Changes in the intracranial pressure dynamics with head-down tilt in cats

To determine changes in the intracranial pressure dynamics under the condition of head-down tilt, the pressure-volume relationship in the cranial cavity as well as changes in intracranial pressure were studied experimentally in 31 cats. The animals were divided into three groups; with the horizontal, with the head-down and one with the head-up position. In each group the pressure volume index (PVI) and cranial cavity compliance (C) were examined under controlled respiration. The following results were obtained. (1) The values of PVI and C were significantly greater in the head-down tilt group as compared to those in the other groups, in spite of the increase in intracranial pressure level. (2) In the situations of craniospinal blockade by epidural ligation of spinal cord at C2 level, the PVI and C were also higher in the head-down tilt group than in the horizontal group. These results indicate that the pressure buffering capacity is increased with head-down tilt with respect to intracranial volume loading. It appears that the buffering mechanism does not depend on movement of the cerebrospinal fluid, but on the increased cerebral venous vascular bed with the communication between extracranium and intracranium.     

Effect of sevoflurane on intracranial pressure, sagittal sinus pressure, and the intracranial volume-pressure relation in cats

The effect of sevoflurane on intracranial pressure (ICP), sagittal sinus pressure (SSP), and the intracranial volume-pressure (V-P) relation was examined in cats. In experiment 1, on nine cats, changes in ICP and SSP were studied for 180 min during anesthesia with 1 MAC sevoflurane (2.6%, inspired) and 50% nitrous oxide (N2O) in oxygen (O2). ICP significantly (p <0.01) increased from 8.4 +/- 3.8 cm H2O (mean +/- SD), the control level to 10.6 +/- 5.1 cm H2O immediately after the administration of sevoflurane. ICP was unchanged for the subsequent 120 min but then increased significantly (p <0.05) 140 min after administration, being 15.5 +/- 9.0 cm H2O at 180 min. There were no changes in SSP or blood gases. In experiment 2, the rapid injection technique of mock cerebrospinal fluid was used to determine the intracranial V-P relation in ten cats. Measures of V-P relationships included (a) ICP before volume injection (Po), (b) peak ICP caused by volume injection (Pp), (c) intracranial compliance (C) calculated as the ratio of change of intracranial volume Delta V) to change of ICP (Delta P), and (d) the pressure volume index (PVI) calculated as the ratio of Delta V to log Pp/Po. The subjects were divided into two groups, one administered 2.6% sevoflurane and 50% N2O in O2 (n = 6) and the other 50% N2O in O2 (n = 4). Each cat in both groups was given two bolus injections into the lateral ventricle at 180 min after the start of anesthesia. Then, C and PVI were calculated. C and PVI in the group treated with sevoflurane were significantly (p <0.05) lower than in the other group. These findings suggest that prolonged use of sevoflurane increases the intracranial elastance.     

The effect of increased intracranial pressure on pressure in the superior sagittal sinus

Summary It is difficult to explain why rises in ICP provoke different types of response in superior sagittal sinus pressure. In most of our experimental animals there was close correlation between rises in ICP and SSSP. In the remainder, SSSP showed little increase when ICP rose. The animals with marked increase in SSSP showed a greater capacity for compensation for increased amounts of intracranial fluid.     

Intraocular pressure profile during general anesthesia

The effect of some anesthetic drugs on intraocular pressure (IOP) was studied in 120 normal healthy patients undergoing non-ophthalmic surgical procedures. IOP rose significantly following the injection of succinylcholine (SCh) alone, or when such injection had been preceded by a pretreatment with a "self-taming" dose of SCh or d-tubocurarine (d-Tc). Though the rise in IOP after diazepam pretreatment was significant, the magnitude was lower than that observed in the groups pretreated with the other two agents. Halothane brought the IOP down faster and lower than ether. SCh is unsafe for intubation for the administration of general anesthesia in cases involving penetrating ocular injuries. It can, however, be used safely for routine ophthalmic surgery, providing that 8 minutes are allowed to elapse between injection and corneal or scleral incision. Halothane is preferred to ether, since the former lowers IOP faster and in a greater amount than the latter.     

