Clinical pharmacokinetics of neuromuscular relaxants in pregnancy

Acute Respiratory Failure in Pregnancy

Respiratory failure may affect up to 1 in 500 pregnancies, due to pregnancy-specific conditions, conditions aggravated by the pregnant state, or other causes. Management during pregnancy is influenced by altered maternal physiology, and the presence of a fetus influencing imaging, and drug therapy choices. Few studies have addressed the approach to invasive mechanical ventilatory management in pregnancy. Hypoxemia is likely harmful to the fetus, but precise targets are unknown. Hypocapnia reduces uteroplacental circulation, and some degree of hypercapnia may be tolerated in pregnancy. Delivery of the fetus may be considered to improve maternal respiratory status but improvement does not always occur.

Prolonged duration of action of suxamethonium in pregnant and postpartum patients: A registry study

BACKGROUND

Suxamethonium is hydrolysed by butyrylcholinesterase (BChE) and a low BChE activity can result in a prolonged duration of action of suxamethonium. The BChE activity is reduced during pregnancy and postpartum period by up to 33%. However, it can also be reduced by mutations in the BChE gene. In this study, we assessed BChE activity and mutations in the BChE gene in pregnant and postpartum patients with prolonged duration of action of suxamethonium. It was hypothesised that at least 30% of patients with a low BChE activity did not have a mutation in the BChE gene.

METHODS

In this registry study we focused on pregnant and postpartum patients with a history of prolonged duration of action of suxamethonium referred to the Danish Cholinesterase Research Unit (DCRU) between March 2007 and January 2023. Primary outcome was the proportion of patients without a mutation among patients with a low BChE activity. Secondary outcomes were the proportion of patients with a low BChE activity and the proportion of patients with a mutation out of the total number of patients.

RESULTS

A total of 40 patients were included and among patients with a low BChE activity, 6% (95% CI: 1%-21%) did not have a mutation. Out of the total number of included patients referred to the DCRU, 90% (95% CI: 76%-97%) had a mutation and 94% (95% CI: 80%-99%) had a low BChE activity.

CONCLUSION

Among pregnant and postpartum patients with a history of prolonged duration of action of suxamethonium and a low BChE activity, 6% did not have a mutation in the BChE gene. Our findings suggest that during pregnancy and postpartum clinically relevant prolonged duration of action of suxamethonium rarely occurs in genotypically normal patients.

Pregnancy and Severe ARDS with COVID-19: Epidemiology, Diagnosis, Outcomes and Treatment

Pregnancy-related acute respiratory distress syndrome (ARDS) is fast becoming a growing and clinically relevant subgroup of ARDS amidst global outbreaks of various viral respiratory pathogens that include H1N1-influenza, severe acute respiratory syndrome (SARS), middle east respiratory syndrome (MERS), and the most recent COVID-19 pandemic. Pregnancy is a risk factor for severe viral-induced ARDS and commonly associated with poor maternal and fetal outcomes including fetal growth-restriction, preterm birth, and spontaneous abortion. Physiologic changes of pregnancy further compounded by mechanical and immunologic alterations are theorized to impact the development of ARDS from viral pneumonia. The COVID-19 sub-phenotype of ARDS share overlapping molecular features of maternal pathogenicity of pregnancy with respect to immune-dysregulation and endothelial/microvascular injury (i.e., preeclampsia) that may in part explain a trend toward poor maternal and fetal outcomes seen with severe COVID-19 maternal infections. To date, current ARDS diagnostic criteria and treatment management fail to include and consider physiologic adaptations that are unique to maternal physiology of pregnancy and consideration of maternal-fetal interactions. Treatment focused on lung-protective ventilation strategies have been shown to improve clinical outcomes in adults with ARDS but may have adverse maternal-fetal interactions when applied in pregnancy-related ARDS. No specific pharmacotherapy has been identified to improve outcomes in pregnancy with ARDS. Adjunctive therapies aimed at immune-modulation and anti-viral treatment with COVID-19 infection during pregnancy have been reported but data in regard to its efficacy and safety is currently lacking.

The Use of Muscle Relaxants in Pregnancy and Puerperium Period

Introduction

Anaesthetising a pregnant woman and during the postpartum period is challenging for most anaesthetists. There are many factors involved, including all the physiological changes that occur in the body of such a woman. Particular attention should be paid to muscle relaxants.

Aim

The purpose of this article is to present the use of muscle relaxants in pregnancy and puerperium period.

