Intraoperative monitoring in patients with moyamoya disease.
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Brain↗
Biomedical subjects
D H Wong
Publications and source records attributed to D H Wong.
Lateral popliteal sciatic nerve block compared with ankle block for analgesia following foot surgery.
The purpose of this study was to compare postoperative analgesia after foot surgery in patients anaesthetised either with popliteal sciatic nerve block or ankle block. In a prospective study, 40 patients scheduled for foot surgery involving osteotomies were allocated randomly into one of two groups. Following induction of general anaesthesia, Group PS (n = 21) received a lateral popliteal sciatic nerve block and Group AB (n = 19) received an ankle block. Both groups received 20 ml bupivacaine 0.5% plain. In group PS 43% required morphine analgesia in the Post Anaesthetic Recovery Room (PAR) compared with 16% in group AB. Postoperative analgesia was assessed using VAS and a pain scale in the PAR and a questionnaire by telephone follow-up on the day after surgery. The ankle block appeared to be more reliable, providing more consistent analgesia in the PAR. Postoperative analgesia in Group PS lasted a median of 18.0 hr and in Group AB lasted 11.5 hr (P < 0.05). Both techniques provided effective analgesia after discharge home and high levels of patient satisfaction.
Adolescent↗
Factors associated with postoperative pulmonary complications in patients with severe chronic obstructive pulmonary disease.
The purpose of this study was to determine the incidence of different postoperative pulmonary complications (PPCs) and their associated risk factors in patients with severe chronic obstructive pulmonary disease (COPD) (forced expiratory volume in 1 s [FEV1] < or = 1.2 L and FEV1/forced vital capacity (FVC) < 75%) undergoing noncardiothoracic operations. Thirty-nine of 105 patients (37%) had one or more PPCs (death, pneumonia, prolonged intubation, refractory bronchospasm, or prolonged intensive care unit (ICU) stay). Thirty-eight of 39 patients (97%) with a PPC had an anesthetic duration > 2 h. Our study patients had a 47% 2-yr mortality rate. We determined specific risk factors for each PPC by analyzing potential preoperative and intraoperative risk factors. Pulmonary factors alone do not predict the likelihood of PPCs in severe COPD patients. Multiple logistic regression identified composite scoring systems, such as the ASA physical status, as the best preoperative predictors of PPCs, probably because they include both pulmonary and nonpulmonary factors. During the intraoperative period, avoiding general anesthesia with tracheal intubation may decrease the risk of postoperative bronchospasm. Shortening the duration of surgery and anesthesia may decrease the risk of prolonged ICU stay.
Aged↗
Methemoglobinemia and oxyhemoglobin concentration.
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Administration, Topical↗
Lateral popliteal sciatic nerve block compared with subcutaneous infiltration for analgesia following foot surgery.
A new lateral approach to blocking the sciatic nerve in the popliteal fossa is described. In a prospective study, 40 patients scheduled for foot surgery involving osteotomies were allocated randomly into one of two groups following induction of general anaesthesia: group PS (n = 21) received a lateral popliteal sciatic nerve block and group SC (n = 19) received subcutaneous infiltration of the wound. Both groups received 20 ml bupivacaine 0.5% plain. The lateral approach to the popliteal sciatic nerve was found to be an effective, quick, and easy to perform, block. Postoperative analgesia in groups PS lasted a median of 18.0 hr and in group SC lasted 6.3 hr (P < 0.05). The lateral popliteal sciatic nerve block provided effective analgesia following foot surgery and had a high level of patient satisfaction.
Adolescent↗
Oxygen Fick and modified carbon dioxide Fick cardiac outputs.
