all the patients who underwent radiologic non - vascular interventional procedures at our clinic during a 3-month period were asked to participate in this study . patients were excluded from the study if ( a ) they were younger than 18 years , ( b ) they had received a sedative or analgesic within 4 hours before the procedure , ( c ) the procedure was performed on night duty , and ( d ) the patient was in a critically ill state such as having a systolic blood pressure less than 80 mmhg . a total of 63 adult patients ( 29 females and 34 males ; mean age : 64 years ; age range : 27 - 82 years ) fit the selection criteria and they underwent moderate sedation for radiologic non - vascular interventional procedures . the following 72 radiologic non - vascular interventional procedures were performed in 63 adult patients : percutaneous transhepatic biliary drainage ( ptbd , n = 21 ) , percutaneous transhepatic gallbladder drainage ( ptgbd , n = 13 ) , percutaneous abscess drainage ( ad , n = 10 ) , percutaneous nephrostomy ( pcn , n = 10 ) , ptbd track dilatation for choledochoscopy ( tdc , n = 10 ) , implanting a ureteral double j stent ( djs , n = 3 ) , implanting a biliary stent ( bs , n = 2 ) , implanting a gastric stent ( gs , n = 2 ) , and radiofrequency ablation of hepatocellular carcinoma ( rfa , n = 1 ) . two different procedures were performed in nine patients at different times : ptbd ( n = 7 ) prior to tdc ( n = 6 ) and bs ( n = 1 ) , and pcn ( n = 2 ) prior to djs ( n = 2 ) . all patients who underwent percutaneous procedures received a local skin anesthetic of 5~15 ml of 2% lidocaine ( huons , hwaseong , korea ) . the moderate sedation protocol mainly followed the staged - dose system proposed by skehan et al . the drugs were administered just before the procedure by nurses under the direction of the radiologist . co. , hwasung , korea ) and midazolam hydrochloride ( roche , fontenay - sous - bois , france ) were administered intravenously as a slow ( 30 - 60 second ) bolus infusion in one to five steps ( a , b , c , d , e ) until the patient was drowsy and tranquil ( 7 ) . the doses per step were follows : a , fentanyl at 1 g per kilogram of body weight ; b , midazolam at 0.035 mg / kg ; c , fentanyl at 1 g / kg ; d , midazolam at 0.015 mg / kg ; e , midazolam as 1 - 2 mg boluses ( maximum : 0.15 mg / kg ) ( 7 ) . the desired end point of sedation was drowsiness , tranquility and a reduced sensitivity to pain ( 7 ) . the correct level of sedation had been achieved when the patient rested with their eyes closed , but the patient responded to verbal commands or mild physical stimulation ; this was a state of moderate sedation ( 14 ) . we used the first dose of fentanyl to estimate the lead time in our patient . the lead time is the time lapse between the drug injection and the clinical effect . we titrated the administration of the drug for effect and we stopped the administration of drug when moderate sedation was achieved . an interventional radiologist and radiology nurses were designated to monitor each patient and record the clinically important data on a standard form . a pulse oximeter was used to continuously monitor arterial oxygen saturation and ecg , while the blood pressure was automatically measured every 3 minutes . if the oxygen saturation decreased to between 90% and 95% , the patient was asked to take deep breaths . if the saturation decreased to 90% or less , supplemental oxygen was administered at a rate of 4 l / minute via a nasal cannula . as the doses of fentanyl citrate and midazolam hydrochloride were administered , the individual and cumulative doses were recorded on the procedural record form . co. ltd . , seoul , korea ) , and midazolam ( flumazenil , roche , basel , switzerland ) were available during all procedures . a visual analog scale , graded from 0 to 10 , the interventional radiologist questioned the patient about their pre - procedural anxiety before the procedure and about their their intraprocedural pain after the procedure . he asked the patients to describe their anxiety and pain with standardized adjectives that corresponded to numerical scores as follows : 0 , none ; 1 - 2 , mild ; 3 - 4 , discomforting ; 5 - 6 , distressing ; 7 - 8 , horrible ; and 9 - 10 , excruciating . the differences in drug doses and the pain scores between the procedures were tested using one - way analysis of variance . the mean procedure time , from the time of drug injection until the radiologist removed his surgical gloves just after the procedure , was 41 minutes ( range : 15 - 90 minutes ) . the mean total dose of fentanyl used per kilogram of body weight was 1.148 g in ptbd , 1.157 g in ptgbd , 1 g in ad , 1 g in pcn , 1.641 g in tdc , 1 g in djs , 2 g in bs , 1 g in gs and 2 g in rfa ( table 1 ) . the mean total dose per kilogram of body weight of midazolam was 0.035 mg in ptbd , ptgbd , ad , pcn , djs , gs and rfa , 0.039 mg in tdc and 0.043 mg in bs ( table 1 ) . significantly more fentanyl was required in the tdc procedure