Epidural anesthesia and analgesia. Their role in postoperative outcome.

We performed meta-analyses of randomized, control trials to assess the effects of seven analgesic therapies on postoperative pulmonary function after a variety of procedures: epidural opioid, epidural local anesthetic, epidural opioid with local anesthetic, thoracic versus lumbar epidural opioid, intercostal nerve block, wound infiltration with local anesthetic, and intrapleural local anesthetic. Measures of forced expiratory volume in 1 s (FEV,), forced vital capacity (FVC), vital capacity (VC), peak expiratory flow rate (PEFR), Pao,, and incidence of atelectasis, pulmonary infection, and pulmonary complications overall were analyzed. Compared with systemic opioids, epidural opioids decreased the incidence of atelectasis (risk ratio [RR] 0.53, 95% confidence interval [CI] 0.33-0.85) and had a weak tendency to reduce the incidence of pulmonaryinfections (RRO.53,95% CIO.18-1.53) and pulmonary complications overall (RR 0.51, 95% CI 0.20-1.33). Epidural local anesthetics increased Pao, (difference 4.56 mm Hg, 95% CI 0.058-9.075) and decreased the incidence of pulmonary infections (RR 0.36,95% CI 0.21-0.65) and pulmonary complications overall (RR 0.58,95% CI 0.42-0.80) compared with systemic opioids. Intercostal nerve blockade tends to improve pulmonary outcome measures (incidence of atelectasis: RR 0.65,95% CI 0.271.57, incidence of pulmonary complications overall: RR 0.47, 95% CI 0X3-1.22), but these differences did not achieve statistical significance. There were no clinically or statistically significant differences in the surrogate measures of pulmonary function (FEV,, FVC, and PEFR). These analyses support the utility of epidural analgesia for reducing postoperative pulmonary morbidity but do not support the use of surrogate measures of pulmonary outcome as predictors or determinants of pulmonary morbidity in postoperative patients. Implications: When individual trials are unable to produce significant results, it is often because of insufficient patient numbers. It may be impossible for a single institution to study enough patients. Meta-analysis is a useful tool for combining the data from multiple trials to increase the patient numbers. These meta-analyses confirm that postoperative epidural pain control can significantly decrease the incidence of pulmonary morbidity.

The comparative effects of postoperative analgesic therapies on pulmonary outcome : Cumulative meta-analyses of randomized, controlled trials

We performed meta-analyses of randomized, control trials to assess the effects of seven analgesic therapies on postoperative pulmonary function after a variety of procedures: epidural opioid, epidural local anesthetic, epidural opioid with local anesthetic, thoracic versus lumbar epidural opioid, in

The Comparative Effects of Postoperative Analgesic Therapies on Pulmonary Outcome

Pendant presque 25 ans ďexperience clinique, les benefices et les limitations de ľanesthesie a la ketamine ont ete generalement bien definis. Les revues extensives de White et al.2 ainsi que celles de Reeves et al.43 ont enormement aide a comprendre ľanesthesie dissociative. Neanmoins, des etudes recentes continuent a nous eclairer sur les differents aspects de la pharmacologie de la ketamine et suggerent de nouvelles utilisations cliniques de cette drogue. Ľidentification du recepteur du N-M ethyl-Aspartate amene une preuve que ľanesthesie et ľanalgesie a la ketamine ont chacune un mecanisme ďaction different. La liaison stereospecifique de la (+) ketamine aux recepteurs opiaces in vitro, ľemergence plus rapide de ľanesthesie, et une incidence plus basse de sequelles lors de ľemergence, rend la (+) ketamine une drogue promettante pour des recherches futures. Les applications cliniques de la ketamine qui ressortent recemment, et qui probablement augmenteront dans le futur sont reliees e ľutilisation orale, rectale et intra-nasale de la ketamine pour des fins ďanalgesie, de sedation ou induction anesthesique. La ketamine est actuellement consideree comme une option raisonnable pour ľinduction anesthesique chez les nouveau-nes prematures en hypotension. Ľexperience initiale avec la ketamine en injection epidurale et intrathecale ne fut pas prometteuse et les donnees sont encore preliminaires dans ce domaine. Ľutilisation de la ketamine dans les catastrophes et les manoeuvres militaires va probablement etre plus frequente. La disponibilite clinique du midazolam va complementer ľanesthesie a la ketamine de plusieurs facons. Cette benzodiazepine est rapidement metabolisee. Elle reduit la stimulation cardiovasculaire de la ketamine ainsi que les phenomenes ďemergence sans avoir des metabolites actifs. Elle est disponible sous une forme aqueuse et n’est pas irritante lors de ľinjection intra-veineuse comme le diazepam. La combinaison de la ketamine et du midazolam sera bien acceptee par les patients contrairement a ce qui arrive quand on utilise la ketamine seule. Finalement, il est necessaire de mentionner la possibilite ďabus de la ketamine.126 Alors que la ketamine n’est pas une substance controlee (aux Etats-Unis) la prudence suggere aux medecins de prendre des precautions appropriees contre son utilisation non-autorisee.

