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Gastrointest Endosc. 2000 Jul;52(1):48-54.

Conscious sedation and cardiorespiratory safety during colonoscopy.

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Departments of Medicine, Research, and Clinical Physiology, Kuopio University Hospital, Finland.



Cardiorespiratory events during colonoscopy are common. The effect of sedative premedication on cardiorespiratory parameters during colonoscopy has not been studied in controlled, prospective trials.


One hundred eighty patients undergoing colonoscopy were divided into 3 groups: (1) sedation with intravenous midazolam (midazolam group); (2) sedation with intravenous saline (placebo group); and (3) no intravenous cannula (control group). Arterial oxygen saturation (SaO(2)), systolic and diastolic blood pressure and continuous electrocardiogram were recorded prior to, during and after the endoscopic procedure.


Midazolam produced lower SaO(2) values during colonoscopy compared with placebo or control groups (p < 0.001, repeated measures analysis of variance). Systolic and diastolic blood pressure during colonoscopy were lower in the midazolam group than in the placebo group (p < 0.01 and p < 0.05, respectively), but no difference was found between the midazolam and the control groups. Hypotension (systolic blood pressure less than 100 mm Hg) occurred more frequently in the midazolam group (19%) than in the placebo (3%; p < 0.01) or control groups (7%; p < 0.05). ST-segment depression developed in 7% of patients during the recording with no difference between the groups. In 75% of cases ST-depression appeared prior to the endoscopic procedure.


Premedication with midazolam induced a statistically significant decrease in arterial oxygen saturation and increased the risk for hypotension. However, colonoscopy proved to be a safe procedure both with and without sedation.

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