Craig M. Palmer

Dose-Response Relationship of Intrathecal Morphine for Postcesarean Analgesia

BACKGROUND This series investigated the quality of analgesia and the incidence and severity of side effects of intrathecal morphine for post-cesarean analgesia administered over a dose range of 0.0-0.5 mg. METHODS ONE hundred eight term parturients undergoing cesarean delivery at term and given spinal anesthesia were randomized to receive a single dose of intrathecal morphine (0.0, 0.025, 0.05, 0.075, 0.1, 0.2, 0.3, 0.4, or 0.5 mg). A patient-controlled analgesia (PCA) device provided free access to additional analgesics. PCA morphine use, incidence and severity of side effects, and need for treatment interventions were recorded for 24 h. Data were analyzed with analysis of variance and linear regression analysis for trends among groups. RESULTS Patient-controlled analgesia use differed significantly between groups; PCA use was higher in the control group than in groups receiving 0.075, 0.1, 0.3, 0.4, or 0.5 mg. Twenty-four-hour PCA morphine use was 45.7 mg lower (95% CI, 4.8-86.6 mg lower) in the 0.075-mg group than the control group. There was no difference in PCA morphine use between the 0.075- and 0.5-mg groups (95% CI, 36.8 mg lower to 45.0 mg higher); despite a fivefold increase in intrathecal morphine dose, PCA morphine use remained constant. There was no difference between control and treatment groups or among treatment groups with respect to nausea and vomiting. Pruritus and the need for treatment interventions increased in direct proportion to the dose of intrathecal morphine (linear regression, P = 0.001 and P = 0.0002, respectively). CONCLUSIONS These data indicate there is little justification for use of more than 0.1 mg for post-cesarean analgesia. For optimal analgesia, augmentation [corrected] of intrathecal morphine with systemic opioids may be necessary.

Practice guidelines for the prevention, detection, and management of respiratory depression associated with neuraxial opioid administration.

PRACTICE guidelines are systematically developed recommendations that assist the practitioner and patient in making decisions about health care. These recommendations may be adopted, modified, or rejected according to clinical needs and constraints, and are not intended to replace local institutional policies. In addition, practice guidelines developed by the American Society of Anesthesiologists (ASA) are not intended as standards or absolute requirements, and their use cannot guarantee any specific outcome. Practice guidelines are subject to revision as warranted by the evolution of medical knowledge, technology, and practice. They provide basic recommendations that are supported by a synthesis and analysis of the current literature, expert and practitioner opinion, open forum commentary, and clinical feasibility data. This document updates the “Practice Guidelines for the Prevention, Detection and Management of Respiratory Depression Associated with Neuraxial Opioid Administration” adopted by ASA in 2007, and includes new survey data and recommendations pertaining to monitoring for respiratory depression. Methodology

The dose-response relation of intrathecal fentanyl for labor analgesia.

Background This study determined the dose‐response relation of intrathecal fentanyl for labor analgesia and described the onset, duration, and quality of analgesia when used as the sole analgesic. Methods Eighty‐four parturients in active labor who requested analgesia were randomized to one of seven treatment groups. They received 5–45 micro gram intrathecal fentanyl as part of a combined spinal‐epidural technique. Visual analog pain scores were recorded before and at intervals after injection patients requested additional analgesia. The occurrence and severity of pruritus, nausea, and vomiting were also recorded. Maternal blood pressure was recorded before injection and at intervals after injection. Fetal heart rate was recorded before and 30 min after injection. Results By 5 min after injection, pain scores were significantly different among groups (P < 0.001). Mean duration of analgesia increased to 89 min as the dose increased to 25 micro gram. Maternal diastolic blood pressure was significantly lower 10 and 30 min after injection. There was no difference among groups in the incidence of pruritus; nausea and vomiting were uncommon. Fetal heart rates did not change after injection. A dose‐response curve indicates that the median effective dose of intrathecal fentanyl for labor analgesia is 14 micro gram (95% confidence interval, 13–15 micro gram). Conclusions Intrathecal fentanyl produces rapid, profound labor analgesia with minimal side effects. These data indicate that there is little benefit to increasing the dose beyond 25 micro gram when it is used as the sole agent for intrathecal labor analgesia.

