Frequent hypoxemia and apnea after sedation with midazolam and fentanyl

Midazolam: a review of therapeutic uses and toxicity

Midazolam is a familiar agent commonly used in the emergency department to provide sedation prior to procedures such as laceration repair and reduction of dislocations. Midazolam is also effective in the treatment of generalized seizures, status epilepticus, and behavioral emergencies, particularly when intravenous access is not available. Midazolam is often employed as an induction agent for rapid sequence endotracheal intubation. Midazolam has a rapid onset of action following intravenous, intramuscular, oral, nasal, and rectal administration. Only 50% of an orally administered dose reaches the systemic circulation due to extensive first-pass metabolism. Midazolam is metabolized by the cytochrome P450 enzyme system to several metabolites including an active metabolite, alpha-hydroxymidazolam. Cytochrome P450 inhibitors such as cimetidine can profoundly reduce the metabolism of midazolam. Midazolam has a half-life of approximately 1 h, but this half-life may be prolonged in patients with renal or hepatic dysfunction. Midazolam has been associated with respiratory depression and cardiac arrest when used in combination with an opioid, particularly in the elderly, although all ages are at risk for respiratory depression. Midazolam is relatively free of side effects when used alone and offers several advantages over traditional pharmacological agents such as chloral hydrate and the combination of meperidine, chlorpromazine, and promethazine. Hiccups, cough, nausea, and vomiting are the most commonly reported adverse effects. Many of the adverse effects associated with midazolam can be reversed rapidly by the administration of flumazenil, a competitive benzodiazepine receptor antagonist. Midazolam is a safe and effective agent for providing sedation in the emergency department.

Outpatient general anesthesia: a comparison of a combination of midazolam plus propofol and propofol alone

STUDY OBJECTIVE

To compare the hemodynamics, efficacy, safety, and postoperative recovery of patients following the use of either midazolam plus propofol or placebo plus propofol for induction and maintenance of general anesthesia for outpatient surgical procedures of less than two hours' duration.

DESIGN

Prospective, parallel, randomized, double-blind, placebo-controlled, multicenter study.

SETTING

Ten outpatient surgery centers.

PATIENTS

203 ASA physical status I, II, and III patients undergoing various outpatient surgical procedures.

INTERVENTIONS

Patients were randomly assigned to one of the two treatment groups. For induction of anesthesia, Group 1 received midazolam (0.077 +/- 0.0021 mg/kg) via slow intravenous (IV) push plus continuous infusion propofol (provided in a concentration of 5 mg/ml), and Group 2 received placebo plus full-concentration (10 mg/ml) propofol. Thereafter, Group 1 received half-concentration propofol and Group 2 received full-concentration propofol via continuous infusion for maintenance of anesthesia. Investigators administered doses of study medication in a blinded fashion as required to achieve the desired clinical effect. Drugs used to maintain anesthesia were restricted to study drug, short-acting opioids, and nitrous oxide. Succinylcholine chloride or vecuronium were used to facilitate intubation of study patients.

MEASUREMENTS AND MAIN RESULTS

There were no statistically significant differences between the midazolam/propofol and placebo/propofol groups with respect to the mean (SE) decrease in mean arterial pressure from pre-dose to time of intubation or from time of intubation to initiation of surgery; the mean (SE) time required from initiation of study medication to completion of intubation [6.7 (0.23) minutes vs. 7.0 (0.26) minutes, respectively]; or the mean (SE) amount of propofol required to induce and maintain anesthesia [6.03 (0.329) mg/kg vs. 9.71 (0.489) mg/kg, respectively]. There was no significant difference between the two treatment groups in the time to recovery following the completion of surgery (as assessed by Aldrete Post Anesthesia Recovery Score). Most patients (approximately 79%) in both groups rated the quality of the anesthetic regimen as excellent; however, as assessed by patient questionnaires, fewer patients in the midazolam/ propofol group were able to recall the events surrounding their surgical procedure as compared with patients in the placebo/ propofol group (89.2% vs. 77.9%; p = 0.022). There were no differences between the two groups with respect to the frequency or severity of adverse events.

CONCLUSIONS

Concomitantly administered midazolam and reduction-concentration propofol did not exacerbate the well-described hypotensive effects of full-strength propofol during induction of anesthesia. The time to intubation was equivalent with the combination of midazolam/propofol as compared with propofol alone. Recovery from the two regimens was not significantly different. However, reduced recall of perioperative events was observed more often in the midazolam/propofol regimen compared with propofol alone.

A comparison of propofol and remifentanil during monitored anesthesia care

STUDY OBJECTIVE

To compare remifentanil, an esterase-metabolized opioid, to a standard propofol-based sedation technique for monitored anesthesia care (MAC).

DESIGN

Non-randomized, open label.

SETTING

University hospital.

PATIENTS

44 healthy female outpatients undergoing breast biopsy procedures under local anesthesia.

INTERVENTIONS

All patients received intravenous (IV) midazolam 2 mg, followed by a continuous infusion of either propofol 75 micrograms/kg/min, or remifentanil 0.1 microgram/kg/min, which was subsequently titrated to maintain optimal patient comfort without respiratory depression. Surgical-related pain was treated by injecting additional local anesthetic solution and "rescue" boluses of fentanyl 25 micrograms IV.

