Neuromuscular-blocking drugs. Use and misuse in the intensive care unit

Ensemble-Based Virtual Screening Led to the Discovery of Novel Lead Molecules as Potential NMBAs

Neuromuscular blocking agents (NMBAs) are routinely used during anesthesia to relax skeletal muscle. Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels; NMBAs can induce muscle paralysis by preventing the neurotransmitter acetylcholine (ACh) from binding to nAChRs situated on the postsynaptic membranes. Despite widespread efforts, it is still a great challenge to find new NMBAs since the introduction of cisatracurium in 1995. In this work, an effective ensemble-based virtual screening method, including molecular property filters, 3D pharmacophore model, and molecular docking, was applied to discover potential NMBAs from the ZINC15 database. The results showed that screened hit compounds had better docking scores than the reference compound d-tubocurarine. In order to further investigate the binding modes between the hit compounds and nAChRs at simulated physiological conditions, the molecular dynamics simulation was performed. Deep analysis of the simulation results revealed that ZINC257459695 can stably bind to nAChRs' active sites and interact with the key residue Asp165. The binding free energies were also calculated for the obtained hits using the MM/GBSA method. In silico ADMET calculations were performed to assess the pharmacokinetic properties of hit compounds in the human body. Overall, the identified ZINC257459695 may be a promising lead compound for developing new NMBAs as an adjunct to general anesthesia, necessitating further investigations.

Dexmedetomidine and paralytic exposure after damage control laparotomy: risk factors for delirium? Results from the EAST SLEEP-TIME multicenter trial

PURPOSE

To evaluate factors associated with ICU delirium in patients who underwent damage control laparotomy (DCL), with the hypothesis that benzodiazepines and paralytic infusions would be associated with increased delirium risk. We also sought to evaluate the differences in sedation practices between trauma (T) and non-trauma (NT) patients.

METHODS

We reviewed retrospective data from 15 centers in the EAST SLEEP-TIME registry admitted from January 1, 2017 to December 31, 2018. We included all adults undergoing DCL, regardless of diagnosis, who had completed daily Richmond Agitation Sedation Score (RASS) and Confusion Assessment Method-ICU (CAM-ICU). We excluded patients younger than 18 years, pregnant women, prisoners and patients who died before the first re-laparotomy. Data collected included age, number of re-laparotomies after DCL, duration of paralytic infusion, duration and type of sedative and opioid infusions as well as daily CAM-ICU and RASS scores to analyze risk factors associated with the proportion of delirium-free/coma-free ICU days during the first 30 days (DF/CF-ICU-30) using multivariate linear regression.

RESULTS

A 353 patient subset (73.2% trauma) from the overall 567-patient cohort had complete daily RASS and CAM-ICU data. NT patients were older (58.9 ± 16.0 years vs 40.5 ± 17.0 years [p < 0.001]). Mean DF/CF-ICU-30 days was 73.7 ± 96.4% for the NT and 51.3 ± 38.7% in the T patients (p = 0.030). More T patients were exposed to Midazolam, 41.3% vs 20.3% (p = 0.002). More T patients were exposed to Propofol, 91.0% vs 71.9% (p < 0.001) with longer infusion times in T compared to NT (71.2 ± 85.9 vs 48.9 ± 69.8 h [p = 0.017]). Paralytic infusions were also used more in T compared to NT, 34.8% vs 18.2% (p < 0.001). Using linear regression, dexmedetomidine infusion and paralytic infusions were associated with decreases in DF/CF-ICU-30, (- 2.78 (95%CI [- 5.54, - 0.024], p = 0.040) and (- 7.08 ([- 13.0, - 1.10], p = 0.020) respectively.

CONCLUSIONS

Although the relationship between paralytic use and delirium is well-established, the observation that dexmedetomidine exposure is independently associated with increased delirium and coma is novel and bears further study.

