With newer drugs, should patients wait 24 hours to drive, use machinery?

Studies look beyond psychomotor impairment to sleepiness

An outpatient surgery patient received general anesthesia, went back to work the same day, and drove a busful of passengers 95 miles.1 Another surgical patient left a health care facility where he had received general anesthesia, went home, and used a chain saw.

"He remembered being told not to drive a car, but did not think that advice applied to operation of a chain saw," says J. Lance Lichtor, MD, professor in the department of anesthesia at the University of Iowa in Iowa City.

These incidences, which did not result in injuries, sound outrageous. However, as new agents with better dispersal and metabolic rates gain widespread popularity, same-day surgery providers are raising an important question: Do patients need to wait 24 hours to drive, operate heavy machinery, and make important decisions?

A newly published study says that the current recommendation to refrain from driving for 24 hours after general anesthesia lacks evidence. The 12 volunteers were randomized to one of three different conditions: general anesthesia (with propofol and fentanyl), alcohol, or no drugs.2

"There was no significant difference in post-anesthetic driving skills at two, three, and four hours post-anesthesia, and the corresponding control sessions," the authors say.

Additionally, there was no significant difference among the three sessions in terms of pen-and-paper tests of psychomotor performance, they say.

The authors concluded that certain driving skills return by two hours after one half-hour of general anesthesia of propofol, desflurane, and fentanyl in a group of young volunteers.

However, the lead author cautions that this study didn’t reflect the experience of actual surgery patients because no pain medications were used and one of the most common sedates, midazolam HCl (Versed), was not used.

"Before we make changes in current guide-lines that would impact patient care, it would be important to do large-scale study on actual patients," says David R. Sinclair, MD, assistant professor of anesthesiology at the University of Florida College of Medicine and program director of conscious sedation reporting at University of Florida Anesthesia, Shands Jacksonville.

Some providers look warily at the current 24-hour guidelines. Those guidelines are related to the older drugs, says Paul F. White, PhD, MD, professor in the department of anesthesiology and pain management at the University of Texas Southwestern Medical Center, Dallas. "Currently, most practitioners routinely use short-acting anesthetic drugs in combination with local anesthetics," he says.

Another reason that the 24-hour guidelines are being debated is that despite instructions, some patients drive or operate heavy machinery after sedation. In fact, studies suggest that, based on a binomial distribution, each year between 780,000 and 1.7 million individuals may drive or operate heavy machinery despite explicit instructions to the contrary, Lichtor says.1,3,4

When examining whether to change the guidelines at your facility, consider these factors:

Sleepiness lasts longer than psychomotor impairment.

In studies that measure sleepiness, there is clear evidence that patients remain sleepier longer than they show psychomotor impairment, Lichtor says. One study that Lichtor published showed residual sleepiness up to eight hours after sedation.5 "In contrast, psychomotor impairment, as measured using standard psychomotor tests, was evident only for two hours," he says.

In one of the few studies that assessed psychomotor performance and sleepiness, psychomotor impairment was seen for eight hours, but drowsiness was present for 12 hours after barbiturate or ether anesthesia.6 A National Institute on Drug Abuse monograph on drugs and driving reiterates the fact that drowsiness outlasts psychomotor impairment.7

In one study of patient symptoms 24 hours after ambulatory surgery, 10% of patients felt drowsy.8 Drowsiness varied by type of surgery, according to that study. One-third of patients undergoing laparoscopy and one-fifth of patients undergoing general surgery complained of drowsiness at 24 hours. Patients who had undergone dilatation and curettage of the uterus and eye procedures had a lower incidence of drowsiness.

One drug is particularly problematic concerning sleepiness, Lichtor maintains. "If an anesthetic with only propofol and fentanyl is given, the amount of sleepiness is much less than if midazolam is added to the mix," he says.

There’s no one answer for every patient.

Although 24 hours is the typical guideline for waiting to drive and operate heavy machinery, treat each patient as an individual, recommends Jeffrey L. Apfelbaum, MD, professor and chair of the department of anesthesia and critical care at the University of Chicago Hospitals.

Consider these factors: how each person metabolizes drugs, the patient’s entire medical history, concomitant medications, the surgical procedure, the patient’s degree of postoperative pain, and how the pain is being managed, Apfelbaum suggests. "A broad constellation of questions have to be answered," he says.

