)

Recreational users call the phenomenon of a deep ketamine high as a “K-hole.” Falling into a K-hole means the drug user is temporarily unable to interact with others or the world around them. Some people refer to a K-hole as an out-of-body or near-death experience. The effects of long-term use of dissociative drugs such as ketamine haven’t been exhaustively studied, but ketamine use is thought to be reinforcing, meaning that individuals find the ketamine high an experience they wish to repeat. Repeated ketamine usage likely leads to some degree of tolerance and physical dependence.

The website The Cut states that “most of the recreational users . . . take K in very small doses, seeking a pleasant buzz that wears off within 30 minutes or can be re-upped as needed. It’s often taken to compliment other drugs — a garnish instead of the main course. For a generation that has less free time for sprawling multi-day psychedelic trips, ketamine has an appealing choose-your-own-adventure quality. . . . Claire says it actually feels like a healthier and more mature lifestyle. ‘People are like: I used to go out and have 16 drinks and do a bunch of cocaine and feel like shit the next day. And then it was this total shift [to ketamine]: Oh, yeah, I can do this. And it still feels like stepping out of my life, but I also feel fine tomorrow.’ At this point, she says: ‘I wouldn’t say that it’s different than like, a bunch of people getting off work and going out for drinks.’”



Can a layperson use ketamine recreationally to treat themself for depression? The specter of self-treatment reminds one of the saying that a physician who treats himself has a fool for a doctor and a fool for a patient. A corollary of this is: a person who treats his or her mood disorder with recreational ketamine has a fool for a caretaker and a fool for a patient.

Kylie will attempt to titrate ketamine recreationally to treat her depression. But a precise, tailored medical dose is required for patients to experience optimal benefit from ketamine with safety. Individuals who self-administer ketamine expose themselves to serious health risks. Ketamine may make their symptoms worse, or they may even die from the habit. Kylie has no plans to have a healthcare provider present when she self-administers ketamine. Kylie has no idea of the milligram dose she is snorting. Her ketamine is not FDA-approved, and may in fact contain fentanyl at a dose that could cease her breathing and kill her.

How dangerous is ketamine? A meta-analysis of the published medical literature showed a total of 312 overdose cases and 138 deaths from recreational ketamine. There were no cases of overdose or death related to the use of ketamine as an antidepressant in a therapeutic setting. Street ketamine may seem cheaper, as the cost of ketamine on the street is approximately $100 per gram (1000 mg), and a single dose is approximately 100 mg. Medical treatment with 50 mg IV ketamine costs approximately $400-$800 per treatment. But ketamine administered by anesthesiologists in a clinic is safe, while there are legitimate respiratory and cardiac risks involved in the recreational use of ketamine.

If Kylie is depressed and seeks relief, an appropriate action would be to consult a psychiatrist. The alternative of intermittent recreational intranasal ketamine as a self-administered treatment for her depression is a dangerous detour.




The most popular posts for laypeople on The Anesthesia Consultant include: How Long Will It Take To Wake Up From General Anesthesia? Why Did Take Me So Long To Wake From General Anesthesia? Will I Have a Breathing Tube During Anesthesia? What Are the Common Anesthesia Medications? How Safe is Anesthesia in the 21st Century? Will I Be Nauseated After General Anesthesia? What Are the Anesthesia Risks For Children?

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Physician anesthesiologist at Stanford at Associated Anesthesiologists Medical Group
Richard Novak, MD is a Stanford physician board certified in anesthesiology and internal medicine.Dr. Novak is an Adjunct Clinical Professor in the Department of Anesthesiology, Perioperative and Pain Medicine at Stanford University, the Medical Director at Waverley Surgery Center in Palo Alto, California, and a member of the Associated Anesthesiologists Medical Group in Palo Alto, California.

An astronaut en route to Mars develops severe abdominal pain, nausea, and vomiting. A fellow crew member examines him and finds significant tenderness and guarding in the right lower quadrant of his abdomen. The crew members teleconference with physicians on Earth, with a 20-minute communication delay because of the 140-million mile distance between them. The physicians confirm a probable diagnosis of appendicitis. Because the spaceship is more than 200 days away from Earth, the physicians instruct the crew to proceed with surgery and anesthesia in outer space.

