The effects of 10 degrees reverse trendelenburg position on ICP and CPP in prone positioned patients subjected to craniotomy for occipital or cerebellar tumours

Summary. Summary.   Background: Control of ICP-hypertension is of utmost importance during craniotomy. The effects of reverse Trendelenburg position (RTP) upon ICP and CPP have recently been studied in supine positioned patients.   Method: In this study we investigated changes in intracranial pressure (ICP), mean arterial blood pressure (MABP), CPP and jugular bulb pressure (JBP) before and one minute after 10^° RTP in 26 prone positioned patients with either occipital (n=12) or cerebellar tumours (n=14). ICP was measured by a subdural approach after removal of the bone flap. Tension of the dura was estimated by the surgeons by digital palpation before and after change in position.   Findings: In patients with occipital tumours ICP decreased from 21.0 to 15.6 mm Hg (p<0.05). MABP decreased from 87.9 to 83.3 mm Hg (p<0.05), JBP decreased from 14.3 to 7.7 mm Hg (P<0.05), while CPP was unchanged. In patients with cerebellar tumours ICP decreased from 18.3 to 14.2 mm Hg (p<0.05). MABP decreased from 93,8 to 90.5 mm Hg (p<0.05), JBP decreased from 12.1 to 5.0 mm Hg (P<0.05), while CPP was unchanged. There were no significant differences between the two groups with regard to changes in ICP, MABP, CPP and JBP. The change in ICP was accompanied by a significant decrease in dural tension (p<0.05).   Interpretation: In prone positioned patients 10^° RTP significantly reduces ICP, JPB and MABP within one minute, while CPP is unchanged. Published online July 18, 2002     

The ICP-lowering effect of 10 degrees reverse Trendelenburg position during craniotomy is stable during a 10-minute period

Recently we studied the effect of 10 degrees reverse Trendelenburg position on subdural pressure and cerebral perfusion pressure (CPP) during craniotomy. Within 1 minute we found a significant decrease in subdural pressure while CPP was unchanged. A longer time span, however, is necessary to exclude a temporary effect. In the present investigation we studied subdural pressure, CPP, and jugular bulb pressure (JBP) before and during a 10-minute period after change in position. Fifteen patients with supratentorial cerebral tumors were anesthetized with propofol/fentanyl in the supine position. Mean arterial blood pressure and JBP were measured invasively, and subdural pressure was measured after removal of the bone flap. End-tidal CO2, PaCO2, PaO2, heart rate, jugular venous oxygen saturation (SjO2), and arteriovenous oxygen difference (AVDO2) were also measured. Dural tension was estimated by the surgeon. The measurements were performed with the patients in a neutral position and during a 10-minute period after positioning the patient in a 10 degrees reverse Trendelenburg position. After 1 minute in the reverse Trendelenburg position, the mean value of subdural pressure decreased from 10.9 +/- 5.7 to 7.3 +/- 5.2 mm Hg (P<0.05) and remained unchanged for the following 9 minutes. Correspondingly, dural tension was lessened significantly. Jugular pressure and mean arterial blood pressure decreased significantly as well (P<0.05), but the CPP was unaffected. No significant changes in PaCO2, PaO2, end-tidal CO2, heart rate, SjO2, or AVDO2 were disclosed. During craniotomy 10 degrees reverse Trendelenburg position reduces subdural pressure and dural tension within 1 minute without reducing CPP. During the following 9 minutes the levels of subdural pressure and CPP are unchanged.     

