Background Infusion Rate Research Articles

Illustrative neonatal cases regarding drug delivery issues.

Illustrative neonatal cases regarding drug delivery issues.

Finding the 'Ideal' Regimen for Fentanyl-Based Intravenous Patient-Controlled Analgesia: How to Give and What to Mix?

PurposeThis analysis was done to investigate the optimal regimen for fentanyl-based intravenous patient-controlled analgesia (IV-PCA) by finding a safe and effective background infusion rate and assessing the effect of adding adjuvant drugs to the PCA regimen.Materials and MethodsBackground infusion rate of fentanyl, type of adjuvant analgesic and/or antiemetic that was added to the IV-PCA, and patients that required rescue analgesics and/or antiemetics were retrospectively reviewed in 1827 patients who underwent laparoscopic abdominal surgery at a single tertiary hospital.ResultsUpon multivariate analysis, lower background infusion rates, younger age, and IV-PCA without adjuvant analgesics were identified as independent risk factors of rescue analgesic administration. Higher background infusion rates, female gender, and IV-PCA without additional 5HT3 receptor blockers were identified as risk factors of rescue antiemetics administration. A background infusion rate of 0.38 µg/kg/hr [area under the curve (AUC) 0.638] or lower required rescue analgesics in general, whereas, addition of adjuvant analgesics decreased the rate to 0.37 µg/kg/hr (AUC 0.712) or lower. A background infusion rate of 0.36 µg/kg/hr (AUC 0.638) or higher was found to require rescue antiemetics in general, whereas, mixing antiemetics with IV-PCA increased the rate to 0.37 µg/kg/hr (AUC 0.651) or higher.ConclusionBackground infusion rates of fentanyl between 0.12 and 0.67 µg/kg/hr may safely be used without any serious side effects for IV-PCA. In order to approach the most reasonable background infusion rate for effective analgesia without increasing postoperative nausea and vomiting, adding an adjuvant analgesic and an antiemetic should always be considered.

An investigation on influential factors of patient-controlled epidural analgesic requirement over time for upper abdominal surgeries

BackgroundPatient-controlled epidural analgesia (PCEA) is commonly used to relieve postoperative pain for upper abdominal surgeries. However, there is still a lack of studies exploring factors associated with PCEA consumption over time after upper abdominal surgery; our study intended to provide further elucidation about this issue. MethodsThis study retrospectively evaluated postoperative PCEA consumption over time after upper abdominal surgery. Cumulative PCEA consumption in the first four 12-hour intervals was directly retrieved from the data recorded by infusion pumps. Potentially influential factors of PCEA requirements, including demographic variables and infusion pump settings, were also collected. A linear mixed model was applied to investigate the relationships between these factors and PCEA consumption over time. A backward elimination strategy was used to select independent factors significantly associated with PCEA consumption. ResultsA total of 1001 patients were included in the analysis. On average, PCEA consumption after upper abdominal surgery peaked during the 2nd 12-hour interval and then decreased gradually over time. After the model selection processes were completed, four independent factors were identified to have significant effects on PCEA consumption. Surgery for malignant disease and background infusion rate were positively associated with PCEA consumption and did not interact with time. Additionally, female patients tended to consume less and less PCEA over time relative to males. Age had a negative effect on PCEA consumption, which peaked during the 2nd 12-hour interval and then decreased gradually over time. The final selected model exhibited acceptable predictive power relative to the observed data. ConclusionOur analyses provided valuable information about the factors associated with PCEA consumption over time after upper abdominal surgery. However, the mechanism of how these factors interact over the course of time awaits further investigation.

Comparison of dexmedetomidine and ketamine for the analgesic effect using intravenous patient-controlled analgesia after gynecological abdominal surgery

Comparison of dexmedetomidine and ketamine for the analgesic effect using intravenous patient-controlled analgesia after gynecological abdominal surgery

The 90% effective dose of a sufentanil bolus for the management of painful positioning in intubated patients in the ICU

