High-concentration supplemental perioperative oxygen to reduce the incidence of postcesarean surgical site infection: a randomized controlled trial.

OBJECTIVE: Most postcesarean infections are caused by anaerobic bacteria. Oxidative killing, an important defense against surgical infections, depends on the oxygen level in contaminated tissue. Among patients undergoing colorectal surgery, perioperative supplemental oxygen decreased infection rates by 50%. We tested the hypothesis that high-concentration inspired oxygen decreases the incidence of surgical site infection in women undergoing cesarean delivery. METHODS: Using a double blind technique, 143 women undergoing cesarean delivery under regional anesthesia after the onset of labor were randomly assigned to receive low- or high-concentration inspired oxygen via nonrebreathing mask during the operation and for 2 hours after. Surgical site infection was defined clinically as administration of antibiotics for postpartum endometritis or wound infection during the initial hospital stay or within 14 days of surgery. Interim statistical analysis was performed after 25% of the planned sample size (143 of 550) accrued using intention-to-treat principle. The stopping rule P value for futility was P>.11 with two planned interim analyses. RESULTS: Postcesarean infection occurred in 17 (25%, 95% confidence interval [CI] 15-35%) of 69 women assigned to high-concentration oxygen compared with 10 (14%, 95% CI 6-22%) of 74 women assigned to low-concentration inspired oxygen (relative risk 1.8, 95% CI 0.9-3.7, P=.13). The P value exceeded the P value for futility, suggesting these differences were unlikely to reach statistical significance with continued recruitment. CONCLUSION: High-concentration perioperative oxygen delivered through a nonrebreathing mask did not decrease the risk of postcesarean surgical site infection.

Obstetric anesthesia - then and now.

In 1947 John Bonica as new Chief of Anesthesiology at Tacoma General Hospital organized one of the first around-the-clock labor anesthesia services and when became the first chairman of the new Department of Anesthesiology at the University of Washington (1960), caudal anesthesia was the primary technique used for providing labor analgesia. In 1967 the first volume of Bonica's classic textbook ''Principles and practice of obstetric analgesia and anesthesia'' was published. The text was a comprehensive treatise that pulled together virtually everything that was known in that field. Perhaps the most significant development in obstetric anesthesia in the past 20 years has been the introduction of spinal opioid analgesia.. Bonica predicted the probable success of these techniques in the last edition of his ''Obstetric analgesia and anesthesia'' handbook published in 1980. Current obstetric anesthetic practice, though quite different from what it was 30 or 40 years ago, has its roots in the priorities, techniques and teachings of Dr. John J. Bonica.

Bilateral leg pain following lidocaine spinal anaesthesia.

Spinal anaesthesia is considered to be a safe and effective method of providing anaesthesia for a variety of surgical procedures. Recently, observations have been made that associate the use of hyperbaric lidocaine with bilateral leg pain. We report nine patients who developed strikingly similar neurological symptoms following routine spinal anaesthesia using hyperbaric lidocaine 5% solutions. All patients had their anaesthesia and surgery in the ambulatory or "short stay" care setting. In each patient, moderate to severe, bilateral, posterior, leg pain developed within 24 hr of the anaesthetic administration. The pain was described as either sharp or cramping with or without associated back pain. None of the patients demonstrated objective neurological deficits. In all cases the symptoms resolved fully within one week. The dose of lidocaine administered in these nine patients ranged from 40 to 100 mg. Although the aetiology of the symptoms is not clear the local anaesthetic or its formulation may have been responsible.

Sprotte needle for obstetric anesthesia: decreased incidence of post dural puncture headache.