Optimal reverse trendelenburg position in patients undergoing craniotomy for cerebral tumors

OBJECT: To the authors' knowledge, repeated measurements of intracranial pressure (ICP), cerebral perfusion pressure (CPP), and the degree of dural tension during different positions on the operating table (reverse Trendelenburg position [rTp]) have not been studied in patients undergoing craniotomy. METHODS: In the present study 53 patients with supratentorial cerebral tumors who underwent craniotomy in the supine position were included. Subdural ICP, mean arterial blood pressure (MABP), CPP, and jugular bulb (JB) pressure were recorded, and the degree of dural tension was analyzed while patients were in the neutral operating position and at 5, 10, and 15 degrees rTp. The optimal operating position was defined as the one at which subdural ICP was as low as possible, and CPP was greater than or equal to 60 mm Hg or as high as possible. Subdural ICP, MABP, and JB pressure decreased significantly after each 5 degrres change in rTp compared with the preceding position. Dural tension decreased significantly up to 10 degrees rTp, but was unchanged at 15 degrees rTp. At 5 degrees rTp CPP remained unchanged, but it decreased significantly during 10 and 15 degrees rTp. The optimal position in the majority of patients was determined to be 15 degrees rTp. CONCLUSIONS: Before opening the dura mater for craniotomy, repeated measurements of ICP and CPP, in the neutral position and at 5, 10, and 15 degrees rTp, provide valuable information regarding the optimal level of ICP and CPP.     

Hyperacute measurement of intracranial pressure, cerebral perfusion pressure, jugular venous oxygen saturation, and laser Doppler flowmetry, before and during removal of traumatic acute subdural hematoma

OBJECT: The poor prognosis for traumatic acute subdural hematoma (ASDH) might be due to underlying primary brain damage, ischemia, or both. Ischemia in ASDH is likely caused by increased intracranial pressure (ICP) leading to decreased cerebral perfusion pressure (CPP), but the degree to which these phenomena occur is unknown. The authors report data obtained before and during removal of ASDH in five cases. METHODS: Five patients who underwent emergency evacuation of ASDH were monitored. In all patients, without delaying treatment, a separate surgical team (including the senior author) placed an ICP monitor and a jugular bulb catheter, and in two patients a laser Doppler probe was placed. The ICP prior to removing the bone flap in the five patients was 85, 85, 50, 59, and greater than 40 mm Hg, resulting in CPPs of 25, 3, 25, 56, and less than 50 mm Hg, respectively. Removing the bone flap as well as opening the dura and removing the blood clot produced a significant decrease in ICP and an increase in CPP. Jugular venous oxygen saturation (SjvO2) increased in four patients and decreased in the other during removal of the hematoma. Laser Doppler flow also increased, to 217% and 211% compared with preevacuation flow. CONCLUSIONS: Intracranial pressure is higher than previously suspected and CPP is very low in patients with ASDH. Removal of the bone flap yielded a significant reduction in ICP, which was further decreased by opening the dura and evacuating the hematoma. The SjvO2 as well as laser Doppler flow increased in all patients but one immediately after removal of the hematoma.     

The effects of 10 degrees reverse Trendelenburg position on subdural intracranial pressure and cerebral perfusion pressure in patients subjected to craniotomy for cerebral aneurysm

The aim of the current study was to examine the effects of 10 degrees reverse Trendelenburg position (rTp) on subdural intracranial pressure (ICP), cerebral perfusion pressure (CPP), and dural tension. Additionally, the relationship between preoperative Hunt and Hess (H and H) grade and the subdural ICP in patients scheduled for cerebral aneurysm surgery was investigated. Twenty-eight consecutive patients with a cerebral aneurysm were subjected to craniotomy in propofol/fentanyl or propofol/remifentanil anesthesia. Subdural ICP was measured after opening of the bone flap and exposure of dura. After reference measurements of subdural ICP and mean arterial blood pressure (MABP), the measurements were repeated during 10 degrees rTp. No significant differences between the anesthetic groups were disclosed. During 10 degrees rTp, a significant decrease in MABP, ICP, and jugular bulb pressure was observed whereas CPP remained unchanged. In H and H 0 patients (unruptured aneurysm), the ICP decreased from 2.9 +/- 2.6 mmHg to 0.4 +/- 2.2 mmHg at 10 degrees rTp. In H and H I to II patients, the ICP decreased from 9.3 +/- 3.8 mmHg to 4.6 +/- 3.3 mmHg at 10 degrees rTp. A significant difference in the mean baseline subdural ICP and DeltaICP (change in ICP) was found between patients with unruptured aneurysm and patients with subarachnoid hemorrhage (H&H I and II). Furthermore, the relationship between the subdural ICP at neutral position and DeltaICP was significant. In patients without intracranial hypertension, 10 degrees rTp decreases subdural ICP and dural tension in patients with ruptured as well as patients with unruptured cerebral aneurysm; CPP is unchanged.     

