Capnography accurately detects apnea during monitored anesthesia care

Apnea and airway obstruction are common during monitored anesthesia care (MAC). Because their early detection is essential, we sought to measure the efficacy of capnography as an indicator of apnea during MAC at a variety of oxygen flow rates compared with thoracic impedance. Anesthesia care providers using standard American Society of Anesthesiologists monitors were blinded to capnography and thoracic impedance monitoring. Ten (26%) of the 39 patients studied developed 20 s of apnea; none was detected by the anesthesia provider, but all were detected by capnography and impedance monitoring. There was no difference in detection rates between the two methods. Higher oxygen flow rates decreased the amplitude of the capnograph but did not interfere with apnea detection. This pilot study revealed that apnea of at least 20 s in duration may occur in every fourth patient undergoing MAC. Although these episodes were undetected by the anesthesia provider, they were reliably detected by both capnography and respiratory plethysmography. Monitoring of nasal end-tidal CO(2) is an important way to improve safety in patients undergoing MAC.     

The cost-effectiveness of methohexital versus propofol for sedation during monitored anesthesia care

We designed this study to test the hypothesis that methohexital is a cost-effective alternative to propofol for sedation during local anesthesia. Sixty consenting women undergoing breast biopsy procedures under local anesthesia were randomly assigned to receive an infusion of either propofol (50 microg x kg(-1) x min(-1)) or methohexital (40 microg x kg(-1) x min(-1)). The sedative infusion rate was titrated to maintain an observer's assessment of alertness/sedation (OAA/S) score of 3 (with 1 = awake/alert to 5 = asleep). Fentanyl 25 microg i.v. was administered as a "rescue" analgesic during the operation. We assessed the level of sedation (OAA/S score), vital signs, time to achieve an OAA/S score of 3 at the onset and a score of 1 after discontinuing the infusion, discharge times, perioperative side effects, and patient satisfaction. The direct cost of methohexital was lower than that of propofol, based on the milligram dosage infused during the operation. The sedative onset (to achieve an OAA/S score of 3) and the recovery (to return to an OAA/S score of 1) times, as well as discharge times, did not differ between the two groups. Patients receiving methohexital had a significantly lower incidence of pain on initial injection compared with those receiving propofol (10% vs 23%). Because the use of methohexital (29.4 +/- 2.7 microg x kg(-1) x min(-1)) for sedation during breast biopsy procedures has a similar efficacy and recovery profile to that of propofol (36.8 +/- 15.9 microg x kg(-1) x min(-1)) and is less costly based on the amount infused, it seems to be a cost-effective alternative to propofol for sedation during local anesthesia. However, when the cost of the drug infused and drug wasted was calculated, there was no difference in the overall drug cost. Implications: When administered to maintain a stable level of sedation during local anesthesia, methohexital is an acceptable alternative to propofol. However, the overall drug costs were similar with the two drugs.     

Remifentanil-propofol versus fentanyl-propofol for monitored anesthesia care during hysteroscopy

STUDY OBJECTIVE: To compare the efficacy of remifentanil-propofol with that of fentanyl-propofol for monitored anesthesia care during hysteroscopy. DESIGN: Prospective, randomized study. SETTING: Operating room and postanesthesia care unit of a university hospital. PATIENTS: 30 ASA physical status I and II adult patients undergoing hysteroscopic procedures. INTERVENTIONS: After propofol infusion, patients received a bolus of remifentanil (group R, 0.5 mug/kg) or fentanyl (group F, 1 mug/kg) 4 minutes before starting the procedure and then received a continuous infusion of remifentanil (group R, 0.05 mug/kg per min) or bolus doses of fentanyl (group F, 0.5 mug/kg). MEASUREMENTS AND MAIN RESULTS: Patients in group R had lower pain scores than patients in group F (0-0 vs 0-7, P < 0.05) and more stable blood pressures (74 +/- 15 vs 85 +/- 9 mmHg, P < 0.05) one minute after the start of the procedure. However, no differences were observed in other variables (recovery profiles and satisfaction scores). CONCLUSION: Remifentanil seems to be a safe and effective analgesic adjunct for monitored anesthesia care of hysteroscopic surgery.     