Pain and discomfort arising from the routine care of intubated patients in the ICU is managed by continuous infusion of narcotic and sedative drugs. There is benefit in keeping infusion rates low because lightening sedation improves clinical outcome, but this risks breakthrough pain. Management of this discomfort by bolus administration could permit lower background infusion rates, but the lowest effective bolus dose of sufentanil to achieve this is unknown. The aim of this study was to determine the effective analgesic dose in 90% of intubated patients (ED90) in the ICU given bolus sufentanil. Pain was assessed using a Behavioural Pain Scale (BPS) requiring a score of 3-4 during moving to the lateral decubitus position. Prospective, dose response study. A 16-bed multidisciplinary ICU in a French university hospital. Study period was from January to June 2010. Intubated and ventilated patients were eligible for the study once they had reached a BPS of 3 or 4 and Ramsay score of 3-5 within 48 h of admission to the ICU. The analgesic efficacy of a sufentanil bolus was measured during successive lateral decubitus positioning over a 72-h study period, using the BPS scale. The dose was increased with each subsequent turn to lateral decubitus until a BPS score of 3-4 was obtained (dose escalation, starting at zero). BPS, Ramsay score, heart rate and mean arterial pressure were collected before and during each procedure. A total of 25 patients were enrolled over 6 months. The ED90 bolus for sufentanil was 0.15 μg kg, but 40% of the patients subsequently demonstrated increased BPS with this dose. The effective dose in 90% was 0.15 μg kg during the first 5 days of sedation. There were no adverse effects. A pre-emptive sufentanil bolus can be used to treat anticipated pain in the ICU. Regular and frequent assessments of acute pain and sedation are essential for adjusting the dose, on a case-by-case basis. This strategy may help clinicians to keep background infusions of sedatives and narcotics as low as possible and may improve clinical outcome. ClinicalTrials.gov NCT01356732.

Morphine at “sub-analgesic” background infusion rate plus low-dose PCA bolus control pain better and is as safe as twice a bolus-only PCA regimen: A randomized, double blind study

Morphine for postoperative pain control is commonly titrated via intravenous patient-controlled analgesia (IV-PCA). An IV morphine background infusion is rarely used. We investigated whether analgesia is effectively attained and morphine consumption is reduced if PCA titration is coadjuvated by a continuous infusion protocol. Following colorectal cancer surgery, consenting patients were randomized to receive a minimal (“sub-analgesic”) dose of morphine 0.01mg/kg/h background infusion plus a 0.01mg/kg bolus (BI), or a 1.5mg bolus-only morphine (B0) (bolus ratio ∼1:2). Bolus lockout time was 7min in either case. All patients received 0.1mg/kg morphine before protocol initiation, and diclofenac 75mg intramuscularly b.i.d. during the study period, lasting 48h. Eighty-six patients (51 males, age 26–95 years) participated in the study. The total mean morphine consumption during the 48h was 25% lower in the BI than in the B0 group (P<0.05). Although the former applied the PCA device for boluses 19% less than the latter (P<0.05), their pain score was lower (P<0.05) most of the time, and they reported greater satisfaction (P<0.05) on a 10-scale numerical rating score. Pre- and postoperative vital signs were similar for both groups. No patient depicted hypoxemia or lapsed into deep sedation. Four BI and three B0 patients required treatment for postoperative nausea and vomiting. One BI patient had transient pruritus and one B0 69-year individual became disoriented 24h into treatment; either event subsided soon after stopping their respective regimen without the need for treatment. The main conclusions of the results are that very-low-dose background morphine infusion combined with small-dose PCA boluses may provide better pain relief, lower morphine consumption, and minimal complication rate as a 1.5mg PCA bolus-only protocol.

The effect of combining dexamethasone with ondansetron for nausea and vomiting associated with fentanyl‐based intravenous patient‐controlled analgesia