Effects of dihydroergotamine on intracranial pressure, cerebral blood flow, and cerebral metabolism in patients undergoing craniotomy for brain tumors.

In a search for a nonsurgical intervention to control intracranial hypertension during craniotomy, the authors studied the effects of dihydroergotamine on mean arterial blood pressure (MABP), intracranial pressure (ICP), cerebral perfusion pressure (CPP), cerebral blood flow (CBF), and cerebral metabolism in patients who underwent craniotomy for supratentorial brain tumors. Twenty patients were randomized to receive either dihydroergotamine 0.25 mg intravenously or placebo as a bolus dose during craniotomy. Anesthesia was induced with thiopental/fentanyl/atracurium, and maintained with isoflurane/N2O/fentanyl at normocapnia. After removal of the bone flap and exposure of intact dura, ICP was measured subdurally and dihydroergotamine/placebo was administered. Intracranial pressure and MABP were measured continuously. Cerebral blood flow (after intravenous administration of 133Xe) and arteriojugular venous difference of oxygen (AVDO2) were measured before, and 30 minutes after, dihydroergotamine/placebo administration. Cerebral metabolic rate of oxygen (CMRO2) was calculated. After administration of dihydroergotamine, a significant increase in MABP from 74 to 87 mm Hg (median) and CPP from 65 to 72 mm Hg (median) were found. Simultaneously to the increase in MABP, a significant increase in ICP from 9.5 to 11.5 mm Hg (median) was disclosed, whereas no significant differences in CBF, AVDO2, or CMRO2 were found. Intracranial pressure was significantly higher after dihydroergotamine than after placebo. In conclusion, no ICP decreasing effect of a bolus dose of dihydroergotamine was found when administered to patients with brain tumors during isoflurane/N2O anesthesia. Corresponding increases in MABP and ICP suggest that abolished cerebral autoregulation might explain why dihydroergotamine was associated with an ICP increase.     

The influence of some inhalation anaesthetics on the intracranial pressure with special reference to nitrous oxide (author's transl)]

The influence of inhalation anaesthetics on intracranial pressure (ICP), arterial blood pressure and cerebral perfusion pressure (CPP) was investigated on 12 unconscious patients with head injury having an initial ICP of about 20 mm Hg. Halothane, enflurane and nitrous oxide induced a considerable rise of ICP during a 15 to 25 minute period of observation. The moderate fall in blood pressure caused by halothane and enflurane enhanced the reduction of the calculated CPP. Besides, a regular fall in blood pressure of about 16% was observed under the influence of nitrous oxide, subsequently reducing the CPP in some cases under 40 mm Hg. Inhalation anaesthetics, including nitrous oxide, should therefore not be used in patients with decreased intracranial compliance before the increased ICP is treated.     

Is cerebral perfusion pressure a major determinant of cerebral blood flow during head elevation in comatose patients with severe intracranial lesions?