Outcomes of Delayed Sternal Closure in Pediatric Heart Surgery: Single-Center Experience

Background

Delayed sternal closure (DSC) after cardiac surgery is a therapeutic option in the treatment of the severely impaired heart in pediatric cardiac surgery.

Methods

A single-center retrospective review of all bypass surgeries performed over a 10-year period (2003–2012).

Results

Of a total of 2325 patients registered in our database, the DSC group included 259 cases (11%), and the remaining 2066 cases (89%) constituted the control group (PSC). RACHS-1 risk was higher for the DSC group (74% had a score of 3 or 4) than for the PSC group (82% had a score of 2 or 3). The most frequent diagnosis for the DSC group was transposition of the great arteries (28%). We found out that hemodynamic instability was the main indication observed in patients aged ≤ 8 years (63%), while bleeding was the principal indication for patients aged ≥ 8 years (94%) (p ≤ 0.001). The average time between surgery and sternal closure was 2.3 ± 1.4 days. Overall mortality rates were higher for patients of the DSC group (22%) than for the PSC group (8.7%) (OR: 0.4 (95% CI: 0.4 to 0.5), p < 0.05). There were six patients with DSC who developed mediastinitis (2.3%). The risk of mediastinitis was significantly higher when DSC was performed 4 days after the primary surgery.

Conclusions

DSC is an important management strategy for congenital cardiac surgery in infants and children. The prolonged sternal closure time is associated with an increased rate of postoperative mediastinitis.

Do Sedation and Neuromuscular Blockade Influence the Outcome of Adult Intensive Care Patients? A Prospective Observational Study

A prospective observational study was conducted on patients admitted to an adult intensive care unit (ICU) to investigate the pattern of sedation, analgesia and neuromuscular blockade and to determine their relationship to patient outcomes. Data including age, gender, diagnoses, dosage of sedatives, analgesics and neuromuscular blocking agents (NMBA), duration of mechanical ventilation, admission and weaning sedation scores, ICU length of stay and outcomes were recorded; 1550 patient-days were studied from 140 mechanically ventilated patients, of which 52 (37%) received NMBA. The mean length of stay in patients receiving NMBA was 15.6 days compared to 11.7 in patients who did not receive them (p=0.08). Mean duration of mechanical ventilation was 12.5 days in patients receiving NMBA, while it was 10.2 days in patients who did not receive NMBA (p=0.21). Neuromuscular blockade did not significantly influence the duration of mechanical ventilation, length of stay and survival of ICU patients.

Planned re-laparotomy and the need for optimization of physiology and immunology

Planned re-laparotomy or damage control laparotomy (DCL), first described by Dr. Harlan Stone in 1983, has become a widely utilized technique in a broad range of patients and operative situations. Studies have validated the use of DCL by demonstrating decreased mortality and morbidity in trauma, general surgery and abdominal vascular catastrophes. Indications for planned re-laparotomy include severe physiologic derangements, coagulopathy, concern for bowel ischemia, and abdominal compartment syndrome. The immunology of DCL patients is not well described in humans, but promising animal studies suggest a benefit from the open abdomen (OA) and several human trials on this subject are currently underway. Optimal critical care of patients with OA's, including sedation, paralysis, nutrition, antimicrobial and fluid management strategies have been associated with improved closure rates and recovery.

Carbon dioxide clearance in critical care

Lung protective ventilation limiting tidal volumes and airway pressures were proven to reduce mortality in patients with acute severe respiratory failure. Hypercapnia and hypercapnic acidosis is often noted with lung protective ventilation. While the protective effects of lung protective ventilation are well recognised, the role of hypercapnia and hypercapnic acidosis remains debatable. Some clinicians argue that hypercapnia and hypercapnic acidosis protect the lungs and may be associated with improved outcomes. To the contrary, some clinicians do not tolerate hypercapnic acidosis and use various techniques including extracorporeal carbon dioxide elimination to treat hypercapnia and acidosis. This review aims at defining the effects of hypercapnia and hypercapnic acidosis with a focus on the pros and cons of clearing carbon dioxide and the modalities that may enhance carbon dioxide clearance.