OBJECTIVE: To compare cardiac outputs estimated from the classical oxygen Fick and modified CO2 Fick methods with thermodilution cardiac output. The modified CO2 Fick cardiac output was obtained by replacing the oxygen uptake (VO2) in the Fick equation with the CO2 production (VCO2) divided by either an assumed or measured value of the respiratory exchange ratio or with an independently determined constant (Crit Care Med 1991; 19:1270-1277). DESIGN: Criterion standard study. SETTING: The medical and surgical intensive care unit (ICU) in a Veterans Affairs Medical Center. PATIENTS: A total of 17 patients (26 studies) and 11 surgical patients (13 studies), predominantly mechanically ventilated using the intermittent mandatory ventilation mode, were studied over a period of 4.3 hrs. MEASUREMENTS: A respiratory gas exchange monitor was used to measure VO2, VCO2, and respiratory exchange ratio at 3-min intervals. Calculations were performed with arterial and venous oxygen saturations measured with both a laboratory cooximeter and bedside pulse and venous reflectance oximeters. In the oxygen Fick method, cardiac output was calculated from VO2 together with arterial and venous oxygen saturations. In the modified CO2 Fick methods, cardiac output values were calculated from arterial and venous oxygen saturations with VCO2, divided by either: a) an assumed value of the respiratory exchange ratio equal to 0.8 for all patients (method 1); b) the patient's measured value of the respiratory exchange ratio (method 2); or c) a constant, determined from an initial, simultaneous measurement of thermodilution cardiac output, VCO2, and oximetry saturations. Data were examined by linear regression analysis and bias and precision calculations. MAIN RESULTS: Thermodilution cardiac output was more related to cardiac outputs calculated with the 3 modified CO2 Fick methods than to the oxygen Fick cardiac output. Thermodilution cardiac output was closely related to the modified CO2 Fick cardiac output calculated via method 3. For this method, with pulse and venous reflectance oximetry saturations, linear regression yielded an r2 = .85, a standard error of the estimate of 0.88 L/min (n = 111) and a bias and precision of 0.11 and 0.97 L/min, respectively. Thermodilution cardiac output was less closely related to oxygen Fick cardiac output, which, when calculated with pulse and venous reflectance oximetry saturations, yielded an r2 = .50, a standard error of the estimate of 1.47 L/min (n = 128), and a bias and precision of 0.01 and 1.85 L/min, respectively. CONCLUSIONS: We conclude from this study that thermodilution cardiac output is more closely related to cardiac output calculated from modified CO2 Fick methods than to oxygen Fick cardiac output. Since cardiac output calculated with the modified CO2 Fick method 3 obviates the difficulties associated with measuring VO2 accurately and requires neither an assumption of nor measurement of the respiratory exchange ratio, method 3 may prove to be clinically useful for continuous cardiac output monitoring via oximetry in ICU patients.
Adult↗
Nasal colonization with methicillin-resistant Staphylococcus aureus on admission to the surgical intensive care unit increases the risk of infection.
We prospectively studied the relationship of perioperative methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization and subsequent infection in surgical intensive care unit (SICU) patients. In addition, risk factors for MRSA nasal colonization were examined. All patients admitted to the 15-bed SICU between August 1991 and July 1992 had their anterior nares cultured. Cultures positive for S. aureus were subsequently placed on oxacillin-containing plates to screen for methicillin-resistance. Of 484 patients, 19 had MRSA nasal colonization (3.9%). There were five infections in the 19 patients with positive perioperative nasal cultures versus six infections in the remaining 465 patients (P < 0.0001). Immunoblot typing confirmed the concordance of colonizing and infecting strains. Prior exposure to the spinal cord injury center (P < 0.001) and prior antibiotic therapy (P < 0.003) were also significant multivariate risk factors for perioperative nasal colonization. Patients with perioperative MRSA nasal colonization are at significantly increased risk of subsequent postoperative MRSA infection.
Aged↗
Changes in renal vein, renal surface, and urine oxygen tension during hypoxia in pigs.
To determine whether ureteral urine oxygen tension could serve as a monitor of renal hypoxia and its relationship to other renal O2 tension parameters, we simultaneously measured femoral artery (PaO2), renal vein (PrvO2), renal surface (PrsO2), and ureteral urine (PuO2) oxygen tensions in 8 anesthetized pigs while incrementally decreasing the inspired oxygen concentration (FiO2) from 21% to 12%. Renal artery blood flow, measured by transit time ultrasound, renal oxygen consumption, and thermodilution cardiac output, was constant. Changes in PaO2, PrvO2, PrsO2, and PuO2 caused by decreasing FiO2 were evaluated by one-way analysis of variance. The relationships between PuO2 and the other O2 tension parameters were evaluated by correlation coefficient and linear regression statistics. Of six possible O2 decrements (combinations of 3, 6, and 9%), only PrvO2 significantly decreased with all six decrements. PuO2 decreased when FiO2 decreased 6% or more. PuO2 is not a sensitive indicator of systemic hypoxia. Under constant renal perfusion and oxygen consumption, PuO2 had a correlation coefficient of 0.80 and a regression equation of PuO2 = 0.84 (PrvO2) + 11.6, with PrvO2. PuO2 is related to PrvO2 when renal perfusion is constant.
