Comparison of skeletal muscle laser Doppler flowmetry to changes in central hemodynamics in detecting the physiological response to moderate hemorrhage

Previous studies have demonstrated that laser Doppler (LD) flowmetry is a useful technique for following changes in blood flow in a tissue bed, but the potential role of LD flowmetry in management of the critically ill patient is unclear. This study sought to establish the sensitivity of LD flowmetry compared to changes in centrally measured hemodynamic parameters in response to a mild hemorrhagic episode. In order to establish the correlation between LD flow and actual blood flow, livers from Sprague-Dawley rats were isolated and perfused via the portal vein with citrate anti-coagulated rat blood. Changes in LD flow were recorded while changing blood flow via the perfusion pump. There was a strong correlation between pump flow and LD flow (for N = 5 livers, r > 0.9; P < 0.05). This relationship was stable at hematocrits > 20. The second part of this study tested the sensitivity of LD flowmetry in anesthesized baboons. An LD probe was placed on the surface of the gracilis muscle of the adult male baboons. LD flow and hemodynamic parameters were measured following two episodes of bleeding and reinfusing 250 cc of blood. During the first bleed there were significant changes in heart rate (97 + 8 to 159 + 12), mean arterial pressure (125 + 6 to 105 + 9), and LD flow (20.6 + 4.6 to 11.9 + 3.6); these parameters returned to normal after reinfusion of blood. During the second bleed, the only parameters that showed significant changes were heart rate (118 + 5 to 135 + 12) and LD flow (17.5 + 8 to 10.7 + 3.4).(ABSTRACT TRUNCATED AT 250 WORDS)

Transanal intracolonic pulse oximetry as a means of monitoring the adequacy of colonic perfusion

Techniques for determining intraoperative compromise in colonic blood flow during aortic reconstruction are inadequate. We investigated the use of transanally recorded oxygen saturation in a porcine model. A Nellcor RS-10 reflectance pulse oximeter probe was attached to the balloon of a Foley catheter and passed transanally to record the oxygen saturation of the sigmoid colonic mucosa. The blood flow rate of the caudal mesenteric artery (CMA) was recorded with a Transonic ultrasonic flowmeter. CMA flow and transanal O2 saturation were recorded simultaneously as CMA flow was progressively decreased by compression of the infrarenal aorta. With unimpeded blood flow the mean O2 saturation in the distal colonic mucosa was 92.9% +/- 2.8. As CMA flow was progressively decreased to 20% of baseline flow, there was a linear decrease in colonic O2 saturation (r = 0.91 P < 0.01). At 20% of basal CMA flow, colonic O2 saturation was 54.0% +/- 4.1. Below 20% of basal CMA flow there was an abrupt loss of signal from the pulse oximeter. This study suggests that transanal pulse oximetry would provide a simple means of continuously monitoring the adequacy of distal colonic blood flow intraoperatively and may prove to be useful during aortic reconstruction when there is concern about the adequacy of blood flow to the distal colon.

The retroperitoneal incision. An evaluation of postoperative flank 'bulge'

OBJECTIVES

To determine if intercostal nerve injury is related to postoperative flank "bulge" and to determine whether the extent of the retroperitoneal incision is related to the incidence of flank bulge following abdominal aortic aneurysm repair.

DESIGN

Bilateral dissection of the 11th intercostal nerve on seven cadavers; neurophysiological evaluation of five patients, three with a flank bulge and two without; and retrospective analysis of the extent of retroperitoneal incision and incidence of postoperative flank bulge in 63 consecutive patients.

SETTING

Urban academic medical center.

PATIENTS

Sixty-three consecutive patients who underwent retroperitoneal repair of an abdominal aortic aneurysm and neurophysiological evaluation of five volunteer patients.

INTERVENTIONS

Retroperitoneal repair of abdominal aortic aneurysms.

MAIN OUTCOME MEASURE

Reduction of injury to the 11th intercostal nerve by avoiding extension of the retroperitoneal incision into the intercostal space.

RESULTS

Of 14 dissections of 11th intercostal nerves, there were bifurcations of the main trunk within the intercostal space in four, at the tip of the 11th rib in seven, and at least 2 cm distal to the tip of the rib in three. Neurophysiological evaluation revealed iterative discharges, polyphasia, fibrillation potentials, and altered recruitment patterns compatible with intercostal nerve injury in patients with a bulge but not in the opposite abdominal wall musculature or in patients without a bulge. Seven (11.11%) of 63 patients had a bulge. Thirty-one of 63 patients had incisions into the 11th intercostal space in which a bulge developed in six (19.35%). Thirty-two patients had incisions that avoided extension into the intercostal space; a bulge developed in one (0.03%) (P = .53).

