Desflurane results in higher cerebral blood flow than sevoflurane or isoflurane at hypocapnia in pigs

Comparison of the effect of sevoflurane and propofol on the optic nerve sheath diameter in patients undergoing middle ear surgery

PURPOSE

During middle ear surgery, the patient's head is turned away from the surgical site, which may increase the intracranial pressure. Anesthetics also affect the intracranial pressure. The optic nerve sheath diameter (ONSD) measured using ultrasonography is a reliable marker for estimating the intracranial pressure. This aim of this study was to investigate the effect of sevoflurane and propofol on the ONSD in patients undergoing middle ear surgery.

METHODS

Fifty-eight adult patients were randomized into sevoflurane group (n = 29) or propofol group (n = 29). The ONSD was measured using ultrasound after anesthesia induction before head rotation (T0), and at the end of surgery (T1). The occurrence and severity of postoperative nausea and vomiting (PONV) were assessed 1 h after the surgery.

RESULTS

The ONSD was significantly increased from T0 to T1 in the sevoflurane group [4.3 (0.5) mm vs. 4.9 (0.6) mm, respectively; P < 0.001] and the propofol group [4.2 (0.3) mm vs. 4.8 (0.5) mm, respectively; P < 0.001]. No significant difference was observed in the ONSD at T0 (P = 0.267) and T1 (P = 0.384) between the two groups. The change in the ONSD from T0 to T1 was not significantly different between the sevoflurane and propofol groups [0.6 (0.4) mm vs. 0.6 (0.3) mm, respectively; P = 0.972]. The occurrence and severity of PONV was not significantly different between the sevoflurane and propofol groups (18% vs. 0%, respectively; P = 0.053).

CONCLUSION

The ONSD was significantly increased during middle ear surgery. No significant difference was observed in the amount of ONSD increase between the sevoflurane and propofol groups.

Effects of pneumoperitoneum and patient position on intracranial pressure in obese patients undergoing laparoscopic cholecystectomy

Background/Aim: Optic nerve sheath diameter (ONSD) measurement is one of the non-invasive techniques used for intracranial pressure (ICP) measurement. ICP changes have been evaluated based on ONSD measurements during many laparoscopic surgeries. However, such analyses in the obese patient populations are limited. This study aimed at investigating the effects of pneumoperitoneum and reverse Trendelenburg and head-up position on ICP based on ONSD measurements in obese patients undergoing laparoscopic cholecystectomy. Methods: This observational study included 60 female patients who were scheduled for laparoscopic cholecystectomy. Obese patients with a body mass index (BMI) of 30 and above were assigned to Group 1, while BMI < 30 patients were assigned to Group 2. The first ONSD measurement was performed just before insufflation (T1). The second measurement was taken 5 min after insufflation (T2), the third measurement 5 min after placing patients in the reverse Trendelenburg and head-up position (T3), and the last measurement 5 min after the deflation while the reverse Trendelenburg and head-up position was maintained (T4). Results: ONSD measurements at the T2 and T3 time points in Group 1 patients were higher than in Group 2 patients (P = 0.012 versus P = 0.020). Both measurement values were higher in obese patients. In Group 1 patients, T2 and T3 measurements were significantly higher than T1 and T4 measurements (T2 > T1; P < 0.001, T2 > T4; P < 0.001, T3 > T1; P < 0.001, and T3 > T4; P < 0.001). No significant difference between T2 and T3 and between T1 and T4 measurements were found. In Group 2 patients, T2 measurements were significantly higher than the T1, T3, and T4 measurements, while T3 measurements were significantly higher than T1 and T4 measurements (T2 > T1; P < 0.001, T2 > T3; P = 0.022, T2 > T4; P < 0.001, T3 > T1; P < 0.001, and T3 > T4; P = 0.048). No significant difference between T1 and T4 measurements was noted. Conclusion: Laparoscopic cholecystectomy does not cause an increase in ICP of obese patients with limited pneumoperitoneum pressure, reverse Trendelenburg and head-up position, and controlled anesthesia.

