Background Hypercapnia while under general anesthesia can be due to many causes including hypoventilation, rebreathing, increased CO2 production,and increased dead space. Increased CO2 production is frequently encountered... [ view full abstract ]
Background
Hypercapnia while under general anesthesia can be due to many causes including hypoventilation, rebreathing, increased CO2 production,and increased dead space. Increased CO2 production is frequently encountered inhypermetabolic states such as malignant hyperthermia, isolated hyperthermia,thyroid storm, and pheochromocytoma. In an otherwise healthy patient with noprior exposure to anesthesia, the concern for malignant hyperthermia and its associated rapid deterioration is of increased concern, with the incidence ofMH in pediatric patients 1:30,000.
Case Description
A 6 year old, otherwise healthy, 17kg male, presented for emergent lower extremity open reduction and internal fixation. After an uneventful induction and oral endotracheal tube placement, he was managed with volume control ventilation using an adult circuit. As the case went on, there was a noticeable uptrend of EtCO2 as seen in the graph below refractory to all basic ventilation changes. The patient otherwise remained hemodynamically stable, normothermic, normotensive, with expected heart rate fluctuations based on sympathetic stimulation. Inhalational anesthetics were discontinued for fear of early malignant hyperthermia, and manual ventilation was begun using an Ambubag. ABG was consistent with respiratory acidosis, with no signs of metabolic or electrolyte abnormalities. The remaining portion of the case was managed with manual ventilation and total IV anesthesia during which the patient remained hemodynamically stable and resolution of hypercarbia. Given the patient remained hemodynamically stable, and the combination of anesthetic management alterations led to the resolution of hypercapnia, the treatment for malignant hyperthermia was not begun. At the end of the case, patient was transported to PICU, intubated, for close monitoring given hypercarbia. The MH hotline was contacted and per their recommendations, CK’s were drawn for 24 hours postoperatively and the patient was closely monitored in the ICU. Later that evening, the patient was extubated by the PICU team and remained hemodynamically stable thereafter until discharge.
Discussion
In an otherwise healthy patient, increased dead space from obstructive processes were deemed unlikely. While hypermetabolic causes were of grave concern, normal vital signs combined with intraoperative blood gas monitoring decreased our concern for malignant hyperthermia. Based on patient's age and weight and normal airway pressures, hypercarbia was unlikely caused by adult circuit use. Lastly, given improvement in hypercarbia with manual ambubag ventilation, machine induced ventilator insufficiency was deemed most likely the cause of hypercapnea in this patient.
