The effect of flow on the filtration performance of paediatric breathing system filters

The effect of flow on the filtration performance of six different types of filter intended for use in paediatric anaesthesia was measured by challenging the filters with sodium chloride particles at five different flows: 6, 10, 15, 20 and 30 l.min⁻¹. Twenty-five unused samples of each filter type were evaluated. The pressure drop across each filter was measured at the same flows as those used to measure penetration. The pressure drop varied both between and within the types of filter. Mean pressure drop varied between 89 and 262 Pa at a flow of 15 l.min⁻¹ for the six different filters. Penetration of sodium chloride particles varied from 1.9 to 18% at 15 l.min⁻¹ for the six filters. Allowing for the variation in pressure drop, the penetration of particles increased fairly linearly as flow increased for all six filter types. The increase in penetration per unit increase in flow varied from 0.11 to 0.82% per litre per minute. Over the range of flows studied, the increase in penetration with flow is fairly predictable.     

The importance of flow and pressure release in emergency jet ventilation devices

Background:  Several self-assembled devices, consisting of a three-way stopcock connected to a high pressure oxygen source, have been proposed for transtracheal jet ventilation in an emergency situation. As a three-way stopcock acts as a 'flow splitter' it will, when connected to a continuous oxygen flow, never ensure total flow and pressure release through its side port. The aim of the present study was to measure the efficacy of flow and pressure release of three previously described self-assembled jet devices and one commercially available tool.
Methods:  In a laboratory setting simulating an obstructed upper airway the generated pressure at the cannula tip (PACT) during the expiration phase was measured in three self-assembled jet devices consisting of a three-way stopcock with an inner diameter of 2 mm (device A), 2.5 mm (device B), and 3 mm (device C), respectively, and in the Oxygen Flow Modulator (OFM) at oxygen flows of 6, 9, 12, and 15 l·min⁻¹.
Results:  The PACT of device A at on oxygen flow of 15 l·min⁻¹ was 71.1 (±0.08) cm H₂O. At a reduced flow of 9 l min⁻¹ the PACT of device A was still 25.8 (±0.08) cm H₂O. In device B and C the PACT was 35.6 (±0.04) and 17.6 (±0.04) cm H₂O, respectively, at an oxygen flow of 15 l·min⁻¹. In contrast, the PACT in the OFM (five side holes open) was 4.4 (±0.02) cm H₂O at the same flow.
Conclusion:  In case of complete upper airway obstruction the OFM provides sufficient flow and pressure release, whereas the self-assembled jet devices tested are inherently dangerous constructions.     

Subcutaneous blood flow in man during sleep with continuous epidural anaesthesia

Background: Subcutaneous blood flow increases during sleep and we evaluated if this increase is affected by epidural anaesthesia.
Methods: Lower leg subcutaneous blood flow was determined by ¹³³Xenon clearance in ten subjects during continuous epidural anaesthesia at L₂-L₃ including eight hours of sleep, while the upper abdominal subcutaneous blood flow served as control.
Results: Epidural anaesthesia to the level of the umbilicus was followed by an increase in the lower leg subcutaneous blood flow from 3.4 (1.8-6.3) to 7.8 (3.6–16.9) ml min^-1 100 g^-1 (median and range; P <0.001) and returned to 3.5 (2.4–7.6) ml min^-1 100 g^-1 after 88 (45–123) min. In contrast, until the period of sleep the upper abdominal region blood flow remained at 5.2 (3.2–6.4) ml min^-1 100 g^-1. During sleep, lower leg subcutaneous blood flow did not change significantly, but the upper abdominal flow increased to 6.2 (5.2–7.2) ml min^-1 100 g^-1 after 34 (29–70) min ( P <0.01), and it remained elevated for 125 (100–164) min.
Conclusions: The results indicate that although epidural anaesthesia induced only a temporary increase in lower leg subcutaneous blood flow, it hindered the rise in subcutaneous blood flow normally manifest during early sleep.     

