Stress response during weaning after cardiac surgery

Critical illness-related corticosteroid insufficiency during difficult weaning from mechanical ventilation

Background

Critical illness-related corticosteroid insufficiency (CIRCI) is common during critical illness and is usually associated with poor outcomes, as prolonged duration of mechanical ventilation (MV) and higher mortality. CIRCI may alter cardiac and vascular functions. Weaning-induced pulmonary oedema (WiPO) is a major mechanism of weaning failure. The aim of this study was to evaluate the role of CIRCI in patients with difficult ventilator weaning and its possible relation with WiPO.

Methods

This is a prospective study conducted in the intensive care of a university hospital in France. Patients under MV for more than 24 h, meeting weaning criteria and having failed the first spontaneous breathing trial (SBT) underwent a corticotropin stimulation test, with assessment of total blood cortisol levels immediately before (T₀) 0.25 mg iv of tetracosactrin and 30 and 60 min afterward. Δ_max was defined as the difference between the maximal value after the test and T₀. CIRCI was defined as T₀ < 10 μg/dL (276 nmol/L) and/or Δ_max < 9 μg/dL (248 nmol/L) and inadequate adrenal reserve as Δ_max < 9 μg/dL. Biomarkers (natriuretic peptide and protidemia) sampling and echocardiograms were performed during the second SBT and were used to diagnose WiPO, which was defined according to two definitions (one liberal and one conservative) derived from recent publications on the topic. Successful extubation was defined as patient alive without reintubation 7 days after extubation. A competing risk analysis was used to assess extubation failure and mortality.

Results

Seventy-six consecutive patients (63 ± 14 years; 49 men) with difficult weaning were enrolled. CIRCI and inadequate adrenal reserve occurred in 25 (33%) and 17 (22%) patients, respectively. The probability of successful extubation was significantly decreased in patients with CIRCI or inadequate adrenal reserve, as compared to their counterparts, and this association persisted after adjustment on severity (SOFA score at first SBT). WiPO occurred in 44 (58%) and 8 (11%) patients, according to the liberal and conservative definition, respectively. WiPO was not associated with CIRCI nor with inadequate adrenal reserve.

Conclusion

CIRCI was common during difficult weaning and was associated with its prolongation. We did not find a significant association between CIRCI and WiPO.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-021-00852-2.

Pulmonary Complications After Cardiac Surgery

Over the past two decades there has been a steady evolution in the practice of adult cardiac surgery with the introduction of “off-pump” surgery. However, respiratory complications remain a leading cause of postcardiac surgical morbidity and can prolong hospital stays and increase costs. The high incidence of pulmonary complications is in part due to the disruption of normal ventilatory function that is inherent to surgery in the thoracic region. Furthermore, patients undergoing such surgery often have underlying illnesses such as intrinsic lung disease (e.g., chronic obstructive pulmonary disease) and pulmonary dysfunction secondary to cardiac disease (e.g., congestive heart failure) that increase their susceptibility to postoperative respiratory problems. Given that many patients undergoing cardiac surgery are thus susceptiple to pulmonary complications, it is remarkable that more patients do not suffer from them during and after cardiac surgery. This is to a large degree because of advances in anesthetic, surgical and critical care that, for example, have reduced the physiological insults of surgery (e.g., better myocardial preservation techniques) and streamlined care in the immediate postoperative period (e.g., early extubation). Moreover, the development of minimally invasive surgery and nonbypass techniques are further evidence of the attempts at reducing the homeostatic disruptions of cardiac surgery. This review examines the available information on the incidences, consequences, and treatments of postcardiac surgery respiratory complications.

Effects of pressure-controlled and volume-controlled ventilation on respiratory mechanics and systemic stress response during laparoscopic cholecystectomy

Pressure-controlled ventilation (PCV) is less frequently employed in general anesthesia. With its high and decelerating inspiratory flow, PCV has faster tidal volume delivery and different gas distribution. The same tidal volume setting, delivered by PCV versus volume-controlled ventilation (VCV), will result in a lower peak airway pressure and reduced risk of barotrauma. We hypothesized that PCV instead of VCV during laparoscopic surgery could achieve lower airway pressures and reduce the systemic stress response. Forty ASA I-II patients were randomly selected to receive either the PCV (Group PC, n = 20) or VCV (Group VC, n = 20) during laparoscopic cholecystectomy. Blood sampling was made for baseline arterial blood gases (ABG), cortisol, insulin, and glucose levels. General anesthesia with sevoflurane and fentanyl was employed to all patients. After anesthesia induction and endotracheal intubation, patients in Group PC were given pressure support to form 8 mL/kg tidal volume and patients in Group VC was maintained at 8 mL/kg tidal volume calculated using predicted body weight. All patients were maintained with 5 cmH₂O positive-end expiratory pressure (PEEP). Respiratory parameters were recorded before and 30 min after pneumoperitonium. Assessment of ABG and sampling for cortisol, insulin and glucose levels were repeated 30 min after pneumoperitonium and 60 min after extubation. The P-peak levels observed before (18.9 ± 3.8 versus 15 ± 2.2 cmH₂O) and during (23.3 ± 3.8 versus 20.1 ± 2.9 cmH₂O) pneumoperitoneum in Group VC were significantly higher. Postoperative partial arterial oxygen pressure (PaO₂) values are higher (98 ± 12 versus 86 ± 11 mmHg) in Group PC. Arterial carbon dioxide pressure (PaCO₂) values (41.8 ± 5.4 versus 36.7 ± 3.5 mmHg) during pneumoperitonium and post-operative mean cortisol and insulin levels were higher in Group VC. When compared to VCV mode, PCV mode may improve compliance during pneumoperitoneum, improve oxygenation and reduce stress response postoperatively and may be more appropriate in patients having laparoscopic surgery.

