Effect of head elevation on intracranial pressure, cerebral perfusion pressure, and regional cerebral oxygen saturation in patients with cerebral hemorrhage

OBJECTIVE: To study the effects on cerebral dynamics and regional oxygenation (rSO2) of the semi-sitting position, with the head at either 30 degrees or 45 degrees, in surgery for cerebral hemorrhage. PATIENTS AND METHODS: We performed a prospective study of 10 patients undergoing surgery for cerebral hemorrhage under sedation and analgesia and with mechanical ventilation. Intracranial pressure (ICP), mean arterial pressure (MAP), cerebral perfusion pressure (CPP), and rSO2 measured using near-infrared spectroscopy were recorded with the head in the supine position (0 degrees) and elevated to an angle of 30 degrees and then 45 degrees, following a stabilization period of 5 minutes. RESULTS: Mean (SD) ICP values were significantly lower in both semi-sitting positions than in the supine position: 2.8 (1.4) mm Hg lower at 30 degrees and 4.4 (1.4) mm Hg lower at 45 degrees. Mean CPP values were fell slightly when the head was elevated to 30 degrees (3.5 [3.1] mm Hg, P=.048); a greater reduction was achieved when the head was elevated 45 degrees (7.1 [4.8] mm Hg, P<.01). The greatest reduction in mean MAP values also occurred with the head elevated to 45 degrees (11.8 [4.6] mm Hg, P<.001). Mean rSO2 values fell when the head was elevated to 30 degrees and 45 degrees; the greatest reduction occurred when the head was elevated to 45 degrees (7% [2%], P<.001). There was a moderate correlation between CPP values and changes in rSO2 (r2=0.45, P<.001). CONCLUSION: Head elevation significantly reduces ICP and CPP in patients with cerebral hemorrhage. Head elevation also reduces rSO2, to a greater or lesser extent depending on the degree to which the head is elevated.     

Hyperacute measurement of brain-tissue oxygen, carbon dioxide, pH, and intracranial pressure before, during, and after cerebral angiography in patients with aneurysmatic subarachnoid hemorrhage in poor condition

BACKGROUND: The objective of this study was to examine early changes of intracranial pressure (ICP) and brain oxygenation before, during, and after cerebral angiography in patients with poor-grade subarachnoid hemorrhage (SAH). METHODS: Fourteen patients with poor-grade SAH without intracerebral hematoma were studied. A significant change in monitored variables (arterial gases, ICP, brain-tissue oxygen pressure [Ptio(2)], brain-tissue carbon dioxide pressure, and pH) was defined as a register deviation of more than 20% compared with the baseline. Critical Ptio(2) values (<15 mm Hg) or significant Ptio(2) decreases were considered to be impaired brain oxygenation. These data were correlated with the angiography findings and the presence of massive brain edema and hypodense areas in follow-up computed tomography (CT) scan controls. RESULTS: Neurotrend data were unavailable in 4 patients because of calibration failure. Impaired brain oxygenation during angiography was observed in 5 patients. Initial critical Ptio(2) values were found in 1 patient. Four patients developed a linear Ptio(2) and pH decrease after the angio-catheter canalized the examined vessels in the neck. Statistically significant correlation was found between brain pH and Ptio(2) changes in these patients (P < .001, Spearman rho). Arterial gases, ICP, and cerebral perfusion pressure did not show significant alterations at this time. Significant correlations existed between severe intracranial angiographic arterial caliber reduction and impaired Ptio(2) values (P < .01). Patients with impaired Ptio(2) values frequently showed lesions in CT scan controls (P < .05). CONCLUSIONS: This study documented several fluctuations in the brain oxygenation of patients with poor-grade SAH during angiography. Patients with severe intracranial angiographic arterial caliber reduction at this time have an increased risk for impaired brain oxygenation.     

Continuous measurement of jugular venous bulb oxygen saturation in neurosurgical patients.

Monitoring cerebral oxygen availability and utilization is of the utmost importance for patients with brain insults or potentially at risk of brain oxygen deprivation. The availability of the continuous measurement of oxygen saturation in the jugular bulb questions the value of this parameter as an indicator of brain oxygenation. This article reviews the theoretical background and the practical aspects of this monitoring. It describes its possible applications to neurosurgical patients in the operating theater as well as in the intensive therapy unit. Finally, it comments on its main limitations which could impede an extensive utilization in clinical practice.     

The effect of changes in cerebral perfusion pressure upon middle cerebral artery blood flow velocity and jugular bulb venous oxygen saturation after severe brain injury.