Contradictory effects of dopamine at 32°C in pigs anesthetized with ketamine

Background: In critically ill patients who were surface cooled to 332C, we have observed that dopamine sometimes causes a substantial decrease in blood pressure. The present study was designed to compare the effects of dopamine in normothermia to those seen after surface cooling to 32C.
Methods: Seven pigs with a mean body weight of 21 kg were anesthetized with ketamine and muscle relaxation was induced with pancuronium. They were mechanically ventilated and given dopamine infusions (5 and 12 μg · kg^-1 min^-1) in normothermia and after surface cooling by cold water immersion to a central blood temperature of 320C (range 31.6–32.6C).
Results: In normothermia, dopamine at a dose of 5 μg · kg^-1 min^-1 increased mean arterial blood pressure (MAP) by 16% ( P < 0.01) and cardiac output (CO) by 9% ( P =0.051); at 12 μg kg^-1 min^-1 dopamine increased MAP by 26% ( P < 0.01) and CO by 18% ( P < 0.01). In hypothermia, MAP and CO did not change at an administration rate of 5 μg kg^-l · min^-1; at 12 μg · kg^-1 min^-1 CO was unchanged but MAP was significantly reduced by 15% ( P < 0.01).
Conclusion: Dopamine increased CO and MAP in normothermia but not at 32C, where there was even a significant reduction of MAP in this porcine model.     

Effects on skeletal muscle oxygenation and capillary blood flow by adenosine-, sodium nitroprusside- and acetylcholine-induced hypotension

Background: Adenosine (ADO)-induced hypotension during diethyl ether anesthesia has been shown to increase skeletal muscle oxygenation. Whether this beneficial effect of ADO hypotension is present also during another anesthetic technique was tested in the present study using ketamine-xylazine anesthesia, and its actions were compared with sodium nitroprusside (SNP) and acetylcholine (ACh) induced hypotension in rabbits.
Methods: Local oxygen pressure and capillary blood flow were measured with a multiwire microelectrode which was placed on the surface of the left vastus medialis muscle. The experiments were performed in three groups, in which either ADO, SNP or ACh was infused into a central vein in a dose that produced a reduction of the mean arterial pressure by 20–25%, to approximately 60 mmHg.
Results: In the ADO group (60–170 μg kg^-1 min^-1) the tissue oxygen pressures increased by 23% while capillary blood flow decreased by 38%. During SNP administration (1–3 μg kg^-1 min^-1) the oxygen pressures decreased by 21% and an increase of 31% in capillary flows was seen. When ACh was infused (1–4 μg kg^-1 min^-1) the oxygen pressures decreased by 21% and, in parallel, capillary blood flow decreased by 50%. During hypotension no low tissue oxygen pressure values (<1.5 kPa) were found in the ADO group, whereas they were present in both the SNP and ACh group.
Conclusion: Compared to sodium nitroprusside and acetylcholine, adenosine appears to have an oxygen-sparing effect in the skeletal muscle during pharmacologically induced hypotension.     

Differential effects of dobutamine, dopamine, and noradrenaline on splanchnic haemodynamics and oxygenation in the pig

Supranormal oxygen (O₂) transport may benefit critically ill patients. Catecholamines are clinically employed for this purpose. However, their effects on splanchnic haemodynamics and oxygenation are not well defined. The effects of dobutamine (DOBU), dopamine (DOPA), and noradrenaline (NA) on splanchnic blood flows (electromagnetic flow probes), O₂ deliveries and uptakes (catheterisation of portal and hepatic veins) were studied in nine anaesthetised (ketamine/flunitrazepam), ventilated, paralysed, and laparotomised pigs. All three catecholamines (DOPA at 15 μg·kg^-1 · min^-1, DOBU at 13 μg · kg^-1 · min^-1, NA at 0.4 μg · kg^-1 · min^-1) significantly ( P <0.05) increased cardiac output and systemic O₂ delivery. Only DOPA increased small intestinal and total hepatic blood flows, and O₂ deliveries, and decreased O₂ extractions. The same parameters did not change during DOBU. During NA, total hepatic blood flow and O₂ delivery decreased, and hepatic O₂ extraction increased. During all three catecholamines, small intestinal and total hepatic O₂ uptakes did not change significantly. Whereas hepatic arterial blood flow decreased during both DOPA and NE, portal venous flow increased during DOPA. These data suggest that in the experimental model used splanchnic O₂ supply and O₂ reserve capacity appear improved by DOPA, unaffected by DOBU, and impaired by NA.     