OBJECT: Head elevation as a treatment for lower intracranial pressure (ICP) in patients with intracranial hypertension has been challenged in recent years. Therefore, the authors studied the effect of head position on cerebral hemodynamics in patients with severe head injury. METHODS: The effect of 0 degrees, 15 degrees, 30 degrees, and 45 degrees head elevation on ICP, cerebral blood flow (CBF), systemic arterial (PsaMonro) and jugular bulb (Pj) pressures calibrated to the level of the foramen of Monro, cerebral perfusion pressure (CPP), and the arteriovenous pressure gradient (PsaMonro - Pj) was studied in 37 patients who were comatose due to severe intracranial lesions. The CBF decreased gradually with head elevation from 0 to 45 degrees, from 46.3+/-4.8 to 28.7+/-2.3 ml x min(-1) x 100 g(-1) (mean +/- standard error, p<0.01), and the PsaMonro - Pj from 80+/-3 to 73+/-3 mm Hg (p< 0.01). The CPP remained stable between 0 degrees and 30 degrees of head elevation, at 62+/-3 mm Hg, and decreased from 62+/-3 to 57+/-4 mm Hg between 30 degrees and 45 degrees (p<0.05). A simulation showed that the 38% decrease in CBF between 0 degrees and 45 degrees resulted from PsaMonro - Pj changes for 19% of the decrease, from a diversion of the venous drainage from the internal jugular veins to vertebral venous plexus for 15%, and from CPP changes for 4%. CONCLUSIONS: During head elevation the arteriovenous pressure gradient is the major determinant of CBF. The influence of CPP on CBF decreases from 0 to 45 degrees of head elevation.     

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.     

Intracranial Pressure and Cerebral Hemodynamic in Patients with Cerebral Tumors: A Randomized Prospective Study of Patients Subjected to Craniotomy in Propofol-Fentanyl, Isoflurane-Fentanyl, or Sevoflurane-Fentanyl Anesthesia

Background: A critical point during craniotomy is opening of dura, where a high intracranial pressure (ICP) results in swelling of cerebral tissue. Controlled studies concerning ICP, degree of dural tension, and degree of cerebral swelling are therefore warranted.

Methods: In an open-label study, 117 patients with supratentorial cerebral tumors were randomized to propofol-fentanyl (group 1), isoflurane-fentanyl (group 2), or sevoflurane-fentanyl anesthesia (group 3). Normo- to moderate hypocapnia was applied, with a target level of arterial carbon dioxid tension of 30-40 mmHg. Mean arterial blood pressure was stabilized with intravenous ephedrine (2.5-5 mg) if necessary. Subdural ICP, mean arterial blood pressure, cerebral perfusion pressure (CPP), arteriovenous oxygen difference (AVDo2), internal jugular vein oxygen saturation were monitored before and after a 10-min period of hyperventilation, and the carbon dioxide reactivity was calculated. Furthermore, the tension of dura before and during hyperventilation and the degree of cerebral swelling during hyperventilation and after opening of the dura were estimated by the neurosurgeon.

Results: No differences were found between groups with regard to demographics, neuroradiologic examination, positioning of the head, and time to ICP measurement. Before and during hyperventilation, ICP was significantly lower and mean arterial blood pressure and CPP significantly higher in group 1 compared with groups 2 and 3 (P < 0.05). The tension of dura before and during hyperventilation was significantly lower in group 1 compared with group2 (P < 0.05), but not significantly different from group 3. In group 1, cerebral swelling after opening of dura was significantly lower compared with groups 2 and 3 (P < 0.05). Furthermore, AVDo2 was significantly higher and jugular vein oxygen saturation and carbon dioxide reactivity were significantly lower in group 1 compared with groups 2 and 3 (P < 0.05). No significant differences with regard to ICP, CPP, AVDo2, carbon dioxide reactivity, and jugular vein oxygen saturation were found between patients anesthetized with isoflurane and sevoflurane.     

