LETTER TO THE EDITOR
Year : 2015 | Volume
: 5 | Issue : 1 | Page : 39--40
Accidental subdural placement of labor epidural catheter leading to sudden maternal collapse
Nitu Puthenveettil, Rajan Sunil, Paul Jerry, Kumar Lakshmi
Department of Anaesthesia and Critical Care, Amrita Institute of Medical Sciences and Research Centre, Kochi, Kerala, India
Dr. Nitu Puthenveettil
Department of Anaesthesia and Critical Care, Amrita Institute of Medical Sciences and Research Centre, Kochi, Kerala
|How to cite this article:|
Puthenveettil N, Sunil R, Jerry P, Lakshmi K. Accidental subdural placement of labor epidural catheter leading to sudden maternal collapse.J Obstet Anaesth Crit Care 2015;5:39-40
|How to cite this URL:|
Puthenveettil N, Sunil R, Jerry P, Lakshmi K. Accidental subdural placement of labor epidural catheter leading to sudden maternal collapse. J Obstet Anaesth Crit Care [serial online] 2015 [cited 2020 Nov 24 ];5:39-40
Available from: https://www.joacc.com/text.asp?2015/5/1/39/155201
A 26-year-old primigravida (American Society of Anesthesiologists I) with 39 weeks gestation was admitted for safe confinement. Labor was induced with artificial rupture of membranes, followed by oxytocin infusion. When the patient was in active labor, labor analgesia was initiated following insertion of an epidural catheter at L3-L4 space. Correct epidural placement was confirmed by negative aspiration for blood and cerebrospinal fluid (CSF). Local anesthetic with adrenaline test dose was avoided. A bolus of 15 ml of 0.1% ropivacaine with fentanyl 20 micrograms was given. Patient had adequate analgesia and vitals remained stable.
Fifteen minutes later foetal bradycardia (58/min) was detected, and the patient became unresponsive. Maternal blood pressure was 110/60 mmHg; SaO 2 was 100%. Soon the patient developed labored breathing, followed by apnea and desaturated. Ventilation was initiated with Ambu-Bag and patient was intubated. Saturation picked up to 100% immediately.
Due to suspicion of amniotic fluid embolism patient was shifted to the operation theatre for emergency lower segment cesarean section. Arterial blood gas showed normal values. Active baby was delivered (Apgar score 8/10). Anesthesia was maintained on oxygen, air and isoflurane (1-1.2%) with 100 microgram fentanyl. Patient remained hemodynamically stable intraoperatively and was ventilated postoperatively. After an hour patient became fully awake and was extubated. Neurological examination revealed no neurological deficit.
Subdural space has its origin within the dura-arachnoid interface  which act as a single unit, but may be pulled apart by placement of catheters, generating a potential space.  It ends in the lower body of the second sacral vertebra and is widest at the cervical area and narrowest in the lumbar area.
The dura and the arachnoid matter are closely attached at the ventral root. Hence, subdural injections pool in the posterior segment sparing the anterior nerve roots. Therefore, subdural blocks are characterized by sparing of sympathetic and motor functions. Though the onset of the sensory block is usually slow and appears disproportionate to the volume of drug injected, it lasts for several hours. The sympathetic and motor functions are usually spared or only minimally affected.
In our case, amniotic fluid embolism was ruled out as oxygen saturation picked up rapidly with normal arterial blood gases and patient was stable hemodynamically. Subarachnoid injection was ruled out by negative aspiration of CSF and absence of motor block.
Subdural injection was suspected as there was delayed onset of symptoms with stable hemodynamics. Cause of apnea could be due to cervical or intracranial spread of local anesthetic. We failed to document extensive sensory block as patient was unresponsive. However the lack of sympathetic response to surgery, even before opioid administration, suggests presence of extensive sensory block. The definitive diagnosis of subdural block could be obtained by injecting a contrast dye through the catheter and radiological confirmation, but no therapeutic benefit could be obtained. Hence the diagnosis is mainly made clinically.
Subdural injection during labor analgesia is a rare, but usually undiagnosed condition.  Unexplained clinical signs which do not fit subarachnoid or intravascular block during epidural anesthesia, should arouse a high degree of suspicion of unintentional subdural block. 
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