Pharmacokinetic–pharmacodynamic modeling of the hypotensive effect of remifentanil in infants undergoing cranioplasty

Objectives:  Although remifentanil has been used to induce hypotension during surgery in infants, no pharmacokinetic–pharmacodynamic (PKPD) model exists for its quantitative analysis. Our aim was to determine the quantitative relationship between whole blood remifentanil concentration and its hypotensive effect during surgery in infants.
Methods/materials:  We studied seven infants (age 0.3–1 year) who underwent cranioplasty surgery and received remifentanil delivered by a computer-controlled infusion pump during the maintenance of anesthesia. Arterial blood samples to determine remifentanil concentration and mean arterial blood pressure (MAP) measurements were collected. A simultaneous PKPD mixed-effects model was built in NONMEM.
Results:  A total of 77 remifentanil concentrations and 185 MAP measurements were collected. Remifentanil pharmacokinetics was described with a two-compartment model, parameter estimates were 2.99 l·min⁻¹·70 kg⁻¹ for clearance and 16.23 l·70 kg⁻¹ for steady state volume of distribution. Mean baseline MAP was 69.7 mmHg and was decreased as per clinical requirements. A sigmoidal E _max model driven by an effect compartment described the decrease in MAP, with an estimated concentration to decrease MAP by half (EC₅₀) being 17.1 ng·ml⁻¹.
Conclusions:  Remifentanil is effective in causing hypotension. The final model predicts that a steady state remifentanil concentration of 14 ng·ml⁻¹ would typically achieve a 30% decrease in MAP.     

Aortic cross-clamping influences regional net release and uptake rates of tissue-type plasminogen activator in pigs

Background: The key regulator of intravascular fibrinolysis, tissue-type plasminogen activator (t-PA), is released from a dynamic endothelial storage pool. The aim of the study was to investigate regional t-PA net release and uptake rates in response to infra-renal aortic cross-clamping (AXC) and declamping (DC).
Results: Prior to AXC, we found a high net release rate of total t-PA across the preportal vascular bed (1700 ng.min^-1, P < 0.001), and a high hepatic net uptake (4900 ng.min^-1, P < 0.001), while coronary and pulmonary t-PA net fluxes were small and variable. AXC per se did not induce significant alterations in net fluxes of t-PA. Following DC, preportal and coronary net releases of total t-PA increased (to 2900 ng · min^-1 and 60 ngemin^-1, respectively). Despite an increase in hepatic net uptake of total t-PA (to 6100 ng.min^-1) after DC, a significant increase in hepatic venous total t-PA occurred.
Methods: Anesthetized pigs were studied during 5 min of AXC, followed by a 35-min declamping (DC) period. Arterio-venous concentration gradients of total and active t-PA, as well as respective plasma flows, were simultaneously obtained across the preportal, hepatic, coronary and pulmonary vascular beds. Plasma levels of total t-PA (ELISA with purified porcine t-PA as standard), and active t-PA (spectrophotometric functional assay) were determined.
Conclusions: The release and uptake of t-PA is indicated to be dynamic and organ-specific. DC induces an acute profibrinolytic reaction in preportal organs. The high hepatic t-PA uptake capacity restricts preportal profibrinolytic events to affect the systemic circulation.     