Material and Methods

This work is based on the available literature and the authors' experience.

Conclusion

In our experience and from a broad review of the medical literature, a great deal of caution should be exercised when using muscle relaxants during the anaesthesia of pregnant or postpartum patients. The pharmacodynamic and pharmacokinetic differences in the action of this group of drugs during this period should be known.

Onset and duration of cis-atracurium neuromuscular block during fentanyl and lidocaine infusions in isoflurane-anaesthetised dogs

BACKGROUND

This retrospective study assessed the onset and duration of the neuromuscular block (NMB) induced by cis-atracurium 0.15 mg/kg intravenously with and without fentanyl or lidocaine infusions in 45 isoflurane-anaesthetised dogs.

METHODS

Dogs with neuromuscular function assessed by a calibrated train-of-four (TOF) monitor with stimulation (every 13 s) of the peroneal nerve were included. The onset and duration of the NMB were defined as the time from cis-atracurium administration until TOF=0 and the time during TOF=0 display, respectively.

RESULTS

The NMB onset was shorter during fentanyl (mean±sd) (1.9±0.7 minutes; P=0.0042) and lidocaine (2.0±0.7 minutes; P=0.0154) compared with control (2.9±0.8 minutes). The NMB duration was shorter in the fentanyl (27.5±7.3 minutes; P=0.0491), but not in the lidocaine group (32.3±6.9 minutes; P=0.0790), compared with control (33.7±9.1 minutes). The NMB onset was poorly but significantly correlated with the dose of fentanyl and lidocaine administered before cis-atracurium (r=-0.3396; P=0.0225). The fentanyl and lidocaine groups received more crystalloid and colloid boluses than the control.

CONCLUSIONS

Fentanyl and lidocaine shortened the NMB onset and the former decreased the NMB duration. Further prospective studies are required to clarify whether this was associated with an indirect decrease in blood pressure or a direct interaction between cis-atracurium and fentanyl and lidocaine.

The influence of mode of anaesthesia for caesarean delivery on neonatal Apgar scores in the Czech Republic and Slovakia: secondary analysis of the results of an international survey in 2015

AIMS

The purpose of this international survey was to describe the impact of current practices and techniques of caesarean section on the neonatal Apgar score in the Czech Republic (CZE) and Slovakia (SVK).

METHODS

All Czech and Slovak departments that provide obstetric anaesthesia were invited to participate in a one-month (November 2015) prospective study that monitored in details all peripartum anaesthetic practices, delivered by anaesthesiologists. Participating centers recorded all data on-line in the CLADE-IS database (Masaryk University, CZE).

RESULTS AND DISCUSSIONS

We collected data of 10119 women who delivered 10226 newborns. A caesarean section was recorded in 25.1% of deliveries (CZE 23.2%; SVK 30%). General anaesthesia was used for caesarean section in 37.5% of the cases (CZE 40%, SVK 33%). There was no statistically significant difference in the Apgar score lower than 7 in the 1, 5 or 10 min in groups of general and regional anaesthesia for caesarean section, when only elective sections of in-term babies with birth weight over 2500 g were analyzed. We found no statistically significant differences in the Apgar score in newborns of women intubated for caesarean section in rocuronium (n=21; 2.2%) and suxamethonium (n=889; 93%).

CONCLUSION

We found no difference in neonatal outcomes in groups of general and regional anaesthesia for caesarean section when only out-of-risk newborns were analyzed. The risk factors were identified as follows: an acute caesarean section, preterm babies, birth weight less than 2 500 g, born in perinatological center and multiple pregnancy - second baby.

TRIAL REGISTRATION

ClinicalTrials.gov (ID: NCT02380586) https://clinicaltrials.gov/ct2/show/NCT02380586.

Anaesthesia in electroconvulsive therapy. Special conditions

OBJECTIVES

Electroconvulsive therapy (ECT) is one of the main techniques available for the treatment of such serious mental illnesses as schizophrenia and drug-resistant depression. The pre-anaesthetic assessment appropriate for patients with various mental disorders or pathologies does not differ substantially from that of any patient prior to undergoing anaesthesia for a surgical procedure. The present review aims to propose guidelines to achieve a higher level of safety and effectiveness during ECT in the most frequent situations, in accordance with the current literature.

METHODS

We conducted a search on the role of anaesthesia in ECT in the Ovid MEDLINE, PubMed, and SciELO (Scientific Electronic Library Online) databases, with special attention to the populations undergoing this type of therapy. The search was carried out between 1978 and December 2016.