The use of desflurane for neurosurgical procedures in rhesus macaque ( Macaca mulatta)

Volatile agents are widely used to anaesthetise laboratory non-human primates as they allow a rapid induction and recovery as well as an easy adjustment of the anaesthesia plan. Desflurane is currently the volatile agent with the lowest solubility in blood, and hence enables the most rapid onset of anaesthesia and most rapid recovery. This study aimed to investigate the suitability of desflurane for maintenance of general anaesthesia in rhesus macaques undergoing elective experimental neurosurgery. Fourteen primates (five males and nine females) were sedated with ketamine (10 mg kg^-1) and anaesthesia was induced with propofol (usually 8 mg kg^-1 IV). Anaesthesia was maintained with desflurane (5.9 ± 0.8 %) and alfentanil (0.2-0.5 µg kg^-1 min^-1 IV). Animals were mechanically ventilated. Meloxicam (0.3 mg kg^-1) and methylprednisolone infusion (5.4 mg kg^-1 h^-1) were also administered. All the primates were successfully anaesthetised and no severe complications related to the procedure or the anaesthesia regimen occurred. No major differences in physiological parameters and recovery times between the male and female groups were found. Emergence from anaesthesia was rapid (male 5.2 ± 2.4 min; female 4.1 ± 1.7 min) but its quality was assessed as equivalent to two other volatile anaesthetics, isoflurane and sevoflurane. These had previously been assessed for neuroanaesthesia in rhesus macaques. In conclusion, this study demonstrated that desflurane was suitable for maintenance of general anaesthesia for elective experimental neurosurgical procedures in rhesus macaque. However the vasodilatory action of the desflurane may limit its use in cases of severe intracranial hypertension or systemic hypotension.

Effects of Volatile Anesthetics on Oral Tissue Blood Flow in Rabbits: A Comparison Among Isoflurane, Sevoflurane, and Desflurane

PURPOSE

The aim of this study was to compare the concentration-dependent effects of isoflurane, sevoflurane, and desflurane on oral tissue blood flow.

MATERIALS AND METHODS

Thirty male Japan White rabbits were randomized to receive 1 of 3 volatile anesthetics: isoflurane (group Iso), sevoflurane (group Sevo), or desflurane (group Des). The end-tidal concentration of each volatile anesthetic was regulated to 0.5, 1, and 1.5 minimum alveolar concentrations (MACs). The observed variables were heart rate, systolic blood pressure, diastolic blood pressure, mean arterial pressure, common carotid arterial blood flow, tongue mucosal blood flow, mandibular bone marrow blood flow (BBF), masseter muscle blood flow (MBF), upper alveolar tissue blood flow, and lower alveolar tissue blood flow (LBF).

RESULTS

The blood pressure in each group tended to decrease depending on the concentration of each volatile anesthetic, with the smallest effect in group Des. BBF and MBF in group Iso were higher than those in group Des at 1 MAC, and MBF and LBF in group Iso were highest at 1.5 MAC.

CONCLUSION

The results of this study suggest that each volatile anesthetic produced unique effects on blood flow in oral tissues and circulatory parameters. Among the 3 volatile anesthetics, desflurane produced the smallest effects on oral tissue blood flow.

Increase in intracranial pressure during carbon dioxide pneumoperitoneum with steep trendelenburg positioning proven by ultrasonographic measurement of optic nerve sheath diameter

PURPOSE

The purpose of this study was to assess the extent of the increased intracranial pressure (ICP) resulting from CO2 pneumoperitoneum and steep Trendelenburg positioning using ultrasonographic measurement of optic nerve sheath diameter (ONSD) in patients undergoing robot-assisted laparoscopic radical prostatectomy (RALRP).

PATIENTS AND METHODS

Twenty patients who underwent elective RALRP were enrolled in this study. ONSD and regional cerebral oxygen saturation (rSO2) were investigated noninvasively using ocular ultrasonography and near-infrared spectroscopy before anesthesia (T0), 10 minutes after anesthesia induction in the supine position (T1), 10 and 30 minutes after CO2 pneumoperitoneum with 30-degree Trendelenburg positioning (T2 and T3), and after returning to supine position without CO2 pneumoperitoneum at the conclusion of the RALRP (T4).