BACKGROUND AND OBJECTIVES: Reports have emphasized the importance of spinal needle tip configuration in the development of post dural puncture headache (PDPH). METHODS: Charts from 366 consecutive obstetric patients receiving spinal anesthesia for labor, cesarean delivery, postpartum surgical procedures, or postpartum tubal ligations were reviewed retrospectively for evidence of PDPH in the five days after dural puncture. Spinal anesthesia was administered to these patients using 25-gauge Quincke (n = 74), 26-gauge Quincke (n = 160), or 24-gauge Sprotte (n = 132) spinal needles. RESULTS: The groups were well matched demographically. The incidence of PDPH in the three groups was 9%, 8%, and 1.5%, respectively. Half of the patients developing PDPH in each group were treated with an epidural blood patch. CONCLUSIONS: Our data indicate that the Sprotte spinal needle, with its non-cutting tip, results in a significantly lower (p less than 0.05) incidence of PDPH than Quincke cutting-tip needles of smaller gauge.

Anesthetic concerns in the patient with preeclampsia.

Preeclampsia is a disease of unknown etiology and a major contributor to maternal and neonatal morbidity and mortality. With severe preeclampsia, numerous factors including intravascular volume depletion and susceptibility of developing pulmonary edema complicate anesthetic management. Invasive monitors such as CVP or PA pressure measurements are often required for guiding fluid management. When possible, lumbar epidural blockade is the preferred method for providing analgesia and anesthesia. Under all circumstances, a collegial and collaborative approach between obstetrician and anesthesiologist facilitates optimum patient care.

A comparison of postcesarean epidural morphine analgesia by single injection and by continuous infusion.

To assess the relative efficacy and incidence of side effects of a single injection versus a continuous infusion of epidural morphine sulfate (MS) in the postcesarean population, the authors report a prospective, randomized, double-blind study. Thirty-one patients received either a 5-mg MS bolus and subsequent saline infusion (n = 13) or a 2.6-mg MS bolus and subsequent MS infusion at 0.1 mg/hour (n = 18), such that after 24 hours both groups had received a total MS dose of 5 mg. No statistically significant differences were found between the two groups in overall satisfaction with analgesia, verbal pain scores, level of activity, need for supplemental opioids, or incidence of sedation during the 24-hour study period. The authors conclude that in this population, continuous epidural morphine infusion offers no obvious advantage over single morphine bolus therapy. However, the theoretical merits of continuous opioid infusion therapy are discussed.

A comparison of obstetric and nonobstetric anesthesia malpractice claims.

Malpractice claims filed against anesthesiologists for care involving obstetric (OB) anesthesia (n = 190) were taken from the American Society of Anesthesiologists' Closed Claims Database and compared to claims not involving OB cases (n = 1351). The most common complications in the OB claims were (percentage of all OB claims): maternal death (22%), newborn brain damage (20%), and headache (12%). In contrast, the most common complications in the nonobstetric (non-OB) group were (percentage of all non-OB claims): death (39%), nerve damage (16%), and brain damage (13%). The group of OB claims contained a proportionately greater number of minor injuries, such as headache, backache, pain during anesthesia, and emotional injury (32%) compared to the non-OB claims (4%). Complications due to aspiration and convulsions were more common among the OB cases. The standard of care was judged to have been met in 46% of OB and 39% of non-OB claims. This difference is not statistically significant. Claims involving general anesthesia were more frequently associated with severe injuries and resulted in higher payments than did claims involving regional anesthesia. Payments were made in a similar proportion of OB and non-OB claims (53 and 59%, respectively). For cases in which payments were made, the median payment for OB claims was significantly greater ($203,000) than for non-OB claims ($85,000; P less than or equal to 0.05).

Aortic stenosis in pregnancy.

Aortic stenosis is uncommon during pregnancy. Five cases are described in which clinical management was facilitated by the use of Doppler echocardiography to assess the severity of disease and pulmonary artery catheterization to manage maternal hemodynamics. Regional anesthesia was used without complication. In patients with severe stenosis, significant morbidity and mortality were experienced when aortic valve replacement was delayed beyond the postpartum period.

Age predicts effective epidural morphine dose after abdominal hysterectomy.

