Linda Chen

Urticaria pigmentosa: An anesthetic challenge

Urticaria pigmentosa is the most common form of mastocytosis, a disease in which abnormal proliferations of mast cells occur in various organs of the body. Multiple stimuli, including many drugs commonly used in anesthetic practice, can provoke mast cell degranulation and result in intraoperative hemodynamic instability. An anesthetic plan minimizing histamine release and utilizing vecuronium as the muscle relaxant is discussed, and the literature pertaining to urticaria pigmentosa is reviewed.

Mechanical Factors Do Not Influence Blood Flow Distribution in Atelectasis

The contribution of mechanical factors to the vascular resistance of the atelectatic lung has been studied in vivo in the anesthetized open-chest dog. When the left lung was ventilated with an hypoxic gas mixture (while the right lung was ventilated with 100% O2), left lung blood flow decreased from 0.99 +/- 0.11 1.min-1 to 0.40 +/- 0.08 1.min-1 due to hypoxic pulmonary vasoconstriction (hypoxic stimulus PSO2 = 36.1 +/- 0.8 mmHg). When the left lung was made atelectatic, blood flow decreased to 0.65 +/- 0.11 1.min-1, consistent with a weaker hypoxic stimulus (PSO2 = 54.0 +/- 3.2 mmHg). With the addition of sodium nitroprusside infused intravenously, left lung blood flow increased to 1.05 +/- 0.14 1.min-1 during atelectasis, and to 0.61 +/- 0.09 1.min-1 during hypoxic ventilation, while flow remained at 0.94 +/- 0.18 1.min-1 during hyperoxic ventilation. When the results were plotted on pressure-flow diagrams, the hyperoxic, hypoxic, and atelectatic lung points fell on the same pressure-flow line in the presence of nitroprusside. It is concluded that hypoxic pulmonary vasoconstriction is the major (but not necessarily only) determinant of increased vascular resistance in the atelectatic lung, and that passive mechanical factors do not measurably affect blood flow distribution during open-chest atelectasis.

High-dose almitrine bismesylate inhibits hypoxic pulmonary vasoconstriction in closed-chest dogs

The effect of almitrine bismesylate on the hypoxic pulmonary vasoconstrictor (HPV) response was studied in seven closed-chest dogs anesthetized with pentobarbital and paralyzed with pancuronium. The right lung was ventilated continuously with 100% O2, while the left lung was ventilated with either 100% O2 (“hyperoxia”) or with an hypoxic gas mixture (“hypoxia”: end-tidal Po2 = 50.1 ± 0.1 mmHg). Cardiac output (CO) was altered from a “normal” value of 3.10 ± 0.18 1 · min-1 to a “high” value of 3.92 ± 0.16 1 · min-1 by opening arteriovenous fistulae which allowed measurements of two points along a pressure-flow line. These four phases of left lung hypoxia or hyperoxia with normal and high cardiac output were repeated in the presence and absence of almitrine. Almitrine bismesylate was administered as a constant infusion of 14.3 μg · kg-1 · min-1 for a mean plasma concentration of 219.5 ± 26.4 ng · ml-1. Relative blood (low to each lung was measured with a differential CO2 excretion (VCO2) method corrected for the Haldane effect. With both lungs hyperoxic, the percent left lung blood flow (%QL-VCO2) was 44 ± 1%. When the left lung was exposed to hypoxia, the %QL-VCO2 decreased significantly to 22 ±1%- However, with the administration of almitrine, the %QL-VCO2 during left lung hypoxia increased significantly to 36 ± 2%. The arterial oxygen tension decreased significantly between hyperoxia (Pao2 = 633 ± 6 mmHg) and hypoxia (271 ± 31 mmHg). With the addition of almitrine, there was no change during hyperoxia; however, during hypoxia, the Pao2 decreased significantly to 124 ± 15 mmHg. Cardiac output did not influence these findings. The pulmonary vascular conductance (G) is the slope of the pressure-flow line. The pulmonary vascular conductance of the right lung (GR × 103) (1.6 ± 0.1 dyn-1 8 cm5 · s-1) did not change significantly during hyperoxia or hypoxia when no drug was given. With the administration of almitrine, GR decreased significantly to 1.0±0.1 dyn-1 · cm5 · s-1 during both hyperoxia and hypoxia. The same was true at normal and high cardiac output. The pulmonary vascular conductance of the left lung (GL) decreased significantly between hyperoxia (1.24 ± 0.1 dyn-1 · cm5 · s-1) and hypoxia (0.7 ± 0.1 dyn-1 · cm5 · s-1). However, with the addition of almitrine, GL decreased significantly during hyperoxia (0.8 ± 0.1 dyn-1 · cm-1 · s-1), but not during hypoxia (0.8 ± 0.1 dyn-1 · cm5 · s-1). The same was true at normal and high cardiac output. It is concluded that almitrine bismesylate caused nonspecific pulmonary vasoconstriction that was greater in the 100% O2 ventilated lung than in the hypoxic lung regions. Therefore, blood flow was diverted from the hyperoxic back to the hypoxic lung causing a reduction of the HPV response.