RESULTS

We included the 96 articles that contained the most important recommendations for the preparation of this guide.

CONCLUSIONS

We propose these guidelines in order to achieve a higher level of safety and effectiveness during ECT in special conditions. We also summarize the most important attitude to be taken into account by the anaesthesiologist in these cases.

Factors that affect the onset of action of non-depolarizing neuromuscular blocking agents

Neuromuscular blockade plays an important role in the safe management of patient airways, surgical field improvement, and respiratory care. Rapid-sequence induction of anesthesia is indispensable to emergency surgery and obstetric anesthesia, and its purpose is to obtain a stable airway, adequate depth of anesthesia, and appropriate respiration within a short period of time without causing irritation or damage to the patient. There has been a continued search for new neuromuscular blocking drugs (NMBDs) with a rapid onset of action. Factors that affect the onset time include the potency of the NMBDs, the rate of NMBDs reaching the effect site, the onset time by dose control, metabolism and elimination of NMBDs, buffered diffusion to the effect site, nicotinic acetylcholine receptor subunit affinity, drugs that affect acetylcholine (ACh) production and release at the neuromuscular junction, drugs that inhibit plasma cholinesterase, presynaptic receptors responsible for ACh release at the neuromuscular junction, anesthetics or drugs that affect muscle contractility, site and methods for monitoring neuromuscular function, individual variability, and coexisting disease. NMBDs with rapid onset without major adverse events are expected in the next few years, and the development of lower potency NMBDs will continue. Anesthesiologists should be aware of the use of NMBDs in the management of anesthesia. The choice of NMBD and determination of the appropriate dosage to modulate neuromuscular blockade characteristics such as onset time and duration of neuromuscular blockade should be considered along with factors that affect the effects of the NMBDs. In this review, we discuss the factors that affect the onset time of NMBDs.

Clinical Practice Guidelines for Sustained Neuromuscular Blockade in the Adult Critically Ill Patient

OBJECTIVE

To update the 2002 version of "Clinical practice guidelines for sustained neuromuscular blockade in the adult critically ill patient."

DESIGN

A Task Force comprising 17 members of the Society of Critical Medicine with particular expertise in the use of neuromuscular-blocking agents; a Grading of Recommendations Assessment, Development, and Evaluation expert; and a medical writer met via teleconference and three face-to-face meetings and communicated via e-mail to examine the evidence and develop these practice guidelines. Annually, all members completed conflict of interest statements; no conflicts were identified. This activity was funded by the Society for Critical Care Medicine, and no industry support was provided.

METHODS

Using the Grading of Recommendations Assessment, Development, and Evaluation system, the Grading of Recommendations Assessment, Development, and Evaluation expert on the Task Force created profiles for the evidence related to six of the 21 questions and assigned quality-of-evidence scores to these and the additional 15 questions for which insufficient evidence was available to create a profile. Task Force members reviewed this material and all available evidence and provided recommendations, suggestions, or good practice statements for these 21 questions.