MEASUREMENTS AND MAIN RESULTS

Sedation, pain, and discomfort were monitored using standardized rating scales at 1 to 5 minute intervals. Recovery times were measured from the end of the study drug infusions. Propofol resulted in significantly higher median sedation scores compared with remifentanil, with 73% of patients requiring a decrease in the propofol infusion rate because of "excessive" sedation. Local anesthetic requirements, pain, and discomfort scores during surgery were similar in both groups. Remifentanil resulted in greater respiratory depression compared with propofol, with decreases in the remifentanil infusion rate required by 41% of patients because of a slow respiratory rate (< 8 bpm) and/or oxygen desaturation measured by pulse oximetry (SpO2 < 90%). Median times to ambulation and to being judged "fit for discharge" were significantly shorter following propofol (40 and 47 minutes, respectively) compared with remifentanil (52 and 58 minutes, respectively).

CONCLUSION

Remifentanil provided comparable intraoperative conditions and patient comfort at a lower sedation level compared with propofol. However, remifentanil was associated with greater respiratory depression and a longer time to home readiness.

Evaluation of ketorolac in children with forearm fractures

OBJECTIVES

To evaluate ketorolac for pain relief and an opioid-sparing effect in children with forearm fractures necessitating reduction.

METHODS

A prospective, randomized, double-blind study was conducted at an urban children's hospital ED. A convenience sample of children aged 3-18 years with isolated forearm fractures was studied. None received prior pain medication. A 10-point visual analog scale (VAS) was used to assess pain at the time of study entry and prior to sedation/analgesia. The Children's Hospital of Eastern Ontario's Pain Score (CHEOPS), a 13-point behavioral score, was used to assess pain during sedation. Patients received either IV ketorolac (K), 1 mg/kg, or saline (S) after entry into the study. After a minimum of 20 minutes, pain was reassessed and supplemental analgesia/sedation administered. A standard dose of midazolam, 0.1 mg/kg to a maximum of 6 mg, was given to all patients, and fentanyl was titrated at 1-microgram/kg increments based on patient need. Once the patient was comfortable, reduction was performed and a reduction CHEOPS score assigned.

RESULTS

For the 34 study children (17 K, 17 S), there was no difference in sex or mean age between the groups. Mean total doses of fentanyl were 2.26 micrograms/kg in the K group and 2.85 micrograms/kg in the S group (p = 0.07). The median changes in VAS score before and after receiving the study drug were -1.13 K and -0.18 S (p = 0.06). The median CHEOPS score was 10 for both groups. Seven of the 17 patients in the S group required the maximum fentanyl dose (4 micrograms/kg), compared with 2 of 17 in the K group (p = p.06).

CONCLUSIONS

Although ketorolac seems to add to patient comfort in children with forearm fractures, it does not have a significant opioid-sparing effect. Ketorolac showed a trend toward pain relief, but statistical significance was not reached.

Sedation and analgesia for colonoscopy: patient tolerance, pain, and cardiorespiratory parameters

BACKGROUND

Colonoscopy is generally performed with the patient sedated and receiving analgesics. However, the benefit of the most often used combination of intravenous midazolam and pethidine on patient tolerance and pain and its cardiorespiratory risk have not been fully defined.

METHODS

In this double-blind prospective study, 150 outpatients undergoing routine colonoscopy were randomly assigned to receive either (1) low-dose midazolam (35 micrograms/kg) and pethidine (700 micrograms/kg in 48 patients, 500 micrograms/kg in 102 patients), (2) midazolam and placebo pethidine, or (3) pethidine and placebo midazolam.

RESULTS

Tolerance (visual analog scale, 0 to 100 points: 0 = excellent; 100 = unbearable) did not improve significantly more in group 1 compared with group 2 (7 points; 95% confidence interval [-2-17]) and group 3 (2 points; 95% confidence interval [-7-12]). Similarly, pain was not significantly improved in group 1 as compared with the other groups. Male gender (p < 0.001) and shorter duration of the procedure (p = 0.004), but not amnesia, were associated with better patient tolerance and less pain. Patient satisfaction was similar in all groups. Oxygen desaturation and hypotension occurred in 33% and 11%, respectively, with a similar frequency in all three groups.

CONCLUSIONS

In this study, the combination of low-dose midazolam and pethidine does not improve patient tolerance and lessen pain during colonoscopy as compared with either drug given alone. When applying low-dose midazolam, oxygen desaturation and hypotension do not occur more often after combined use of both drugs. For the individual patient, sedation and analgesia should be based on the endoscopist's clinical judgement.

Choices in sedation: the balanced sedation technique

Patients undergoing surgery under regional anaesthesia may be anxious, uncomfortable or in pain. Therefore, effective sedation throughout the procedure is an important aspect of patient management. The balanced sedation technique uses combinations of sedatives to meet the anxiolytic and analgesic needs of the individual patient. For example, benzodiazepines are effective anxiolytics, while propofol can be used to provide a suitable level of sedation, especially in patients who have expressed a wish to remain asleep during the procedure. Analgesics should be considered only in those patients who are likely to experience pain during the procedure. Basic measures to increase the comfort of the patient and to facilitate the effect of pharmacological methods include supplementary non-pharmacological techniques, for example the use of a soft mattress to prevent back pain, infusion of warmed fluids and a warm operating atmosphere. This may extend to the opportunity for patients to listen to music if they have a fear of the sounds associated with the operating room, such as technical discussions by surgical staff or the sound of surgical instruments being used and discarded. The balanced sedation technique can, therefore, help to achieve the ideal goal of a comfortable patient who is free from anxiety and pain, and can sleep if desired.