Outer space medical care will certainly not resemble Dr. Leonard “Bones” McCoy on the original Star Trek, who waved his fictional handheld “tricorder” tool over a patient to diagnose and treat the patient’s illness.

How will astronauts conduct general anesthesia and surgery in outer space? Is an anesthesiologist required on board? Is a surgeon required on board? If the flight crew doesn’t include any physicians, how will the crew proceed to save the astronaut’s life?

Full disclosure: I’ve never given an anesthetic in outer space. But to date, no one else has given an anesthetic to a human in outer space eitherProtocols regarding how to accomplish anesthesia in outer space exist in the medical literature.

For comprehensive reading I’d refer you to three papers by expert Matthieu Komorowski MD, an anesthesiologist, intensive care physician, and biomedical engineer at Imperial College London, and a former Research Fellow at the European Space Agency. Three of Komorowski’s key articles are: “Anaesthesia in outer space, the ultimate ambulatory setting?” in Current Opinion in Anaesthesiology; “Fundamentals of Anesthesiology for Spaceflight,Journal of Cardiothoracic Vascular Anesthesia, andPotential Anesthesia Protocols for Space Exploration Missions in Aviation Space Environmental Medicine.

Distant space missions, known as exploration class missions (e.g. missions to the Moon and Mars) are planned in the coming decades. Staffing an astronaut/physician as one of the crew members on a mission to Mars is possible, but I have no information that the National Aeronautics and Space Administration (NASA) is grooming a combination astronaut/anesthesiologist at this time.  In 2017, NASA created an Integrated Medical Model (IMM) as an evidence-based decision support tool to assess risks and design medical systems for extended space travel. The IMM includes 100 medical conditions that might commonly occur during space flight. Twenty-seven of these 100 conditions would require surgical treatment.

The most significant medical risks for space exploration missions are trauma, hemorrhagic shock, and infections. The risk of a medical emergency in space travel is estimated at one event per 68 person months. For a crew of six on a 900-day mission to Mars and back, at least one medical emergency would be expected. On a mission to Mars, the option of a stat return to Earth is impossible. Telemedicine can provide remote communication for medical consultation. While telecommunication between the Moon and Earth would have delays of only 2 seconds in each direction, for a Mars mission the delay in communications could reach up to 20 minutes in each direction, making real-time telemedicine impractical. The communications delay on a Mars mission would also mean that a surgical robot on board could not be controlled by a surgeon on Earth. The crew must be self-reliant.

Only physically and mentally fit candidates who are able to withstand the stresses of space travel are selected as astronauts. Physically and mentally fit candidates are at low risk for medical or surgical emergencies. But with the recent trend of privately funded space programs (e.g. SpaceX), some members of the general public may be offered the opportunity to experience space travel. Privately funded programs may push boundaries regarding the undesirable health status of candidates traveling into space.


To devise safe anesthetic care for outer space, one must first understand the changes in an astronaut’s body during microgravity. The void of outer space provides a lack of barometric pressure, a lack of oxygen, severe extremes of temperature, and dangerous levels of radiation. Spacecraft are equipped with Environmental Control and Life Support Systems (ECLSS) to ensure livable conditions within the space capsule.  Weightlessness and microgravity cause marked changes in human physiology, described by systems as follows:

Cardiovascular system 

Microgravity causes fluid to redistribute toward the upper half of the body, resulting in facial and airway edema (swelling), and diuresis (increased urination) which leads to an intravascular volume decrease of 10-15%. The systemic vascular resistance in the arterial system decreases about 14% because of dilatation of the blood vessels, but the left ventricular systolic function of the heart is maintained near normal.


Gastrointestinal system

Weightlessness causes a combination of decreased gastric motility and increased gastric acidity. If an astronaut requires general anesthesia, one must assume the patient has a full stomach and is at risk for aspiration.

Respiratory system

Microgravity leads to an increase in respiratory rate and a decrease in tidal volume, resulting in near normal ventilation.

