The effect of neuromuscular blockade on oxygen supply, consumption, and total chest compliance in patients with high oxygen requirements undergoing mechanical ventilation

Use of neuromuscular blockade for neck dissection and association with iatrogenic nerve injury

BACKGROUND

Cranial nerve injury is an uncommon but significant complication of neck dissection. We examined the association between the use of intraoperative neuromuscular blockade and iatrogenic cranial nerve injury during neck dissection.

METHODS

This was a single-center, retrospective, electronic health record review. Study inclusion criteria stipulated patients > 18 years who had ≥ 2 neck lymphatic levels dissected for malignancy under general anesthesia with a surgery date between 2008 - 2018. Use of neuromuscular blockade during neck dissection was the primary independent variable. This was defined as any use of rocuronium, cisatracurium, or vecuronium upon anesthesia induction without reversal with sugammadex prior to surgical incision. Univariate tests were used to compare variables between those patients with, and those without, iatrogenic cranial nerve injury. Multivariable logistic regression determined predictors of cranial nerve injury and was performed incorporating Firth's estimation given low prevalence of the primary outcome.

RESULTS

Our cohort consisted of 925 distinct neck dissections performed in 897 patients. Neuromuscular blockade was used during 285 (30.8%) neck dissections. Fourteen instances (1.5% of surgical cases) of nerve injury were identified. On univariate logistic regression, use of neuromuscular blockade was not associated with iatrogenic cranial nerve injury (OR: 1.73, 95% CI: 0.62 - 4.86, p = 0.30). There remained no significant association on multivariable logistic regression controlling for patient age, sex, weight, ASA class, paralytic dose, history of diabetes, stroke, coronary artery disease, carotid atherosclerosis, myocardial infarction, and cardiac arrythmia (OR: 1.87, 95% CI: 0.63 - 5.51, p = 0.26).

CONCLUSIONS

In this study, use of neuromuscular blockade intraoperatively during neck dissection was not associated with increased rates of iatrogenic cranial nerve injury. While this investigation provides early support for safe use of neuromuscular blockade during neck dissection, future investigation with greater power remains necessary.

Neuromuscular blockade with rocuronium bromide increases the tolerance of acute normovolemic anemia in anesthetized pigs

BACKGROUND

The patient's individual anemia tolerance is pivotal when blood transfusions become necessary, but are not feasible for some reason. To date, the effects of neuromuscular blockade (NMB) on anemia tolerance have not been investigated.

METHODS

14 anesthetized and mechanically ventilated pigs were randomly assigned to the Roc group (3.78 mg/kg rocuronium bromide followed by continuous infusion of 1 mg/kg/min, n = 7) or to the Sal group (administration of the corresponding volume of normal saline, n = 7). Subsequently, acute normovolemic anemia was induced by simultaneous exchange of whole blood for a 6% hydroxyethyl starch solution (130/0.4) until a sudden decrease of total body O(2) consumption (VO(2)) indicated a critical limitation of O(2) transport capacity. The Hb concentration quantified at this time point (Hb(crit)) was the primary endpoint of the protocol. Secondary endpoints were parameters of hemodynamics, O(2) transport and tissue oxygenation.

RESULTS

Hb(crit) was significantly lower in the Roc group (2.4 ± 0.5 vs. 3.2 ± 0.7 g/dl) reflecting increased anemia tolerance. NMB with rocuronium bromide reduced skeletal muscular VO(2) and total body O(2) extraction rate. As the cardiac index increased simultaneously, total body VO(2) only decreased marginally in the Roc group (change of VO(2) relative to baseline -1.7 ± 0.8 vs. 3.2 ± 1.9% in the Sal group, p < 0.05).

CONCLUSION

Deep NMB with rocuronium bromide increases the tolerance of acute normovolemic anemia. The underlying mechanism most likely involves a reduction of skeletal muscular VO(2). During acellular treatment of an acute blood loss, NMB might play an adjuvant role in situations where profound stages of normovolemic anemia have to be tolerated (e.g. bridging an unexpected blood loss until blood products become available for transfusion).