A prospective evaluation of the safety and efficacy of methohexital in the emergency department

A prospective observational study in an inner-city teaching hospital was conducted to evaluate the safety and efficacy of intravenous methohexital (MTX) in the emergency department (ED). Pulse oximetry, vital signs and Glasgow Coma Scale (GCS) scores were recorded serially for 30 minutes after the administration of MTX to 76 adult patients. Likert scales of 1 to 5 were used to record the physician's assessment of the adequacy of sedation and the patient's assessments of recall and pain of the procedure. Patients received an average of 88 +/- 21 mg of MTX for a variety of indications (orthopedic procedures, 78%; sedation for other procedures, 14%; intubation, 5%; and psychiatric interview, 3%). No patient had clinically significant changes in heart rate or blood pressure. Eight (10.5%) had apnea, although only one patient had oxygen saturations of less than 90%. Each episode was brief and easily managed with bag-valve-mask ventilation. Risk factors for apnea included a history of alcoholism (P = .0003) and recent recreational narcotic use (P = .0139). Patients were maximally sedated in an average of 37 +/- 42 seconds. In the subset of initially alert patients, GCS scores decreased from 15 at baseline to 5.9 +/- 4.5. The physician's assessment of the adequacy of sedation was excellent (4.7 +/- 0.7). Patients reported little recall (1.3 +/- 0.9) or pain (1.3 +/- 0.8). It was concluded that MTX caused clinically insignificant changes in hemodynamics or oxygenation, although respiratory depression did occur; significant respiratory depression was brief and easily managed. MTX provided rapid and excellent levels of sedation with little or no patient recall or pain.

Self-hypnotic relaxation during interventional radiological procedures: effects on pain perception and intravenous drug use

The authors evaluated whether self-hypnotic relaxation can reduce the need for intravenous conscious sedation during interventional radiological procedures. Sixteen patients were randomized to a test group, and 14 patients were randomized to a control group. All had patient-controlled analgesia. Test patients additionally had self-hypnotic relaxation and underwent a Hypnotic Induction Profile test. Compared to controls, test patients used less drugs (0.28 vs. 2.01 drug units; p < .01) and reported less pain (median pain rating 2 vs. 5 on a 0-10 scale; p < .01). Significantly more control patients exhibited oxygen desaturation and/or needed interruptions of their procedures for hemodynamic instability. Benefit did not correlate with hypnotizability. Self-hypnotic relaxation can reduce drug use and improve procedural safety.

End-tidal PCO2 monitoring via nasal cannulae in pediatric patients: accuracy and sources of error

OBJECTIVE

To assess the correlation and accuracy of end-tidal PCO2 (PetCO2) sampled via nasal cannulae in pediatric patients by comparison to the criterion standard PaCO2, and to identify sources of error during PetCO2 monitoring via nasal cannulae.

METHODS

PetCO2 was monitored continuously by sampling end-tidal gas through nasal cannulae that had been designed and manufactured for this purpose in spontaneously breathing children undergoing conscious or deep sedation during either cardiac catheterization (n = 43) or critical care (n = 54). When both the capnographic wave form and the PetCO2 value had been stable for at least 10 minutes, the PetCO2 value was recorded while blood was drawn from an indwelling arterial line for PaCO2 measurement. The effects of age, weight, respiratory rate, oxygen delivery system, airway obstruction, mouth breathing, and cyanotic heart disease were evaluated by linear regression analysis and calculation of absolute bias (PaCO2-PetCO2).

RESULTS

Mouth breathing, airway obstruction, oxygen delivery through the ipsilateral nasal cannula, and cyanotic heart disease adversely affected accuracy. In patients without those factors, PetCO2 correlated well with PaCO2 (R2 = 0.994), and absolute bias was 3.0 +/- 1.8 mmHg.

CONCLUSIONS

Several factors-some controllable and all recognizable-affect the accuracy of PetCO2 monitored via nasal cannulae in pediatric patients. When these factors are not present, PetCO2 correlates well with PaCO2 and appears to be a useful monitor of ventilatory status during conscious or deep sedation.

Sedation for the critically ill neurologic patient

OBJECTIVE

To review the scientific basis for sedation of critically ill neurologic patients by summarizing the distinct neurophysiologic disturbances present in this population and presenting the central nervous system effects of sedative agents to permit optimal drug therapy.

DATA SOURCES

Review of the English language clinical and scientific literature using MEDline data search.

STUDY SELECTION

Literature references were selected through a key word search of sedative therapy, drugs used for sedation, and specific neurologic disorders and processes to provide an in-depth overview of sedative drug mechanisms of action, effects on neurophysiology and intracranial dynamics, pharmacokinetics, and toxicity profile. Special emphasis was placed on neurologic side effects.

DATA EXTRACTION

Clinical and scientific literature was reviewed and data relevant to neurophysiologic effects of sedative drug therapy were summarized. Recommendations for institution of sedative therapy and of particular agents were made as a result of analysis of all pooled data.