Intracranial pressure and cerebral hemodynamic in patients with cerebral tumors: a randomized prospective study of patients subjected to craniotomy in propofol-fentanyl,isoflurane-fentanyl,or sevoflurane-fentanyl anesthesia

BACKGROUND: A critical point during craniotomy is opening of dura, where a high intracranial pressure (ICP) results in swelling of cerebral tissue. Controlled studies concerning ICP, degree of dural tension, and degree of cerebral swelling are therefore warranted. METHODS: In an open-label study, 117 patients with supratentorial cerebral tumors were randomized to propofol-fentanyl (group 1), isoflurane-fentanyl (group 2), or sevoflurane-fentanyl anesthesia (group 3). Normo- to moderate hypocapnia was applied, with a target level of arterial carbon dioxid tension of 30-40 mmHg. Mean arterial blood pressure was stabilized with intravenous ephedrine (2.5-5 mg) if necessary. Subdural ICP, mean arterial blood pressure, cerebral perfusion pressure (CPP), arteriovenous oxygen difference (AVDo2), internal jugular vein oxygen saturation were monitored before and after a 10-min period of hyperventilation, and the carbon dioxide reactivity was calculated. Furthermore, the tension of dura before and during hyperventilation and the degree of cerebral swelling during hyperventilation and after opening of the dura were estimated by the neurosurgeon. RESULTS: No differences were found between groups with regard to demographics, neuroradiologic examination, positioning of the head, and time to ICP measurement. Before and during hyperventilation, ICP was significantly lower and mean arterial blood pressure and CPP significantly higher in group 1 compared with groups 2 and 3 (P < 0.05). The tension of dura before and during hyperventilation was significantly lower in group 1 compared with group2 (P < 0.05), but not significantly different from group 3. In group 1, cerebral swelling after opening of dura was significantly lower compared with groups 2 and 3 (P < 0.05). Furthermore, AVDo was significantly higher and jugular vein oxygen saturation and carbon dioxide reactivity were significantly lower in group 1 compared with groups 2 and 3 (P < 0.05). No significant differences with regard to ICP, CPP, AVDo, carbon dioxide reactivity, and jugular vein oxygen saturation were found between patients anesthetized with isoflurane and sevoflurane. CONCLUSIONS: The study indicates that before as well as during hyperventilation, subdural ICP and AVDo2 are lower and CPP higher in propofol-anesthetized patients compared with patients anesthetized with isoflurane or sevoflurane. These findings were associated with less tendency for cerebral swelling after opening of dura in the propofol group. The carbon dioxide reactivity in patients anesthetized with isoflurane and sevoflurane was significantly higher than in the propofol group. The differences in subdural ICP between the groups are presumed to be caused by differences in the degree of vasoconstriction elicited by the anesthetic agents, but autoregulatory mechanisms caused by differences in CPP cannot be excluded.     

Cerebral hemodynamic responses to blood pressure manipulation in severely head-injured patients in the presence or absence of intracranial hypertension

The management of cerebral perfusion pressure (CPP) remains a controversial issue in the critical care of severely head-injured patients. Recently, it has been proposed that the state of cerebrovascular autoregulation should determine individual CPP targets. To find optimal perfusion pressure, we pharmacologically manipulated CPP in a range of 51 mm Hg (median; 25th-75th percentile, 48-53 mm Hg) to 108 mm Hg (102-112 mm Hg) on Days 0, 1, and 2 after severe head injury in 13 patients and studied the effects on intracranial pressure (ICP), autoregulation capacity, and brain tissue partial pressure of oxygen. Autoregulation was expressed as a static rate of regulation for 5-mm Hg CPP intervals based on middle cerebral artery flow velocity. When ICP was normal (26 occasions), there were no major changes in the measured variables when CPP was altered from a baseline level of 78 mm Hg (74-83 mm Hg), indicating that the brain was within autoregulation limits. Conversely, when intracranial hypertension was present (11 occasions), CPP reduction to less than 77 mm Hg (73-82 mm Hg) further increased ICP, decreased the static rate of regulation, and decreased brain tissue partial pressure of oxygen, whereas a CPP increase improved these variables, indicating that the brain was operating at the lower limit of autoregulation. We conclude that daily trial manipulation of arterial blood pressure over a wide range can provide information that may be used to optimize CPP management.     