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Ketamine: an update on the first twenty-five years of clinical experience

Atelectasis occurs in the dependent parts of the lungs of most patients who are anesthetized. Development of atelectasis is associated with decreased lung compliance, impairment of oxygenation, increased pulmonary vascular resistance, and development of lung injury. The adverse effects of atelectasis persist into the postoperative period and can impact patient recovery. This review article focuses on the causes, nature, and diagnosis of atelectasis. The authors discuss the effects and implications of atelectasis in the perioperative period and illustrate how preventive measures may impact outcome. In addition, they examine the impact of atelectasis and its prevention in acute lung injury.

Pulmonary atelectasis: a pathogenic perioperative entity.

The effects on diaphragmatic function of a thoracic epidural block were assessed in 13 patients after upper abdominal surgery (UAS). Lung volumes and tidal changes in chest wall circumferences and gastric (delta Pgas) and esophageal (delta Pes) pressures were measured pre- and postoperatively. Volume displacement of the abdomen divided by tidal volume (delta VAB/VT) and delta Pgas/delta Pes were taken as indices of the diaphragmatic contribution to tidal breathing. These respiratory variables were obtained in the postoperative period, before and after epidural injection of 0.5% plain bupivacaine to achieve a block up to the T4 segment. UAS was constantly associated with a decrease in VT, delta VAB/VT, delta Pgas/delta Pes, and forced vital capacity (FVC). Epidural block was associated with an increase in VT, delta VAB/VT, and FVC. delta Pgas and delta Pgas/delta Pes returned to their preoperative values. It is concluded that: 1) diaphragmatic dysfunction observed after UAS is partially reversed by thoracic epidural block; and 2) that inhibitory reflexes of phrenic activity arising from the abdominal compartment (abdominal wall and/or viscera) could be involved in this diaphragmatic dysfunction.

Improvement of diaphragmatic function by a thoracic extradural block after upper abdominal surgery

An external spirometric method using a differential linear transformer was used to measure tidal volume (VT) and to determine factors influencing CO2 elimination and HFJV-induced "PEEP effect" in 15 critically ill patients under HFJV. VT increased with increasing driving pressure (DP) and decreasing frequency (f) and was influenced little by changes in I/E ratio. CO2 elimination, as reflected by the measurement of PaCO2, was mainly influenced by the absolute level of VT rather than by the product VT X frequency (PaCO2 = 5715/VT, r = 0.75, P less than 0.05). The primary phenomenon explaining HFJV-induced "PEEP effect" was intrapulmonary gas trapping due to incomplete exhalation of the first VT administered: the spontaneous relaxation times of these first VT were longer than expiratory time allotted to the ventilatory settings. HFJV-induced "PEEP effect" increased with I/E ratio, DP, and f and was markedly influenced by the mechanical properties of the total respiratory system. At given ventilatory settings, HFJV-induced "PEEP effect" was greater in patients with a normal or elevated time constant of the total respiratory system (tau RS) than in patients with a low tau RS. These results suggest that HFJV should not be used in patients with chronic obstructive pulmonary disease and asthma, and should be preferentially administered to patients having stiff lungs or decreased chest wall compliance.

Factors influencing pulmonary volumes and CO2 elimination during high-frequency jet ventilation.

The effects of anesthetic doses of ketamine (iv bolus of 3 mg X kg-1 followed by a continuous infusion of 20 micrograms X kg-1 X min-1) on functional residual capacity (FRC) measured by the helium dilution method and on the breathing pattern recorded by a noninvasive method (NIM) based on chest wall circumference changes were studied in 14 ASA P.S. I patients. Ketamine anesthesia was associated with: 1) the maintenance of FRC, minute ventilation, and tidal volume; 2) an increase in rib cage contribution to tidal breathing; and 3) an alteration of volume-motion relationships of the chest wall compartments. It is concluded that: 1) in contrast to volatile anesthetic agents, ketamine anesthesia has a sparing effect on intercostal muscle activity, which may explain the maintenance of FRC; and 2) changes in chest wall geometry and compliance induced by anesthetic agents must be taken into account for NIM to be valid.

R. Sartene

Papers

Improvement of diaphragmatic function by a thoracic extradural block after upper abdominal surgery

Factors influencing pulmonary volumes and CO2 elimination during high-frequency jet ventilation.

Ventilatory Pattern and Chest Wall Mechanics during Ketamine Anesthesia in Humans

Ventilatory Pattern and Chest Wall Mechanics During Isoflurane Anesthesia

Factors influencing tidal volume during high-frequency jet ventilation