Michael S. Higgins

The catecholamine, cortisol, and hemodynamic responses to mild perioperative hypothermia. A randomized clinical trial.

BackgroundUnintended hypothermia occurs frequently during surgery and may have adverse effects on the cardiovascular system. Although the mechanisms responsible for the cardiovascular manifestations of hypothermia are unclear, it is possible that they are sympathetically mediated. In this prospectiv

Multivariate determinants of early postoperative oxygen consumption in elderly patients. Effects of shivering, body temperature, and gender.

Background Previous investigators have proposed that postoperative shivering may be poorly tolerated by patients with cardiopulmonary disease because of the associated significant increase in total-body oxygen consumption. However, the often-quoted 300-400% increase in oxygen consumption with shivering was derived from relatively few studies performed in a small number of younger persons specifically selected on the basis of clinically recognizable shivering. We hypothesized that the average elderly postoperative patient has a shivering response that is associated with a relatively small increase in total-body oxygen consumption.

Comparison of two different temperature maintenance strategies during open abdominal surgery: upper body forced-air warming versus whole body water garment.

BackgroundA new system has been developed that circulates warm water through a whole body garment worn by the patient during surgery. In this study the authors compared two different strategies for the maintenance of intraoperative normothermia. One strategy used a new water garment warming system that permitted active warming of both the upper and lower extremities and the back. The other strategy used a single (upper body) forced-air warming system. MethodsIn this prospective, randomized study, 53 adult patients were enrolled in one of two intraoperative temperature management groups during open abdominal surgery with general anesthesia. The water-garment group (n = 25) received warming with a body temperature (rectal) set point of 36.8°C. The forced-air–warmer group (n = 28) received routine warming therapy using upper body forced-air warming system (set on high). The ambient temperature in the operating room was maintained constant at approximately 20°C. Rectal, distal esophageal, tympanic, forearm, and fingertip temperatures were recorded perioperatively and during 2 h after surgery. Extubated patients in both groups were assessed postoperatively for shivering, use of additional warming devices, and subjective thermal comfort. ResultsThe mean rectal and esophageal temperatures at incision, 1 h after incision, at skin closure, and immediately postoperatively were significantly higher (0.4–0.6°C) in the group that received water-garment warming when compared with the group that received upper body forced-air warming. The calculated 95% confidence intervals for the above differences in core temperatures were 0.7–0.1, 0.8–0.2, 0.8–0.2, and 0.9–0.1, retrospectively. In addition, 14 and 7% of patients in the control upper body forced-air group remained hypothermic (< 35.5°C) 1 and 2 h after surgery, respectively. No core temperature less than 35.5°C was observed perioperatively in any of the patients from the water-garment group. A similar frequency of the thermal stress events (shivering, use of additional warming devices, subjective thermal discomfort) was observed after extubation in both groups during the 2 h after surgery. ConclusionsThe investigated water warming system, by virtue of its ability to deliver heat to a greater percentage of the body, results in better maintenance of intraoperative normothermia that does forced-air warming applied only to the upper extremities, as is common practice.

Recovery from outpatient laparoscopic tubal ligation is not improved by preoperative administration of ketorolac or ibuprofen.

The analgesic efficacy of a single dose of ketorolac or ibuprofen given preoperatively was assessed in healthy outpatients undergoing general anesthesia for laparoscopic tubal ligation. Fifty patients were randomized to receive either ketorolac 60 mg intravenously (i.v.), ibuprofen 800 mg orally, or placebo in a double-blind manner. Anesthesia was induced with fentanyl 2 micrograms/kg, thiopental 5 mg/kg, and either vecuronium 0.1 mg/kg or succinylcholine 1.5 mg/kg i.v. and was maintained with nitrous oxide 67% in oxygen and isoflurane. Patients were assessed at 15-min intervals in the postanesthesia care unit (PACU) and treated for pain with i.v. morphine by protocol. Patients were evaluated for pain, analgesic requirements, side effects, and recovery times. After discharge, patients completed questionnaires to assess pain, analgesic use, and side effects 6 and 24 h postoperatively. Parenteral morphine was required in 80% of patients in the control group, and 73% of patients in both treatment groups, and the difference was not statistically significant. The dose of parenteral morphine required in the PACU was not different between the control (7 +/- 1.2 mg), ibuprofen (5.7 +/- 1.4 mg), and ketorolac (6.1 +/- 1.4 mg) groups. There was no difference between groups in terms of pain visual analog scale (VAS) scores, fatigue VAS scores, recovery times, or the incidence of postoperative nausea and vomiting. The preoperative administration of either parenteral ketorolac or oral ibuprofen did not decrease postoperative pain or side effects when compared to placebo in this outpatient population.

Comparison of awake endotracheal intubation in patients with cervical spine disease: the lighted intubating stylet versus the fiberoptic bronchoscope.

