Background and Objectives: Postoperative cognitive disturbances (POCD) can significantly alter postoperative recovery. Inadequate intraoperative cerebral oxygen supply is one of the inciting causes of POCD. Near-infrared spectroscopy (NIRS) devices monitor cerebral oxygen saturation continuously and can help to guide intraoperative patient management. The aim of the study was to evaluate the applicability of the NIRS-based clinical algorithm during spinal neurosurgery and to find out whether it can influence postoperative cognitive performance. Materials and Methods: Thirty four patients scheduled for spinal neurosurgery were randomized into a study group (n = 23) and a control group (n = 11). We monitored regional cerebral oxygen saturation (rScO2) throughout surgery, using a NIRS device (INVOS 4100). If rScO2 dropped bilaterally or unilaterally by more than 20% from baseline values, or under an absolute value of 50%, the NIRS-based algorithm was initiated in the study group. In the control group, rScO2 was monitored blindly. To evaluate cognitive function, Montreal-Cognitive Assessment (MoCA) scale was used in both groups before and after the surgery. Results: In the study group, rScO2 dropped below the threshold in three patients and the NIRS-based algorithm was activated. Firstly, we verified correct positioning of the head; secondly, we increased mean systemic arterial pressure in the three patients by injecting repeated intravenous bolus doses of Ephedrine, ultimately resulting in an rScO2 increase above the approved threshold level. None of the three patients showed POCD. In the control group, one patient showed a drop in rScO2 of 34% from baseline and presented with a POCD. RScO2 drop occurred with other stable intraoperative measurements. Conclusions: A significant rScO2 drop may occur during spinal surgery in prone position despite other intraoperative measurements remaining stable, allowing it to stay otherwise unrecognized. Use of the NIRS-based clinical algorithm can help to avoid POCD in patients after spinal surgery.

Background: Near infrared spectroscopy (NIRS) devices are non-invasive and monitor cerebral oxygen saturation (rScO₂) continuously. NIRS interventional protocol is available in order to avoid hypoxic brain injury. Methods: We recruited patients scheduled for spinal surgery (n = 44). rScO₂ was monitored throughout the surgery using INVOS 4100 cerebral oximeter. If the rScO₂ values dropped more than 20% below baseline, or there was an absolute drop to below 50%, NIRS interventional protocol was followed. Results: In two patients rScO₂ decreased by more than 20% from baseline values. In one patient rScO₂ decreased to below 50%. NIRS protocol was initiated. As the first step, correct head position was verified–in one patient rScO₂ increased above the threshold value. In the two remaining patients, mean arterial pressure was raised by injecting Ephedrin boluses as the next step. rScO₂ raised above threshold. Patients with desaturation episodes had longer medium time of the operation (114 ± 35 versus 200 ± 98 min, p = 0.01). Pearson’s correlation showed a negative correlation between rScO₂ and duration of operation (r = −0.9, p = 0.2). Receiver operating characteristic curve analysis showed blood loss to be a strong predictor for possible cerebral desaturation (Area under the curve (AUC): 0.947, 95%CI: 0.836–1.000, p = 0.04). Conclusion: Patients with higher blood loss might experience cerebral desaturation more often than spinal surgery patients without significant blood loss.

Summary: Introduction. The adverse effects of hypoxia are well known, especially regarding the brain, and can lead to postoperative cognitive disturbances. On the other hand, the brain is still one of the least monitored organs intraoperatively. Near infrared spectroscopy devices are non-invasive continuous cerebral oxygenation monitoring devices that can also be used intraoperatively. Prone position used during spinal neurosurgery is of particular importance regarding physiological changes that can occur in the human body and can lead to reduced blood and oxygen supply of the brain. Aim of the Study. The aim of the study was to determine whether prone position used during spinal neurosurgery impacts cerebral oxygenation and patients’ cognitive performance after the surgery. Material and methods. 40 patients were included in the study (32 study group, 8 control group). Patients were scheduled for spinal neurosurgery in prone position. All patients received standard general anaesthesia. In the study group regional cerebral oxygen saturation (rScO₂) was continuously monitored using INVOS 4100 near infrared spectroscopy device. During the surgery every 5 minutes in study and control group medium non–invasive blood pressure, heart rate, peripheral oxygen saturation, exhaled CO₂ and cerebral oxygenation measurements were fixed. We also fixed intraoperative blood loss and duration of the operation. Cognitive function was assessed in both groups using Montreal - Cognitive Assessment (MoCA) scale before surgery and two days after the surgery. Results. We didn’t observe any significant changes in our calculated medium rScO₂ intraoperative values. During induction of anaesthesia when patients were lying supine rScO₂ above the right cerebral hemisphere was rScO₂ 72±9.7%, above the left cerebral hemisphere 71± 9.7%. Cerebral oxygen saturation in prone position was rScO₂ R 74±10.7% and rScO₂ L 74±10.1%. At the end of the surgery when patients were lying supine again rScO₂ R was 74±9.3% and rScO₂ L was 74±7.9%. We didn’t observe any differences in medium MoCA scores when comparing study and control group. MoCA score before surgery in the study group was 24.1±2.9 points and 24.6±4.1 points in the control group. MoCA performed 2 days after the surgery was 24.6 ±3.2 points in study group and 24.6±2.4 points in control group. Conclusions. No significant changes were observed in medium MoCA scores between patients who intraoperatively received noninvasive cerebral oxygen saturation monitoring and patients who did not receive it. Despite medium calculated MoCA scores, individually we observed postoperative cognitive function impairment for MoCA 1-2 points in 5 out of 8 patients in the control group, but in the study group only 1 patient out of 32 showed cognitive dysfunction. Intraoperative regional cerebral oxygen saturation monitoring can help to obviate cerebral desaturation that can lead to postoperative cognitive decline.

