Anesthesia and analgesia
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Anesthesia and analgesia · Jun 1998
Comparative StudyThe effects of propofol on cerebral blood flow velocity and cerebral oxygen extraction during cardiopulmonary bypass.
We investigated the effects of burst-suppression doses of propofol on cerebral blood flow velocity (CBFV), cerebral oxygen extraction (COE), and dynamic autoregulation in 20 patients undergoing cardiac surgery. The experimental procedure was performed during nonpulsatile cardiopulmonary bypass (CPB) with stable hypothermia (32 degrees C) in fentanyl-anesthetized patients. Middle cerebral artery transcranial Doppler flow velocity, right jugular bulb oxygen saturation, and jugular venous pressure (JVP) were continuously measured. Dynamic autoregulation was tested by stepwise changes in mean arterial pressure (MAP) within a range of 40-80 mm Hg by sodium nitroprusside and phenylephrine before (control) and during propofol infusion, with a stable plasma concentration (approximately 9 microg/mL). Propofol induced a 35% decrease in CBFV (P < 0.0001) and a 10% decrease in COE (P < 0.05) compared with control. The slopes of the curves relating CBFV and COE to cerebral perfusion pressure (CPP = MAP - JVP) were less pronounced with propofol (P < 0.01 and P < 0.05, respectively). We conclude that propofol decreases CBFV and improves dynamic autoregulation during moderate hypothermic CPB. Furthermore, during propofol infusion, cerebral blood flow was in excess relative to oxygen demand, as indicated by the decrease in COE. ⋯ In this study, we evaluated the effects of propofol on continuously measured cerebral blood flow velocity (CBFV) and cerebral oxygen extraction as a function of perfusion pressure. Propofol induced 35% and 10% decreases in CBFV and cerebral oxygen extraction, respectively. The slope of the curve relating cerebral perfusion pressure to CBFV decreased with propofol.
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Anesthesia and analgesia · Jun 1998
Randomized Controlled Trial Clinical TrialAdding ketamine in a multimodal patient-controlled epidural regimen reduces postoperative pain and analgesic consumption.
We designed this double-blind study to evaluate the effect of adding small-dose ketamine in a multimodal regimen of postoperative patient-controlled epidural analgesia (PCEA). Ninety-one patients, ASA physical status I-III, undergoing major surgery, received a standardized general anesthesia and epidural catheterization in an appropriate intervertebral space after surgery. A PCEA device was programmed to deliver a regimen of morphine 0.02 mg/mL, bupivacaine 0.8 mg/mL, and epinephrine 4 microg/mL, with the addition of ketamine 0.4 mg/mL (ketamine, n = 45) or without (control, n = 46). The mean visual analog pain scale (VAS) scores during cough or movement for the first 3 days after surgery were higher in the control group than in the ketamine group (P < 0.05), whereas the mean VAS score at rest for the first 2 days were higher in the control group than in the ketamine group (P < 0.05). Furthermore, patients in the control group consumed more multimodal analgesics than patients in the ketamine group for the first 2 days (P < 0.05). The sedation scores and the incidence of side effects (pruritus, nausea, emesis, sleep deprivation, motor block, and respiration depression) were similar between the two groups. We conclude that adding ketamine 0.4 mg/mL in a multimodal PCEA regimen provides better postoperative pain relief and decreases consumption of analgesics. ⋯ Many studies have evaluated one or a combination of two analgesics for postoperative pain control, but few have examined a multimodal approach using three or four different epidural analgesics. This study demonstrates an additive analgesic effect when ketamine is added to a multimodal analgesic treatment.
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Anesthesia and analgesia · Jun 1998
Quantitative analysis of respiratory, motor, and sensory function after supraclavicular block.
