Management of the difficult and failed airway in obstetric anesthesia

Cardiac arrest in pregnancy

Cardiac arrest in pregnancy is a rare and frightening event. Although not every obstetrician will encounter cardiac arrest in pregnancy during their career, it is imperative to be prepared to manage this acute emergency. The management is particularly complex due to maternal physiologic changes from pregnancy and the simultaneous management of two patients, the mother and fetus. In 2010, the American Heart Association released their first scientific statement on guidelines for management of cardiac arrest in pregnancy that has since been updated in 2015. All providers who care for pregnant patients should be aware of these guidelines and ready to manage cardiac arrest in pregnancy because correct and timely interventions can affect real world outcomes.

Does neck circumference help to predict difficult intubation in obstetric patients? A prospective observational study

Background:

Failed intubation in obstetrics remains the most common cause of death directly related to anesthesia. Neck circumference has been shown to be a predictor for difficult intubation in morbidly obese patients. The aim of this study was to determine an optimal cutoff point of neck circumference for prediction of difficult intubation in obstetric patients.

Methods:

Ninety-four parturients scheduled for cesarean section under general anesthesia were included in the study. Preoperative airway assessment and neck circumference were measured. Difficult intubation was the primary outcome according to the intubation difficulty scale (IDS), intubation reported difficult if the IDS score was ≥5.

Results:

Univariate analysis showed that Mallampati score and neck circumference were positive predictors for difficult intubation (P = 0.005 and P = 0.011, respectively). Mouth opening, thyromental distance, sternomental distance, and the hyomental distance ratio were not useful predictors (P = 0.68, P = 0.87, P = 0.48, and P = 0.27, respectively). Logistic regression for the Mallampati score and neck circumference negative results as independent predictors of difficult intubation in obstetric (P = 0.53). Sensitivity analysis showed that neck circumference of 33.5 cm is the cutoff point to detect difficult intubation with 100% sensitivity (95% confidence interval [CI]: 69.2–100) and 50% specificity (95% CI: 38.9–61.1). The area under the curve for neck circumference was 0.746 (95% CI: 0.646–0.830) with a positive predictive value of 19.2 (95% CI: 9.6–32.5), a negative predicative value of 100 (95% CI: 91.6–100), and a P < 0.0001.

Conclusions:

In obstetric patients, a neck circumference ≥33.5 cm is a sensitive predictor for difficult intubation.

CXC Chemokine Receptor Type 4 Antagonism Ameliorated Allograft Fibrosis in Rat Kidney Transplant Model

OBJECTIVES

In this study, we evaluated the effects of CXC chemokine receptor type 4 and stromal cell-derived factor 1 signaling in the progression of chronic allograft nephropathy in a rat model.

MATERIALS AND METHODS

Experimental rats were divided into 3 groups: Lewis-to-Lewis isograft transplant (group A), Fisher 344 rat-to-Lewis allograft transplant with immunosuppressant cyclosporine (group B), and Fisher 344 rat-to-Lewis allograft transplant treated with cyclosporine and the CXC chemokine receptor type 4 antagonist AMD3100 (1 mg/kg/d) (group C). On day 90 after the operation, renal graft function, proteinuria, and histologic Banff score were measured. The expression levels of transforming growth factor β1 and collagen IV were determined by quantitative real-time polymerase chain reaction.

RESULTS

Renal function and urinary protein were increased in allografts of groups B and C compared with isografts of group A. The Banff score was significantly decreased in the AMD3100-treated animals (group C), with renal fibrosis being reduced. In addition, overexpressed levels of transforming growth factor β1 and collagen IV in group B allografts were significantly reduced versus that shown with treatment with the CXC chemokine receptor type 4 antagonist in group C.

CONCLUSIONS

Together, these data strongly implicate that CXC chemokine receptor type 4 antagonism alleviated renal interstitial fibrosis in long-term surviving allografts by down-regulating expression of transforming growth factor β1.

The anesthetic approach to operative delivery of the extremely obese parturient

Extreme obesity (BMI ≥ 40) is thought to complicate approximately 5% of deliveries in the United States. Extreme obesity puts a pregnant woman at an increased risk for cardiovascular disease, including hypertension, coronary artery disease, and congestive heart failure; respiratory disease, including obstructive sleep apnea and asthma; as well as pregnancy-specific diseases including pregnancy-induced hypertension and gestational diabetes. Extreme obesity also puts a parturient at a significantly increased risk of requiring cesarean delivery. For the anesthesiologist, the physiologic changes of obesity combined with the normal physiologic changes of pregnancy can make for a complex and challenging case. This review will focus on the anesthetic approach to the extremely obese parturient undergoing scheduled operative delivery. With proper planning and a detailed understanding of the patient's comorbidities, a safe and effective anesthetic can be achieved.