Surgical strategies for management of the open abdomen

Since the mid-1990s the surgical community has seen a surge in the prevalence of open abdomens (OAs) reported in the surgical literature and in clinical practice. The OA has proven to be effective in decreasing mortality and immediate postoperative complications; however, it may come at the cost of delayed morbidity and the need for further surgical procedures. Indications for leaving the abdomen open have broadened to include damage control surgery, abdominal compartment syndrome, and abdominal sepsis. The surgical options for management of the OA are now more diverse and sophisticated, but there is a lack of prospective randomized controlled trials demonstrating the superiority of any particular method. Additionally, critical care strategies for optimization of the patient with an OA are still being developed. Review of the literature suggests a bimodal distribution of primary closure rates, with early closure dependent on postoperative intensive care management and delayed closure more affected by the choice of the temporary abdominal closure technique. Invariably, a small fraction of patients requiring OA management fail to have primary fascial closure and require some form of biologic fascial bridge with delayed ventral hernia repair in the future.

Postoperative neuromuscular blocker use is associated with higher primary fascial closure rates after damage control laparotomy

BACKGROUND

Failure to achieve fascial primary closure after damage control laparotomy (DCL) is associated with increased morbidity, higher healthcare expenditures, and a reduction in quality of life. The use of neuromuscular blocking agents (NMBA) to facilitate closure remains controversial and poorly studied. The purpose of this study was to determine whether exposure to NMBA is associated a higher likelihood of primary fascial closure.

METHODS

All adult trauma patients admitted between January 2002 and May 2008 who (1) went directly to the operating room, (2) were managed initially by DCL, and (3) survived to undergo a second laparotomy. Study group (NMBA+): those receiving NMBA in the first 24 hours after DCL. Comparison group (NMBA-): those not receiving NMBA in the first 24 hours after DCL. Primary fascial closure defined as fascia-to-fascia approximation by hospital day 7.

RESULTS

One hundred ninety-one patients met inclusion (92 in NMBA+ group, 99 in NMBA- group). Although the NMB+ patients were younger (31 years vs. 37 years, p = 0.009), there were no other differences in demographics, severity of injury, or lengths of stay between the groups. However, NMBA+ patients achieved primary closure faster (5.1 days vs. 3.5 days, p = 0.046) and were more likely to achieve closure by day 7 (93% vs. 83%, p = 0.023). After controlling for age, gender, race, mechanism, and severity of injury, logistic regression identified NMBA use as an independent predictor of achieving primary fascial closure by day 7 (OR, 3.24, CI: 1.15-9.16; p = 0.026).

CONCLUSIONS

Early NMBA use is associated with faster and more frequent achievement of primary fascial closure in patients initially managed with DCL. Patients exposed to NMBA had a three times higher likelihood of achieving primary fascial closure by hospital day 7.

To close or not to close? Treatment of abdominal compartment syndrome by neuromuscular blockade without laparostomy

Abdominal compartment syndrome (ACS) is a recognised postoperative complication seen frequently in the intensive care unit (ICU). Surgical decompression and laparostomy remain the gold standard treatment for established ACS, combined with supportive non-surgical therapy, such as nasogastric decompression. In the following case report, we describe our successful management of a patient with established postoperative ACS by re-laparotomy to exclude a reversible cause, immediate re-closure of the abdomen and prolonged neuromuscular blockade, avoiding a laparostomy.

Impact of sustained neuromuscular blockade on outcome of mechanically ventilated children

BACKGROUND

Neuromuscular blocking agents (NMBA) are commonly administered to critically ill children in pediatric intensive care units (PICU) in the USA and Europe. Although NMBA are frequently used in PICU patients, their role in the PICU setting has not yet been clearly defined. The aim of this study was to describe the sustained administration of NMBA and its impact on outcome of PICU patients.