Animals↗
Experimental and predicted dual oximetry variability.
OBJECTIVE: We wished to determine whether the individual bias (mean difference) and precision (standard deviation of the difference) values of 2 variables, arterial oxygen saturation (SaO2) and mixed venous oxygen saturation (SvO2), could be used to predict the bias and precision values of the combined dual oximetry variable (SaO2-SvO2). METHODS: We simultaneously measured SaO2 by pulse oximetry and arterial blood gas co-oximetry and SvO2 by fiberoptic reflectance oximetry pulmonary artery catheter and venous blood gas co-oximetry in 238 data sets from 55 patients. Three different methods were used to predict the standard deviation of the difference of (SaO2-SvO2) [s delta(SaO2-SvO2)]: simple sum, root mean square (RMS) error, and RMS error with correction term. We derived the equation for the RMS error with correction term because initial results showed that the simple sum and RMS error methods did not predict s delta(SaO2-SvO2) well. The correction term accounts for the non-independence of simultaneous SaO2 and SvO2 measurements. RESULTS: The observed overall bias of the SaO2, SvO2, and (SaO2-SvO2) measurement methods were 0.17, -1.76, and 1.94, respectively. The observed overall s delta(SaO2-SvO2) of the (SaO2-SvO2) measurement method was 5.12. The simple sum method overestimated the actual s delta(SaO2-SvO2) by 38%, the RMS error method differed from the actual s delta(SaO2-SvO2) by 3%, and the RMS error with correction term method matched the actual s delta(SaO2-SvO2). CONCLUSION: The bias of a (SaO2-SvO2) measurement method is simply the bias of the SaO2 measurement method less the bias of the SvO2 measurement method. s delta(SaO2-SvO2) is best predicted by the derived equation, RMS error with correction term. The same principles and equations also apply to other situations in which 2 variables with the same dimensions are combined into 1 variable, such as (PaCO2-EtCO2) gradients and perfusion-pressure gradients. Although the difference between the s delta(SaO2-SvO2) predicted by the RMS error equation and the derived RMS error equation with correction term was small, the difference may be significant for other combined variables.
Oximetry↗
Regional anaesthesia for intraocular surgery.
The role of anaesthetists in providing local anaesthesia for intraocular surgery has changed over the past decade. No longer confined to the interested few, more and more anaesthetists are involved in monitored care and/or are performing eye block anaesthesia. This review summarizes the information related to eye block anaesthesia. The salient features of the orbital anatomy important for safe conduct of eye block anaesthesia are described. The techniques for retrobulbar and peribulbar anaesthesia, including facial nerve blocks, anaesthetic mixture, types of needles, and softening the eye are presented. Complications such as retrobulbar haemorrhage, globe penetration/perforation, visual impairment, brainstem anaesthesia, muscle injury, and oculocardiac reflex are explored. The implications of anticoagulant therapy are examined. The choice between retrobulbar and peribulbar blocks and the role of anaesthetists are discussed.
Anesthesia, Conduction↗
A modified retrobulbar block for eye surgery.
A modified retrobulbar block (MRB) using a single superomedial injection was compared with the classical retrobulbar block (RB) and peribulbar block (PB) in a randomized, prospective, surgeon-blinded study involving 150 patients undergoing cataract surgery. No serious complication occurred in any of the patients. The MRB produced higher rates of total akinesia in the orbicularis and all the extraocular muscles, which were statistically significant for the orbicularis, superior, inferior and lateral rectus and oblique muscles when compared with RB, and for the superior rectus and oblique muscles when compared with PB. MRB required less supplemental blocks, provided good operating conditions for the surgeon, and achieved high patient acceptance. It is concluded that MRB is a useful alternative method of ocular block for cataract surgery.
Adult↗
Patient recruitment for clinical research.
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Anesthesia, Local↗
Alteration of clathrin light chain expression by transfection and gene disruption.