than in the ptbd , ptgbd , ad and pcn ( p < .05 ) . the number of required steps in the abcde protocol to achieve the moderate sedation is illustrated in table 2 . no patient was adequately sedated after step a , while 57 procedures were sufficiently drowsy after step b , 11 procedures after step c and four procedures after step d ( table 2 ) . the duration of the lead time in each procedure was 2 - 5 minutes ( mean : 3.8 minutes ) . the mean pain score during the procedure , which was recorded after all procedures , was 2.9 ( mild ) . figure 1 illustrates the distribution of the pre - procedural anxiety scores and the intraprocedural pain scores for all 72 procedures . four patients complained of pain scores greater than 5 during tdc ( three patients ) and bs ( one patient ) . these patients received an incremental dose of sedative or analgesic and an incremental dose of lidocaine . patients received supplemental oxygen ( 4 l / min ) via a nasal cannula in 14 ( 19.4% ) of 72 procedures due to an arterial oxygen saturation level of less than 90% . patients with an arterial oxygen saturation level between 90% and 95% were asked to take deep breaths in 11 ( 15.3% ) of 72 procedures . none of the patients required pharmacologic reversal of the sedation because of hypoxia . in 5 ptbd procedures , the systolic blood pressure temporarily decreased to less than 80 mmhg during the procedure . in all of these patients , the temporal reduction of blood pressure was related to drug administration and the blood pressure decreased when the sedatives were administered . in 10 procedures , the systolic blood pressure increased to more than 150 mmhg during a painful portion of the following procedures : 2 ptbd , 3 tdc , 2 ptgbd , 2 pcn and 1 bs . all of the hemodynamic changes responded to increased intravenous fluid and/or to an incremental dose of sedative , analgesic or local anesthetic . when performing procedures , interventional radiologists are responsible for administering safe , effective sedation and analgesia . a 1993 survey of interventional radiologic practices in the british isles ( 15 ) showed that anesthesiologists were present for less than 10% of procedures . even when patients are critically ill , most interventional procedures are performed without the assistance of anesthesiologists ( 7 ) . general guidelines have been published on the use of sedation by non - anesthesiologists ( 10 ) , but no consensus exists for a single drug administration protocol that is suitable for the majority of interventional radiologic cases ( 7 ) . generally , benzodiazepines ( bzds ) and opioids are used to achieve safe and effective sedation and analgesia during radiologic interventional procedures . proper use of these agents improves the patient 's satisfaction , reduces the procedure time and stabilizes the hemodynamic status ; however , incorrect drug administration or inadequate patient monitoring can precipitate disastrous complications and even death ( 16 - 18 ) . all the sedation procedures done in this study were performed by an interventional radiologist with the support of radiology nurses . midazolam , a short - acting bzd , and fentanyl , a short - acting opioid , were used in this study as a sedative and analgesic , respectively . the onset of its effect is within 2 minutes , and it lasts between 45 and 60 minutes ( 6 ) . the short - acting sedative effect with rapid recovery , the low risk of respiratory depression , and the antegrade amnestic effects associated with midazolam make it the favored sedative agent used by non - anesthesiologists to achieve moderate sedation during radiology procedures ( 19 ) . although this agent is relatively safe , more than 80 deaths have been reported after midazolam use for patients undergoing a variety of medical and surgical procedures ( 6 ) . the onset of its effect is 2 - 3 minutes , and the duration of the analgesic effect is between 30 and 60 minutes ( 6 ) . fentanyl is favored by most physicians over the other opioids when performing short , painful procedures because of its rapid onset and suitable duration of effect ( 6 ) . its principal adverse effect is profound respiratory depression due to depression of the carbon dioxide response and elimination of the hypoxemia response ( 10 ) . the durations of the effects of midazolam and fentanyl were quite adequate since less than 60 minutes was required for most of our non - vascular interventional procedures . when used in combination , fentanyl and midazolam provide effective analgesia , sedation and amnesia ( 15 , 20 - 22 ) . however , the two drugs have synergistic effects on respiration ( 18 ) . as of 1989 , there were reports of 49 deaths due to the use of midazolam and opiates in the united states ( 18 ) . respiratory depression or apnea is common during moderate sedation . sedation refers to the use of pharmacologic and nonpharmacologic means to depress the central nervous system and to reduce patient anxiety and irritability ( 23 ) . analgesia is defined as