CONCLUSIONS

Postoperative bulge is related to intercostal nerve injury with subsequent paralysis of abdominal wall musculature. Intercostal nerve injury can be reduced by avoiding extension of the incision into the 11th intercostal space.

Can air plethysmography accurately identify upper extremity deep venous thrombosis?

PURPOSE

Air plethysmography (APG) is an established, noninvasive means of evaluating lower extremity venous outflow.

METHODS

To determine whether APG could identify deep venous thrombosis (DVT) of the upper extremity, we measured the percentage of venous outflow in the first second (maximum venous outflow [MVO]) of four groups of arms: (1) normal volunteers (no previous central vein catheters), (2) the affected, (3) the unaffected arms of the patients with DVT (proven by venography or duplex scanning), and (4) hospital patients (no previous central vein catheters).

RESULTS

The results of an analysis of variance were as follows: the mean MVO (%) of the affected arms of patients with DVT, 29.4 +/- 2.6, was significantly less than their unaffected arms, 55.3 +/- 3.9, hospital controls, 64.3 +/- 2.2, and normal volunteers, 64.2 +/- 0.9 (p < 0.05). In addition, the unaffected arms differed significantly from all groups (p < 0.05). An MVO of 45% was 2 SD below the mean MVO of the normal volunteer group. Two unaffected arms of the patients with DVT were below 45%, whereas only one affected arm of the patients with DVT was above 45% (45.6%). Therefore a comparison of the distribution of the MVO values revealed virtually no overlap of the affected arms of the patients with DVT with the other three groups.

CONCLUSIONS

We conclude that APG clearly discriminated arms with documented DVT from controls and is a highly accurate means of identifying upper extremity DVT.

Changes in lower esophageal sphincter pressure (LES) after Stamm gastrostomy

Previous clinical and experimental reports have implicated placement of a Stamm gastrostomy (SG) as a cause of gastroesophageal reflux (GER) in children. This study evaluates this problem by measuring alterations in the lower esophageal sphincter pressure (LES) after SG with and without maintenance of the esophagogastric angle of Hiss. In 20 cats (2.8-3.2 kg) general anesthesia was induced using 20 mg/kg ketamine im. Esophageal manometrics were measured using a continuous perfusion catheter and recording system, evaluating three measurements for each animal. Eight cats (Group I) underwent SG placement in the anterior stomach wall two-thirds of the way down from the fundus. This was tacked to the anterior abdominal wall 3 cm lateral to the midline at the appropriate level. Six cats (Group II) had standard SG tube placement and in addition, two interrupted sutures were placed between the fundus and the esophagus maintaining the gastroesophageal angle of Hiss. Six cats (Group III) had sham laparotomy. After awakening, the animals were fed cat chow and water ad libitum. At 7 and 14 days, the animals were reanesthetized with ketamine and manometrics were repeated. Preoperative LES pressure measured 11.3 +/- 4.7 Torr. LES pressure in Group I decreased to 6.61 +/- 1.6 Torr at 7 days (P less than 0.01) and 4.8 +/- 1.6 Torr at 14 days postoperatively (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction of lower esophageal sphincter pressure with Stamm gastrostomy

Although recent clinical studies suggest an association between Stamm gastrostomy and gastroesophageal reflux (GER), no significant experimental data is available. This study evaluates alterations in lower esophageal sphincter (LES) pressure after Stamm gastrostomy in cats. Eight male cats (average weight 3 to 4 kg) were induced under general anesthesia using 20/mg/kg ketamine intramuscularly (IM). Esophageal manometrics were determined for each animal using a continuous perfusion catheter and recording system. Three measurements were taken for each animal. Stamm gastrostomy was then placed in the anterior wall of the stomach two thirds of the way down from the fundus. This was tacked to the anterior abdominal wall 3.0 cm lateral to the midline at the appropriate longitudinal level. Esophageal manometry was repeated after abdominal closure. The animals were awakened and returned to their cages for ad libidum feedings. The animals were reanesthetized with ketamine and manometrics repeated at 7 and 14 days. Each animal served as its own control. Five animals underwent barium esophagram 14 days postoperatively to evaluate for GER. Preoperative mean LES pressure measured 11.4 +/- 3.5 torr. This decreased to 7.8 +/- 2.8 torr immediately after Stamm gastrostomy (P less than .025). When evaluated at 1 and 2 weeks after gastrostomy, further decrease in LES pressures to 6.6 +/- 1.6 torr and 4.8 +/- 1.6 was observed (P less than .02 v preoperative). Three of five cats undergoing barium swallow demonstrated significant reflux radiographically. Stamm gastrostomy caused significant reduction of the LES pressure in all cats studied. This resulted in clinical GER as documented by barium swallow in three of five cats.(ABSTRACT TRUNCATED AT 250 WORDS)