For example, a patient might have a mole removed at 5 p.m., but have a heavy degree of medication, Apfelbaum says. "We may advise them to not drive for 36 hours," he says.

Medication may cause drowsiness or slow reflexes, Apfelbaum points out. Some pain medications, such as Tylenol No. 3, caution against driving or operating heavy machinery for as long as patients are taking medication, he says.

In addition to medication concerns, pain can be a significant distraction, he points out.

Also, each patient has a different level of anxiety related to surgery, he says. Also, "it may not be prudent to operate heavy machine or drive . . . simply because of the physical exhaustion related to stress," Apfelbaum says.

Handle moderate (conscious) sedation the same as you do other forms of anesthesia.

Studies have shown that patients are sleepier up to eight hours after receiving sedation.9

"With moderate sedation, the rules are the same certainly as for any type of surgery," Apfelbaum says. "The drugs they receive at the time and the patient’s history, the type of procedure, and whatever pain medications they prescribe are the main determining factors, not the level of sedation."

There are no scientific data to support a 24-hour waiting period to drive when patients undergo brief ambulatory procedures (fewer than 60 minutes) with intravenous sedation (e.g., monitored anesthesia care) or general anesthesia when short-acting anesthetics are used, White says. He maintains that the 24-hour waiting period is from several decades ago when longer-acting anesthetic drugs routinely were used during surgery.

"We know that from a practical point of view, it is unnecessary to wait 24 hours to resume normal activities," White adds. "It’s one of those situations where there is a lag between the science and its application in the clinical setting."

However, in the current litigious state of health care, no one wants to push the issue, he says.

"We all know that it’s probably not a problem, but no one is saying we should change our guidelines," White says.

[Editor’s note: When do you think patients should be allowed to drive after moderate sedation? Cast your vote on the SDS web site, www.same-daysurgery.com, in the "poll" section. Your user name is your subscriber number from the mailing label. Your password is sds (lowercase) plus your subscriber number — no spaces.]


1. Ogg TW. An assessment of postoperative outpatient cases. Br Med J 1972; 4:573-576.

2. Sinclair DR, Chung F, Smiley A. General anesthesia does not impair simulator driving skills in volunteers in the immediate recovery period — a pilot study. Can J Anaesth 2003; 50:238-245.

3. Correa R, Menezes RB, Wong J, et al. Compliance with postoperative instructions: A telephone survey of 750 day surgery patients. Anaesthesia 2001; 56:481-484.

4. Laffey JG, Boylan JF. Patient compliance with preoperative day case instructions. Anaesthesia 2001; 56:906-924.

5. Lichtor JL, Alessi R, Lane BS. Sleep tendency as a measure of recovery after drugs used for ambulatory surgery. Anesthesiology 2002; 96:878-883.

6. Doenicke A, Kugler J, Laub M. Evaluation of recovery and street fitness’ by EEG and psychodiagnostic tests after anaesthesia. Can Anaesth Soc J 1967; 14:567-583.

7. Linnoila M. "Anesthetics and foreign tranquilizers." In Willette RE. Drugs and Driving. National Institute on Drug Abuse, ed. NIDA research monograph series 11. Rockville, MD: U.S. Department of Health, Education, and Welfare; 1997.

8. Chung F, Un V, Su J. Postoperative symptoms 24 hours after ambulatory anaesthesia. Can J Anaesth 1996; 43:1,121-1,127.


For more information, contact:

  • Jeffrey L. Apfelbaum, MD, Professor and Chair, Department of Anesthesia and Critical Care, University of Chicago Hospitals. 5841 S. Maryland Ave., Chicago, IL 60637.
  • J. Lance Lichtor, MD, Professor, Department of Anesthesia, University of Iowa, Iowa City. E-mail: lance-lichtor@uiowa.edu.
  • David R. Sinclair, MD, Assistant Professor, Anesthesiology, University of Florida College of Medicine, Program Director, Conscious Sedation Reporting, University of Florida Anesthesia, Shands, 655 W. Eighth St., Jacksonville, FL 32209. Telephone: (904) 244-4630. Fax: (904) 244-4908. E-mail: david.sinclair@jax.ufl.edu.
  • Paul F. White, PhD, MD, Professor, Department of Anesthesiology and Pain Management, University of Texas Southwestern Medical Center, Dallas. E-mail: paul.white@utsouthwestern.edu.