Uz infrasarkano staru spektroskopijas balstīta klīniskā algoritma izmantošana mugurkaula operācijās un pēcoperācijas kognitīvie traucējumi

In patients undergoing spinal surgery in prone position, physiological changes can occur in multiple organ systems. Pressure on pelvis, abdomen and thorax reduces systemic venous return, thereby decreasing cardiac output and increasing pressure in vertebral blood vessels, thus promoting intraoperative bleeding. Concomitantly, lung compliance decreases. The latter noxious factors hamper blood flow and oxygen delivery to the brain. The brain is highly dependent on adequate oxygen delivery, thus, tissue injury, and even cell death may occur already 5 minutes after cerebral ischemia. Postoperative cognitive decline is a potential complication, which may lead to long-term consequences. The exact aetiology and pathophysiology of postoperative cognitive disturbances is not known. Despite intraoperative cerebral ischemia could be a contributing factor to consider, the brain remains one of the least monitored organs intraoperatively. The aim of the present study was to evaluate the effect of the intraoperative use of a near-infrared spectroscopy-based clinical algorithm on outcome, especially on postoperative cognitive decline. We included 64 adult patients, scheduled for elective spinal neurosurgery in the prone position. All the patients underwent general anaesthesia and regional cerebral oxygen saturation (rScO2) was monitored intraoperatively by means of an INVOS 4100 cerebral oximeter. Patients were randomised into a study group and a control group. In patients of the study group, a near-infrared spectroscopy-based clinical algorithm was used to restore adequate cerebral oxygen saturation when noticing a drop of 20 % from preoperative baseline of cerebral oxygen saturation, or a fall in regional cerebral oxygen saturation below an absolute value of 50 %. In the control group, intraoperative cerebral oxygen saturation was monitored blindly without using the near-infrared spectroscopy-based clinical algorithm. In both groups, before and after the surgery, cognitive function was evaluated using Montreal Cognitive Assessment Scale (MOCA). Preoperative haemoglobin (Hb) and haematocrit (Hct) concentrations also were noticed, as well as intraoperative mean arterial pressure (MAP), expiratory end-tidal carbon dioxide (EtCO2) levels, peripheral oxygen saturation (SpO2), intraoperative blood loss and length of operation. In our study, in three patients – two in the study group and one in the control group, intraoperative cerebral desaturation was observed. Two study group patients were 54 and 57 years old. In one study group patient, cerebral saturation fell for 29 % from baseline values and also under an absolute value of 50 %; in the other study group patient, we noticed a cerebral oxygen saturation drop of 27 % below preoperative baseline. The NIRS-based clinical algorithm was initiated. No changes in rScO2 were observed after the first step, which according to the algorithm, was an assurance of correct head positioning. The next step was a raise in mean arterial pressure in both patients, as assessed by ephedrine administration. After the second step rScO2 values raised above the threshold, and no further intervention was necessary. Mean arterial pressure in the patients at the time of cerebral desaturation was 95 mmHg and 62 mmHg, respectively vs. 124 mmHg and 104 mmHg preoperatively. None of the patients showed postoperative cognitive decline – MOCA score remained unchanged pre- and postoperatively. In one control group patient, in whom intraoperative cerebral desaturation occurred, but the NIRS-based clinical algorithm was not applied, we detected a rScO2 drop of 21 % from the preoperative baseline values. The patient was 24 years old and showed a postoperative MOCA score decline of 4 points (from 29 points preoperatively to 25 points postoperatively). In the present study, we found a correlation between lower intraoperative rScO2 values and higher patient age, larger intraoperative blood loss, higher preoperative mean arterial pressure and lower preoperative MOCA score. In our study, 45.5 % patients from the control group, where cerebral oximetry was monitored blindly, no NIRS algorithm was applied, showed postoperative cognitive decline, compared to the study group where postoperative cognitive decline was observed in 21.4 % of patients. No correlation was found between intraoperative cerebral oxygenation and postoperative cognitive function. However, patients, who had a rScO2 decrease of > 10 % in any stage of surgery experienced a lower median MOCA score after the surgery. Near-infrared spectroscopy together with NIRS-based clinical algorithm is useful to manage intraoperative cerebral oxygen desaturation and to avoid postoperative cognitive disturbances.