The effects of a small-dose ketamine-propofol combination on tourniquet-induced ischemia-reperfusion injury during arthroscopic knee surgery

Study ObjectiveTo determine the effects of a small-dose ketamine-propofol combination used for sedation during spinal anesthesia on tourniquet-induced ischemia-reperfusion injury.Study DesignProspective randomized study.SettingTraining and research hospital.Patients60 adult, ASA physical status 1 and 2 patients, ages 20–60 years, scheduled for elective arthroscopic knee surgery for meniscal and chondral lesions.InterventionsThe initial hemodynamic parameters were recorded and blood samples were collected at baseline (T1); then spinal anesthesia was performed. In Group I (n=30), a combination of 0.5 mg/kg/hr of ketamine and 2 mg/kg/hr of propofol was administered; Group II (n=30) received an equivalent volume of saline as an infusion. A pneumatic tourniquet was applied.MeasurementsMalondialdehyde (MDA), superoxide dismutase (SOD), and catalase levels were measured one minute before tournique deflation in the ischemic period (T2), then 5 (T3) and 30 (T4) minutes following tourniquet deflation in the reperfusion period.Main ResultsNo differences were noted between groups in hemodynamic data (P > 0.05) or SOD levels (P > 0.05). In Group I, MDA levels at T2 were lower than in Group II (P < 0.05). In Group I, catalase levels were lower at T2 and T4 than they were in Group II (P < 0.05).ConclusionSmall-dose ketamine-propofol combination may be useful in reducing tourniquet-induced ischemia-reperfusion injury in arthroscopic knee surgery.     

Clinical assessment of target-controlled infusion of propofol during monitored anesthesia care

PURPOSE: To determine the plasma concentrations of propofol required to achieve different levels of sedation during monitored anesthesia care. METHODS: Sixty ASA I-II, 18-65 yr-old patients, received a target-controlled continuous iv infusion of propofol. The target plasma concentration of propofol (Cpt) was initially set at 0.4 microg x ml(-1). Two minutes after calculated equilibrium between plasma and effect-site concentrations, the Cpt of propofol was increased by 0.2 microg x ml(-1) steps until the patient showed no reaction to squeezing the trapezius. The level of sedation was assessed immediately before each increase in propofol Cpt using the Observer's Assessment of Alertness/Sedation (OAA/S) scale. RESULTS: The Cpt of propofol required to induce lethargic response to name was 1.3 microg x ml(-1) (5 degrees and 95 degrees percentiles: 1.0 - 1.8 microg x ml(-1)), to obtain response after loud and repeated calling name was 1.7 microg x ml(-1) (1.2 - 2.2 microg x ml(-1)), to obtain response after prodding or shaking was 2.0 microg x ml(-1) (1.6 - 2.6 microg x ml(-1)), to obtain response after squeezing the trapezius was 2.4 microg x ml(-1) (1.8 - 3.0 microg x ml(-1)). Patients showed no response after squeezing the trapezius at 2.8 microg x ml(-1) (2.0 - 3.6 microg x ml(-1)). Correlation between Cpt propofol and sedation scores were r = 0.76, P < 0.0001. CONCLUSIONS: Target-controlled infusion of propofol provided easy and safe management of intraoperative sedation, allowing fast and predictable deepening in the level of sedation, while minimizing systemic side effects of intravenous sedation due to the minimal risk of overdosing the drug.     

Bispectral Index and the incidence of apnea during monitored anesthesia care

Purpose:

The Bispectral Index (BIS) provides an estimate of depth of consciousness during sedation. If apnea can be shown to correlate with BIS, then a potential improvement in safety during MAC/sedation may be achieved.

Scope:

Ninety-nine patients undergoing MAC anesthesia were monitored with BIS for level of consciousness, and capnography for apnea detection. The anesthesia provider was blinded to BIS and capnography data. Forty-nine percent of subjects experienced apnea independent of medical history, procedure, or medication. BIS immediately preceding apneic episodes (55 ± 18) was frequently lower than that recommended for an upper limit during general anesthetics (<60). The incidence increased as depth of consciousness decreased with a 50% likelihood of developing apnea at a BIS of 56.

Conclusions:

The incidence of apnea during MAC is high, and incidence increases as BIS decreases.     

