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.