Middle cerebral artery blood flow velocity and jugular bulb venous oxygen saturation (SJO2) were measured by transcranial Doppler (TCD) ultrasonography and continuous venous oximetry, respectively, in 41 severely brain-injured patients. The purpose of the study was to examine the relationships between TCD flow velocity, SJO2, and alterations in blood pressure (BP), intracranial pressure (ICP), and cerebral perfusion pressure (CPP). In these patients, CPP was reduced either by rising ICP or by falling BP. Both forms of reduction of CPP resulted in a greater fall in diastolic flow velocity than other flow parameters. As CPP decreased below a critical value of 70 mm Hg, a progressive increase in TCD pulsatility index (PI) was observed (r = -0.942, p less than 0.0001), accompanied by a fall in SJO2 (r = 0.78, p less than 0.0001). At pressures above 70 mm Hg, there was no correlation of either PI or SJO2 with CPP. The relationship between PI and CPP held true in patients with both focal and diffuse pathologies and was the same whether changes in CPP resulted from alterations in ICP or BP. The PI and SJO2 correlated better with CPP than with ICP or BP. Transcranial Doppler ultrasonography can identify states of reduced CPP. Decreases in SJO2 with falling CPP suggested progressive failure of cerebral blood flow to meet metabolic demands. Monitoring of TCD and SJO2 may be used to define the optimum CPP level for management of severely brain-injured patients.     

Local cerebral blood flow mapping before and after removal of acute subdural hematoma in the rat.

The cause of hemispheric swelling and high intracranial pressure after acute subdural hematoma is unknown, yet this is a major cause of death related to this condition. To investigate whether vascular engorgement is the cause of this form of hemisphere swelling, we have autoradiographically mapped regional cerebral blood flow before and after removal of acute subdural hematoma in a rat model. Hyperemia was patchy and infrequent. The major cause of the significant hemisphere swelling seen after hematoma removal was enlargement of the zone of focal tissue ischemia and edema under the hematoma.     

Comparison of changes in jugular venous bulb oxygen saturation and cerebral oxygen saturation during variations of haemoglobin concentration under propofol and sevoflurane anaesthesia

Background. A severe reduction in haemoglobin concentrationcan lead to a decrease in jugular venous bulb oxygen saturation(     

Measuring brain tissue oxygenation compared with jugular venous oxygen saturation for monitoring cerebral oxygenation after traumatic brain injury

Jugular bulb oximetry is the most widely used method of monitoring cerebral oxygenation. More recently, measurement of brain tissue oxygenation has been reported in head-injured patients. We compared the changes in brain tissue oxygen partial pressure (PbO2) with changes in jugular venous oxygen saturation (SjVO2) in response to hyperventilation in areas of brain with and without focal pathology. Thirteen patients with severe head injuries were studied. A multiparameter sensor was inserted into areas of brain with focal pathology in five patients and outside areas of focal pathology in eight patients. A fiberoptic catheter was inserted into the right jugular bulb. Patients were hyperventilated in a stepwise manner from a PaCO2 of approximately 35 mm Hg to a PaCO2 of 22 mm Hg. There was no significant change in cerebral perfusion pressure or arterial partial pressure of oxygen with hyperventilation. In areas without focal pathology, there was a good correlation between changes in SjVO2 and PbO2 (deltaSjVO2 and deltaPbO2; r2 = 0.69, P < 0.0001). In areas with focal pathology, there was no correlation between deltaSjVO, and APbO2 (r2 =0.07, P = 0.23). In this study, we demonstrated that measurement of local tissue oxygenation can highlight focal differences in regional cerebral oxygenation that are disguised when measuring SjVO2. Thus, monitoring of PbO2 is a useful addition to multimodal monitoring of patients with traumatic head injury. IMPLICATIONS: Brain oxygenation is currently monitored by using jugular bulb oximetry, which attracts a number of potential artifacts and may not reflect regional changes in oxygenation. We compared this method with measurement of brain tissue oxygenation using a multiparameter sensor inserted into brain tissue. The brain tissue monitor seemed to reflect regional brain oxygenation better than jugular bulb oximetry.     

Infusion rate of propofol and jugular venous oxygen saturation

We compared jugular venous blood oxygen saturation (Sj(O) (2)) and the arterial-to-jugular-bulb venous oxygen content difference (AjD(O) (2)) between bispectral index (BIS) values of 40 and 60, adjusted by the infusion rate of propofol. Eighteen postoperative neurosurgical patients (Glasgow Coma Scale [GCS] scores, 11-15) were enrolled. Normocapnia, normothermia, and a mean arterial blood pressure greater than 70 mmHg were maintained. At BIS values of 40 and 60, hemoglobin, oxygen saturation, and the oxygen partial pressure of arterial and jugular venous blood were measured. Sj(O) (2) at BIS40 (58 +/- 9%) was significantly (P < 0.01) lower than that at BIS60 (63 +/- 10%), and AjD(O) (2) at BIS40 (6.3 +/- 1.5 ml.dl(-1)) was significantly (P < 0.01) higher than that at BIS60 (5.7 +/- 1.5 ml.dl(-1); mean +/- SD). At BIS40, status defined as Sj(O) (2) less than 50% was observed in 3 patients, while this status was observed in 1 patient at BIS60. In conclusion, in patients with postoperative neurosurgical surgery (GCS scores, 11-15), decreases of propofol infusion to adjust the BIS value from 40 to 60 increase the cerebral oxygen balance.     