Neurologic system

Microgravity interferes with inner ear function, and causes disturbances in balance and vestibular function. Constant exposure to artificial lighting alters sleep rhythms, and predisposes the crew to impaired mental acuity and depression.

Musculoskeletal system

Weightlessness and inactivity cause an increase in bone resorption. Bone density decreases by about 1% per month, which predisposes astronauts to long bone fractures and kidney stones secondary to increased calcium excretion. Prolonged microgravity leads to deconditioning of the muscular system with skeletal muscle atrophy. This is most marked in the lower body, as the legs become “effectively redundant.” 




IV fluids

Every anesthetic, regional or general, will require the patient to have an intravenous line, usually in their arm. Astronauts will be trained in the insertion of IV cannulae, and the sampling of blood for diagnostic tests. Storage of prepackaged intravenous fluids can occupy a large volume of precious cargo space. An exploration class mission may require up to 100 liters of IV fluids in case of severe burn injuries. Scientists have developed a system named IVGEN (Intravenous Fluid Generation) to prepare sterile IV normal saline from space station drinking water.

Bubbles in the IV fluids are dangerous, and are filtered out by the system, because bubbles could form air emboli and cause a stroke or a heart attack if they entered the body. Transfusable blood products have a limited shelf life, which makes an onboard blood bank impractical for prolonged space travel. Medical checklists will aim to ensure patient safety and help the astronauts gain familiarity with medical equipment and drugs. Medical kits on board will include a basic vital signs monitor, a mechanical ventilator, an ultrasound machine, suction, airway equipment, and a limited range of drugs with protocols regarding how to use them.


Standard patient monitoring would include ECG, non-invasive blood pressure cuff, oxygen saturation, end-tidal CO2, and temperature. Preoperative ultrasound examination can be applied for diagnostic use, the assessment of cardiac function and fluid status, and assistance in visualizing blood vessels for peripheral or central line placement.


A regional technique offers simplicity over general anesthesia, but a successful regional anesthetic requires skill, experience, training, and regular use of such skills. Studies on Earth show that an average of 20 procedures are required to reach a learning curve plateau. A practitioner must be schooled in regional anesthesia techniques on Earth prior to the space flight. The three suggested regional blocks to treat the majority of conditions expected to be encountered in space include femoral, sciatic, and brachial plexus nerve blocks. The blocks would be ultrasound-guided, and there is hope that AI-imbedded ultrasound technology will be available in the future to localize relevant structures such as nerves and blood vessels. The injection of a local anesthetic such as ropivacaine for a regional techniques carries the inherent risk of local anesthetic toxicity. The antidote for local anesthetic toxicity is lipid emulsion, which could occupy valuable space on board, and has a shelf life of only 24 months. Spinal blocks are impractical, as the use of typical hyperbaric local anesthesia such as 0.75% bupivicaine has not been investigated in microgravity to date.


General anesthesia has the advantages of a quick and reliable onset. The physiologic changes during microgravity predispose a general anesthesia patient to both aspiration of stomach contents and hypotension due to low intravascular volume. Each general anesthetic would require a preinduction loading with intravenous fluid replacement, followed by a rapid sequence induction and endotracheal intubation. In the absence of gravity, restraints will be required to keep the patient immobile for intubation.


Potent anesthetic gases such as sevoflurane cannot be used in outer space, as vaporizers will not function properly in microgravity. General anesthesia will include intravenous medications only. Ketamine will be the preferred drug of choice for induction of general anesthesia, as spontaneous respiration and cardiovascular stability are maintained. Ketamine induces both a dissociative state and analgesia, and has an extended shelf life of around 20 years in powder form. It’s currently used in remote locations on Earth where there is limited equipment and monitoring (e.g. combat anesthesia in low-income countries). The unpleasant psychomimetic side effects of ketamine are negated by the co-administration of an IV benzodiazepine such as midazolam or Valium. Intravenous atropine will also be administered to minimize the increased oral secretions produced by ketamine.

