Steen Winther Henneberg

Effect of high perioperative oxygen fraction on surgical site infection and pulmonary complications after abdominal surgery: the PROXI randomized clinical trial.

CONTEXTnUse of 80% oxygen during surgery has been suggested to reduce the risk of surgical wound infections, but this effect has not been consistently identified. The effect of 80% oxygen on pulmonary complications has not been well defined.nnnOBJECTIVEnTo assess whether use of 80% oxygen reduces the frequency of surgical site infection without increasing the frequency of pulmonary complications in patients undergoing abdominal surgery.nnnDESIGN, SETTING, AND PATIENTSnThe PROXI trial, a patient- and observer-blinded randomized clinical trial conducted in 14 Danish hospitals between October 2006 and October 2008 among 1400 patients undergoing acute or elective laparotomy.nnnINTERVENTIONSnPatients were randomly assigned to receive either 80% or 30% oxygen during and for 2 hours after surgery.nnnMAIN OUTCOME MEASURESnSurgical site infection within 14 days, defined according to the Centers for Disease Control and Prevention. Secondary outcomes included atelectasis, pneumonia, respiratory failure, and mortality.nnnRESULTSnSurgical site infection occurred in 131 of 685 patients (19.1%) assigned to receive 80% oxygen vs 141 of 701 (20.1%) assigned to receive 30% oxygen (odds ratio [OR], 0.94; 95% confidence interval [CI], 0.72-1.22; P = .64). Atelectasis occurred in 54 of 685 patients (7.9%) assigned to receive 80% oxygen vs 50 of 701 (7.1%) assigned to receive 30% oxygen (OR, 1.11; 95% CI, 0.75-1.66; P = .60), pneumonia in 41 (6.0%) vs 44 (6.3%) (OR, 0.95; 95% CI, 0.61-1.48; P = .82), respiratory failure in 38 (5.5%) vs 31 (4.4%) (OR, 1.27; 95% CI, 0.78-2.07; P = .34), and mortality within 30 days in 30 (4.4%) vs 20 (2.9%) (OR, 1.56; 95% CI, 0.88-2.77; P = .13).nnnCONCLUSIONnAdministration of 80% oxygen compared with 30% oxygen did not result in a difference in risk of surgical site infection after abdominal surgery.nnnTRIAL REGISTRATIONnclinicaltrials.gov Identifier: NCT00364741.

Academic performance in adolescence after inguinal hernia repair in infancy: a nationwide cohort study.

BACKGROUNDnAlthough animal studies have indicated that general anesthetics may result in widespread apoptotic neurodegeneration and neurocognitive impairment in the developing brain, results from human studies are scarce. We investigated the association between exposure to surgery and anesthesia for inguinal hernia repair in infancy and subsequent academic performance.nnnMETHODSnUsing Danish birth cohorts from 1986-1990, we compared the academic performance of all children who had undergone inguinal hernia repair in infancy to a randomly selected, age-matched 5% population sample. Primary analysis compared average test scores at ninth grade adjusting for sex, birth weight, and paternal and maternal age and education. Secondary analysis compared the proportions of children not attaining test scores between the two groups.nnnRESULTSnFrom 1986-1990 in Denmark, 2,689 children underwent inguinal hernia repair in infancy. A randomly selected, age-matched 5% population sample consists of 14,575 individuals. Although the exposure group performed worse than the control group (average score 0.26 lower; 95% CI, 0.21-0.31), after adjusting for known confounders, no statistically significant difference (-0.04; 95% CI, -0.09 to 0.01) between the exposure and control groups could be demonstrated. However, the odds ratio for test score nonattainment associated with inguinal hernia repair was 1.18 (95% CI, 1.04-1.35). Excluding from analyses children with other congenital malformations, the difference in mean test scores remained nearly unchanged (0.05; 95% CI, 0.00-0.11). In addition, the increased proportion of test score nonattainment within the exposure group was attenuated (odds ratio = 1.13; 95% CI, 0.98-1.31).nnnCONCLUSIONnIn the ethnically and socioeconomically homogeneous Danish population, we found no evidence that a single, relatively brief anesthetic exposure in connection with hernia repair in infancy reduced academic performance at age 15 or 16 yr after adjusting for known confounding factors. However, the higher test score nonattainment rate among the hernia group could suggest that a subgroup of these children are developmentally disadvantaged compared with the background population.