A comparison of fentanyl-propofol with a ketamine-propofol combination for sedation during endometrial biopsy

STUDY OBJECTIVE: The purpose of this study was to compare the clinical activities of ketamine and fentanyl when used in combination with propofol for outpatients undergoing endometrial biopsy. The investigated parameters were respiration, sedation, recovery rate, side effects, time to discharge, and patient satisfaction. DESIGN: Prospective, randomized, double-blind study. SETTING: University hospital. PATIENTS: Forty American Society of Anesthesiologists physical status I and II patients (age range 38-61 years) scheduled for elective endometrial biopsy. INTERVENTIONS: Patients received intravenous bolus doses of either fentanyl 1 microg/kg and propofol 1 mg/kg in (group 1 n = 20) or ketamine 0.5 mg/kg and propofol 1 mg/kg in (group 2 n = 20). MEASUREMENTS: Heart rate, systolic and diastolic blood pressure, respiratory rate, and peripheral O(2) saturation were monitored in all patients. Depth of sedation was assessed by the Ramsay sedation score. The Aldrete score was used for postoperative recovery evaluation. The time to Aldrete score >/=8, side effects, and time to discharge were recorded. MAIN RESULTS: Respiratory depression was observed in 5 patients from group 1 and 1 patient from group 2, but the difference was not significant (P > .05). Nausea, vertigo, and visual disturbances were more frequent in group 2 (P < .05). The time to Aldrete score >/=8 was similar in the 2 groups (6.2 +/- 3.5 minutes in group 1 and 7.0 +/- 3.1 minutes in group 2); the time to discharge was significantly longer in group 2 (71.2 +/- 9.7 minutes in group 1 and 115.2 +/- 25.6 minutes in group 2). Frequency of patient satisfaction was 95% in group 1 and 60% in group 2. CONCLUSIONS: Hemodynamic change and degrees of sedation showed that fentanyl-propofol and ketamine-fentanyl combinations can be used safely in patients undergoing endometrial biopsy. However, with regard to side effects and patient satisfaction, the fentanyl-propofol was superior.     

Optimal target concentration of remifentanil during cataract surgery with monitored anesthesia care

Study objectiveTo determine the effect-site target concentration (C_et) of remifentanil that provides optimal conditions for patients and operators during cataract surgery during monitored anesthesia care using a target controlled infusion (TCI) of propofol and remifentanil.DesignProspective, randomized, double-blinded study.SettingOperating room and postoperative recovery area of a university-affiliated hospital.Patients66 adult, ASA physical status I, II, and III patients undergoing cataract surgeryInterventionsGroup I received C_et of remifentanil 0.5 ng/mL; Group 2 received C_et of remifentanil one ng/mL; and Group 3 received C_et of remifentanil 1.5 ng/mL. After giving TCI propofol (C_et; one μg/mL) - remifentanil, an ophthalmologist administered topical anesthesia.Measurements and main resultsIntraoperative hemodynamics, pain scores, sedation scores, patient satisfaction scores, and operators’ satisfaction scores regarding surgical conditions were recorded. No statistical differences in heart rate or mean blood pressure were detected among the three groups during surgery. Pain scores (Group 1: 31.9 ± 17.9 vs. Group 2: 11.8 ± 7.7 and Group 3: 11.8 ± 7.7; P < 0.05) were higher and patient satisfaction scores (Group 1: 4.7 ± 0.8 vs. Group 2: 5.4 ± 0.4 and Group 3: 5.5 ± 0.4; P < 0.05) were lower in Group 1 than Groups 2 and 3. On the other hand, surgeon satisfaction was lowest in Group 3 (Group 3: 2.9 ± 1.3 vs. Group 1: 4.7 ± 0.4 and Group 2: 4.6 ± 0.7; P < 0.05) due to ocular movement.ConclusionC_et values of remifentanil and propofol of one ng/mL and one μg/mL, respectively, appear to provide optimal conditions for patients and operators during cataract surgery using monitored anesthesia care with TCI.     