RESULTS

The Task Force developed a single strong recommendation: we recommend scheduled eye care that includes lubricating drops or gel and eyelid closure for patients receiving continuous infusions of neuromuscular-blocking agents. The Task Force developed 10 weak recommendations. 1) We suggest that a neuromuscular-blocking agent be administered by continuous intravenous infusion early in the course of acute respiratory distress syndrome for patients with a PaO2/FIO2 less than 150. 2) We suggest against the routine administration of an neuromuscular-blocking agents to mechanically ventilated patients with status asthmaticus. 3) We suggest a trial of a neuromuscular-blocking agents in life-threatening situations associated with profound hypoxemia, respiratory acidosis, or hemodynamic compromise. 4) We suggest that neuromuscular-blocking agents may be used to manage overt shivering in therapeutic hypothermia. 5) We suggest that peripheral nerve stimulation with train-of-four monitoring may be a useful tool for monitoring the depth of neuromuscular blockade but only if it is incorporated into a more inclusive assessment of the patient that includes clinical assessment. 6) We suggest against the use of peripheral nerve stimulation with train of four alone for monitoring the depth of neuromuscular blockade in patients receiving continuous infusion of neuromuscular-blocking agents. 7) We suggest that patients receiving a continuous infusion of neuromuscular-blocking agent receive a structured physiotherapy regimen. 8) We suggest that clinicians target a blood glucose level of less than 180 mg/dL in patients receiving neuromuscular-blocking agents. 9) We suggest that clinicians not use actual body weight and instead use a consistent weight (ideal body weight or adjusted body weight) when calculating neuromuscular-blocking agents doses for obese patients. 10) We suggest that neuromuscular-blocking agents be discontinued at the end of life or when life support is withdrawn. In situations in which evidence was lacking or insufficient and the study results were equivocal or optimal clinical practice varies, the Task Force made no recommendations for nine of the topics. 1) We make no recommendation as to whether neuromuscular blockade is beneficial or harmful when used in patients with acute brain injury and raised intracranial pressure. 2) We make no recommendation on the routine use of neuromuscular-blocking agents for patients undergoing therapeutic hypothermia following cardiac arrest. 3) We make no recommendation on the use of peripheral nerve stimulation to monitor degree of block in patients undergoing therapeutic hypothermia. 4) We make no recommendation on the use of neuromuscular blockade to improve the accuracy of intravascular-volume assessment in mechanically ventilated patients. 5) We make no recommendation concerning the use of electroencephalogram-derived parameters as a measure of sedation during continuous administration of neuromuscular-blocking agents. 6) We make no recommendation regarding nutritional requirements specific to patients receiving infusions of neuromuscular-blocking agents. 7) We make no recommendation concerning the use of one measure of consistent weight over another when calculating neuromuscular-blocking agent doses in obese patients. 8) We make no recommendation on the use of neuromuscular-blocking agents in pregnant patients. 9) We make no recommendation on which muscle group should be monitored in patients with myasthenia gravis receiving neuromuscular-blocking agents. Finally, in situations in which evidence was lacking or insufficient but expert consensus was unanimous, the Task Force developed six good practice statements. 1) If peripheral nerve stimulation is used, optimal clinical practice suggests that it should be done in conjunction with assessment of other clinical findings (e.g., triggering of the ventilator and degree of shivering) to assess the degree of neuromuscular blockade in patients undergoing therapeutic hypothermia. 2) Optimal clinical practice suggests that a protocol should include guidance on neuromuscular-blocking agent administration in patients undergoing therapeutic hypothermia. 3) Optimal clinical practice suggests that analgesic and sedative drugs should be used prior to and during neuromuscular blockade, with the goal of achieving deep sedation. 4) Optimal clinical practice suggests that clinicians at the bedside implement measure to attenuate the risk of unintended extubation in patients receiving neuromuscular-blocking agents. 5) Optimal clinical practice suggests that a reduced dose of an neuromuscular-blocking agent be used for patients with myasthenia gravis and that the dose should be based on peripheral nerve stimulation with train-of-four monitoring. 6) Optimal clinical practice suggests that neuromuscular-blocking agents be discontinued prior to the clinical determination of brain death.

Rocuronium versus suxamethonium for rapid sequence induction of general anaesthesia for caesarean section: influence on neonatal outcomes

BACKGROUND

In a previous study we compared rocuronium and suxamethonium for rapid-sequence induction of general anaesthesia for caesarean section and found no difference in maternal outcome. There was however, a significant difference in Apgar scores. As this was a secondary outcome, we extended the study to explore this finding on a larger sample.

METHODS

We included 488 parturients of whom 240 were women from the original study. Women were randomly assigned to receive either rocuronium 1mg/kg (ROC n=245) or suxamethonium 1mg/kg (SUX n=243) after propofol 2mg/kg. Anaesthesia was maintained with up to 50% nitrous oxide and up to one minimum alveolar concentration of sevoflurane until the umbilical cord was clamped. We compared neonatal outcome using Apgar scores and umbilical cord blood gases.

RESULTS

Data were analysed for 525 newborns (ROC n=263vs. SUX n=262). There was a statistically significant difference in the proportion of Apgar scores <7 at 1min (ROC 17.5% vs. SUX 10.3%, P=0.023) but no difference at 5min (ROC 8% vs. SUX 4.2%, P=0.1) or 10min (ROC 3.0% vs. SUX 1.9%, P=0.58). There was no difference between groups in other measured outcomes.

CONCLUSION

The use of rocuronium was associated with lower Apgar scores at 1min compared with suxamethonium. The clinical significance of this is unclear and warrants further investigation.

Hypermagnesemia disturbances in rats, NO-related: pentadecapeptide BPC 157 abrogates, L-NAME and L-arginine worsen

AIM

Stable gastric pentadecapeptide BPC 157, administered before a high-dose magnesium injection in rats, might be a useful peptide therapy against magnesium toxicity and the magnesium-induced effect on cell depolarization. Moreover, this might be an NO-system-related effect. Previously, BPC 157 counteracts paralysis, arrhythmias and hyperkalaemia, extreme muscle weakness; parasympathetic and neuromuscular blockade; injured muscle healing and interacts with the NOS-blocker and NOS-substrate effects.

