Tacrolimus and the risk of solid cancers after liver transplant: a dose effect relationship

Although increased rates of solid organ cancers have been reported following liver transplantation (LT), the impact of quantitative exposure to calcineurin inhibitors (CNI) remains unclear. We have therefore probed the relationship between the development of solid organ cancers following LT and the level of CNI exposure. This prospective single-center study was conducted between 1995 and 2008 and is based on 247 tacrolimus-treated liver transplant recipients who survived at least 1 year following surgery. The incidence of cancer was recorded, and the mean blood concentration of tacrolimus (TC) was determined at 1 and 3 years following LT. The study results indicate that 43 (17.4%) patients developed de novo solid cancers. Mean TC during the first year after LT was significantly higher in patients who developed solid organ tumors (10.3 ± 2.1 vs. 7.9 ± 1.9 ng/mL, p < 0.0001). Independent risks factors in multivariate analysis were tobacco consumption before LT (OR = 5.42; 95% CI [1.93-15.2], p = 0.0014) and mean annual TC during the first year after LT (p < 0.0001; OR = 2.01; 95% CI [1.57-2.59], p < 0.0001). Similar effects were observed in 216 patients who received tacrolimus continuously for ≥3 years. It appears therefore that CNI should be used with caution after LT, and that new immunosuppressive therapies could deliver significant clinical benefits in this regard.

Difficult intubation in obese patients: incidence, risk factors, and complications in the operating theatre and in intensive care units

BACKGROUND

Intubation procedure in obese patients is a challenging issue both in the intensive care unit (ICU) and in the operating theatre (OT). The objectives of the study were (i) to compare the incidence of difficult intubation and (ii) its related complications in obese patients admitted to ICU and OT.

METHODS

We conducted a multicentre prospective observational cohort study in ICU and OT in obese (BMI≥30 kg m(-2)) patients. The primary endpoint was the incidence of difficult intubation. Secondary endpoints were the risk factors for difficult intubation, the use of difficult airway management techniques, and severe life-threatening complications related to intubation (death, cardiac arrest, severe hypoxaemia, severe cardiovascular collapse).

RESULTS

In cohorts of 1400 and 11 035 consecutive patients intubated in ICU and in the OT, 282 (20%) and 2103 (19%) were obese. In obese patients, the incidence of difficult intubation was twice more frequent in ICU than in the OT (16.3% vs 8.2%, P<0.01). In both cohorts, risk factors for difficult intubation were Mallampati score III/IV, obstructive sleep apnoea syndrome, and reduced mobility of cervical spine, while limited mouth opening, severe hypoxaemia, and coma appeared only in ICU. Specific difficult airway management techniques were used in 66 (36%) cases of difficult intubation in obese patients in the OT and in 10 (22%) cases in ICU (P=0.04). Severe life-threatening complications were significantly more frequent in ICU than in the OT (41.1% vs 1.9%, relative risk 21.6, 95% confidence interval 15.4-30.3, P<0.01).

CONCLUSIONS

In obese patients, the incidence of difficult intubation was twice more frequent in ICU than in the OT and severe life-threatening complications related to intubation occurred 20-fold more often in ICU.

CLINICAL TRIAL REGISTRATION

Current controlled trials. Identifier: NCT01532063.

How to preoxygenate in operative room: healthy subjects and situations "at risk"

Intubation is one of the most common procedures performed in operative rooms. It can be associated with life-threatening complications when difficult airway access occurs, in patients who cannot tolerate even a slight hypoxemia or when performed in patients at risk of oxygen desaturation during intubation, as obese, critically-ill and pregnant patients. To improve intubation safety, preoxygenation is a major technique, extending the duration of safe apnoea, defined as the time until a patient reaches an arterial saturation level of 88% to 90%, to allow for placement of a definitive airway. Preoxygenation consists in increasing the lung stores of oxygen, located in the functional residual capacity, and helps preventing hypoxia that may occur during intubation attempts. Obese, critically-ill and pregnant patients are especially at risk of reduced effectiveness of preoxygenation because of pathophysiological modifications (reduced functional residual capacity (FRC), increased risk of atelectasis, shunt). Three minutes tidal volume breathing or 3-8 vital capacities are recommended in general population, mostly allowing achieving a 90% end-tidal oxygen level. Recent studies have indicated that in order to maximize the value of preoxygenation (i.e, oxygenation stores) obese and critically-ill patients can benefit from the combination of breathing 100% oxygen and non-invasive positive pressure ventilation (NIV) with end-expiratory positive pressure (PEEP) in the proclive position (Trendelenburg reverse). Recruitment manoeuvres may be of interest immediately after intubation to limit the risk of lung derecruitment. Further studies are needed in the field of preoxygenation in pregnant women.

