Martin Beiderlinden

Protective versus Conventional Ventilation for Surgery: A Systematic Review and Individual Patient Data Meta-analysis.

Background:Recent studies show that intraoperative mechanical ventilation using low tidal volumes (VT) can prevent postoperative pulmonary complications (PPCs). The aim of this individual patient data meta-analysis is to evaluate the individual associations between VT size and positive end–expiratory pressure (PEEP) level and occurrence of PPC. Methods:Randomized controlled trials comparing protective ventilation (low VT with or without high levels of PEEP) and conventional ventilation (high VT with low PEEP) in patients undergoing general surgery. The primary outcome was development of PPC. Predefined prognostic factors were tested using multivariate logistic regression. Results:Fifteen randomized controlled trials were included (2,127 patients). There were 97 cases of PPC in 1,118 patients (8.7%) assigned to protective ventilation and 148 cases in 1,009 patients (14.7%) assigned to conventional ventilation (adjusted relative risk, 0.64; 95% CI, 0.46 to 0.88; P < 0.01). There were 85 cases of PPC in 957 patients (8.9%) assigned to ventilation with low VT and high PEEP levels and 63 cases in 525 patients (12%) assigned to ventilation with low VT and low PEEP levels (adjusted relative risk, 0.93; 95% CI, 0.64 to 1.37; P = 0.72). A dose–response relationship was found between the appearance of PPC and VT size (R2 = 0.39) but not between the appearance of PPC and PEEP level (R2 = 0.08). Conclusions:These data support the beneficial effects of ventilation with use of low VT in patients undergoing surgery. Further trials are necessary to define the role of intraoperative higher PEEP to prevent PPC during nonopen abdominal surgery.

Argatroban Anticoagulation in Critically Ill Patients

Background: Despite long-term use of argatroban in clinical practice, no dosing recommendations exist for critically ill patients with multiple organ dysfunction (MODS) and suspected or proven heparin-induced thrombocytopenia (HIT). Objective: To determine the suitability of argatroban use in critically ill patients with MODS and HIT. Methods: We conducted prospective observation of 24 consecutive patients with suspected HIT who were being anticoagulated with argatroban (target activated partial thromboplastin time [aPTT] 1.5–2 times normal or 50–60 sec) using 2 μg/kg/min in the first 5 patients and 0.2 μg/kg/min in the subsequent 19 patients. Results: Infusion of argatroban 2 μg/kg/min over 4 hours caused bleeding complications in 3 patients as aPTT increased from 51 ± 18 to 86 ± 34 seconds (p = 0.02), prothrombin time (PT) decreased from 76 ± 27% to 33 ± 12% of normal reference values, and international normalized ratio (INR) increased from 1.4 ± 0.4 to 2.5 ± 0.9 (p = 0.007). Infusion of argatroban 0.2 μg/kg/min over 4 hours provided sufficient anticoagulation without bleeding complications. The aPTT in this population increased from 44 ± 9 to 59 ± 13 seconds (p < 0.001), and PT and INR remained unchanged (76 ± 22% and 69 ± 23% of normal reference values, 1.3 ± 0.3 and after 1.3 ± 0.3, respectively [p = 0.4]). Coagulation variables (aPTT, PT, INR) were significantly different between both dosing regimens after 4 hours of infusion (p = 0.042 and p = 0.003, respectively). The maintenance dose for target aPTT averaged 0.22 ± 0.15 μg/kg/min in both groups. Conclusions: In critically ill patients with MODS, argatroban 2 μg/kg/min, as recommended by the manufacturer, resulted in extensive anticoagulation. A tenfold lower starting dose is sufficient and safe for effective anticoagulation in this specific patient population.