Low-dose Almitrine Bismesylate Enhances Hypoxic Pulmonary Vasoconstriction in Closed-chest Dogs

The effect of almitrine bismesylate on the hypoxic pulmonary vasoconstrictor response was studied in six closed-chest dogs anesthetized with pentobarbital and paralyzed with pancuronium. The right lung was ventilated continuously with 100% O2; the left lung was ventilated either with 100% O2 (“hyperoxia”) or with an hypoxic gas mixture (“hypoxia”: end-tidal oxygen tension = 60.3 ± 0.6 mm Hg). On two consecutive days, each dog received either almitrine (Vectarion, Servier Lab) or malic acid. Consecutive almitrine doses of 0.003, 0.03, 0.3, and 3.0 μg·kg−1·min−1, or the equivalent volumes of malic acid without almitrine, were administered intravenously as a constant peripheral infusion for 15 min. Percent blood flow to each lung was calculated based on a variation of the traditional shunt equation. The change in percent left lung blood flow (Δ%QL-VA) increased significantly between the hypoxia-no drug and the hypoxia-almitrine (3.0μg·kg−1·min−1) phase. No significant changes occurred during the other almitrine doses or the respective malic acid control phases. The change in arterial oxygen tension (ΔPaO2) also increased significantly between the hypoxia-no drug and the hypoxia-almitrine (3.0 μg·kg−1·min−1) phase. No significant changes occurred during the other almitrine doses or the respective malic acid control phases. It is concluded that in dogs low-dose almitrine enhances hypoxic pulmonary vasoconstriction and that this enhancement is dose-related.

The use of epidurals in abdominal wall reconstruction: an analysis of outcomes and cost.

Background: Ventral hernias are a common, challenging, and expensive problem for general and reconstructive surgeons. The authors assessed the impact of epidurals on morbidity following abdominal wall reconstruction for hernia. Methods: A retrospective review of abdominal wall reconstruction patients operated on between 2007 and 2012 was performed with a specific focus on the use of epidurals. Bivariate and multivariate logistic regression analyses were used to assess independent predictors of morbidity. Subgroup analyses were also performed. Results: The study included 134 consecutive reconstructions performed by a single surgeon over a 5-year period at an academic teaching center. Patient groups were similar in terms of demographics, preoperative characteristics, hernia grade, and intraoperative characteristics. Epidural use was associated with a lower incidence of major surgical complications (19.7 percent versus 36.1 percent; p = 0.04) and medical complications (26.8 percent versus 54.1 percent; p = 0.001). A significant and independent reduction in medical morbidity (OR, 0.09; p ⩽ 0.001) and unplanned reoperations (OR, 0.23; p = 0.052), was found with patients receiving epidurals. Furthermore, a notable trend toward reduced major surgical complications (OR, 0.45; p = 0.141) and cost savings (−

The effect of pleural pressure on the hypoxic pulmonary vasoconstrictor response in closed chest dogs.

22,184; p = 0.01) was found in patients who received epidurals. Subgroup analysis did not demonstrate statistically significant reductions in major surgical morbidity in reconstruction either with (p = 0.13) or without (p = 0.07) concurrent intra abdominal procedures when epidurals were not or were used, respectively. Conclusions: Epidural use may be associated with reduced morbidity and cost savings in abdominal wall reconstruction. This effect appears to be related to reduced medical morbidity and shortened length of stay in patients undergoing more complex, concurrent intraabdominal hernia procedures. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, II.