A wake endotracheal intubation followed by brief neurological examination before the induction of general anesthesia is an accepted practice for patients with cervical spine disease with symptoms of myelopathy and for patients at risk of spinal cord compression during standard endotracheal intubation (1). Awake intubation is performed with the fiberoptic bronchoscope (FOB) either by the nasal or oral route, the nasal route being relatively more common. The success rate of FOB intubation ranges from 72% to 98% (2-5). The lighted intubating stylet (LIS) has been used for indirect endotracheal intubation with success rates between 88% and 100% (6-9). Studies have demonstrated the efficiency of the LIS for managing the difficult airway in children (10) and in patients with maxillofacial injury (11). Use of the LIS is part of the ASA’s difficult airway algorithm (12). Because the LIS allows endotracheal intubation with minimal movement of the cervical spine, it is ideally suited for patients with myelopathy. Fox et al. (13) compared the LIS with blind nasotracheal intubation in awake patients with cervical spine disease and found the LIS to be superior, with greater speed, fewer required attempts, and reduced incidence of complications. Because awake nasotracheal intubation with the FOB is a common method of endotracheal intubation in patients with myelopathy, it is important to compare this technique with orotracheal intubation using the LIS.

Capnography during transtracheal needle cricothyrotomy

T he percutaneous placement of a catheter through the cricothyroid membrane followed by transtracheal jet ventilation can be used to maintain oxygenation in the “cannot intubate/cannot ventilate” scenario (1). Despite the relative safety of the technique, jet ventilation through a catheter that is not in the trachea can have disastrous consequences. This can lead directly to patient mortality or distort anatomic planes, so that surgical access to the airway becomes impossible. Different methods have been suggested to identify needle placement, including the aspiration of air or the observation of bubbles as air is aspirated through saline (2). Capnography remains a standard of care in the operating room and is regularly used to verify the intratracheal placement of an endotracheal tube. Despite this practice, which is used routinely in the operating room, we are unaware of reports evaluating the identification of CO, as a means of identifying correct catheter or needle placement during needle cricothyrotomy.

Cardiovascular and Adrenergic Manifestations of Cold Stress

Ischemic cardiac morbidity is the most common cause of death in the United States in patients undergoing surgery as well as in the non-perioperative setting.(l). Coronary artery disease is ultimately the predisposing factor in patients who suffer cardiac death, but usually a triggering event disrupts the delicate balance between myocardial oxygen supply and demand and leads to ischemia and infarction. Some of the factors that have been shown to induce myocardial ischemia include tachycardia, hypertension, hypotension, thrombosis, and cold stress. Bainton et al. (2) described a two-fold increase in the death rate from ischemic cardiac events in the winter relative to the summer. This study was a simple epidemiologic description of the relationship between time of year, ambient outdoor temperature, and mortality. These results have been confirmed by other investigators as well.(3) Neither study, however, has determined, or even proposed a mechanism to explain the higher death rate.

The Catecholamine, Cortisol, and Hemodynamic Responses to Mild Perioperative Hypothermia: A Randomized Clinical Trial

Background Unintended hypothermia occurs frequently during surgery and may have adverse effects on the cardiovascular system. Although the mechanisms responsible for the cardiovascular manifestations of hypothermia are unclear, it is possible that they are sympathetically mediated. In this prospective study, relationships between body temperature, the neuroendocrine response, and hemodynamic changes in the perioperative period were examined. Methods Seventy‐four elderly patients, undergoing abdominal, thoracic, or lower extremity vascular surgical procedures, were randomly assigned to either “routine care” (n = 37) or “forced‐air warming” (n = 37) groups. Throughout the intraoperative and early postoperative periods, the routine care group received standard thermal care, and the forced‐air warming group received forced‐air skin‐surface warming. Core temperature, forearm minus fingertip skin‐surface temperature gradient, and plasma concentrations of epinephrine, norepinephrine, and cortisol were measured throughout the perioperative period, and the two groups were compared. In addition, heart rate and arterial blood pressure were compared between groups. Results The routine care and forced‐air warming groups did not differ with regard to age, sex, type of surgical procedures, anesthetic techniques, or postoperative analgesia. Mean core temperature was lower in the routine care group on admission to the postanesthetic care unit (routine care, 35.3 plus/minus 0.1 degree Celsius; forced‐air warming, 36.7 plus/minus 0.1 degree Celsius; P = 0.0001) and remained lower during the early postoperative period. Forearm minus fingertip skin‐surface temperature gradient (an index of peripheral vasoconstriction) was greater in the routine care group in the early postoperative period. The mean norepinephrine concentration (pcg/ml) was greater in the routine care group immediately after surgery (480 plus/minus 70 vs. 330 plus/minus 30, P = 0.02) and at 60 min (530 plus/minus 50 vs. 340 plus/minus 30, P = 0.002) and 180 min (500 plus/minus 80 vs. 320 plus/minus 30, P = 0.004) postoperatively. Mean epinephrine concentrations were not significantly different between groups. Mean cortisol concentrations were increased in both groups during the early postoperative period (P < 0.01), but the differences between groups were not significant. Systolic, mean, and diastolic arterial blood pressures were significantly higher in the routine care group. Conclusions Compared with patients in the forced‐air warming group, patients receiving routine thermal care had lower core temperatures, a greater degree of peripheral vasoconstriction, higher norepinephrine concentrations, and higher arterial blood pressures in the early postoperative period. These findings suggest a possible mechanism for hypothermia‐related cardiovascular morbidity in the perioperative period.