Song et al. reported that the addition of dexamethasone to ondansetron failed to reduce the incidence of nausea and vomiting experienced by patients using fentanyl patient-controlled analgesia (PCA) after thoracoscopic surgery, although it appeared to lessen the severity [1]. We find the incidences of nausea and vomiting both with and without dexamethasone reported in this study (45% and 56%, respectively) surprisingly high and far in excess of those seen in our institution where fentanyl PCA is frequently used after kidney transplant. Other studies have reported considerably lower incidences of nausea and/or vomiting (30% or less) associated with the use of fentanyl PCA after arthroplasty [2], colorectal surgery [3], thoracoscopy [4] and thoracotomy [5], and during labour [6], even without any antiemetic prophylaxis. Incidences exceeding 50% have indeed been reported but are related to higher basal infusion rates [7]. Interestingly, in comparison with the above studies, the regimen employed by Song et al. consisted of a relatively high basal infusion rate (0.4 μg. kg−1.h−1) and low patient demand capacity (0.1 μg.kg−1 bolus every 15 min). It seems counterintuitive to use a high background infusion rate if this could result in a high incidence of nausea and vomiting. Moreover, in the presence of an insufficient fentanyl bolus on demand, we would question the validity of administering pethidine for breakthrough pain. Although the authors state that cumulative pethidine consumption was similar between groups, they did not provide the doses used over 48 hours. Without the patients’ pain scores, which would inform the reader about the efficacy of the PCA regimen, we find it difficult to put the severity of the side effects into the context of the benefits of any pain relief. We would suggest that the need for frequent pethidine administration suggests that the analgesic regimen is unsatisfactory. Finally, the practice of adding an antiemetic to PCA mixtures has declined in popularity because the dose received by patients is typically sub-therapeutic if PCA usage is reduced or stopped, and especially if boluses of an alternative opioid are then administered. We agree that it may be valid to state that dexamethasone failed to reduce the incidence of postoperative nausea and vomiting in this study; however, without reference to the cumulative doses of fentanyl, pethidine or ondansetron, we question the conclusion that these high incidences of nausea and vomiting, apparently refractory to 5-HT3 receptor-blocking drugs, are typical of fentanyl PCA in general.

Morphine and its metabolites after patient-controlled analgesia: considerations for respiratory depression

Study Objective To assess concentrations of morphine and its metabolites after patient-controlled analgesia (PCA). Design Pilot pharmacokinetic study of morphine and pharmacokinetic simulation. Setting Post-anesthesia care room and ward of an academic teaching hospital. Patients 10 ASA physical status I, II, and III postoperative surgical patients. Interventions Patients received morphine via PCA by routine hospital protocols. Measurements The population mean plasma and effect-site concentrations of morphine, morphine-6-glucuronide (M6G), and morphine-3-glucuronide (M3G) was simulated in 4 patient group scenarios: morphine PCA used alone, morphine PCA used with continuous background morphine infusion of 0.5 mg/hr, morphine PCA used with continuous background morphine infusion of 1.0 mg/hr, and morphine PCA used with continuous background morphine infusion of 2.0 mg/hr. Main Results The 4 groups exhibited simulated peak morphine, M6G, and M3G effect-site concentrations at 8 to 24 hours post-infusion. The highest peak morphine, M6G, and M3G effect-site concentrations decreased in the following order by group: 2.0 mg/hr morphine infusion + PCA group, 1.0 mg/hr morphine infusion + PCA group, and 0.5. mg/hr morphine infusion + PCA group. Conclusions Patients receiving morphine PCA should be monitored closely from 8 to 24 hours postoperatively. Morphine PCA given with background infusion rates up to 1.0 mg/hr does not offer distinct pharmacokinetic advantages over morphine PCA alone. Morphine PCA with background infusion rate of 2.0 mg/hr is associated with the greatest risk of respiratory depression.

Effects of flurbiprofen on cellular immune function during patient-controlled intravenous analgesia with fentanyl in patients after esophagectomy