The light chain subunits of clathrin, LCa and LCb, have been implicated in the regulation of coated vesicle disassembly and other aspects of clathrin cycling within the cell. The potential for functional specialization of each light chain is suggested by tissue-specific variation in the relative amounts of the two light chains and by conservation of differences between LCa and LCb sequences during evolution. To investigate whether there might be exclusive roles for LCa and LCb in clathrin function, the expression of LCa was manipulated in C1R lymphoid cells and PC12 pheochromocytoma cells by transfection with light chain cDNA. These two cell lines differ in their ratios of LCa to LCb, expressing 86 and 25% LCa, respectively. After transfection with exogenous human LCa cDNA, a PC12 cell derivative was produced that completely lost the ability to manufacture LCa. Loss of LCa expression was found to be because of gene disruption and consequent lack of mRNA transcription. In C1R cells, the normally high level of LCa expression was reduced to 25% by overexpression of transfected LCb cDNA under the control of an inducible promoter. The C1R transfectants with reduced levels of LCa and the LCa-negative PC12 transfectant grow normally and show no change in clathrin distribution, clathrin assembly level, or impairment of endocytosis or secretion compared with wild-type cells and cells transfected with vectors lacking light chain cDNA. However, subtle alterations in the hsc70-mediated clathrin uncoating process were observed for vesicles derived from the LCa-negative cells, reflecting the preferential activity of LCa in stimulating the in vitro uncoating reaction.
Animals↗
100-kD proteins of Golgi- and trans-Golgi network-associated coated vesicles have related but distinct membrane binding properties.
The 100-110-kD proteins (alpha-, beta-, beta'-, and gamma-adaptins) of clathrin-coated vesicles and the 110-kD protein (beta-COP) of the nonclathrin-coated vesicles that mediate constitutive transport through the Golgi have homologous protein sequences. To determine whether homologous processes are involved in assembly of the two types of coated vesicles, the membrane binding properties of their coat proteins were compared. After treatment of MDBK cells with the fungal metabolite Brefeldin A (BFA), beta-COP was redistributed to the cytoplasm within 15 s, gamma-adaptin and clathrin in the trans-Golgi network (TGN) dispersed within 30 s, but the alpha-adaptin and clathrin present on coated pits and vesicles derived from the plasma membrane remained membrane associated even after a 15-min exposure to BFA. In PtK1 cells and MDCK cells, BFA did not affect beta-COP binding or Golgi morphology but still induced redistribution of gamma-adaptin and clathrin from TGN membranes to the cytoplasm. Thus BFA affects the binding of coat proteins to membranes in the Golgi region (Golgi apparatus and TGN) but not plasma membranes. However, the Golgi binding interactions of beta-COP and gamma-adaptin are distinct and differentially sensitive to BFA. BFA treatment did not release gamma-adaptin or clathrin from purified clathrin-coated vesicles, suggesting that their distribution to the cytoplasm after BFA treatment of cells was due to interference with their rebinding to TGN membranes after a normal cycle of disassembly. This was confirmed using an in vitro assay in which gamma-adaptin binding to TGN membranes was blocked by BFA and enhanced by GTP gamma S, similar to the binding of beta-COP to Golgi membranes. These results suggest the involvement of GTP-dependent proteins in the association of the 100-kD coat proteins with membranes in the Golgi region of the cell.
Adaptor Protein Complex alpha Subunits↗
Perioperative stroke. Part II: Cardiac surgery and cardiogenic embolic stroke.
The major mechanism of stroke in cardiac surgery is embolization. The risk is higher in intracardiac than in extracardiac surgery. The incidence of stoke associated with CABG is about 5%. The cerebral protective properties of isoflurane and thiopentone, acid-base management, and monitoring of cerebral perfusion during cardiopulmonary bypass are discussed. Prophylactic carotid endarterectomy for patients with asymptomatic carotid disease before cardiac surgery is not necessary. Symptomatic carotid disease increases the risk of stroke, and the management of patients who have both symptomatic coronary and carotid artery diseases is discussed. Cardiogenic embolism is probably responsible for many perioperative strokes. Patients with atrial fibrillation, valvular disease, and prosthetic heart valves are at high risk of cardiogenic embolism. Strokes associated with cardioversion, pacemaker insertion, coronary arteriography and angioplasty are explored.
