Persistent Intraoperative Hypoxemia in the right lateral decubitus position: a case report.

DOI: https://doi.org/10.21203/rs.3.rs-2395711/v1

Abstract

Background

Platypnea-orthodeoxia syndrome is an extremely rare syndrome. Platypnea-orthodeoxia syndrome is a group of diseases characterized by hypoxemia and dyspnea in the upright position and improvement in the supine position. In this case, severe hypoxemia occurred in the intraoperative right lateral decubitus position and was suspected to be associated with Platypnea-orthodeoxia syndrome.

Case Presentation

An 85-year-old woman underwent surgery for a fracture of the left femoral neck. After the right lateral decubitus position, the patient presented with sustained low oxygen saturation and normal blood pressure which was maintained at the range of  180mmhg- 150mmhg/90-52mmhg lasting 45 minutes. Subsequently, arterial blood pressure and heart rate decreased. The patient was immediately placed in a supine position. In the supine position, all vital signs were back to normal.

Conclusion

This case may be a clinical manifestation of a specific POS syndrome, which provides a new differential diagnosis for intraoperative posture-related hypoxemia. Severe hypoxemia due to intraoperative position changes can be highly suspected as POS.

Background:

POS is a rare syndrome presenting with dyspnea and cyanosis induced by an upright position and relieved by recumbency[1]. Patent foramen ovale(PFO) is the most common cause of POS. Nevertheless, the patients with PFO developed persistent hypoxemia while in the right lateral decubitus position which is very infrequent.

As far as we know, previous cases were diagnosed and treated by clinical manifestations of upright hypoxia and imaging. Prolonged bed rest poses a significant preoperative diagnostic challenge. As well, severe intraoperative posture-related hypoxemia poses a serious diagnostic and therapeutic challenge.

We report a case of persistent intraoperative hypoxia in a patient with combined PFO, right deviation of the mediastinum, abnormal liver location, and aortic root dilatation. Written informed consent was obtained from the patient for the publication of this case report.

Case Presentation:

An 85-year-old woman prepared for surgery to treat a left femoral neck fracture caused by a fall. Her previous medical history included hypertension, Meniere’s syndrome, lumbar disc herniation, cirrhosis of the liver, kidney stones, and renal cysts. Physical examination revealed her height was 145cm, her weight was 40kg, her blood pressure was 159/59 mm Hg, her breath rate was 18 per minute, and her heart rate 60 per minute; The slightly coarse breath sounds were heard in both lungs. Preoperative laboratory tests showed no significant abnormalities. A general chest Computed Tomography (CT) confirmed inflammation of both lungs, with the lower lobes of both lungs being the focus. As well, it also confirmed the right deviation of the mediastinum. Transthoracic echocardiography revealed an enlarged left heart(Left ventricle LV 51 Left Atrium LA43); Thickening of the basal segment of the ventricular septum(interventricular septum IVS = 9–12); Aortic valve regurgitation(moderate VC = 5.6mm); Mitral regurgitation(mildly); Decreased diastolic function(E/e'=18). The patient suffered a fracture of the left femoral neck and was ready to perform a left-sided double-action artificial femoral head replacement.

The patient was admitted to the operating room with an oxygen saturation of 92% on air, and breath sounds in both lungs were symmetrical but slightly coarse. Arterial blood gases showed a partial pressure of oxygen of 68 mmHg and PCO2 of 37 mmHg after invasive arterial blood pressure monitoring. During induction of anesthesia, 0.15 mg/kg cis-atracurium, 0.4 µg/kg sufentanil, and 0.2 mg/kg etomidate injection were administered. After successful intubation, the tidal volume of mechanical ventilation was 7 ml/kg, the airway pressure was 15 mmHg, the oxygen concentration was 50%, and no significant abnormalities were observed in the vital signs. After the right lateral decubitus position, the patient presented with sustained low oxygen saturation and normal arterial blood pressure which lasted up to 45 minutes. Arterial blood gas analysis suggested PO2 was 55.1mmHg, and SPO2 was sustained at the range of 82%-92%. In the meanwhile, adjustment of oxygen concentration to 100%, intravenous hydrocortisone infusion and changed to manual high-frequency ventilation were noneffective. During this period, systolic blood pressure was in the range of 123 to 153 mmHg and diastolic blood pressure was in the range of 70 to 80 mmHg. However, it was effective to use ephedrine to raise the level of higher blood pressure which could elevate oxygen saturation. Suddenly, heart rate, oxygen saturation, and blood pressure decreased, the surgery was stopped immediately and the body position was changed to the supine position. The above management measures resulted in the patient's oxygen saturation rising to 100% and other vital signs returning to normal. TEE was checked in detail. (Fig. 1). TEE suggested the presence of a large PFO and a left-to-right shunt in the supine position. At this point, the patient needed to close the wound, so the patient was tilted 30° to the right, and oxygen saturation remained at 100%. TEE suggested a small amount of right-to-left shunting in the PFO (Fig. 2). In the right lateral decubitus position, the patient's oxygenation could not be maintained, so TEE was not performed.

When the patient was conscious, the tracheal tube was removed in the operating room. And arterial blood gas indicated PO2 49.9mmHg. When the patient was in the upright position in the general ward, the patient developed significant shortness of breath and no significant respiratory distress in the supine position. The patient was discharged from the hospital after 35 days.