Objective To investigate the effects of flurbiprofen on cellular immune function during patient-controlled intravenous analgesia (PCIA) with fentanyl in the patients after esophagectomy. Methods Forty-five ASA Ⅰ or Ⅱ patients, aged 40-64 yr, weighing 50-80 kg, were randomly divided into 3 groups with 15 cases each: group Ⅰ PCIA with fentanyl 20 μg/kg; group Ⅱ PCIA with fentanyl 10 μg/kg + flurbiprofen 2 mg/kg and group Ⅲ preemptive analgesia with iv flurbiprofen 1 mg/kg + PCIA with fentanyl 10 μg/kg + flurbiprofen 1 mg/kg. The patients received iv injection of fentanyl 0.05 mg 10 min before the end of operation and then were attached to a PCIA pump. Droperidol 2.5 mg was added to normal saline 100 ml in all groups. PCIA was started with background infusion rate 2 ml/h, bolus dose 0.5 ml, lockout interval 5 min. Blood samples were obtained from peripheral vein at 30 min before operation (T0, baseline), and at 1, 24 and 72 h after operation (T1-3) for determination of the plasma concentrations of norepinephrine (NE), adrenocorticotropic hormone (ACTH), cortisol (Cor) and levels of CD3+, CD4+ and CD8+ in lymphocyte. CD4+/CD8+ ratio was calculated. The number of successful delivered doses was recorded. Results The number of successful delivered doses was significantly less in group Ⅲ than in group Ⅰ and Ⅱ (P 0.05). The plasma concentration of ACTH was significantly lower and CD3+ level significantly higher after operation in group Ⅱ , the plasma concentrations of NE, ACTH and Cor were significantly lower, CD3+ level was significantly higher at T1,3, and CD4+ level and CD4+/CD8+ ratio at T1,2 were significantly higher after operation in group Ⅲ than in group Ⅰ (P<0.05). The plasma concentration of NE was significantly lower, and CD4+ level and CD4+/CD8+ ratio were significantly higher in group Ⅲ than in group Ⅱ (P<0.05). Conclusion Flurbiprofen can improve the cellular immune function in the patients after esophagectomy through reducing the consumption of fentanyl for PCIA and inhibiting the postoperative stress, and the efficacy is better when flurbiprofen is used before and after operation. Key words: Flurbiprofen; Fentanyl; Analgesia, patient-controlled; Immunity, cellular

Patient-Controlled Epidural Analgesia Regimens for Labor Analgesia: Background Infusion or Demand-Only?

To the Editor: In a recent article on patient-controlled epidural analgesia (PCEA) for labor pain, Lim et al.1 conclude that demand-only PCEA resulted in an increased incidence of breakthrough pain, higher pain scores, and lower maternal satisfaction, when compared with PCEA with background infusion (ropivacaine 0.1% with fentanyl 2 μg/mL; 5-mL bolus, 10–15 min lockout interval, and 5- 10 mL/h infusion). These conclusions raise several issues. First, we acknowledge that performing this study as a randomized, controlled, double-blind trial is a challenge, but we are concerned that several aspects of the study design make it susceptible to expectation bias. Although breakthrough pain occurred more in the demand-only group, the hourly consumption of ropivacaine remained a low mean of 7.3 mg, corresponding with approximately 1.5 boluses. This may be the result of several hours of effective analgesia, but might also be due to inadequate use of the PCEA-system or failure to administer top-up boluses in a timely manner. Moreover, breakthrough pain may have been influenced by other factors not studied, e.g., fetal position. Parturients were withdrawn from the study when visual analog scale remained greater than 30 mm, despite a maximum of two supplemental top- up boluses of 5 mL ropivacaine 0.2%. Surprisingly, Table 2 shows a median number of zero administered supplemental boluses with a maximum of three in the demand-only group. The three different PCEA regimens compared do not only differ in background infusion rates, but also have different lockout times. The authors explain this to be standard PCEA settings used in their institution, as recommended in a review by D’Angelo.2 Not only were these settings designed for PCEA with bupivacaine 0.125%, but they were also suggested for meeting different specific goals. We, therefore, find comparing different PCEA regimens with different lock-out intervals to be inappropriate. Finally, Lim et al. state in the conclusions section of their abstract that demand-only PCEA resulted in lower maternal satisfaction. These conclusions are not supported by their data. Niels Koopmans, MD Götz J. K. Wietasch, MD, PhD Michel M. R. F. Struys, MD, PhD Department of Anesthesiology University Medical Center Groningen University of Groningen Groningen, The Netherlands [email protected]