瑞芬太尼复合小剂量咪达唑仑用于ERCP监护性麻醉的研究

目的观察瑞芬太尼复合小剂量咪达唑仑用于内镜逆行胰胆管造影术（ERCP）监护性麻醉的效果和安全性。方法选择66例ASAⅠ～Ⅲ级、年龄35～79岁拟在监护性麻醉下行ERCP的患者,随机均分为单纯瑞芬太尼组（R组）和瑞芬太尼复合小剂量咪达唑仑组（RM组）。R组首先持续输注瑞芬太尼0.2μg·kg^-1·min^-15min,随后减为0.15μg·kg^-1·min^-1,RM组在手术开始前静注咪达唑仑0.02mg/kg,其余用药同R组。观察两组患者麻醉前（T₀）、手术开始时（T₁）、手术开始后 min（T₂）、10min（T₃）和术毕（T₄）时MAP、HR、RR、SpO₂、脑电双频指数（BIS）以及术后改良Aldrete镇静评分、操作者对麻醉效果的满意度评分和不良反应发生情况,并记录手术操作时间和麻醉时间。结果与T₀时比较,T₁、T₂时R组MAP均明显升高（P<0.05）;T₂～T₄时两组HR均明显加快,T₁时R组HR明显快于T₀时和RM组。T₁～T₄时两组BIS均明显低于T₀时,且T₁～T₃时RM组BIS明显低于R组（P<0.05）。术后RM组遗忘评分明显高于R组（P<0.05）。R组手术操作者满意度评分明显高于RM组（P<0.05）;术毕时R组的改良Aldrete评分明显高于RM组（P<0.05）。结论瑞芬太尼0.2 μg·kg^-1·min^-1用于ERCP实施监护性麻醉可获得满意的麻醉效果,且安全性佳。     

Comparison of a lower-lipid propofol emulsion with the standard emulsion for sedation during monitored anesthesia care

BACKGROUND: The currently used emulsion formulations of 1% propofol contain 10% soybean oil. However, a new emulsion of 1% propofol (Ampofol) containing 50% less lipid has recently become available for clinical investigation. This study was designed to compare the pharmacodynamic properties of Ampofol with those of a standard formulation (Diprivan) when administered for intraoperative sedation. METHODS: Sixty healthy outpatients undergoing minor operations with local anesthesia were randomly assigned to receive either Ampofol (n = 31) or Diprivan (n = 29) for intravenous sedation. The sedation was initiated with an intravenous loading dose of propofol, 0.75 mg/kg, followed by an initial infusion rate of 50 microg x kg(-1) x min(-1) to achieve an Observer's Assessment of Alertness/Sedation score of 3. The targeted level of sedation was maintained with a variable-rate propofol infusion during the operation. The onset times to achieving a sedation score of 3, the severity of pain on injection of the loading dose, intraoperative hemodynamic variables, and electroencephalographic Bispectral Index values were recorded. In addition, recovery times, postoperative pain and nausea, and patient satisfaction with the sedative medication were assessed. RESULTS: There were no significant differences between Ampofol and Diprivan with respect to onset times, dosage requirements, Bispectral Index values, hemodynamic variables, recovery times, or patient satisfaction scores. The incidence of moderate pain on injection was higher in the Ampofol group (26%vs. 7% with Diprivan; P < 0.05). CONCLUSIONS: Ampofol was equipotent to Diprivan with respect to its sedative properties during monitored anesthesia care. Although both groups received pretreatment with intravenous lidocaine, Ampofol was associated with more pain on injection.     

Breast augmentation under general anesthesia versus monitored anesthesia care: a retrospective comparative study

Breast augmentation is one of the leading esthetic surgeries, enjoying high satisfaction rates. Pain, nausea, and vomiting are frequent shortcomings of the immediate postoperative period. The aim of this study was to compare breast augmentation from the anesthetic point of view: general anesthesia (GA) versus monitored anesthesia care (MAC). The charts of 115 patients were reviewed in this retrospective study performed over a period of 2 years. Sixty-nine women chose to have the surgery done under MAC, and 46 under GA. Statistically significant differences were noted in both postoperative hospital stay (16.1 +/- 6.78 hours vs. 11.7 +/- 6.10 hours) and frequency of vomiting (mean, 0.5 vs. 0.22 times per patient) after GA and MAC, respectively (Mann-Whitney, P < 0.01). Postoperative pain, assessed using the visual analog scale, was significantly higher (mean visual analog scale, 5 vs. 3.27) when the prosthesis was placed in the submuscular plane compared with the subglandular plane (Mann-Whitney, P = 0.043). When offered a choice, more women preferred MAC over GA for their breast augmentation procedure. Less vomiting and shorter postoperative hospitalization were prominent in the MAC group.     