DATA SYNTHESIS

Critically ill patients with neurologic pathology present as a unique subset of individuals cared for in an acute care setting. Because monitoring of neurologic patients requires frequent assessment of the neurologic examination, the goal of sedative therapy should be to enhance, or to minimally perturb elicitation of the examination. Neurophysiologic disturbances introduce distinct risks for sedation and require their identification and understanding before the initiation of any sedative therapy. Sedative drugs, in particular, act to disturb central nervous system function and their effects may result in diagnostic confusion and further neurologic deterioration. The pharmacokinetic and neurophysiologic actions of the common classes of sedative agents, such as benzodiazepines, opioids, barbiturates, and neuroleptics, as well as ketamine, propofol, and clonidine are discussed. Recommendations are presented based on the specific type of sedation required and the underlying neurologic disturbance. Several specific examples, including head trauma, neuromuscular disease, and alcohol withdrawal, are provided.

CONCLUSIONS

Preservation of the neurologic examination is paramount in documenting clinical improvement or deterioration in the critically ill neurologic patient. Pharmacologic sedation in this unique population of acute care patients requires careful consideration of the underlying neurophysiologic disturbances and potential adverse effects introduced by sedative drugs.

A placebo-controlled trial using intravenous atropine as an adjunct to conscious sedation in pediatric esophagogastroduodenoscopy

BACKGROUND

The usefulness of intravenous atropine as an adjunct to conscious sedation in pediatric esophagogastroduodenoscopy remains an unresolved issue.

METHODS

This prospective, double-blind, randomized study examined 101 patients, who were randomized to receive either intravenous atropine 0.02 mg/kg (maximum 0.4 mg) or a placebo of normal saline solution prior to the procedure.

RESULTS

The mean maximum heart rate during the procedure and the percentage of time that the heart rate was more than 1 standard deviation above mean for age was significantly greater in the atropine group as compared to the placebo group (p < 0.0005). There was no significant difference between groups in the amount of secretions noted, gastric motility, retching or vomiting, facial flushing, or dysphoria. There were no causes of significant bradycardia or hypotension in either group. There was a significant number of patients greater than 5 years of age and receiving meperidine and atropine (as compared with meperidine and placebo) whose arterial oxygen saturation dropped below 90% during the procedure (p = 0.0485).

CONCLUSIONS

We found that the use of atropine when used as an adjunct to conscious sedation in children undergoing upper endoscopy did not increase the safety of the procedure or provide significant benefits. We do not recommend the routine use of atropine for upper endoscopy in pediatric patients.

Anaesthesia for thyroplasty

The purpose of this report is to describe the anaesthetic considerations for layngoplastic procedures. Thyroplasty is a procedure which restores the voice in unilateral vocal cord paralysis. The procedure employs an external approach via a window cut at the appropriate level in the thyroid ala. A wedge of silastic is inserted against the inner perichondrium, thereby displacing the vocal cord medially and permitting voice production. Correct placement of the implant is assessed by asking the patient to phonate; patient cooperation is therefore necessary at certain times during the procedure. We describe our management of a patient undergoing thyroplasty. The use of a benzodiazepine agonist-antagonist combination provided both optimal operating conditions and patient comfort.

The effect of supplemental dietary fat on plasma cholesterol levels in lovastatin-treated hypercholesterolemic patients

STUDY OBJECTIVE

A validation study was conducted first to test assumptions about the effect of saturated and unsaturated dietary fat supplements. The second study was conducted to determine the effect on blood cholesterol levels of saturated and unsaturated fat supplements in patients who followed a low-fat diet and were administered lovastatin.

DESIGN

Randomized, crossover design, with three periods in the first study and four in the second study, each lasting 6 weeks.

SETTING

Cholesterol Research Center.

PATIENTS

The first study evaluated adults with total cholesterol levels between 200 and 280 mg/dl (5.172 and 7.241 mmol/L). The second study included adults with low-density lipoprotein (LDL) cholesterol levels above 160 mg/dl (4.138 mmol/L).

INTERVENTIONS

Fat supplements with either coconut or canola oil were delivered to patients in oatmeal-raisin cookies.

MEASUREMENTS AND MAIN RESULTS

In the validation study, patients' mean prerandomization total cholesterol level of 222 mg/dl was reduced to 213 mg/dl with canola oil and increased to 233 mg/dl with coconut oil cookies (p = 0.0038). In the second study the mean prerandomization total cholesterol level of 214 mg/dl was decreased to 199 mg/dl with canola oil and to 208 mg/dl with coconut oil cookies (p = 0.2342). The LDL cholesterol levels changed in a similar fashion in both studies.

CONCLUSIONS

Changes in total and LDL cholesterol levels in the validation study were expected based on established effects of saturated and unsaturated fatty acids, but changes in these levels in lovastatin-cookie study were not expected. They could have occurred because lovastatin reversed the effect of saturated fats and enhanced the effect of unsaturated fats. Alternatively, they may have been due to enhanced bioavailability of lovastatin when administered with a high-fat diet. These findings must be confirmed.

Use of analgesics during propofol sedation: a comparison of ketorolac, dezocine, and fentanyl

STUDY OBJECTIVE

To evaluate the comparative efficacy and side effect profile of ketorolac 60 mg, dezocine 6 mg, and fentanyl 100 micrograms when used as analgesic supplements to a propofol infusion during monitored anesthesia care (MAC).

DESIGN

Randomized, double-blind, placebo-controlled study.

SETTING

Ambulatory surgery facility at a university medical center.

PATIENTS

80 outpatients undergoing breast biopsy or inguinal herniorraphy procedures under MAC.