RESULTS

The mean values of ONSD at all time points (T1, T2, T3, and T4) after general anesthesia significantly increased compared with that before general anesthesia (T0). During CO2 pneumoperitoneum with 30-degree Trendelenburg positioning (T2, T3), a significant increase of 12.5% in ONSD was observed in comparison with ONSD after anesthesia induction in the supine position without CO2 pneumoperitoneum (T1). Three patients had an ONSD value equivalent to an ICP above 20 mm Hg, and these patients did not experience a decrease of rSO2 or any neurologic complications.

CONCLUSIONS

In patients undergoing RALRP, the increase of 12.5% in ONSD during CO2 pneumoperitoneum with steep Trendelenburg positioning was observed and thus the increase of ICP corresponding to this change of ONSD could be predicted. In 15% of the enrolled patients, ONSD increased by values equivalent to an ICP above 20 mm Hg without a deterioration of rSO2 or any neurologic complications.

Dose-dependent influence of sevoflurane anesthesia on neuronal survival and cognitive outcome after transient forebrain ischemia in Sprague-Dawley rats

BACKGROUND

Volatile anesthetics reduce postischemic neurohistopathological injury and improve neurological outcome in various animal models. However, the isoflurane concentrations above 1 minimum alveolar concentration (MAC) have been associated with reduced neuronal survival and impaired functional outcome. The aim of this study was to evaluate if 1.8 MAC sevoflurane alters postischemic neuronal survival and neurologic outcome compared with 0.45 MAC sevoflurane.

METHODS

In this study, 20 fasted male Sprague-Dawley rats were randomly assigned to treatment groups with 1 or 4 vol.% sevoflurane end-tidal concentration. Cerebral ischemia was induced by bilateral carotid artery occlusion and hemorrhagic hypotension (BCAO). The cognitive outcome was assessed after 7 days using the object recognition test. Animals were then re-anesthetized and brains were removed for neurohistopathological analysis of the hippocampus (CA1) and cortex using hematoxylin-eosin staining.

RESULTS

Physiologic parameters were not different between both the treatment groups. The number of viable neurons (median [Q1, Q3]) in the CA1 region on postischemic day 7 was increased after high-dose sevoflurane compared with low-dose sevoflurane (1645 [453, 1825] vs. 3222 [2920, 3993] neurons/ROI, P < 0.05). Results of the object recognition test were not different between both the treatment groups.

CONCLUSIONS

Postischemic neuronal survival was increased with 1.8 MAC compared with 0.45 MAC sevoflurane. Therefore, experimental models of cerebral ischemia should account for neuroprotective effects of sevoflurane with increasing concentrations. To ensure minimal interference of sevoflurane on neuronal survival, a low inspired concentration should be used and fluctuations in the depth of anesthesia should be limited.

Dose effect of sevoflurane and isoflurane anesthetics on cortical blood flow during controlled hypotension in the pig

BACKGROUND

The ability of the brain to preserve adequate cerebral blood flow (CBF) during alterations in systemic perfusion pressure is of fundamental importance. At increasing concentrations, isoflurane and sevoflurane have been known to alter CBF, which may be disadvantageous for patients with increased intracranial pressure. The aim was to examine the effects of isoflurane and sevoflurane at increasing minimum alveolar concentrations (MAC) on CBF, during controlled hypotension.

METHODS

We studied eight pigs during variations in perfusion pressure induced by caval block (100, 60, 50, and 40 mmHg) under normocapnia. CBF was measured locally in a defined area (4 x 5 measurement points covering 1 cm(2)) of the motor cortex using laser Doppler perfusion imaging. Physiological variables, assessed by analysis of arterial O(2) and CO(2), hemoglobin and hematocrit, were controlled. CBF was measured during propofol (10 mg x kg(-1)x h(-1)) and fentanyl (0.002 mg x kg(-1)x h(-1)) anesthesia, and then during anesthesia with either isoflurane or sevoflurane (given in random order) at increasing MAC (0.3-1.2). After a washout period, the measurements were repeated with the other gas.

RESULTS

CBF was significantly higher in the cortex during normotensive (control) settings, MAP approximately 100 mmHg, compared with during hypotension (MAP 40-60 mmHg). Neither different anesthetic nor MAC or local measurement sites were found to influence CBF at any perfusion pressure.