Effect of spinal versus general anesthesia on bladder compliance and intraabdominal pressure during transurethral procedures.

STUDY OBJECTIVE: To evaluate the influence of spinal versus general anesthesia on bladder compliance and intraabdominal pressure in elderly males undergoing elective transurethral resection of the prostate. DESIGN: Prospective, randomized, open-label study. SETTING: Teaching hospital. PATIENTS: 21 ASA physical status I, II, and III patients at least 18 years of age, undergoing transurethral surgery. INTERVENTIONS: According to a computer-generated randomization schedule, patients were allocated to one of two groups. In Group Spinal (S), 10 mg of hyperbaric tetracaine was administered intrathecally. In Group General Anesthesia (GA), patients received, fentanyl intravenous (i.v. 1 to 2 micrograms/kg and propofol i.v. 1.0 to 2.0 mg/kg for induction of anesthesia. Thereafter, a laryngeal mask airway was inserted and, with spontaneous ventilation, anesthesia was maintained by administering isoflurane (end-tidal 0.7% to 1.2%) and 70% nitrous oxide (N2O) in oxygen. Intraabdominal pressure and bladder compliance were recorded prior to the induction of anesthesia and immediately before the onset of the surgical procedure. MEASUREMENTS AND MAIN RESULTS: The two groups were demographically comparable. In Group S, mean bladder compliance was significantly (p = 0.003) higher and mean intraabdominal pressure significantly lower (p = 0.007) when compared to baseline preanesthetic values. In Group GA, mean intraabdominal pressure significantly (p = 0.006) decreased when compared to baseline preanesthetic recordings. Following the induction of general anesthesia, a small change in bladder compliance was noted. However, statistical significance was not reached. Data were analyzed and compared using Student's t-test (p < 0.05 was considered statistically significant). CONCLUSION: Both spinal and general anesthesia induced a significant decrease in intraabdominal pressure. While both techniques were associated with an increase in bladder compliance, statistical significance was demonstrated only in the spinal anesthesia treatment group.     

Endotracheal tube cuff pressure. Monitoring during general anesthesia

BACKGROUND: To value changes of endotracheal tube cuff pressure during anaesthesia with N2O, using standard tubes or Brandt-system tubes. METHODS: Endotracheal cuff pressure during anaesthesia in three groups of patients has been monitored: Group 1 (n. 41): endotracheal tube with low-pressure cuff using N2O/O2 (2:1 or 1:1); Group 2 (n. 55): Brandt's double cuff-tubes using N2O/O2 (2:1 or 1:1); Group 3 (n. 20-control group): tubes with low-pressure cuff using O2/air. Values of pressure (M +/- DS: p < 0.05) have been compared with ANOVA, Bonferroni's method (p < 0.017). RESULTS AND CONCLUSIONS: Brandt's double cuff-tubes (G2) succeed in avoiding uncontrolled increase of cuff-pressure during anaesthesia with N2O. Standard low-pressure tubes (G1) shown increase of cuff pressure during anaesthesia with N2O which is absent using no N2O (G3).     

Effect of alfentanil on intracranial pressure during propofol-fentanyl anesthesia for craniotomy. A randomized prospective dose-response study

