Incidence of oxygen desaturation with intravenous ketamine and the effects of the basic airway management maneuvers on it

Introduction : This study was conducted to evaluate and compare the incidence of oxygen desaturation during intrave - nous ketamine for short surgical procedure and the effects of basic airway management maneuvers during desatura - tion. Methods : A Population based comparative study was done at two different hospitals situated in hilly regions of Nepal. Children aged between 3 months and 14 years were observed for their oxygen saturation with the help of Pulse Oxyme - ter during intravenous ketamine anesthesia for short surgical procedures lasting less than 15 minutes. Results : Seventy nine patients from United Mission Hospital (UMN), Tansen and 66 patients from Okhaldhunga Com - munity Hospital (OCH), Okhadhunga were enrolled; the incidence of desaturation was 8(10%) and 11(16.1%) in Tansen and Okhaldhunga respectively. 7(87.5%) and 8(72.7%) of the patients with desaturation from UMH and OCH respec - tively, were improved to >90% with chin lift only and rest needed jaw thrust. Conclusion : The incidence of oxygen desaturation is common within first few minutes of ketamine administration. Ba - sic airway measures like chin lift and jaw thrust is enough to improve oxygen saturation.


INTRODUCTION
Nepal is a mountainous country, and almost half of the population resides within the range of 600-4500 meter altitude. 1 High altitude is obviously associated with low barometric pressure and low oxygen partial pressure.
Ketamine is widely used throughout the world especially in precarious condition, like battlefield 2 , disaster, prehospital trauma victims 3,4 , where resources are minimal.
Provision of oxygen is usually considered mandatory in any anesthetized patients. But oxygen supply to remote areas of Nepal is difficult due to various reasons like cost factor, infrequent supply and lack of transportation. These are the factors that limit the use of ketamine in the rural hospitals of hilly areas of Nepal. Small case series done at 3900m altitude from Nepal 5 showed that supplemental oxygen was not required in healthy acclimatized patients.
Similarly Pesonan also used ketamine successfully without any supplemental oxygen at an altitude of 6000ft for short procedures. 6 Tansen is situated at 1361 m western part and Okhaldhunga is situated at 1800 m above sea level, eastern part of Nepal. 7,8 The concept of basic airway management maneuvers like chin lift, jaw thrust , physical stimulation and oro-pharyngeal suction has been documented only in few papers discretely 6,9 , but whether these maneuvers are really effective when solely applied in a systematic way, is still not answered. This study will evaluate the incidence and magnitude of oxygen saturation changes with intravenous ketamine for short surgical procedure lasting less than 15 minutes and will try to answer the effectiveness of different basic airway maneuvers to correct desaturation in the children population residing in hilly areas of Nepal.

This comparative study was done at Tansen Mission
Hospital, 165 bed hospital situated at an altitude of 1361 meter located in western part of Nepal, and at Okhaldhunga Community Hospital, Okhaldhunga, 32 bed hospital situated at an altitude of 1800 meter located in eastern Nepal. The study was conducted from May 2007 to October 2007. Children age between 3 months to 14 years or less undergoing short surgical procedures with intravenous ketamine anesthesia were included. Patients were excluded if premedicated or supplemented with medicines other than intravenous antibiotics; procedures lasted more than 15 minutes, patients having pre-existing heart or lung disease, oxygen saturation less than <90% before intravenous ketamine administration.
After administration of ketamine (at 2 mg/kg) SpO2 was recorded at every 2 minute interval throughout the procedure and full recovery. Maintenance dose of intravenous ketamine were given at a dose of 0.5-1 mg/ kg if necessary.
Patient breathed room air throughout the procedure and recovery. Manual basic airway procedure like chin lift, jaw thrust, oro-pharyngeal suction and physical stimulation were used, in those whose oxygen saturation drops below 90%, one after another for 15 seconds for each maneuvers.
Physical stimulation was used when desaturation was associated with slow breathing or apnea. Oropharyngeal suction was used when desaturation was associated with increase oropharyngeal secretions. Supplemental oxygen was used only after 1 minute when all the maneuvers failed to improve initial oxygen desaturation with the help of mask in order to restore SpO 2 above 90%. Patients needing any of the maneuvers or supplemental oxygen were recorded by Principal Investigator.
Ethical clearance from Nepal Health Research Council was obtained for the study.

DISCUSSION
This study has demonstrated that the incidence of desaturation with intravenous ketamine is common and simple basic measures if done in a systematic way can correct these problems. The incidence of oxygen desaturation was recorded to be 10.12% in Tansen and 16.66% in Okhaldhunga, consistent with the findings of Goor, and Joly, 10% and 18% respectively. 10,11 The lowest

ORIGINAL ARTICLES
Incidence of oxygen desaturation with intravenous ketamine and the effects of the basic airway management maneuvers on it     The onset and duration of falls in oxygen saturation are likely to be related to the pharmacokinetics of ketamine, which peak plasma concentration is within 1 minute of IV administration. As documented by Joly 11 desaturation may be partly related to airway obstruction but also to central ventilator depression which is more pronounced when ketamine is used as bolus, desaturation is less severe and less frequent in children than in adult. We found no desaturation during recovery period.
We found that chin lift maneuvers is very much effective in correcting oxygen desaturation and jaw thrust maneuvers as second effective measure. Jaw thrust has been tried successfully for restoration of airway malalignment during desaturation. There were some oral salivary secretion noted in 2 (3.3%) patient during procedure at Okhaldhunga and in 2 (2.5%) patient during recovery at Tansen, similar with general incidence of 1.7% 4 , but they were not significant to cause airway obstruction as there was no desaturation. This finding support that the routine use of anti-sialogague in children during ketamine anesthesia for short surgical procedure is un-necessary and further stresses the importance of basic airway management. We found none of our patient had apnoea. Literatures have shown that incidence of laryngospasm is less than 1% in children and apnoea is exceptionally rare. 3 The limitations of this study were that the statistical calculation for sample size was not done before the study, no blinding was possible and only children were included, so whether the findings is relevant for adults is still questionable.