Effects of CYP3A5~*3 genetic polymorphism on analgesia with fentanyl

Objective To investigate the effects of CYP3A5~* 3 genetic polymorphism on analgesia with fentanyl. Methods One hundred and eighty ASA Ⅰ or Ⅱ patients, aged 20-50 yr, Hart nationality, Henan province, scheduled for elective abdominal total hysterectomy or myomectomy under general anesthesia, were enrolled in this study. The polymorphic sites of the CYP3A5~* 3 allele were analyzed by polymerase chain reaction-restriction fragment length polymorphism. The patients were assigned to one of 3 groups according to their genotypes: wild homozygote group, mutation heterozygote group and mutation homozygote group. Midazolam, remifentanyl, propofol and succinylcholine were used for induction of anesthesia. The patients were mechanically ventilated after tracheal intubation. Remifentanyl, propofol and atracurium were given iv for maintenance of anesthesia. The pain was assessed with visual analog scale (VAS) after consciousness was regained. When VAS score > 3, the patients were given fentanyl 20 μg every 5 min until VAS score was decreased to ≤3 and then patient-controlled intravenous analgesia (PCIA) with fentanyl was started. The background infusion rate of fentanyl 1.0 mg and droperidol 5 mg (in 100 ml normal saline) was 0.5 ml/h. The PCIA pump was programmed to give a 2 ml bolus of fentanyl solution with a 5 min lockout interval, 7 time successful delivery per hour and maximum dosage 145 μg/h, and VAS score was maintained less than 3. The amount of fentanyl used within 24 h after surgery was recorded. Results No significant difference was detected in the fentanyl consumption in the 24 h during PCIA among the 3 groups (P> 0.05). Conclusion The genetic polymorphism CYP3 A5~* 3 is not the factor contributing to the individual variation in the patient's response to analgesia with fentanyl. Key words: Cytochrome P-450 enzyme system; Polymorphism,single nucleo tide; Fentanyl; Analgesia,patient-controlled

Determinants of Patient-controlled Epidural Analgesia Requirements

Patient-controlled epidural analgesia (PCEA) has been widely used in postoperative pain management. Many factors may correlate with PCEA requirements but no previous study has ever investigated this subject. Therefore, we conducted this study to explore the relationship among patients' characteristics and total PCEA consumption during the 3-day postoperative course. This prospective study was conducted with surgical patients receiving postoperative PCEA and completing the 3-day course. The PCEA regimen was prepared as 0.0625% bupivacaine with fentanyl (l microg/mL). Patients' characteristics including demographic data and surgical procedures were collected. The total doses were recorded after the course terminated. Stepwise regression analyses were conducted to select significant variables, which could determine total PCEA demand. Subgroup analyses were also performed to investigate whether differences exist among distinct surgical sites. There were 1753 patients (1094 men and 659 women) included in the analysis. Weight, age, height, body mass index, sex distribution, and total PCEA consumption were significantly different among various surgical sites (all P<0.001). Operational sites, procedures involving malignant disease, weight, and age are the most significant factors in sequence to determine total PCEA requirements. Height and sex have no impact on PCEA demand. The multiple correlation coefficient of our model is 0.688 and the predictive formula of the 3-day postoperative PCEA requirement was 240.1+(130.5xsite)+(66.6xmalignancy)+(1.7xweight)-(0.4xage). Our study demonstrated the association between patients' characteristics and total PCEA requirements from a large-scaled clinical data. Surgical procedures have more influence on PCEA consumption than demographic variables. Background infusion rate of PCEA could be determined from our predictive model.

Comparison of computer integrated patient controlled epidural analgesia vs. conventional patient controlled epidural analgesia for pain relief in labour

Computer integrated-patient controlled epidural analgesia (CI-PCEA) is a novel drug delivery system. It automatically titrates the background infusion rate based on the individual parturient's need. In this randomised trial, we compared the local anaesthetic consumption by parturients using CI-PCEA with demand only patient controlled epidural analgesia (PCEA) for labour analgesia. We recruited 40 parturients after approval by the ethics committee. Group PCEA (n = 20) received demand only PCEA. Group CI-PCEA (n = 20) received a similar PCEA regimen but the computer integration titrated the background infusion to 5, 10 or 15 ml x h(-1) if the patient required one, two or three demand boluses, respectively, in the previous hour. The background infusion decreased by 5 ml x h(-1) if there was no demand bolus in the previous hour. The sample size was calculated to show equivalence in local anaesthetic used. The time weighted consumption of local anaesthetic was similar in both groups (mean difference 0.7 mg x h(-1), 95% confidence interval [CI: -2.5, 1.1]; p = 0.425). The CI-PCEA group had higher maternal satisfaction scores: mean (SD) 93 (7) vs. 86 (11), p = 0.042. CI-PCEA does not increase the use of local anaesthetic when compared with demand only PCEA but does increase patient satisfaction.