INTERVENTIONS

All patients received midazolam 2 mg intravenously (IV) followed by 1 ml of the study medication containing either dezocine 3 mg IV, ketorolac 30 mg IV, fentanyl 50 micrograms IV, or normal saline. A propofol infusion was initiated at 75 micrograms/kg/min and then varied to maintain a stable level of sedation (i.e., Observer Assessment of Alertness/Sedation scale score of 3). An additional 1 ml of the same study medication was administered IV 2 to 3 minutes prior to infiltration of the local anesthetic solution. During the operation, supplemental (rescue) medication consisted of fentanyl 25 micrograms IV, bolus injections in all four treatment groups.

MEASUREMENTS AND MAIN RESULTS

Propofol infusion and supplemental fentanyl dosage requirements, oxygen saturation values, respiratory rates, recovery times, and postoperative side effects were recorded. Visual analog scales were used to assess sedation, anxiety, pain, and nausea preoperatively (baseline), upon entry into the postanesthesia care unit, and at 30-minute intervals until discharge. The fentanyl and dezocine groups required lower average infusion rates of propofol to maintain a stable level of sedation than the control (saline) group. The saline and ketorolac groups required rescue analgesic medication more frequently and/or larger supplemental dosages of fentanyl than the two opioid analgesic treatment groups. Compared with the three analgesic treatment groups, postoperative pain scores were only marginally higher in the control group. Ketorolac-treated patients had consistently (but not significantly) shorter recovery times to oral intake, ambulation, and discharge than those in the dezocine or fentanyl groups. No postoperative nausea, vomiting, or pruritus was reported in the ketorolac group.

CONCLUSION

Compared with ketorolac 60 mg, fentanyl 100 micrograms and dezocine 6 mg produced a greater decrease in the propofol sedation requirement during MAC. However, the use of ketorolac in combination with propofol for MAC was associated with an improved recovery profile.

Spinal anesthesia for repair of meningomyelocele in neonates

The use of spinal anesthesia for meningomyelocele repair in neonates has received minimal attention. Spinal anesthesia may lessen the stress response to surgery and decrease postoperative respiratory complications. We therefore examined the efficacy of spinal anesthesia in 14 neonates requiring repair of lumbar or sacral meningomyelocele. All neonates were positioned prone with a small chest roll. Hyperbaric 0.5% tetracaine with epinephrine was injected into the caudal end of the meningomyelocele sac. If necessary, supplemental tetracaine was administered directly into the intrathecal space by the surgeon during the operation. Blood pressure, heart rate, and oxyhemoglobin saturation were measured throughout surgery. Neonates were monitored with transthoracic impedance apnea monitors, electrocardiogram (ECG), and pulse oximetry for 36 h after surgery. Spinal anesthesia was successful in all cases. Seven patients received one supplemental tetracaine injection; one patient received two supplemental injections. Arterial blood pressure decreased an average of 5 mm Hg with the largest decrease being 10 mm Hg. Two postoperative respiratory events occurred in the first 8 h after surgery. Both neonates had received intraoperative midazolam for sedation. Neurologic function was assessed pre- and postoperatively. Twelve patients had no change in neurologic function after surgery, while two infants demonstrated improved function. We conclude that spinal anesthesia can be safely used for meningomyelocele repair.

Severe withdrawal syndrome possibly associated with cessation of a midazolam and fentanyl infusion

A 40-month-old child was sedated with a fentanyl and midazolam infusion for 7 days. After the drugs were discontinued he became unresponsive and globally aphasic, and had marked thrombocytosis. He was hospitalized for 4 weeks, during which time his motor and cognitive status slowly improved, and had almost returned to baseline at time of discharge. Severe neurologic abnormalities have been reported with midazolam and fentanyl, administered separately or together, and seem to be a consequence of a withdrawal syndrome. Of interest, this patient had a reactive thrombocytosis at the time of onset of the withdrawal syndrome, and his decreased platelet count coincided with the return to normal cognitive and motor status. Based on this experience and other reports, we believe midazolam-fentanyl combination should be administered with caution.

Effects of midazolam on heart rate variability during surgery under spinal anaesthesia

Effects of midazolam on the cardiac autonomic nervous system were studied by power spectral analysis of electrocardiographic R-R intervals in patients undergoing elective lower abdominal surgery under spinal anaesthesia. Patients were randomly assigned into two groups: 10 patients in group A received spinal anaesthesia only and 10 in group S received spinal anaesthesia and midazolam of 0.05 mg/kg when surgery started. In the frequency domain power spectra, low (Lo; 0.04-0.15 Hz) and high (Hi; 0.15-0.40 Hz) frequency components were integrated to ascertain sympathetic and parasympathetic activity, respectively. There was no intergroup difference in starting time of surgery, ventilatory frequency, arterial pressure, heart rate, mean and variance of R-R interval, and cephalad level of analgesia. In spectral component, Lo decreased (P < 0.05) and Hi/Lo ratio increased (P < 0.05) relative to their baselines in group S. These were also different from group A (P < 0.05). We concluded that intravenous midazolam depressed sympathetic activity to produce a vagotonic cardiac autonomic nervous system under spinal anaesthesia.

