Keywords
awake cranioplasty - rheumatic heart disease - severe mitral stenosis - transverse
abdominis plane block
Introduction
Decompressive craniectomy is done to manage intractable rise in intracranial pressures
following brain injuries and sometimes following evacuation of high-risk tumors or
following aneurysm surgeries. Cranioplasty, done following normalization of intracranial
pressures, improves cerebral hemodynamics, prevents hydrocephalus, trephined syndrome,
and problems associated with hemispheric collapse.[1]
[2]
Maintaining normal patient hemodynamics during conduct of anesthesia, for cranioplasty,
in patients with cardiac pathology can be extremely challenging. We report the anesthetic
management of one such high-risk cardiac case posted for cranioplasty.
Case Report
A 36-year-old female (height 156 cm, weight 60 kg, body mass index = 24.6 kg/m2), was admitted for cranioplasty, following previous decompressive hemicraniectomy
for left anterior and middle cerebral artery infarction, done under general anesthesia.
The intraoperative course was uneventful. Postoperatively, patient was electively
ventilated, eventually weaned off, and discharged with a Glasgow Coma Scale score
of E4VaphasicM6.
She was a known case of rheumatic heart disease (RHD) with severe mitral stenosis
(MS), on medication, with rate-controlled (heart rate 70–80 beats/min) atrial fibrillation
(AF) and right-sided hemiparesis. Chest radiograph showed left atrial enlargement
and left heart border straightening. A noncontrast computed tomography (NCCT) scan
head revealed skull defect in the left fronto-temporo-parietal region. Preoperative
echocardiogram showed mitral valve area of 0.9 cm2 and 21/12 mm Hg gradient across the valve, suggesting severe MS. Pulmonary artery
(PA) pressure was 36 mm Hg and left atrial clots were absent. Patient was on tablet
amiodarone 20 mg twice daily, digoxin 0.125 mg once daily for 5 days a week, diltiazem
30mg three times a day, and warfarin 2 mg once daily. Tablet warfarin was stopped
1 week prior to the surgery, and low molecular weight heparin (enoxaparin) 0.6 mL
subcutaneously twice daily, was started for bridging anticoagulation, which was discontinued
24 hours before surgery. Tablet amiodarone, digoxin, and diltiazem were continued
in the perioperative period. Prior to the surgery, patient was counseled and asked
to communicate in sign language in case she experienced any pain following the block.
Regional anesthesia (RA) was planned, including scalp block for cranioplasty and oblique
transverse abdominis plane (TAP) block for abdominal bone retrieval. In accordance
with the patient's comorbidities, appropriate emergency drugs and equipment were kept
ready in the operation theater. Preoperatively, she had a heart rate of 70 to 80 beats/min,
blood pressure (BP) of 128/74 mm Hg, and room air saturation of 98%. She was administered
oxygen at FiO2 0.6 and EtCO2 line was placed in situ. Left radial arterial cannulation was done for invasive BP
monitoring. Intravenous dexmedetomidine infusion was started (loading dose of 1 mcg/kg
for 10 minutes, followed by 0.4–0.8 mcg/kg/h infusion), titrated to desired sedation
and analgesia. Scalp block was administered unilaterally (landmark-guided) using 20 mL
local anesthetic (LA) (10 mL of 2% lignocaine + adrenaline [1:200,000] and 10 mL of
0.25% bupivacaine) for blocking supraorbital, supratrochlear, zygomaticotemporal,
auriculotemporal, greater occipital, and lesser occipital nerves. Since we expected
dura mater to be adherent to the scalp in the defect area, shorter length needle (24G)
was used for block administration and LA was injected slowly after repeated aspirations
by a well-experienced anesthesiologist. For bone-flap retrieval, ultrasound-guided
oblique TAP block was given unilaterally, using 10 mL of 2% lignocaine + adrenaline
(1:200,000) and 10 mL of 0.25% bupivacaine. Intraoperative course, of approximately
120 minutes, was uneventful. Postoperatively, the patient received oral tablet paracetamol
500 mg 6 hourly and was put on mechanical thromboprophylaxis (TED stockings). After
a postoperative NCCT scan, and 24 hours postsurgery, enoxaparin and warfarin were
resumed, with discontinuation of enoxaparin after 5 days. Patient was discharged on
the fifth postoperative day.
