Dirk Varelmann

Nocebo-induced hyperalgesia during local anesthetic injection.

Common practice during local anesthetic injection is to warn the patient using words such as: “You will feel a big bee sting; this is the worst part.” Our hypothesis was that using gentler words for administration of the local anesthetic improves pain perception and patient comfort. One hundred forty healthy women at term gestation requesting neuraxial analgesia were randomized to either a “placebo” (“We are going to give you a local anesthetic that will numb the area and you will be comfortable during the procedure”) or “nocebo” (“You are going to feel a big bee sting; this is the worst part of the procedure”) group. Pain was assessed immediately after the local anesthetic skin injection using verbal analog scale scores of 0 to 10. Median verbal analog scale pain scores were lower when reassuring words were used compared with the harsher nocebo words (3 [2–4] vs 5 [3–6]; P < 0.001). Our data suggest that using gentler, more reassuring words improves the subjective experience during invasive procedures.

Electrical impedance tomography compared with thoracic computed tomography during a slow inflation maneuver in experimental models of lung injury

Objective:To determine the validity of functional electric impedance tomography to monitor regional ventilation distribution in experimental acute lung injury, and to develop a simple electric impedance tomography index detecting alveolar recruitment. Design:Randomized prospective experimental study. Setting:Academic research laboratory. Subjects:Sixteen anesthetized, tracheotomized, and mechanically ventilated pigs. Interventions:Acute lung injury was induced either by acid aspiration (direct acute lung injury) or by abdominal hypertension plus oleic acid injection (indirect acute lung injury) in ten pigs. Six pigs with normal lungs were studied as a control group and with endotracheal suction-related atelectasis. After 4 hrs of mechanical ventilation, a slow inflation was performed. Measurements and Main Results:During slow inflation, simultaneous measurements of regional ventilation by electric impedance tomography and dynamic computed tomography were highly correlated in quadrants of a transversal thoracic plane (r2 = .63–.88, p < .0001, bias <5%) in both direct and indirect acute lung injury. Variability between methods was lower in direct than indirect acute lung injury (11 ± 2% vs. 18 ± 3%, respectively, p < .05). Electric impedance tomography indexes to detect alveolar recruitment were determined by mathematical curve analysis of regional impedance time curves. Empirical tests of different methods revealed that regional ventilation delay, that is, time delay of regional impedance time curve to reach a threshold, correlated well with recruited volume as measured by CT (r2 = .63). Correlation coefficients in subgroups were r2 = .71 and r2 = .48 in pigs with normal lungs with and without closed suction related atelectasis and r2 = .79 in pigs subject to indirect acute lung injury, respectively, whereas no significant correlation was found in pigs undergoing direct acute lung injury. Conclusions:Electric impedance tomography allows assessment of regional ventilation distribution and recruitment in experimental models of direct and indirect acute lung injury as well as normal lungs. Except for pigs with direct acute lung injury, regional ventilation delay determined during a slow inflation from impedance time curves appears to be a simple index for clinical monitoring of alveolar recruitment.

The impact of spontaneous breathing during mechanical ventilation.

Purpose of reviewIn patients with acute respiratory distress syndrome, controlled mechanical ventilation is generally used in the initial phase to ensure adequate alveolar ventilation, arterial oxygenation, and to reduce work of breathing without causing further damage to the lungs. Although introduced as weaning techniques, partial ventilator support modes have become standard techniques for primary mechanical ventilator support. This review evaluates the physiological and clinical effects of persisting spontaneous breathing during ventilator support in patients with acute respiratory distress syndrome. Recent findingsThe improvements in pulmonary gas exchange, systemic blood flow and oxygen supply to the tissue which have been observed when spontaneous breathing has been maintained during mechanical ventilation are reflected in the clinical improvement in the patients condition. Computer tomography observations demonstrated that spontaneous breathing improves gas exchange by redistribution of ventilation and end-expiratory gas to dependent, juxtadiaphragmatic lung regions and thereby promotes alveolar recruitment. Thus, spontaneous breathing during ventilator support counters the undesirable cyclic alveolar collapse in dependent lung regions. In addition, spontaneous breathing during ventilator support may prevent increase in sedation beyond a level of comfort to adapt the patient to mechanical ventilation which decreases duration of mechanical ventilator support, length of stay in the intensive care unit, and overall costs of care giving. SummaryIn view of the recently available data, it can be concluded that maintained spontaneous breathing during mechanical ventilation should not be suppressed even in patients with severe pulmonary functional disorders.

Extended therapeutic hypothermia for several days during extracorporeal membrane-oxygenation after drowning and cardiac arrest Two cases of survival with no neurological sequelae.