Comparison of conventional averaged and rapid averaged, autoregressive-based extracted auditory evoked potentials for monitoring the hypnotic level during propofol induction.

Background The extraction of the middle latency auditory evoked potentials (MLAEP) is usually done by moving time averaging (MTA) over many sweeps (often 250–1,000), which could produce a delay of more than 1 min. This problem was addressed by applying an autoregressive model with exogenous input (ARX) that enables extraction of the auditory evoked potentials (AEP) within 15 sweeps. The objective of this study was to show that an AEP could be extracted faster by ARX than by MTA and with the same reliability. Methods The MTA and ARX methods were compared with the Modified Observers Assessment of Alertness and Sedation Scale (MOAAS) in 15 patients scheduled for cardiac surgery and anesthetized with propofol. The peak amplitudes and latencies were recorded continuously for the MTA- and ARX-extracted AEP. An index, AAI, was derived from the ARX-extracted AEP as well. Results The best predictors of the awake and anesthetized states, in terms of the prediction probability, Pk, were the AAI (Pk [SE] = 0.93 [0.01]) and Na-Pa amplitude (MTA, Pk [SE] = 0.89 [0.02]; ARX, Pk [SE] = 0.87[0.02]). When comparing the AAI at the MOAAS levels 5–3 versus 2–0, significant differences were achieved. During the transitions from awake to asleep, the ARX-extracted AEP were obtained with significantly less delay than the MTA-extracted AEP (28.4 s vs. 6 s). Conclusion The authors conclude that the MLAEP peaks and the AAI correlate well to the MOAAS, whether extracted by MTA or ARX, but the ARX method produced a significantly shorter delay than the MTA.

Educational outcome in adolescence following pyloric stenosis repair before 3 months of age: a nationwide cohort study

Immature animals exposed to anesthetics display apoptotic neurodegeneration with subsequent long‐term cognitive dysfunctions. Young age at anesthetic exposure is believed to be critical, but human studies are scarce. This study investigated the association between exposure to surgery and anesthesia for pyloric stenosis (PS) before 3 months of age and subsequent educational outcome in adolescence.

Comparison of auditory evoked potentials and the A‐line ARX Index for monitoring the hypnotic level during sevoflurane and propofol induction

Background: Extraction of the middle latency auditory evoked potentials (AEP) by an auto regressive model with exogenous input (ARX) enables extraction of the AEP within 1.7u2003s. In this way, the depth of hypnosis can be monitored at almost real‐time. However, the identification and the interpretation of the appropriate signals of the AEP could be difficult to perform during the anesthesia procedure. This problem was addressed by defining an index which reflected the peak amplitudes and latencies of the AEP, developed to improve the clinical interpretation of the AEP. This index was defined as the A‐line Arx Index (AAI).

Thermodilution versus inert gas rebreathing for estimation of effective pulmonary blood flow.

Objective: To compare measurements of the effective pulmonary blood flow (&OV0422;ep, i.e., nonshunted fraction of cardiac output, &OV0422;t) by the inert gas rebreathing (RB) method and the thermodilution (TD) technique in critically ill patients. Design: Prospective, comparative study of a noninvasive method and an established invasive technique. Setting: An 11‐bed general intensive care unit in a university hospital. Patients: A total of 14 critically ill patients, all mechanically ventilated and monitored with systemic and pulmonary artery catheters. Measurements and Main Results: &OV0422;ep was determined in duplicate by RB using a mass spectrometer for gas analysis. For each determination, &OV0422;t was measured in triplicate by the cold water bolus TD technique and averaged. Simultaneously mixed venous and arterial blood samples were analyzed to calculate the intrapulmonary shunt fraction and thereby convert estimates of &OV0422;t to &OV0422;ep. Mean difference between paired estimates (RB ‐ TD) was 0.01 L/min, so for differences was 1.19 L/min, and 95% confidence interval for the bias was −0.45 to 0.47 L/min. Coefficients of variation for repeated &OV0422;ep estimates were 8% (RB) and 12% (TD), respectively. Coefficients of variation for RB estimates of functional residual capacity and lung tissue volume were 6% and 17%, respectively. Conclusions: The RB method is a promising method for simultaneous noninvasive estimation of &OV0422;ep and functional residual capacity in mechanically ventilated patients. However, further investigations are needed to evaluate potential problems of the method before it can be recommended for clinical purposes.