Evaluation of cerebral oxygen balance during normothermic cardiopulmonary bypass using jugular oxygen saturation

BACKGROUND: Previous studies suggest that normothermic cardiopulmonary bypass(CPB) impairs cerebral oxygen balance. We studied the effect of normothermic CPB on cerebral oxygen balance evaluated by continuous measurement of oxygen saturation in the jugular vein (SjO2). METHODS: Eleven patients undergoing coronary artery bypass grafting with normothermic CPB were studied. A 4 Fr oxymetry catheter was inserted into the internal jugular bulb for SjO2 monitoring. We measured mean arterial pressure (MAP), SjO2 and hemoglobin (Hgb) concentration at five time points-1) pre CPB, 2) 3) 4) 5, 30, 60 min after the onset of CPB, respectively, 5) 5 min after the end of CPB. RESULTS: MAP decreased significantly 30 min (47 +/- 9 mmHg) and 60 min (48 +/- 9 mmHg) after the onset of CPB compared with the pre CPB (80 +/- 14 mmHg) value. Hgb also decreased significantly 5 min (7.8 +/- 1.1 g x dl(-1)) and 30 min (7.1 +/- 1.0 g x dl(-1)) and 60 min (7.1 +/- 0.8 g x dl(-1)) after the onset of CPB compared with the pre CPB (11 +/- 1.0 g x dl(-1)) value. However, SjO2 showed no significant change throughout the study period. No significant correlation was observed between MAP and SjO2. CONCLUSIONS: Cerebral oxygen balance assessed by SjO2 was not impaired during normothermic CPB, and was unaffected by hypotension and hemodilution.     

Analysis of factors related to jugular venous oxygen saturation during cardiopulmonary bypass

OBJECTIVE: To investigate preoperative clinical conditions and/or intraoperative physiologic variables related to jugular venous oxygen saturation (SjO2) during cardiopulmonary bypass (CPB). DESIGN: Prospective study. SETTING: General hospital, single institution. PARTICIPANTS: One hundred forty patients (52 women, 88 men) who underwent coronary artery bypass grafting. MEASUREMENTS AND MAIN RESULTS: The authors measured SjO2 at five times during surgery. Multiple stepwise regression analysis showed a significant correlation of SjO2 with (1) arterial carbon dioxide partial pressure (PaCO2) before CPB (standard regression coefficient [(SC)] = 0.435), (2) cerebral perfusion pressure (CPP) during initiation of CPB (SC = 0.259), (3) PaCO2, tympanic temperature (TT), bubble oxygenator, and cerebral small infarctions (CSIs) during hypothermic CPB (SC = 0.507, -0.237, -0.192, and -0.189, respectively), (4) CPP, PaCO2, CSIs, and bubble oxygenator during rewarming (SC = 0.476, 0.294, -0.220, and -0.189, respectively), and (5) PaCO2 after CPB (SC = 0.480; p < 0.01). Correlation coefficients between SjO2 and CPP during rewarming were 0.40 (0.46 without CSI and 0.37 with CSI; p < 0.01). These results indicate that the relationship between CPP and SjO2 was significant in patients with CPP less than 40 mmHg during rewarming. CONCLUSION: During rewarming, when cerebral perfusion and oxygen demand change abruptly, but not during stable hypothermic CPB, CPP was a significant factor related to sjO2.     

全凭静脉麻醉下过度通气对颈内静脉血氧饱和度的影响

目的评价神经外科患者全凭静脉麻醉下不同PETCO2水平对颈内静脉血氧饱和度(SjvO2)的影响。方法择期行幕上颅内肿瘤切除术患者12例,ASAⅠ或Ⅱ级,全凭静脉麻醉下根据计算机产生的随机表,按随机顺序将PETCO2分别控制到如下水平:25、35、45mmHg;稳定10min后同时取动脉血和颈静脉球部血进行血气分析,并同时记录MAP、HR、食管温度(TESO)、脑电双频指数(BIS)等参数。结果PETCO2为25、35和45mmHg时,SjvO2分别为(53.7±2.5)%、(69.3±3.8)%和(81.8±2.0)%,组间比较差异有统计学意义(P<0.01)。结论神经外科患者全凭静脉麻醉下随着PCO的降低,SjvO也明显下降。     

Validity of laser Doppler flowmetry for measuring the effect of the tissue expander pressure on skin circulation. Simultaneous measurement of tissue pressure and laser Doppler flowmetry

Intermittent Laser Doppler Flowmetry (LDF) was used in five patients to measure changes in the dermal blood flow when changing intraluminal pressures in tissue expanders (TE). In another patient, continuous monitoring of the intraluminal pressure in the TE and simultaneous LDF was used. Our finding is that LDF is a suitable method for the registration of reactions in dermal circulation, caused by TE pressure changes. A statistically significant association between the changes of the LDF values and the intraluminal pressure in the TE was observed.     

