Published papers

This study was undertaken to describe the metabolic O2 reserve of the coronary circulation in an awake sheep model of hyperdynamic sepsis. Forty- eight hours after sheep were randomized to either a SHAM group (n = 8) or a cecal ligation and perforation (CLP) group (n = 8), we measured hemodynamics, organ blood flows, and systemic and myocardial O2 metabolism variables at baseline and through four stages of progressive hypoxia. A significant elevation in arterial lactate levels occurred at a higher O2 delivery in the CLP group (527 ± 55 ml/min/m2) than in the SHAM group (357 ± 29 ml/min/m2, p < 0.05). The heart's metabolic O2 reserve (difference in circulatory determinants of O2 availability between baseline and where O2 uptake could not be sustained) was exhausted at an O2 content of 56.9 ± 4.2 ml O2/L in SHAM sheep and 79.6 ± 7.2 ml O2/L (p < 0.05) in CLP sheep. An increase in coronary blood flow was three times greater in SHAM than in CLP animals. Myocardial O2 extraction increased with hypoxia in SHAM sheep (0.78 ± 0.03 to 0.88 ± 0.02, p < 0.05), but not in CLP sheep (0.79 ± 0.02 to 0.80 ± 0.04). We conclude that the metabolic O2 reserve of the coronary circulation is depressed in this model of hyperdynamic sepsis as the ability to increase both coronary blood flows and myocardial O2 extraction was significantly limited.

Purpose: There are few clinical data examining whether sensitization of peripheral nerves contributes to postoperative pain when the entry of noxious impulses to the central nervous system is blocked. We hypothesized that wound infiltration with lidocaine would provide better postoperative analgesia than with normal saline following haemorrhoidectomy with spinal blockade. Methods: In a randomized, placebo-controlled, blinded study, 168 adults undergoing haemorrhoidectomy were allocated to two groups. In Group L (n = 88) local infiltration was provided with lidocaine 1% and in Group S (n = 80) with normal saline. Following spinal anaesthesia with lidocaine 3%, the surgeon infiltrated 15 ml of either infiltration solution to the surgical area. Postoperative analgesia was obtained by continuous epidural administration of 90 mg eptazocine in normal saline for 48 hr. Supplemental analgesics were given on request. Postoperative pain control was assessed at rest and during coughing with a 10 cm VAS on the 1st, 2nd, and 3rd postoperative days (POD). Results: The VAS scores at rest in Group L were lower than those in Group S throughout the postoperative period. During coughing, VAS scores in Group S were increased on the 3rd postoperative day, while those in Group L remained constant (4.42 ± 0.27 vs 3.14 ± 0.28, P < 0.05). Fewer patients in Group L than in Group S required supplemental analgesics. Conclusion: Preoperative lidocaine infiltration to the surgical area provided prolonged postoperative analgesia in patients receiving haemorrhoidectomy with spinal anaesthesia. © 1996 Canadian Anesthesiologists.

Since repeated noxious stimuli may sensitize neuropathic pain receptors of the spinal cord, we tested the hypothesis that the appropriate blockade of surgical stimuli with epidural anesthesia during upper abdominal surgery would be beneficial for postoperative analgesia. Thirty-six adult patients undergoing either elective gastrectomy or open cholecystectomy were randomly allocated to receive either inhalational general anesthesia alone (group G) or epidural anesthesia along with light general anesthesia (group E) throughout the surgery. Postoperative pain management consisted of patient-controlled analgesia (PCA) with bupivacaine accompanied by the continuous infusion of buprenorphine. To assess postoperative pain, a visual analogue scale (VAS) was employed at 2, 24, and 48 h postoperatively. While there was no significant difference in the bupivacaine dose, more patients undergoing gastrectomy in group G required supplemental analgesics than those in group E, and the VAS scores in group E demonstrated significantly better postoperative analgesia compared to group G after both types of surgery. Thus, an appropriate epidural blockade during upper abdominal surgery likely provides better postoperative pain relief. © 1996 JSA.

