Case Report
A 15 year-old, 68 kg female with a history of idiopathic scoliosis was scheduled for thoracolumbar posterior fusion and instrumentation (levels T3-L4). Additional past medical and surgical history were unremarkable, without allergies or chronic medications. Induction of general anesthesia was achieved with intravenous lidocaine, Propofol, fentanyl, and succinylcholine. Following easy mask ventilation, the patient was intubated uneventfully via direct laryngoscopy with a 7.0 cuffed endotracheal tube. Total intravenous anesthesia (TIVA) with Propofol, remifentanil, and dexmedetomidine infusions was utilized for maintenance. Additionally, infusions of aminocaproic acid and nicardipine were employed for fibrinolysis and intermittent hypertension, respectively. The patient was turned to the prone position with no change in oxygenation or ventilation and all other vital signs were stable.
Ventilator settings included fraction of inspired oxygen (FiO2) 0.4, tidal volume (TV) 470cc, respiratory rate (RR) 11, and positive end expiratory pressure (PEEP) 5 cmH2O. Four hours post-induction, the first arterial blood gas (ABG) analysis showed 7.42/33/231/22/-3/99% with hemoglobin (Hgb)/hematocrit (Hct) = 8.5/25. Estimated blood loss (EBL) at that time was approximately 500cc. One hour later, the surgeon noticed cerebrospinal fluid in the operative field resulting from a dural tear at T2-T3. A pediatric neurosurgeon was consulted and a lumbar drain was placed at L2-L3. During this period, the patient became mildly hypotensive with a blood pressure (BP) of 93/53 mmHg, however oxygenation and ventilation remained stable. At this point, 1000cc of 5% albumin and 2500cc of crystalloid had been administered along with a transfusion of 60cc Cell Saver. Later on a second ABG analysis was obtained with normal results except for a low hematocrit: 7.43/37/218/24/0/99% with Hgb/Hct = 6.1/18. Two units packed red blood cells were transfused, the blood pressure stabilized, and the surgeon began closing. While still prone, the patient was transitioned to pressure support (PS) ventilation with settings of PS 14, PEEP 5, FiO2 0.4, RR 17-20, achieving tidal volumes of 350cc. The FiO2 was then increased to 1.0 in preparation for returning to supine position and emergence. All infusions were discontinued prior to turning supine, and acetaminophen 1000mg, hydromorphone 0.6mg, fentanyl 200mcg, were administered intravenously. Total fluids given for the case were 1000cc albumin 5% and 4000cc crystalloid, 60cc Cell Saver and 2 units packed red blood cells. Urine output was 3475cc with an EBL of 1000cc.
By the end of the case, the patient had been spontaneously ventilating with pressure support during wound closure for 30 minutes. The respiratory rate was 17-20 breaths/minute and TV 350-450cc. All vital signs were normal. Residual neuromuscular blockade was reversed, and the patient was turned supine. Immediately upon turning supine, her pulse oxymetry decreased to 65% with mild hypotension (BP 96/40) and a heart rate (HR) of 80. She became tachypneic (RR 30) with TV decreased to around 150cc. Respirations were supported with intermittent manual ventilation at an FiO2 of 1.0 over the next three minutes. This resulted in a slow, but steady increase in oxygenation to 89%. Over the next 5 minutes the oxygenation continued to rise slowly to 96%. Breath sounds were equal bilaterally without wheezing at the apices anteriorly, but were difficult to auscultate posteriorly. After 30 minutes, the patient was awake and appropriately following commands with unsupported TV of 250-275cc, RR 30, BP 121/53, HR 92, and oxygen saturation of 97%. The patient was extubated, after which, she immediately desaturated to 83% but was otherwise hemodynamically stable. Ventilation was assisted via bag-mask, but she remained tachypneic achieving poor TV (approximately 200cc) with good mask seal. A stat portable chest x-ray revealed a moderate right-sided pneumothorax. ABG analysis showed hypoxemia and respiratory acidosis 7.28/53/89/25/-2/96, Hgb/Hct=8.2/24. The patient was sedated in the operating room and the surgical team, under local anesthesia, placed a chest tube. The patient’s oxygenation immediately improved to 100%. She was then transported to the intensive care unit. The chest tube was removed on post-op day (POD)#1, her lumbar drain was removed POD#2, and the remainder of her hospital course proceeded uneventfully with discharge on POD#5. The patient and family were very satisfied with their care.