Reliability of continuous jugular venous bulb hemoglobin oxygen saturation during cardiac surgery.

OBJECTIVE: To evaluate the accuracy and reliability of continuous measurement of jugular venous bulb hemoglobin oxygen saturation (SjvO2) with a fiberoptic catheter (SjvO(2OX)) during cardiac surgery versus simultaneous paired measurements of hemoglobin oxygen saturation by the Hemoximeter (SjVO(2HEM); Radiometer, Copenhagen, Denmark) and indirect estimations of hemoglobin oxygen saturation from measurements of partial pressure of oxygen in blood gases (SjVO(2BG)). DESIGN: A prospective study. SETTING: American Hellenic Educational Progressive Association General Hospital, University Hospital of Thessaloniki, Greece. PATIENTS: Thirty patients undergoing elective aortocoronary artery bypass surgery. INTERVENTIONS: In addition to routine pressure monitoring, a 4F fiberoptic catheter was placed in the left jugular bulb by a retrograde internal jugular vein approach and SIvO(2OX) was continuously measured. Before insertion, each catheter was calibrated in vitro. MEASUREMENTS AND MAIN RESULTS: One hundred twelve simultaneous paired recordings between SjvO(2OX) and SjVO2BG were performed to define the accuracy of SjVO(2OX) to SjVO(2BG). Sixty-one of 112 simultaneous paired recordings between SjvO(2OX) and SjVO(2HEM) and SjVO(2HEM) and SjVO(2BG) were performed to define the accuracy of SjvO(2OX) to the reference SjVO(2HEM) and the reliability of the SjVO(2BG) measurement to SjVO(2HEM). The fiberoptic catheter readings varied from underestimating to overestimating hemoglobin saturation by a mean of -5.35% to +9.67% and of -3.22% to +7.81% versus Blood Gas Analyzer (Ciba-Corning) and Co-Oximeter (OSM 2b Hemoximeter, Radiometer) values, respectively. The mean underestimation and overestimation of Co-Oximeter versus Blood Gas Analyzer values were -3.18% and +4.17%, respectively. CONCLUSION: SjvO2 values obtained continuously from a jugular venous bulb fiberoptic catheter may give relatively accurate readings provided they are duly interpreted and errors caused by wall artifact or blood sampling are avoided.     

Positive end-expiratory pressure alters intracranial and cerebral perfusion pressure in severe traumatic brain injury

BACKGROUND: Optimizing intracranial pressure (ICP) and cerebral perfusion pressure (CPP) is important in the management of severe traumatic brain injury (TBI). In trauma patients with TBI and respiratory dysfunction, positive end-expiratory pressure (PEEP) is often required to support oxygenation. Increases in PEEP may lead to reduced CPP. We hypothesized that increases in PEEP are associated with compromised hemodynamics and altered cerebral perfusion. METHODS: Twenty patients (mean Injury Severity Score of 28) with TBI (Glasgow Coma Scale score < 8) were examined. All required simultaneous ICP and hemodynamic monitoring. Data were categorized on the basis of PEEP levels. Variables included central venous pressure, pulmonary artery occlusion pressure, cardiac index, oxygen delivery, and oxygen consumption indices. Differences were assessed using Kruskal-Wallis analysis of variance. RESULTS: Data were expressed as mean +/- SE. As PEEP increased from 0 to 5, to 6 to 10 and 11 to 15 cm H O, ICP decreased from 14.7 +/- 0.2 to 13.6 +/- 0.2 and 13.1 +/- 0.3 mm Hg, respectively. Concurrently, CPP improved from 77.5 +/- 0.3 to 80.1 +/- 0.5 and 78.9 +/- 0.7 mm Hg. As central venous pressure (5.9 +/- 0.1, 8.3 +/- 0.2, and 12.0 +/- 0.3 mm Hg) and pulmonary artery occlusion pressure (8.3 +/- 0.2, 11.6 +/- 0.4, and 15.6 +/- 0.4 mm Hg) increased with rising levels of PEEP, cardiac index, oxygen delivery, and oxygen consumption indices remained unaffected. Overall mortality was 30%. CONCLUSION: In trauma patients with severe TBI, the strategy of increasing PEEP to optimize oxygenation is not associated with reduced cerebral perfusion or compromised oxygen transport.