Postoperative analgesia in herniorrhaphy with local anesthesia and monitored anesthesia care

Summary In this study the authors evaluated the grade of acceptance and the operating conditions of unilateral primary herniorrhaphy under local anesthesia and monitored anesthesia care (MAC). The amount of pain in the immediate postoperative period was assessed and the efficacy of treatment using a popular non-opiate analgesic, magnesic metamizol, by the oral route was studied. In a period of six months 63 consecutive patients were operated on by the same surgeon using the same technique of hernia repair (Shouldice technique) with local infiltration anesthesia supplemented by MAC in the form of conscious sedation. A mixture of 300 mg of plain mepivacaine and 50 mg of plain bupivacaine was used for infiltration. A standard dose of fentanyl 0.10 mg and midazolam 2 mg was used for conscious sedation. Propofol in continuous infusion was also employed. The average dose of propofol varied from 1–3 mg/kg/h. Conscious level was assessed using a five-point sedation score. A level-3 end point was persued (closed eyes, but answer verbal orders). Pain intensity in the postoperative period was measured by the visual analogue scale (VAS) and the verbal pain scale (VPS), based on the McGill pain questionnaire. The operating conditions were excellent in all cases except in three patients. In no case conversion to general anesthesia was necessary. In the postoperative period, 5 patients (8%) never felt pain and 58 (92%) felt pain on the average 4 hours 36 minutes after the local infiltration (VAS=2.5; VPS=1.45). Of the 58 patients 49 took the first dose of oral analgesic 6 hours 40 minutes after infiltration (VAS=4; VPS=1.97). All patients were satisfied with the anesthetic-surgical technique and were ready to repeat the experience. However, when the patients took the second dose of oral analgesic 28% of them had moderate pain and 9% severe pain. Our conclusions are that local infiltration with MAC is a valid and satisfying experience for both the patient and the surgeon. Nevertheless, further attempts should be made to better the postoperative pain relief when the oral route is elected.     

Fast-tracking after immersion lithotripsy: general anesthesia versus monitored anesthesia care

Both monitored anesthesia care (MAC) and general anesthesia (GA) offer advantages over epidural anesthesia for immersion lithotripsy. We compared propofol-based MAC and desflurane-based GA techniques for outpatient lithotripsy. After receiving midazolam 2 mg IV, 100 subjects were randomly assigned to one of two anesthetic treatment groups. In the MAC group, propofol 50-100 microg. kg(-1). min(-1) IV was titrated to maintain an observer's assessment of alertness/sedation score of 2-3 (5 = awake/alert to 1 = asleep). Remifentanil 0.05 microg.kg(-1). min(-1) IV supplemented with 0.125 microg/kg IV boluses, was administered for pain control. In the GA group, anesthesia was induced with propofol 1.5 mg/kg IV and remifentanil 0.125 microg/kg IV and maintained with desflurane (2%-4% inspired) and nitrous oxide (60%). Tachypnea (respiratory rate >20 breaths/min) was treated with remifentanil 0.125 microg/kg IV boluses. In the GA group, droperidol (0.625 mg IV) was administered as a prophylactic antiemetic. Recovery times and postoperative side effects were assessed up to 24 h after the procedure. Compared with MAC, the use of GA reduced the opioid requirement and decreased movements and episodes of desaturation (<90%) during the procedure. Although the GA group took longer to return to an observer's assessment of alertness/sedation score of 5, discharge times were similar in both groups. We conclude that GA can provide better conditions for outpatient immersion lithotripsy than MAC sedation without delaying discharge. IMPLICATIONS: A desflurane-based general anesthetic technique using the cuffed oropharyngeal airway device was found to be a highly acceptable alternative to propofol-based monitored anesthesia care sedation for outpatient immersion lithotripsy.