Sedative and ventilatory effects of midazolam infusion: effect of flumazenil reversal

The purpose of this study was to evaluate the effects of flumazenil (1 mg i.v.) on the ventilatory response of premedicated patients receiving a continuous infusion of midazolam for sedation. After assessing baseline ventilatory function using a modified Read rebreathing method for determining hypercapnic ventilatory drive, 16 healthy outpatients were administered fentanyl, 50 micrograms i.v., and midazolam 2 mg i.v., followed by a variable-rate midazolam infusion, 0.3-0.5 mg.min-1. Upon termination of the midazolam infusion, serum midazolam concentrations were measured and ventilatory function was reassessed. Then, 10 ml either saline or flumazenil (1 mg) were administered according to a randomized, double-blind protocol. Ventilatory function was subsequently measured at 5 min, 30 min and 60 min intervals after study drug. Compared with the baseline value, midazolam infusion reduced tidal volume and increased respiratory rate and alveolar dead space. However, midazolam did not decrease the slope of the CO2-response curve. Flumazenil reduced the degree of midazolam-induced sedation and the decrease in tidal volume (P < 0.05), but not the change in resting respiratory rate. In some patients, the ventilatory response to hypercarbia actually decreased after flumazenil administration compared with the immediate prereversal (sedated) values. It is concluded that midazolam infusion, 0.43 mg.min-1, did not impair CO2-responsiveness. Flumazenil's effect on central ventilatory drive was more variable than its reversal of midazolam-induced sedation.

Anesthetic management of a patient with obstructive sleep apnea syndrome and difficult airway access

Patients with the obstructive sleep apnea syndrome (OSAS) are predisposed to respiratory complications under the influence of sedative and anesthetic drugs because of these drugs' alternation of respiratory control with a tendency for upper airway collapse. Additional difficulties for airway management during anesthesia may arise if fixed anatomic obstacles block the upper airway. We present a case of a patient with OSAS scheduled for general anesthesia for nasal polypectomy and correction of a deviated septum. Preoperative evaluation revealed several factors known to be associated with difficult intubation and ventilation: nasal obstruction, maxillofacial malformation (micrognathia), reduced temporomandibular joint mobility, and obesity. An individualized strategy of airway management based on published standards was developed and successfully applied. It involved fiberoptic guided intubation through a laryngeal mask airway. This case illustrates the management of patients with OSAS and additional conditions that reduce upper airway patency.

Analgesia and sedation in interventional radiological procedures

The use of intravenous analgesia and anxiolytics in interventional radiology improves the patient's tolerance of potentially painful and prolonged procedures and allows the radiologist better control of the course of the procedure being undertaken. Monitoring of the patient's oxygen saturation, pulse rate, respiration, blood pressure and cardiac rhythm during a procedure is essential. Fentanyl and midazolam is a combination that is effective and convenient to use because both agents are relatively short acting, have little cardiovascular depression and are easily reversible (with naloxone and flumazenil). They are a better alternative to pethidine and diazepam because they can be more tightly titrated and controlled and are safer and more suitable for use in outpatients. Monitoring for respiratory depression is important and special care must be taken in the elderly and patients with hepatic, renal or chronic airways disease. General anaesthesia may be unavoidable in patients who are unstable, unco-operative or who have raised intracranial pressure.

Conscious sedation for gastroscopy: patient tolerance and cardiorespiratory parameters

BACKGROUND/AIMS

Most patients receive conscious sedation for gastroscopy. However, the benefit of the most often used combination of low-dose intravenous midazolam and topical lidocaine on patient tolerance remains poorly defined and has not been shown to outweigh cardiorespiratory risks. To respond to these issues, a randomized, double-blind, placebo-controlled prospective study was performed.

METHODS

Two hundred outpatients undergoing diagnostic gastroscopy were assigned to receive either (1) midazolam (35 micrograms/kg) and lidocaine spray (100 mg), (2) midazolam and placebo lidocaine, (3) placebo midazolam and lidocaine, or (4) placebo midazolam and placebo lidocaine.

RESULTS

Tolerance (visual analogue scale, 0-100 points; 0, excellent; 100, unbearable) improved as compared with placebo midazolam and placebo lidocaine by 23 points (95% confidence interval, 15-32) in group 1, 15 points (95% confidence interval, 7-24) in group 2, and 10 points (95% confidence interval, 2-18) in group 3. Increasing age (P < 0.001), low anxiety (P < 0.001), and male sex (P < 0.03), but not amnesia, were associated with better patient tolerance. Oxygen desaturation (< 1 minute) occurred in 8.2% and was not more frequent after midazolam treatment. Hypotension was rare (2.1%), and no adverse outcome occurred.

CONCLUSIONS

Both low-dose midazolam (35 micrograms/kg) and lidocaine spray have an additive beneficial effect on patients tolerance and rarely induce significant alterations in cardiorespiratory monitoring parameters, thus supporting the widespread use of conscious sedation.

Characteristics of propofol in outpatient oral and maxillofacial surgery

Propofol is a relatively new intravenous anesthetic with qualities that make it useful in the practice of oral and maxillofacial surgery. In a preliminary study to examine the safety of the drug, 100 patients ASA class I patients were treated in an outpatient environment with standardized doses of fentanyl and midazolam in combination with propofol. An induction dose of propofol of 1 mg/kg was followed by a constant bolus given at the rate of 10 mg/minute. The overall quality of induction and maintenance of anesthesia was good to excellent in 91% of cases. The main complications experienced were excessive movements during administration of local anesthesia, movement to stimulation during the operative period, and modest decreases in blood pressure. The results indicate that propofol is an effective means for the provision of general anesthesia in the outpatient oral surgery setting.

