Histamine release during adult cardiopulmonary bypass

Paediatric perioperative hypersensitivity: the performance of the current consensus formula and the effect of uneventful anaesthesia on serum tryptase

Background

Paired sampling of acute (aST) and basal (bST) serum tryptase has been recommended when investigating patients with a suspected perioperative hypersensitivity (POH) reaction. In the current consensus formula, an aST value exceeding (1.2×bST+2) confirms mast cell activation. The current consensus formula has been validated in adults but not in children.

Methods

We prospectively included 96 children who underwent uneventful anaesthesia and sampled serum tryptase at baseline and 60-90 min after induction. Tryptase changes were then compared with those in 94 children with suspected POH who were retrospectively included from four reference centres in Belgium, France, and Denmark.

Results

We observed a median decrease in serum tryptase during uneventful anaesthesia of 0.41 μg L-1 (-15.9%; P<0.001). The current consensus formula identified mast cell activation in 31.9% of paediatric POH patients. After generating receiver operating characteristic curves through 100 repeated five-fold cross-validation, aST>bST+0.71 was identified as the optimal cut-off point to identify mast cell activation. This new paediatric formula has higher sensitivity than the current consensus formula (53.2% vs 31.9%, P<0.001) with a specificity of 96.9%. Analysis in the subpopulation where a culprit was identified and in grade 3-4 reactions similarly yielded higher sensitivity for the new paediatric formula when compared with the current consensus formula (85.3% vs 61.8%; P=0.008 and 78.0% vs 48.8%; P<0.001, respectively). Internally cross-validated sensitivity and specificity were 53.3% and 93.3%, respectively.

Conclusions

This is the first study suggesting the need for an adjusted formula in children to identify perioperative mast cell activation as tryptase is significantly lowered during uneventful anaesthesia. We propose a new formula (aST>bST+0.71) which performs significantly better than the current consensus formula in our multicentric paediatric population.

The Pathophysiology of Cardiac Surgery-Associated Acute Kidney Injury (CSA-AKI)

Cardiac surgery associated acute kidney injury (CSA-AKI) is a significant clinical problem. Its pathogenesis is complex and multifactorial. It likely involved at least six major injury pathways: exogenous and endogenous toxins, metabolic factors, ischemia and reperfusion, neurohormonal activation, inflammation and oxidative stress. These mechanisms of injury are likely to be active at different times with different intensity and probably act synergistically. Because of such complexity and the small number of randomised controlled investigations in this field only limited recommendations can be made. Nonetheless, it appears important to avoid nephrotoxic drugs and desirable to avoid hyperglycemia in the peri-operative period. The duration of cardiopulmonary bypass should be limited whenever possible. Off-pump surgery, when indicated, may decrease the risk of AKI. Invasive hemodynamic monitoring focussed on attention to maintaining euvolemia, an adequate cardiac output and an adequate arterial blood pressure is desirable. Echocardiography may be useful in minimizing atheroembolic complications. The administration of N-acetylcysteine to protect the kidney from oxidative stress is not recommended. There is marked lack of randomised controlled trials in this field.

Sevoflurane Relieves Lung Function Deterioration After Cardiopulmonary Bypass

OBJECTIVE

To investigate sevoflurane's potential to alleviate the detrimental pulmonary changes after cardiopulmonary bypass (CPB).

DESIGN

Prospective, randomized clinical investigation.

SETTING

University hospital.

PARTICIPANTS

One hundred ninety patients undergoing elective cardiac surgery.

INTERVENTIONS

Ninety-nine patients under intravenous anesthesia were administered 1 minimal alveolar concentration of sevoflurane for 5 minutes after being weaned from CPB (group SEV); intravenous anesthesia was maintained in the other 91 patients (group CTRL).