Perioperative oxygen fraction – effect on surgical site infection and pulmonary complications after abdominal surgery: a randomized clinical trial. Rationale and design of the PROXI-Trial

BackgroundA high perioperative inspiratory oxygen fraction may reduce the risk of surgical site infections, as bacterial eradication by neutrophils depends on wound oxygen tension. Two trials have shown that a high perioperative inspiratory oxygen fraction (FiO2 = 0.80) significantly reduced risk of surgical site infections after elective colorectal surgery, but a third trial was stopped early because the frequency of surgical site infections was more than doubled in the group receiving FiO2 = 0.80. It has not been settled if a high inspiratory oxygen fraction increases the risk of pulmonary complications, such as atelectasis, pneumonia and respiratory failure. The aim of our trial is to assess the potential benefits and harms of a high perioperative oxygen fraction in patients undergoing abdominal surgery.Methods and designThe PROXI-Trial is a randomized, patient- and assessor blinded trial of perioperative supplemental oxygen in 1400 patients undergoing acute or elective laparotomy in 14 Danish hospitals. Patients are randomized to receive either 80% oxygen (FiO2 = 0.80) or 30% oxygen (FiO2 = 0.30) during surgery and for the first 2 postoperative hours. The primary outcome is surgical site infection within 14 days. The secondary outcomes are: atelectasis, pneumonia, respiratory failure, re-operation, mortality, duration of postoperative hospitalization, and admission to intensive care unit. The sample size allows detection of a 33% relative risk reduction in the primary outcome with 80% power.DiscussionThis trial assesses benefits and harms of a high inspiratory oxygen fraction, and the trial may be generalizable to a general surgical population undergoing laparotomy.Trial registrationClinicalTrials.gov identifier: NCT00364741.

Peroperative depth of anaesthesia may influence postoperative opioid requirements

Background:u2002 Studies on monitoring the depth of anaesthesia have shown that with the use of these monitors the peroperative consumption of anaesthetics can be reduced. Studies have also indicated that the peroperative depth of anaesthesia may affect the postoperative course. The purpose of this study was to evaluate a possible relation between the depths of anaesthesia and the postoperative pain score and consumption of morphine.

Accuracy of a new bedside method for estimation of circulating blood volume

To evaluate the accuracy of a modification of the carbon monoxide method of estimating the circulating blood volume. Design:Prospective, clinical study comparing two methods for estimating the circulating blood volume. Carbon monoxide kinetics were studied by computer simulation. Setting:Intensive care unit in a university hospital. Patients:Intensive care patients receiving intermittent positive-pressure ventilation and healthy volunteers. Measurements and Main Results:The circulating blood volume was determined from measurements of the carbon monoxide saturation of hemoglobin before and after rebreathing a gas mixture containing 20 to 50 mL of carbon monoxide for a period of 10 to 15 mins. A specially designed Waters “to & fro” system was developed to avoid any leakage during intermittent positive-pressure ventilation. Blood samples were taken before, during, and immediately after rebreathing. The amount of carbon monoxide administrated during each rebreathing maneuver resulted in an average increase in the carbon monoxide saturation of hemoglobin of 3.6%. The washin of carbon monoxide was completed within the first 4 to 6 mins of the rebreathing period in nine healthy subjects and within 10 mins in 12 intensive care patients. The 95% limits of agreement between the carbon monoxide method and the radioactive isotope-labeling method was ±540 mL (±2 SD). Conclusion:Determination of circulating blood volume can be performed with sufficient accuracy using an amount of carbon monoxide that gives rise to an unharmful increase in the carboxyhemoglobin concentration. (Crit Care Med 1993; 21:1535–1540)

Intranasal sufentanil/ketamine analgesia in children

The management of procedural pain in children ranges from physical restraint to pharmacological interventions. Pediatric formulations that permit accurate dosing, are accepted by children and a have a rapid onset of analgesia are lacking.