Deliberate hypotension

Perioperative Management of Antiplatelet Therapy in Ophthalmic Surgery

Many patients undergoing ophthalmic surgery are elderly with comorbidities requiring antiplatelet therapy to prevent thromboembolic or atherothrombotic events. The use of antiplatelet therapy has expanded over the years, predisposing these patients to hemorrhagic complications perioperatively. The risk of hemorrhagic complications must be weighed against the risk of thromboembolic events with cessation of antiplatelet therapy. The decision to continue or interrupt antiplatelet therapy in the setting of ophthalmic surgery is based upon various factors, including the type of surgery and each patient’s comorbidities. This review examines the risks of thrombotic complications versus hemorrhagic complications in different types of ophthalmic surgeries with the use of antiplatelet medications and provides evidence-based recommendations regarding perioperative management of antiplatelet therapy

Peri-operative management of ophthalmic patients taking antithrombotic therapy

Increasing number of patients presenting for ophthalmic surgery are using oral anti-coagulant and anti-platelet therapy. The current practice of discontinuing these drugs preoperatively because of a presumed increased risk of bleeding may not be evidence-based and could pose a significant risk to the patient's health. To provide an evidence-based review on the peri-operative management of ophthalmic patients who are taking anti-thrombotic therapy. In addition, we briefly discuss the underlying conditions that necessitate the use of these drugs as well as management of the operative field in anti-coagulated patients. A semi-systematic review of literature was performed. The databases searched included MEDLINE, EMBASE, database of abstracts of reviews of effects (DARE), Cochrane controlled trial register and Cochrane systematic reviews. In addition, the bibliographies of the included papers were also scanned for evidence. The published data suggests that aspirin did not appear to increase the risk of serious postoperative bleeding in any type of ophthalmic surgery. Topical, sub-tenon, peri-bulbar and retrobulbar anaesthesia appear to be safe in patients on anti-thrombotic (warfarin and aspirin) therapy. Warfarin does not increase the risk of significant bleeding in most types of ophthalmic surgery when the INR was within the therapeutic range. Current evidence supports the continued use of aspirin and with some exceptions, warfarin in the peri-operative period. The risk of thrombosis-related complications on disruption of anticoagulation may be higher than the risk of significant bleeding by continuing its use for most types of ophthalmic surgery.

The effects of desflurane and propofol-remifentanil on postoperative hepatic and renal functions after right hepatectomy in liver donors

Various volatile anesthetics have been used in hepatectomy in living donors, and their effects on major organs have been extensively evaluated. However, the impact of total intravenous anesthesia (TIVA) on postoperative liver and renal functions after large liver resections has been less extensively investigated than that of volatile agents. The aim of this study was to compare the postoperative hepatic and renal functions between volatile anesthesia with desflurane and TIVA with propofol-remifentanil in living donors undergoing right hepatectomy. Seventy adult patients were randomly allocated into 2 groups: the desflurane group (n = 35) and TIVA group (n = 35). Aspartate aminotransferase, alanine aminotransferase, prothrombin time (PT), albumin, total bilirubin (TB), blood urea nitrogen (BUN), creatinine (Cr), BUN/Cr ratio, estimated glomerular filtration rate (GFR), platelet count, and hemoglobin levels were analyzed in the preoperative period, immediately after the operation, and on the first, second, third, fifth, seventh, and thirtieth postoperative days (PODs). Most of the liver function test results were not significantly different between the 2 groups. However, PT (international normalized ratio) and TB were significantly greater on POD 5 in the TIVA group. Among the renal function tests, Cr was significantly higher and estimated GFR was significantly lower on POD 1 in the TIVA group. The platelet counts and hemoglobin levels were similar between the 2 groups. In conclusion, the results of our study suggest that living related donors for liver transplant may have a better outcome following anesthesia with desflurane. However, further testing will be necessary to prove this hypothesis.

Dominant frequency analysis of EEG reveals brain's response during injury and recovery

A new method of monitoring an analyzing electroencephalogram (EEG) signals during brain injury is presented. EEG signals are modeled using the autoregressive (AR) technique to obtain the frequencies where there are peaks in the spectrum. The powers at these dominant frequencies are analyzed to reveal the state of brain injury during an experimental study involving progressive hypoxia, asphyxia, and recovery. Neonatal piglets (n = 8) were exposed to a sequence of 30 min of hypoxia (10% oxygen), 5 min of room air, and 7 min of asphyxia. They then received cardiopulmonary resuscitation and were subsequently monitored for 4 h. An optimal AR model order of six was obtained for these data, resulting in three dominant frequencies. These dominant frequencies, referred to as the low, medium, and high frequency components, fell in the bands 1.0-5.5 Hz, 9.0-14.0 Hz, and 18.0-21.0 Hz, respectively. A remarkable feature of our data is the spectral dispersion, or diverging trends in the three frequency bands. During hypoxia, the relative powers of the medium and high-frequency components of EEG increased up to 160% and 176%, from their respective baseline values. During the first minute of asphyxia the medium- and high-frequency powers (relative to baseline) increased by 280-400%. The power in three frequency components went down to nearly zero within 40-80 s of asphyxia. During recovery, the phenomenon of burst-suppression was clearly exhibited in the low-frequency component. A new index, called mean normalized separation, representing the degree of disproportionality in the recovery of powers of the three dominant components relative to their mean recovered power, is presented as a possible single indicator of electrical function recovery. In conclusion, dominant frequency analysis helps reveal the brain's graded electrical response to injury and recovery.