METHODS

A 3-year retrospective cohort study was conducted to compare mechanically-ventilated patients who received NMBA for at least 12 h with patients who did not (control group).

RESULTS

A total of 317 consecutive patients were ventilated over 3473 days. Patients were similar in age, weight and severity scores. Thirty-four children (10.7%) received NMBA. Compared with controls, the neuromuscular blockade (NMB) group had a longer duration of mechanical ventilation (13.7 vs 5.5 days, P= 0.000), longer PICU stay (20 vs 11 days, P= 0.000) and increased occurrence of ventilator-associated pneumonia (6.6 vs 4.1/1000 ventilator days, P= 0.010). The NMB use was not associated with higher mortality (8.8% vs 17.6%, P= 0.287) or longer hospital stay (30.5 vs 23 days, P= 0.117).

CONCLUSION

Although the use of NMBA was not associated with greater mortality, we found that sustained use of NMBA is associated with prolonged mechanical ventilation, longer PICU stay and higher incidence of ventilator-associated pneumonia when compared with controls. Larger studies are necessary to confirm these findings.

The effect of neuromuscular blockers in patients with intra-abdominal hypertension

OBJECTIVE

The objective was to prospectively study the effect of neuromuscular blockers on intra-abdominal pressure (IAP) and a number of physiological variables in patients with increased IAP.

DESIGN

Prospective cohort study.

SETTING

Intensive care unit of the Ghent University Hospital.

PATIENTS AND PARTICIPANTS

Ten critically ill patients with intra-abdominal hypertension (IAH).

INTERVENTIONS

An intravenous bolus of cisatracurium at a dose of 0.15 mg/kg was administered, and IAP was measured just before administration and then at 15, 30, 60 and 120 min. The effect of cisatracurium on central venous pressure (CVP), mean arterial pressure (MAP), abdominal perfusion pressure (APP) and heart rate (HR) was also evaluated. Urinary output was recorded prior to administration and after 60 and 120 min.

MEASUREMENTS AND RESULTS

The median age of the patients was 50 years (interquartile range 38-65); five of them were male. APACHE II score on admission was 29 (IQR 14-37). IAH was caused by massive fluid resuscitation without obvious abdominal problem in five patients, by abdominal trauma in three, and by burns and bowel distension in one patient each. Bolus administration of cisatracurium significantly decreased IAP from 18 mmHg (16-20) at baseline to 14 mmHg (12-16) at 15 min (p = 0.01) and to 14 mmHg (13-17) at 30 min (p = 0.02). MAP, APP, CVP and HR remained unchanged. No significant effect on urinary output was observed. In all patients, IAP returned to the baseline level after 2 h.

CONCLUSIONS

Bolus administration of cisatracurium can be used to temporarily reduce IAP in patients with IAH.

Medical management of cerebral edema

✓Cerebral edema is frequently encountered in clinical practice in critically ill patients with acute brain injury from diverse origins and is a major cause of increased morbidity and death in this subset of patients. The consequences of cerebral edema can be lethal and include cerebral ischemia from compromised regional or global cerebral blood flow (CBF) and intracranial compartmental shifts due to intracranial pressure gradients that result in compression of vital brain structures. The overall goal of medical management of cerebral edema is to maintain regional and global CBF to meet the metabolic requirements of the brain and prevent secondary neuronal injury from cerebral ischemia. Medical management of cerebral edema involves using a systematic and algorithmic approach, from general measures (optimal head and neck positioning for facilitating intracranial venous outflow, avoidance of dehydration and systemic hypotension, and maintenance of normothermia) to specific therapeutic interventions (controlled hyperventilation, administration of corticosteroids and diuretics, osmotherapy, and pharmacological cerebral metabolic suppression). This article reviews and highlights the medical management of cerebral edema based on pathophysiological principles in acute brain injury.

“Early” Delayed Sternal Closure Following Pediatric Cardiac Surgery

BACKGROUND

Delayed sternal closure is commonly used following pediatric cardiopulmonary bypass surgery for many reasons including support of the failing myocardium. We hypothesized that, as a result of improvements in perioperative care, sternal closure could be achieved at an earlier postoperative time than the 3 to 5 days typically reported in the literature.