the relief of pain without the intentional production of an altered mental state , the same as in sedation ( 23 ) . moderate sedation / analgesia is the depression of consciousness during which time the patients respond purposefully to verbal commands , either alone or the commands are accompanied by light tactile stimulation ( 6 ) . the patient maintains airway patency and spontaneous ventilation , and the cardiovascular function is usually maintained . moderate sedation provides sufficient anxiolysis and control of unwanted movements during most interventional radiology procedures ( 6 ) . this level of sedation is therefore an appropriate target for procedures that are not supervised by an anesthesiologist . the term conscious sedation continues to be used in both the anesthesia and non - anesthesia literature ( 6 ) . however , this term is no longer included in standards of the american society of anesthesiologists ( asa ) ( 10 ) , and its use is being discouraged because it is imprecise and potentially misleading ( 24 - 26 ) . to achieve moderate sedation in this study , the drugs were administered in a stepwise fashion according to the staged - dose system proposed by skehan et al . the mean total dose of fentany and midazolam used in each procedure to achieve the moderate sedation was 68 g ( range , 54 - 100 g ) and 1.9 mg ( range , 1.7 - 2.4 mg ) respectively . no patient was adequately sedated after step a , while the majorities were sufficiently sedated after step b to commence the procedure ( table 2 ) . fentanyl and midazolam may be the ideal drugs for use in many interventional procedures because they have a rapid onset of action ( usually less than 3 minutes ) and a short duration of effect ( usually less than 60 minutes ) . however , it is unwise to administer both of them simultaneously since they act synergistically ( 14 , 18 , 20 ) . the principal concerns with the combination of fentanyl and midazolam are hypoxemia and/or respiratory arrest ( 7 ) . in one study ( 18 ) , fentanyl administered at a dose of 2 g / kg body weight produced hypoxia ( oxygen saturation < 90% ) in six of 12 healthy volunteers . the addition of midazolam at a dose of 0.05 mg / kg body weight increased the incidence of hypoxia to 11 ( 92% ) volunteers ( 18 ) . there is great inter - patient variation in susceptibility to these drugs and the concept of stepwise administration to achieve moderate sedation is a logical way to avoid hypoxia in the more susceptible patients ( 10 ) . this is consistent with the guidelines of the asa , which recommends that " the ventilatory function should be continually monitored by observation " ( 10 ) . we considered an oxygen saturation of less than 90% to be indicative of clinically significant hypoxemia . below this level , further desaturation occurs along the steep portion of the oxyhemoglobin dissociation curve , and this causes a greater risk of hypoxia - related complications such as cardiac and cerebral ischemia , and arrhythmia ( 10 ) . we stopped all the procedures when the oxygen saturation fell to 90% and we then administered supplemental oxygen at a rate of 4 l / minute via a nasal cannula to prevent clinically significant hypoxemia . the oxygen saturation decreased to 90% or lower in only 14 ( 19.4% ) procedures , and all these patients improved after the administration of supplemental oxygen . in the study by skehan et al . ( 7 ) , the oxygen saturation decreased to 90% or lower in only 15 ( 13% ) patients . continuous monitoring of the oxygen saturation and blood pressure are essential for all patients and if possible , the administration of supplemental oxygen is recommended for all patients . the patients during 68 ( 94.4% ) procedures described pain scores of 4 or less on a scale of 0 to 10 ( fig . 1 ) , with a score of 4 being indicative of discomforting pain . this score represented an acceptable level of analgesia . in total , four patients complained of pain scores in excess of 5 during tdc ( three patients ) and bs ( one patient ) . although the patients appeared to have been moderately sedated , they suddenly indicated pain ; this occurred mainly during track dilatation for choledochoscopy , which is often a very painful procedure . additional drugs were administered in a stepwise fashion to achieve moderate sedation subsequent to the painful episodes . a few other studies have reported on the effectiveness of analgesia during interventional radiologic procedures . ayre - smith ( 22 ) described achieving " favorable results " with fentanyl and midazolam in a preliminary report of 12 patients who underwent unspecified interventional radiologic procedures . miller and wall ( 27 ) reported effective analgesia in all 100 patients who underwent sedation and analgesia for radiologic procedures with a combination of fentanyl and diazepam . in one large study on pain control during interventional biliary procedures ( 2 ) , epidural anesthesia was effective in 91% of the cases , while intravenous sedation was successful