Practical uses of end-tidal carbon dioxide monitoring in the emergency department

Qualitative and quantitative measurement of the carbon dioxide (CO2) concentration in respiratory gases is readily available with current technology. End-tidal CO2 (PetCO2) monitoring, whether by qualitative colorimetric methods or by solid-state spectrophotometric techniques, is becoming increasingly valuable in the Emergency Department (ED). These techniques offer a practical adjunct to the ED management of critical interventions including endotracheal intubation, conscious sedation, and cardiopulmonary resuscitation.

Guidelines for sedation by nonanesthesiologists during diagnostic and therapeutic procedures. The Risk Management Committee of the Department of Anaesthesia of Harvard Medical School

The increasing use of sedation to enhance patient comfort during diagnostic and therapeutic procedures has been noted by the Joint Commission of Accredited Healthcare Organizations, specialty societies, and the public. Although anesthesiologists, by virtue of training and experience, possess unique qualifications to provide such sedation services, their availability remains somewhat limited by primary commitments to the operating room, intensive care unit, or pain service. The Risk Management Committee of the Department of Anaesthesia of Harvard Medical School has made specific recommendations to the Harvard-affiliated hospitals for anesthesiologists who participate in institutional-level committees in setting guidelines for such services when they are provided by nonanesthesiologists. Specific consideration is given to facilities, backup emergency services, equipment, education and training, issues of informed consent, documentation, and release of patients from medical care. These recommendations emphasize the collaboration of the department of anesthesia and other departments that provide sedation services in formulating policies and procedures that reflect values intrinsic to the practice of anesthesiology.

Morbidity and mortality in pediatric anesthesia

This article reviews specific considerations for greater anesthetic mortality in the first year of life as well as significant differences in pediatric anesthetic morbidity associated with routine anesthetic management. Clinical conditions such as upper respiratory tract infection, congenital heart disease, and muscle disease are addressed. Loss experience suggests a different profile for pediatric anesthesia.

Perioperative drug interactions

The various classes of IV and inhalation anesthetics all appear to potentiate one another. Many of these interactions are clinically useful in outpatient anesthesia, and many are quite predictable. True synergy is most likely to occur when two drugs produce similar actions by slightly different mechanisms. These principles are particularly well demonstrated by the interactions of hypnotic drugs at the locus ceruleus. It is possible that the reduced anesthetic requirements seen in some disease states may involve similar mechanisms.

Pharmacokinetics and pharmacodynamics in the critically ill patient

1. Until recently, when drugs were used in critically ill patients they were expected to behave in the same way as in less seriously ill patients. Now the unpredictability of even the most reliable drugs has been recognized. With this there is an awareness of the adverse effects drugs may have on organs other than the ones the drug was intended to act on. In patients with multiorgan dysfunction, poly-pharmacy is usually needed. The drugs may not only interfere with the action of each other at the receptor and enzyme level, but may also change protein binding and elimination. All these effects may be unimportant in less seriously ill patients, but may affect outcome in the critically ill. A high degree of awareness and suspicion of unknown drug-induced adverse reaction is needed by clinicians and pharmacologists alike.

Impact of newer drugs and techniques on the quality of ambulatory anesthesia

Recent pharmacologic and technologic advances in anesthesia and surgery allow outpatients with complex medical problems to undergo a wide variety of diagnostic and surgical procedures on an ambulatory basis. Increasingly, however, anesthesia practitioners, as well as pharmacy and therapeutic committees, are demanding proof that a new, more costly drug or medical device is superior to existing products in achieving its desired effect, is associated with fewer adverse effects, enhances efficiency, and reduces health care costs. The new field of pharmacoeconomics has emphasized the importance of cost-effectiveness analyses that consider both direct and indirect costs of newer drugs and therapeutic modalities. As new biomedical technology is introduced to facilitate the perioperative management of patients (e.g., computerized anesthesia information management systems), evidence that these systems enhance our ability to continue to provide high-quality, cost-effective health care will assume increasing importance. Limitations in health care resources necessitate a careful reevaluation of our clinical practices with respect to choice of drugs, supplies, equipment, and even discharge criteria. Ambulatory anesthesia and surgery will continue to increase because of the potential cost savings for patients undergoing elective operations on an outpatient basis. However, the challenge we face will be to continue to provide high-quality anesthesia care at a reduced cost. A careful examination of commonly accepted (but unproven) clinical practice patterns will be necessary to meet this challenge.

Carbon dioxide retention and oxygen desaturation during gastrointestinal endoscopy

BACKGROUND

Pulse oximetry measures arterial oxygen saturation (SpO2), not hypoventilation, which is directly reflected by increases in carbon dioxide tension.

METHODS

In the present study, transcutaneous carbon dioxide tension (PtcCO2) and SpO2 were measured during 101 endoscopic procedures selected for long duration or comorbid illnesses, and relationships between hypercapnia and hypoxemia were evaluated. Nasal oxygen was administered only for sustained desaturation (SpO2 < 90%).

