Venous Air Embolism in an Awake Patient
Troy Cummens, MD and Dietrich Gravenstein, MD.
Department of Anesthesiology, University of Florida, Gainesville, Florida
Since FDA approval in 2002 implantation of deep brain stimulators (DBS)
is becoming an increasingly common surgical treatment for movement
disorders. Implantation involves functional mapping of relevant subcortical
structures by electrophysiological recordings followed by symptom-based
placement of the stimulating electrode. Typically no systemic sedative,
inhalational, anxiolytic, sympatholytic, or analgesic agents are utilized
during the procedure, because anesthetic agents alter intrinsic cellular
activity. This practice lures some anesthesiologists into thinking there is
“nothing to do” during this procedure. This report presents a complication
of DBS placement, its diagnosis and treatment.
The patient was a 76-year-old woman with a 10-year history of Parkinson’s
tremor. Her right sided tremors were controlled with a DBS that was placed
10 months prior. She was now scheduled for the same procedure on the
contralateral side. In preparation of the procedure, a stereotactic head
ring was placed under local anesthesia. The patient was taken to the OR and
placed in a recumbent position with her head fixed to the table via the head
ring. She was awake and alert. Vital signs remained stable with blood
pressure ranging from 135 - 150/55 - 62 mmHg, HR 68 - 72 min-1 and SpO2
remained at 100%. End tidal CO2, measured by nasal cannula, was 40, and her
respiratory rate was 13. About half an hour into the procedure, her end
tidal CO2 decreased precipitously from 40 to 13. The nurse at the bedside
reported the patient was shaking, possibly consistent with seizure activity.
The patient became confused, but remained capable of answering questions.
Her blood pressure decreased to 60/29 by noninvasive measurement. Over the
next three minutes, the patient’s SpO2 decreased from 100 to 82%, while she
became tachypneic at a rate of 25 breaths per minute. She was placed in
Trendelenburg position, given supplemental oxygen (4 L/min) via nasal cannula, and given a fluid bolus of intravenous crystalloid solution. She
reported a sensation of pressure in her chest, which was treated with a
single dose (400 mcg) of sublingual nitroglycerin. The only
electrocardiographic abnormality was a single premature ventricular
depolarization.
With these interventions, blood pressure normalized quickly and remained
stable throughout the case. SpO2 improved to the mid 90's over 3 minutes,
and returned to 100% within 10 minutes. EtCO2 improved gradually as her
respiratory rate normalized. Her chest pressure resolved, and her mental
status improved gradually. There were no further complications during the
procedure. No definitive diagnostic tests were done to determine the cause
of the symptoms.
Acute complications described for DBS placement include intracranial
hemorrhage, seizures, stimulation-induced dyskinesia, improper lead
placement, and pulmonary embolism. We believe the patient experienced a
venous air embolism introduced into the superior sagittal sinus as the
surgeon entered the dura. The surgeons confirmed that a small amount of
blood did come from the sinus through a small tear immediately prior to the
symptoms, which was controlled with two sutures and some gelfoam. The
incidence of venous air embolism in this relatively new procedure is not
known. However, this is not the first incidence seen in our institution.
Other instances presented with subtle symptoms not seen in this patient,
such as hiccough or cough. The case illustrates the need for vigilant
monitoring for complications and prompt intervention to prevent bad
outcomes.