Estimating anesthetic depth by electroencephalography during anesthetic induction and intubation in patients undergoing cardiac surgery

Intravenous (IV) anesthesia titrated to continuous computer-processed electroencephalograms (EEGs) was studied in 32 consecutive patients undergoing cardiac surgery. Anesthesia was induced with fentanyl 50 micrograms/kg with no EEG monitoring (n = 16) or 25 to 50 micrograms depending on changes in EEG (n = 16). EEG, oxygen saturation by pulse oximeter, intra-arterial blood pressure (BP), central venous pressure (CVP), and pulmonary artery pressure (PAP) (n = 18) were monitored continuously. Cardiac output (CO), CVP, PAP, spectral-edge frequency for each hemisphere, and BP were recorded before induction, immediately before intubation, and 1 and 5 minutes after intubation. With EEG monitoring, intubation was performed when spectral-edge frequency decreased to 10 Hz or less. Recall and pain were investigated 2 to 12 weeks postoperatively. With EEG, the amount of fentanyl used before intubation was significantly lower (39.7 +/- 2 micrograms/kg; p less than 0.005) than without EEG (50 micrograms/kg). The decrease in BP (% change) was less with than without EEG; mean changes in BP between preinduction and preintubation were -7.4% +/- 3.8% and -16.5% +/- 3.1% and between preinduction and 1 minute after intubation 0.3% +/- 3.4% and -12.5% +/- 3.5%, respectively. Percent changes in mean BP between intubation and 1 minute after were 9.6% +/- 4.0% with EEG and 5.2% +/- 3.0% without EEG. No patient in either group had recall. The authors conclude that using EEG monitoring to estimate depth of anesthesia during induction and laryngoscopy may increase safety in high-risk patients undergoing cardiac surgery.

Surgical management of vascular malformations of the head and neck

The evaluation and treatment of non-involuting hemangiomas with arteriovenous components and arteriovenous malformations of the head and neck remain difficult. Surgical excision is still the most important and effective method of controlling these lesions. Radiotherapy should never be used. It is ineffective, dangerous, and often complicates any later operation that may be required. Evaluation of vascular malformations with computerized tomography, arteriography, magnetic nuclear imaging, and Doppler mapping will aid diagnosis. Adjunctive hypotensive anesthesia, intraoperative embolization with Gelfoam, and temporary peripheral suture ligations have made the surgical task more manageable. The integration of reconstructive techniques into the surgical program is essential if optimum results are to be obtained. Incisions must be planned so that future flap patterns are preserved. Axial vessels may be needed later. Fascial slings, muscle transfers, nerve grafts, and tissue expansion of adjacent normal tissue may be needed to maintain and restore function and features. Above all, the treatment of each patient requires individual planning. The most common errors in the treatment of vascular hemangiomas result from missed diagnoses and faint-heartedness in tackling the surgical removal of such highly vascular tumors. Many patients go for years without finding a surgeon who will help them. We believe that aggressive surgical treatment offers much to many of these patients.

[Plasma renin activity and prostaglandin E2 in hypotension induced by nicergoline]

The hypotensive actions of nicergoline, a new alpha 1-adrenoreceptor blocking agent, were studied in six dogs during stable anaesthesia under mechanical ventilation. Systemic haemodynamic parameters were measured before the infusion of nicergoline (500 micrograms X kg-1 in 5 min), and regularly after it during 2 h. Plasma renin activity (PRA), right atrial (V PGE2) and arterial (A PGE2) prostaglandin E2 concentrations measured by radio-immunoassay were collected before, and 10 and 20 min after nicergoline infusion. The mean aortic pressure fell to its lowest figure (-30%) at the 5th min, this being maintained for 45 min. Heart rate and cardiac output remained unchanged. Pulmonary wedge pressure (p less than 0.01) and central venous pressure (p less than 0.05) decreased. All parameters reached their control values in 120 min. PRA was unchanged. V PGE2 (p less than 0.01) and pulmonary extraction in PGE2 (V PGE2 - A PGE2/V PGE2) (p less than 0,05) increased whilst A PGE2 was unmodified. The fall in mean aortic pressure was linked (p less than 0.001) to the increase in V PGE2. Nicergoline infusion induced hypotension by reducing vascular tone of resistance and capacitance beds. Hypotension was related to the vasoplegia and to an inhibition of the rapid pressor control mechanisms. The reasons for the lack of renin release were unknown. V PGE2 release was stimulated by the hypotension. The increase in pulmonary extraction in PGE2 was involved in the maintenance of A PGE2 concentration. Nicergoline gave mild hypotension without reflex sympathetic activation. Its alpha-adrenoreceptor blocking properties were similar to those of prazosin.(ABSTRACT TRUNCATED AT 250 WORDS)