Discussion
Incidence of cardiac pathologies is 0.7% in 18 to 44 years age group.[3] Isolated MS is present in 25% patients with RHD, while 40% have both MS and regurgitation.[4] The American College of Cardiology/American Heart Association (ACC/AHA) guidelines
recommend that occurrence of severe valvular disease be considered a major clinical
predictor of cardiac risk. Further, brain surgery is considered to have high surgery-specific
cardiac risk (> 5%).[5] Perioperative strategy in these high-risk patients includes achievement of stable
hemodynamics, optimal preload and afterload, avoidance of hypoxia, hypercarbia, acidosis,
and hypothermia.[6]
Patients with severe MS need to undergo mitral valve replacement. Our patient was
advised the same, but she did not give consent due to financial constraints. Further,
she felt that RHD was not hampering her day-to-day activities. As per the current
ACC/AHA guidelines 2020, asymptomatic patients with moderate or greater degrees of
rheumatic MS with less than severe pulmonary hypertension (PA systolic pressure < 50 mm
Hg) can undergo elective noncardiac surgery.[7] Our patient was asymptomatic, with severe MS and PA systolic pressure of 36 mm Hg.
Hence she was posted for cranioplasty.
Though awake craniotomies are commonly done for mapping and resection of lesions in
vitally important brain areas where imaging is not very sensitive, however, previous
literature is deficient with regards to the use of RA in cranioplasty. RA is considered
a safe technique in cardiac patients as it avoids the hemodynamic alterations associated
with general anesthesia, need for airway manipulation with its inherent risks, and
use of opioids. It attenuates stress response and provides prolonged postoperative
analgesia. As the patient is awake following RA, the sympathetic tone remains intact
and rapid postoperative recovery ensures early neurologic status assessment.
It is important to be very careful while administering scalp block in such high-risk
patients. The inherent scalp defect in postcraniectomy patient may be associated with
altered bony landmarks, with the dura mater being adherent to the scalp. Scalp also
has a very rich nerve supply.[8] Thus, extreme caution must be exercised while giving scalp block, which should be
administered by a trained anesthesiologist. In addition, LA dose should be meticulously
calculated, not exceeding maximum safe limits. Previously, maximum volumes of 40 to
60 mL of lignocaine with adrenaline and bupivacaine have been used for giving this
block.[8]
For abdominal bone flap retrieval, we administered ultrasound-guided oblique TAP block,
wherein the drug is administered along the oblique subcostal line, in the plane above
the transverse abdominis muscle, starting from the xiphoid process, approaching the
anterior part of iliac crest ([Figs. 1] and [2]). This tends to block the thoracolumbar intercostal nerves originating from anterior
divisions of spinal nerves T6 to L1.[9]
Fig. 1 Linear probe placement parallel to the costal margin (CM, costal margin).
Fig. 2 Sonoanatomy for administering oblique transverse abdominis plane (TAP) block. Red
line: Plane of administering oblique TAP block. RM, rectus muscle; EO, external oblique;
TA, transverse abdominis.
Intraoperatively, patient was sedated using intravenous dexmedetomidine. Dexmedetomidine
preserves the respiratory drive, maintains target heart rate, provides analgesia,
decreases cerebral metabolic rate of oxygen, and prevents CO2 retention, thereby maintaining cerebral blood flow. Dexmedetomidine decreases opioid
dose and reduces new-onset postoperative AF.[10] It allows the conduct of neurological examination while maintaining smooth sedation
and analgesia within the targeted therapeutic window.[11]
[12]
To conclude, in high-risk neurosurgical patients, a meticulous preoperative evaluation
along with a good technique that balances the anesthetic requirements of both the
cardiac and neurologic disease helps in achieving a successful outcome. The conduct
of novel awake cranioplasty is advantageous in patients with challenging comorbidities.