Single-Dose, Sustained-Release Epidural Morphine in the Management of Postoperative Pain After Elective Cesarean Delivery: Results of a Multicenter Randomized Controlled Study

In this multicenter, randomized, controlled study, we compared the analgesic efficacy and safety profile of a new single-dose extended-release epidural morphine (EREM) formulation (DepoDur™) with that of epidural morphine sulfate for the management of postoperative pain for up to 48 h after elective cesarean delivery. ASA physical status I or II parturients (n = 75) were anesthetized with a combined spinal/epidural technique. Parturients received intrathecal bupivacaine 12–15 mg and fentanyl 10 &mgr;g for spinal anesthesia and a single epidural injection of either 5 mg of standard (conventional preservative-free) morphine or 5, 10, or 15 mg of extended-release morphine after cord clamping for postoperative pain control. Single-dose EREM 10 and 15 mg groups significantly decreased total supplemental opioid medication use and improved functional ability scores for 48 h after surgery compared with those receiving 5 mg of standard morphine. Visual analog scale pain scores at rest and with activity at 24 to 48 h after dosing were significantly better in the 10- and 15-mg single-dose EREM groups versus the standard morphine group. There were no significant differences between the two 5 mg (single-dose EREM and standard morphine) groups. Single-dose EREM was well tolerated, and most adverse events were mild to moderate in severity. Single-dose EREM is a potentially beneficial epidural analgesic for the management of post-cesarean delivery pain and has particular advantages over standard morphine for the period from 24 to 48 h after surgery.

Postcesarean epidural morphine: a dose-response study.

The purpose of this study was to describe the dose-response relationship of epidural morphine for postcesarean analgesia for quality of analgesia and relation to the side effects of pruritus, nausea, and vomiting. Sixty term parturients undergoing nonurgent cesarean delivery were enrolled and randomized to receive a single dose of epidural morphine after delivery (0,1.25, 2.5, 3.75, or 5 mg). A patient-controlled analgesia (PCA) device provided free access to additional analgesics. PCA morphine use and the incidence and severity of side effects were recorded for 24 h. Data were analyzed with analysis of variance, Student’s t-tests, and &khgr;2 analysis. Nonlinear regression was used to describe a dose-response curve. PCA use differed significantly among groups (P < 0.001); PCA use was significantly greater in Group 0 mg than Groups 2.5, 3.75, and 5 mg (P < 0.05). PCA use was also significantly greater in Group 1.25 mg than Groups 3.75 and 5 mg (P < 0.05). Pruritus scores were significantly higher in all groups given epidural morphine than the control group (0 mg) (P < 0.05), but did not differ among the treatment groups (1.25–5 mg), although pruritus scores were significantly higher in treatment groups than in the control (P < 0.05). No relation was found between epidural morphine dose and incidence or severity of nausea and vomiting. We concluded that, for optimal analgesia, augmentation of epidural morphine with systemic analgesics or other epidural medications may be necessary. Implications: Quality of analgesia increases as the dose of epidural morphine increases to at least 3.75 mg; increasing the dose further to 5 mg did not improve analgesia. Side effects were not dose related. For optimal analgesia, augmentation of epidural morphine with systemic analgesics or other epidural medications may be necessary.