Pharmacokinetics of Pethidine During Anaesthesia and Patient-Controlled Analgesic Therapy

The pharmacokinetics of pethidine has been studied in 12 patients subjected to major intraabdominal surgery. Pethidine and norpethidine were analyzed in plasma samples collected during anesthesia and during patient-controlled administration of small intravenous doses of pethidine in the early postoperative period. A second study on the pharmacokinetics of pethidine was performed on the 3-5th postoperative day. The plasma clearance of pethidine was significantly lower in the peroperative study (8.9±1.8ml·kg·min^-1) compared with the postoperative study (12.0 ±3.1 ml·kg·min^-1). Volume of distribution (Vd) was not significantly influenced, being 4.25±1.72 l·kg^-1 peroperatively and 3.14±0.84 l·kg^-1 postoperatively. Elimination half-life decreased from 5.91 ±3.57 h peroperatively to 3.25 ± 1.40 h postoperatively. The kinetics of pethidine in the postoperative study agreed with pethidine kinetics reported for healthy volunteers. The fraction of unbound pethidine decreased from 0.26±0.1 peroperatively to 0.18±0.1 postoperatively. Norpethidine, a metabolite of pethidine, has been claimed to be responsible for several side effects like respiratory depression and convulsions during pethidine therapy. No side effect attributable to norpethidine was observed in the self-administration period. Norpethidine plasma concentrations did not exceed 500 ng/ml. The altered pethidine pharmacokinetics during anesthesia and the ensuing postoperative hours and the interindividual differences of the disposition of the drug strongly suggest that pethidine should be given by individualized regimens in surgical patients.     

Intestinal Vascular Responses to Dopamine During Fentanyl-Nitrous Oxide Anaesthesia, Supplemented with Dixyrazin

Intestinal haemodynamics in response to continuous i.v. administration of dopamine were investigated in cats anaesthetized with fentanyl-nitrous oxide either with or without supplement of dixyrazin. A dose-dependent vasodilatation was observed in the dopamine dose range 2.5–35 μg-kg^-1 min ^-1 and the subsequent maximal intestinal blood flow increase was 121%. No net intestinal vasoconstriction was evident even at the largest dopamine doses, although the vascular response reached a plateau at 17.5 μg-kg^-1 min^-1. Control experiments during chloralose anaesthesia gave similar results. Changes in mean arterial pressure and heart rate were small. Renal blood flow was virtually unchanged at dopamine doses below 10 μg-kg^-1 min^-1, while renal vasoconstriction was evident following dopamine doses above that level. The addition of i.v. dixyrazin (0.15-0.30 mg kg^-1) to the fentanyl-nitrous oxide anaesthesia substantially potentiated the intestinal vasodilator response to i.v. dopamine and the maximal blood flow increase was 183% at 10–15 μg kg^-1 min^-1. In vitro experiments using mesenteric resistance vessels from the rat demonstrated a dose-dependent relaxation to dopamine. At very large doses this response was counteracted, but not reversed into vasoconstriction by dopamine-induced a-adrenergic stimulation.     

A comparison of the effects of fentanyl and propofol on left ventricular contractility during myocardial stunning

Background : The intravenous anaesthetic propofol has been shown to possess free radical scavenging activity and calcium channel blocking effects in a number of in vitro models. We decided to compare the effects of propofol with those of fentanyl on myocardial contractility during and after ischaemia to determine whether propofol could protect the heart and improve recovery of ventricular contractile function in open-chested dogs.
Methods : Twenty adult beagles were acutely instrumented, under halothane anaesthesia, to measure ECG; aortic, left ventricular pressures; cardiac output; coronary flow; and segmental lengths in the regions perfused by the left anterior and left circumflex coronary arteries. After surgery and a stabilisation period halothane anaesthesia was terminated and fentanyl (100 μg. kg^-1 bolus followed by 2 μ.kg^-1·min^-1 infusion; n=10) or propofol (5 mg. kg^-1 bolus followed by 0.3 mg· kg^-1 min^-1 infusion; n=10) anaesthesia commenced. After a stabilisation period the LAD coronary artery was occluded for 10 min and then reperfused for 3 h. Measurements were taken throughout the protocol.
Results : We found no significant difference in recovery of contractile function between propofol and fentanyl as assessed by normalised preload recruitable work area (50±10 vs 47±16%), normalised systolic shortening (36±12 vs 48±14%) and peak left ventricular dP/dt (1665±276 vs 1846±151 mmHg.s^-1) at the end of reperfusion.
Conclusion : We conclude that at the concentration used in this study propofol shows no improvement in contractility during "stunning" when compared to fentanyl.     

