Ketamine Infusion and Hypoventilation

Procedures performed under sedation have the same severity in regards to morbidity and
mortality as procedures performed under general anesthesia1. The demand for anesthesia care
outside the operating room has increased tremendously and it poses, according to a closed
claim analysis, major risks to patients . Both closed claim analysis identified respiratory
depression due to oversedation as the main risk to patients undergoing procedures under
sedation. The major problem is that hypoventilation is only detected at very late stages in
patients receiving supplemental oxygen. Besides the respiratory effects of hypoventilation,
hypercapnia can also lead to hypertension, tachycardia, cardiac arrhythmias and seizures.

The incidence of anesthetized patients with obstructive sleep apnea has increased
substantially over the last years along with the current national obesity epidemic. These
patients are at increased risk of hypoventilation when exposed to anesthetic drugs. The
context of the massive increase in procedural sedation and the extremely high prevalence of
obstructive sleep apnea poses major respiratory risks to patients and it may, in a near
future, increase malpractice claims to anesthesiologists. The development of safer
anesthesia regimen for sedation are, therefore, needed. The establishment of safer
anesthetics regimen for sedation is in direct relationship with the anesthesia patient
safety foundation priorities. It addresses peri-anesthetic safety problems for healthy
patient's. It can also be broadly applicable and easily implemented into daily clinical
care.

Ketamine has an established effect on analgesia but the effects of ketamine on ventilation
have not been clearly defined. The lack of validated and sensitive instruments to evaluate
the effects of ketamine on ventilation is an important reason for the conflicting
results.The investigators have demonstrated that the transcutaneous carbon dioxide monitor
is accurate in detecting hypoventilation in patients undergoing deep sedation. Animal data
suggest that when added to propofol in a sedation regimen, ketamine decreased
hypoventilation when compared to propofol alone. It is unknown if ketamine added to a
commonly used sedative agent (propofol) can decrease the incidence and severity of
hypoventilation in patients undergoing deep sedation. It is also unknown if the effect of
ketamine on ventilation are different in patients with and without obstructive sleep apnea.

The investigators hypothesized that patients receiving ketamine and propofol will develop
less intraoperative hypoventilation than patients receiving propofol alone. The
investigators also hypothesized that this effect will be even greater in patients with
obstructive sleep apnea than patients without obstructive sleep apnea.

Significance: Respiratory depression due to oversedation was identified twice as the major
factor responsible for claims related to anesthesia. The high prevalence of obstructive
sleep apnea combined with more complex procedures done in outpatient settings can increase
physical risks to patients and liability cases to anesthesiologists. The main goal of this
project is to establish the effect of ketamine in preventing respiratory depression to
patients undergoing procedures under sedation. If the investigators confirm the their
hypothesis , their findings can be valuable not only to anesthesiologist but also to other
specialties ( Emergency medicine, gastroenterologists, cardiologists, radiologists) that
frequently performed procedural sedation. The research questions is;does ketamine prevent
hypoventilation during deep sedation? The hypotheses is; ketamine will prevent
hypoventilation during sedation cases.