Discussion And Conclusion

POS is a syndrome of hypoxia accompanied by postural changes. POS has no clear diagnostic criteria. Based on the literature review, possible criteria include :(1) decreased noninvasive oxygen saturation in the upright position and recovered in the supine position[1];(2) Arterial PO2 was significantly lower in the upright position compared to the supine position[2]

However, cases of decreased oxygen saturation in the lateral recumbent position had also been reported and very few cases of intraoperative lateral hypoxia had been reported. In the present case, there was insufficient evidence of hypoxia in the upright position, but the mechanism of lateral recumbent hypoxia was consistent with POS. We discuss the pathophysiology of this case in terms of POS pathophysiology.

The possible pathophysiological causes are intracardiac shunt (PFO, ASD, or atrial septal aneurysm(ASA) with fenestration), pulmonary diseases with ventilation/perfusion mismatch(High V/Q ratio, and low V/Q ratio[3].

Additionally, the possible pathophysiological cause is the right-to-left shunt due to PFO in the right lateral position. Due to the low diagnostic sensitivity of TTE for PFO as well as shunts, the prevalence of PFO observed by TTE contrast was reported to be lower than that observed by TEE (14.9% vs. 24.3%)[4]. This could explain the failure of preoperative TTE to detect PFO.

Factors without pulmonary hypertension that the right-to-left shunt include:(1) During positive pressure ventilation in the right lateral position, Intrathoracic positive pressure results in right heart compression, increased right atrial pressure, and appeared right-to-left shunt. Possible causes of right heart compression are short stature, diaphragm elevation, liver compression, and positive pressure ventilation. From the CT mediastinal window, we can see the smaller right atrium and the compression of the right atrium by the liver(Fig. 3). As well, the right deviation of the mediastinum was observed. (Fig. 4) (2) Dilation of the aortic root may lead to a leftward shift of the interatrial septum, which may widen the gap in the PFO as well as provide for increased right atrial pressure, thereby increasing the right-to-left shunt[5]. We can see the dilated aortic root from the intraoperative TEE examination as well as the mediastinal window of the chest CT.

In the absence of pulmonary hypertension, PFO causes a left-to-right shunt due to higher left heart pressure than the right heart. In right de-cubitus, the liver was in full contact with the right atrium resulting which increased right heart pressure. The patient had no previous history of liver disease, but on CT the liver was found to be in close apposition to the right atrium, which may be associated with the right diaphragm elevation. A few case studies reported POS with hemidiaphragmatic elevation, especially triggered by hemidiaphragmatic paralysis[6]. After the onset of muscle relaxants, the patient's diaphragm was relaxed and the postural pad elevated the relaxed diaphragm in the right lateral position. This may be the cause of diaphragm elevation in this case. Likewise, the above was aggravated by the rightward deviation of the mediastinum and aortic root dilation. In addition, smaller right atria were more likely to be compressed. These are why right heart pressure increases in the right lateral decubitus position and a right-to-left shunt occurs.

The strange phenomenon of reduced oxygen saturation but normal blood pressure occurred intraoperatively. This may be because a large amount of unoxygenated blood flow reached the left heart directly through the PFO, and the normal output of the left heart ensured normal blood pressure. After 45 minutes, prolonged hypoxia resulted in decreased cardiac pump function, decreased cardiac output, and a rapid drop in blood pressure.

During the patient's hypoxia, we tried to raise the blood pressure to a higher level using ephedrine, and oxygen saturation was briefly improved. Ephedrine has an α agonist effect, the pharmacological effect that causes pulmonary vasoconstriction and reduces intrapulmonary shunts as well as temporarily increasing left atrial pressure and reducing intracardiac right-to-left shunts. Successful reversal of right-to-left shunt to improve oxygen saturation has been reported in an elderly patient with POS using 5 µg/hr norepinephrine[7].

However, intracardiac shunts can only be resolved by PFO closure. PFO closure was rejected due to the patient's advanced age and good post-operative recovery.

In conclusion, PFO-related POS syndrome should be highly suspected in posture-related hypoxia.

Abbreviations

POS: Platypnea-orthodeoxia; PFO: Patent foramen ovaleTEE: Transesophageal Echocardiography

TTE: Trans-thoracic echocardiographyCT: chest computed tomography; ASA: atrial septal aneurysm; LV: Left ventricleLA: Left Atrium; IVS: interventricular septum.

Declarations

Acknowledgments

None

Authors’ contributions

Wu G.W collected all the patient initial data and drafted the manuscript; Song H.B completed the TEE examination and processed images. Wu G.W and Xu H.W completed the anesthesia management; All authors read and approved the final manuscript.

Funding

This case report was not funded by any funding.

Availability of data and materials

The datasets are available from the corresponding author on request.

Ethics approval and consent to participate

All clinical practices were conducted by the principles of the Declaration of Helsinki.

Consent for publication

Written informed consent was obtained from the patient for publication of this article and any accompanying images.

Competing interests

The authors declared that they have no competing interests.

Author details

Department of Anesthesiology, West China Hospital, Sichuan University, No. 20, Sect. 3 South Renmin Rd., Chengdu, Sichuan 610041, PR China.

References

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