Ventilation with low tidal volumes during upper abdominal surgery does not improve postoperative lung function

BACKGROUND Prolonged postoperative decrease in lung function is common after major upper abdominal surgery. Evidence suggests that ventilation with low tidal volumes may limit the damage during mechanical ventilation. We compared postoperative lung function of patients undergoing upper abdominal surgery, mechanically ventilated with high or low tidal volumes. METHODS This was a double-blind, prospective, randomized controlled clinical trial. One hundred and one patients (age ≥ 50 yr, ASA ≥ II, duration of surgery ≥ 3 h) were ventilated with: (i) high [12 ml kg(-1) predicted body weight (PBW)] or (ii) low (6 ml kg(-1) PBW) tidal volumes intraoperatively. The positive end-expiratory pressure was 5 cm H(2)O in both groups and breathing frequency adjusted to normocapnia. Time-weighted averages (TWAs) of forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV(1)) until 120 h after operation were compared (P<0.025 considered statistically significant). Secondary outcomes were oxygenation, respiratory and non-respiratory complications, length of stay and mortality. RESULTS The mean (sd) values of TWAs of FVC and FEV(1) were similar in both groups: FVC: 6 ml group 1.8 (0.7) litre vs 12 ml group 1.6 (0.5) litre (P=0.12); FEV(1): 6 ml group 1.4 (0.5) litre vs 12 ml group 1.2 (0.4) litre (P=0.15). FVC and FEV(1) at any single time point and secondary outcomes did not differ significantly between groups. CONCLUSIONS Prolonged impaired lung function after major abdominal surgery is not ameliorated by low tidal volume ventilation.

Association between driving pressure and development of postoperative pulmonary complications in patients undergoing mechanical ventilation for general anaesthesia: a meta-analysis of individual patient data.

BACKGROUND Protective mechanical ventilation strategies using low tidal volume or high levels of positive end-expiratory pressure (PEEP) improve outcomes for patients who have had surgery. The role of the driving pressure, which is the difference between the plateau pressure and the level of positive end-expiratory pressure is not known. We investigated the association of tidal volume, the level of PEEP, and driving pressure during intraoperative ventilation with the development of postoperative pulmonary complications. METHODS We did a meta-analysis of individual patient data from randomised controlled trials of protective ventilation during general anesthaesia for surgery published up to July 30, 2015. The main outcome was development of postoperative pulmonary complications (postoperative lung injury, pulmonary infection, or barotrauma). FINDINGS We included data from 17 randomised controlled trials, including 2250 patients. Multivariate analysis suggested that driving pressure was associated with the development of postoperative pulmonary complications (odds ratio [OR] for one unit increase of driving pressure 1·16, 95% CI 1·13-1·19; p<0·0001), whereas we detected no association for tidal volume (1·05, 0·98-1·13; p=0·179). PEEP did not have a large enough effect in univariate analysis to warrant inclusion in the multivariate analysis. In a mediator analysis, driving pressure was the only significant mediator of the effects of protective ventilation on development of pulmonary complications (p=0·027). In two studies that compared low with high PEEP during low tidal volume ventilation, an increase in the level of PEEP that resulted in an increase in driving pressure was associated with more postoperative pulmonary complications (OR 3·11, 95% CI 1·39-6·96; p=0·006). INTERPRETATION In patients having surgery, intraoperative high driving pressure and changes in the level of PEEP that result in an increase of driving pressure are associated with more postoperative pulmonary complications. However, a randomised controlled trial comparing ventilation based on driving pressure with usual care is needed to confirm these findings. FUNDING None.

Postoperative upper airway obstruction after recovery of the train of four ratio of the adductor pollicis muscle from neuromuscular blockade.

