Delayed Reversal - Hypothermia despite Caution in a Case of Pediatric Robotic Pyeloplasty

A seven year old male child was posted for robotic pyeloplasty.  Patient was pre-medicated with midazolam, fentanyl and glycopyrrolate, induced with propofol and maintained on low flow (1L/min) nitrous oxide, oxygen, sevoflurane (2%) with Volume Control Ventilation (VCV). Pneumoperitoneum was created and maintained below 12mm Hg pressure. Patient was positioned in left lateral and steep trendelenburg position (almost 60-70 degrees after the surgeons conveyed difficulty in access with 40-50 degrees inclination). Soon, there was an increasing trend in the End Tidal Carbon Dioxide (EtCO2) to 45-55 mmHg. Ventilator settings were changed by increasing tidal volume (from 6ml/kg to 8ml/kg) and respiratory rate but it did not help much (EtCO2 still in range of 50-55mmHg). Peak Inspiratory Pressure (PIP) and plateau pressure rose to 32mm Hg and 28mm Hg respectively. This prompted us to shift the patient on Pressure-Controlled Ventilation (PCV) with lung protective strategy (Pmax -25mmHg) allowing a larger tidal volume for the same inspired pressure with EtCO2 coming down in the range of 40-45mmHg. Paracetamol injection was given for supplementing analgesia. At the end of surgery, port sites were infiltrated with 0.25% Bupivacaine and caudal anesthesia was given. Total duration of procedure was nearly 4.5hrs. At the time of reversal, patient was not taking spontaneous breaths despite 1 hour of the last dose of relaxant and no signs of hypercapnia (EtCO2 within 35-40mm Hg). All possible causes for delayed reversal were ruled out and axillary temperature recorded 36 degree Celsius. We continued to electively ventilate the child and resorted to actively warm the patient suspecting hypothermia being the culprit behind delayed awakening. Finally, after about 30 min of active efforts, patient was successfully extubated and shifted to post anesthesia care unit.

Robotic surgeries have gained popularity and anesthesiologist should be prepared to tackle fresh challenges associated with proper patient selection and screening along with intraoperative care challenges [1]. The most common complications related with pediatric robotic surgeries include peripheral neuropathies, oedema (airway, cerebral and ocular), vascular complications including compartment syndrome, rhabdomyolysis and thromboembolism; cardiovascular complications like hypotension, hypertension and arrhythmias can also occur. The major pulmonary complications include pneumothorax, bronchospasm, endotracheal intubation, hypoxia, hypercarbia and atelectasis [2,3]. The trendelenburg position for prolonged periods can cause pooling of secretions that necessitates administration of anti-sialagogues like glycopyrrolate with added benefit of preventing vasovagal reflexes. The pressure of pnemoperitoneum in children should be kept between 6-12cm H₂O, flow of gas about 0.9L [4]. An increase in EtCO2, peak inspiratory pressure and plateau pressure can cause hypercarbia and acidosis requiring prolonged mechanical ventilation. In response to hypercapnia, we shifted to PCV to deliver the desired tidal volume as it allows lower peak airway pressure and plateau pressure with higher lung compliance. PCV rather than VCV, application of PEEP, recruitment maneuver and prolonged Inspiratory-Expiratory (I:E) ratio might improve respiratory mechanics during robotic laparoscopic surgery [5]. Moreover, the steep angle used for trendelenburg position in our case could have been a major determinant in the respiratory changes. Therefore, adherence to a lower allowable angle for the position could help in preventing the substantial cardiorespiratory compromise. We also observed delayed reversal in our patient. The various possible causes for delayed reversal include hypoglycemia, hypoxia, hypercapnia, hypothermia, acidosis, hypothyroidism, electrolyte disturbances, anesthetic overdose and toxins. In our case, we ruled out hypoglycemia (random blood glucose was 104mg/dl), hypoxia, hypercapnia and electrolyte disturbances or any drug overdose. Though, the intravenous (iv) and irrigation fluid used were warm and child was properly covered with warm sheets, the suspected cause could be the long duration of surgery resulting in prolonged exposure to cold and dry insufflating CO₂ used during laparoscopy leading to core hypothermia. Insufflation of cold (usually at 25 deg C), non-humidified CO₂ directly inside the abdominal cavity poses a risk of hypothermia. There are also studies supporting exaggeration of intra-operative hypothermia in head down position. Though the axillary temperature recorded 36 degrees Celsius, a greater discrepancy is expected between the axillary and core temperature. Hence, we would stress that when dealing with pediatric patients or surgeries demanding accurate temperature monitoring, due caution be paid to the relationship between the measured temperature and the core temperature. This can guide us in an accurate assessment and hence, efficient prevention of hypothermia. The preventive measures to avoid hypothermia include using warming mattress, heat humidifier, forced air warmers. The insufflating gas flows should be warmed and kept below 2 L/min. A Humigard device can be used to humidify and warm the gas to near body temperatures (37 deg C) [3].

Hence, there are various critical anesthetic concerns in robotic-assisted pediatric surgery, however with meticulous preparation, closeful watch of the functional correlations, active efforts and good communication, complications could be minimized to achieve improved patient outcomes.

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