The effect of a heat and moisture exchanger on humidity in a low-flow anaesthesia system

The heat and humidity in a low-flow breathing system was measured in order to study the inherent humidifying properties of the system at low fresh gas flows (< 1 and 2 l.min⁻¹) and whether a heat and moisture exchanger could compensate for the loss of heat and humidification occurring at higher fresh gas flows (5 l.min⁻¹) in these systems. Sixty patients were randomly divided into three groups (< 1, 2 and 5 l.min⁻¹ fresh gas flows) with a heat and moisture exchanger and three groups without a heat and moisture exchanger in the breathing system. Thirty minutes after the start of anaesthesia a control measurement was performed, after which a heat and moisture exchanger was inserted into the breathing system of the three groups randomly allocated to have one. Three more measurements were performed at 10, 30 and 60 min after control. At low fresh gas flows the humidifying properties of the low-flow breathing system are adequate (i.e. provide an absolute humidity > 20 mg.l⁻¹) but at a fresh gas flow of 5 l.min⁻¹ there is a need for a heat and moisture exchanger for adequate humidification of the inspired gas.     

The combination of external high-frequency oscillation and pressure support ventilation in acute respiratory failure

Background: Effective gas exchange can be maintained in animals by using external high-frequency oscillation (EHFO). The present study evaluates the effect of relatively long-term duration EHFO combined with pressure support ventilation (PSV) in patients with acute respiratory failure.
Methods: Twelve patients were ventilated with EHFO combined with PSV for 8 h at 60 oscillations min^-1, with a cuirass pressure of 36 cm H₂O: -26 to +10 cm H₂O (27 mm Hg: -19.5 to +7.5 mm Hg) and an inspiratory-to-expiratory ratio of 1: 1. Blood gas values and hemodynamic parameters were measured. Results: Significant increases were noted in cardiac index (3.0±0.7 to 3.2±0.7 1 min^-1 m^-2, P < 0.05) and stroke volume index (32±14 to 35±13 ml m^-2, P < 0.05) without changes in pulmonary artery wedge pressure at 1 h after EHFO. PaO₂(kPa)/FiO₂ and PaCO₂ improved from 21.9±7.5 to 26.8±8.0 ( P < 0.05) at 2 h and from 6.9±1.7 to 6.1±0.9 kPa ( P < 0.01) at 30 min after EHFO, respectively. Breath sounds could be heard well throughout the lung fields after institution of EHFO. The mucous rales also decreased.
Conclusions: As a method of ventilation for patients with acute respiratory failure, EHFO combined with PSV may have potential advantages over conventional mechanical ventilation when drainage of secretions is facilitated. Beneficial effects of EHFO may appear after several hours.     

Sevoflurane preserves endocardial blood flow during coronary ligation in dogs: comparison with adenosine

Background : Sevoflurane has been reported to attenuate ischaemia-induced changes of myocardial metabolism, but the mechanism is still unclear. We examined the effect of sevoflurane on regional myocardial blood flow (RMBF) in the ischaemic area and compared the flow with that in the presence of adenosine.
Method : Twenty-seven mongrel dogs were anaesthetized with fentanyl infused at the rate of 1μg.kg^-1.min^-1 throughout the experiment. Then they were divided into 4 groups; 0, 1, 2 MAC sevoflurane groups and adenosine group. Adenosine was infused into the left ventricle at a rate of 14.5 mg.kg^-1.h^-1. The left anterior descending coronary artery (LAD) was ligated for 3 min. RMBF in the endo- and epicardial layers were measured using coloured microspheres.
Results : Sevoflurane decreased both systolic and diastolic blood pressures and LV dp/dt max. Adenosine increased heart rate and coronary flow. The endocardial blood flow in 2 MAC sevoflurane was almost the same as that in the 0 MAC group. Adenosine significantly increased the myocardial blood flow. During 3-min ischaemia, endocardial blood flow in the ischaemic area under 2 MAC sevoflurane was essentially the same as those in 0 MAC and adenosine groups, though myocardial work in 2 MAC sevoflurane was lower compared with that of the other groups.
Conclusion : Preservation of endocardial blood flow related to the myocardial work during ischaemia occurred during 2 MAC sevoflurane. The decrease in LV dp/dt max induced by 2 MAC sevoflurane is one of the factors responsible for the preservation of the endocardial blood flow during ischaemia.     