Anesthetics, and even minimal residual neuromuscular blockade, may lead to upper airway obstruction (UAO). In this study we assessed by spirometry in patients with a train-of-four (TOF) ratio >0.9 the incidence of UAO (i.e., the ratio of maximal expiratory flow and maximal inspiratory flow at 50% of vital capacity [MEF50/MIF50] >1) and determined if UAO is induced by neuromuscular blockade (defined by a forced vital capacity [FVC] fade, i.e., a decrease in values of FVC from the first to the second consecutive spirometric maneuver of ≥10%). Patients received propofol and opioids for anesthesia. Spirometry was performed by a series of 3 repetitive spirometric maneuvers: the first before induction (under midazolam premedication), the second after tracheal extubation (TOF ratio: 0.9 or more), and the third 30 min later. Immediately after tracheal extubation and 30 min later, 48 and 6 of 130 patients, respectively, were not able to perform spirometry appropriately because of sedation. The incidence of UAO increased significantly (P < 0.01) from 82 of 130 patients (63%) at preinduction baseline to 70 of 82 patients (85%) after extubation, and subsequently decreased within 30 min to values observed at baseline (80 of 124 patients, 65%). The mean maximal expiratory flow and maximal inspiratory flow at 50% of vital capacity ratio after tracheal extubation was significantly increased from baseline (by 20%; 1.39 ± 1.01 versus 1.73 ± 1.02; P < 0.01), and subsequently decreased significantly to values observed at baseline (1.49 ± 0.93). A statistically significant FVC fade was not present, and a FVC fade of ≥10% was observed in only 2 patients after extubation. Thus, recovery of the TOF ratio to 0.9 predicts with high probability an absence of neuromuscular blocking drug-induced UAO, but outliers, i.e., persistent effects of neuromuscular blockade on upper airway integrity despite recovery of the TOF ratio, may still occur.

Conservative treatment of tracheal injuries.

Tracheal injuries, independent of their origin, may be life-threatening. Surgical repair is regarded as the treatment of choice but has not been compared with other approaches. We hypothesized that defects bridgeable by an artificial airway may enable conservative treatment. We report on five patients with tracheal injuries, two in the trachea’s upper third resulting from trauma and intubation and three in its middle third after percutaneous dilational tracheostomy. Tracheal defects were bridged by endotracheal or tracheostomy tubes under bronchoscopic guidance and the cuff was inflated distal to the lesion. Air leakage stopped immediately and all tracheal defects healed without further interventions. No case of stenosis or mediastinitis was observed. These results suggest that treating tracheal injuries conservatively by placing an artificial airway under bronchoscopic guidance may be effective and offers a convenient starting position for secondary surgical repair in selected patients when conservative treatment fails.

Reply to comment on: "Safety of percutaneous dilational tracheostomy in patients ventilated with high positive end-expiratory pressure"

the beginning of ARDS and even after initial stabilization (PEEP of 17±4 vs. 8.7±5.5 mbar and a PaO2/FIO2 ratio of 130±42 vs. 141±55 mmHg). Furthermore, as suggested by an overall mortality of 61%, obviously not all ARDS patients improve within 72 h [1]. Thus to optimize mechanical ventilation and handling of these severely compromised patients PDT is performed after the attempt of initial stabilization. We also agree that blood gas measurements 1 h after PDT do not reflect the oxygenation during PDT, and that intra-arterial blood gas tension measurement would be likely to show this. Furthermore, we cannot contradict the speculation that oxygenation had to be impaired, and that PaCO2 increased under PDT in patients with high PEEP. However, in our hands [2, 3] it took a median of 7 min to perform PDT, and no serious side effects in these severely ill patients were observed. Moreover, PDT is performed using a FIO2 of 1.0, and no serious deterioration in arterial oxygen saturation was observed. However, Cakar et al. are mistaken in believing that our main concern was oxygenation during PDT. Rather, we were interested that sequelae of the procedure jeopardized gas exchange. Therefore we measured blood gas tensions 1 h and 24 h after the procedure. As we demonstrated, particularly in the most severely ill patients (see Fig. 2), PDT did not cause a deterioration in gas exchange but was associated with further improvement. Overall, 55 of 88 patients (59%) treated with high PEEP survived in contrast to 53 of 115 patients (46%) with low PEEP, which is an excellent result for patients with grave ARDS. Therefore while we do not argue that PDT can be dangerous in the hands of unexperienced physicians, it is time to rethink: PDT can be safe even in patients with severe ARDS ventilated with high PEEP. References