Mechanical ventilation in abdominal surgery

One of the key challenges in perioperative care is to reduce postoperative morbidity and mortality. Patients who develop postoperative morbidity but survive to leave hospital have often reduced functional independence and long-term survival. Mechanical ventilation provides a specific example that may help us to shift thinking from treatment to prevention of postoperative complications. Mechanical ventilation in patients undergoing surgery has long been considered only as a modality to ensure gas exchange while allowing maintenance of anesthesia with delivery of inhaled anesthetics. Evidence is accumulating, however, suggesting an association between intraoperative mechanical ventilation strategy and postoperative pulmonary function and clinical outcome in patients undergoing abdominal surgery. Non-protective ventilator settings, especially high tidal volume (VT) (>10-12mL/kg) and the use of very low level of positive end-expiratory pressure (PEEP) (PEEP<5cmH2O) or no PEEP, may cause alveolar overdistension and repetitive tidal recruitment leading to ventilator-associated lung injury in patients with healthy lungs. Stimulated by previous findings in patients with acute respiratory distress syndrome, the use of lower tidal volume ventilation is becoming increasingly more common in the operating room. However, lowering tidal volume, though important, is only part of the overall multifaceted approach of lung protective mechanical ventilation. In this review, we aimed at providing the most recent and relevant clinical evidence regarding the use of mechanical ventilation in patients undergoing abdominal surgery.

How to choose an anesthesia ventilator?

During the past few years, many manufacturers have developed a new generation anesthesia ventilators or anesthesia workstations with innovative technology and introduced so-called new ventilatory modes in the operating room. The aim of this article is to briefly explain how an anesthesia ventilator works, to describe the main differences between the technologies used, to describe the main criteria for evaluating technical and pneumatic performances and to list key elements not to be forgotten during the process of acquiring an anesthesia ventilator.

Protective lung ventilation in operating room: a systematic review

Postoperative pulmonary and extrapulmonary complications adversely affect clinical outcomes and healthcare utilization, so that prevention has become a measure of the quality of perioperative care. Mechanical ventilation is an essential support therapy to maintain adequate gas exchange during general anesthesia for surgery. Mechanical ventilation using high tidal volume (VT) (between 10 and 15 mL/kg) has been historically encouraged to prevent hypoxemia and atelectasis formation in anesthetized patients undergoing abdominal and thoracic surgery. However, there is accumulating evidence from both experimental and clinical studies that mechanical ventilation, especially the use of high VT and plateau pressure, may potentially aggravate or even initiate lung injury. Ventilator-associated lung injury can result from cyclic alveolar overdistension of non-dependent lung tissue, and repetitive opening and closing of dependent lung tissue resulting in ultrastructural damage at the junction of closed and open alveoli. Lung-protective ventilation, which refers to the use of lower VT and limited plateau pressure to minimize overdistension, and positive end-expiratory pressure to prevent alveolar collapse at end-expiration, was shown to improve outcome in critically ill patients with acute respiratory distress syndrome (ARDS). It has been recently suggested that this approach might also be beneficial in a broader population, especially in critically ill patients without ARDS at the onset of mechanical ventilation. There is, however, little evidence regarding a potential beneficial effect of lung protective ventilation during surgery, especially in patients with healthy lungs. Although surgical patients are frequently exposed to much shorter periods of mechanical ventilation, this is an important gap in knowledge given the number of patients receiving mechanical ventilation in the operating room. This review developed the benefits of lung protective ventilation during surgery and general anesthesia and offers some recommendations for mechanical ventilation in the surgical context.