Drowning associated with hypothermia and cardiopulmonary resuscitation has a very poor prognosis. We report two such cases, where impossible oxygenation due to severe pulmonary oedema was treated with extracorporeal membrane-oxygenation (ECMO). Following cardiac arrest, mild therapeutic hypothermia for 24h was maintained as recommended, but subsequent rewarming precipitated additional pulmonary oedema. Little is currently known about how long to maintain therapeutic hypothermia to optimize neurological outcome and suppress reperfusion injury. In our patients, therapeutic hypothermia during veno-venous ECMO-treatment was extended for up to 6 days. Both patients survived with no neurological sequelae. We speculate that prolonged hypothermia was not only neuroprotective, but also minimized reperfusion injury including pulmonary oedema. Extension of hypothermia for several days seems safe and feasible in selected cases.

Cardiorespiratory effects of spontaneous breathing in two different models of experimental lung injury : a randomized controlled trial

IntroductionAcute lung injury (ALI) can result from various insults to the pulmonary tissue. Experimental and clinical data suggest that spontaneous breathing (SB) during pressure-controlled ventilation (PCV) in ALI results in better lung aeration and improved oxygenation. Our objective was to evaluate whether the addition of SB has different effects in two different models of ALI.MethodsForty-four pigs were randomly assigned to ALI resulting either from hydrochloric acid aspiration (HCl-ALI) or from increased intra-abdominal pressure plus intravenous oleic acid injections (OA-ALI) and were ventilated in PCV mode either with SB (PCV + SB) or without SB (PCV – SB). Cardiorespiratory variables were measured at baseline after induction of ALI and after 4 hours of treatment (PCV + SB or PCV – SB). Finally, density distributions and end-expiratory lung volume (EELV) were assessed by thoracic spiral computed tomography.ResultsPCV + SB improved arterial partial pressure of oxygen/inspiratory fraction of oxygen (PaO2/FiO2) by a reduction in intrapulmonary shunt fraction in HCl-ALI from 27% ± 6% to 23% ± 13% and in OA-ALI from 33% ± 19% to 26% ± 18%, whereas during PCV – SB PaO2/FiO2 deteriorated and shunt fraction increased in the HCl group from 28% ± 8% to 37% ± 17% and in the OA group from 32% ± 12% to 47% ± 17% (P < 0.05 for interaction time and treatment, but not ALI type). PCV + SB also resulted in higher EELV (HCl-ALI: 606 ± 171 mL, OA-ALI: 439 ± 90 mL) as compared with PCV – SB (HCl-ALI: 372 ± 130 mL, OA-ALI: 192 ± 51 mL, with P < 0.05 for interaction of time, treatment, and ALI type).ConclusionsSB improves oxygenation, reduces shunt fraction, and increases EELV in both models of ALI.

Rescue transoesophageal echocardiography for refractory haemodynamic instability during transvenous lead extraction.

AIMS The rising number of cardiovascular implantable electronic devices has led to a steep increase in transvenous lead extractions (TLEs). Procedure-related, haemodynamically significant adverse events are uncommon during TLE yet remain an inevitable risk. While the use of transoesophageal echocardiography (TEE) as a guide to clinical decision-making during refractory circulatory instability has been well established, the specific utility of rescue TEE during TLE has not been comprehensively studied. METHODS AND RESULTS Twenty-six patients who required emergent TEE to determine the aetiology of intractable haemodynamic instability during TLE were evaluated. Pericardial effusion requiring urgent pericardiocentesis and/or cardiac surgical intervention was diagnosed by TEE in 10 patients, and progressed to cardiac arrest in 4 patients. Haemorrhagic shock developed in two patients suffering from femoral vein laceration and right haemothorax, respectively. One additional patient developed acute respiratory compromise and right ventricular dysfunction diagnosed by TEE, which necessitated prolonged post-operative intubation and inotropic therapy. In 14 patients, TEE excluded life-threatening cardiovascular injuries and enabled the pursuit of continued medical management. Two patients with reassuring TEE findings underwent intra-operative placement of chest tubes for pneumothorax. All the 26 patients were discharged from the hospital. CONCLUSION While TLE is a relatively safe procedure, life-threatening cardiovascular injuries remain a rare risk. In this study, the use of rescue TEE ruled out significant cardiovascular injuries in the majority of patients. Furthermore, rescue TEE had a substantial impact on the efficiency of determining the aetiology of refractory haemodynamic instability during TLE and thereby facilitated the timely initiation of definitive intervention.