[Effects of sedative agents on metabolic demand]

Literature about the effects of sedative drugs on the metabolic demand of critically ill patients is relatively old and of relatively poor quality. Most are experimental or observational studies. Level of evidence is therefore relatively low corresponding to "expert opinion". The effects of analgesics and hypnotics on tissue metabolic demand associated remain difficult to be adequately quantified. They are essentially related to a decreased neuro-humoral response to stress. This response involves principally the sympathetic system, which could be effectively blocked by most of the anesthetic agents. Other factors could participate to the observed reduction in tissue metabolic demand, as a decrease in spontaneous muscular activity, a reduction in work of breathing and/or a decrease in body temperature. The relative contribution of these different factors will depend on the clinical situation of the patient. Proper effects of anesthetic agents on cellular metabolism are limited as they can only decrease the functional component of this metabolism especially at the level of the heart and to some extent, at the level of the brain. Although the control of the sympathetic activity may be beneficial in critically ill patient, complete sympathetic blockade could be detrimental. Indeed, when oxygen transport to the tissues is acutely reduced, the sympathetic system plays an important role in the redistribution of blood flow according of local metabolic demand. The complete blunting of the neuro-humoral response to stress and therefore of the sympathetic system alters this physiological mechanism and results in a decrease in tissue oxygen extraction capabilities. An imbalance between tissue oxygen demand and delivery could appear with the development of cellular hypoxia. The institution of sedation in a critically ill patient requires careful evaluation of the sedation level using an appropriate scale. In patients in whom a reduction in metabolic demand is specifically requested, but also in patients with limited oxygen transport, the effects of sedative agents on the oxygen consumption-oxygen delivery relationship must also be monitored. The choice of the different agents to be administered will depend on the predefined objectives. As far as intravenous agents are concerned, there is no evidence than one association is more efficient in reducing patient's metabolic demand.

Muscle relaxation does not influence venous oxygen saturation during cardiopulmonary bypass

STUDY OBJECTIVE

To examine whether the omission of neuromuscular blocking drugs during cardiopulmonary bypass (CPB) is associated with increased anesthetic requirements, higher frequency of intraoperative movements, and lower venous oxygen saturation (SvO(2)).

DESIGN

Prospective, randomized study.

SETTING

Large community hospital.

PATIENTS

30 ASA physical status III and IV patients scheduled for cardiac surgery.

INTERVENTIONS

Patients were randomized to one of two groups: group 1 (n = 15) received a 3xED(95) bolus dose of cisatracurium at induction and thereafter no more neuromuscular blocking drug; group 2 (n = 15) received a continuous infusion of cisatracurium during the entire procedure.

INTERVENTIONS

Both groups received a standardized anesthetic with bispectral index-guided propofol target-controlled infusion and a remifentanil infusion steered by hemodynamic changes. Venous oxygen saturation was continuously determined during CPB.

MEASUREMENTS AND MAIN RESULTS

Propofol consumption was 5.4 +/- 1.7 and 4.4 +/- 1.0 mg/(kg/h) in groups 1 and 2, respectively (P = 0.07). Remifentanil consumption was 0.15 +/- 0.05 and 0.17 +/- 0.05 mug/(kg/min) in groups 1 and 2, respectively (P = 0.19). In groups 1 and 2, no patient recalled any intraoperative phenomena; none moved or had diaphragmatic contractions. During CPB, SvO(2) was 81.3 +/- 3.2% (76%-85%) in group 1 and 80.6 +/- 3.1% (73%-85%) in group 2 (P = 0.53).

CONCLUSIONS

Omitting the continuous administration of neuromuscular blocking drugs during CPB did not increase anesthetic requirements. No intraoperative movements occurred, nor was there decreased SvO(2).

Clinical manifestations and neurodevelopmental outcome following an event of accidental intramuscular injection of atracurium in newborns

Pediatric populations are at risk for medication errors that may be associated with mortality and disability. The purpose of this study was to describe the clinical manifestations of seven newborns following an event of accidental intramuscular injection of atracurium and to assess the impact on neurodevelopmental outcome. This study enrolled seven newborns who were accidentally administered 10 mg of atracurium, equivalent to 2.6-3.3 mg/kg, in a local perinatal clinic. Accident reports and hospital records were reviewed to obtain the history and medical data for the event. The survivors were prospectively examined for their growth, health and neurodevelopment until 24 months of age. All newborns showed immediate apnea and cyanosis requiring resuscitation after atracurium injection and presented with respiratory failure and flaccid paralysis on arrival for emergency medical services. One newborn was asystolic despite resuscitation and died of multiple organ failure. Of the five survivors available for follow-up, all achieved favorable growth outcomes. However, four showed mild to significant delay in development; and two manifested mild hypomyelination of cerebral white matter on the brain magnetic resonance imaging.

CONCLUSION

Newborns accidentally injected with high doses of atracurium are at risk of death and neurodevelopmental delay. The serious clinical manifestations, developmental delay and cerebral hypomyelination were most likely due to insufficient immediate respiratory assistance following atracurium injection.