To examine the adverse effects of peritoneal carbon dioxide (CO2) insufflation during laparoscopic cholecystectomy, both hemodynamic and respiratory alterations were continously monitored in 17 adult patients using noninvasive Doppler ultrasonography and a continuous spirometric monitoring device. During the surgery, which was performed under inhalational general anesthesia, intraabdominal pressure was maintained automatically at 10mmHg by a CO2 insufflator, and a constant minute ventilation, initially set to 30-33 mmHg of end-tidal CO2 (ETCO2), was maintained. Despite considerable depth of anesthesia, peritoneal CO2 insufflation induced a significant and immediate increase of mean blood pressure (+42%) and systemic vascular resistance (+62%), accompanied by a slight depression of cardiac index (-12%, nonsignificant), while the ETCO2 gradually increased and maximized around 30min following the initial CO2 insufflation. The stress of 10mmHg pneumoperitoneum was a major cause of hemodynamic changes during laparoscopic cholecystectomy. Some clinical strategies such as deliberate intraabdominal insufflation at the initial phase might be required to minimize these hemodynamic changes. © 1996 JSA.

This study was designed to determine whether sepsis modifies the ability to preserve vital organ O2 delivery (Q̇O2) across a clinically relevant range of hematocrits. Ninety rats were randomly allocated to cecal ligation and perforation (CLP) or a sham (Sham) procedure. With the use of rat plasma, rat whole blood, or packed rat red blood cells, respectively, randomization into three different hematocrit subgroups followed: low (21-28%), middle (33- 40%), and high (4552%). Organ blood flow values (Q̇) were measured by the radioactive microsphere technique, and organ Q̇O2 values were calculated. Twenty-four hours after laparotomy, the hematocrit grouping had not modified the interorgan distribution of Q̇ or Q̇O2 in either the CLP or Sham rats. To characterize overall metabolic O2 reserve, rats were then exposed to hypoxia (inspired O2 fraction, 0.08) for 20 min. Whereas cardiac output increased significantly during hypoxia in all experimental groups, myocardial Q̇O2 failed to increase in the low hematocrit Sham subgroup and fell significantly in both the middle- and low-hematocrit CLP subgroups. There was also a lesser redistribution of Q̇O2 away from the small intestine in the low-hematocrit compared with the high-hematocrit CLP subgroup. We conclude that myocardial Q̇O2 is more effectively maintained in septic hypoxic rats if the hematocrit is maintained at levels >45%.

Background: While permissive hypercapnia is commonly practised in critical care, it remains unclear if the comparable manoeuvres are clinically acceptable during anaesthesia. This retrospective study aimed at describing the anaesthetic implications of hypercapnia associated with deliberate hypoventilation during thoracic surgery in patients with severe emphysema. Methods: Thirteen patients with emphysema who required thoracic surgery under similar anaesthesia were reviewed: 3 patients were managed to maintain normocapnia (normocapnia group) whereas 10 patients developed hypercapnia (PaCO2 >70 mmHg) as a result of restricting peak airway pressures (hypercapnia group). Results: In the normocapnia group (PaCO2: 45±1 mmHg, mean±SD), no event which required therapeutic intervention during the surgery was seen, whereas 2 of 3 patients showed postoperative air leakage which persisted over 5 days. In the hypercapnia group, the maximum PaCO2 during anaesthesia ranged between 70 mmHg and 135 mmHg (98±21 mmHg). During anaesthesia, all 10 patients required inotropic support to pre- vent hypotension, 4 patients required tracheal gas insufflation of oxygen to the operated lung to avoid hypoxaemia and 3 patients required lidocaine to treat ventricular arrhythmia. However, the trachea was extubated in the operation theatre in 9 of 10 patients and no organ dysfunction was observed postoperatively. Four patients showed postoperative air leak on the first postoperative day, one of which persisted over 5 days. Conclusion: Although there are some limitations, this preliminary study indicates that hypercapnia around 100 mmHg during anaesthesia for thoracic surgery may not be associated with serious consequences.