Nonoperative Management of Tracheobronchial Injuries in Severely Injured Patients

PurposeA rupture of the airway due to blunt chest trauma is rare, and treatment can prove challenging. Many surgeons suggest operative management for these kinds of injuries. Nonoperative therapy is reported only in exceptional cases. But there is still a lack of evidence from which to recommend surgical repair of these injuries as the first choice procedure.MethodsWe retrospectively analyzed the records of 92 multiple injured patients admitted to our trauma department between July 2002 and July 2003 for the incidence and management of tracheobronchial rupture (TBR).ResultsFive (5.4%) of 92 patients suffered from tracheobronchial injuries. The mean injury severity score was 38. There were three male and two female patients, with a mean age of 23 years. All patients had lesions <2 cm in size and were treated nonoperatively. One patient died from multiorgan failure, but the others recovered from TBR uneventfully. One patient developed acute pneumonia as a result of respirator therapy, but none of the patients had mediastinitis or tracheal stenosis within 3 months after injury.ConclusionWe believe that surgical treatment is not mandatory in patients with small to moderate ruptures, and such aggressive treatment may even have adverse effects, especially in patients with multiple injuries.

Risk factors associated with bleeding during and after percutaneous dilational tracheostomy

We evaluated the effect of pre‐operative coagulation status on the incidence of acute and chronic bleeding in 415 consecutive patients undergoing percutaneous dilational tracheostomy. The incidence of acute bleeding was independent of the coagulation variables tested. The risk of chronic bleeding was higher with an activated partial thromboplastin time above 50 s (OR 3.7 (95% CI 1.1–12.7); NNT 18.4 (95% CI 9.0–∞); p = 0.04), a platelet count below 50 × 109 l−1 (OR 5.0 (95% CI 1.4–17.2); NNT 12.3 (95% CI 6.2–833.3); p = 0.01) and in the presence of two or more abnormal coagulation variables (OR 9.5 (95% CI 2.3–34.7); NNT 6.2 (95% CI 3.2–68); p = 0.002). Low‐dose heparin treatment did not significantly increase the risk of chronic bleeding.

Does perioperative administration of rofecoxib improve analgesia after spine, breast and orthopaedic surgery?

Background and objective: Data on the effectiveness of cyclooxygenase 2 inhibitors in postoperative pain therapy vary widely. We tested in a prospective, placebo‐controlled, randomized, double‐blind trial the hypotheses that perioperative (i.e. preoperative and postoperative) administration of the cyclooxygenase 2 inhibitor rofecoxib decreases pain scores and morphine consumption after spine, breast and orthopaedic surgery. Methods: Five hundred and forty patients scheduled for spine, breast or orthopaedic surgery were randomly assigned to receive in combination with postoperative morphine via patient controlled analgesia pump for 4 days either rofecoxib 50 mg administered perioperatively, rofecoxib 50 mg administered only postoperatively, or placebo. Primary outcome criteria were pain score at rest (numeric rating scale 0–4) and morphine consumption. Results: Perioperative rofecoxib significantly decreased pain score 0 (0–1) vs. 1 (0–2) (median (interquartile range)), and morphine consumption 18 (6–33) vs. 22.5 (12–38) compared with placebo. In contrast, rofecoxib when administered only postoperatively did not significantly improve analgesic effects or side‐effects at time of assessment of the main criteria (24 h after skin closure), but during the follow‐up period at 48 h and 72 h after skin closure pain scores and morphine consumption were improved compared to placebo. The analgesic effects of rofecoxib were independent from the type of surgery. Conclusions: Perioperative administration of the cyclooxygenase 2 inhibitor rofecoxib decreases pain scores and morphine consumption after orthopaedic, breast and spine surgery. However, the benefit of preoperative administration of the cyclooxygenase 2 inhibitor seems to be only moderate, suggesting that early postoperative administration may be a useful alternative approach. There is no evidence that the type of surgery influences analgesic effects of cyclooxygenase 2 inhibitors.