MEASUREMENTS AND MAIN RESULTS

Measurements were performed with open chest: before CPB, after CPB, and after intervention. The lungs' mechanical impedance and capnogram traces were recorded, arterial and central venous blood samples were analyzed, and lung compliance was documented. Airway resistance, tissue damping, and elastance were obtained from the impedance spectra. The capnogram phase III slope was determined using linear regression. The partial pressure of oxygen in the arterial blood/fraction of inspired oxygen ratio and shunt fraction were calculated from blood gas parameters. After CPB, sevoflurane induced bronchodilation, reflected in marked drops in airway resistance and smaller improvements in lung tissue viscoelasticity indicated by decreases in tissue damping and elastance. These changes were reflected in a decreased capnogram phase III slope and shunt fraction and increased partial pressure of oxygen in the arterial blood/fraction of inspired oxygen ratio and lung compliance. The more severe deteriorations that occurred after CPB, the greater improvements by sevoflurane were observed.

CONCLUSIONS

Sevoflurane can alleviate CPB-induced bronchoconstriction, compromised lung tissue mechanics, and enhanced intrapulmonary shunt. This benefit has particular importance in patients with severe CPB-induced lung function deterioration.

Mast cell activation and arterial hypotension during proximal aortic repair requiring hypothermic circulatory arrest

OBJECTIVE

Aortic surgeries requiring hypothermic circulatory arrest evoke systemic inflammatory responses that often manifest as vasoplegia and hypotension. Because mast cells can rapidly release vasoactive and proinflammatory effectors, we investigated their role in intraoperative hypotension.

METHODS

We studied 31 patients undergoing proximal aortic repair with hypothermic circulatory arrest between June 2013 and April 2015 at Duke University Medical Center. Plasma samples were obtained at different intraoperative time points to quantify chymase, interleukin-6, interleukin-8, tumor necrosis factor alpha, and white blood cell CD11b expression. Hypotension was defined as the area (minutes × millimeters mercury) below a mean arterial pressure of 55 mm Hg. Biomarker responses and their association with intraoperative hypotension were analyzed by 2-sample t test and Wilcoxon rank sum test. Multivariable logistic regression analysis was used to examine the association between clinical variables and elevated chymase levels.

RESULTS

Mast cell-specific chymase increased from a median 0.97 pg/mg (interquartile range [IQR], 0.01-1.84 pg/mg) plasma protein at baseline to 5.74 pg/mg (IQR, 2.91-9.48 pg/mg) plasma protein after instituting cardiopulmonary bypass, 6.16 pg/mg (IQR, 3.60-9.41 pg/mg) plasma protein after completing circulatory arrest, and 7.64 pg/mg (IQR, 4.63-12.71 pg/mg) plasma protein after weaning from cardiopulmonary bypass (each P value < .0001 vs baseline). Chymase was the only biomarker associated with hypotension during (P = .0255) and after (P = .0221) cardiopulmonary bypass. Increased temperatures at circulatory arrest and low presurgical hemoglobin levels were independent predictors of increased chymase responses.

CONCLUSIONS

Mast cell activation occurs in cardiac surgery requiring cardiopulmonary bypass and hypothermic circulatory arrest and is associated with intraoperative hypotension.

Systemic mastocytosis presenting as intraoperative anaphylaxis with atypical features: a report of two cases

Two cases of perioperative cardiovascular collapse are presented that were associated with markedly elevated mast cell tryptase levels shortly after the event, leading to the assumption that an immunoglobin E-mediated, drug-induced anaphylaxis had occurred. However, the clinical picture in both cases was atypical and subsequent skin testing failed to identify a triggering drug. Further blood tests, some weeks later, revealed persistently elevated baseline levels of mast cell tryptase. In both cases bone marrow biopsy and genetic testing confirmed the diagnosis of mastocytosis. We present evidence and speculate that mast cell degranulation was triggered by tourniquet release in the first case and by exposure to peanuts in the second. An atypical presentation of anaphylaxis should alert the anaesthetist to the possibility of previously undiagnosed mastocytosis.