in only 50% . however , this study may have been biased against intravenous sedation because most of the patients received single - agent therapy with a narcotic such as meperidine or morphine , without the synergistic benefit of a benzodiazepine . it is important to stress that the effective use of local anesthetic is a vital component of interventional radiology , and particularly for percutaneous non - vascular intervention . sufficient infiltration with a local anesthetic may markedly reduce the requirement for sedation and analgesic ( 28 ) . sufficient use of a local anesthetic may have substantially reduced the pain associated with track dilatation in the three patients of this study for whom the pain was poorly controlled . the major limitation of this study was that we did n't make comparisons with the control groups such as a group using only lidocaine as a local anesthetic and a group using only demerol as a analgesic . another limitation was the small number of cases of djs , bs , gs and rfa ; thus , these procedures were excluded from the statistical analysis . in conclusion , moderate sedation is easy to achieve in patients and it is useful for interventional radiologists . however , all patients undergoing moderate sedation should be continuously monitored to check the vital signs and arterial oxygen saturation . sedation refers to the use of pharmacologic and nonpharmacologic means to depress the central nervous system and to reduce patient anxiety and irritability ( 23 ) . analgesia is defined as the relief of pain without the intentional production of an altered mental state , the same as in sedation ( 23 ) . moderate sedation / analgesia is the depression of consciousness during which time the patients respond purposefully to verbal commands , either alone or the commands are accompanied by light tactile stimulation ( 6 ) . the patient maintains airway patency and spontaneous ventilation , and the cardiovascular function is usually maintained . moderate sedation provides sufficient anxiolysis and control of unwanted movements during most interventional radiology procedures ( 6 ) . this level of sedation is therefore an appropriate target for procedures that are not supervised by an anesthesiologist . the term conscious sedation continues to be used in both the anesthesia and non - anesthesia literature ( 6 ) . however , this term is no longer included in standards of the american society of anesthesiologists ( asa ) ( 10 ) , and its use is being discouraged because it is imprecise and potentially misleading ( 24 - 26 ) . to achieve moderate sedation in this study , the drugs were administered in a stepwise fashion according to the staged - dose system proposed by skehan et al . ( 7 ) . the mean total dose of fentany and midazolam used in each procedure to achieve the moderate sedation was 68 g ( range , 54 - 100 g ) and 1.9 mg ( range , 1.7 - 2.4 mg ) respectively . no patient was adequately sedated after step a , while the majorities were sufficiently sedated after step b to commence the procedure ( table 2 ) . fentanyl and midazolam may be the ideal drugs for use in many interventional procedures because they have a rapid onset of action ( usually less than 3 minutes ) and a short duration of effect ( usually less than 60 minutes ) . however , it is unwise to administer both of them simultaneously since they act synergistically ( 14 , 18 , 20 ) . the principal concerns with the combination of fentanyl and midazolam are hypoxemia and/or respiratory arrest ( 7 ) . in one study ( 18 ) , fentanyl administered at a dose of 2 g / kg body weight produced hypoxia ( oxygen saturation < 90% ) in six of 12 healthy volunteers . the addition of midazolam at a dose of 0.05 mg / kg body weight increased the incidence of hypoxia to 11 ( 92% ) volunteers ( 18 ) . there is great inter - patient variation in susceptibility to these drugs and the concept of stepwise administration to achieve moderate sedation is a logical way to avoid hypoxia in the more susceptible patients ( 10 ) . this is consistent with the guidelines of the asa , which recommends that " the ventilatory function should be continually monitored by observation " ( 10 ) . we considered an oxygen saturation of less than 90% to be indicative of clinically significant hypoxemia . below this level , further desaturation occurs along the steep portion of the oxyhemoglobin dissociation curve , and this causes a greater risk of hypoxia - related complications such as cardiac and cerebral ischemia , and arrhythmia ( 10 ) . we stopped all the procedures when the oxygen saturation fell to 90% and we then administered supplemental oxygen at a rate of 4 l / minute via a nasal cannula to prevent clinically significant hypoxemia . the oxygen saturation decreased to 90% or lower in only 14 ( 19.4% ) procedures , and all these patients improved after the administration of supplemental oxygen . in the study by skehan et al . ( 7 ) , the oxygen saturation decreased to 90% or lower in only 15 ( 13% ) patients . continuous monitoring of the oxygen saturation and blood pressure are essential for all patients and if possible , the administration of supplemental oxygen is recommended for all patients . the patients during 68 ( 94.4% ) procedures described pain scores of 4 or less on a scale of 0 to 10 ( fig . 