Cardiac arrest during segmental thoracic epidural anesthesia

Postoperative monitoring in pregnant patients undergoing surgery for advanced malignancy in last trimester: How long is enough?

Surgery for advanced breast malignancy in the last trimester of pregnancy is uncommon. We present successful management of a 32-year-old woman, 30 weeks pregnant with stage 3 breast malignancy, for surgery followed by normal labor and chemotherapy. Surgery and intraoperative period were uneventful. Patient had uterine contractions 36 h postsurgery, which were managed timely with active interventions and tocolytics. Risk of premature labor following nonobstetric surgery in pregnant patients is estimated to be 8.3%, but majority of the studies have been carried out in second trimester following appendectomy. There is insufficient data in literature regarding the estimation and duration of persistence of risk of premature labor in these patients. No guidelines are available regarding how long they need to be monitored for premature labor. There is some evidence, although little that risk of premature labor persists for 7 days postsurgery. In the absence of convincing studies and guidelines, we recommend postoperative monitoring for at least 7 days in patients undergoing major surgeries for malignancies in last trimester. Multidisciplinary approach is required to manage these patients.

Witnessed asystole during spinal anesthesia treated with atropine and ondansetron: a case report

PURPOSE

To present a case of asystole during spinal anesthesia that responded to atropine and ondansetron and to discuss the possible pathophysiology with special emphasis on the Bezold-Jarisch reflex and the role of 5-HT3 receptors in mediating bradycardia and sympathoinhibition.

CLINICAL FEATURES

A 50-yr-old, 97-kg, healthy male presented for elective left high tibial osteotomy. Spinal anesthesia was induced uneventfully at L3-4 with 11.25 mg of hyperbaric 0.75% bupivacaine and morphine 0.25 mg. Thirteen minutes after induction, the incision site was infiltrated with 20 mL of 0.5% bupivacaine with epinephrine 5 microg.mL(-1) for intraoperative hemostasis, resulting in an increase in heart rate from 74 to 90 beats.min(-1). Three minutes after infiltration of the incision site, the patient's heart rate dropped to 48 beats.min(-1), accompanied by a blood pressure of 107/51 mmHg, SpO2 97%, and a sinus bradycardia on the electrocardiogram. The electrocardiographic complexes suddenly disappeared with loss of the pulse oximeter waveform. Pre-drawn atropine 0.6 mg i.v. and ondansetron 4 mg i.v. were administered within seven seconds of the event. After an asystolic period of 30 to 40 sec, but before chest compressions were initiated, vital signs returned to normal with no other sequelae.

CONCLUSION

Exogenous epinephrine may have triggered the Bezold-Jarisch reflex and subsequent asystole. It is postulated that the combination of atropine and ondansetron may have played a key role in resuscitation by blocking the serotonergic and cholinergic receptors in the afferent and efferent limbs of this vagally-mediated reflex.

Common mechanisms and strategies for prevention and treatment of cardiac arrest during epidural anesthesia

Cardiac arrests continue to occur during epidural anesthesia and frequently result in death or brain damage. Although unintentional "total spinal" anesthesia, respiratory depression, myocardial ischemia, and local anesthetic toxicity can also lead to cardiac arrest, often the arrests do not fit any of these four categories. Many of the unexplained arrests may be attributed to vagal predominance. The evidence for a vagal-linked circulatory mechanism for these arrests is reviewed, and the characteristics that are associated with an increased risk for cardiac arrest during epidural anesthesia are identified. Specific strategies to forestall vagal predominance are discussed. In case these strategies fail, multiple interventions are discussed that should increase the likelihood of a successful resuscitation in the setting of extensive sympathetic blockade.

Complete recovery of consciousness in a patient with decorticate rigidity following cardiac arrest after thoracic epidural injection

A 46-yr-old man with dysaesthesia (burning sensation) following herpes zoster in the left upper chest region was treated with a single thoracic (T2/T3) epidural injection (1.0% lidocaine 3 ml + 0.125% bupivacaine 3 ml) as an outpatient. Twenty minutes after the injection, a nurse noticed the patient to be unconscious with dilated pupils, apnoea and cardiac arrest. Following immediate cardiopulmonary resuscitation, the patient was treated with an i.v. infusion of thiamylal sodium 2-4 mg kg-1 h-1 and his lungs were mechanically ventilated. When the patient developed a characteristic decorticate posture, mild hypothermia (oesophageal temperature, 33-34 degrees C) was induced. On the 17th day of this treatment, after rewarming (35.5 degrees C) and discontinuation of the barbiturate, the patient responded to command. Weaning from the ventilator was successful on the 18th day. About 4 months after the incident, the patient was discharged with no apparent mental or motor disturbances. We suggest that mild hypothermia with barbiturate therapy may have contributed to the successful outcome in this case.

Mechanisms behind and treatment of sudden, unexpected circulatory collapse during central neuraxis blockade

Judging from the number of cases reported in the literature, severe bradycardia and/or asystole in association with central neuraxis blockade fortunately seems a rare complication. However, short periods of extreme bradycardia may go unnoticed and manifest cases, especially when outcome is favourable, may go unreported, and thus the real incidence may be much higher. Although the decrease in systemic blood pressure as a result of central neuraxis blockade is caused by various mechanisms, the most important factor causing severe hypotension, bradycardia and circulatory collapse is decreased venous return, and both prevention and treatment are aimed at preserving or restoring adequate venous return to the heart. Correction of preoperative hypovolaemia, limiting the extent of sensory blockade and positioning the patient so that gravity promotes venous return are the most significant preventive measures. Although a widespread custom, controversy exists regarding the efficacy of a preload; for certain categories of patients intravenous volume loading may be deleterious, and rather than a routine measure, the decision to administer a preload should be based on the clinical situation and the condition of the individual patient. For the treatment of mild bradycardia, anticholinergic drugs are the first choice. Hypotension may be treated by promoting venous return using gravity, by intravenous fluid infusion, by intravenous administration of sympathomimetic drugs, or by a combination of all three measures. In the event of sudden circulatory collapse, the first therapeutic measure that is usually immediately effective is elevation of the legs, thus promoting venous return.