Continuous monitoring of cerebral oxygenation in acute brain injury: assessment of cerebral hemodynamic reserve

A new index of cerebral hemodynamics, cerebral hemodynamic reserve (CHR), was evaluated in 12 comatose adults with severe, acute, traumatic, diffuse swelling of the brain, who underwent continuous monitoring with a fiberoptic catheter of the saturation difference in arteriojugular oxyhemoglobin. CHR was assessed as the ratio of changes in global cerebral oxygen extraction to changes in cerebral perfusion pressure (CPP) as a result of spontaneous increases in intracranial pressure (ICP). During the course of hyperventilation (Pco2 in the range of 20 mm Hg) for ICP control below 20 mm Hg, 34 observations were made over the initial 48 hours postinjury. Despite normal CPP, in 25 of the observations (73.5%), ICP elevations to the range of 20 mm Hg were associated with compromised CHR, as evidenced by decreases in jugular oxygenation directly attributed to the ICP increases. In the remaining nine observations (26.5%), CHR was preserved, as evidenced by no changes or increases in jugular oxygenation when ICP increased. The CHR improved on the second day, suggesting an improved tolerance of the cerebral hemodynamics to ICP increases. Before the ICP elevations, in most of the observations, the global cerebral blood flow was estimated as being optimally decreased (by hypocapnia), in relation to cerebral oxygen consumption. This was reflected by the occurrence of baseline normalized cerebral oxygen extraction. It is concluded that in this group of patients, under circumstances of profound hyperventilation, ICP elevations within the normal CPP range may result in decreased cerebral oxygenation, even when the normal CPP would imply otherwise. It is suggested that CHR assessment may provide information regarding the status of intracranial "tightness," insofar as cerebral circulation and oxygenation are concerned.     

Subdural pressure measurement during posterior fossa surgery. Correlation studies of brain swelling/herniation after dural incision with measurement of subdural pressure and tactile estimation of dural tension

Thirty-two patients with posterior fossa tumours or arteriovenous malformations were subjected to elective craniotomy in the prone position. The intracranial pressure (ICP) was measured by a subdural approach in the open area of the exposed dura. Estimation of dural tension before dural incision and the degree of brain swelling/herniation after opening the dura were correlated with the subdural pressure measured with intact dura. The results indicate that at ICP < 10 mmHg, brain swelling/herniation rarely occurred, while at ICP > or = 10 mmHg some degree of brain swelling/herniation was always present. The neurosurgeon's tactile estimation of dural tension correlated poorly with any tendency to brain swelling/herniation. It is concluded that measurement of subdural pressure is a better predictor of the risk of brain swelling/herniation than the tactile estimation of dural tension during posterior fossa surgery.     

Effects of PEEP on the intracranial system of patients with head injury and subarachnoid hemorrhage: the role of respiratory system compliance