The Venturi Anaesthesia Circuit II Carbon Dioxide Production and Gas Flow Requirements

Carbon dioxide production was measured in 20 adult patients undergoing alloplastic operation of the hip. Body weight ranged from 40 to 81 kg. Anaesthesia consisted of lumbar plexus block, i. v. diazepam, pethidine, pavulon and N₂O/O₂ under controlled ventilation. CO₂ production was 2.13 ml kg^-1 min^-1 (interquartile range 2.09-2.23). A fresh gas flow rate of about 30 ml kg^-1 min^-1 was required for the elimination of CO₂ produced when using the Venturi system for inhalation anaesthesia.     

Antinociceptive effect of perioperative adenosine infusion in abdominal hysterectomy

Background: Adenosine (ADO), and stable analogs thereof, have been shown to exert antinociceptive action in cutaneous and deep somatic pain under experimental and clinical conditions in animals and in humans. The aims of this randomized double-blind placebo-controlled study were to evaluate if a low dose of intravenous (i.v.) ADO could reduce the requirements of volatile anesthetic and postoperative opioid in connection to hysterectomy, where visceral nociception significantly contributes to pain.
Methods:
Forty-three women, age 32–65 years, ASA I and 11, scheduled for abdominal hysterectomy, were assigned to receive an i.v. infusion of either adenosine, 80 μg. kg^-1 min^-1, or placebo during surgery. Anesthesia was maintained with isoflurane (ISO)/N₂O/ O₂ inhalation. Postoperatively, a reduced dose of 40 μg. kg^-1. min^-1 was continued for 3 h.
Results: The end-tidal (ET-) IS0 was equal between groups before surgery. During surgery, the IS0 requirement was increased, compared to the preoperative level, in the placebo group, while the requirement declined in the ADO group. The overall IS0 requirement in the ADO group was reduced by 36% (P<0.002). The first 24 h postoperative opioid requirement, with equal resting pain in both groups, was 18% ( P < 0.05)lower in the ADO group.
Conclusion: A low dose of perioperative adenosine infusion in abdominal hysterectomy reduces the requirements of volatile anesthetic and postoperative opioid analgesic.     

Pentoxifylline in Regional Cerebral Ischemia in Cats

The effect of pentoxifylline on regional cerebral ischemia was evaluated in 22 cats. In one group of 10 cats the middle cerebral artery (MCA) was occluded by a transorbital approach, and the cats were maintained on an intensive care protocol for 48 h. Pentoxifylline 10 mg · kg^-1 initiated intravenously 30 niin post-occlusion and followed by 6.3 mg · kg^-1 · h^-1 for 48 h failed to improve the neurologic outcome or infarct size when compared to controls. In another group of 12 cats with the same ischemic lesion, regional cerebral blood flow in the anterior (ischemic) area and an ipsilateral parieto-occipital region was measured by ¹³³Xe wash-out after intra-arterial injection. MCA occlusion reduced the anterior flow by 50% from a mean control value of 62.7 ml · 100 g^-1 · min^-1 to 31.9 ml · 100 g^-1 · min^-1. The parieto-occipital flow was reduced by 20–30%, probably due to diaschisis. Pentoxifylline produced only a brief, although approximately 50%, increase in flow detected over both brain regions and failed to improve the cerebral energy stores as measured 150 min following MCA occlusion. From the neurologic, blood flow and metabolic data, it is concluded that pentoxifylline failed to affect cerebral ischemia favorably in cats.     