To determine whether there is a relation between patient age and the effective dose of epidural morphine for relief of incisional pain after abdominal hysterectomy, experience treating 66 patients between the ages of 22 and 84 years was retrospectively examined. Linear regressions were plotted for age vs effective 24-hr morphine dose, age vs pain at rest, and age vs pain during coughing. To evaluate the frequency of side effects, the population was classified into three age groups (less than 40, 40-60, greater than 60 yr) and examined by Fisher's exact test for possible differences. Although there was wide interpatient variability, there was a correlation between patient age and effective 24-hr morphine dose (r = -0.40, P less than 0.01). The relation is described by the following equation: 24-hr morphine dose (mg) = 18-age(0.15). The quality of analgesia did not diminish with the smaller doses administered to the older patients. The frequency of side effects did not differ significantly in the three age groups. These observations may be related to higher CSF morphine concentrations or to a greater analgesic effect from morphine absorbed systemically from the epidural space in older patients.

Electrical correlates of brain injury resulting from severe hypotension and hemodilution in monkeys.

The effects of hypotension, hemodilution, and their combination on the relationship between concurrent brain electrical activity and resulting brain injury were studied in anesthetized monkeys. The authors compared changes in the electroencephalogram and somatosensory and auditory evoked potentials with eventual neuropathologic outcome. Our goals were: 1) to define the margin of safety for the monkey brain during hemodilution and hypotension under several simulated clinical conditions; and 2) to determine whether noninvasive measurements of brain electrical activity can predict ischemic brain cell damage. Forty-one monkeys were anesthetized with halothane (0.8 vol % inspired) and ventilated mechanically. Arterial hypotension was induced with trimethaphan (25 +/- 8 mmHg mean arterial blood pressure [MABP] for 30 min). Hemodilution was induced by replacing blood with lactated Ringer's solution (14 +/- 2% hematocrit for 1 h). Combined hemodilution and hypotension consisted of 30 min of hemodilution alone followed by superimposing hypotension for 30 min (16 +/- 3% hematocrit and 29 +/- 5 mmHg MABP). Ten monkeys died following severe hypotension alone or combined hemodilution and hypertension as a consequence of cardiac arrest or undetermined (possibly neurologic) causes. No histologic evidence of ischemic brain cell injury was found in surviving monkeys subjected to hemodilution or hypotension alone. Neuropathologic alterations in the cerebral cortex, cerebellum, hippocampus and globus pallidus as well as neurologic and behavioral deficits were found in seven of 16 surviving monkeys subjected to both hemodilution and hypotension. These findings resulted from combinations of hematocrit less than 20% and MABP below 40 mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)

Toxicity and resuscitation in lidocaine- or bupivacaine-infused cats.

Controversy persists surrounding the relative safety of bupivacaine compared with lidocaine especially with regard to its cardiovascular toxicity and the ability to resuscitate following such occurrences. The margin of safety between seizure onset and cardiovascular collapse was compared in lightly anesthetized and ventilated cats given an equipotent infusion of either lidocaine or bupivacaine (N = 10 for each group). The infusion rates were 4 mg X kg-1 X min-1 bupivacaine or 16 mg X kg-1 X min-1 lidocaine. Onset of electrical seizure activity occurred at about the same time in both groups and was defined as the central nervous system (CNS) toxic end point. The infusion continued until the mean arterial pressure reached 10 mmHg (cardiotoxic end point). Despite the early occurrence of electrocardiographic changes in the bupivacaine group, mean arterial pressure was greater and sustained significantly longer (4.9 +/- 1.3 min; mean +/- SD) with this drug compared with lidocaine (3.0 +/- 0.6 min) (P less than 0.005). Using the blood pressure criterion for defining cardiovascular (CV) collapse, the CV/CNS toxicity ratio for drug dosage was 4.0 with lidocaine and 4.8 with bupivacaine. The use of a standardized resuscitation protocol made it possible to compare the ability to resuscitate animals in each group. Despite very high plasma local anesthetic concentrations, all lidocaine-infused animals were quickly resuscitated (4.4 +/- 3.0 min; mean +/- SD). The resuscitation time for the bupivacaine group (5.4 +/- 2.4 min) was similar. Two cats in the bupivacaine group could not be brought to resuscitation criterion, a difference, however, that was not statistically significant.