BACKGROUND: The effect of alfentanil on intracranial pressure (ICP) in patients with supratentorial cerebral tumors has only been sparsely examined and with somewhat contradictory results. METHODS: Thirty-one patients were anesthetized with propofol and fentanyl. After removal of the bone flap a bolus-dose of alfentanil 10 (group 1), 20 (group 2), or 30 microg kg(-1) (group 3) was administered followed by an infusion of 10, 20, or 30 microg.kg(-1).h(-1) to patients in groups 1, 2, and 3, respectively. A control group received no alfentanil. Subdural ICP, mean arterial blood pressure (MAP), and cerebral perfusion pressure (CPP) were monitored and arterial and jugular bulb blood were sampled before and every minute for 5 min after the bolus administration of alfentanil and again after 5 min of hyperventilation to be able to calculate cerebral arterio-venous oxygen content difference (AVDO2) and carbon dioxide reactivity (CO2-reactivity). Results: No changes in subdural ICP or AVDO2 from alfentanil in the study period were observed within the groups. However, alfentanil decreased MAP and CPP. The maximum CPP decrease (mean value of each group) was 4 mmHg, 8 mmHg, and 18 mmHg in groups 1, 2, and 3, respectively. There was no difference between groups as regards the CO2-reactivity. Conclusion: We conclude that administration of alfentanil to propofol-fentanyl anesthetized patients with supratentorial cerebral tumors decreases MAP and CPP in a dose-related way, but does not influence subdural ICP, AVDO2 or the CO2-reactivity.     

Effect of diltiazem-induced hypotension on normal and increased intracranial pressure of cats

The commonly used vasodilators sodium nitroprusside and nitroglycerin increase intracranial pressure (ICP) and cause tachycardia. Since diltiazem is also a vasodilator, we designed this experiment in cats to study its effect on intracranial pressure and heart rate (HR). Twelve cats were assigned to two equal groups. One group had normal ICP (N-ICP), while in the other the ICP was raised artificially (AR-ICP) by placing a balloon into the intracranial extradural space. Both groups received an infusion of diltiazem to decrease the mean blood pressure (BP), which was maintained 30 per cent below the baseline value for 15 minutes. Diltiazem caused no significant change in ICP (5.7 +/- 1 to 6.7 +/- 1.5 mmHg, p less than 0.01) in cats with N-ICP while in cats with AR-ICP, the increase from 26.9 +/- 0.5 to 34.0 +/- 1.9 mmHg was significant (p less than 0.006). HR decreased significantly during the diltiazem infusion in both groups.     

盐酸戊乙奎醚对全麻患者肺胸顺应性的影响

目的研究盐酸戊乙奎醚对全麻机械通气患者肺胸顺应性(Comp)的影响。方法40例ASAⅠ级拟行气管插管全身麻醉的择期手术患者,随机均分为观察组和对照组。所有患者诱导前静脉注射咪唑安定0.03 mg/kg,以丙泊酚2～2.5 mg/kg、芬太尼3μg/kg、维库溴铵0.1 mg/kg静脉诱导;采用压力控制机械通气使呼气末二氧化碳分压(PETCO2)维持在正常范围;丙泊酚、维库溴铵持续输注维持麻醉。诱导后20 min,观察组静脉给予盐酸戊乙奎醚0.02 mg/kg,对照组给予生理盐水。监测给药前(T0)、给药后5 min(T5)、10 min(T10)、20 min(T20)、30 min(T30)的HR、MAP、SpO2、PETCO2、潮气量(VT)、Comp和T0、T30时的血气分析。结果两组HR、MAP差异无统计学意义。T5、T10、T20、T30时观察组VT、Comp均明显高于T0时(P<0.05或P<0.01),T20、T30时观察组的VT明显高于对照组(P<0.05)。结论对于全麻患者,盐酸戊乙奎醚可以扩张支气管,改善Comp且对血流动力学无明显影响。     

Effects of intracranial pressure on frontal sinus development

Through a study of some syndromes of intra-cranial high and low pressure, the authors try to find out the relations between the intra-cranial stresses and the development of frontal sinuses. They account for the choice of frontal sinuses and the various factors determining this pneumatization. They study the morphology of the frontal sinuses in 20 cases of old and chronic hydrocephaly, in 13 cases of oxycephaly with a late diagnosis, and in 20 cases of adults suffering with infantile cerebral hemiatrophy. They show that in these syndromes, the development of frontal sinuses is an inverse ratio to the intracranial pressure. However, they point out that in standard people, the extreme differences in the morphology of their frontal pneumatization can be explained not only by various causes--a number of which is as yet not known--but also by an aleatory distribution.