MAIN METHODS

Assessment included magnesium sulfate (560 mg/kg intraperitoneally)-induced muscle weakness, muscle and brain lesions, hypermagnesemia, hyperkalaemia, increased serum enzyme values assessed in rats during and at the end of a 30-min period and medication (given intraperitoneally/kg at 15 min before magnesium) [BPC 157 (10 µg, 10 ng), L-NAME (5 mg), L-arginine (100 mg), alone and/or together]. In HEK293 cells, the increasing magnesium concentration from 1 to 5 mM could depolarize the cells at 1.75 ± 0.44 mV.

KEY FINDINGS

L-NAME + magnesium-rats and L-arginine + magnesium-rats exhibited worsened severe muscle weakness and lesions, brain lesions, hypermagnesemia and serum enzymes values, with emerging hyperkalaemia. However, L-NAME + L-arginine + magnesium-rats exhibited all control values and normokalaemia. BPC 157 abrogated hypermagnesemia and counteracted all of the magnesium-induced disturbances (including those aggravated by L-NAME or L-arginine). Thus, cell depolarization due to increasing magnesium concentration was inhibited in the presence of BPC 157 (1 µM) in vitro.

SIGNIFICANCE

BPC 157 likely counteracts the initial event leading to hypermagnesemia and the life-threatening actions after a magnesium overdose. In contrast, a worsened clinical course, higher hypermagnesemia, and emerging hyperkalaemia might cause both L-NAME and L-arginine to affect the same events adversely. These events were also opposed by BPC 157.

Management of critical asthma syndrome during pregnancy

One-third of pregnant asthmatics experience a worsening of their asthma that may progress to a critical asthma syndrome (CAS) that includes status asthmaticus (SA) and near-fatal asthma (NFA). Patients with severe asthma before pregnancy may experience more exacerbations, especially during late pregnancy. Prevention of the CAS includes excellent asthma control involving targeted early and regular medical care of the pregnant asthmatic, together with medication compliance. Spontaneous abortion risk is higher in pregnant women with uncontrolled asthma than in non-asthmatics. Should CAS occur during pregnancy, aggressive bronchodilator therapy, montelukast, and systemic corticosteroids can be used in the context of respiratory monitoring, preferably in an Intensive Care Unit (ICU). Systemic epinephrine should be avoided due to potential teratogenic side-effects and placental/uterine vasoconstriction. Non-invasive ventilation has been used in some cases. Intratracheal intubation can be hazardous and rapid-sequence intubation by an experienced physician is recommended. Mechanical ventilation parameters are adjusted based on changes to respiratory mechanics in the pregnant patient. An inhaled helium-oxygen gas admixture may promote laminar airflow and improve gas exchange. Permissive hypercapnea is controversial, but may be unavoidable. Sedation with propofol which itself has bronchodilating properties is preferred to benzodiazepines. Case reports delineating good outcomes for both mother and fetus despite intubation for SA suggest that multidisciplinary ICU care of the pregnant asthmatic with critical asthma are feasible especially if hypoxemia is avoided.

Efficacy and safety of electroconvulsive therapy in the first trimester of pregnancy: a case of severe manic catatonia

OBJECTIVES

Electroconvulsive therapy (ECT) is an appropriate, albeit often neglected, option for managing severe or life-threatening psychiatric symptoms during pregnancy. We report on the rapid effectiveness and safety of ECT during the first trimester of pregnancy in a 28-year-old woman with severe catatonia.

METHODS

Catatonic symptoms were assessed using the Catatonia Rating Scale (CRS). The patient was treated with unilateral ECT using left anterior right temporal (LART) placement. Seizure quality and duration were monitored by a two-lead electroencephalograph (EEG) and by one-lead electromyography (EMG). During each ECT session, the fetal heart rate was monitored with electrocardiogram (ECG).

RESULTS

After the second ECT treatment (day 13 of hospitalization), we observed remission of the catatonic symptoms, as shown by the drop in the CRS score from 22 to 0. No cognitive abnormalities were reported and no gynecological complications were detected (e.g. vaginal bleeding, abdominal pain, or uterine contraction). The patient delivered at term a healthy male neonate who presented normal growth as well as normal psychomotor development.