Perioperative Pain Management for Patients on Chronic Buprenorphine: A Case Report

The effect of intrapleural pressure on the hypoxic pulmonary vasoconstrictor (HPV) responses to atelectasis and hypoxia were measured in two groups of anesthetized closed chest dogs. The right lung was continuously ventilated with 100% O2. The left lung was initially ventilated with 100% O2, (hyperoxia) but subsequently underwent either reabsorption atelectasis (atelectasis; group I) or ventilation with a hypoxic gas mixture (hypoxia; group II). The mean intrapleural pressure in the left hemithorax was 5.4 cm H2O during hyperoxia, but with left lung atelectasis decreased significantly to −3.8 cm H2O by 15 minutes and to −4.2 cm H2O by 90 minutes. Venous admixture (%VA) increased significantly from 10.3% during hyperoxia to 33.2% at 15 minutes of left lung atelectasis and to 34.6% at 90 minutes. However, after sternotomy with the left lung still atelectatic, the %VA decreased significantly to 25.4%. For the hypoxia group, %VA increased significantly from 9.2% during hyperoxia to 29.9% at 15 minutes of left lung hypoxia and 25.1 % at 90 minutes. HPV diverted blood flow away from both atelectatic lung and hypoxic lung. However, due to the negative intrapleural pressure generated during left lung resorption atelectasis when the chest was closed, HPV was less effective during atelectasis than during hypoxia.

The Influence of Halothane and Isoflurane on Pulmonary Collateral Ventilation

Here we present a patient with a Type I Chiari malformation who was receiving buprenorphine for chronic pain who underwent two separate urogynecologic procedures for removal of vaginal mesh with two different pain management regimens. For the first procedure at an outside hospital, the patients usual dose of buprenorphine (8 mg sublingual every 8 hours) was continued up through her surgery and then a full opioid receptor agonist was used for postoperative pain management. The patient complained that this resulted in very poor pain control for her in the postoperative period. Prior to her second procedure, which was performed at our institution, buprenorphine was switched to a full opioid agonist (oral hydromorphone 4 mg every 4 to 6 hours, maximum 20 mg per day) for 5 days prior to surgery; postoperative pain was managed with full opioid receptor agonists. The patient again reported suboptimal pain control in spite of substantially increased doses of opioids. This case report highlights the difficulty of perioperative pain management for patients on chronic buprenorphine and emphasizes the need for additional investigation.

Negative Pressure Pulmonary Edema after Laryngospasm: A Revisit with a Case Report

The effects of halothane and isoflurane on hypocapnic increases in pulmonary collateral resistance were studied in dogs. A bronchoscope with a double lumen catheter in the suction port obstructed a peripheral airway and allowed gas to flow out of the isolated segment of lung only via collateral channels. The collateral gas flow (&OV0312;coll) was measured with a flowmeter and delivered through one lumen of the catheter, while the other lumen measured distal pressure (Pb). At FRC, the resistance to collateral ventilation (Rcoll) was calculated as Rcoll = Pb/Vcoll. The rest of the lung was ventilated with air, while air (hypocapnia), 10% CO2 in air, or air and halothane or isoflurane were delivered to the isolated segment. A measurement of resistance was made after 4 min of test gas flow. For each segment, when air replaced 10% CO2, the average increase in Rcoll was calculated and called Rmax. When 10% CO2 in air was infused into segments the mean Rcoll (n = 50) was 0.0196 ± 0.0022 cmH2O·ml−1 · min. This increased to 0.0285 ± 0.0031 cmH2O · ml−1 · min (mean ± E) when air was infused, a mean increase in resistance of 52 ± 3%. When halothane or isoflurane was added to air the hypocapnic increase in Rcoll was attenuated with a 50% decrease at 1.3% (1.4 MAC and 0.8 MAC, respectively). These two inhalational anesthetics reduce active changes in the flow resistance to collateral ventilation. When collateral resistance acts to adjust ventilation perfusion deviations, this action of halothane and isoflurane may make this regulation less effective.

Intraoperative air embolism with pulse irrigation device

Laryngospasm, a brief closure of the vocal cords is not an uncommon perioperative occurrence. If recognized and managed appropriately, the effects are transient and reversible. However, in rare cases where recognition and management are delayed, the consequences are associated with a high morbidity including desaturation, awareness, negative pressure pulmonary edema, and mortality. This case highlights that of a healthy woman admitted the intensive care unit (ICU) for negative pressure pulmonary edema (NPPE) after an episode of laryngospasm.