RESULTS

Mean peak increase in PtcCO2 was significantly higher in patients requiring oxygen for sustained desaturation (16.3 mm Hg; range, 4-52) than in patients breathing room air who had transient or no desaturation (10.2 mm Hg [range, 3-19] and 5.1 mm Hg [range, 0-15]). If nasal oxygen corrected desaturation, even transient recurrence of desaturation indicated worsening CO2 retention, which preceded respiratory arrest in one patient. Independent predictors of hypercapnia were fentanyl and midazolam doses, oxygen requirement, and dementia.

CONCLUSIONS

Severe hypoventilation may occur during endoscopy, undetected by clinical observation or pulse oximetry, but only in sedated patients who require supplemental oxygen to maintain SpO2 above 90%. After oxygen supplementation corrects desaturation, recurrence of desaturation implies severe hypoventilation and warrants limitation of further sedation.

Experimental evaluation of two new sensors for respiratory rate monitoring

Visual observation was chosen as the reference method for measuring the respiratory rate in ten healthy volunteers. The new fibre-optic and acoustic sensors were simultaneously compared with capnography and transthoracic impedance plethysmography during normoventilation in the respiratory rate range of 6-24 breaths per minute and at a fixed respiratory rate of 13 breaths per minute. In addition a simulation of central apnoea was performed. All the measurements were recorded on an analogue tape recorder and a strip-chart recorder and analysed off line. The analyses of the recordings were performed by a person who was unable to see the monitoring systems. There was no discrepancy in the results of these methods. Each of the methods responded rapidly to an apnoeic event. The new fibre-optic and acoustic sensors correlate well with more traditional methods such as capnography and transthoracic impedance plethysmography for respiratory rate monitoring.

The opioid-sparing effect of diclofenac sodium in outpatient extracorporeal shock wave lithotripsy (ESWL)

STUDY OBJECTIVE

To evaluate the opioid-sparing and analgesic effect of diclofenac sodium in ambulatory nonimmersion extracorporeal shock wave lithotripsy (ESWL).

DESIGN

Randomized, double-blind, placebo-controlled study.

SETTING

Large referral hospital.

PATIENTS

Twenty-seven ASA physical status I and II patients with upper renal tract nephrolithiasis.

INTERVENTIONS

ESWL was performed with a sedative-analgesic technique. Diclofenac sodium 75 mg or an equal volume of saline was given intramuscularly 45 minutes prior to the procedure. Fentanyl and midazolam were added to maintain adequate sedation and analgesia.

MEASUREMENTS AND MAIN RESULTS

Demographically, both groups were comparable. In the diclofenac sodium group, heart rate was slightly higher, treatment time was shorter, more shock waves were administered (p < 0.02), and less fentanyl was required (p < 0.02). Mean arterial pressure was lower and arterial oxygen saturation by pulse oximeter was higher in the diclofenac sodium group. There were no differences between the groups in voltage, stone size, fragmentation, dose of midazolam administered, or overall assessment by both the doctors and patients.

CONCLUSIONS

Patients administered diclofenac sodium received a greater number of shock waves, required less fentanyl, and showed a marginal improvement in hemodynamic stability and oxygenation during ambulatory nonimmersion ESWL.

Emergency management of the airway outside the operating room

Successful emergency airway intervention incorporates the anaesthetist's basic skills in airway management with the knowledge of the special nature of the clinical problems that arise outside the operating room. While a thorough but rapid evaluation of the key anatomical and physiological factors of an individual patient may result in an obvious choice for optimal management, clinical problems often arise in which there is not an evident "best approach." In these less clear-cut situations, the anaesthetist may do well to employ those techniques with which she/he has the greatest skills and experience. At times, however, some degree of creative improvisation is required to care for an especially difficult problem.

Ketorolac or fentanyl to supplement local anesthesia?

STUDY OBJECTIVE

To evaluate the usefulness of ketorolac in the treatment of intraoperative pain refractory to the administration of local anesthetic alone.

DESIGN

Intraoperative acute-pain treatment model consisting of awake, nonsedated patients who randomly received either an opioid or a study drug in a double-blind fashion.

SETTING

University medical center.

PATIENTS

Eighty patients who underwent breast biopsy, lumpectomy, or central venous catheter placement.

INTERVENTIONS

Patients received either ketorolac 1 mg/kg intravenously (IV) up to a total dose of 60 mg or fentanyl 3 micrograms/kg IV up to a total dose of 250 micrograms to supplement the local anesthetic.

MEASUREMENTS AND MAIN RESULTS

Verbal pain evaluation and the visual analog scale (VAS) were used for perioperative measurement of pain. Heart rate (HR), blood pressure, and respiratory rate (RR) were recorded before and after analgesic drug injections at 10-minute intervals, both intraoperatively and while the patient was in the postanesthesia care unit (PACU). Speed of recovery was quantified by p-deletion and digit substitution tests on admission to the PACU and at 30-minute intervals until discharge. The frequency of nausea, vomiting, and pruritus were recorded. There were no differences between the groups in perioperative verbal pain evaluation, VAS scores, HR, systolic blood pressure, diastolic blood pressure, or RR. Patients who received ketorolac exhibited a significantly lower frequency of intraoperative and postoperative medication administration intraoperatively, than those who received fentanyl. No additional pain medication was required by patients in the PACU in either group.

CONCLUSIONS

Ketorolac is a useful alternative to fentanyl for the treatment of intraoperative pain refractory to the administration of local anesthetic alone during monitored anesthesia care. A decided advantage of ketorolac over fentanyl is the absence of nausea and vomiting in the intraoperative and postoperative periods.