The incidence and clinical significance of hemidiaphragmatic paresis after supraclavicular block of the brachial plexus is unknown. Eight healthy volunteers received a supraclavicular block with a standard technique using 30 mL of 1.5% lidocaine. Respiratory function was assessed with ultrasound of the diaphragm, respiratory inductive plethysmography (RIP), and pulmonary function tests (PFT) every 20 min. Sensory block was assessed with pinprick and motor block with isometric force dynamometry every 20 min. Four of eight subjects demonstrated hemidiaphragmatic paresis on both ultrasound and RIP. No subject experienced changes in PFT values or subjective symptoms of respiratory difficulty. Motor and sensory blockade outlasted hemidiaphragmatic paresis. These results are contrasted to the often symptomatic, 100% incidence of hemidiaphragmatic paresis seen after interscalene block. In this study of healthy volunteers, supraclavicular block was associated with a 50% incidence (95% confidence interval 14-86) of hemidiaphragmatic paresis that was not accompanied by clinical evidence of respiratory compromise. ⋯ Interscalene block is always associated with diaphragmatic paralysis and respiratory compromise. The significance of these side effects after supraclavicular block is unknown. Using sensitive measures of respiratory function, we determined that diaphragmatic paralysis occurs less often with the supraclavicular approach and is not associated with respiratory difficulties in healthy subjects.
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Anesthesia and analgesia · Jun 1998
The effect of hydroxyethyl starch on platelet aggregation in vitro.
The effect of hydroxyethyl starch (HES) on hemostasis seems to be minimal when it is used in recommended amounts. A number of studies have investigated the effect of HES on platelet function when administered in vivo, but there has been no study investigating the effect on the isolated platelet function when administered in vitro. A photometrical method to assess platelet function in platelet-rich plasma (approximately 250 x 10(9) platelets/L) was used with platelet aggregation induced using either collagen, epinephrine, adenosine diphosphate, or ristocetin. We found a dose-dependent decrease of platelet aggregation in vitro with either collagen or epinephrine, but not with adenosine diphosphate or ristocetin. However, the changes of HES on platelet aggregation were detected only in doses larger than those routinely used in the clinical setting. Therefore, we conclude that the influence of HES at the recommended doses on initial platelet aggregation may not be clinically relevant. ⋯ The effect of hydroxyethyl starch on platelet function and coagulation is discussed. This study showed no influence on platelets in clinically relevant doses in an in vitro model.
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Anesthesia and analgesia · Jun 1998
The effect of pneumoperitoneum on intraocular pressure in rabbits with alpha-chymotrypsin-induced glaucoma.
Increased intraperitoneal pressure is associated with physiological changes including alterations of intraocular pressure (IOP). We have previously shown that IOP is not adversely affected by increased intraperitoneal pressure up to 15 mm Hg in women with no preexisting eye disease. The aim of this study was to measure IOP changes associated with increased intraperitoneal pressure (up to 15 mm Hg) of 2 h duration in 12 rabbits with alpha-chymotrypsin-induced glaucoma. A reliable model of glaucoma was created by injecting alpha-chymotrypsin into the posterior chamber of the right eye in 12 rabbits. Thereafter, 5 of the 12 rabbits with glaucomatous eyes were treated with topical timolol. The left eye was used as a control. During pentobarbital general anesthesia, increased intraperitoneal pressure up to 15 mm Hg was created by intraperitoneal CO2 insufflation. Body temperature and expired CO2 were kept constant throughout the study. IOP measurements were made using an electronic pneumotonometer. IOP, mean arterial pressure, heart rate, and central venous pressure were recorded in head-up and head-down positions before, during, and after increased intraperitoneal pressure. The IOP of both eyes, in both treated and untreated rabbits, increased significantly from baseline only when increased intraperitoneal pressure associated with the head-down position resulted in a significant increase in central venous pressure. However, the IOP increase remained within the diurnal range. The major finding of this study is that, in a reliable model of glaucoma, CO2 pneumoperitoneum was associated with an increase in IOP when a head-down position was combined with pneumoperitoneum. ⋯ In rabbits with alpha-chymotrypsin-induced glaucoma, increased intraperitoneal pressure (up to 15 mm Hg) resulted in a significant intraocular pressure increase when pneumoperitoneum was associated with the head-down position. However, the intraocular pressure increase remained within the diurnal range.