Patient-Controlled Analgesia in the Management of Postoperative Pain

Patient-controlled analgesia (PCA) is a delivery system with which patients self-administer predetermined doses of analgesic medication to relieve their pain. Since its introduction in the early 1980s, the daily management of postoperative pain has been extensively optimised. The use of PCA in hospitals has been increasing because of its proven advantages over conventional intramuscular injections. These include improved pain relief, greater patient satisfaction, less sedation and fewer postoperative complications. All PCA modes contain the following variables: initial loading dose, demand dose, lockout interval, background infusion rate and 1-hour or 4-hour limits. Morphine is the most studied and most commonly used intravenous drug for PCA. In spite of the fact that it is the 'first choice' for PCA, other opioids have been successfully used for this option. The most observed adverse effects of opioid-based PCA are nausea and vomiting, pruritus, respiratory depression, sedation, confusion and urinary retention. Although intravenous PCA is the most studied route of PCA, alternative routes have extensively been described in the literature. PCA by means of peridural catheters and peripheral nerve catheters are the most studied. Recently, transdermal PCA has been described. The use of peripheral or neuraxial nerve blocks is recommended to avoid the so called opioid tolerance observed with the intravenous administration of opioids. Numerous studies have shown the superiority of epidural PCA to intravenous PCA. The beneficial postoperative effects of epidural analgesia are more apparent for high-risk patients or those undergoing higher risk procedures. PCA with peripheral nerve catheters results in increased postoperative analgesia and satisfaction for surgery on upper and lower extremities. Serious complications occur rarely with these catheters. With the introduction of an Acute Pain Service, management of postoperative pain can be improved. This will also help to minimise adverse effects related to PCA and to avoid lethal mishaps.

Remifentanil patient‐controlled analgesia following cardiac surgery

Remifentanil is increasingly used as a component of cardiac anaesthesia. Following cardiac surgery remifentanil is often substituted for alternative opioids on the intensive care unit. We were interested to evaluate postoperative continuation of remifentanil in the form of remifentanil patient control analgesia (RPCA) for those patients who received intraoperative remifentanil. The objectives of this study were to assess the safety, efficacy and feasibility of the RPCA. Ten patients who received an intravenous infusion of remifentanil perioperatively for coronary artery bypass graft surgery (CABG) had their remifentanil infusion converted to RPCA following extubation on the intensive care unit. Remifentanil patient control analgesia delivered an initial background infusion consistent with the infusion rate at extubation and with a bolus facility of 50 microg administered over 5 min followed by a 5-min lockout. Data collection included sedation and pain scores, respiratory rate, arterial blood gases, number of successful/unsuccessful attempts and the background infusion rate for each subject over a period of 12 h following extubation. The data from nine male and one female patient were analyzed by using SPSS11 for Windows. During the study period the patients achieved adequate pain control and made more RPCA attempts at lower background infusion rates. No episodes of apnoea, SpO(2) less than 95% or a rise in PaCO(2) greater than 6.5 kPa were observed. Remifentanil patient control analgesia with a background infusion was effective and safe for postoperative pain relief in this group of spontaneously breathing ICU patients following cardiac surgery.

A Comparison of the Effect of Fentanyl and Fentanyl-Nalbuphine for Postoperative Analgesia Using IV-PCA

Background: Patient-controlled analgesia (PCA) is effectively used for postoperative pain control. Fentanyl has a strong analgesic effect but has some side effects. The purpose of this study was to compare the side effects and analgesic effects of fentanyl alone and combination with nalbuphine in patients using intravenous PCA. Methods: Forty six ASA class 1 or 2 patients were randomly divided into two groups. Group F (n = 23) received fentanyl 1,200g in 100 ml of normal saline. Group NF (n = 23) received nalbupine 60 mg and fentanyl 600g in 100 ml of normal saline. All patients used the same background infusion rate (2 ml/hr), bolus dose (2 ml) and lockout interval (15 min) just after emergence from general anesthesia. The analgesic effect was evaluated by using a visual analogue scale (VAS) at 1 hr, 6 hr, 12 hr, 24 hr and 48 hr postoperatively. Side effects and satisfaction degree were also checked. Results: No significant differences were observed between the two groups in terms of pain scores and satisfaction degrees. The side effects were similar in both groups except that sedation was significantly (P ＜ 0.05) lower in group NF. Conclusions: We conclude that nalbuphine with fentanyl in combination is a useful method for intravenous PCA. On comparing the incidence of side effects in the two groups, sedation was found to be lower for the combined regimen.

Patient-controlled analgesia: an appropriate method of pain control in children.