CONCLUSION

In this experimental model, the effect of hypotension on CBF was not altered by the anesthetics used [isoflurane, sevoflurane (MAC 0.3-1.2) or propofol (10 mg x kg(-1)x h(-1))]. In this aspect (cortical tissue perspective), these volatile agents appear as suitable as propofol for neurosurgical anesthesia for patients at risk.

Inhalational or intravenous anesthetics for craniotomies? Pro inhalational

PURPOSE OF REVIEW

In neurosurgery, anesthesiologists and surgeons focus on the same target - the brain. The nature of anesthetics is to interact with brain physiology, leading to favorable and adverse effects. Research in neuroanesthesia over the last three decades has been dedicated to identifying the optimal anesthetic agent to maintain coupling between cerebral blood flow and metabolism, keep cerebrovascular autoregulation intact, and not increase cerebral blood volume and intracranial pressure.

RECENT FINDINGS

Sevoflurane is less vasoactive than halothane, enflurane, isoflurane, or desflurane. The context sensitive half-life is short and similar to that of desflurane, which translates into fast on and offset. Compared with propofol, sevoflurane decreases cerebral blood flow to a lesser extent, while cerebral metabolism is suppressed to the same degree. Sevoflurane does not increase intracranial pressure, while propofol decreases intracranial pressure.

SUMMARY

In neurosurgical patients with normal intracranial pressure, sevoflurane might be a good alternative to propofol. In patients with reduced intracranial elastance, caused by space occupying lesions, with elevated intracranial pressure or complex surgical approaches, propofol should remain first choice.

Desflurane induces more cerebral vasodilation than isoflurane at the same A-line autoregressive index level

BACKGROUND

Clinical use of desflurane in neuroanesthesia remains under debate. Comparison of dose-dependent vasodilatory properties between desflurane and isoflurane, the more traditional volatile agent for clinical neuroanesthesia, requires equianesthetic dosing of the agents. Reproducible neurophysiological measurements of the level of anesthesia in an individual, e.g. the A-line autoregressive index (AAI), can be used for an equipotent dosage of two volatile agents in the same individual.

METHODS

Desflurane and isoflurane, in randomized order, were titrated to a stable AAI level of 15-20 in 18 ASA I or II patients. The mean flow velocity (Vmca) and pulsatility index (PI) in the middle cerebral artery were then measured with transcranial Doppler at an end-tidal CO(2) concentration of 4.4%.

RESULTS

For desflurane Vmca was 11% higher [95% confidence interval (CI), 5-18%; P = 0.0020] and PI was 13% lower (95% CI, 3-23%; P = 0.0083) than for isoflurane. The mean arterial blood pressure did not differ between the agents. The fraction of MAC necessary for the intended AAI level was 35% lower (95% CI, 20-49%; P = 0.00016) with desflurane than with isoflurane.

CONCLUSION

Desflurane was associated with more cerebral vasodilation than isoflurane at the same depth of anesthesia, as indicated by the AAI. This attributes further reason for caution in the use of desflurane in clinical neuroanesthesia. The difference between desflurane and isoflurane in the MAC fractions required for the same AAI level confirms the limitations of MAC in defining the level of anesthesia.

Managing elevated intracranial pressure

PURPOSE OF REVIEW

Elevated intracranial pressure is one of the major deteriorating factors in patients with intracerebral lesions. Therefore, every year many experimental and clinical studies are performed to identify the best method for managing elevated intracranial pressure in head-injured patients. The current review summarizes the most important recent findings for the treatment of increased intracranial pressure.

RECENT FINDINGS

The currently most discussed treatments of elevated intracranial pressure are the use of hypertonic saline, which seems to be equal to mannitol, the use of hypothermia, and the performance of decompressive craniectomy.

SUMMARY

The treatment strategy to manage increased intracranial pressure includes decisions about anaesthetics, ventilation, head and body position, hypothermia, the use of osmotic drugs and surgical procedures. Propofol seems to be suitable for the sedation of patients with elevated intracranial pressure. Sudden increases in intracranial pressure can be treated using hyperosmotic agents, high-dose thiopental, or short episodes of mild hyperventilation. Surgical decompression of the cranium seems to improve the outcome in patients below the age of 50 years, especially children.