A muscle relaxant/paralytic drug is recommended to facilitate endotracheal intubation. Succinylcholine will not be used because of its ability to cause hyperkalemia. Rocuronium at a modified rapid sequence dose of 1mg/kg is recommended. A checklist and a PowerPoint presentation on the sequence of drugs and procedures needed to initiate general anesthesia will be available for the astronauts to read prior to and during the administration of general anesthesia. A video laryngoscope will be available, as it is recognized as an easier technique for inexperienced practitioners to complete successful endotracheal intubation. A publication by Komorowski and Fleming, “Intubation after rapid sequence induction performed by non-medical personnel during space exploration missions: a simulation pilot study in a Mars analogue environment,” demonstrated that intubation can be done by non-medical staff with little or no training via instructions from PowerPoint slides.

An intravenous infusion of ketamine is recommended for the maintenance of general anesthesia. Opioids are unlikely to be carried on a spacecraft. It’s likely the analgesic effects of ketamine will be used for acute pain relief. Sugammadex will be available to reverse the neuromuscular blockade from rocuronium, and neuromuscular monitoring will be utilized prior to extubation.


Restraining the surgeon, the patient, and the surgical tools against floating around the room in zero gravity are challenges to overcome in outer space. Magnetizing the surgical tools so they stick to the operating room table, and restraining the astronaut/surgeon and the patient are important adjustments. Surgery involving anesthesia was successfully performed on rodents for the first time in 1990 on the STS-90 Neurolab Space Shuttle. Astronauts repaired rat tails and performed laparoscopy on rodents in microgravity. It’s possible that insufflation of the human abdomen with carbon dioxide gas during laparoscopy in microgravity may cause changes in cardiac or respiratory function. During open abdominal surgery in microgravity, a patient’s intestines would float around and could obscure the view of the surgical field. Because of the large array of surgical equipment necessary for any specific surgery, a 3D printer on the spacecraft may be the solution to create tools as needed.

Bleeding in microgravity causes domes to form around the bleeding site. The domes are held in that shape because of surface tension. Enclosed surgical chambers have been developed to protect the sterile surgical field and the cabin environment during open surgeries in zero gravity. A hermetically sealed expandable surgical chamber for microgravity is called a “surgical overhead canopy” (SOC). The surgical repair can be performed within the canopy, and the canopy prevents organs or blood from floating about the cabin.

Surgical Overhead Canopy (SOC) SpringerLink Image



Anesthesia in Outer Space – Conclusion

For the appendicitis case introduced in paragraph one, the anesthetic would include the IV loading of 500 ml of normal saline; a rapid sequence intravenous induction of general anesthesia using ketamine, midazolam, atropine, and rocuronium; placement of an endotracheal tube into the patient; and an IV ketamine infusion for the maintenance of anesthesia. Once the patient is anesthetized, the surgery could either proceed as an open abdomen under a sterile surgical canopy, or a laparoscopy with the abdomen remaining closed, depending on the skillset and the surgical equipment available to the surgeon/astronaut on board.

One day an astronaut will perform the first anesthetic on a human in outer space. The astronaut will most likely not be a board-certified anesthesiologist, and he or she will likely follow a PowerPoint slide show demonstrating the sequence of procedures and pharmacology for successful anesthesia. Expect the first anesthetic in space to be a tense, exciting, and dramatic event in the history of medicine.




The most popular posts for laypeople on The Anesthesia Consultant include: How Long Will It Take To Wake Up From General Anesthesia? Why Did Take Me So Long To Wake From General Anesthesia? Will I Have a Breathing Tube During Anesthesia? What Are the Common Anesthesia Medications? How Safe is Anesthesia in the 21st Century? Will I Be Nauseated After General Anesthesia? What Are the Anesthesia Risks For Children?

The most popular posts for anesthesia professionals on The Anesthesia Consultant  include: 10 Trends for the Future of Anesthesia Should You Cancel Anesthesia for a Potassium Level of 3.6? 12 Important Things to Know as You Near the End of Your Anesthesia Training Should You Cancel Surgery For a Blood Pressure = 170/99? Advice For Passing the Anesthesia Oral Board Exams What Personal Characteristics are Necessary to Become a Successful Anesthesiologist?