METHODS

Retrospective chart review of all bypass surgery (n = 585) performed in a single center over a 3-year period (2000-2002).

RESULTS

We identified 66 children (11.3%), median age 5 days old, who underwent delayed sternal closure. In 60 of these patients, sternal closure was achieved at a median (interquartile) postoperative time of 21 hours (18 to 40 hours). The most common indication was inadequate hemostasis, although early sternal closure was also achieved in the subgroup with poor myocardial function as the primary indication at a median of 36 hours (21 to 44 hours). There was no noticeable hemodynamic, respiratory or metabolic compromise following sternal closure, although patients with poor myocardial function tended to have a lower mean blood pressure than those with inadequate hemostasis (ANOVA, p = 0.02). The overall mortality was 19.7% (13 of 66), with a median duration of ventilation and intensive care stay among survivors of 3.8 days (2.4 to 6.3 days) and 4.8 days (3.7 to 7.9 days), respectively.

CONCLUSIONS

Delayed sternal closure is possible at an earlier stage than previously reported.

New Anesthesia Techniques

Advances in anesthesia involve refinements in understanding, technique, and technology. These refinements have led to better control of the anesthetic state, effective anesthesia for a wider variety of situations, and the ability to bring sicker patients to the operating room. Although the molecular mechanisms underlying the general anesthetic state are unknown, evidence suggests a specific, receptor-based effect. This concept has allowed anesthesiologists to treat anesthetic end points of immobility, lack of awareness, and autonomic control separately. It is likely that anesthesia and naturally occurring sleep interact physiologically. New, processed EEG monitors may allow anesthesiologists to titrate more finely anesthetic dose, with possible benefits in terms of speed of recovery and detection of intraoperative awareness. Since the 1990s, new anesthetic drugs (propofol, desflurane/sevoflurane, cisatracurium) have enhanced greatly control of the anesthetic state. The new intravenous anesthetic agent dexmedetomidine offers sedation with preserved respiration and cognitive function. Although its role has yet to be defined fully, it currently plays a role in ICU sedation and monitored anesthesia care. New anesthesia ventilators have better monitoring and better flow delivery at high airway pressures. These improvements significantly narrow the performance gap between anesthesia and ICU ventilators. In patients with COPD, pulmonary hypertension, or severe hypoxemia, heliox may improve gas flow, and NO may reduce pulmonary vascular resistance and improve oxygenation.

Sedation and comfort issues in the ventilated infant and child

Intubated infants and children require optimal sedation and comfort measures. Key elements that ensure the provision of quality care for these patients include the use of pain, comfort, and sedation assessment tools; pharmacologic and nonpharmacologic strategies; and the inclusion of the patient and parents as part of the team. This article describes approaches for using sedation and ensuring comfort in these patients. Application of research and the education of team members and the patient and family are crucial aspects of care and are also discussed.

Sedation in neurointensive care: advances in understanding and practice

PURPOSE OF REVIEW

To evaluate the rationale and the pharmacologic options for sedating neurointensive care patients.

RECENT FINDINGS

Sedation is a fundamental element in the neurointensive care unit. Even if the sedative strategy in the neurointensive care unit shares the same general aims with intensive care, the characteristics of the patients in the neurointensive care unit pose other unique challenges and some specific indications. The primary aim of neurointensive care is to maintain adequate cerebral perfusion pressure, to control intracranial pressure, and to maintain an adequate mean arterial pressure. Reducing the brain's metabolic demand is an important treatment strategy, and analgesic and sedative agents are used to prevent undesirable increases in intracranial pressure. There are many different pharmacologic agents available, each with distinct advantages and disadvantages.

SUMMARY

The pharmacokinetic and pharmacologic effects of the available sedatives used in neurointensive care patients are reviewed.