Background
Epidural analgesia is commonly used to provide excellent pain relief with few complications [
1]. Although it has become a routine procedure, the complications that are associated with its use may be underestimated [
2]. Identification of the epidural space through loss of resistance to air is a widely applied technique during epidural catheter placement [
3]. However, several complications are associated with this method, including pneumocephalus [
3], subcutaneous emphysema [
4], venous air embolism [
5], and spinal cord and nerve root compression [
6]. Pneumorrhachis and pneumocephalus are rare complications of unintentional dural puncture and air injection into the subarachnoid or subdural space [
7]. To the best of our knowledge, no cases of cardiac arrest associated with these complications have been reported. In this report, we describe two cases of cardiac arrest associated with pneumorrhachis and pneumocephalus after epidural analgesia that originated from the use of air during loss-of-resistance placement technique.
Discussion and conclusions
We report two cases of pneumorrhachis and pneumocephalus in patients who previously underwent epidural analgesia. Thereafter, they presented to the ED with cardiac arrest. To the best of our knowledge, no cases of cardiac arrest associated with these complications have been reported previously.
Pneumorrhachis is a phenomenon characterized by intraspinal air mostly due to traumatic and iatrogenic etiologies [
8]. Various conditions may cause pneumorrhachis, including iatrogenic manipulations during interventions and lumbar puncture [
9]. The diagnostic tool of choice for the detection of pneumorrhachis is CT [
10]. Pneumorrhachis is usually asymptomatic and reabsorbs spontaneously and completely the air that passed directly into the blood for several days without recurrence [
11]. Therefore, patients with pneumorrhachis are commonly managed conservatively.
The symptoms of pneumocephalus, such as headache, elevated intracranial pressure, vomiting, convulsions, and unstable vital signs, depend on the intracranial air distribution and amount [
12]. Less than 2 ml of subarachnoid air can cause headache [
13]. However, the air volume that can safely be injected into the epidural space remains to be established [
14], and the correlation between the intracranial air amount and headache is unclear [
13].
The entrapped air occupies parts of the cerebrospinal compartment, which may cause both intracranial and intraspinal hypertension and hypotension secondary to either increase or decrease in intracranial and intraspinal pressure [
8]. The injected air can also act as a space-occupying lesion and exert pressure on the nervous structures within the spinal canal. Hence, entrapped intraspinal air might cause tension pneumorrhachis and pneumocephalus with nervous tissue compression [
15]. These mechanisms may lead to cardiac arrest. Therefore, recognizing the differential diagnosis of altered intraspinal pressure within the cerebrospinal compartment is important to ensuring its adequate management.
There are some limitations to these conclusions. There are other causes of cardiac arrest that were not thoroughly investigated in these cases. Electrocardiograms revealed sinus tachycardia, and the cardiac troponin levels were not elevated in these cases of cardiac arrest. Furthermore, the echocardiograms of the patients displayed no regional wall motion abnormality. However, the exclusion of cardiac causes had not been achieved through coronary angiography. Additionally, anaphylactic shock due to the injected anesthetic drug may have resulted in cardiac arrest. However, we believe that fatal anaphylaxis may be distinguished from pneumorrhachis in that the former can occur within minutes of drug injection compared with the latter. The possibility of total spinal anesthesia following epidural analgesia also needs to be ruled out. Total spinal anesthesia causes sudden physiological changes by blocking the peripheral nerves, including the spinal cord and cranial nerve [
16]. Because both patients came from local pain clinics, there was insufficient information to investigate this possibility; including the patients’ position, location of injection, type or size of needle, and number of attempts. Thus, it is difficult to further clarify the association between total spinal anesthesia and cardiac arrest. In some case reports, pneumorrhachis or pneumocephalus developed after basic life support, and this possibility cannot be excluded [
17].
No empiric treatment guidelines or standards of care exist for pneumorrhachis, owing to its rareness and different pathogenesis and etiologies. Pneumorrhachis is thought to be associated with increased morbidity and mortality [
8]. In this report, we present cases of pneumorrhachis and pneumocephalus in two women who presented to the ED with cardiac arrest after epidural analgesia. If cardiac arrest occurs after epidural analgesia, pneumocephalus and pneumorrhachis should be suspected as its cause. The contributing factors for pneumorrhachis and pneumocephalus have to be evaluated, and appropriate interventions should be implemented. Patients with severe and life-threatening conditions that can lead to pneumorrhachis and pneumocephalus should be carefully monitored, followed, and considered for admission to an ICU. Care should be taken because patients may have a cardiac arrest after epidural analgesia.