Genetic variation of TLR4 influences immunoendocrine stress response: an observational study in cardiac surgical patients

Introduction

Systemic inflammation (for example, following surgery) involves Toll-like receptor (TLR) signaling and leads to an endocrine stress response. This study aims to investigate a possible influence of TLR2 and TLR4 single nucleotide polymorphisms (SNPs) on perioperative adrenocorticotropic hormone (ACTH) and cortisol regulation in serum of cardiac surgical patients. To investigate the link to systemic inflammation in this context, we additionally measured 10 different cytokines in the serum.

Methods

A total of 338 patients admitted for elective cardiac surgery were included in this prospective observational clinical cohort study. Genomic DNA of patients was screened for TLR2 and TLR4 SNPs. Serum concentrations of ACTH, cortisol, interferon (IFN)-γ, interleukin (IL)-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, tumor necrosis factor (TNF)-α and granulocyte macrophage-colony stimulating factor (GM-CSF) were determined before surgery, immediately post surgery and on the first postoperative day.

Results

Thirteen patients were identified as TLR2 SNP carriers, 51 as TLR4 SNP carriers and 274 patients as non-carriers. Basal levels of ACTH, cortisol and cytokines did not differ among groups. In all three groups a significant, transient perioperative rise of cortisol could be observed. However, only in the non-carrier group this was accompanied by a significant ACTH rise. TLR4 SNP carriers had significant lower ACTH levels compared to non-carriers (mean (95% confidence intervals)) non-carriers: 201.9 (187.7 to 216.1) pg/ml; TLR4 SNP carriers: 149.9 (118.4 to 181.5) pg/ml; TLR2 SNP carriers: 176.4 ((110.5 to 242.3) pg/ml). Compared to non-carriers, TLR4 SNP carriers showed significant lower serum IL-8, IL-10 and GM-CSF peaks (mean (95% confidence intervals)): IL-8: non-carriers: 42.6 (36.7 to 48.5) pg/ml, TLR4 SNP carriers: 23.7 (10.7 to 36.8) pg/ml; IL-10: non-carriers: 83.8 (70.3 to 97.4) pg/ml, TLR4 SNP carriers: 54.2 (24.1 to 84.2) pg/ml; GM-CSF: non-carriers: 33.0 (27.8 to 38.3) pg/ml, TLR4 SNP carriers: 20.2 (8.6 to 31.8) pg/ml). No significant changes over time or between the groups were found for the other cytokines.

Conclusions

Regulation of the immunoendocrine stress response during systemic inflammation is influenced by the presence of a TLR4 SNP. Cardiac surgical patients carrying this genotype showed decreased serum concentrations of ACTH, IL-8, IL-10 and GM-CSF. This finding might have impact on interpreting previous and designing future trials on diagnosing and modulating immunoendocrine dysregulation (for example, adrenal insufficiency) during systemic inflammation and sepsis.

Cardiac surgery patients present considerable variation in pre-operative hemodynamic variables

BACKGROUND

It is essential to control hemodynamics in cardiac surgery. Patients are often monitored extensively in order to optimize hemodynamic performance. However, pre-operative values are normally unknown. Furthermore, hemodynamic goals may seem arbitrary and the lack of an evidence-based consensus may lead to both under- and over-treatment. The aim of this study was to evaluate the variables most commonly used for hemodynamic guidance in the post-operative period.

METHODS

Ten patients scheduled for elective cardiac surgery were followed with invasive hemodynamic monitoring the night before surgery. All data were recorded automatically and electronically.

RESULTS

We found considerable inter-patient differences and intra-patient variation. The greatest intra-patient variation was found in the cardiac index (CI), ranging from 1.9 to 5.3 l/min/m(2). Four patients had periodic CI <2.4 l/min/m(2). Eight patients showed SpO2 values < or =92, four of them in more than 15% of the observations. Six patients had an SvO2 <70% in more than 40% of the observations and two an SvO2 < 64% in more than 20% of the observations.

CONCLUSIONS

This study is unique because hemodynamic reference data in cardiac surgery patients have not been published previously. The intra-patient variations were unexpectedly high in most hemodynamic variables and demonstrate the difficulties of using hemodynamic parameters as a guidance for treatment and indicate that goal-oriented therapy using currently accepted values may result in over-treatment in some patients.

The effects of different weaning modes on the endocrine stress response

Introduction

The aim of the present study was to investigate the effects of the stress response on plasma insulin, cortisol, glucose, and urinary vanilmandelic acid during weaning and after extubation, using pressure support (PS), continuous positive airway pressure (CPAP) and T-piece modes.

Methods

Sixty patients were randomly divided into three groups (n = 20). The PS group received FiO₂ ≤ 0.4, PS ≤ 10 cmH₂O, and positive end expiratory pressure ≤ 5 cmH₂O for 2 hours. The CPAP group was given FiO₂ ≤ 0.4 and CPAP 5 ≤ cmH₂O for 2 hours. The T-piece group (group T) received 4 l/min oxygen via a T-piece for 2 hours. After 1 hour and 2 hours in their respective weaning modes, blood and urine samples were taken for insulin, cortisol, glucose and vanilmandelic acid measurements. Forty-eight hours after extubation, blood and urine samples were again taken.

Results

Plasma insulin was greater in group T than in the PS and CPAP groups (P < 0.01 and P < 0.01). The plasma cortisol concentration was greater in group T than in group PS during weaning (P < 0.05) and after extubation (P < 0.05). Blood glucose concentrations were greater in group T than in the other groups (both P < 0.01) both during weaning and post extubation. Urine vanilmandelic acid was greater in group T than in the other groups during weaning and after extubation (both P < 0.001).

Conclusion

Weaning via the T-piece caused a greater stress response than the PS and CPAP modes.