CONCLUSIONS

This case highlights the effectiveness of ECT in treating severe catatonic mania during the first 3 months of pregnancy. In addition, ECT proved to be a safe therapeutic option, since neither mother nor infant experienced any adverse event. We suggest that ECT might be considered as a valid and safe option in the therapeutic decision-making process when catatonic symptoms manifest during pregnancy.

Critical care in pregnancy--is it different?

In the first part of this review, the epidemiology of obstetric critical care is discussed. This includes the incidence of severe morbidity in pregnancy, identification of critically ill and potentially critically ill patients, the incidence of obstetric ICU admissions, the type of critical illness by stage of pregnancy, ICU admission diagnoses, the severity of illness in obstetric ICU patients compared to non-obstetric patients, ICU mortality of obstetric patients, the ICU proportion of total maternal mortality, and the causes of death for obstetric patients in ICU. In the second part, the management of obstetric patients who happen to be admitted to a general ICU is discussed. Rather than focusing on the management of particular obstetric conditions, general principles of ICU management will be discussed as applied to obstetric ICU patients. These include drug safety, monitoring the fetus, management of the airway, sedation, muscle relaxation, ventilation, cardiovascular support, thromboprophylaxis, and radiology and ethical issues.

Fetal outcome in the critically ill pregnant woman

Management of the critically ill pregnant woman is complicated by potential adverse effects of both maternal illness and ICU interventions on the fetus. This paper reviews the potential risks to the fetus of maternal critical illness, including shock, hypoxemia, and fever, as well as the effects of critical care management, such as drug therapy and radiological investigations. The authors’ recommended approach to management is provided. Prior publications and new data presented identify that there is insufficient information to prognosticate accurately on fetal outcome after maternal critical illness, although maternal shock, hypoxemia and early gestational age are likely significant risk factors.

[Modified rapid sequence induction for Caesarian sections : case series on the use of rocuronium and sugammadex]

BACKGROUND

Aspiration is a feared complication of anesthesia and is accompanied by increased morbidity and mortality. Rapid sequence induction (RSI) describes the preferred procedure to perform endotracheal placement of the tubus in emergency cases of patients with an increased risk of aspiration of gastric contents. For more than 50 years RSI has consisted of the application of suxamethonium for neuromuscular blockade because of its fast onset and ultra short duration. Due to the serious side effects of suxamethonium attempts were made to find better alternative neuromuscular blocking drugs, e.g. rocuronium, to perform RSI.

MATERIALS AND METHODS

In this small clinical series RSI was performed for general anesthesia of ten pregnant women for Caesarean sections using 1.0 mg/kgBW rocuronium for induction and maintaining deep relaxation until the end of surgery. For rapid reversal of the neuromuscular blockade to a train-of-four (TOF) ratio of 0.9, the µ-cyclodextrin sugammadex was administered at the end of surgery. Major and minor side effects, such as cardiac dysrhythmia, anaphylactic reactions, hoarseness and postoperative nausea and vomiting were documented.

CONCLUSIONS

The combination of rocuronium and sugammadex for RSI combines rapid onset and rapid reversal of neuromuscular blockades with avoidance of serious side effects and very comfortable conditions for intubation in all cases. Minor side effects such as hoarseness, throat discomfort (in up to 30%) and myalgia (10%) for up to 48 h were documented.

The management of the critically ill obstetric patient

Hypertensive disorders, postpartum hemorrhage, and sepsis are the most common indications for intensive care unit admission among obstetric patients. In general, ICU mortality is low, and better than would be predicted using available mortality prediction tools. Provision of care to this special population requires an intimate understanding of physiologic changes that occur during pregnancy. Clinicians must be aware of the way various diagnostic and treatment choices can affect the mother and fetus. Most clinically necessary radiographic tests can be safely performed and fall under the maternal radiation exposure limit of less than 0.05 Gray (Gy). Careful attention must be paid to acid-base status, oxygenation, and ventilation when faced with respiratory failure necessitating intubation. Cesarean delivery can be justified after 4 minutes of cardiac arrest and may improve fetal and maternal outcomes. The treatment of obstetric patients in the ICU introduces complexities and challenges that may be unfamiliar to many critical care physicians; teamwork and communication with obstetricians is crucial.

