Rewarming Pattern Research Articles

Decreased oesophageal blood flow in patients with Raynaud's phenomenon.

Cold-induced vasospasm seen in systemic sclerosis (SS) and Raynaud's phenomenon (RP) has previously been thought to be limited to peripheral skin sites. However, the oesophageal problems seen in SS cannot be sufficiently explained by connective tissue damage/abnormal motility alone. We wondered if temperature dependent ischaemia could occur in the oesophageal microcirculation. We have measured oesophageal temperature variation following oesophageal cold challenge: 50 ml of water at 7 degrees C and 17 degrees C, with 37 degrees C used as control, were introduced into the mid-oesophagus at a rate of 2 ml/s. Temperature was recorded using a thermocouple probe 5 cm above the gastro-oesophageal junction. The test was performed on 14 SS patients, eight patients with Raynaud's disease and 21 controls. The control's rewarming pattern followed a simple exponential curve. This did not vary with temperature or after repeated challenge. In the SS patients the time constant was significantly longer after cold challenge.

Effect of phentolamine in controlling temperature and acidosis associated with cardiopulmonary bypass.

This study assessed the effects of phentolamine on rewarming patterns and metabolic acidosis in 37 patients subjected to hypothermia during cardiopulmonary bypass for the performance of aortocoronary bypass grafting. An additional 16 patients undergoing the same surgery received no phentolamine and served as a control group. In all patients, sodium bicarbonate (44.6 mEq) was administered only when the negative base excess was 3.0 mEq/L or greater. Sixty-eight percent of the patients receiving phentolamine and 56% of the control patients exhibited a uniform rewarming pattern in which the rectal, hand, and foot temperatures increased in parallel. In 32% of the patients receiving phentolamine and in 44% of the control patients, rectal and hand temperatures increased more than foot temperature during rewarming. Analysis of base excess values in the subgroups of patients with similar rewarming patterns indicated that base deficits were significantly decreased in patients receiving phentolamine. Phentolamine administration was also associated with significantly lower blood lactate levels and sodium bicarbonate requirements, as well as improvements in overall appearance and mental status. These data suggest that the routine use of phentolamine in patients undergoing cardiopulmonary bypass may be associated with more uniform body cooling and rewarming and improved tissue perfusion.

A plastic head cover to reduce surgical heat loss

Objective: To compare the effects of two external rewarming methods on body core temperature and the rate of rewarming between two age groups (less than 65 years, 65 years or more) of adult, midly hypothermic patients who have undergone cardiac surgery, during the immediate postoperative period.Design: Stratified, randomized clinical trial.Setting: Five-bed cardiac surgical intensive care unit in a large teaching-research institution.Subjects: Thirty-two white patients who had undergone cardiac surgery and who had midly hypothermic body core temperatures (33° to 35°C) immediately after the surgery.Outcome Measures: Body core temperature was measured with a pulmonary artery catheter thermistor at the time of external rewarming method application and at 60, 90, and 150 minutes afterward. Rate of rewarming was measured as body core temperature change in degrees Celsius per hour (at 36.6°C, minus body core temperature when external rewarming method was applied, divided by total rewarming time). Temperatures were recorded six times at intervals of 15 minutes; then every 30 minutes until a value of 36.6°C was obtained, at which time the blanket was removed; then hourly for 8 hours.Intervention: Either a fluid-filled circulating blanket (active-conductive external rewarming) or a reflective blanket (passive-reflective external rewarming) was applied immediately after core temperature was measured on admission to the cardiac surgical intensive care unit after surgery.Results: External rewarming methods affected body core temperature differently at different times, and there were significant differences in body core temperature across the time periods (p<0.05). Both active and passive external rewarming methods showed a sigmoidal rewarming pattern without a downward temperature drift. The fluid-filled circulating blanket produced a quicker and steeper body core temperature change in the early rewarming phase; the reflective blanket resulted in a more gradual temperature rise. Age did not significantly affect body core temperature, nor did age or external rewarming method significantly influence the rate of rewarming, although total rewarming time was longer for those of more advanced age. Seven subjects with passive rewarming method experienced body core temperature overshoot during the 8-hour period after blanket removal.Conclusions: In this study, conduction and reflection of radiant heat were equally effective in producing an acceptable rate of rewarming but contributed to different internal patterns in core rewarming. The average total rewarming time with the active external rewarming method was 1 hour shorter than with the passive external rewarming method.

Myocardial Performance Early After Aorto‐Coronary Bypass Surgery and the Influence of Nitroprusside Infusion

The central and peripheral circulation were studied in 12 patients after aortocoronary bypass surgery. During the initial 5 h after termination of cardiopulmonary bypass, the oesophageal temperature rose from 36.5 degrees C to 39.4 degrees C, concomitant with cutaneous vasoconstriction and an increase in systemic vascular resistance (SVR) and mean arterial blood pressure (MABP). The oxygen uptake index (Vo2I) increased by 57% during the rewarming period. The cardiac index (CI), which was constant at 2.8 l.min-1.m-2, was too low to satisfy this oxygen demand and the arterio-venous oxygen content difference (AVDo2) increased to 3.0 mmol . l-1 by the 3rd hour. After 5 h, SVR had decreased and cutaneous vasodilation began. Vo2I and AVDo2 decreased. The postoperative myocardial function was moderately impaired and deteriorated after the cutaneous vasodilation. Twelve patients were given an infusion of sodium nitroprusside during the postoperative period (0.25--2.5 micrograms . kg-1 . min-1). The rewarming pattern was not influenced by this infusion, but the initial increases in MABP and SVR were eliminated. The myocardial performance was better in the nitroprusside group. CI was significantly higher than in the control group (3.5 l.min-1.m-2) and AVDo2 remained normal.

Competition between cutaneous vasodilator and vasoconstrictor reflexes in man.

A two-part experiment was carried out on seven men to determine whether skin will respond to increased neurogenic vasoconstrictor activity during heating. The latter was induced by lower body negative pressure of -50 mm Hg applied for 5 of each 15 min in 12 studies with constant, neutral skin temperature (32.2-34.4 C) in a 40-min control period and with skin temperature held at 38 C for 40-70 min. We conclude that during heating, skin retains the ability to vasoconstrict but that this vasoconstriction cannot completely override heat-induced vasodilatation.

Central and peripheral rewarming patterns in postoperative cardiac patients.

Central and peripheral temperature patterns in rewarming cardiac surgery patients have been studied by thermistor and infrared scanning techniques. These studies were combined with comprehensive patient monitoring records in a series of five patients. Evidence that thermoregulation, cardiac output, and drug action strongly affect the rewarming patterns could be substantiated for this limited series. In general an anatomic sequence of rewarming occurs in which the toes rewarm before the entire foot. Patterns of rewarming at the fingers and hands were similar to those at the toes. There was interpatient variation in the detailed temporal-spatial re-warming pattern of the digits. Blood flow rates to the toe were computed in accordance with the temperature data and were substantiated by venous occlusion plethysmography.