Maternal cardiac arrest: a practical and comprehensive review

Cardiac arrest during pregnancy is a dedicated chapter in the American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care; however, a robust maternal cardiac arrest knowledge translation strategy and emergency response plan is not usually the focus of institutional emergency preparedness programs. Although maternal cardiac arrest is rare, the emergency department is a high-risk area for receiving pregnant women in either prearrest or full cardiac arrest. It is imperative that institutions review and update emergency response plans for a maternal arrest. This review highlights the most recent science, guidelines, and recommended implementation strategies related to a maternal arrest. The aim of this paper is to increase the understanding of the important physiological differences of, and management strategies for, a maternal cardiac arrest, as well as provide institutions with the most up-to-date literature on which they can build emergency preparedness programs for a maternal arrest.

Jet or intensive care unit ventilator during simulated percutaneous transtracheal ventilation: a lung model study

BACKGROUND

Percutaneous transtracheal ventilation (PTV) via a jet ventilator (PTJV) is considered a rescue technique in difficult airway management. However, whether a conventional ventilator can generate adequate ventilation via PTV is not known. Our goal was to evaluate the tidal volume (V(T)) generated by a conventional ventilator during simulated PTV compared with PTJV in a lung model.

METHODS

A lung model simulating an adult lung was used. A catheter was inserted through the artificial trachea and connected to either a jet ventilator or a conventional ventilator. The direction of catheter insertion was perpendicular to the trachea, pointing towards the lung and away from the lung. The jet ventilator was operated at 344.7 kPa. The conventional ventilator was operated in the pressure mode at peak inspiratory pressures of 40-90 cm H(2)O.

RESULTS

The jet ventilator generated larger V(T) [817 (336) ml] when the catheter was pointing towards the lung than when pointing away from the lung or perpendicular to the trachea [121 (41) and 69 (24) ml, respectively, P<0.01]. With the conventional ventilator, changes in V(T) at different direction of catheter insertion were much less [222 (81) ml catheter pointing towards the lung, 229 (121) ml perpendicular to the trachea, and 187 (97) ml away from the lung].

CONCLUSIONS

Our result demonstrated that PTJV was effective only when the catheter was pointing towards the lung and requires high operating pressure. A conventional ventilator can generate reasonable minute ventilation through the transtracheal catheter less dependent on directions of catheter insertion and should be considered during emergent PTV.

When the Heart Stops

Cardiac arrest is a rare occurrence in pregnancy and may be related to obstetric or medical causes. Pregnancy is associated with profound physiologic changes that prepare the gravida for the challenges of labor and delivery, and resuscitation of the pregnant patient needs to take these changes into consideration. Cardiac output and plasma volume increase in pregnancy and distribute differently with the uterine circulation receiving approximately 17% of the total cardiac output. On the other hand, cardiac output is sensitive to positional changes in the second half of pregnancy but may improve with a lateral tilt of the gravida. Both oxygen reserve and upper airway size decrease in pregnancy, leading to difficulties surrounding airway management. Changes in the volume of distribution, renal and hepatic clearance may impact drug effects and need to be recognized. This review will discuss an overview of pregnancy physiology that is relevant to cardiac resuscitation, detail the challenges in the various resuscitative steps including a synopsis on perimortem delivery, and describe obstetric and nonobstetric causes of mortality and cardiac arrest in pregnancy.

Difficult intubation in pregnancy

PURPOSE OF REVIEW

This review focuses on difficult intubation in pregnant patients, particularly during the late pregnancy when physiological, patho-physiological and psychological factors may cause or aggravate difficulties with providing sufficient oxygenation and securing the airway. It is intended to highlight the methodological approach to the difficult airway in this particular patient population and to draw relevant principles in dealing with this problem.

RECENT FINDINGS

There are strong indications for improvement in the outcome of airway management in pregnant patients; however, this is obscured by the growing frequency of caesarean sections and connected to this by more tracheal intubations. Various new airway devices have been suggested as alternative techniques for laryngoscopic intubation if the latter becomes difficult or failed.

SUMMARY

A scenario-oriented approach to the problem of difficult intubation in pregnant patients leads to the recognition of the unpredicted difficult or failed intubation as the main concern. The appropriate means to cope with this rare but life-threatening complication lies in a gradual employment of principles beginning with preferential application of regional anaesthesia techniques, followed by proceeding according to locally adapted simple and comprehensive failed intubation algorithms, design of a suitable difficult airway cart that contains only a few but well chosen items and by implementation of a continuous and mandatory training program to which all personnel are subjected to participate in regular intervals.