1 ) , with a score of 4 being indicative of discomforting pain . this score represented an acceptable level of analgesia . in total , four patients complained of pain scores in excess of 5 during tdc ( three patients ) and bs ( one patient ) . although the patients appeared to have been moderately sedated , they suddenly indicated pain ; this occurred mainly during track dilatation for choledochoscopy , which is often a very painful procedure . additional drugs were administered in a stepwise fashion to achieve moderate sedation subsequent to the painful episodes . a few other studies have reported on the effectiveness of analgesia during interventional radiologic procedures . ayre - smith ( 22 ) described achieving " favorable results " with fentanyl and midazolam in a preliminary report of 12 patients who underwent unspecified interventional radiologic procedures . miller and wall ( 27 ) reported effective analgesia in all 100 patients who underwent sedation and analgesia for radiologic procedures with a combination of fentanyl and diazepam . in one large study on pain control during interventional biliary procedures ( 2 ) , epidural anesthesia was effective in 91% of the cases , while intravenous sedation was successful in only 50% . however , this study may have been biased against intravenous sedation because most of the patients received single - agent therapy with a narcotic such as meperidine or morphine , without the synergistic benefit of a benzodiazepine . it is important to stress that the effective use of local anesthetic is a vital component of interventional radiology , and particularly for percutaneous non - vascular intervention . sufficient infiltration with a local anesthetic may markedly reduce the requirement for sedation and analgesic ( 28 ) . sufficient use of a local anesthetic may have substantially reduced the pain associated with track dilatation in the three patients of this study for whom the pain was poorly controlled . the major limitation of this study was that we did n't make comparisons with the control groups such as a group using only lidocaine as a local anesthetic and a group using only demerol as a analgesic . another limitation was the small number of cases of djs , bs , gs and rfa ; thus , these procedures were excluded from the statistical analysis . in conclusion , moderate sedation is easy to achieve in patients and it is useful for interventional radiologists . however , all patients undergoing moderate sedation should be continuously monitored to check the vital signs and arterial oxygen saturation . administering supplemental oxygen
objectivethe purpose of this study was to prospectively characterize the safety and effectiveness of moderate sedation / analgesia for performing radiologic non - vascular abdominal intervention.materials and methodsduring a 3-month period , a total of 63 adult patients with a mean age of 64 years ( range : 27 - 82 ) underwent moderate sedation for 72 radiologic non - vascular interventional procedures . 
 a combination of fentanyl citrate and midazolam hydrochloride , based on the patient 's body weight , was intravenously administered until the patient was drowsy and tranquil . 
 the adverse events associated with this moderate sedation were assessed . 
 the visual analog scale format was used to measure the subjective feelings of the patient 's pre - procedural anxiety and intraprocedural pain.resultsthe mean total dose per kilogram of body weight of fentanyl used in ptbd was 1.148 g , it was 1.157 g for ptgbd , 1 g for ad , 1 g for pcn , 1.641 g for tdc , 1 g for djs , 2 g for bs , 1 g for gs and 2 g for rfa . 
 the mean total dose per kilogram of body weight of midazolam was 0.035 mg in ptbd , ptgbd , ad , pcn , djs , gs and rfa , 0.039 mg in tdc , and 0.043 mg in bs . 
 a temporary reduction of systolic blood pressure to less than 80 mmhg was observed during 5 procedures ( 6.9% ) , whereas a temporary elevation of systolic blood pressure above 150 mmhg was observed during 10 procedures ( 13.8% ) . a reduction of arterial oxygen saturation to less than 90% 
 was observed during 14 procedures ( 19.4% ) . none of the patients required pharmacologic reversal agents or cardiopulmonary resuscitation . the mean anxiety score recorded before all procedures was 5.2 ( distressing ) . 
 the mean pain score during the procedure , which was recorded after all procedures , was 2.9 ( mild).conclusionmoderate sedation allows performance of safe and effective radiologic non - vascular intervention , and it is also easy for an interventional radiologist to use . 
 the patients should be continuously monitored to check their vital signs and arterial oxygen saturation during the procedures .