Patient-controlled analgesia (PCA) is an analgesic technique originally used in adults but now with an established role in paediatric practice. It is well tolerated in children as young as 5 years and has uses in postoperative pain as well as burns, oncology and palliative care. The use of background infusions is more frequent in children and improves efficacy; however, it may increase the occurrence of adverse effects such as nausea and respiratory depression. Monitoring involves measurement of respiratory rate, level of sedation and oxygen saturation. Efficacy is assessed by self-reporting, visual analogue scales, faces pain scales and usage patterns. This is optimally performed both at rest and on movement. The selection of opioid used in PCA is perhaps less critical than the appropriate selection of parameters such as bolus dose, lockout and background infusion rate. Moreover, opioid choice may be based on adverse effect profile rather than efficacy. The concept of PCA continues to be developed in children, with patient-controlled epidural analgesia, subcutaneous PCA and intranasal PCA being recent extensions of the method. There may also be a role for patient-controlled sedation. PCA, when used with adequate monitoring, is a well tolerated technique with high patient and staff acceptance. It can now be regarded as a standard for the delivery of postoperative analgesia in children aged >5 years.

A review of the use of fentanyl analgesia in the management of acute pain in adults.

A review of the use of fentanyl analgesia in the management of acute pain in adults.

Continuous infusions of alfentanil and propofol for coronary artery surgery

To study the anesthetic efficacy of two different background infusion rates for alfentanil in a total intravenous anesthesia (TIVA) technique using propofol. Therefore, the effects of these infusions on hemodynamic stability and on the suppression of hemodynamic and somatic responses to noxious stimuli were compared. Prospective and randomized. The study was performed in a university hospital setting. Two patient groups were compared. Anesthesia was induced in group 1 (n = 16) with alfentanil 50 micrograms/kg and in group 2 (n = 14) with alfentanil 75 micrograms/kg, infused in 4 min, as well as with an infusion of propofol at a rate of 10 mg/kg/h in both groups. After 4 min, the alfentanil infusion was reduced to 1 microgram/kg/min in group 1 and to 2 micrograms/kg/min in group 2. The propofol infusion was reduced following sternal spread to 3 mg/kg/h. Responses indicating inadequate anesthesia were treated with additional alfentanil bolus doses. Induction of anesthesia in group 1 was associated with significant decreases in systolic and diastolic (-13%) blood pressures, cardiac index (-16%) and left ventricular stroke work index (-31%). Hemodynamic changes were similar in group 2, except for the greater fall in systemic vascular resistance during maintenance of anesthesia. There was no difference in the incidence of breakthrough hypertension between the two groups (in 44% and 43% of the patients, respectively) and in the number of alfentanil bolus supplements. There were also no differences in the incidence of ischemia, myocardial infarction or duration of postoperative ventilation. Because both infusions provided equally stable anesthesia, the lower infusion regimen for alfentanil is the more appropriate technique. Using this technique, the administration of additional alfentanil boluses just before stressful surgical episodes will further improve hemodynamic stability.

Effectiveness of sodium nitroprusside as a function of total peripheral resistance in the anesthetized dog.

To determine the influence of background vasomotor tone on the effectiveness of sodium nitroprusside in decreasing total peripheral resistance, experiments were performed on 12 open-chest dogs under halothane anesthesia. In the first experiment, the vasomotor condition of six dogs was changed by altering the background infusion rate of phenylephrine (0,40, and 0 microgram/min). Increasing background phenylephrine infusion from 0 to 40 micrograms/min significantly enhanced the effectiveness of nitroprusside in decreasing total peripheral resistance. In contrast, the effectiveness of nitroprusside in decreasing arterial pressure was not altered significantly. In a second experiment on six other dogs, phenylephrine was infused continuously at 40 micrograms/min, and the vasomotor condition was changed by the infusion of phentolamine (0, 60-100, 0 microgram/min). Phentolamine significantly diminished the effectiveness of nitroprusside in decreasing peripheral resistance. In contrast, the effectiveness of nitroprusside in decreasing arterial pressure was not altered significantly. Stepwise linear regression analysis indicated that the background peripheral resistance was the hemodynamic variable that could account partially for the changes in nitroprusside effectiveness. Increasing background total peripheral resistance significantly enhanced the effectiveness of nitroprusside in decreasing total peripheral resistance.