Survival of Densely Packed Follicular Unit Grafts Using the Lateral Slit Technique

BACKGROUND The use of densely packed follicular unit grafts (>30 grafts/cm²) is a highly debated issue, with some claiming decreased survival rates. Those who perform dense packing routinely do not believe they have seen any impaired survival. However, no prior study has rigorously analyzed densely packed areas to assess survival rates.
OBJECTIVE In this study, the authors assessed the survivability of densely packed (>70 grafts/cm²) follicular unit grafts using the lateral slit technique.
METHODS This study was a strictly observational study in one patient. Several 1-cm² areas tattooed on the mid scalp were grafted at densities ranging from 23 to 72 grafts/cm² using the lateral slit technique. The area surrounding the observation sites was transplanted at a density of 30 to 40 grafts/cm².
RESULTS Examination of the most densely packed area (72 grafts/cm²) at 8 months posttransplant revealed that the number of implanted grafts showing growth was 98.6% whereas the least densely transplanted area (23 grafts/cm²) revealed a growth rate of 95.6%.
CONCLUSION This is the first study that demonstrates high growth rates in densely packed follicular units using the lateral slit technique, even at densities of 72 grafts/cm². These data are in contradistinction to previously performed studies using older methodologies.     

Evaluating the Efficacy of Treatment of Resistant Port-Wine Stains With Variable-Pulse 595-nm Pulsed Dye and 532-nm Nd:YAG Lasers

Background. Some port wine stains (PWSs), despite multiple treatments with the 585-nm 0.45-ms pulsed dye laser (PDL), fail to improve substantially.
Objective. To determine the efficacy and tolerability of variable pulse width 595-nm PDL and 532-nm Nd:YAG laser in the treatment of resistant PWS.
Methods. Twenty-two patients whose PWS failed to achieve more than 75% lightening after more than 15 treatments with the 585-nm 0.45-ms PDL were recruited. A homogenous patch of PWS was divided into five areas. Area 1 (control area) was treated with 585-nm, 0.45-ms PDL (fluence 7.5 J/cm²). Areas 2 and 3 were treated with 595-nm PDL at fluence 15 J/cm² (with cryogen spray cooling) and pulse durations of 1.5 and 10 ms, respectively. Areas 4 and 5 were treated with a 532-nm Nd:YAG laser at 2 ms, 7 J/cm² and 10 ms, 16 J/cm², respectively (with a contact cooling tip). The response was assessed by photographic evaluation.
Results. Three patients had further lightening in area 2, and two patients had further lightening in area 3. Each of three patients had further lightening in areas 4 and 5, respectively. One patient had further lightening in the control area.
Conclusion. In individual patients, it may be effective to treat resistant PWS with the variable-pulse width 595-nm PDL and the 532-nm Nd:YAG laser.     

Cardiovascular depression by isoflurane and concomitant thoracic epidural anesthesia is reversed by dopamine

Interactive effects between exogenous dopamine (DA) and isoflurane (I) combined with thoracic epidural blockade (TEA) were studied in dogs during chloralose anesthesia. The I–TEA intervention per se decreased heart rate (HR; 28%), mean arterial pressure (MAP; 63%), cardiac output (CO; 54%), left ventricular dP/ dt (LVdP/dt; 75%) and LVdP/dt/systolic arterial pressure (SAP; 42%). Prior to the I–TEA intervention , dopamine increased MAP, CO, LVdP/dt, LVdP/dt/SAP and stroke volume (SV) already at the dose 10 μg–kg^-1. min^-1 and, additionally, increased mean pulmonary artery pressure (MPAP) at the dose 20 μg–kg^-1. min^-1. During the I–TEA intervention , the DA–induced increases in MAP and systemic vascular resistance (SVR) were significantly higher than prior to I–TEA, as indicated by significant ANOVA interactive effects. At the dose 10 μg–kg^-1 min^-1, DA restored MAP, CO, LVdP/dt, LVdP/dt/SAP and SV to levels found before the I–TEA intervention, while HR was restored first at the dose 20 μg–kg^-1 –min^-1. At the dose 20 μg–kg^-1–min^-1, DA also increased MAP (39%), LVdP/dt (119%), LVdP/dt/SAP (73%), SVR (28%) and MPAP (70%) above levels prior to I–TEA. To conclude, exogenous dopamine effectively and dose–dependently counters cardiovascular depression induced by the anesthetic technique of combining I and TEA. The pressor and systemic vasoconstrictor actions of dopamine are potentiated by conjoint administration of I and TEA.