Cesarean delivery in the obese parturient: anesthetic considerations

Obesity is a worldwide health problem and its prevalence is reaching epidemic proportions. As obesity does not spare women of childbearing age, obstetric anesthesiologists will increasingly be exposed to the challenges of anesthesia in this population. The purpose of this article is to give the reader a thorough understanding of the anesthetic implications of obesity relating to cesarean deliveries. Obesity is associated with hypertension, diabetes, obstructive sleep apnea and other comorbidities. It increases the risk of cesarean delivery, postpartum wound infections and deep venous thromboembolism. Obese parturients are prone to anesthetic complications such as aspiration of gastric contents, difficult monitoring, positioning, airway management and challenging neuraxial techniques. A thorough precesarean delivery preparation should include an evaluation by an anesthesiologist for women with a BMI over 40 kg/m² and institution of an antacid prophylaxis protocol, thromboprophylaxis and antibiotic prophylaxis. Regional anesthesia should ideally be used in all obese parturients unless contraindicated. The goals of postpartum care include efficacious analgesia, physiotherapy and early mobilization. Monitoring and vigilance in an intensive care unit or step-down units should be considered for morbidly obese women.

[Influence of gender on the potency and course of action of rocuronium bromide]

OBJECTIVE

The correlation between gender and the potency of certain neuromuscular blockers, including rocuronium, has been investigated. However, the methods used have been inconsistent. This study aimed to look further at the role of gender in order to arrive at definitive conclusions.

PATIENTS AND METHODS

In a first and second phases of the study, rocuronium dose-response curves were constructed for patient groups as follows: 2 mixed-gender groups, 2 female groups, and 2 male groups. One group in each set received a single dose. In the other group the effect of the accumulated dose was measured after each of 3 fractions. The doses were transformed logarithmically. The effect was monitored by electromyography, and probit analysis was used to calculate the effective dose to induce 50%, 90% and 95% of the maximum effect (ED50, ED90 and ED95, respectively) in each patient. In the third phase, a bolus dose of 400 microg-Kg(-1) was administered to 3 additional groups. Onset time, maximum effect, speed of onset, duration of effect as the 10%-25% recovery index, and speed of recovery were recorded. In the fourth phase analysis was restricted to measurements during the period of onset.

RESULTS

No significant between-group differences in mean (SD) ED50, ED90, or ED95 values were observed after single doses (female group: 176 [68], 252 [97], and 285 [110] microg x Kg(-1), respectively; male group: 187 [69], 271 [100], and 307 [114] microg x Kg(-1); mixed group: 172 [73], 233 [98], and 258 [109] microg x Kg(-1)). Assessment of effect after cumulative fracional doses gave the following mean values for ED50, ED90, and ED95: 249 (63), 310 (79), and 334 (85) microg x Kg(-1) for the female group; 261 (60), 327 (75), and 354 (81) microg x Kg(-1) for the male group; and 242 (70), 305 (88), and 330 (95) microg x Kg(-1) for the mixed group. No significant differences in measures of effect were found after bolus administration in the third phase.

CONCLUSIONS

These results suggest that there is no significant effect of gender on potency or course of action of rocuronium bromide. Reports of such differences based on previous studies may be the result of problems in the methods applied.

Perinatal neuroprotection by muscle relaxants against hypoxic-ischemic lesions: Is it a possible hypothesis?

The incidence of neurological disabilities ascribable to hypoxia-ischemia in the perinatal period (HIPP) is rising. Glutamate plays a key role in the development of cerebral damage related to HIPP: it triggers the excitotoxic cascade by overactivating N-methyl-D-aspartate receptors (NMDA), implicated as important mediators of both learning and neuronal development. Laudanosine is the metabolite of the neuromuscular blocking drugs, atracurium and cisatracurium, administered as part of obstetric general anesthesia. In elective cesarean section, laudanosine may be found in the fetus with a mean umbilical vein concentration of 26 (range 6-60) ng ml(-1). At nM concentrations, laudanosine can activate alpha4beta2 nACh subtype receptors. Activation of alpha4beta2 nAChRs provided neuroprotection against NMDA excitotoxic cascade in a neonatal model. Taken together, experimental and clinical data widely indicate a potential neuroprotective role for laudanosine against perinatal brain lesions of hypoxic-ischemic origin. The clinical relevance is that administration of the neuromuscular blocking drugs atracurium and cisatracurium, administered as part of general anesthesia for cesarean section, could be potentially therapeutic in obstetric anesthesia. Therefore, we find laudanosine to be an attractive proposal for further studies in the prevention of neurological disabilities ascribable to perinatal injury related to hypoxia and ischemia.