Cardiac Surgical Procedures↗
Perioperative stroke. Part I: General surgery, carotid artery disease, and carotid endarterectomy.
Although stroke, defined as a focal neurological deficit lasting more than 24 hr, is uncommon in the perioperative period, its associated mortality and long-term disability are high. No large-scale data are available to identify the importance of recognized risk factors for stroke in the perioperative period. A review of the literature shows that the incidence and mechanism of its occurrence are influenced by the presence of cardiovascular disease and the type of surgery. The most common cause of perioperative stroke is embolism. In non-cardiac surgery, the incidence of perioperative stroke is higher among the elderly. Properly administered, controlled hypotension is associated with minimal risk of stroke. Cerebral vasospasm may be the cause of focal cerebral ischaemia in eclamptic patients, and the aggressive treatment of hypertension may exacerbate the neurological damage. The risk of stroke associated with carotid endarterectomy is closely related to the preoperative neurological presentation, and the experience of the surgical/anaesthetic team. Symptomatic cerebrovascular disease, acute stroke, asymptomatic carotid lesions, preoperative assessment of risk, local and general anaesthesia, cerebral protection and monitoring during carotid endarterectomy are discussed with reference to reducing the risk of perioperative stroke. Adequate monitoring and protection have minimized the risk of ischaemia from carotid clamping, and the major mechanism of stroke is embolization.
Carotid Arteries↗
Clathrin light chains: arrays of protein motifs that regulate coated-vesicle dynamics.
Polymerization of clathrin triskelions into clathrin coats and subsequent disassembly by the heat shock protein hsc70 control receptor-mediated pathways of intracellular transport. The clathrin light chains are major regulatory elements in these processes. These polypeptides consist of linear arrays of functional domains with distinctive sequence motifs. Comparison of unicellular and multicellular eukaryotes reveals differences in the numbers of clathrin light chains and in the functional domains they contain.
Amino Acid Sequence↗
Cardiac output from carbon dioxide production and arterial and venous oximetry.
OBJECTIVE: To determine cardiac output from measurements of CO2 production (VCO2), and arterial (SaO2) and mixed venous (SvO2) oxygen saturations, using a modified Fick equation, in which cardiac output = VCO2/[k (SaO2 - SvO2)], where k represents a constant. DESIGN: A metabolic measurement cart was used to measure VCO2 and oxygen consumption (VO2) at 3-min intervals. SaO2 and SvO2 were measured via a pulse oximeter and a fiberoptic right heart catheter, respectively. The initial value of k for each study was determined from initial simultaneous measurements of thermodilution cardiac output, VCO2, SaO2, and SvO2 via the equation k = VCO2/[cardiac output (SaO2 - SvO2)]. The value of k was assumed to remain constant for the entire study period. Thereafter, cardiac outputs calculated from k and the measurements of VCO2, SaO2, and SvO2 were compared with the simultaneously obtained cardiac outputs determined by thermodilution. Similarly, cardiac outputs calculated from the traditional oxygen Fick equation, where cardiac output = VO2/[13.4 x hemoglobin (SaO2 - SvO2)], were compared with the simultaneously acquired cardiac outputs determined by thermodilution. SETTING: Surgical ICU in a Veterans Affairs Medical Center. PATIENTS: Seven postoperative patients, mechanically ventilated using the intermittent mandatory ventilation mode, were studied over a mean period of 4 hrs. RESULTS: Cardiac output (obtained from VCO2 and oximetry saturations) was closely related to thermodilution cardiac output: with linear regression showing r2 = .96 and standard error of the estimate = 0.59 L/min, n = 21; and, with bias and precision = 0.17 and 0.68 L/min, respectively. The traditional oxygen Fick cardiac output was also closely related to the thermodilution cardiac output (r2 = .81, standard error of the estimate = 1.46 L/min, n = 22; bias and precision = 0.31 and 1.46 L/min, respectively). CONCLUSION: The proposed method for calculating cardiac outputs solely from VCO2 and oximetry saturations yields results that correspond closely to thermodilution determined cardiac outputs. The method is simple and avoids the difficulties in the Fick method associated with accurate VO2 measurement. This approach may be suitable for continuous cardiac output monitoring in critically ill patients.
Aged↗