Practice advisory for the prevention, diagnosis, and management of infectious complications associated with neuraxial techniques: A report by the american society of anesthesiologists task force on infectious complications associated with neuraxial techniques

P RACTICE advisories are systematically developed reports that are intended to assist decision making in areas of patient care. Advisories are based on a synthesis of scientific literature and analysis of expert opinion, clinical feasibility data, open forum commentary, and consensus surveys. Advisories developed by the American Society of Anesthesiologists (ASA) are not intended as standards, guidelines, or absolute requirements. They may be adopted, modified, or rejected according to clinical needs and constraints. The use of practice advisories cannot guarantee any specific outcome. Practice advisories summarize the state of the literature and report opinions obtained from expert consultants and ASA members. Practice advisories are not supported by scientific literature to the same degree as standards or guidelines because of the lack of sufficient numbers of adequately controlled studies. Practice advisories are subject to periodic revision as warranted by the evolution of medical knowledge, technology, and practice. Methodology

Incidence of electrocardiographic changes during cesarean delivery under regional anesthesia.

Serial electrocardiograms were obtained on 93 healthy ASA physical status I and II term parturients during nonemergent cesarean delivery under regional anesthesia. Electrocardiographic changes occurred in 44 of the 93 patients (47.3%); in 35 of these 44 patients, the changes were characteristic, or suggestive, of myocardial ischemia. Symptoms of chest pain, pressure, and dyspnea occurred in 15 of the 44 patients with electrocardiographic changes; no patient without electrocardiographic change developed symptoms of chest pain, pressure, or dyspnea. Small but statistically significant differences were noted in heart rate, diastolic and systolic arterial pressures, and rate-pressure product between the patients with electrocardiographic changes and those without. The authors speculate that myocardial ischemia is a likely cause of both the electrocardiographic changes seen in these patients and of the symptoms of chest pain and dyspnea that they sometimes experience.

Early Respiratory Depression Following Intrathecal Fentanyl-Morphine Combination

Recent reports regarding the use of intrathecal fentanyl and of opioid combinations including fentanyl in obstetric patients have indicated they may have advantages over morphine while having a lower risk of respiratory depression. The following case report illustrates that this perceived safety may be unwarranted

A Randomized, Double-masked, Multicenter Comparison of the Safety of Continuous Intrathecal Labor Analgesia Using a 28-Gauge Catheter versus Continuous Epidural Labor Analgesia

Background:Continuous intrathecal labor analgesia produces rapid analgesia or anesthesia and allows substantial flexibility in medication choice. The US Food and Drug Administration, in 1992, removed intrathecal microcatheters (27–32 gauge) from clinical use after reports of neurologic injury in nonobstetric patients. This study examined the safety and efficacy of a 28-gauge intrathecal catheter for labor analgesia in a prospective, randomized, multicenter trial. Methods:Laboring patients were randomly assigned to continuous intrathecal analgesia with a 28-gauge catheter (n = 329) or continuous epidural analgesia with a 20-gauge catheter (n = 100), using bupivacaine and sufentanil. The primary outcome was the incidence of neurologic complications, as determined by masked neurologic examinations at 24 and 48 h postpartum, plus telephone follow-up at 7–10 and 30 days after delivery. The secondary outcomes included adequacy of labor analgesia, maternal satisfaction, and neonatal status. Results:No patient had a permanent neurologic change. The continuous intrathecal analgesia patients had better early analgesia, less motor blockade, more pruritus, and higher maternal satisfaction with pain relief at 24 h postpartum. The intrathecal catheter was significantly more difficult to remove. There were no significant differences between the two groups in neonatal status, post–dural puncture headache, hemodynamic stability, or obstetric outcomes. Conclusions:Providing intrathecal labor analgesia with sufentanil and bupivacaine via a 28-gauge catheter has an incidence of neurologic complication less than 1%, and produces better initial pain relief and higher maternal satisfaction, but is associated with more technical difficulties and catheter failures compared with epidural analgesia.

Continuous Spinal Anesthesia and Analgesia in Obstetrics

The development of the technique of continuous spinal anesthesia as it relates to the obstetric population is recounted. The advantages and disadvantages of continuous spinal anesthesia are examined, currently available catheters and kits are reviewed, and strategies for the management of continuous spinal techniques for labor analgesia and surgical anesthesia are discussed. Continuous spinal anesthesia may have particular value over other regional techniques in several specific clinical circumstances.