BACKGROUND: Positive end-expiratory pressure (PEEP) can be effective in improving oxygenation, but it may worsen or induce intracranial hypertension. The authors hypothesized that the intracranial effects of PEEP could be related to the changes in respiratory system compliance (Crs). METHODS: A prospective study investigated 21 comatose patients with severe head injury or subarachnoid hemorrhage receiving intracranial pressure (ICP) monitoring who required mechanical ventilation and PEEP. The 13 patients with normal Crs were analyzed as group A and the 8 patients with low Crs as group B. During the study, 0, 5, 8, and 12 cm H2O of PEEP were applied in a random sequence. Jugular pressure, central venous pressure (CVP), cerebral perfusion pressure (CPP), intracranial pressure (ICP), cerebral compliance, mean velocity of the middle cerebral arteries, and jugular oxygen saturation were evaluated simultaneously. RESULTS: In the group A patients, the PEEP increase from 0 to 12 cm H2O significantly increased CVP (from 10.6 +/- 3.3 to 13.8 +/- 3.3 mm Hg; p < 0.001) and jugular pressure (from 16.6 +/- 3.1 to 18.8 +/- 3.2 mm Hg; p < 0.001), but reduced mean arterial pressure (from 96.3 +/- 6.7 to 91.3 +/- 6.5 mm Hg; p < 0.01), CPP (from 82.2 +/- 6.9 to 77.0 +/- 6.2 mm Hg; p < 0.01), and mean velocity of the middle cerebral arteries (from 73.1 +/- 27.9 to 67.4 +/- 27.1 cm/sec; F = 7.15; p < 0.001). No significant variation in these parameters was observed in group B patients. After the PEEP increase, ICP and cerebral compliance did not change in either group. Although jugular oxygen saturation decreased slightly, it in no case dropped below 50%. CONCLUSIONS: In patients with low Crs, PEEP has no significant effect on cerebral and systemic hemodynamics. Monitoring of Crs may be useful for avoiding deleterious effects of PEEP on the intracranial system of patients with normal Crs.     

甘露醇对颅脑手术患者脑氧供需平衡的影响

目的：探讨颅脑手术麻醉期间静脉输注甘露醇对脑氧供需平衡的影响。方法：选择静脉全麻醉上开颅行幕上肿瘤切除术患者14例，分别检测静脉输液25％甘露醇1g/kg输液前和输注后，30，60分钟时的颅内压（ICP），颈内静脉和桡动脉的血气，计算脑灌注压（CPP），动－颈静氧含量差（C(a-j)O2)和脑氧摄取率（CEO2）。结果：甘露醇输注后30分钟，ICP和心率（HR）较输注前显著降低（P＜0．05），但CPP，C(a-j)O2和CEO2虽呈下降趋势，但与输液前比较均无统计学差异。结论：颅脑手术麻醉期间输注甘露醇，不仅可降低ICP，对MAP和CPP无明显影响，而且能改善脑血流代谢耦联，对开颅手术的病人有利。     

Prognostic value of early computerized tomography scanning following craniotomy for traumatic hematoma.

OBJECT: Patients with head injuries traditionally were categorized on the basis of whether their lesions appeared to be diffuse, focal, or mass lesions on admission computerized tomography (CT) scanning. In the classification of Marshall, et al., the presence of a hematoma (evacuated or not evacuated) is more significant than any diffuse injury (DI). The CT scan appearance after evacuation of a mass lesion has not been analyzed previously in relation to outcome. The authors have investigated the importance of: 1) neurological assessment at hospital admission; 2) the status of the basal cisterns and associated intracranial lesions on the admission CT scan; and 3) the degree of DI on the early CT scan obtained after craniotomy to identify patients at risk for development of raised intracranial pressure (ICP) and lowered cerebral perfusion pressure (CPP) and to discover the influence of the postoperative CT appearance of the lesion on patient outcome. METHODS: The authors prospectively studied 82 patients with isolated, severe closed head injury (Glasgow Coma Scale [GCS] score < or = 8), all of whom had intracranial hematoma. Both ICP and CPP were continuously monitored, and a CT scan was obtained within 2 to 12 hours after craniotomy. The CT images were categorized according to the classification of Marshall, et al. The mortality rate during the hospital stay was 37%, and 50% of the patients achieved a favorable outcome. Compression of the basal cistern on the admission (preoperative) CT scan was associated with raised ICP and a CPP of less than 70 mm Hg but not with any other features or with poor patient outcome. In 53 patients the postoperative CT scan revealed DIs III or IV and 29 patients had DIs I or II. The percentages of time during the hospital stay in which ICP was higher than 20 mm Hg and CPP was lower than 70 mm Hg as well as unfavorable outcome were higher in the group of patients in whom DI III or IV was present (p < 0.001). Raised ICP, CPP lower than 70 mm Hg, DI III or IV, and unfavorable outcome were more frequently observed in patients who presented with a motor (m)GCS score of 3 or less, bilateral unreactive pupils, associated intracranial injuries, and hypotension (p < 0.001). When logistic regression analysis was performed, an mGCS score of 3 or less (p = 0.0013, odds ratio [OR] 10.8), bilateral unreactive pupils (p = 0.0047, OR 31.8), and DI III or IV observed on CT scanning after surgery (p = 0.015, OR 8.9) were independently associated with poor outcome. CONCLUSIONS: Features on CT scans obtained shortly after craniotomy constitute an independent predictor of outcome in patients with traumatic hematoma. Patients in whom DI III or IV appears on postoperative CT scanning, who often present with an mGCS score of 3 or less and nonreactive pupils, are at high risk for the development of raised ICP and lowered CPP.     

