Effect of type 2 diabetes, surgical incision, and volatile anesthesia on hemodynamics in the rat

Abstract

Diabetic patients have increased cardiac complications during surgery, possibly due to impaired autonomic regulation. Anesthesia lowers blood pressure and heart rate (HR), whereas surgical intervention has opposing effects. The interaction of anesthesia and surgical intervention on hemodynamics in diabetes is unknown, despite being a potential perioperative risk factor. We aimed to determine the effect of diabetes on the integrative interaction between hemodynamics, anesthesia, and surgical incision. Zucker type 2 diabetic rats (DM) and their nondiabetic littermates (ND) were implanted with an intravenous port for drug delivery, and a radiotelemeter to measure mean arterial blood pressure (MAP) and derive HR (total n = 50). Hemodynamic pharmacological responses were assessed under conscious, isoflurane anesthesia (~2–2.5%), and anesthesia–surgical conditions; the latter performed as a laparotomy. MAP was not different between groups under conscious conditions (ND 120 ± 6 vs. DM 131 ± 4 mmHg, P > 0.05). Anesthesia reduced MAP, but not differently in DM (ND −30 ± 6 vs. DM −38 ± 4 ΔmmHg, P > 0.05). Despite adequate anesthesia, surgical incision increased MAP, which tended to be less in DM (ND +21 ± 4 vs. DM +13 ± 2 ΔmmHg, P = 0.052). Anesthesia disrupted central baroreflex HR responses to sympathetic activation (sodium nitroprusside 10 μg·kg−1, ND conscious 83 ± 13 vs. anesthetized 16 ± 5 Δbpm; P < 0.05) or to sympathetic withdrawal (phenylephrine 10 μg·kg−1, ND conscious −168 ± 37 vs. anesthetized −20 ± 6 Δbpm; P < 0.05) with no additional changes observed after surgical incision or during diabetes. During perioperative conditions, type 2 diabetes did not impact on short‐term hemodynamic regulation. Anesthesia had the largest hemodynamic impact, whereas surgical effects were limited to modulation of baseline blood pressure.

Carvedilol and metoprolol are both able to preserve myocardial function in type 2 diabetes

“…DM rats displayed small but significant reductions in ejection fraction (Figure 3b) and fractional shortening (Figure 3h) compared to ND, suggestive of impaired contractility although values remained in the normal range. Heart rate was reduced in DM (Figure 3c), in line with our previous studies (Bussey & Lamberts, 2017). However, stroke volume and cardiac output were unchanged (Figure 3d,e).…”

“…Rats with diabetes ingested significantly more food per day than their nondiabetic counterparts. This was accounted for within the β‐blocker dosing, such that ND and DM rats were housed separately and prepared chow with different drug concentrations, based on estimated food intake from our previous studies (Bussey & Lamberts, 2017). Actual β‐blocker intake was estimated from the measured food intake for the current study.…”

“…Due to carvedilol's limited solubility, the drugs were delivered orally by crushed into the diet. Concentrations were estimated based on average daily food intake data from previous studies (Bussey & Lamberts, 2017), requiring separate diets for each group, and food intake was monitored to determine delivery.…”