Management of the obstetric patient with status asthmaticus

Status asthmaticus requiring mechanical ventilation is an uncommon, life-threatening disorder in obstetric patients. The unique physiologic changes of pregnancy, impact of the fetus on the maternal condition, and concerns for fetal and maternal health and survival are particular concerns in critical illness. Furthermore, the issues of hypoxemia and hypercapnia, ventilator management and complications make this disease of respiratory failure an especially important area for review. There is abundant literature on the management of asthma during pregnancy; however the literature is very limited in those with status asthmaticus who require intensive care unit admission. We report our intensive care unit experience in the management of status asthmaticus in 5 pregnant patients and review the literature on management of status asthmaticus during pregnancy.

Psychiatric disorders during pregnancy

Treating women with psychiatric disorders during pregnancy is a challenge for numerous reasons. Balancing the risks and benefits of symptoms and treatments is particularly important during pregnancy because both medication and maternal illness may have adverse effects on the fetus. Communication of options in the management of psychiatric disorders in pregnancy is vital to optimal treatment. One barrier to effective communication has been a paucity of research from which clinicians can draw information, particularly in the area of pharmacological treatment. However, emerging evidence points to the low risk of many psychotropic medications during pregnancy. Uncertainty must not prevent frank risk-benefit discussions from occurring between treating physicians and their pregnant patients. Psychiatrists can prepare themselves for management decisions by reviewing the current literature.

The use of electroconvulsive therapy in special patient populations

BACKGROUND

Despite its well-established efficacy and its increasing use, electroconvulsive therapy (ECT) remains a controversial treatment. Lack of clarity in the issues related to its use in special patient populations (for example, in children, in adolescents, in pregnant women, in the elderly, and in the medically ill) often contributes to the debate about the use of ECT.

METHOD

The literature on ECT use in special patient populations is reviewed, together with the commonly associated high-risk medical conditions in clinical practice. Specific reference is made in each case to the safety, tolerability, and efficacy of the procedure.

RESULTS

Much of the literature surveyed consists of case studies, although a few controlled trials are available. In general, ECT use in special populations is relatively safe and extremely effective. In small case series, ECT use in children and adolescents is effective but requires further systematic study. In pregnant women, ECT is very effective, and with proper medical care, it is relatively safe in all trimesters of pregnancy, as well as in the postpartum period. The frail elderly are particularly good candidates for ECT because they are often unresponsive to or intolerant of psychotropic medication. Medical conditions that should receive particular attention during a course of ECT are disorders of the central nervous system (CNS), cardiovascular, and respiratory system. With modern anesthesia techniques and careful medical management of each high-risk patient, most can successfully complete a course of ECT. The process of obtaining informed consent also requires special consideration in this group of patients because their capacity to consent to treatment may be compromised.

CONCLUSIONS

With careful attention to each patient's medical and anesthesia needs, ECT is an effective and relatively safe procedure in high-risk special patient populations.

Gender differences in depression and antidepressant pharmacokinetics and adverse events

OBJECTIVE

To review data generated by studies examining gender differences in the prevalence of depression, as well as in antidepressant pharmacokinetics, pharmacodynamics, and adverse events.

DATA SOURCES

Published articles and abstracts were identified through MEDLINE (January 1966-April 1999) using the following search terms: antidepressant, response, gender, pharmacokinetic, pharmacodynamic, female, side effect, and adverse events. All articles that assessed gender differences in antidepressant response, pharmacokinetics, and adverse events, as well as articles that evaluated postulated mechanisms for these differences, were reviewed. Additional articles were identified from bibliographies of retrieved articles.

STUDY SELECTION AND DATA EXTRACTION

All relevant abstracts, studies, and review articles were evaluated.

DATA SYNTHESIS

Gender differences in the prevalence of depression have been reported and may result from the interaction of several factors. Women have been shown to have a higher incidence of depression, which may be due to artifact, social, or biologic reasons. Studies suggest that the pharmacokinetic disposition of popular antidepressants varies between men and women, and women taking antidepressants may exhibit a different adverse event profile. Only one study specifically evaluated gender differences in antidepressant treatment response.

CONCLUSIONS

Further research elucidating gender differences in response to antidepressant treatment and on depression prevalence is needed. Some studies report that the pharmacokinetics of antidepressants may vary between men and women. Therefore, clinicians should be aware that potential differences in antidepressant pharmacokinetics may exist, and a dosage adjustment may be necessary for women to ensure a favorable drug response, compliance, and decreased incidence of adverse events.