Effects of nifedipine on intracranial pressure in neurosurgical patients with arterial hypertension

The effects of nifedipine, 20 mg administered via a nasogastric tube, on intracranial pressure (ICP) and cerebral perfusion pressure (CPP) were examined. Nifedipine was administered to treat arterial hypertension (greater than 180 mm Hg, systolic). Ten measurements were made in eight patients with cerebrovascular disease or head trauma. The mean arterial blood pressure (MABP) and ICP were measured before and for 30 minutes after the administration of nifedipine. The MABP gradually decreased and reached its lowest value at approximately 10 minutes after initiation of nifedipine administration, and thereafter remained unchanged. The MABP decreased significantly from 128 +/- 8 (mean +/- standard deviation) to 109 +/- 7 mm Hg, and the CPP decreased from 105 +/- 11 to 84 +/- 10 mm Hg. The ICP increased by 1 to 10 mm Hg in eight of 10 measurements, and the mean change of ICP from 19 +/- 7 to 22 +/- 6 mm Hg was statistically significant. These changes were not accompanied by alterations in neurological signs. The results suggest that enteral nifedipine produces a small but statistically significant increase in ICP. Accordingly, neurological signs must be closely observed to detect deterioration, which can be caused by an increase in ICP and/or a decrease in CPP.     

Phenylephrine increases cerebral perfusion pressure without increasing intracranial pressure in rabbits with balloon-elevated intracranial pressure.

Using a rabbit model of intracranial hypertension, we studied the effects of infusion of phenylephrine on intracranial pressure (ICP) and cerebral perfusion pressure (CPP). Seven New Zealand white rabbits were anesthetized with isoflurane and normocapnia was maintained. An extradural balloon was used to raise ICP to 25 +/- 1 mm Hg. Infusion of phenylephrine increased mean arterial blood pressure (MAP) (77 +/- 6 --> 95 +/- 8 mm Hg) and CPP (52 +/- 7 --> 70 +/- 7 mm Hg). ICP was unchanged during infusion of phenylephrine (25 +/- 1 vs. 25 +/- 2 mm Hg). The phenylephrine infusion was stopped after 45 minutes and MAP returned to baseline (76 +/- 8 mm Hg). We conclude that phenylephrine increased CPP because of its effect on MAP, but did not alter ICP. Phenylephrine may be used to increase CPP without raising ICP when autoregulation is intact.     

Intracranial pressure responses to PEEP in head-injured patients.

PEEP (positive end-expiratory pressure) was required in 12 head-injured patients in whom intracranial pressure (ICP) monitoring had been previously established. In six, ICP increased by 10 mm Hg or more as 4-8 cm H2O of PEEP were administered. In 10 patients the mean arterial pressure decreased during PEEP. Before PEEP, the mean cerebral perfusion pressure (CPP = BP-ICP) was above 50 mm Hg in all patients. The CPP was less than 50 mm Hg in six patients given PEEP. Neurological deterioration occurred in two patients during PEEP therapy. In head-injured patients, optimal titration of PEEP therapy should include ICP measurement and/or continuous evaluation of neurologic status.