A Comparison of Web-Based with Traditional Classroom-Based Training of Lung Ultrasound for the Exclusion of Pneumothorax

BACKGROUND:Lung ultrasound (LUS) is a well-established method that can exclude pneumothorax by demonstration of pleural sliding and the associated ultrasound artifacts. The positive diagnosis of pneumothorax is more difficult to obtain and relies on detection of the edge of a pneumothorax, called the “lung point.” Yet, anesthesiologists are not widely taught these techniques, even though their patients are susceptible to pneumothorax either through trauma or as a result of central line placement or regional anesthesia techniques performed near the thorax. In anticipation of an increased training demand for LUS, efficient and scalable teaching methods should be developed. In this study, we compared the improvement in LUS skills after either Web-based or classroom-based training. We hypothesized that Web-based training would not be inferior to “traditional” classroom-based training beyond a noninferiority limit of 10% and that both would be superior to no training. Furthermore, we hypothesized that this short training session would lead to LUS skills that are similar to those of ultrasound-trained emergency medicine (EM) physicians. METHODS:After a pretest, anesthesiologists from 4 academic teaching hospitals were randomized to Web-based (group Web), classroom-based (group class), or no training (group control) and then completed a posttest. Groups Web and class returned for a retention test 4 weeks later. All 3 tests were similar, testing both practical and theoretical knowledge. EM physicians (group EM) performed the pretest only. Teaching for group class consisted of a standardized PowerPoint lecture conforming to the Consensus Conference on LUS followed by hands-on training. Group Web received a narrated video of the same PowerPoint presentation, followed by an online demonstration of LUS that also instructs the viewer to perform an LUS on himself using a clinically available ultrasound machine and submit smartphone snapshots of the resulting images as part of a portfolio system. Group Web received no other hands-on training. RESULTS:Groups Web, class, control, and EM contained 59, 59, 20, and 42 subjects. After training, overall test results of groups Web and class improved by a mean of 42.9% (±18.1% SD) and 39.2% (±19.2% SD), whereas the score of group control did not improve significantly. The test improvement of group Web was not inferior to group class. The posttest scores of groups Web and class were not significantly different from group EM. In comparison with the posttests, the retention test scores did not change significantly in either group. CONCLUSIONS:When training anesthesiologists to perform LUS for the exclusion of pneumothorax, we found that Web-based training was not inferior to traditional classroom-based training and was effective, leading to test scores that were similar to a group of clinicians experienced in LUS.

“Proportional assist ventilation” kombiniert mit “automatic tube compensation”

Zusammenfassung“Proportional assist ventilation” (PAV) kombiniert mit “automatic tube compensation” (ATC) stellt ein viel versprechendes Konzept zur Unterstützung einer insuffizienten Spontanatmung dar.Im Gegensatz zur konventionellen druckunterstützten Beatmung (“pressure support ventilation”,PSV) liefert PAV+ATC eine dynamische Druckunterstützung proportional zur Inspirationsbemühung des Patienten und sollte damit den Patienten nicht nur selektiv von der durch eine pathologische Resistance und Elastance des respiratorischen Systems erhöhten Atemarbeit entlasten, sondern auch von der zusätzlichen Arbeit durch den Widerstand des endotrachealen Tubus.Damit erhält der Patient die Möglichkeit durch Modulation des Atemzugvolumens seine Ventilation einem wechselnden Bedarf anzupassen. Dies kann eine bessere Synchronisation von Patient und Beatmungsgerät bedeuten und sollte – verglichen mit PSV – in einem erhöhten Beatmungskomfort resultieren. Da die Unterstützung während PAV als eine Funktion der atemmechanischen Größen des respiratorischen Systems eingestellt wird, deren Bestimmung unter assistierter Spontanatmung bisher aber nicht routinemäßig möglich ist, kann PAV für den Einsatz in der klinischen Routine zurzeit nicht uneingeschränkt empfohlen werden.SummaryThe combination of proportional assist ventilation (PAV) and automatic tube compensation (ATC) is a promising concept for partial ventilatory support. In contrast to conventional pressure support ventilation (PSV), PAV+ATC provides dynamic pressure support depending on the patients initial inspiratory effort.PAV+ATC should selectively unload the respiratory muscles from the additional workload imposed by increased respiratory system resistance and elastance as well as by endotracheal tube resistance.Patients have the ability to modify the tidal volume in response to changes in ventilatory demand, thereby improving patient-ventilator interaction and breathing comfort when compared with PSV.However, since routine measurements of respiratory mechanics during augmented spontaneous breathing are currently unavailable but would be necessary for setting the support level as a function of respiratory system mechanics during PAV, this mode cannot yet be generally recommended for routine clinical use.

Big fish, little fish

Many people assume that it’s better to attend the most selective college possible, even if your high school grades, test scores, and other measures place you towards the lower end of the college’s student body. The rationale behind this “small fish in a big pond” line of thinking is that students will always benefit from being surrounded by smarter peers, as well as enjoy the perceived prestige of the more selective school.

Pumpless extracorporeal CO2 removal restores normocapnia and is associated with less regional perfusion in experimental acute lung injury

Lung protective ventilation may lead to hypoventilation with subsequent hypercapnic acidosis (HA). If HA cannot be tolerated or occurs despite increasing respiratory rate or buffering, extracorporeal CO2‐removal using a percutaneous extracorporeal lung assist (pECLA) is an option. We hypothesised that compensation of HA using pECLA impairs regional perfusion. To test this hypothesis we determined organ blood flows in a lung‐injury model with combined hypercapnic and metabolic acidosis.